WorldWideScience

Sample records for hydrogen kinetic investigation

  1. Proton NMR investigation of heme pocket mobility in hemoglobin via hydrogen isotope exchange kinetics

    International Nuclear Information System (INIS)

    Han, K.

    1985-01-01

    Dynamic mobility of heme cavity, the active site of Hb, was investigated by analyzing the hydrogen isotope exchange kinetics of the proximal histidyl ring NH of various kinds of Hbs with the aid of the high field Fourier Transform 1 H NMR spectroscopy. The exchange reaction occurs faster in oxy or R-state Hb than in deoxy or T-state Hb and there exists a good correlation between the oxygen affinity of Hb and the heme pocket mobility reflected in the hydrogen exchange rate. The effect of pH on the exchange is dramatically different for the two subunits of Hb A. Studying the exchange characteristics of mutant Hbs and chemically modified Hbs not only showed the existence of three well-defined localized paths for transmission of conformational changes between different heme pockets through a 1 b 2 subunit interface, but also indicated that the heme pocket mobility is regulated by the quaternary state of Hb as well as by the ligation state of Hb. Finally, the effect of the quaternary state on the heme pocket mobility is separated from that of the ligation by following the exchange reactions in Hbs where only their quaternary structure transition can be achieved without changing their ligation states by adjusting experimental conditions such as adding inositol hexaphosphate

  2. Investigation of the kinetics of the reactions of oxidation, nitration, and hydrogenation of uranium

    International Nuclear Information System (INIS)

    Adda, Y.

    1955-06-01

    Various physico-chemical methods have been used to investigate the kinetics of the oxidation hydridation and nitridation of uranium. The experimental results show that the kinetics of these reactions are influenced by many factors also the Pilling and Bedworth rule is valid only under very limited conditions. The disagreement between this rule and the experimental results could be explained by the existence of numerous mechanical faults in the compounds obtained by the dry corrosion of the metal. (author) [fr

  3. Liquefaction chemistry and kinetics: Hydrogen utilization studies

    Energy Technology Data Exchange (ETDEWEB)

    Rothenberger, K.S.; Warzinski, R.P.; Cugini, A.V. [Pittsburgh Energy Technology Center, PA (United States)] [and others

    1995-12-31

    The objectives of this project are to investigate the chemistry and kinetics that occur in the initial stages of coal liquefaction and to determine the effects of hydrogen pressure, catalyst activity, and solvent type on the quantity and quality of the products produced. The project comprises three tasks: (1) preconversion chemistry and kinetics, (2) hydrogen utilization studies, and (3) assessment of kinetic models for liquefaction. The hydrogen utilization studies work will be the main topic of this report. However, the other tasks are briefly described.

  4. Investigation of hydrogen micro-kinetics in metals with ion beam implantation and analysis

    International Nuclear Information System (INIS)

    Wang, T.S.; Peng, H.B.; Lv, H.Y.; Han, Y.C.; Grambole, D.; Herrmann, F.

    2007-01-01

    One of the most important subjects in the fusion material research is to study the hydrogen and helium concentration, diffusion and evolution in the structure material of fusion reactor, since the hydrogen and helium can be continuously produced by the large dose fast neutron irradiation on material. Various analysis Methods can be used, but the ion beam analysis method has some advantages for studying the hydrogen behaviors in nano- or micrometer resolution. In this work, the hydrogen motion and three-dimensional distribution after implantation into metal has been studied by resonance NRA, micro-ERDA and XRD etc Methods. The resolution of the H-depth-profile is in nanometer level and the lateral resolution can be reached to 2 micrometers. The evolution of hydrogen depth-profile in a titanium sample has been studied versus the change of normal stress in samples. Evident hydrogen diffusion has been observed, while a normal stress is changed in the range of 107-963 MPa. A new phase transformation during the hydrogenation is observed by the in-situ XRD analysis. The further study on the hydrogen behaviors in the structure materials of fusion reactor is in plan. (authors)

  5. An investigation on hydrogen storage kinetics of nanocrystalline and amorphous Mg2Ni1-xCox (x = 0-0.4) alloy prepared by melt spinning

    International Nuclear Information System (INIS)

    Zhang Yanghuan; Li Baowei; Ren Huipin; Ding Xiaoxia; Liu Xiaogang; Chen Lele

    2011-01-01

    Research highlights: → The investigation of the structures of the Mg 2 Ni 1-x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys indicates that a nanocrystalline and amorphous structure can be obtained in the experiment alloys by melt spinning technology. The substitution of Co for Ni facilitates the glass formation in the Mg 2 Ni-type alloy. And the amorphization degree of the alloys visibly increases with increasing Co content. → Both the melt spinning and Co substitution significantly improve the hydrogen storage kinetics of the alloys. The hydrogen absorption saturation ratio (R t a ) and hydrogen desorption ratio (R t d ) as well as the high rate discharge ability (HRD) increase with rising spinning rate and Co content. The hydrogen diffusion coefficient (D), the Tafel polarization curves and the electrochemical impedance spectra (EIS) measurements show that the electrochemical kinetics notably increases with rising spinning rate and Co content. → Furthermore, all the as-spun alloys, when the spinning rate reaches to 30 m/s, have nearly same hydrogen absorption kinetics, indicating that the hydrogen absorption kinetics of the as-spun alloy is predominately controlled by diffusion ability of hydrogen atoms. - Abstract: In order to improve the hydrogen storage kinetics of the Mg 2 Ni-type alloys, Ni in the alloy was partially substituted by element Co, and melt-spinning technology was used for the preparation of the Mg 2 Ni 1-x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys is tested by an automatic galvanostatic system. The hydrogen diffusion coefficients in the alloys are calculated by virtue of potential-step method. The electrochemical impedance spectrums (EIS) and the Tafel

  6. Hydrogen peroxide kinetics in water radiolysis

    Science.gov (United States)

    Iwamatsu, Kazuhiro; Sundin, Sara; LaVerne, Jay A.

    2018-04-01

    The kinetics of the formation and reaction of hydrogen peroxide in the long time γ- radiolysis of water is examined using a combination of experiment with model calculations. Escape yields of hydrogen peroxide on the microsecond time scale are easily measured with added radical scavengers even with substantial amounts of initial added hydrogen peroxide. The γ-radiolysis of aqueous hydrogen peroxide solutions without added radical scavengers reach a steady state limiting concentration of hydrogen peroxide with increasing dose, and that limit is directly proportional to the initial concentration of added hydrogen peroxide. The dose necessary to reach that limiting hydrogen peroxide concentration is also proportional to the initial concentration, but dose rate has a very small effect. The addition of molecular hydrogen to aqueous solutions of hydrogen peroxide leads to a decrease in the high dose limiting hydrogen peroxide concentration that is linear with the initial hydrogen concentration, but the amount of decrease is not stoichiometric. Proton irradiations of solutions with added hydrogen peroxide and hydrogen are more difficult to predict because of the decreased yields of radicals; however, with a substantial increase in dose rate there is a sufficient decrease in radical yields that hydrogen addition has little effect on hydrogen peroxide decay.

  7. Hydrogen electrode reaction: A complete kinetic description

    International Nuclear Information System (INIS)

    Quaino, P.M.; Gennero de Chialvo, M.R.; Chialvo, A.C.

    2007-01-01

    The kinetic description of the hydrogen electrode reaction (HER) in the whole range of overpotentials (-0.2 < η (V) < 0.40) is presented. The Volmer-Heyrovsky-Tafel mechanism was solved considering simultaneously the following items: (i) the diffusional contribution of the molecular hydrogen from and towards the electrode surface, (ii) the forward and backward reaction rates of each elementary step and (iii) a Frumkin type adsorption for the reaction intermediate. In order to verify the descriptive capability of the kinetic expressions derived, an experimental study of the HER was carried out on a rotating platinum disc electrode in acid solution. From the correlation of these results the elementary kinetic parameters were evaluated and several aspects related to the kinetic mechanism were discussed. Finally, the use of these kinetic expressions to interpret results obtained on microelectrodes is also analysed

  8. Hydrogen atom kinetics in capacitively coupled plasmas

    Science.gov (United States)

    Nunomura, Shota; Katayama, Hirotaka; Yoshida, Isao

    2017-05-01

    Hydrogen (H) atom kinetics has been investigated in capacitively coupled very high frequency (VHF) discharges at powers of 16-780 mW cm-2 and H2 gas pressures of 0.1-2 Torr. The H atom density has been measured using vacuum ultra violet absorption spectroscopy (VUVAS) with a micro-discharge hollow cathode lamp as a VUV light source. The measurements have been performed in two different electrode configurations of discharges: conventional parallel-plate diode and triode with an intermediate mesh electrode. We find that in the triode configuration, the H atom density is strongly reduced across the mesh electrode. The H atom density varies from ˜1012 cm-3 to ˜1010 cm-3 by crossing the mesh with 0.2 mm in thickness and 36% in aperture ratio. The fluid model simulations for VHF discharge plasmas have been performed to study the H atom generation, diffusion and recombination kinetics. The simulations suggest that H atoms are generated in the bulk plasma, by the electron impact dissociation (e + H2 \\to e + 2H) and the ion-molecule reaction (H2 + + H2 \\to {{{H}}}3+ + H). The diffusion of H atoms is strongly limited by a mesh electrode, and thus the mesh geometry influences the spatial distribution of the H atoms. The loss of H atoms is dominated by the surface recombination.

  9. Kinetics of Hydrogen Absorption and Desorption in Titanium

    Directory of Open Access Journals (Sweden)

    Suwarno Suwarno

    2017-10-01

    Full Text Available Titanium is reactive toward hydrogen forming metal hydride which has a potential application in      energy storage and conversion. Titanium hydride has been widely studied for hydrogen storage, thermal storage, and battery electrodes applications. A special interest is using titanium for hydrogen production in a hydrogen sorption-enhanced steam reforming of natural gas. In the present work, non-isothermal dehydrogenation kinetics of titanium hydride and kinetics of hydrogenation in gaseous flow at isothermal conditions were investigated. The hydrogen desorption was studied using temperature desorption spectroscopy (TDS while the hydrogen absorption and desorption in gaseous flow were studied by temperature programmed desorption (TPD. The present work showed that the path of dehydrogenation of the TiH2 is d®b®a hydride phase with possible overlapping steps occurred. The fast hydrogen desorption rate observed at the TDS main peak temperature were correlated with the fast transformation of the d-TiH1.41 to b-TiH0.59. In the gaseous flow, hydrogen absorption and desorption were related to the transformation of b-TiH0.59 Û d-TiH1.41 with 2 wt.% hydrogen reversible content. Copyright © 2017 BCREC Group. All rights reserved Received: 21st November 2016; Revised: 20th March 2017; Accepted: 9th April 2017; Available online: 27th October 2017; Published regularly: December 2017 How to Cite: Suwarno, S., Yartys, V.A. (2017. Kinetics of Hydrogen Absorption and Desorption in Titanium. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (3: 312-317  (doi:10.9767/bcrec.12.3.810.312-317

  10. MODELING STYRENE HYDROGENATION KINETICS USING PALLADIUM CATALYSTS

    Directory of Open Access Journals (Sweden)

    G. T. Justino

    Full Text Available Abstract The high octane number of pyrolysis gasoline (PYGAS explains its insertion in the gasoline pool. However, its use is troublesome due to the presence of gum-forming chemicals which, in turn, can be removed via hydrogenation. The use of Langmuir-Hinshelwood kinetic models was evaluated for hydrogenation of styrene, a typical gum monomer, using Pd/9%Nb2O5-Al2O3 as catalyst. Kinetic models accounting for hydrogen dissociative and non-dissociative adsorption were considered. The availability of one or two kinds of catalytic sites was analyzed. Experiments were carried out in a semi-batch reactor at constant temperature and pressure in the absence of transport limitations. The conditions used in each experiment varied between 16 - 56 bar and 60 - 100 ºC for pressure and temperature, respectively. The kinetic models were evaluated using MATLAB and EMSO software. Models using adsorption of hydrogen and organic molecules on the same type of site fitted the data best.

  11. Kinetics of hydrogen peroxide decomposition by catalase: hydroxylic solvent effects.

    Science.gov (United States)

    Raducan, Adina; Cantemir, Anca Ruxandra; Puiu, Mihaela; Oancea, Dumitru

    2012-11-01

    The effect of water-alcohol (methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol and propane-1,2,3-triol) binary mixtures on the kinetics of hydrogen peroxide decomposition in the presence of bovine liver catalase is investigated. In all solvents, the activity of catalase is smaller than in water. The results are discussed on the basis of a simple kinetic model. The kinetic constants for product formation through enzyme-substrate complex decomposition and for inactivation of catalase are estimated. The organic solvents are characterized by several physical properties: dielectric constant (D), hydrophobicity (log P), concentration of hydroxyl groups ([OH]), polarizability (α), Kamlet-Taft parameter (β) and Kosower parameter (Z). The relationships between the initial rate, kinetic constants and medium properties are analyzed by linear and multiple linear regression.

  12. Kinetics of gaseous uranium hexafluoride reaction with hydrogen chloride

    International Nuclear Information System (INIS)

    Ezubchenko, A.N.; Ilyukhin, A.I.; Merzlyakov, A.V.

    1993-01-01

    Kinetics of decrease of concentration of gaseous uranium hexafluoride in reaction with hydrogen chloride at temperatures close to room ones, was investigated by the method of IR spectroscopy. It was established that the process represented the first order reaction by both UF 6 and HCl. Activation energy of the reaction was determined: 7.6 ± 0.7 kcal/mol. Specific feature of reaction kinetics was noted: inversely proportional dependence of effective constant on UF 6 initial pressure. 5 refs., 3 figs

  13. Hydrogen kinetics in a-Si:H and a-SiC:H thin films investigated by real-time ERD

    Energy Technology Data Exchange (ETDEWEB)

    Halindintwali, S., E-mail: shalindintwali@uwc.ac.za [Physics Department, University of the Western Cape, Private Bag X17, Bellville 7535 (South Africa); Khoele, J. [Physics Department, University of the Western Cape, Private Bag X17, Bellville 7535 (South Africa); Nemroaui, O. [Department of Mechatronics, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535 (South Africa); Comrie, C.M. [Department of Physics, University of Cape Town, Rondebosch 7700 (South Africa); Materials Research Department, iThemba LABS, P.O. Box 722, Somerset West 7129 (South Africa); Theron, C.C. [Physics Department, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa)

    2015-04-15

    Hydrogen effusion from hydrogenated amorphous silicon (a-Si:H) and amorphous silicon carbide (a-Si{sub 1−x}C{sub x}:H) thin films during a temperature ramp between RT and 600 °C was studied by in situ real-time elastic recoil detection analysis. Point to point contour maps show the hydrogen depth profile and its evolution with the ramped temperature. This paper proposes a diffusion limited evolution model to study H kinetic properties from total retained H contents recorded in a single ramp. In a compact a-Si:H layer where H predominantly effuses at high temperatures between 500 and 600 °C, an activation energy value of ∼1.50 eV and a diffusion pre-factor of 0.41 × 10{sup −4} cm{sup 2}/s were obtained. Applied to an non-stoichiometric a-Si{sub 1−x}C{sub x}:H film in the same range of temperature, the model led to reduced values of activation energy and diffusion prefactor of ∼0.33 eV and 0.59 × 10{sup −11} cm{sup 2}/s, respectively.

  14. Transport kinetics of hydrogen permeable lanthanum tungstate

    Energy Technology Data Exchange (ETDEWEB)

    Falkenstein, Andreas

    2017-01-24

    The electrical conductivity relaxation technique is a widely used method to determine the oxygen transport parameters of mixed ionic-electronic conductors. In recent years, it has been modified to investigate the hydration behavior of proton conducting mixed conductors, giving access to up to four transport parameters in a single relaxation experiment, the diffusion coefficients and surface reaction rates of hydrogen and oxygen. In this work, the transport properties of the fluorite type protonic conductor lanthanum tungstate have been investigated by means of electrical conductivity relaxation. The experiments were performed in a temperature range from 650 C to 950 C, in a pO{sub 2} range from 3 mbar to 100 mbar and in a pH{sub 2}O range from 10 mbar to 100 mbar and in dry atmosphere. At high temperatures, the conductivity relaxation curve follows the expected two-fold non-monotonic behavior upon hydration. At low temperatures, however, the contribution of the fast hydrogen kinetic decreases and by a further decrease of the temperature, the relaxation shows two-fold monotonic behavior. The power factors - the contribution of each single fold relaxation curve to the resulting two-fold relaxation curve, which is a superposition - have been derived to explain the behavior mentioned above. The activation energy of the oxygen incorporation is rather low. Hence, oxidation experiments were performed in dry atmospheres in order to investigate if the origin of the oxygen species is relevant. The results revealed higher activation energies, which was expected, but also higher absolute values of the surface reaction rate and the diffusion coefficient. Oxidation experiments with increasing humidity revealed that the increased diffusivity cannot be attributed to the total concentrations of electron holes and proton interstitials. First experiments using spectroscopic relaxation, which is dependent on the concentration of hydroxy-anions only, were performed. Absorption bands

  15. Hydrogen peroxide decomposition kinetics in aquaculture water

    DEFF Research Database (Denmark)

    Arvin, Erik; Pedersen, Lars-Flemming

    2015-01-01

    during the HP decomposition. The model assumes that the enzyme decay is controlled by an inactivation stoichiometry related to the HP decomposition. In order to make the model easily applicable, it is furthermore assumed that the COD is a proxy of the active biomass concentration of the water and thereby......Hydrogen peroxide (HP) is used in aquaculture systems where preventive or curative water treatments occasionally are required. Use of chemical agents can be challenging in recirculating aquaculture systems (RAS) due to extended water retention time and because the agents must not damage the fish...... reared or the nitrifying bacteria in the biofilters at concentrations required to eliminating pathogens. This calls for quantitative insight into the fate of the disinfectant residuals during water treatment. This paper presents a kinetic model that describes the HP decomposition in aquaculture water...

  16. The kinetic study of oxidation of iodine by hydrogen peroxide

    International Nuclear Information System (INIS)

    Cantrel, L.; Chopin, J.

    1996-01-01

    Iodine chemistry is one of the most important subjects of research in the field of reactor safety because this element can form volatile species which represent a biological hazard for environment. As the iodine and the peroxide are both present in the sump of the containment in the event of a severe accident on a light water nuclear reactor, it can be important to improve the knowledge on the reaction of oxidation of iodine by hydrogen peroxide. The kinetics of iodine by hydrogen peroxide has been studied in acid solution using two different analytical methods. The first is a UV/Vis spectrophotometer which records the transmitted intensity at 460 nm as a function of time to follow the decrease of iodine concentration, the second is an amperometric method which permits to record the increase of iodine+1 with time thanks to the current of reduction of iodine+1 to molecular iodine. The iodine was generated by Dushman reaction and the series of investigations were made at 40 o C in a continuous stirring tank reactor. The influence of the initial concentrations of iodine, iodate, hydrogen peroxide, H + ions has been determined. The kinetics curves comprise two distinct chemical phases both for molecular iodine and for iodine+1. The relative importance of the two processes is connected to the initial concentrations of [I 2 ], [IO 3 - ], [H 2 O 2 ] and [H + ]. A rate law has been determined for the two steps for molecular iodine. (author) figs., tabs., 22 refs

  17. In situ NMR studies of hydrogen storage kinetics and molecular diffusion in clathrate hydrate at elevated hydrogen pressures

    Energy Technology Data Exchange (ETDEWEB)

    Okuchi, T. [Okayama Univ., Misasa, Tottori (Japan); Moudrakovski, I.L.; Ripmeester, J.A. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences

    2008-07-01

    The challenge of storing high-density hydrogen into compact host media was investigated. The conventional storage scheme where an aqueous solution is frozen with hydrogen gas is too slow for practical use in a hydrogen-based society. Therefore, the authors developed a faster method whereby hydrogen was stored into gas hydrates. The hydrogen gas was directly charged into hydrogen-free, crystalline hydrate powders with partly empty lattices. The storage kinetics and hydrogen diffusion into the hydrate was observed in situ by nuclear magnetic resonance (NMR) in a pressurized tube cell. At pressures up to 20 MPa, the storage was complete within 80 minutes, as observed by growth of stored-hydrogen peak into the hydrate. Hydrogen diffusion within the crystalline hydrate media is the rate-determining step of current storage scheme. Therefore, the authors measured the diffusion coefficient of hydrogen molecules using the pulsed field gradient NMR method. The results show that the stored hydrogen is very mobile at temperatures down to 250 K. As such, the powdered hydrate media should work well even in cold environments. Compared with more prevailing hydrogen storage media such as metal hydrides, clathrate hydrates have the advantage of being free from hydrogen embrittlement, more chemically durable, more environmentally sound, and economically affordable. It was concluded that the powdered clathrate hydrate is suitable as a hydrogen storage media. 22 refs., 4 figs.

  18. Kinetics of Dicyclopentadiene Hydrogenation Using PD/C Catalyst

    Czech Academy of Sciences Publication Activity Database

    Skála, D.; Hanika, Jiří

    2003-01-01

    Roč. 45, 3-4 (2003), s. 105-108 ISSN 1335-3055 Institutional research plan: CEZ:AV0Z4072921 Keywords : hydrogenation * dicyclopentadiene * kinetics Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  19. A kinetic study of the electrochemical hydrogenation of ethylene

    International Nuclear Information System (INIS)

    Sedighi, S.; Gardner, C.L.

    2010-01-01

    In this study, we have examined the kinetics of the electrochemical hydrogenation of ethylene in a PEM reactor. While in itself this reaction is of little industrial interest, this reaction can be looked upon as a model reaction for many of the important hydrogenation processes including the refining of heavy oils and the hydrogenation of vegetable oils. To study the electrochemical hydrogenation of ethylene, several experimental techniques have been used including polarization measurements, measurement of the composition of the exit gases and potential step, transient measurements. The results show that the hydrogenation reaction proceeds rapidly and essentially to completion. By fitting the experimental transient data to the results from a zero-dimensional mathematical model of the process, a set of kinetic parameters for the reactions has been obtained that give generally good agreement with the experimental results. It seems probable that similar experimental techniques could be used to study the electrochemical hydrogenation of other unsaturated organic molecules of more industrial significance.

  20. Kinetic of martensitic transformations induced by hydrogen in the austenite

    International Nuclear Information System (INIS)

    Oliveira, Sergio P. de; Saavedra, A.; Miranda, P.E.V. de

    1986-01-01

    The X-ray diffractometry technique was used, with an automatic data acquisition system to determine the kinetics of hydrogen induced martensitic phase transformations in an AISI 304 austenitic stainless steel type, used in nuclear power plants. Hydrogenation was performed cathodically in a 1N sulfuric acid solution, containing 100 mg/l of arsenic trioxide, at 50 0 C, during 2 hours and with a current density of 200 A/m 2 . It was found that the microstructure of the steel plays a role on the generation of hydrogen induced martensitic phases and surface micro cracks. Both kinetics were slower on a pre-cold rolled steel. (Author) [pt

  1. Investigation of the explosion hazards of hydrogen sulphide

    International Nuclear Information System (INIS)

    Saber, A.J.; Sulmistras, A.; Moen, I.O.; Thibault, P.A.

    1986-03-01

    The results of Phase I of an investigation directed towards quantifying the explosion hazards of hydrogen sulphide in air are described. The first phase is focussed on detonation in free hydrogen sulphide/air clouds. Detonation properties, including velocity and pressure, have been calculated and compared with experimental results. The observed detonation structure together with critical tube tests tests are used to assess the detonability of hydrogen sulphide/air mixtures relative to hydrogen and common hydrocarbon gases. Detailed chemical kinetic modelling of hydrogen sulphide combustion in air has been performed to correlate the detonation cell size data and to determine the influence of water vapour on the detonability of hydrogen sulphide in air. Calculations of the blast wave properties for detonation of a hydrogen sulphide/air cloud provide the data required to assess the blast effects of such explosions

  2. Hydrogen vacancies facilitate hydrogen transport kinetics in sodium hydride nanocrystallites

    NARCIS (Netherlands)

    Singh, S.; Eijt, S.W.H.

    2008-01-01

    We report ab initio calculations based on density-functional theory, of the vacancy-mediated hydrogen migration energy in bulk NaH and near the NaH(001) surface. The estimated rate of the vacancy mediated hydrogen transport, obtained within a hopping diffusion model, is consistent with the reaction

  3. The kinetic study of oxidation of iodine by hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Cantrel, L [Institut de Protection et de Surete Nucleaire, IPNS, CEN Cadarache, Saint Paul lez Durance (France); Chopin, J [Laboratoire d` Electrochimie Inorganique, ENSSPICAM, Marseille (France)

    1996-12-01

    Iodine chemistry is one of the most important subjects of research in the field of reactor safety because this element can form volatile species which represent a biological hazard for environment. As the iodine and the peroxide are both present in the sump of the containment in the event of a severe accident on a light water nuclear reactor, it can be important to improve the knowledge on the reaction of oxidation of iodine by hydrogen peroxide. The kinetics of iodine by hydrogen peroxide has been studied in acid solution using two different analytical methods. The first is a UV/Vis spectrophotometer which records the transmitted intensity at 460 nm as a function of time to follow the decrease of iodine concentration, the second is an amperometric method which permits to record the increase of iodine+1 with time thanks to the current of reduction of iodine+1 to molecular iodine. The iodine was generated by Dushman reaction and the series of investigations were made at 40{sup o}C in a continuous stirring tank reactor. The influence of the initial concentrations of iodine, iodate, hydrogen peroxide, H{sup +} ions has been determined. The kinetics curves comprise two distinct chemical phases both for molecular iodine and for iodine+1. The relative importance of the two processes is connected to the initial concentrations of [I{sub 2}], [IO{sub 3}{sup -}], [H{sub 2}O{sub 2}] and [H{sup +}]. A rate law has been determined for the two steps for molecular iodine. (author) figs., tabs., 22 refs.

  4. Electrochemical permeation tests on the kinetics of the hydrogen absorption of palladium and iron

    International Nuclear Information System (INIS)

    Dafft, E.G.

    1977-01-01

    Electrochemical permeation tests were performed to investigate the kinetics of the hydrogen development and hydrogen absorption. The cathode side of the samples was galvanostatically cathodically polarized in different electrolyte solutions with and without additions. THe hydrogen atoms diffusing out of the opposite side for iron and α-palladium were oxidized with potentiostatic, sufficiently anodic polarization. The thus registered stationary current is proportional to the hydrogen activity on the cathode side. Test apparatus and conditions are described. The measurements on iron are discussed. (orig./HPOE) [de

  5. The kinetics of hydrogen removal from liquid sodium

    International Nuclear Information System (INIS)

    Gwyther, J.R.; Whittingham, A.C.

    1981-01-01

    The rates of hydrogen removal from liquid sodium-sodium hydride mixtures have been measured as a function of sodium stirring rate at temperatures up to 420 0 C. Two techniques have been employed - removal under continuous evacuation in which hydrogen flow rates were measured using a capillary flow technique and by argon purging in which hydrogen concentrations in the argon carrier gas were measured by gas chromatography. The results have been used to assess the feasibility of thermal decomposition of sodium hydride for the regeneration of hydride-laden LMFBR cold traps. Studies on the kinetics of desorption of hydrogen from solution in liquid sodium at temperatures up to 400 0 C are also presented and possible kinetic mechanisms discussed. (orig.)

  6. The role of surface oxides on hydrogen sorption kinetics in titanium thin films

    Science.gov (United States)

    Hadjixenophontos, Efi; Michalek, Lukas; Roussel, Manuel; Hirscher, Michael; Schmitz, Guido

    2018-05-01

    Titanium is presently discussed as a catalyst to accelerate the hydrogenation kinetics of hydrogen storage materials. It is however known that H absorption in Ti decisively depends on the surface conditions (presence or absence of the natural surface oxide). In this work, we use Ti thin films of controlled thickness (50-800 nm) as a convenient tool for quantifying the atomic transport. XRD and TEM investigations allow us to follow the hydrogenation progress inside the film. Hydrogenation of TiO2/Ti bi-layers is studied at 300 °C, for different durations (10 s to 600 min) and at varying pressures of pure H2 atmosphere. Under these conditions, the hydrogenation is found to be linear in time. By comparing films with and without TiO2, as well as by studying the pressure dependence of hydrogenation, it is demonstrated that hydrogen transport across the oxide represents the decisive kinetic barrier rather than the splitting of H2 molecules at the surface. Hydrogenation appears by a layer-like reaction initiated by heterogeneous nucleation at the backside interface to the substrate. The linear growth constant and the H diffusion coefficient inside the oxide are quantified, as well as a reliable lower bound to the hydrogen diffusion coefficient in Ti is derived. The pressure dependence of hydrogen absorption is quantitatively modelled.

  7. A kinetic and ESR investigation of iron(II) oxalate oxidation by hydrogen peroxide and dioxygen as a source of hydroxyl radicals

    DEFF Research Database (Denmark)

    Park, J S; Wood, P M; Davies, Michael Jonathan

    1997-01-01

    The reaction of Fe(II) oxalate with hydrogen peroxide and dioxygen was studied for oxalate concentrations up to 20 mM and pH 2-5, under which conditions mono- and bis-oxalate complexes (Fe[II](ox) and Fe[II](ox)2[2-]) and uncomplexed Fe2+ must be considered. The reaction of Fe(II) oxalate...... with hydrogen peroxide (Fe2+ + H2O2 --> Fe3+ + .OH + OH-) was monitored in continuous flow by ESR with t-butanol as a radical trap. The reaction is much faster than for uncomplexed Fe2+ and a rate constant, k = 1 x 10(4) M(-1) s(-1) is deduced for Fe(II)(ox). The reaction of Fe(II) oxalate with dioxygen...... by oxalate. Further ESR studies with DMPO as spin trap reveal that reaction of Fe(II) oxalate with hydrogen peroxide can also lead to formation of the carboxylate radical anion (CO2-), an assignment confirmed by photolysis of Fe(II) oxalate in the presence of DMPO....

  8. Beneficial effect of carbon on hydrogen desorption kinetics from Mg–Ni–In alloy

    International Nuclear Information System (INIS)

    Cermak, J.; Kral, L.

    2013-01-01

    Highlights: ► Beneficial effect of graphitic carbon was observed. ► The effect is optimal up to c opt . ► Above c opt , phase decomposition occurs. ► Indium in studied Mg–Ni-based alloys prevents oxidation. - Abstract: In the present paper, hydrogen desorption kinetics from hydrided Mg–Ni–In–C alloys was investigated. A chemical composition that substantially accelerates hydrogen desorption was found. It was observed that carbon improves the hydrogen desorption kinetics significantly. Its beneficial effect was found to be optimum close to the carbon concentration of about c C ≅ 5 wt.%. With this composition, stored hydrogen can be desorbed readily at temperatures down to about 485 K, immediately after hydrogen charging. This can substantially shorten the hydrogen charging/discharging cycle of storage tanks using Mg–Ni-based alloys as hydrogen storage medium. For higher carbon concentrations, unwanted phases precipitated, likely resulting in deceleration of hydrogen desorption and lower hydrogen storage capacity.

  9. Effect of the strong metal-support interaction on hydrogen sorption kinetics of Pd-capped switchable mirrors

    NARCIS (Netherlands)

    Borgschulte, A.; Westerwaal, R.J.; Rector, J.H.; Dam, B.; Griessen, R.P.; Schoenes, J.

    2004-01-01

    The morphology and electronic structure of Pd clusters grown on oxidized yttrium surfaces are investigated by scanning tunneling microscopy and ultraviolet photoelectron spectroscopy. The hydrogen sorption mediated by the Pd clusters is determined from the optically monitored switching kinetics of

  10. Kinetic Monte Carlo study on the evolution of silicon surface roughness under hydrogen thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Gang; Wang, Yu; Wang, Junzhuan; Pan, Lijia; Yu, Linwei; Zheng, Youdou; Shi, Yi, E-mail: yshi@nju.edu.cn

    2017-08-31

    Highlights: • The KMC method is adopted to investigate the relationships between surface evolution and hydrogen thermal treatment conditions. • The reduction in surface roughness is divided into two stages at relatively low temperatures, both exhibiting exponential dependence on the time. • The optimized surface structure can be obtained by precisely adjusting thermal treatment temperatures and hydrogen pressures. - Abstract: The evolution of a two-dimensional silicon surface under hydrogen thermal treatment is studied by kinetic Monte Carlo simulations, focusing on the dependence of the migration behaviors of surface atoms on both the temperature and hydrogen pressure. We adopt different activation energies to analyze the influence of hydrogen pressure on the evolution of surface morphology at high temperatures. The reduction in surface roughness is divided into two stages, both exhibiting exponential dependence on the equilibrium time. Our results indicate that a high hydrogen pressure is conducive to obtaining optimized surfaces, as a strategy in the applications of three-dimensional devices.

  11. Kinetics of hydrogen isotope exchange reactions

    International Nuclear Information System (INIS)

    Gold, V.; McAdam, M.E.

    1975-01-01

    Under the influence of tritium β-radiation, 1,4-dioxan undergoes hydrogen exchange with the solvent water. The inhibition of the reaction by known electron scavengers (Ag + , Cu 2+ , Ni 2+ , Co 2+ , Zn 2+ , H 3 + O) and also by species with high reactivity towards hydroxyl radicals but negligible reactivity towards solvated electrons (N 3 - , Br - , SCN - ) has been examined in detail. γ-irradiation similarly induces hydrogen exchange. The action of scavengers is interpreted as requiring the involvement of two separately scavengeable primary radiolysis products in the sequence of reactions leading to exchange. The presence of electron scavengers, even at high concentration, does not totally inhibit the exchange, and a secondary exchange route, involving a low vacancy state of inhibitor cations, is considered responsible for the 'unscavengeable' portion of the reaction, by providing an alternative exchange route. Analogies are drawn between the exchange reaction and other radiation-induced reactions that are thought to involve spur processes. Some implication of radiation-chemical studies in water-alcohol mixtures are indicated. (author)

  12. The hydrogen evolution and oxidation kinetics during overdischarging of sealed nickel-metal hydride batteries

    NARCIS (Netherlands)

    Ayeb, A.; Otten, W.M.; Mank, A.J.G.; Notten, P.H.L.

    2006-01-01

    The hydrogen evolution and oxidation kinetics in NiMH batteries have been investigated under temperature-controlled, steady-state, overdischarging conditions within a temperature range of 10 and 50°C and at discharging currents of 1–330 mA (0.0009 to 0.3 C rate). In situ Raman spectroscopic analyses

  13. Synthesis of Mg2Cu nanoparticles on carbon supports with enhanced hydrogen sorption kinetics

    NARCIS (Netherlands)

    Au, Y.S.; Ponthieu, M.; van Zwienen, M.; Zlotea, C.; Cuevas, F.; de Jong, K.P.; de Jongh, P.E.

    2013-01-01

    The reaction kinetics and reversibility for hydrogen sorption were investigated for supported Mg2Cu nanoparticles on carbon. A new preparation method is proposed to synthesize the supported alloy nanoparticles. The motivation of using a support is to separate the nanoparticles to prevent sintering

  14. Kinetic investigation on enantioselective hydrolytic resolution of ...

    African Journals Online (AJOL)

    Kinetic investigation on enantioselective hydrolytic resolution of epichlorohydrin by crude epoxide hydrolase from domestic duck liver. X Ling, D Lu, J Wang, J Chen, L Ding, J Chen, H Chai, P Ouyang ...

  15. Dissolution kinetics of lead telluride in alkali solutions of hydrogen peroxide

    International Nuclear Information System (INIS)

    Danilova, M.G.; Sveshnikova, L.L.; Stavitskaya, T.A.; Repinskij, S.M.

    1991-01-01

    Dissolution kinetics of lead telluride in alkali solutions of hydrogen peroxide was investigated. Dependences of change of PbTe dissolution rate on concentration of hydrogen peroxide and alkali in the solution were obtained. It is shown that dissolution rate of lead telluride is affected by dissolution rate of lead oxide, representing the product of ReTe dissolution. The obtained regularities can be explained by change of solution structure with increase of KOH concentration and by the state of hydrogen peroxide in the solution

  16. Kinetics of Platinum-Catalyzed Decomposition of Hydrogen Peroxide

    Science.gov (United States)

    Vetter, Tiffany A.; Colombo, D. Philip, Jr.

    2003-07-01

    CIBA Vision Corporation markets a contact lens cleaning system that consists of an AOSEPT disinfectant solution and an AOSEPT lens cup. The disinfectant is a buffered 3.0% m/v hydrogen peroxide solution and the cup includes a platinum-coated AOSEPT disc. The hydrogen peroxide disinfects by killing bacteria, fungi, and viruses found on the contact lenses. Because the concentration of hydrogen peroxide needed to disinfect is irritating to eyes, the hydrogen peroxide needs to be neutralized, or decomposed, before the contact lenses can be used again. A general chemistry experiment is described where the kinetics of the catalyzed decomposition of the hydrogen peroxide are studied by measuring the amount of oxygen generated as a function of time. The order of the reaction with respect to the hydrogen peroxide, the rate constant, and the energy of activation are determined. The integrated rate law is used to determine the time required to decompose the hydrogen peroxide to a concentration that is safe for eyes.

  17. Kinetics with deactivation of methylcyclohexane dehydrogenation for hydrogen energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Maria, G; Marin, A; Wyss, C; Mueller, S; Newson, E [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The methylcyclohexane dehydrogenation step to recycle toluene and release hydrogen is being studied as part of a hydrogen energy storage project. The reaction is performed catalytically in a fixed bed reactor, and the efficiency of this step significantly determines overall system economics. The fresh catalyst kinetics and the deactivation of the catalyst by coke play an important role in the process analysis. The main reaction kinetics were determined from isothermal experiments using a parameter sensitivity analysis for model discrimination. An activation energy for the main reaction of 220{+-}11 kJ/mol was obtained from a two-parameter model. From non-isothermal deactivation in PC-controlled integral reactors, an activation energy for deactivation of 160 kJ/mol was estimated. A model for catalyst coke content of 3-17 weight% was compared with experimental data. (author) 3 figs., 6 refs.

  18. Thermodynamic and kinetic properties of hydrogen defect pairs in SrTiO3 from density functional theory

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Bonanos, Nikolaos; Rossmeisl, Jan

    2011-01-01

    A density functional theory investigation of the thermodynamic and kinetic properties of hydrogen–hydrogen defect interactions in the cubic SrTiO3 perovskite is presented. We find a net attraction between two hydrogen atoms with an optimal separation of ∼2.3 Å. The energy gain is ca. 0.33 eV comp...

  19. Improved hydrogen sorption kinetics in wet ball milled Mg hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Li

    2011-05-04

    In this work, wet ball milling method is used in order to improve hydrogen sorption behaviour due to its improved microstructure of solid hydrogen materials. Compared to traditional ball milling method, wet ball milling has benefits on improvement of MgH{sub 2} microstructure and further influences on its hydrogen sorption behavior. With the help of solvent tetrahydrofuran (THF), wet ball milled MgH{sub 2} powder has much smaller particle size and its specific surface area is 7 times as large as that of dry ball milled MgH{sub 2} powder. Although after ball milling the grain size is decreased a lot compared to as-received MgH{sub 2} powder, the grain size of wet ball milled MgH{sub 2} powder is larger than that of dry ball milled MgH{sub 2} powder due to the lubricant effect of solvent THF during wet ball milling. The improved particle size and specific surface area of wet ball milled MgH{sub 2} powder is found to be determining its hydrogen sorption kinetics especially at relatively low temperatures. And it also shows good cycling sorption behavior, which decides on its industrial applicability. With three different catalysts MgH{sub 2} powder shows improved hydrogen sorption behavior as well as the cyclic sorption behavior. Among them, the Nb{sub 2}O{sub 5} catalyst is found to be the most effective one in this work. Compared to the wet ball milled MgH{sub 2} powder, the particle size and specific surface area of the MgH{sub 2} powder with catalysts are similar to the previous ones, while the grain size of the MgH{sub 2} with catalysts is much finer. In this case, two reasons for hydrogen sorption improvement are suggested: one is the reduction of the grain size. The other may be as pointed out in some literatures that formation of new oxidation could enhance the hydrogen sorption kinetics, which is also the reason why its hydrogen capacity is decreased compared to without catalysts. After further ball milling, the specific surface area of wet ball milled Mg

  20. Reduction kinetics of zinc and cadmium sulfides with hydrogen

    International Nuclear Information System (INIS)

    Turgenev, I.S.; Kabisov, I.Kh.; Zviadadze, G.N.; Vasil'eva, O.Yu.

    1985-01-01

    Kinetics of reduction processes of zinc sulfide in the temperature range 800-1100 deg C and of cadmium sulfide 600-900 deg C has been stodied. Activation energies and reaction order in terms of hydrogen are calculated. Thermodynamic processes of reduction depend on aggregate state of the metal formed. For vaporous zinc in the temperature range 1050-950 deq C activation energy constitutes 174 kJ/mol, for liquid in the range 900-850 deg - 151 kJ/mol and reaction order in terms of hydrogen is 1.0. For vaporous cadmium in the temperature range 900-700 deg C activation energy constitutes 144 kJ/mol and reaction order in terms of hydrogen is 0.86, for liquid in the range 675-600 deg C 127 kJ/mol and 0.8 respectively. The processes of zinc and cadmium sulfide reduction proceed in kinetic regime and are limited by the rate of chemical reaction

  1. Equilibrium amide hydrogen exchange and protein folding kinetics

    International Nuclear Information System (INIS)

    Bai Yawen

    1999-01-01

    The classical Linderstrom-Lang hydrogen exchange (HX) model is extended to describe the relationship between the HX behaviors (EX1 and EX2) and protein folding kinetics for the amide protons that can only exchange by global unfolding in a three-state system including native (N), intermediate (I), and unfolded (U) states. For these slowly exchanging amide protons, it is shown that the existence of an intermediate (I) has no effect on the HX behavior in an off-pathway three-state system (I↔U↔N). On the other hand, in an on-pathway three-state system (U↔I↔N), the existence of a stable folding intermediate has profound effect on the HX behavior. It is shown that fast refolding from the unfolded state to the stable intermediate state alone does not guarantee EX2 behavior. The rate of refolding from the intermediate state to the native state also plays a crucial role in determining whether EX1 or EX2 behavior should occur. This is mainly due to the fact that only amide protons in the native state are observed in the hydrogen exchange experiment. These new concepts suggest that caution needs to be taken if one tries to derive the kinetic events of protein folding from equilibrium hydrogen exchange experiments

  2. Understanding the kinetics of sulfate reduction in brines by hydrogen: Progress report

    International Nuclear Information System (INIS)

    Strachan, D.M.

    1988-07-01

    Experiments were conducted with mixtures of hydrogen gas and each of PBB1 and PBB3 brines to examine the reduction kinetics of sulfate in high ionic strength solutions. Results from the experiments with brines showed that the kinetics of sulfate reduction is slower in high ionic strength solutions than the kinetics in low ionic strength solutions. However, the kinetic mechanism does not seem to alter the slow kinetics, but the addition of much larger quantities of sulfide, about 40 mM, does accelerate the reduction of sulfate. Since the proposed reaction mechanism for the reduction of sulfate by hydrogen gas involves the reaction of sulfide with sulfate, slow initial kinetics in the absence of sulfide is understandable, but also implies an unknown rate-limiting reaction. Precipitation of calcium sulfate(s) and calcium sulfide may limit the sulfide and sulfate concentrations to low values. The coexistence of anhydrite and oldhamite may indicate a part of the Ca-S-H 2 O that has not yet been investigated. 6 refs., 4 figs., 3 tabs

  3. Microstructure and hydrogen sorption kinetics of Mg nanopowders with catalyst

    International Nuclear Information System (INIS)

    Revesz, A.; Fatay, D.; Spassov, T.

    2007-01-01

    MgH 2 powders were ball-milled with and without catalysts (Nb 2 O 5 ) under hydrogen in a high-energy mill for 10 h. Morphological, structural and microstructural characterization of the nanocomposites, including particle and crystallite size distribution were carried out before and after hydrogen absorption. In order to study the above-mentioned microstructural parameters imaging and X-ray scattering techniques (high-resolution X-ray diffractometry) have been employed. The effect of the particle and grain size on the hydriding/dehydriding kinetics of ball-milled MgH 2 + catalyst powders was analyzed. The grain and particle size reduction enhances substantially the hydriding/dehydriding

  4. Palladium mixed-metal surface-modified AB5-type intermetallides enhance hydrogen sorption kinetics

    Directory of Open Access Journals (Sweden)

    Roman V. Denys

    2010-09-01

    Full Text Available Surface engineering approaches were adopted in the preparation of advanced hydrogen sorption materials, based on ‘low-temperature’, AB5-type intermetallides. The approaches investigated included micro-encapsulation with palladium and mixed-metal mantles using electroless plating. The influence of micro-encapsulation on the surface morphology and kinetics of hydrogen charging were investigated. It was found that palladium-nickel (Pd-Ni co-deposition by electroless plating significantly improved the kinetics of hydrogen charging of the AB5-type intermetallides at low hydrogen pressure and temperature, after long-term pre-exposure to air. The improvement in the kinetics of hydrogen charging was credited to a synergistic effect between the palladium and nickel atoms in the catalytic mantle and the formation of an ‘interfacial bridge’ for hydrogen diffusion by the nickel atoms in the deposited layer. The developed surface-modified materials may find application in highly selective hydrogen extraction, purification, and storage from impure hydrogen feeds.

  5. Kinetic stabilities of double, tetra- and hexarosette hydrogen-bonded assemblies

    NARCIS (Netherlands)

    Prins, L.J.; Neuteboom, Edda E.; Paraschiv, V.; Crego Calama, Mercedes; Timmerman, P.; Reinhoudt, David

    2002-01-01

    A study of the kinetic stabilities of hydrogen-bonded double, tetra-, and hexarosette assemblies, comprising 36, 72, and 108 hydrogen bonds, respectively, is described. The kinetic stabilities are measured using both chiral amplification and racemization experiments. The chiral amplification studies

  6. Synergistic methane formation kinetics for hydrogen impact on carbon

    International Nuclear Information System (INIS)

    Haasz, A.A.; Davis, J.W.

    1986-06-01

    A physical/chemical model is presented for the reaction kinetics for methane formation from carbon, due to bombardment by energetic (∼ 100's eV) H + ions and thermal (∼ 1 eV) H 0 atoms. While the model was developed for H + and H 0 , it can be readily applied to non-hydrogenic energetic particles (ions or atoms, e.g., Ar + , He + , He) in combination with thermal (∼ 1 eV) hydrogen (again ions or atoms) impacting on carbon. Both collisional (in the case of the energetic particles) and chemical reaction processes are included. Special cases of sub-eV H 0 alone, energetic H + alone and combined H 0 plus H + were considered and fitted to experimental data. Generally good agreement was found between theoretical predictions and experimental results over the experimental flux and H + energy ranges studied (H 0 flux: 6x10 14 - 7x10 15 H 0 /cm 2 s, H + flux: 6x10 12 - 5x10 15 H + /cm 2 s, H + energy: 300 eV/H + and 1 keV/H + )

  7. Elementary Processes and Kinetic Modeling for Hydrogen and Helium Plasmas

    Directory of Open Access Journals (Sweden)

    Roberto Celiberto

    2017-05-01

    Full Text Available We report cross-sections and rate coefficients for excited states colliding with electrons, heavy particles and walls useful for the description of H 2 /He plasma kinetics under different conditions. In particular, the role of the rotational states in resonant vibrational excitations of the H 2 molecule by electron impact and the calculation of the related cross-sections are illustrated. The theoretical determination of the cross-section for the rovibrational energy exchange and dissociation of H 2 molecule, induced by He atom impact, by using the quasi-classical trajectory method is discussed. Recombination probabilities of H atoms on tungsten and graphite, relevant for the determination of the nascent vibrational distribution, are also presented. An example of a state-to-state plasma kinetic model for the description of shock waves operating in H 2 and He-H 2 mixtures is presented, emphasizing also the role of electronically-excited states in affecting the electron energy distribution function of free electrons. Finally, the thermodynamic properties and the electrical conductivity of non-ideal, high-density hydrogen plasma are finally discussed, in particular focusing on the pressure ionization phenomenon in high-pressure high-temperature plasmas.

  8. Thermodynamic modelling and kinetics of hydrogen absorption associated with phase transformations

    International Nuclear Information System (INIS)

    Gondor, G.; Lexcellent, Ch.

    2007-01-01

    The intermetallic are used for hydrogen pressure containers in order to avoid leaks in the case of an hybrid container. The hydrogen atoms are absorbed by the intermetallic which act as a hydrogen sponge. This hydrogen absorption must be modelled for the container design. The Pressure-composition isotherms describe the equilibrium. Out of this equilibrium the kinetics are controlled by different processes, without taking into account the phase transformations. The author presents a new model of the p-c isotherms with the hydrogen absorption kinetics. (A.L.B.)

  9. Kinetic Studies on State of the Art Solid Oxide Cells – A Comparison between Hydrogen/Steam and Reformate Fuels

    DEFF Research Database (Denmark)

    Njodzefon, Jean-Claude; Graves, Christopher R.; Mogensen, Mogens Bjerg

    2015-01-01

    Electrochemical reaction kinetics at the electrodes of Solid Oxide Cells (SOCs) were investigated at 700 °C for two cells with different fuel electrode microstructures as well as on a third cell with a reduced active electrode area. Three fuel mixtures were investigatedhydrogen/steam and refor......Electrochemical reaction kinetics at the electrodes of Solid Oxide Cells (SOCs) were investigated at 700 °C for two cells with different fuel electrode microstructures as well as on a third cell with a reduced active electrode area. Three fuel mixtures were investigatedhydrogen....../steam fuel split into two processes with opposing temperature behavior in the reformate fuels. An 87.5% reduction in active electrode area diminishes the gas conversion impedance in the hydrogen/steam fuel at high fuel flow rates. In both reformates, the second and third lowest frequency processes merged...

  10. The mechanism of the catalytic oxidation of hydrogen sulfide: II. Kinetics and mechanism of hydrogen sulfide oxidation catalyzed by sulfur

    NARCIS (Netherlands)

    Steijns, M.; Derks, F.; Verloop, A.; Mars, P.

    1976-01-01

    The kinetics of the catalytic oxidation of hydrogen sulfide by molecular oxygen have been studied in the temperature range 20–250 °C. The primary reaction product is sulfur which may undergo further oxidation to SO2 at temperatures above 200 °C. From the kinetics of this autocatalytic reaction we

  11. Unravelling the dependence of hydrogen oxidation kinetics on the size of Pt nanoparticles by in operando nanoplasmonic temperature sensing

    DEFF Research Database (Denmark)

    Wettergren, Kristina; Hellman, Anders; Cavalca, Filippo Carlo

    2015-01-01

    We use a noninvasive nanoscale optical-temperature measurement method based on localized surface plasmon resonance to investigate the particle size-dependence of the hydrogen oxidation reaction kinetics on model supported Pt nanocatalysts at atmospheric pressure in operando. With decreasing average...

  12. Kinetics of hydrogen adsorption on MgH{sub 2}/CNT composite

    Energy Technology Data Exchange (ETDEWEB)

    Rather, Sami ullah, E-mail: rathersami@gmail.com; Taimoor, Aqeel Ahmad; Muhammad, Ayyaz; Alhamed, Yahia Abobakor; Zaman, Sharif Fakhruz; Ali, Arshid Mahmood

    2016-05-15

    Highlights: • Hydrogen adsorption comparisons of commercial, milled, and MgH{sub 2} composite. • Hydrogen adsorption capacity and kinetics improves tremendously by CNT embedding. • Unsteady state modeling and simulation of adsorption kinetics. - Abstract: Magnesium hydride (MgH{sub 2})–carbon nanotubes (CNT) composite has been prepared by high-energy ball milling method and their experimental and kinetic hydrogen adsorption studies was assessed. Hydrogen adsorption studies were performed by Sievert’s volumetric apparatus and kinetic evaluation was conducted by surface chemistry and Langmuir–Hinshelwood–Hougen–Watson (LHHW) type mode. Powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were performed. Hydrogen adsorption capacity of commercial MgH{sub 2}, milled MgH{sub 2}, and MgH{sub 2}/CNT composite are found to be 0.04, 0.057, and 0.059 g (H{sub 2})/g (MgH{sub 2}) at 673 K and hydrogen pressure of 4.6 MPa. Addition of 5 wt% of CNTs to MgH{sub 2} proved to be very critical to enhance hydrogen adsorption as well as to improve its kinetics. It was observed that hydrogen adsorption is not in quasi-state equilibrium and is modeled using kinetic rate laws.

  13. Popcorn polymerisation of chloroprene. A kinetic investigation

    International Nuclear Information System (INIS)

    Brough, Neil

    1997-01-01

    The project was sponsored by Du Font Dow Elastomers Ltd (Maydown, N. Ireland), in whose neoprene plant the popcorn polymers are found. The material itself has no commercial value, but grows rapidly and has the ability to block pipes and halt production. Therefore the production equipment containing monomers is all scheduled for 'popcorn search' inspections at intervals that differ according to the prevailing temperatures and monomer concentrations; a process which adds to costs. Prior work within the Queen's University of Belfast has identified the factors which affect the initiation of chlorobutadiene popcorn polymers, but available published and unpublished kinetic studies are in conflict concerning their rate of growth, and there is no data on the dichlorobutadiene popcorn polymer. In consequence, current relief system design procedures are based on a worst case scenario about popcorn growth rates and thus the design may be unduly expensive. The research obtained reliable kinetic data to allow these 'popcorn search' schedules to be rationalised and relief system designs to be improved and as a result to reduce the company's expenditure and improve operational safety margins. The proposed research was to investigate the kinetic behaviour of chlorinated butadiene monomers in the formation of omega- or 'popcorn' polymers. The growth rates of the chloroprene popcorn polymer were investigated at various temperatures in the liquid phase in the pure chloroprene monomer, mixed with other monomers and diluted with toluene in what we term 'Korean' type experiments. In these experiments the growth of popcorn polymer was terminated in a set of identically prepared ampoules after a fixed time. The growth rates of popcorn polymer seeds were obtained over various time periods, namely 24, 43 and 54 hours, at temperatures ranging from 10 deg C to 60 deg C. It was observed that the results differ greatly from those obtained by J.Op.Li. In particular, in the present work it was

  14. Hydrogen absorption kinetics in powdered V + 80 wt.% LaNi5 composite

    International Nuclear Information System (INIS)

    Kumar, Sanjay; Tirpude, Amit; Taxak, Manju; Krishnamurthy, Nagaiyar

    2013-01-01

    Highlights: •Vanadium prevents the pulverization of LaNi 5 . •H absorption capacity LaNi 5 –V composite is higher than LaNi 5 . •H absorption kinetics of LaNi 5 –V composite is relatively faster than V and LaNi 5 . •Fermi energy level of LaNi 5 –V composite lowered by vanadium addition. -- Abstract: The hydrogen absorption behavior of V + 80 wt.% LaNi 5 composite, LaNi 5 and V has been investigated. The LaNi 5 –V composite was prepared by high energy ball-milling technique using high pure vanadium and LaNi 5 powder. Lattice expansion of the composite has been observed in X-ray analysis which indicates the solid solution formation. Presence of free V and traces of V 2 O 5 phase were also observed in the composite. The hydrogen absorption capacity and absorption kinetics of the composite showed improvement as compared to LaNi 5 . The improved kinetics of the composite has been co-related to the change in lattices parameter, Fermi energy level and catalytic property of vanadium. Integrity of the composite has found to be effective even after 20 numbers of hydriding and dehydriding cycles due to the presence of vanadium

  15. Computational investigation of hydrogen storage on B5V3

    Science.gov (United States)

    Guo, Chen; Wang, Chong

    2018-05-01

    Based on density functional theory method with 6-311+G(d,p) basis set, the structures, stability and hydrogen storage capacity of B5V3 have been theoretically investigated. It is found that a maximum of seven hydrogen molecules can be adsorbed on B5V3 with gravimetric uptake capacity of 6.39 wt%. The uptake capacity exceeds the target set by the US Department of Energy for vehicular application. Moreover, the average adsorption energy of B5V3 01 (7H2) is 0.60 eV/H2 in the desirable range of reversible hydrogen storage. The kinetic stability of H2 adsorbed on B5V3 01 is confirmed by using gap between highest occupied molecular orbital (HOMO)and the lowest unoccupied molecular orbital (LUMO). The gap value of B5V3 01 (7H2) is 2.81 eV, which indicates the compound with high stability. In addition, the thermochemistry calculation (Gibbs free energy corrected adsorption energy) is used to analyse if the adsorption is favourable or not at different temperatures. It can be found that the Gibbs corrected adsorption energy of B5V3 01 (7H2) is still positive at 400 K at 1 atm. It means that the adsorption of seven hydrogen molecules on B5V3 01 is energetically favourable in a fairly wide temperature range. All the results show that B5V3 01 can be considered as a promising material for hydrogen storage.

  16. Investigation of hydrogen-deflagration/-detonation

    International Nuclear Information System (INIS)

    Breitung, W.; Redlinger, R.; Werle, H.; Moeschke, M.

    1992-01-01

    The static and dynamic loads of a PWR-containment from hydrogen combustion are investigated theoretically and experimentally. The primary goal is the determination of realistic, not too conservative, upper bounds. The load data are needed to define design requirements for a core-melt resistant containment structure. The following work was performed in 1991: balloon tests; design of a medium scale detonation tube; development of a 1D detonation code; analytical study with SNL/Albuquerque, USA and documentation and presentation of results. (orig./DG)

  17. Investigation of the kinetics of the reactions of oxidation, nitration, and hydrogenation of uranium; Etude cinetique de l'oxydation, de la nitruration et de l'hydruration de l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Adda, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-06-15

    Various physico-chemical methods have been used to investigate the kinetics of the oxidation hydridation and nitridation of uranium. The experimental results show that the kinetics of these reactions are influenced by many factors also the Pilling and Bedworth rule is valid only under very limited conditions. The disagreement between this rule and the experimental results could be explained by the existence of numerous mechanical faults in the compounds obtained by the dry corrosion of the metal. (author) [French] Les cinetiques d'oxydation, d'hydruration et de nitruration de l'uranium ont ete etudiees au moyen de differentes methodes physico-chimiques. Les resultats experimentaux obtenus indiquent qu'un grand nombre de facteurs influencent les cinetiques d'attaque et que la regle de Pilling et Bedworth n'est verifiee que dans des cas tres limites. Les desaccords entre cette regle et les resultats experimentaux s'expliqueraient par l'existence de nombreux defauts mecaniques dans les composes obtenus par corrosion seche du metal. (auteur)

  18. The kinetic isotope effect of hydrogen, deuterium and tritium absorbed and desorbed by titanium

    International Nuclear Information System (INIS)

    Huang Gang; Cao Xiaohua; Long Xinggui

    2008-06-01

    p-t curves of hydrogen, deuterium and tritium absorption at 550-750 degree C and desorption at 350-550 degree C by titanium were investigated. The rate constants of absorption and desorption for hydrogen, deuterium and tritium on each temperature are determined and the activation energy values obtained by this analysis are (55.6 ± 2.4) kJ·mol -1 , (110.2 ± 3.0) kJ·mol -1 and (155.5 ± 3.2) kJ·mol -1 for absorption and (27.1±0.4) KJ·mol -1 , (42.3 ± 1.9) kJ·mol -1 and (62.1±1.6) kJ·mol -1 for desorption respectively. The activation energy value of tritium absorption is highest which shows titanium tritiation is hardest. The activation energy value of tritium desorption is highest and it also can prove that titanium tritide is stablest. There are remarkable kinetic hydrogen isotope effects when titanium absorb and desorb hydrogen, deuterium and tritium. (authors)

  19. Investigation of Laser Peening Effects on Hydrogen Charged Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Zaleski, Tania M. [San Jose State Univ., CA (United States)

    2008-10-30

    Hydrogen-rich environments such as fuel cell reactors can exhibit damage caused by hydrogen permeation in the form of corrosion cracking by lowering tensile strength and decreasing material ductility. Coatings and liners have been investigated, but there were few shot-peening or laser peening studies referenced in the literature with respect to preventing hydrogen embrittlement. The surface compressive residual stress induced by laser peening had shown success in preventing stress corrosion cracking (SCC) for stainless steels in power plants. The question arose if the residual stresses induced by laser peening could delay the effects of hydrogen in a material. This study investigated the effect of laser peening on hydrogen penetration into metal alloys. Three areas were studied: laser peening, hydrogenation, and hydrogen detection. This study demonstrated that laser peening does not reduce the hydrogen permeation into a stainless steel surface nor does it prevent hydrogen embrittlement. The effect of laser peening to reduce hydrogen-assisted fatigue was unclear.

  20. An Experimental and Chemical Kinetics Study of the Combustion of Syngas and High Hydrogen Content Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Santoro, Robers [Pennsylvania State Univ., State College, PA (United States); Dryer, Frederick [Princeton Univ., NJ (United States); Ju, Yiguang [Princeton Univ., NJ (United States)

    2013-09-30

    An integrated and collaborative effort involving experiments and complementary chemical kinetic modeling investigated the effects of significant concentrations of water and CO2 and minor contaminant species (methane [CH4], ethane [C2H6], NOX, etc.) on the ignition and combustion of HHC fuels. The research effort specifically addressed broadening the experimental data base for ignition delay, burning rate, and oxidation kinetics at high pressures, and further refinement of chemical kinetic models so as to develop compositional specifications related to the above major and minor species. The foundation for the chemical kinetic modeling was the well validated mechanism for hydrogen and carbon monoxide developed over the last 25 years by Professor Frederick Dryer and his co-workers at Princeton University. This research furthered advance the understanding needed to develop practical guidelines for realistic composition limits and operating characteristics for HHC fuels. A suite of experiments was utilized that that involved a high-pressure laminar flow reactor, a pressure-release type high-pressure combustion chamber and a high-pressure turbulent flow reactor.

  1. Kinetics and mechanism of nitrobenzene hydrogenation to phenylhydroxylamine in rhenium thiocomplexes solutions

    International Nuclear Information System (INIS)

    Korenyako, G.I.; Belousov, V.M.

    1985-01-01

    A study was made on kinetics of nitrobenzene hydrogenation to phenylhydroxylamine in dimethylformamide solutions of rhenium thiocomplexes. The mechanism of hydrogenation was suggested. Formation of hydride catalyst complex represents the first stage of the process. Kinetic equation derived on the basis of suggested mechanism corresponds satisfactorily with experimental results. Thermodynamic parameters of separate process stages calculated on the basis of equilibrium constant values testify as well to the benefit of suggested mechanism

  2. Kinetic modelling of slurry polymerization of ethylene with a polymer supported Ziegler-Natta catalyst (hydrogen)

    Energy Technology Data Exchange (ETDEWEB)

    Shariati, A.

    1996-12-31

    The kinetics of polymerization of ethylene catalyzed by a polymer supported Ziegler-Natta catalyst were investigated in a semi-batch reactor system. The influences of six polymerization variables were investigated using a central composite design. The variables were monomer partial pressure, catalyst loading, co-catalyst loading, catalyst particle size and hydrogen to monomer ratio. The influence of temperature on rate and polymer properties were investigated. Empirical models were fitted to the experimental data to quantify the effects of the polymerization variables on the rate characteristics and polymer properties. The rate of polymerization exhibited a first order dependency with respect to monomer partial pressure, but a nonlinear relationship with respect to catalyst loading. In the absence of hydrogen, the polymerization rate showed a non-decaying profile at the centre point conditions for the other variables. Catalyst loading and catalyst particle size had a negligible effect on weight-and-number-average molecular weights, while increasing co-catalysts loading lowered the molecular weights, as did increased temperature and hydrogen concentration. refs., figs.

  3. Enhanced hydrogen reaction kinetics of nanostructured Mg-based composites with nanoparticle metal catalysts dispersed on supports

    International Nuclear Information System (INIS)

    Yoo, Yeong; Tuck, Mark; Kondakindi, Rajender; Seo, Chan-Yeol; Dehouche, Zahir; Belkacemi, Khaled

    2007-01-01

    Hydrogen reaction kinetics of nanocrystalline MgH 2 co-catalyzed with Ba 3 (Ca 1+x Nb 2-x )O 9-δ (BCN) proton conductive ceramics and nanoparticle bimetallic catalyst of Ni/Pd dispersed on single wall carbon nanotubes (SWNTs) support has been investigated. The nanoparticle bimetallic catalysts of Ni/Pd supported by SWNTs were synthesized based on a novel polyol method using NiCl 2 .6H 2 O, PdCl 2 , NaOH and ethylene glycol (EG). The nanostructured Mg composites co-catalyzed with BCN and bimetallic supported catalysts exhibited stable hydrogen desorption capacity of 6.3-6.7 wt.% H 2 and the significant enhancement of hydrogen desorption kinetics at 230-300 deg. C in comparison to either non-catalyzed MgH 2 or the nanocomposite of MgH 2 catalyzed with BCN

  4. Thermodynamic, kinetic and mechanistic investigations of ...

    Indian Academy of Sciences (India)

    with respect to the rate determining step and the thermodynamic quantities with respect to the equilibrium steps were evaluated and ... are, (1) to establish a rate law through kinetic measure- ments, (2) to ..... second and third equilibrium steps.

  5. Role of point defects and additives in kinetics of hydrogen storage materials

    Science.gov (United States)

    van de Walle, Chris

    2010-03-01

    First-principles computational studies of hydrogen interactions with storage materials can provide direct insight into the processes of H uptake and release, and may help in developing guidelines for designing storage media with improved storage capacity and kinetics. One important conclusion is that the defects involved in kinetics of semiconducting or insulating H-storage materials are charged, and hence their formation energy is Fermi-level dependent and can be affected by the presence of impurities that change the Fermi level [1,2]. This provides an explanation for the role played by transition-metal impurities in the kinetics of NaAlH4 and related materials. Desorption of H and decomposition of NaAlH4 requires not only mass transport of H but also of Al and/or Na. This process is mediated by native defects. We have investigated the structure, stability, and migration enthalpy of native defects based on density functional theory. The results allow us to estimate diffusion activation energies for the defects that may be involved in mass transport. Most of the relevant defects exist in charge states other than neutral, and consideration of these charge states is essential for a proper description of kinetics. We propose specific new mechanisms to explain the observed activation energies and their dependence on the presence of impurities. We have also expanded our studies to materials other than NaAlH4. In the case of LiBH4 and Li4BN3H10 we have found that the calculations have predictive power in terms of identifying which impurities will actually enhance kinetics. Other complex hydrides that we are currently investigating include Li2NH and LiNH2. [4pt] [1] A. Peles and C. G. Van de Walle, Phys. Rev. B 76, 214101 (2007). [0pt] [2] C. G. Van de Walle, A. Peles, A. Janotti, and G. B. Wilson-Short, Physica B 404, 793 (2009).

  6. Experimental investigations of hydrogen cluster ions

    International Nuclear Information System (INIS)

    Lumig, H.A. van.

    1978-01-01

    Experiments to obtain information about the structure and stability of small hydrogen cluster ions have been performed. Attenuation and fragmentation measurements are presented of hydrogen cluster ions colliding with nitrogen, argon, hydrogen and helium over fixed energy ranges. The total collision and differential fragmentation cross sections are tabulated. (C.F.)

  7. Hydrogen desorption kinetics from zirconium hydride and zirconium metal in vacuum

    International Nuclear Information System (INIS)

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.

    2014-01-01

    The kinetics of hydrogen desorption from zirconium hydride is important in many nuclear design and safety applications. In this paper, a coordinated experimental and modeling study has been used to explicitly demonstrate the applicability of existing kinetic theories for hydrogen desorption from zirconium hydride and α-zirconium. A static synthesis method was used to produce δ-zirconium hydride, and the crystallographic phases of the zirconium hydride were confirmed by X-ray diffraction (XRD). Three obvious stages, involving δ-zirconium hydride, a two-phase region, and α-zirconium, were observed in the hydrogen desorption spectra of two zirconium hydride specimens with H/Zr ratios of 1.62 and 1.64, respectively, which were obtained using thermal desorption spectroscopy (TDS). A continuous, one-dimensional, two-phase moving boundary model, coupled with the zero- and second-order kinetics of hydrogen desorption from δ-zirconium hydride and α-zirconium, respectively, has been developed to reproduce the TDS experimental results. A comparison of the modeling predictions with the experimental results indicates that a zero-order kinetic model is valid for description of hydrogen flux away from the δ-hydride phase, and that a second-order kinetic model works well for hydrogen desorption from α-Zr if the activation energy of desorption is optimized to be 70% of the value reported in the literature

  8. Modeling of hydrogen production methods: Single particle model and kinetics assessment

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.S.; Bellan, J. [California Institute of Technology, Pasadena, CA (United States)

    1996-10-01

    The investigation carried out by the Jet Propulsion Laboratory (JPL) is devoted to the modeling of biomass pyrolysis reactors producing an oil vapor (tar) which is a precursor to hydrogen. This is an informal collaboration with NREL whereby JPL uses the experimentally-generated NREL data both as initial and boundary conditions for the calculations, and as a benchmark for model validation. The goal of this investigation is to find drivers of biomass fast-pyrolysis in the low temperature regime. The rationale is that experimental observations produce sparse discrete conditions for model validation, and that numerical simulations produced with a validated model are an economic way to find control parameters and an optimal operation regime, thereby circumventing costly changes in hardware and tests. During this first year of the investigation, a detailed mathematical model has been formulated for the temporal and spatial accurate modeling of solid-fluid reactions in biomass particles. These are porous particles for which volumetric reaction rate data is known a priori and both the porosity and the permeability of the particle are large enough to allow for continuous gas phase flow. The methodology has been applied to the pyrolysis of spherically symmetric biomass particles by considering previously published kinetics schemes for both cellulose and wood. The results show that models which neglect the thermal and species boundary layers exterior to the particle will generally over predict both the pyrolysis rates and experimentally obtainable tar yields. An evaluation of the simulation results through comparisons with experimental data indicates that while the cellulose kinetics is reasonably accurate, the wood pyrolysis kinetics is not accurate; particularly at high reactor temperatures. Current effort in collaboration with NREL is aimed at finding accurate wood kinetics.

  9. Kinetic Characteristics of Hydrogen Transfer Through Palladium-Modified Membrane

    Science.gov (United States)

    Petriev, I. S.; Frolov, V. Yu.; Bolotin, S. N.; Baryshev, M. G.; Kopytov, G. F.

    2018-01-01

    The paper deals with hydrogen transfer through Pd-23%Ag alloy membrane, the surface of which is modified by the electrolytic deposition of highly dispersed palladium. The dependence between the density of hydrogen flow and its excess pressure on the input surface of membrane is well approximated by the first-order curve. This fact indicates that the process of hydrogen permeability is defined by its dissociation on the input surface. Activation energy of this process is 47.9 kJ/mol which considerably exceeds that of the process of hydrogen transfer through palladium (22-30 kJ/mol). This confirms the fact that the chemisorption is a rate-controlling step of the hydrogen transfer through membrane.

  10. Kinetics of the excited muonic hydrogen in the mixtures of hydrogen isotopes in helium

    International Nuclear Information System (INIS)

    Bystritskij, V.M.; Kravtsov, A.V.; Popov, N.P.

    1989-01-01

    De-excitation of the excited muonic hydrogen in the mixture of hydrogen isotopes and helium is considered. The method is proposed which allows one to determine the rates of the muon transfer from the excited muonic hydrogen to helium nuclei, as well as the probability of the direct muon atomic capture by nuclei of hydrogen isotopes. 20 refs.; 4 figs

  11. Dispersive kinetic model for the non-isothermal reduction of nickel oxide by hydrogen

    International Nuclear Information System (INIS)

    Adnadevic, Borivoj; Jankovic, Bojan

    2008-01-01

    The kinetics of the non-isothermal reduction process of powder nickel oxide samples using hydrogen was investigated by temperature-programmed experiments at the different constant heating rates. The new procedure for the determination of density distribution function of activation energies (ddfE a ), evaluated from the experimentally obtained non-isothermal conversion curves, was developed. The analytical relationships between the corresponding thermo-kinetic parameters for the investigated reduction process were established. From the influence of heating rate on the basic characteristics of ddfE a 's, it was concluded that the evaluated ddfE a 's are completely independent of the heating rate (v h ). It was found that the value of activation energy at the peak of the distribution curve (E a,max ), at all considered heating rates, is in good agreement with the value of E a,0 (96.6 kJ mol -1 ) calculated from the isoconversional dependence of activation energy, in the conversion range of 0.20≤α≤0.60. From the appearances of the true compensation effect, it was concluded that the factor that produces the changes of kinetic parameter values is a conversion fraction (α). Using the model prediction, the experimentally obtained conversion curves are completely described by the evaluated distribution curves (g(E a ) vhj ) at all considered heating rates. It was concluded that the assumption about the distribution of potential energies of oxygen vacancies presented in NiO samples leads to the distribution of activation energies, which determine the kinetics of non-isothermal reduction processes

  12. Improved hydrogen absorption and desorption kinetics of magnesium-based alloy via addition of yttrium

    Science.gov (United States)

    Yang, Tai; Li, Qiang; Liu, Ning; Liang, Chunyong; Yin, Fuxing; Zhang, Yanghuan

    2018-02-01

    Yttrium (Y) is selected to modify the microstructure of magnesium (Mg) to improve the hydrogen storage performance. Thereby, binary alloys with the nominal compositions of Mg24Yx (x = 1-5) are fabricated by inexpensive casting technique. Their microstructure and phase transformation during hydriding and dehydriding process are characterized by using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy analysis. The isothermal hydrogen absorption and desorption kinetics are also measured by a Sievert's-type apparatus at various temperatures. Typical multiphase structures of binary alloy can be clearly observed. All of these alloys can reversibly absorb and desorb large amount of hydrogen at proper temperatures. The addition of Y markedly promotes the hydrogen absorption kinetics. However, it results in a reduction of reversible hydrogen storage capacity. A maximum value of dehydrogenation rate is observed with the increase of Y content. The Mg24Y3 alloy has the optimal desorption kinetic performance, and it can desorb about 5.4 wt% of hydrogen at 380 °C within 12 min. Combining Johnson-Mehl-Avrami kinetic model and Arrhenius equation, the dehydrogenation activation energy of the alloys are evaluated. The Mg24Y3 alloy also has the lowest dehydrogenation activation energy (119 kJ mol-1).

  13. Kinetic analysis on photocatalytic degradation of gaseous acetaldehyde, ammonia and hydrogen sulfide on nanosized porous TiO2 films

    Directory of Open Access Journals (Sweden)

    Iis Sopyan

    2007-01-01

    Full Text Available The characteristics of the UV illumination-assisted degradation of gaseous acetaldehyde, hydrogen sulfide, and ammonia on highly active nanostructured-anatase and rutile films were investigated. It was found that the anatase film showed a higher photocatalytic activity than the counterpart did, however, the magnitude of difference in the photocatalytic activity of both films decreased in the order ammonia>acetaldehyde>hydrogen sulfide. To elucidate the reasons for the observation, the adsorption characteristics and the kinetics of photocatalytic degradation of the three reactants on both films were analyzed. The adsorption analysis examined using a simple Langmuir isotherm, showed that adsorbability on both films decreased in the order ammonia>acetaldehyde>hydrogen sulfide, which can be explained in terms of the decreasing electron-donor capacity. Acetaldehyde and ammonia adsorbed more strongly and with higher coverage on anatase film (1.2 and 5.6 molecules/nm2, respectively than on rutile (0.6 and 4.7 molecules/nm2, respectively. Conversely, hydrogen sulfide molecules adsorbed more strongly on rutile film (0.7 molecules/nm2 than on anatase (0.4 molecules/nm2. Exposure to UV light illumination brought about the photocatalytic oxidation of the three gases in contact with both TiO2 films, and the decrease in concentration were measured, and their kinetics are analyzed in terms of the Langmuir–Hinshelwood kinetic model. From the kinetic analysis, it was found that the anatase film showed the photocatalytic activities that were factors of ~8 and ~5 higher than the rutile film for the degradation of gaseous ammonia and acetaldehyde, respectively. However, the activity was only a factor of ~1.5 higher for the photodegradation of hydrogen sulfide. These observations are systematically explained by the charge separation efficiency and the adsorption characteristics of each catalyst as well as by the physical and electrochemical properties of each

  14. Tailoring Thermodynamics and Kinetics for Hydrogen Storage in Complex Hydrides towards Applications.

    Science.gov (United States)

    Liu, Yongfeng; Yang, Yaxiong; Gao, Mingxia; Pan, Hongge

    2016-02-01

    Solid-state hydrogen storage using various materials is expected to provide the ultimate solution for safe and efficient on-board storage. Complex hydrides have attracted increasing attention over the past two decades due to their high gravimetric and volumetric hydrogen densities. In this account, we review studies from our lab on tailoring the thermodynamics and kinetics for hydrogen storage in complex hydrides, including metal alanates, borohydrides and amides. By changing the material composition and structure, developing feasible preparation methods, doping high-performance catalysts, optimizing multifunctional additives, creating nanostructures and understanding the interaction mechanisms with hydrogen, the operating temperatures for hydrogen storage in metal amides, alanates and borohydrides are remarkably reduced. This temperature reduction is associated with enhanced reaction kinetics and improved reversibility. The examples discussed in this review are expected to provide new inspiration for the development of complex hydrides with high hydrogen capacity and appropriate thermodynamics and kinetics for hydrogen storage. © 2015 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Thermodynamic and kinetics models of hydrogen absorption bound to phase transformations

    International Nuclear Information System (INIS)

    Gondor, G.; Lexcellent, Ch.

    2007-01-01

    In order to design hydrogen gaseous pressure tanks, the absorption (desorption) of hydrogen has to be described and modelled. The equilibrium state can be described by the 'H 2 gas pressure - H 2 composition in the intermetallic compounds - isotherms' (PCI) curves. Several models of PCI curves already exist. At the beginning of the absorption, the hydrogen atoms and the intermetallic compounds form a solid solution (α phase). When the hydrogen concentration increases, a phase transformation appears changing the α solid solution into an hydride (β phase) (solid solution + H 2 ↔ hydride). When all the solid solution has been transformed into hydride, the absorbed hydrogen atoms are in β phase. A new thermodynamic model has been developed in order to take into account this transition phase. The equilibrium state is then given by a relation between the H 2 gas pressure and the H 2 concentration in the intermetallic compound for a fixed external temperature. Two kinetics models have been developed too; at first has been considered that the kinetics depend only of the entire concentration in the intermetallic compound and of the difference between the applied pressure and the equilibrium pressure. Then, has been considered that the hydrogen concentration changes in the metallic matrix. In this last case, for each hydrogenation process, the absorption velocity is calculated to determine the slowest local process which regulates the local evolution of the hydrogen concentration. These two models are based on the preceding thermodynamic model of the PCI curves. (O.M.)

  16. Hydrogen exchange kinetics changes upon formation of the soybean trypsin inhibitor: trypsin complex

    International Nuclear Information System (INIS)

    Woodward, C.K.; Ellis, L.M.

    1975-01-01

    The hydrogen exchange kinetics of the complex of trypsin--soybean trypsin inhibitor (Kunitz) have been compared to the calculated sum of the exchange kinetics for the inhibitor and trypsin measured separately. The exchange rates observed for the complex are substantially less than the sum of the exchange rates in the two individual proteins. These results cannot be accounted for by changes in intermolecular or intramolecular hydrogen bonding. The decrease in exchange rates in the complex are ascribed to changes in solvent accessibility in the component proteins. (U.S.)

  17. KINETIC BEHAVIOR IN THE HYDROGENATION OF FURFURAL OVER IR CATALYSTS SUPPORTED ON TIO2

    OpenAIRE

    ROJAS, HUGO; MARTÍNEZ, JOSÉ J.; REYES, PATRICIO

    2010-01-01

    The kinetics of the liquid-phase hydrogenation of furfuraldehyde to furfuryl alcohol over Ir catalysts supported over TiO2 was studied in the temperature range of 323 to 373 K. The effect of furfural concentration, hydrogen pressure and the solvent effect were also studied. A high selectivity towards furfuryl alcohol was demonstrated. Initial rates describes the order global of the reaction. The experimental data could also be explained using the Langmuir-Hinshelwood model with of a single-si...

  18. Investigation into kinetics of decomposition of nitrates

    International Nuclear Information System (INIS)

    Belov, B.A.; Gorozhankin, Eh.V.; Efremov, V.N.; Sal'nikova, N.S.; Suris, A.L.

    1985-01-01

    Using the method of thermogravimetry, the decomposition of nitrates, Cd(NO 3 ) 2 x4H 2 O, La(NO 3 ) 2 x6H 2 O, Sr(NO 3 ) 2 , ZrO(NO 3 ) 2 x2H 2 O, Y(NO 3 ) 3 x6H 2 O, in particular, is studied in the 20-1000 deg C range. It is shown, that gaseous pyrolysis, products, remaining in the material, hamper greatly the heat transfer required for the decomposition which reduces the reaction order. An effective activation energy of the process is in a satisfactory agreement with the characteristic temperature of the last endotherm. Kinetic parameters are calculated by the minimization method using a computer

  19. Kinetics of Butyrate, Acetate, and Hydrogen Metabolism in a Thermophilic, Anaerobic, Butyrate-Degrading Triculture

    OpenAIRE

    Ahring, Birgitte K.; Westermann, Peter

    1987-01-01

    Kinetics of butyrate, acetate, and hydrogen metabolism were determined with butyrate-limited, chemostat-grown tricultures of a thermophilic butyrate-utilizing bacterium together with Methanobacterium thermoautotrophicum and the TAM organism, a thermophilic acetate-utilizing methanogenic rod. Kinetic parameters were determined from progress curves fitted to the integrated form of the Michaelis-Menten equation. The apparent half-saturation constants, Km, for butyrate, acetate, and dissolved hyd...

  20. Experimental investigation of a hydrogen plasma railgun

    International Nuclear Information System (INIS)

    Harden, B.; Howell, J.R.

    1991-01-01

    This paper reports that the plasma velocity and temperature and composition distributions in a hydrogen plasma railgun were measured. Typical velocities near the muzzle were ∼95 km/s at an initial capacitor bank stored energy of 4.1 kJ. Temperatures ranged from a peak of ∼24000 K in the current-carrying plasma, to ∼85000 K in the tail. The current-carrying plasma was composed of roughly equal parts of hydrogen and copper. Also, computer modeling of armature B probe signals has yielded a simple interpretation of the signal

  1. A feasible kinetic model for the hydrogen oxidation on ruthenium electrodes

    International Nuclear Information System (INIS)

    Rau, M.S.; Gennero de Chialvo, M.R.; Chialvo, A.C.

    2010-01-01

    The hydrogen oxidation reaction (hor) was studied on a polycrystalline ruthenium electrode in H 2 SO 4 solution at different rotation rates (ω). The experimental polarization curves recorded on steady state show the existence of a maximum current with a non-linear dependence of the current density on ω 1/2 . On the basis of the Tafel-Heyrovsky-Volmer kinetic mechanism, coupled with a process of inhibition of active sites by the reversible electroadsorption of hydroxyl species, it was possible to appropriately describe the origin of the maximum current. The corresponding set of kinetic parameters was also calculated from the correlation of the experimental results with the proposed kinetic model.

  2. Microstructure and kinetics evolution in MgH2–TiO2 pellets after hydrogen cycling

    International Nuclear Information System (INIS)

    Mirabile Gattia, D.; Di Girolamo, G.; Montone, A.

    2014-01-01

    Highlights: • MgH 2 was ball milled with TiO 2 anatase phase and expanded graphite to prepare pellets. • Different pellets have been prepared at different compression load. • Pellets were repeatedly cycled under hydrogen pressure to simulate tank exercise and verify their stability. • The compression load highly affects the stability of the pellets to cycling. • Microstructural evolution of the particles due to cycling have been observed. - Abstract: The interest in Mg-based hydrides for solid state hydrogen storage is associated to their capability to reversibly absorb and desorb large amounts of hydrogen. In this work MgH 2 powder with 5 wt.% TiO 2 was ball milled for 10 h. The as-milled nanostructured powder was enriched with 5 wt.% of Expanded Natural Graphite (ENG) and then compacted in cylindrical pellets by cold pressing using different loads. Both the powder and the pellets were subjected to kinetic and thermodynamic tests using a Sievert’s type gas reaction controller, in order to study the microstructural and kinetic changes which took place during repeated H 2 absorption and desorption cycles. The pellets exhibited good kinetic performance and durability, even if the pressure of compaction revealed to be an important parameter for their mechanical stability. Scanning Electron Microscopy observations of as-prepared and cycled pellets were carried out to investigate the evolution of their microstructure. In turn the phase composition before and after cycling was analyzed by X-ray diffraction

  3. Investigation of hydrogen usage in aviation industry

    International Nuclear Information System (INIS)

    Yılmaz, İlker; İlbaş, Mustafa; Taştan, Murat; Tarhan, Cevahir

    2012-01-01

    Highlights: ► We examine usage of liquid hydrogen as a fuel in aircrafts. ► Engine performance is a little better for liquid hydrogen fuel than kerosene. ► Liquid hydrogen can be a potential alternative to kerosene as aviation fuel. ► Usage of liquid hydrogen will provide national independence for fuel supply. ► Increased production of liquid hydrogen will decrease its cost disadvantage. - Abstract: Fossil-based fuels are commonly used in aircraft engines but they have a polluting effect and they cause a greenhouse effect for our world. This study reports a research about aircraft gas turbine engines which are fired by liquid hydrogen (LH 2 ) in terms of performance and environmental aspects. Also, the performance and emissions of LH 2 fueled engines are compared with those of kerosene fired aircraft engines. Same flights from Istanbul to London, and Paris to Kabul are examined to estimate the emission from a conventional aircraft as an application in aviation sector. It is shown that the amount of NO x , HC and CO emissions for traveling by a conventional aircraft for London is 78.36, 1.202 and 22.4 kg, while Paris is 71.55, 1.171 and 21.63 kg, and Kabul is 111.44, 1.36 and 26.11 kg, respectively. For the use of liquid hydrogen as a fuel, amount of gas emissions decreases for any destination like London, Paris and Kabul. Total HC and CO emissions are going to be nearly 0 kg because of lack of carbon in the fuel. Also NO x emission is lower because of wider flammability limit of LH 2 . Results show that the aircraft engines with LH 2 have great potential for emissions reduction and engine performance parameters are a little better for LH 2 fuel. It is strongly emphasized that one of the most important advantages for the use of LH 2 is national independence for fuel supply. Oil cannot be extracted in every countries territory but LH 2 is producible for every country and this is so important for a countries freedom.

  4. Kinetics of hydrogen reduction of titanium-doped molybdenum dioxide

    International Nuclear Information System (INIS)

    He, Qian; Marin-Flores, Oscar; Hu, Shuozhen; Scudiero, Louis; Ha, Su; Norton, M. Grant

    2015-01-01

    Ti-doped MoO 2 was synthesized to broaden the oxygen-to-carbon ratio operating range of MoO 2 for partial oxidation of long-chain hydrocarbons by increasing the redox stability. The structure modification causes the hydrogen reduction mechanism to change from three-dimensional nuclei growth with an activation energy of 61.3 kJ mol −1 to a three-dimensional hydrogen diffusion limited model with an activation energy of 317.9 kJ mol −1 . Because of the enhanced redox stability, Ti-doped MoO 2 has potential as an alternative anode in direct liquid-fed solid oxide fuel cells

  5. Thermodynamics and kinetics of graphene chemistry: a graphene hydrogenation prototype study.

    Science.gov (United States)

    Pham, Buu Q; Gordon, Mark S

    2016-12-07

    The thermodynamic and kinetic controls of graphene chemistry are studied computationally using a graphene hydrogenation reaction and polyaromatic hydrocarbons to represent the graphene surface. Hydrogen atoms are concertedly chemisorped onto the surface of graphene models of different shapes (i.e., all-zigzag, all-armchair, zigzag-armchair mixed edges) and sizes (i.e., from 16-42 carbon atoms). The second-order Z-averaged perturbation theory (ZAPT2) method combined with Pople double and triple zeta basis sets are used for all calculations. It is found that both the net enthalpy change and the barrier height of graphene hydrogenation at graphene edges are lower than at their interior surfaces. While the thermodynamic product distribution is mainly determined by the remaining π-islands of functionalized graphenes (Phys. Chem. Chem. Phys., 2013, 15, 3725-3735), the kinetics of the reaction is primarily correlated with the localization of the electrostatic potential of the graphene surface.

  6. Ion beam investigation of hydrogen implanted in magnesium

    International Nuclear Information System (INIS)

    Chami, A.-C.

    1977-01-01

    The diffusion mechanism for hydrogen implanted in magnesium was investigated by nuclear reaction analysis or channeling. The hydrogen introduced is then in the presence of radiation defects created by implantation. The H( 11 B,α) reaction used allowed the profiles of implanted hydrogen to be drawn. The Winterbon calculations derived from LSS theory (Lindhard, Scharff, Schiott) were used. LSS profiles folding and the excitation curve unfolding give very same results. An analysis of the profile of the defects and the evaluation of the total number of Frenkel pairs produced show that the defects are isolated when low energy light elements are implanted, and hydrogen interactions are effected through point defects. A channeling analysis shows that hydrogen occupies tetrahedral sites as far as the temperature remains lower that the migration temperature (about 100K). Beyonds this temperature, the hydrogen migrates and is trapped on motionless defects [fr

  7. Fluorescence kinetics and positron annihilation kinetics investigations in cadmium sulfide crystals

    Energy Technology Data Exchange (ETDEWEB)

    Grillot, E; Bancie-Grillot, M; Egee, M [Reims Univ., 51 (France)

    1976-03-01

    Fluorescence kinetics and positrons annihilation kinetics investigations on CdS crystals, either very pure or with increasing contents of Ag-ions, led to similar and complementary results. Ag-ions mainly fill the cadmium vacancies of the lattice, building red emission luminogene centres, while green 'edge-emission' ones are destroyed. These latter, which involve an excited level active for high energy series fluorescence, seems actually related to cadmium vacancies.

  8. Kinetics of hydrogen in chromospheres of red dwarfs

    International Nuclear Information System (INIS)

    Bruevich, E.A.; Katsova, M.M.; Livshits, M.A.; AN SSSR, Moscow

    1990-01-01

    A method is suggested and solution is conducted of the stationary equations for an 8-level hydrogen atom with an approximate account for lines radiative transfer in an optically thick layer. Ionization and excitation of hydrogen atoms are caused by electron collisions; the influence of photospheric radiation was neglected. The medium stays motionless, and the photon escape from the layer is connected with gradual diffusion in frequency during multiple scatterings. Mean over the layer probabilities of photon escape are introduced into the stationary equations. They are determined for a finite-thickness layer with an uniform distribution of primary photon sources and with an absorption coefficient accounting for Stark and Doppler effects. As an example of application of the calculations, an interpretation is presented of the data on the Balmer decrement in the maximum of the stellar flare of YZ CMi on March 4, 1985. It is shown that the transition from a steep Balmer decrement to a mildly sloping one is due to a decrease of the photon escape probability in the higher members of Balmer series, i.e. the lines later than H γ

  9. Kinetics of the oxidation of hydrogen sulfite by hydrogen peroxide in aqueous solution:. ionic strength effects and temperature dependence

    Science.gov (United States)

    Maaß, Frank; Elias, Horst; Wannowius, Klaus J.

    Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO -3, by hydrogen peroxide in aqueous non-buffered solution at the low concentration level of 10 -5-10 -6 M, typically found in cloud water. The kinetic data confirm that the rate law reported for the pH range 3-6 at higher concentration levels, rate= kH·[H +]·[HSO -3]·[H 2O 2], is valid at the low concentration level and at low ionic strength Ic. At 298 K and Ic=1.5×10 -4 M, third-order rate constant kH was found to be kH=(9.1±0.5)×10 7 M -2 s -1. The temperature dependence of kH led to an activation energy of Ea=29.7±0.9 kJ mol -1. The effect of the ionic strength (adjusted with NaCl) on rate constant kH was studied in the range Ic=2×10 -4-5.0 M at pH=4.5-5.2 by conductometry and stopped-flow spectrophotometry. The dependence of kH on Ic can be described with a semi-empirical relationship, which is useful for the purpose of comparison and extrapolation. The kinetic data obtained are critically compared with those reported earlier.

  10. Searching out the hydrogen absorption/desorption limiting reaction factors: Strategies allowing to increase kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Zeaiter, Ali, E-mail: ali.zeaiter@femto-st.fr; Chapelle, David; Nardin, Philippe

    2015-10-05

    Highlights: • A macro scale thermodynamic model that simulates the response of a FeTi-X hydride tank is performed, and validated experimentally. • A sensibility study to identify the most influent input variables that can changes very largely the reaction rate. - Abstract: Hydrogen gas has become one of the most promising energy carriers. Main breakthrough concerns hydrogen solid storage, specially based on intermetallic material use. Regarding the raw material abundance and cost, the AB type alloy FeTi is an auspicious candidate to store hydrogen. Its absorption/desorption kinetics is a basic hindrance to common use, compared with more usual hydrides. First, discussions based on literature help us identifying the successive steps leading to metal hydriding, and allow to introduce the physical parameters which drive or limit the reaction. This analysis leads us to suggest strategies in order to increase absorption/desorption kinetics. Attention is then paid to a thermofluidodynamic model, allowing to describe a macroscopic solid storage reactor. Thus, we can achieve a simulation which describes the overall reaction inside the hydrogen reactor and, by varying the sub-mentioned parameters (thermal conductivity, the powder granularity, environment heat exchange…), we attempt to hierarchy the reaction limiting factors. These simulations are correlated to absorption/desorption experiments for which pressure, temperature and hydrogen flow are recorded.

  11. Carbon monoxide activation by organoactinides: a comparative synthetic, thermodynamic, kinetic, and mechanistic investigation of migratory CO insertion into actinide-carbon and actinide-hydrogen bonds to yield eta2-acyls and eta2-formyls

    International Nuclear Information System (INIS)

    Moloy, K.G.; Marks, T.J.

    1984-01-01

    Reported are results of the synthesis, characterization, and carbon monoxide chemistry of a series of sterically hindered thorium alkyls and hydrides of the type Cp' 2 Th(R)(X) (Cp' = eta 5 -C 5 Me 5 ) where R = H, D, methyl, eta-butyl, and CH 2 -t-Bu and X = OCH-t-Bu 2 , OC 6 H 3 -2,6-t-Bu 2 , and O-t-Bu. In addition, improved syntheses of the known complexes [Cp' 2 Th(μ-H)(H)] 2 , Cp' 2 Th(O-t-Bu)(Cl) and Cp' 2 Th(CH 2 -t-Bu)(Cl) are presented. The alkyl complexes undergo facile, irreversible carbonylation to yield eta 2 -acyls that were characterized by a variety of methods. Infrared Ir and 13 C NMR spectra of these complexes demonstrate that strong meta-(acyl)oxygen bonding takes place, fostering a pronounced carbene-like character. Thus, these complexes are characterized by low C-O Ir infrared stretching frequencies (nu/sub CO/ = 1450-1480 cm -1 ) and low-field 13 C NMR chemical shifts (delta/sub 13 C/ 355-370). The hydrides undergo a rapid, reversible, migratory CO insertion to yield formyls that have been characterized spectroscopically at low temperature. Infrared Ir and 13 C NMR spectra of these species are similar to the corresponding acyls, suggesting an analogous eta 2 structure. Variable-temperature equilibrium data show that the insertion of CO into thorium-hydrogen bonds is exothermic by ca. 5 kcal/mol, and this value is compared to that for the analogous alkyls. The equilibrium was also found to exhibit a distinct equilibrium isotope effect upon deuterium substitution, K/sub H//K/sub D/ = 0.31 at -78 0 C. The carbonylation of the complex Cp' 2 Th(n-Bu)(OCH-t-Bu 2 ) was found to obey a second-order rate law where rate = kP/sub CO/ [complex]. The insertion of CO into the Th-H bond of Cp' 2 Th(H)(OCH-t-Bu 2 ) was found by NMR methods to be first order in metal hydride. 55 references, 3 figures, 6 tables

  12. Kinetics of tritium isotope exchange between liquid pyrrole and gaseous hydrogen

    International Nuclear Information System (INIS)

    Stolarz, A.

    1994-01-01

    The kinetics of tritium isotope exchange between liquid pyrrole and gaseous hydrogen has been studied over the temperature range of 290-303 K. The reaction was carried out in the presence of platinum black but in spite of that, it appeared to be relatively slow. The kinetics of the exchange reaction studied could be described by the simple McKay equation. The results obtained suggest that diffusion is the rate-determining step. A mechanism of exchange is proposed. (author) 10 refs.; 2 figs.; 1 tab

  13. Kinetic study of hydrogen peroxide decomposition by catalase in a flow-mix microcalorimetric system

    International Nuclear Information System (INIS)

    Fidaleo, Marcello; Lavecchia, Roberto

    2003-01-01

    The kinetics of hydrogen peroxide decomposition by the enzyme catalase was studied at pH 7.4 in the temperature range 10-30 deg. C. Experiments were performed by the LKB-2277 Thermal Activity Monitor equipped with a flow-mix cylinder. The calorimetric reaction unit was schematised as a tubular reactor operating under plug-flow conditions. A first-order kinetic expression, with respect to both the substrate and the enzyme, was used to describe the rate of hydrogen peroxide decomposition. Regression analysis of calorimetric data provided a molar reaction enthalpy of -87.55 kJ mol -1 and an activation energy of 11 kJ mol -1 . Analysis of model residuals and the normal probability plot indicated that the results obtained were statistically significant

  14. Investigation of hydrogen bubbles behavior in tungsten by high-flux hydrogen implantation

    Science.gov (United States)

    Zhao, Jiangtao; Meng, Xuan; Guan, Xingcai; Wang, Qiang; Fang, Kaihong; Xu, Xiaohui; Lu, Yongkai; Gao, Jun; Liu, Zhenlin; Wang, Tieshan

    2018-05-01

    Hydrogen isotopes retention and bubbles formation are critical issues for tungsten as plasma-facing material in future fusion reactors. In this work, the formation and growing up behavior of hydrogen bubbles in tungsten were investigated experimentally. The planar TEM samples were implanted by 6.0keV hydrogens to a fluence of 3.38 ×1018 H ṡ cm-2 at room temperature, and well-defined hydrogen bubbles were observed by TEM. It was demonstrated that hydrogen bubbles formed when exposed to a fluence of 1.5 ×1018 H ṡ cm-2 , and the hydrogen bubbles grew up with the implantation fluence. In addition, the bubbles' size appeared larger with higher beam flux until saturated at a certain flux, even though the total fluence was kept the same. Finally, in order to understand the thermal annealing effect on the bubbles behavior, hydrogen-implanted samples were annealed at 400, 600, 800, and 1000 °C for 3 h. It was obvious that hydrogen bubbles' morphology changed at temperatures higher than 800 °C.

  15. Investigation of dissolution kinetics of a Nigerian columbite in ...

    African Journals Online (AJOL)

    Investigation of dissolution kinetics of a Nigerian columbite in hydrofluoric acid using the shrinking core model. ... Experimental results indicate that the dissolution rate is chemical reaction controlled, with reaction order of 0.57. Dissolution of over 90 % of the columbite was achieved in 5 h, using 20 M HF at 90 oC with 100 ...

  16. Kinetics of hydrogen evolution in the thermal dissociation of the hydride ZrNiH /SUB 2.8/

    International Nuclear Information System (INIS)

    Chernavskii, P.A.; Lunin, V.V.

    1985-01-01

    The kinetics of hydrogen evolution in the thermal decomposition of ZrNiH /SUB 2.8/ has been studied. The kinetic curve has two rate maxima. It is presumed that the second maximum is related to the phenomenon of critical inhibition that accompanies the phase transition. Apparent activation energies were determined for hydrogen evolution in argon and argon-ethylene atmospheres. The apparent energy increases in the argon-ethylene mixture. On the basis of the activation energy measurements it is presumed that the rate-determining step in hydrogen evolution is either the formation of hydrogen molecules from atoms on the surface of the lateral diffusion of atomic hydrogen. In the region of hydrogen concentration in the hydride corresponding to the phase transition, the rate-determining step is hydrogen diffusion in the hydride

  17. Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg₂Ni-type Alloy by Melt Spinning.

    Science.gov (United States)

    Zhang, Yang-Huan; Li, Bao-Wei; Ren, Hui-Ping; Li, Xia; Qi, Yan; Zhao, Dong-Liang

    2011-01-18

    Mg₂Ni-type Mg₂Ni 1-x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1) alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg₂Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD) of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio () of the (x = 0.4) alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio () from 54.5 to 70.2%, the hydrogen diffusion coefficient (D) from 0.75 × 10 - 11 to 3.88 × 10 - 11 cm²/s and the limiting current density I L from 150.9 to 887.4 mA/g.

  18. In situ hydrogen consumption kinetics as an indicator of subsurface microbial activity

    Science.gov (United States)

    Harris, S.H.; Smith, R.L.; Suflita, J.M.

    2007-01-01

    There are few methods available for broadly assessing microbial community metabolism directly within a groundwater environment. In this study, hydrogen consumption rates were estimated from in situ injection/withdrawal tests conducted in two geochemically varying, contaminated aquifers as an approach towards developing such a method. The hydrogen consumption first-order rates varied from 0.002 nM h-1 for an uncontaminated, aerobic site to 2.5 nM h-1 for a contaminated site where sulfate reduction was a predominant process. The method could accommodate the over three orders of magnitude range in rates that existed between subsurface sites. In a denitrifying zone, the hydrogen consumption rate (0.02 nM h-1) was immediately abolished in the presence of air or an antibiotic mixture, suggesting that such measurements may also be sensitive to the effects of environmental perturbations on field microbial activities. Comparable laboratory determinations with sediment slurries exhibited hydrogen consumption kinetics that differed substantially from the field estimates. Because anaerobic degradation of organic matter relies on the rapid consumption of hydrogen and subsequent maintenance at low levels, such in situ measures of hydrogen turnover can serve as a key indicator of the functioning of microbial food webs and may be more reliable than laboratory determinations. ?? 2007 Federation of European Microbiological Societies.

  19. Superior hydrogen storage kinetics of MgH2 nanoparticles doped with TiF3

    International Nuclear Information System (INIS)

    Xie, L.; Liu, Y.; Wang, Y.T.; Zheng, J.; Li, X.G.

    2007-01-01

    MgH 2 nanoparticles were obtained by hydriding ultrafine magnesium particles which were prepared by hydrogen plasma-metal reaction. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the obtained sample is almost pure MgH 2 phase, without residual magnesium and with an average particle size of ∼300 nm. Milled with 5 wt.% TiF 3 as a doping precursor in a hydrogen atmosphere, the sample desorbed 4.5 wt.% hydrogen in 6 min under an initial hydrogen pressure of ∼0.001 bar at 573 K and absorbed 4.2 wt.% hydrogen in 1 min under ∼20 bar hydrogen at room temperature. Compared with MgH 2 micrometer particles doped with 5 wt.% TiF 3 under the same conditions as the MgH 2 nanoparticles, it is suggested that decrease of particle size is beneficial for enhancing absorption capacity at low temperatures, but has no effect on desorption. In addition, the catalyst was mainly responsible for improving the sorption kinetics and its catalytic mechanism is discussed

  20. Kinetics of butyrate, acetate, and hydrogen metabolism in a thermophilic, anaerobic, butyrate-degrading triculture.

    Science.gov (United States)

    Ahring, B K; Westermann, P

    1987-02-01

    Kinetics of butyrate, acetate, and hydrogen metabolism were determined with butyrate-limited, chemostat-grown tricultures of a thermophilic butyrate-utilizing bacterium together with Methanobacterium thermoautotrophicum and the TAM organism, a thermophilic acetate-utilizing methanogenic rod. Kinetic parameters were determined from progress curves fitted to the integrated form of the Michaelis-Menten equation. The apparent half-saturation constants, K(m), for butyrate, acetate, and dissolved hydrogen were 76 muM, 0.4 mM, and 8.5 muM, respectively. Butyrate and hydrogen were metabolized to a concentration of less than 1 muM, whereas acetate uptake usually ceased at a concentration of 25 to 75 muM, indicating a threshold level for acetate uptake. No significant differences in K(m) values for butyrate degradation were found between chemostat- and batch-grown tricultures, although the maximum growth rate was somewhat higher in the batch cultures in which the medium was supplemented with yeast extract. Acetate utilization was found to be the rate-limiting reaction for complete degradation of butyrate to methane and carbon dioxide in continuous culture. Increasing the dilution rate resulted in a gradual accumulation of acetate. The results explain the low concentrations of butyrate and hydrogen normally found during anaerobic digestion and the observation that acetate is the first volatile fatty acid to accumulate upon a decrease in retention time or increase in organic loading of a digestor.

  1. Microstructure and kinetics evolution in MgH{sub 2}–TiO{sub 2} pellets after hydrogen cycling

    Energy Technology Data Exchange (ETDEWEB)

    Mirabile Gattia, D., E-mail: daniele.mirabile@enea.it; Di Girolamo, G.; Montone, A.

    2014-12-05

    Highlights: • MgH{sub 2} was ball milled with TiO{sub 2} anatase phase and expanded graphite to prepare pellets. • Different pellets have been prepared at different compression load. • Pellets were repeatedly cycled under hydrogen pressure to simulate tank exercise and verify their stability. • The compression load highly affects the stability of the pellets to cycling. • Microstructural evolution of the particles due to cycling have been observed. - Abstract: The interest in Mg-based hydrides for solid state hydrogen storage is associated to their capability to reversibly absorb and desorb large amounts of hydrogen. In this work MgH{sub 2} powder with 5 wt.% TiO{sub 2} was ball milled for 10 h. The as-milled nanostructured powder was enriched with 5 wt.% of Expanded Natural Graphite (ENG) and then compacted in cylindrical pellets by cold pressing using different loads. Both the powder and the pellets were subjected to kinetic and thermodynamic tests using a Sievert’s type gas reaction controller, in order to study the microstructural and kinetic changes which took place during repeated H{sub 2} absorption and desorption cycles. The pellets exhibited good kinetic performance and durability, even if the pressure of compaction revealed to be an important parameter for their mechanical stability. Scanning Electron Microscopy observations of as-prepared and cycled pellets were carried out to investigate the evolution of their microstructure. In turn the phase composition before and after cycling was analyzed by X-ray diffraction.

  2. Kinetics of hydrogen release from dissolutions of ammonia borane in different ionic liquids

    International Nuclear Information System (INIS)

    Valero-Pedraza, María José; Martín-Cortés, Alexandra; Navarrete, Alexander; Bermejo, María Dolores; Martín, Ángel

    2015-01-01

    Ammonia borane is a promising hydrogen storage material that liberates hydrogen by thermolysis at moderate temperatures, but it also presents major limitations for practical applications including a long induction time before the initiation of hydrogen release and a difficult regeneration. Previous works have demonstrated that by dissolution of ammonia borane into several ionic liquids, and particularly in 1-butyl-3-methylimidazolium chloride bmimCl, the induction period at the beginning of the thermolysis is eliminated, but some problems persist, including foaming and the formation of a residue after thermolysis that is insoluble in the ionic liquid. In this work, the release of hydrogen from ammonia borane dissolved in different ionic liquids has been analyzed, measuring the kinetics of hydrogen release, visually following the evolution of the sample during the process using pressure glass tube reactors, and analyzing the residue by spectroscopic techniques. While dissolutions of ammonia borane in most ionic liquids analyzed show similar properties as dissolutions in bmimCl, using ionic liquids with bis(trifluoromethylsulfanyl)imide Tf_2N anion the foaming problem is reduced, and in some cases the residue remains dissolved in the ionic liquid, while with ionic liquids with choline anion higher hydrogen yields are achieved that indicate that the decomposition of ammonia borane proceeds through a different path. - Highlights: • Hydrogen release from ammonia borane dissolved in 13 ionic liquids has been studied. • Induction time is shortened and hydrogen release rate is accelerated in all cases. • The best results are obtained using ionic liquids with Tf_2N anion. • Ch cation ionic liquids enable higher H_2 yield, but cyclotriborazane is produced.

  3. Hydrogen storage thermodynamics and kinetics of LaMg11Ni + x wt.% Ni (x = 100, 200) alloys synthesized by mechanical milling

    International Nuclear Information System (INIS)

    Zhang, Yanghuan; Jia, Zhichao; Central Iron and Steel Research Institute, Beijing; Yuan, Zeming; Qi, Yan; Zhao, Dongliang; Hou, Zhonghui

    2016-01-01

    LaMg 11 Ni + x wt.% Ni (x = 100, 200) composite hydrogen storage alloys with a nanocrystalline/amorphous structure were synthesized using ball milling technology. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were investigated systematically. The hydrogen desorption properties were assessed using a Sieverts apparatus and differential scanning calorimetry. The thermodynamic parameters for the hydrogen absorption and desorption were calculated using the Van't Hoff equation. The hydrogen desorption activation energies of the hydrogenated alloys were also estimated by Arrhenius and Kissinger methods. Results indicate that the amount of Ni added has no effect on the thermodynamics of the alloys, but it significantly improves their absorption and desorption kinetics. Furthermore, the milling time has a great influence on the hydrogen storage properties. To be specific, the hydrogen absorption capacities reach the maximum values with the variation of milling time, and the hydrogen desorption activation energy obviously decreases with increasing milling time.

  4. Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

    Energy Technology Data Exchange (ETDEWEB)

    Costin, Walter L. [School of Mechanical Engineering, The University of Adelaide, SA 5005 (Australia); Lavigne, Olivier, E-mail: Olivier.lavigne@adelaide.edu.au [School of Mechanical Engineering, The University of Adelaide, SA 5005 (Australia); Kotousov, Andrei; Ghomashchi, Reza [School of Mechanical Engineering, The University of Adelaide, SA 5005 (Australia); Linton, Valerie [Energy Pipelines Cooperative Research Centre, Faculty of Engineering, University of Wollongong, NSW 2522 (Australia)

    2016-01-10

    Hydrogen assisted cracking (HAC) is a common type of failure mechanism that can affect a wide range of metals and alloys. Experimental studies of HAC are cumbersome due to various intrinsic and extrinsic parameters and factors (associated with stress, hydrogen and the materials microstructure) contributing to the hydrogen crack kinetics. The microstructure of many materials consists of diverse constituents with characteristic features and mechanical properties which only occur in very small material volumes. The only way to differentiate the effect of these individual constituents on the hydrogen crack kinetics is to miniaturise the testing procedures. In this paper we present a new experimental approach to investigate hydrogen assisted crack growth in a microstructural constituent, i.e. acicular ferrite. For this purpose, sharply notched micro-cantilevers were fabricated with a Focus Ion Beam within this selected microscopic region. Acicular ferrite can be found in many ferrous alloys including ferritic weld metal and has specific features that control its intrinsic susceptibility to HAC. These features were characterised via Electron Backscatter Diffraction and the specimens were subsequently loaded under uncharged and hydrogen charged conditions with a nano-indenter. The outcomes of the testing, demonstrated that the threshold stress intensity factor, K{sub th}, to initiate crack propagation in acicular ferrite ranges between 1.56 MPa m{sup 1/2} and 4.36 MPa m{sup 1/2}. This range is significantly below the values of K{sub th} reported for various ferrous alloys in standard macro-tests. This finding indicates that the mechanisms and resistance to HAC at micro-scale could be very different than at the macro-scale as not all fracture toughening mechanisms may be activated at this scale level.

  5. EFFECT OF DIATOMEAOUS EARTH TREATMENT USING HYDROGEN CHLORIDE AND SULFURIC ACID ON KINETICS OF CADMIUM(II ADSORPTION

    Directory of Open Access Journals (Sweden)

    Nuryono Nuryono

    2010-06-01

    Full Text Available In this research, treatment of diatomaceous earth, Sangiran, Central Java using hydrogen chloride (HCl and sulfuric acid (H2SO4 on kinetics of Cd(II adsorption in aqueous solution has been carried out. The work was conducted by mixing an amount of grounded diatomaceous earth (200 mesh in size with HCl or H2SO4 solution in various concentrations for two hours at temperature range of 100 - 150oC. The mixture was then filtered and washed with water until the filtrate pH is approximately 7 and then the residue was dried for four hours at a temperature of 70oC. The product was used as an adsorbent to adsorb Cd(II in aqueous solution with various concentrations. The Cd(II adsorbed was determined by analyzing the rest of Cd(II in the solution using atomic absorption spectrophotometry. The effect of treatment was evaluated from kinetic parameter of adsorption rate constant calculated based on the simple kinetic model. Results showed  that before equilibrium condition reached, adsorpstion of Cd(II occurred through two steps, i.e. a step tends to follow a reaction of irreversible first order  (step I followed by reaction of reversible first order (step II. Treatment with acids, either hydrogen chloride or sulfuric acid, decreased adsorption rate constant for the step I from 15.2/min to a range of 6.4 - 9.4/min.  However, increasing concentration of acid (in a range of concentration investigated did not give significant and constant change of adsorption rate constant. For step II process,  adsorption involved physical interaction with the sufficient low adsorption energy (in a range of 311.3 - 1001 J/mol.     Keywords: adsorption, cdmium, diatomaceous earth, kinetics.

  6. Ozonation and H2O2/UV treatment of clofibric acid in water: a kinetic investigation.

    Science.gov (United States)

    Andreozzi, Roberto; Caprio, Vincenzo; Marotta, Raffaele; Radovnikovic, Anita

    2003-10-31

    The presence of pharmaceuticals or their active metabolites in surface and ground waters has been recently reported as mainly due to an incomplete removal of these pollutants in sewage treatment plants (STP). Advanced oxidation processes may represent a suitable tool to reduce environmental release of these species by enhancing the global efficiency of reduction of pharmaceuticals in the municipal sewage plant effluents. The present work aims at assessing the kinetics of abatement from aqueous solutions of clofibric acid (a metabolite of the blood lipid regulator clofibrate) which has been found in surface, ground and drinking waters. Ozonation and hydrogen peroxide photolysis are capable of fast removal of this species in aqueous solution, with an almost complete conversion of the organic chlorine content into chloride ions for the investigated reaction conditions. A validation of assessed kinetics at clofibric acid concentrations as low as those found in STP effluents is presented for both systems.

  7. Chemical Kinetics of Hydrogen Atom Abstraction from Allylic Sites by 3O2; Implications for Combustion Modeling and Simulation.

    Science.gov (United States)

    Zhou, Chong-Wen; Simmie, John M; Somers, Kieran P; Goldsmith, C Franklin; Curran, Henry J

    2017-03-09

    Hydrogen atom abstraction from allylic C-H bonds by molecular oxygen plays a very important role in determining the reactivity of fuel molecules having allylic hydrogen atoms. Rate constants for hydrogen atom abstraction by molecular oxygen from molecules with allylic sites have been calculated. A series of molecules with primary, secondary, tertiary, and super secondary allylic hydrogen atoms of alkene, furan, and alkylbenzene families are taken into consideration. Those molecules include propene, 2-butene, isobutene, 2-methylfuran, and toluene containing the primary allylic hydrogen atom; 1-butene, 1-pentene, 2-ethylfuran, ethylbenzene, and n-propylbenzene containing the secondary allylic hydrogen atom; 3-methyl-1-butene, 2-isopropylfuran, and isopropylbenzene containing tertiary allylic hydrogen atom; and 1-4-pentadiene containing super allylic secondary hydrogen atoms. The M06-2X/6-311++G(d,p) level of theory was used to optimize the geometries of all of the reactants, transition states, products and also the hinder rotation treatments for lower frequency modes. The G4 level of theory was used to calculate the electronic single point energies for those species to determine the 0 K barriers to reaction. Conventional transition state theory with Eckart tunnelling corrections was used to calculate the rate constants. The comparison between our calculated rate constants with the available experimental results from the literature shows good agreement for the reactions of propene and isobutene with molecular oxygen. The rate constant for toluene with O 2 is about an order magnitude slower than that experimentally derived from a comprehensive model proposed by Oehlschlaeger and coauthors. The results clearly indicate the need for a more detailed investigation of the combustion kinetics of toluene oxidation and its key pyrolysis and oxidation intermediates. Despite this, our computed barriers and rate constants retain an important internal consistency. Rate constants

  8. Thermogravimetric study of the kinetics of lithium titanate reduction by hydrogen

    International Nuclear Information System (INIS)

    Sonak, Sagar; Rakesh, R.; Jain, Uttam; Mukherjee, Abhishek; Kumar, Sanjay; Krishnamurthy, Nagaiyar

    2014-01-01

    Highlights: • Li 2 TiO 3 powder is synthesized by the gel combustion route. • Activation energy of reduction of Li 2 TiO 3 by H 2 found out to be 27.45 kJ/mol H 2 . • Non-stoichiometric phase of Li 2 TiO 3 is formed in hydrogen atmosphere. • One-dimensional diffusion appears to be the most probable mechanism of reduction. - Abstract: The lithium titanate powder was synthesized by gel-combustion route. The mechanism and the kinetics of hydrogen interaction with lithium titanate powder were studied using non-isothermal thermogravimetric technique. Lithium titanate underwent reduction in hydrogen atmosphere which led to the formation of oxygen deficient non-stoichiometric compound in lithium titanate. One-dimensional diffusion appeared to be the most probable reaction mechanism. The activation energy for reduction of lithium titanate under hydrogen atmosphere was found to be 27.4 kJ/mol/K. Structural changes after hydrogen reduction in lithium titanate were observed in X-ray diffraction analysis

  9. INVESTIGATIONS ON BIOCHEMICAL PURIFICATION OF GROUND WATER FROM HYDROGEN SULFIDE

    Directory of Open Access Journals (Sweden)

    Yu. P. Sedlukho

    2015-01-01

    Full Text Available The paper considers problems and features of biochemical removal of hydrogen sulfide from ground water. The analysis of existing methods for purification of ground water from hydrogen sulfide has been given in the paper. The paper has established shortcomings of physical and chemical purification of ground water. While using aeration methods for removal of hydrogen sulfide formation of colloidal sulfur that gives muddiness and opalescence to water occurs due to partial chemical air oxidation. In addition to this violation of sulfide-carbonate equilibrium taking place in the process of aeration due to desorption of H2S and CO2, often leads to clogging of degasifier nozzles with formed CaCO3 that causes serious operational problems. Chemical methods require relatively large flow of complex reagent facilities, storage facilities and transportation costs.In terms of hydrogen sulfide ground water purification the greatest interest is given to the biochemical method. Factors deterring widespread application of the biochemical method is its insufficient previous investigation and necessity to execute special research in order to determine optimal process parameters while purifying groundwater of a particular water supply source. Biochemical methods for oxidation of sulfur compounds are based on natural biological processes that ensure natural sulfur cycle. S. Vinogradsky has established a two-stage mechanism for oxidation of hydrogen sulfide with sulfur bacteria (Beggiatoa. The first stage presupposes oxidation of hydrogen sulphide to elemental sulfur which is accumulating in the cytoplasm in the form of globules. During the second stage sulfur bacteria begin to oxidize intracellular sulfur to sulfuric acid due to shortage of hydrogen sulfide.The paper provides the results of technological tests of large-scale pilot plants for biochemical purification of groundwater from hydrogen sulfide in semi-industrial conditions. Dependences of water quality

  10. Kinetics of two-stage fermentation process for the production of hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Nath, Kaushik [Department of Chemical Engineering, G.H. Patel College of Engineering and Technology, Vallabh Vidyanagar 388 120, Gujarat (India); Muthukumar, Manoj; Kumar, Anish; Das, Debabrata [Fermentation Technology Laboratory, Department of Biotechnology, Indian Institute of Technology, Kharagpur 721302 (India)

    2008-02-15

    Two-stage process described in the present work is a combination of dark and photofermentation in a sequential batch mode. In the first stage glucose is fermented to acetate, CO{sub 2} and H{sub 2} in an anaerobic dark fermentation by Enterobacter cloacae DM11. This is followed by a successive second stage where acetate is converted to H{sub 2} and CO{sub 2} in a photobioreactor by photosynthetic bacteria, Rhodobacter sphaeroides O.U. 001. The yield of hydrogen in the first stage was about 3.31molH{sub 2}(molglucose){sup -1} (approximately 82% of theoretical) and that in the second stage was about 1.5-1.72molH{sub 2}(molaceticacid){sup -1} (approximately 37-43% of theoretical). The overall yield of hydrogen in two-stage process considering glucose as preliminary substrate was found to be higher compared to a single stage process. Monod model, with incorporation of substrate inhibition term, has been used to determine the growth kinetic parameters for the first stage. The values of maximum specific growth rate ({mu} {sub max}) and K{sub s} (saturation constant) were 0.398h{sup -1} and 5.509gl{sup -1}, respectively, using glucose as substrate. The experimental substrate and biomass concentration profiles have good resemblance with those obtained by kinetic model predictions. A model based on logistic equation has been developed to describe the growth of R. sphaeroides O.U 001 in the second stage. Modified Gompertz equation was applied to estimate the hydrogen production potential, rate and lag phase time in a batch process for various initial concentration of glucose, based on the cumulative hydrogen production curves. Both the curve fitting and statistical analysis showed that the equation was suitable to describe the progress of cumulative hydrogen production. (author)

  11. Computational investigation and design of coordination compounds for hydrogen storage

    DEFF Research Database (Denmark)

    Hummelshøj, Jens Strabo

    Two classes of high capacity hydrogen storage materials, the metal tetrahydroborates and the metal ammines, were investigated at the atomic scale using density functional theory simulations. It was shown that simple model structures could be used to asses the stabilities of complex systems. Trends...

  12. Investigation of combustion characteristics of methane-hydrogen fuels

    Science.gov (United States)

    Vetkin, A. V.; Suris, A. L.; Litvinova, O. A.

    2015-01-01

    Numerical investigations of combustion characteristics of methane-hydrogen fuel used at present in tube furnaces of some petroleum refineries are carried out and possible problems related to change-over of existing furnaces from natural gas to methane-hydrogen fuel are analyzed. The effect of the composition of the blended fuel, associated temperature and emissivity of combustion products, temperature of combustion chamber walls, mean beam length, and heat release on variation in the radiation heat flux is investigated. The methane concentration varied from 0 to 100%. The investigations were carried out both at arbitrary given gas temperatures and at effective temperatures determined based on solving a set of equations at various heat-release rates of the combustion chamber and depended on the adiabatic combustion temperature and the temperature at the chamber output. The approximation dependence for estimation of the radiation heat exchange rate in the radiant chamber of the furnace at change-over to fuel with a greater hydrogen content is obtained. Hottel data were applied in the present work in connection with the impossibility to use approximated formulas recommended by the normative method for heat calculation of boilers to determine the gas emissivity, which are limited by the relationship of partial pressures of water steam and carbon dioxide in combustion products . The effect of the methane-hydrogen fuel on the equilibrium concentration of nitrogen oxides is also investigated.

  13. Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts

    International Nuclear Information System (INIS)

    Mori, T.; Masuda, H.; Imai, H.; Miyamoto, A.; Baba, S.; Murakami, Y.

    1982-01-01

    Kinetics and hydrogen-deuterium isotope effects in the methanation of adsorbed CO molecules on a Ni/SiO 2 catalyst were precisely measured by using pulse surface reaction rate analysis (PSRA). When a CO pulse was injected into flowing hydrogen, it was immediately adsorbed on the catalyst and gradually hydrogenated to CH 4 and H 2 O. The amounts of CH 4 and H 2 O produced by the hydrogenation of the adsorbed CO were determined up to various times, and it was found that CH 4 and H 2 O were produced at the same rate. When O 2 instead of CO was injected, H 2 O was immediately produced. From these results, the rate-determining step of the reaction was found to be C-O bond dissociation of an adsorbed CO molecule or a partially hydrogenated CO species. By PSRA, the rate constant for the C-O bond dissocition process per adsorbed CO molecule (k/sub H/) was determined at various temperatures, and the Arrhenius parameters of the rate constant were obtained. The rate constant in flowing deuterium (k/sub D/) was also determined. it was found that k/sub D/ is considerably larger than k/sub H/, indicating an inverse isotope effect. The average value of k/sub H//k/sub D/ was 0.75. From these results, it was concluded that adsorbed CO is not directly dissociated to surface carbon and oxygen atoms but it is partially hydrogenated before C-O bond dissociation under the conditions of the PSRA experiment. 8 figures

  14. Kinetic energy of solid and liquid para-hydrogen: a path integral Monte Carlo simulation

    International Nuclear Information System (INIS)

    Zoppi, M.; Neumann, M.

    1992-01-01

    The translational (center of mass) kinetic energy of solid and liquid para-hydrogen have been recently measured by means of Deep Inelastic Neutron Scattering. We have evaluated the same quantity, in similar thermodynamic conditions, by means of Path Integral Monte Carlo computer simulation, modelling the system as composed of a set of spherical molecules interacting through a pairwise additive Lennard-Jones potential. In spite of the crude approximations on the interaction potential, the agreement is excellent. The pressure was also computed by means of the same simulations. This quantity, compared with the equation of state for solid para-hydrogen given by Driessen and Silvera, gives an agreement of a lesser quality and a negative value for the liquid state. We attribute this discrepancy to the limitations of the Lennard-Jones potential. (orig.)

  15. Time-resolved pulsed hydrogen/deuterium exchange mass spectrometry probes gaseous proteins structural kinetics.

    Science.gov (United States)

    Rajabi, Khadijeh

    2015-01-01

    A pulsed hydrogen/deuterium exchange (HDX) method has been developed for rapid monitoring of the exchange kinetics of protein ions with D2O a few milliseconds after electrospray ionization (ESI). The stepwise gradual evolution of HDX of multiply charged protein ions was monitored using the pulsed HDX mass spectrometry technique. Upon introducing a very short pulse of D2O (in the μs to ms time scale) into the linear ion trap (LIT) of a time-of-flight (TOF) mass spectrometer, bimodal distributions were detected for the ions of cytochrome c and ubiquitin. Mechanistic details of HDX reactions for ubiquitin and cytochrome c in the gas phase were uncovered and the structural transitions were followed by analyzing the kinetics of HDX.

  16. Solid-state reaction kinetics and optical studies of cadmium doped magnesium hydrogen phosphate crystals

    Science.gov (United States)

    Verma, Madhu; Gupta, Rashmi; Singh, Harjinder; Bamzai, K. K.

    2018-04-01

    The growth of cadmium doped magnesium hydrogen phosphate was successfully carried out by using room temperature solution technique i.e., gel encapsulation technique. Grown crystals were confirmed by single crystal X-ray diffraction (XRD). The structure of the grown crystal belongs to orthorhombic crystal system and crystallizes in centrosymmetric space group. Kinetics of the decomposition of the grown crystals were studied by non-isothermal analysis. Thermo gravimetric / differential thermo analytical (TG/DTA) studies revealed that the grown crystal is stable upto 119 °C. The various steps involved in the thermal decomposition of the material have been analysed using Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova equations for evaluating various kinetic parameters. The optical studies shows that the grown crystals possess wide transmittance in the visible region and significant optical band gap of 5.5ev with cut off wavelength of 260 nm.

  17. Solid-state reaction kinetics of neodymium doped magnesium hydrogen phosphate system

    Science.gov (United States)

    Gupta, Rashmi; Slathia, Goldy; Bamzai, K. K.

    2018-05-01

    Neodymium doped magnesium hydrogen phosphate (NdMHP) crystals were grown by using gel encapsulation technique. Structural characterization of the grown crystals has been carried out by single crystal X-ray diffraction (XRD) and it revealed that NdMHP crystals crystallize in orthorhombic crystal system with space group Pbca. Kinetics of the decomposition of the grown crystals has been studied by non-isothermal analysis. The estimation of decomposition temperatures and weight loss has been made from the thermogravimetric/differential thermo analytical (TG/DTA) in conjuncture with DSC studies. The various steps involved in the thermal decomposition of the material have been analysed using Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova equations for evaluating various kinetic parameters.

  18. Kinetic Monte-Carlo modeling of hydrogen retention and re-emission from Tore Supra deposits

    International Nuclear Information System (INIS)

    Rai, A.; Schneider, R.; Warrier, M.; Roubin, P.; Martin, C.; Richou, M.

    2009-01-01

    A multi-scale model has been developed to study the reactive-diffusive transport of hydrogen in porous graphite [A. Rai, R. Schneider, M. Warrier, J. Nucl. Mater. (submitted for publication). http://dx.doi.org/10.1016/j.jnucmat.2007.08.013.]. The deposits found on the leading edge of the neutralizer of Tore Supra are multi-scale in nature, consisting of micropores with typical size lower than 2 nm (∼11%), mesopores (∼5%) and macropores with a typical size more than 50 nm [C. Martin, M. Richou, W. Sakaily, B. Pegourie, C. Brosset, P. Roubin, J. Nucl. Mater. 363-365 (2007) 1251]. Kinetic Monte-Carlo (KMC) has been used to study the hydrogen transport at meso-scales. Recombination rate and the diffusion coefficient calculated at the meso-scale was used as an input to scale up and analyze the hydrogen transport at macro-scale. A combination of KMC and MCD (Monte-Carlo diffusion) method was used at macro-scales. Flux dependence of hydrogen recycling has been studied. The retention and re-emission analysis of the model has been extended to study the chemical erosion process based on the Kueppers-Hopf cycle [M. Wittmann, J. Kueppers, J. Nucl. Mater. 227 (1996) 186].

  19. A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

    International Nuclear Information System (INIS)

    Ma, Ling-Ling; Lv, Cun-Qin; Wang, Gui-Chang

    2017-01-01

    Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H_2 molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H_2. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of C−H/C−C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H_2 dissociation and

  20. A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

    Science.gov (United States)

    Ma, Ling-Ling; Lv, Cun-Qin; Wang, Gui-Chang

    2017-07-01

    Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H2 molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H2. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of Csbnd H/Csbnd C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H2 dissociation and

  1. A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Ling-Ling [Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071 (China); Lv, Cun-Qin, E-mail: lcq173@126.com [College of Chemistry and Environmental Engineering, Shanxi Datong University, Datong 037009, Shanxi Province (China); Wang, Gui-Chang, E-mail: wangguichang@nankai.edu.cn [Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071 (China)

    2017-07-15

    Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H{sub 2} molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H{sub 2}. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of C−H/C−C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H{sub 2

  2. Kinetics of the hydrogen production reaction in a copper-chlorine water splitting plant

    International Nuclear Information System (INIS)

    Zamfirescu, C.; Naterer, G.F.; Dincer, I.

    2009-01-01

    The exothermic reaction of HCl with particulate Cu occurs during hydrogen production step in the thermochemical copper-chlorine (Cu-Cl) water splitting cycle. In this paper, this chemical reaction is modeled kinetically, and a parametric study is performed to determine the influences of particle size, temperature and molar ratios on the reaction kinetics. It is determined that the residence time of copper particles varies between 10 and 100 s, depending on the operating conditions. The hydrogen conversion at equilibrium varies between 55 and 85%, depending on the reaction temperature. The heat flux at the particle surface, caused by the exothermic enthalpy of reaction, reaches about 3,000 W/m 2 when the particle shrinks to 0.1% from its initial size. A numerical algorithm is developed to solve the moving boundary Stefan problem with a chemical reaction. It predicts the shrinking of copper particles based on the hypothesis that the chemical reaction and heat transfer are decoupled. The model allows for estimation of the temperature of the copper particle, assumed spherical, in the radial direction. The maximum temperature at the interface is higher than the melting point of CuCl by 10-50 o C, depending on the assumed operating conditions. (author)

  3. Thermal desorption spectroscopy for investigating hydrogen isotope behavior in materials

    International Nuclear Information System (INIS)

    Xia Tirui; Yang Hongguang; Zhan Qin; Han Zhibo; He Changshui

    2012-01-01

    The behavior of hydrogen isotope generated in fusion reactor materials is the key issue for safety and economic operation of fusion reactors and becomes an interesting field. In order to investigate the mechanism of hydrogen isotope such as diffusion, release and retention, a high-sensitivity thermal desorption spectroscopy (TDS) in combination with a quadruple mass spectrometer (QMS) was developed. A major technical breakthrough in ultrahigh vacuum (UHV), low hydrogen background, linear heating and sensitivity calibration of TDS system was made. UHV of l × 10 -7 Pa and low hydrogen background of l × 10 -9 Pa were obtained by combining turbo molecule pump and sputter ion pump. Specimens can be linearly heated up to 1173 K at the rate of 1 to 50 K/min under the MCGS PID software. Sensitivity calibration of the TDS system was accomplished using a special deuterium leak in the detector mode of QMS second electron multiplier. The desorption sensitivity coefficient and the minimum detection limit of deuterium desorption rate are 6.22 × l0 24 s -l · and l.24 × l0 -10 s -1 , respectively. The measurement was also routinely conducted on a specimen of standard, deuterium-containing Zr-4 alloy maintained in the laboratory, so as to validate the TDS method. (authors)

  4. A kinetic model for quantitative evaluation of the effect of hydrogen and osmolarity on hydrogen production by Caldicellulosiruptor saccharolyticus

    Directory of Open Access Journals (Sweden)

    Zacchi Guido

    2011-09-01

    Full Text Available Abstract Background Caldicellulosiruptor saccharolyticus has attracted increased interest as an industrial hydrogen (H2 producer. The aim of the present study was to develop a kinetic growth model for this extreme thermophile. The model is based on Monod kinetics supplemented with the inhibitory effects of H2 and osmotic pressure, as well as the liquid-to-gas mass transfer of H2. Results Mathematical expressions were developed to enable the simulation of microbial growth, substrate consumption and product formation. The model parameters were determined by fitting them to experimental data. The derived model corresponded well with experimental data from batch fermentations in which the stripping rates and substrate concentrations were varied. The model was used to simulate the inhibition of growth by H2 and solute concentrations, giving a critical dissolved H2 concentration of 2.2 mmol/L and an osmolarity of 0.27 to 29 mol/L. The inhibition by H2, being a function of the dissolved H2 concentration, was demonstrated to be mainly dependent on H2 productivity and mass transfer rate. The latter can be improved by increasing the stripping rate, thereby allowing higher H2 productivity. The experimentally determined degree of oversaturation of dissolved H2 was 12 to 34 times the equilibrium concentration and was comparable to the values given by the model. Conclusions The derived model is the first mechanistically based model for fermentative H2 production and provides useful information to improve the understanding of the growth behavior of C. saccharolyticus. The model can be used to determine optimal operating conditions for H2 production regarding the substrate concentration and the stripping rate.

  5. Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics

    Science.gov (United States)

    Zhang, Jian; Wang, Tao; Liu, Pan; Liao, Zhongquan; Liu, Shaohua; Zhuang, Xiaodong; Chen, Mingwei; Zschech, Ehrenfried; Feng, Xinliang

    2017-05-01

    Various platinum-free electrocatalysts have been explored for hydrogen evolution reaction in acidic solutions. However, in economical water-alkali electrolysers, sluggish water dissociation kinetics (Volmer step) on platinum-free electrocatalysts results in poor hydrogen-production activities. Here we report a MoNi4 electrocatalyst supported by MoO2 cuboids on nickel foam (MoNi4/MoO2@Ni), which is constructed by controlling the outward diffusion of nickel atoms on annealing precursor NiMoO4 cuboids on nickel foam. Experimental and theoretical results confirm that a rapid Tafel-step-decided hydrogen evolution proceeds on MoNi4 electrocatalyst. As a result, the MoNi4 electrocatalyst exhibits zero onset overpotential, an overpotential of 15 mV at 10 mA cm-2 and a low Tafel slope of 30 mV per decade in 1 M potassium hydroxide electrolyte, which are comparable to the results for platinum and superior to those for state-of-the-art platinum-free electrocatalysts. Benefiting from its scalable preparation and stability, the MoNi4 electrocatalyst is promising for practical water-alkali electrolysers.

  6. Kinetic Modeling of a Silicon Refining Process in a Moist Hydrogen Atmosphere

    Science.gov (United States)

    Chen, Zhiyuan; Morita, Kazuki

    2018-06-01

    We developed a kinetic model that considers both silicon loss and boron removal in a metallurgical grade silicon refining process. This model was based on the hypotheses of reversible reactions. The reaction rate coefficient kept the same form but error of terminal boron concentration could be introduced when relating irreversible reactions. Experimental data from published studies were used to develop a model that fit the existing data. At 1500 °C, our kinetic analysis suggested that refining silicon in a moist hydrogen atmosphere generates several primary volatile species, including SiO, SiH, HBO, and HBO2. Using the experimental data and the kinetic analysis of volatile species, we developed a model that predicts a linear relationship between the reaction rate coefficient k and both the quadratic function of p(H2O) and the square root of p(H2). Moreover, the model predicted the partial pressure values for the predominant volatile species and the prediction was confirmed by the thermodynamic calculations, indicating the reliability of the model. We believe this model provides a foundation for designing a silicon refining process with a fast boron removal rate and low silicon loss.

  7. Experimental and numerical investigations of a hydrogen-assisted laser-induced materials transfer procedure

    International Nuclear Information System (INIS)

    Toet, D.; Smith, P. M.; Sigmon, T. W.; Thompson, M. O.

    2000-01-01

    We present investigations of the mechanisms of a laser-induced transfer technique, which can be used for the spatially selective deposition of materials such as Si. This transfer is effected by irradiating the backside of a hydrogenated amorphous silicon film, deposited on a transparent substrate with an excimer laser pulse. The resulting release and accumulation of hydrogen at the film/substrate interface propels the silicon onto an adjacent receptor wafer. Time-resolved infrared transmission measurements indicate that the amorphous film is melted by the laser pulse and breaks into droplets during ejection. These droplets travel towards the receptor substrate and coalesce upon arrival. The transfer velocity increases as a function of fluence, the rate of increase dropping noticeably around the full melt threshold of the film. At this fluence, the transfer velocity reaches values of around 1000 m/s for typical films. Atomic force microscopy reveals that films transferred below the full melt threshold only partially cover the receptor substrate, while uniform, well-adhering films, which can be smoothed by subsequent laser irradiation, are obtained above it. Transfer of hydrogen-free Si films, on the other hand, does not occur until much higher fluences. The dynamics of the process have been simulated using a semiquantitative numerical model. In this model, hydrogen released from the melt front is instantaneously accumulated at the interface with an initial kinetic energy given by the melting temperature of Si and the enthalpy of solution. The resulting pressure accelerates the Si film, the dynamics of which are modeled using Newtonian mechanics, and the gas cools adiabatically as its kinetic energy is converted to the film's momentum. The results of the calculations are in good agreement with the experimental data. (c) 2000 American Institute of Physics

  8. Influence of the evaporation rate and the evaporation mode on the hydrogen sorption kinetics of air-exposed magnesium films

    International Nuclear Information System (INIS)

    Leon, A.; Knystautas, E.J.; Huot, J.; Schulz, R.

    2006-01-01

    It has been shown that the hydrogen sorption properties of air-exposed magnesium films are influenced by the deposition parameters such as the evaporation rate or the evaporation mode used during their preparation. As the evaporation rate increases, the structure of the film tends to be highly oriented along the [002] direction and the kinetics of hydrogen absorption and desorption are faster. Moreover, the hydrogen sorption kinetics of magnesium films prepared with an electron beam source under a high vacuum are faster by almost a factor of two compared to those prepared using resistive heating under low vacuum. These two parameters reduce drastically the activation and the incubation period during hydrogen absorption and desorption, respectively

  9. Experimental investigation on a pulsating heat pipe with hydrogen

    International Nuclear Information System (INIS)

    Deng, H R; Liu, Y M; Ma, R F; Han, D Y; Gan, Z H; Pfotenhauer, J M

    2015-01-01

    The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb 3 Sn and NbTi, MgB 2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB 2 , this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios. (paper)

  10. Hydrogen kinetics studies of MgH2-FeTi composites

    Science.gov (United States)

    Meena, Priyanka; Jangir, Mukesh; Singh, Ramvir; Sharma, V. K.; Jain, I. P.

    2018-05-01

    MgH2 + x wt% FeTi (x=10, 25, 50) nano composites were ball milled to get nano structured material and characterized for structural, morphological and thermal properties. XRD of the milled samples revealed the formation of MgH2, FeTi, Fe2Ti and H0.06FeTi phases. Morphological studies by SEM were undertaken to investigate the effect of hydrogenation of nanostructure alloy. EDX confirmed elemental composition of the as-prepared alloy. TGA studies showed higher desorption temperature for milled MgH2 compared to x wt% FeTi added MgH2. Activation energy for hydrogen desorption was found to be -177.90, -215.69, -162.46 and -87.93 kJ/mol for milled MgH2 and Mg2+x wt% FeTi (10, 25, 50), showing 89.97 kJ/ mol reduction in activation energy for 50 wt% alloy additives resulting in improved hydrogen storage capacity. DSC investigations were carried out to investigate the effect of alloy on hydrogen absorption behavior of MgH2.

  11. Thermoanalytical investigation of the hydrogen absorption behaviour of Sm2Fe17-xGax at high hydrogen pressures

    International Nuclear Information System (INIS)

    Handstein, A.; Kubis, M.; Gebel, B.; Mueller, K.-H.; Schultz, L.; Gutfleisch, O.; Harris, I.R.; Birmingham Univ.

    1998-01-01

    The complete disproportionation of Sm 2 Fe 17-x Ga x during annealing in hydrogen is hindered due to an increased stability of the compounds with a higher Ga content (x ≥ 1). Therefore the HD process as the first step of HDDR (hydrogenation-disproportionation-desorption-recombination) has to be carried out at a high hydrogen pressure for x ≥ 1. The hydrogen absorption behaviour of Sm 2 Fe 17-x Ga x (x = 0, 0.5, 1 and 2) was investigated by means of hydrogen differential thermal analysis (HDTA) and high pressure differential scanning calorimetry (HPDSC) at hydrogen pressures up to 70 bar. A dependency of hydrogenation and disproportionation temperatures on hydrogen pressure and Ga content was found. The comparison with other substituents (M = Al and Si) instead of M = Ga showed an increased stability of Sm 2 Fe 17-x M x compounds against disproportionation by hydrogen in the sequence Al, Ga and Si. The Curie temperatures of the interstitially hydrogenated Th 2 Zn 17 -type materials increase with the hydrogen pressure. In order to produce coercive and thermally stable Sm 2 Fe 15 Ga 2 C y powder by means of the HDDR process, we recombined material disproportionated at different hydrogen pressures. Preliminary results of magnetic properties of this HDDR treated and gas-carburized Sm 2 Fe 15 Ga 2 C y are discussed. (orig.)

  12. Improving the Kinetics and Thermodynamics of Mg(BH4)2 for Hydrogen Storage

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Brandon [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Klebanoff, Lennie [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Stavila, Vitalie [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Heo, Tae Wook [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ray, Keith [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lee, Jonathan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Baker, Alex [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kang, ShinYoung [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Yu, Hui-Chia [Univ. of Michigan, Ann Arbor, MI (United States); Thornton, Katsuyo [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-10-31

    The objective of this project is to (1) combine theory, synthesis, and characterization across multiple scales to understand the intrinsic kinetic and thermodynamic limitations in MgB2/Mg(BH4)2; (2) construct and apply a flexible, validated, multiscale theoretical framework for modeling (de)hydrogenation kinetics of the Mg-B-H system and related metal hydrides; and (3) devise strategies for improving kinetics and thermodynamics, particularly through nanostructuring and doping. The project has an emphasis on understanding and improving rehydrogenation of MgB2, which has generally been less explored and is key to enabling practical use.

  13. Experimental investigation on oxidation kinetics of germanium by ozone

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaolei, E-mail: wangxiaolei@ime.ac.cn [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Zhao, Zhiqian; Xiang, Jinjuan [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Wang, Wenwu, E-mail: wangwenwu@ime.ac.cn [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Zhang, Jing, E-mail: zhangj@ncut.edu.cn [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Microelectronics Department, North China University of Technology, Beijing 100041 (China); Zhao, Chao; Ye, Tianchun [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

    2016-12-30

    Highlights: • Kinetics mechanism of Ge surface oxidation by ozone at low temperature is experimentally investigated. • The growth process contains initially linear growth region and following parabolic growth region. • The GeO{sub x} thickness vs. oxidation time plot obeys the well-known Deal-Grove or linear parabolic model. • The linear growth region includes the oxidation of two topmost Ge layers, and the oxidation of third layer and following layers of Ge is diffusion limited. • The activation energies for linear and parabolic regions are 0.04 and 0.55 eV, respectively. - Abstract: Oxidation kinetics of germanium surface by ozone at low temperature (≤400 °C) is experimentally investigated. The growth process contains two regions: initial linear growth region and following parabolic growth region. The GeO{sub x} thickness vs. oxidation time plot obeys the well-known Deal-Grove or linear parabolic model. The linear growth region contains reaction of oxygen atoms with surface bond and back bonds of outmost Ge layer. And the activation energy is experimentally estimated to be 0.06 eV. Such small activation energy indicates that the linear growth region is nearly barrier-less. The parabolic growth region starts when the oxygen atoms diffuse into back bonds of second outmost Ge layers. And the activation energy for this process is found to be 0.54 eV. Furthermore, in the ozone oxidation it is not O{sub 3} molecules but O radicals that go through the GeO{sub x} film.

  14. The catalytic oxidation of 1-butene over bismuth molybdate catalysts : V. The kinetics of the oxidation: A. Pulse reaction kinetics; exploratory experiments for a kinetic investigation

    NARCIS (Netherlands)

    Keizer, K.; Batist, P.A.; Schuit, G.C.A.

    1969-01-01

    The kinetics of oxidn. of 1-butene with O on three types of bismuth molybdate catalysts were investigated in pulse expts. For all the catalysts mentioned the kinetics can be expressed by a first-order dependency on the butene pressure and a zero-order dependency on the O pressure. A slight deviation

  15. Simulation of uranium oxides reduction kinetics by hydrogen. Reactivities of germination and growth

    International Nuclear Information System (INIS)

    Brun, C.

    1997-01-01

    The aim of this work is to simulate the reduction by hydrogen of the tri-uranium octo-oxide U 3 O 8 (obtained by uranium trioxide calcination) into uranium dioxide. The kinetics curves have been obtained by thermal gravimetric analysis, the hydrogen and steam pressures being defined. The geometrical modeling which has allowed to explain the trend of the kinetics curves and of the velocity curves is an anisotropic germination-growth modeling. The powder is supposed to be formed of spherical grains with the same radius. The germs of the new UO 2 phase appear at the surface of the U 3 O 8 grains with a specific germination frequency. The growth reactivity is anisotropic and is very large in the tangential direction to the grains surface. Then, the uranium dioxide growths inside the grain and the limiting step is the grain surface. The variations of the growth reactivity and of the germination specific frequency in terms of the gases partial pressures and of the temperature have been explained by two different mechanisms. The limiting step of the growth mechanism is the desorption of water in the uranium dioxide surface. Concerning the germination mechanism the limiting step is a water desorption too but in the tri-uranium octo-oxide surface. The same geometrical modeling and the same germination and growth mechanisms have been applied to the reduction of a tri-uranium octo-oxide obtained by calcination of hydrated uranium trioxide. The values of the germination specific frequency of this solid are nevertheless weaker than those of the solid obtained by direct calcination of the uranium trioxide. (O.M.)

  16. The impact of surface composition on Tafel kinetics leading to enhanced electrochemical insertion of hydrogen in palladium

    Science.gov (United States)

    Dmitriyeva, Olga; Hamm, Steven C.; Knies, David L.; Cantwell, Richard; McConnell, Matt

    2018-05-01

    Our previous work experimentally demonstrated the enhancement of electrochemical hydrogen insertion into palladium by modifying the chemical composition of the cathode surface with Pb, Pt and Bi, referred to as surface promoters. The experiment demonstrated that an optimal combination of the surface promoters led to an increase in hydrogen fugacity of more than three orders of magnitude, while maintaining the same current density. This manuscript discusses the application of Density Functional Theory (DFT) to elucidate the thermodynamics and kinetics of observed enhancement of electrochemical hydrogen insertion into palladium. We present theoretical simulations that: (1) establish the elevation of hydrogen's chemical potential on Pb and Bi surfaces to enhance hydrogen insertion, (2) confirm the increase of a Tafel activation barrier that results in a decrease of the reaction rate at the given hydrogen overpotential, and (3) explain why the surface promoter's coverage needs to be non-uniform, namely to allow hydrogen insertion into palladium bulk while simultaneously locking hydrogen below the surface (the corking effect). The discussed DFT-based method can be used for efficient scanning of different material configurations to design a highly effective hydrogen storage system.

  17. Kinetic modeling of levulinic acid hydrogenation to gamma-valerolactone in water using a carbon supported Ru catalyst

    NARCIS (Netherlands)

    Piskun, A.S.; van de Bovenkamp, H.H.; Rasrendra, C.B.; Winkelman, J.G.M.; Heeres, H.J.

    2016-01-01

    gamma-Valerolactone (GVL) is considered a very interesting green, bio-based platform chemical with highapplication potential for the production of both biofuels and biobased chemicals. In this contribution, wereport a kinetic study on the hydrogenation of levulinic acid (LA) to 4-hydroxypentanoic

  18. On the mean kinetic energy of the proton in strong hydrogen bonded systems

    Energy Technology Data Exchange (ETDEWEB)

    Finkelstein, Y. [Nuclear Research Center–Negev, Beer-Sheva 84190 (Israel); Moreh, R. [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Shang, S. L.; Wang, Y.; Liu, Z. K. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Shchur, Ya. [Institute for Condensed Matter Physics, 1 Svientsitskii str., L’viv 79011 (Ukraine)

    2016-02-07

    The mean atomic kinetic energies of the proton, Ke(H), and of the deuteron, Ke(D), were calculated in moderate and strongly hydrogen bonded (HB) systems, such as the ferro-electric crystals of the KDP type (XH{sub 2}PO{sub 4}, X = K, Cs, Rb, Tl), the DKDP (XD{sub 2}PO{sub 4}, X = K, Cs, Rb) type, and the X{sub 3}H(SO{sub 4}){sub 2} superprotonic conductors (X = K, Rb). All calculations utilized the simulated partial phonon density of states, deduced from density functional theory based first-principle calculations and from empirical lattice dynamics simulations in which the Coulomb, short range, covalent, and van der Waals interactions were accounted for. The presently calculated Ke(H) values for the two systems were found to be in excellent agreement with published values obtained by deep inelastic neutron scattering measurements carried out using the VESUVIO instrument of the Rutherford Laboratory, UK. The Ke(H) values of the M{sub 3}H(SO{sub 4}){sub 2} compounds, in which the hydrogen bonds are centro-symmetric, are much lower than those of the KDP type crystals, in direct consistency with the oxygen-oxygen distance R{sub OO}, being a measure of the HB strength.

  19. On the mean kinetic energy of the proton in strong hydrogen bonded systems

    International Nuclear Information System (INIS)

    Finkelstein, Y.; Moreh, R.; Shang, S. L.; Wang, Y.; Liu, Z. K.; Shchur, Ya.

    2016-01-01

    The mean atomic kinetic energies of the proton, Ke(H), and of the deuteron, Ke(D), were calculated in moderate and strongly hydrogen bonded (HB) systems, such as the ferro-electric crystals of the KDP type (XH 2 PO 4 , X = K, Cs, Rb, Tl), the DKDP (XD 2 PO 4 , X = K, Cs, Rb) type, and the X 3 H(SO 4 ) 2 superprotonic conductors (X = K, Rb). All calculations utilized the simulated partial phonon density of states, deduced from density functional theory based first-principle calculations and from empirical lattice dynamics simulations in which the Coulomb, short range, covalent, and van der Waals interactions were accounted for. The presently calculated Ke(H) values for the two systems were found to be in excellent agreement with published values obtained by deep inelastic neutron scattering measurements carried out using the VESUVIO instrument of the Rutherford Laboratory, UK. The Ke(H) values of the M 3 H(SO 4 ) 2 compounds, in which the hydrogen bonds are centro-symmetric, are much lower than those of the KDP type crystals, in direct consistency with the oxygen-oxygen distance R OO , being a measure of the HB strength

  20. Kinetics of isotopic exchange of [1-3H]saccharides with hydrogen using palladium catalysts

    International Nuclear Information System (INIS)

    Akulov, G.P.; Kayumov, V.G.; Snetkova, E.V.; Kaminskij, Yu.L.

    1988-01-01

    The kinetics was studied of the isotopic exchange of [1- 3 H]saccharides with hydrogen on palladium catalysts. The effect was studied of different factors on the rate of isotopic exchange, e.g., of the composition and structure of saccharides, their concentration in the solution (C), the type of catalyst and of the buffer solution. It was found that by reduced rate of isotopic exchange with hydrogen, all studied saccharides may be arranged into a series independent of the type of catalyst in accordance with the sequence of declining coefficient of relative mobility of l-H atoms during the reaction. Linear dependence was found to exist between the rate constant of the isotopic exchange reaction (r) and the coefficient of relative lability. It was also found that in the range of low concentrations the observed rate constants of isotopic exchange were not dependent on concentration and in the range of higher concentrations, r decreased with increasing C. This character of dependence is justified by the side effect of the processes of sorption on the catalyst. (author). 3 figs., 1 tab., 4 refs

  1. Kinetics of Natural Detoxification of Hydrogen Cyanide Contained In Retted Cassava Roots

    Directory of Open Access Journals (Sweden)

    2016-11-01

    Full Text Available This work presents the kinetics of natural detoxification of hydrogen cyanide contained in retted cassava roots. Retting is traditional fermentation of cassava, performed to soften the roots. During retting, cyanide diffuses into water used for the retting. The fresh cassava roots (bitter and sweet varieties used for this experiment were separately retted at ambient 0 temperature of 30 C. The cyanide content and pH were monitored daily. From the analysis of the experimental results, a first order consecutive rate equation is an adequate tool for explaining the mechanism of HCN reduction (or decay in retted cassava roots. The detoxification constants for the bound cyanide in the bitter and sweet cassava roots were 0.378/day and 0.438/day respectively, while that of the free hydrogen cyanide were 0.63/day and 0.74/day for the bitter and sweet varieties respectively. Cassava tubers from different species cannot be fermented with the same retting condition unless they have same or close functional properties.

  2. Real-time hydrogen/deuterium exchange kinetics via supercharged electrospray ionization tandem mass spectrometry.

    Science.gov (United States)

    Sterling, Harry J; Williams, Evan R

    2010-11-01

    Amide hydrogen/deuterium exchange (HDX) rate constants of bovine ubiquitin in an ammonium acetate solution containing 1% of the electrospray ionization (ESI) "supercharging" reagent m-nitrobenzyl alcohol (m-NBA) were obtained using top-down, electron transfer dissociation (ETD) tandem mass spectrometry (MS). The supercharging reagent replaces the acid and temperature "quench" step in the conventional MS approach to HDX experiments by causing rapid protein denaturation to occur in the ESI droplet. The higher charge state ions that are produced with m-NBA are more unfolded, as measured by ion mobility, and result in higher fragmentation efficiency and higher sequence coverage with ETD. Single amino acid resolution was obtained for 44 of 72 exchangeable amide sites, and summed kinetic data were obtained for regions of the protein where adjacent fragment ions were not observed, resulting in an overall spatial resolution of 1.3 residues. Comparison of these results with previous values from NMR indicates that the supercharging reagent does not cause significant structural changes to the protein in the initial ESI solution and that scrambling or back-exchange is minimal. This new method for top-down HDX-MS enables real-time kinetic data measurements under physiological conditions, similar to those obtained using NMR, with comparable spatial resolution and significantly better sensitivity.

  3. Investigation kinetics mechanisms of adsorption malachite green onto activated carbon

    International Nuclear Information System (INIS)

    Onal, Y.; Akmil-Basar, C.; Sarici-Ozdemir, C.

    2007-01-01

    Lignite was used to prepare activated carbon (T3K618) by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N 2 adsorption isotherm. BET surface area of activated carbon is determined as 1000 m 2 /g. Adsorption capacity of malachite green (MG) onto T3K618 activated carbon was investigated in a batch system by considering the effects of various parameters like initial concentration (100, 150 and 200 mg/L) and temperature (25, 40 and 50 deg. C). The adsorption process was relatively fast and equilibrium was reached after about 20 min for 100, 150 mg/L at all adsorption temperature. Equilibrium time for 200 mg/L was determined as 20 min and 40 min at 298, 313 and 323 K, respectively. Simple mass and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate controlling steps such as external mass transfer, intraparticle diffusion. Pseudo second-order model was found to explain the kinetics of MG adsorption most effectively. It was found that both mass transfer and pore diffusion are important in determining the adsorption rates. The intraparticle diffusion rate constant, external mass transfer coefficient, film and pore diffusion coefficient at various temperatures were evaluated. The activation energy (E a ) was determined as 48.56, 63.16, 67.93 kJ/mol for 100, 150, 200 mg/L, respectively. The Langmiur and Freundlich isotherm were used to describe the adsorption equilibrium studies at different temperatures. Langmiur isotherm shows better fit than Freundlich isotherm in the temperature range studied. The thermodynamic parameters, such as ΔG o , ΔS and ΔH o were calculated. The thermodynamics of dyes-T3K618 system indicates endothermic process

  4. Understanding the Relationship Between Kinetics and Thermodynamics in CO 2 Hydrogenation Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Jeletic, Matthew S. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Hulley, Elliott B. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Helm, Monte L. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Mock, Michael T. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Appel, Aaron M. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Wiedner, Eric S. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Linehan, John C. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States

    2017-08-14

    Linear free-energy relationships have been identified that link the kinetic activity for catalytic hydrogenation of CO2 to formate with the thermodynamic driving force for the rate-limiting steps of catalysis. Cobalt and rhodium bis(diphosphine) complexes with different hydricities (G°H-), acidities (pKa), and free energies for H2 addition (G°H2) were examined. Catalytic CO2 hydrogenation was studied under 1.8 and 20 atm of pressure (1:1 CO2:H2) at room temperature in tetrahydrofuran with a spread of turnover frequencies (TOF) ranging from 0 to 74,000 h-1. The catalysis was followed by 1H and 31P NMR in real time under all conditions to yield information about the rate determining step. Catalysts exhibiting the highest activities were found to have hydride transfer and hydrogen addition steps that were each downhill by approximately 6 to 7 kcal/mol, and the deprotonation step was thermoneutral. The research by M.S.J., A.M.A., E.S.W., and J.C.L. was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The research by E.B.H., M.L.H., and M.T.M. (X-ray crystallography, synthesis) was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. The authors thank Dr. Samantha A. Burgess for assistance in collecting cyclic voltammetry data. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  5. A parametric investigation of hydrogen hcci combustion using a multi-zone model approach

    International Nuclear Information System (INIS)

    Komninos, N.P.; Hountalas, D.T.; Rakopoulos, C.D.

    2007-01-01

    The purpose of the present study is to examine the effect of various operating variables of a homogeneous charge compression ignition (HCCI) engine fueled with hydrogen, using a multi-zone model developed by the authors. The multi-zone model consists of zones, which are allotted spatial locations within the combustion chamber. The model takes into account heat transfer between the zones and the combustion chamber walls, providing a spatial temperature distribution during the closed part of the engine cycle, i.e. compression, combustion and expansion. Mass transfer between zones is also accounted for, based on the geometric configuration of the zones, and includes the flow of mass in and out of the crevice regions, represented by the crevice zone. Combustion is incorporated using chemical kinetics based on a chemical reaction mechanism for the oxidation of hydrogen. This chemical reaction mechanism also includes the reactions for nitrogen oxides formation. Using the multi-zone model a parametric investigation is conducted, in order to determine the effect of engine speed, equivalence ratio, compression ratio, inlet pressure and inlet temperature, on the performance, combustion characteristics and emissions of an HCCI engine fueled with hydrogen

  6. Hydrogen absorption kinetics and structural properties of Mg85Ni10Ca5 and Mg90Ni10

    International Nuclear Information System (INIS)

    Aoki, Masakazu; Saito, Katsushi; Towata, Shin-ichi

    2005-01-01

    Mg 85 Ni 10 Ca 5 and Mg 90 Ni 10 were prepared by melting mixtures of the elements in mild steel crucibles and pouring them into copper molds. Hydrogen absorption kinetics and structural properties of the alloys were characterized by the volumetric method using a Sievert's apparatus, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size of Mg in Mg 85 Ni 10 Ca 5 , which is evaluated by XRD peak broadening, is about 50% smaller than that in Mg 90 Ni 10 . In addition, the nanometer-scale structure composed of Mg, Mg 2 Ni, Mg 2 Ca was observed in Mg 85 Ni 10 Ca 5 . Mg 85 Ni 10 Ca 5 shows better hydrogen absorption kinetics than Mg 90 Ni 10 in the temperature range of room temperature to 573 K. The better absorption kinetics of Mg 85 Ni 10 Ca 5 is mainly attributed to the nanometer-scale structure

  7. Kinetic Modeling of Methionine Oxidation in Monoclonal Antibodies from Hydrogen Peroxide Spiking Studies.

    Science.gov (United States)

    Hui, Ada; Lam, Xanthe M; Kuehl, Christopher; Grauschopf, Ulla; Wang, Y John

    2015-01-01

    When isolator technology is applied to biotechnology drug product fill-finish process, hydrogen peroxide (H2O2) spiking studies for the determination of the sensitivity of protein to residual peroxide in the isolator can be useful for assessing a maximum vapor phase hydrogen peroxide (VPHP) level. When monoclonal antibody (mAb) drug products were spiked with H2O2, an increase in methionine (Met 252 and Met 428) oxidation in the Fc region of the mAbs with a decrease in H2O2 concentration was observed for various levels of spiked-in peroxide. The reaction between Fc-Met and H2O2 was stoichiometric (i.e., 1:1 molar ratio), and the reaction rate was dependent on the concentrations of mAb and H2O2. The consumption of H2O2 by Fc-Met oxidation in the mAb followed pseudo first-order kinetics, and the rate was proportional to mAb concentration. The extent of Met 428 oxidation was half of that of Met 252, supporting that Met 252 is twice as reactive as Met 428. Similar results were observed for free L-methionine when spiked with H2O2. However, mAb formulation excipients may affect the rate of H2O2 consumption. mAb formulations containing trehalose or sucrose had faster H2O2 consumption rates than formulations without the sugars, which could be the result of impurities (e.g., metal ions) present in the excipients that may act as catalysts. Based on the H2O2 spiking study results, we can predict the amount Fc-Met oxidation for a given protein concentration and H2O2 level. Our kinetic modeling of the reaction between Fc-Met oxidation and H2O2 provides an outline to design a H2O2 spiking study to support the use of VPHP isolator for antibody drug product manufacture. Isolator technology is increasing used in drug product manufacturing of biotherapeutics. In order to understand the impact of residual vapor phase hydrogen peroxide (VPHP) levels on protein product quality, hydrogen peroxide (H2O2) spiking studies may be performed to determine the sensitivity of monoclonal antibody

  8. The kinetics of Cr layer coated on TiNi films for hydrogen absorption

    Indian Academy of Sciences (India)

    The effect of hydrogen absorption on electrical resistance with temperature for TiNi and TiNi–Cr thin films was investigated. The TiNi thin films of thickness 800 Å were deposited at different angles ( = 0°, 30°, 45°, 60° and 75°) under 10−5 Torr pressure by thermal evaporation on the glass substrate at room temperature.

  9. Numerical investigation on pulsating heat pipes with nitrogen or hydrogen

    Science.gov (United States)

    Y Han, D.; Sun, X.; Gan, Z. H.; Y Luo, R.; Pfotenhauer, J. M.; Jiao, B.

    2017-12-01

    With flexible structure and excellent performance, pulsating heat pipes (PHP) are regarded as a great solution to distribute cooling power for cryocoolers. The experiments on PHPs with cryogenic fluids have been carried out, indicating their efficient performances in cryogenics. There are large differences in physical properties between the fluids at room and cryogenic temperature, resulting in their different heat transfer and oscillation characteristics. Up to now, the numerical investigations on cryogenic fluids have rarely been carried out. In this paper, the model of the closed-loop PHP with multiple liquid slugs and vapor plugs is performed with nitrogen and hydrogen as working fluids, respectively. The effects of heating wall temperature on the performance of close-looped PHPs are investigated and compared with that of water PHP.

  10. Development of a kinetic model of hydrogen absorption and desorption in magnesium and analysis of the rate-determining step

    Science.gov (United States)

    Kitagawa, Yuta; Tanabe, Katsuaki

    2018-05-01

    Mg is promising as a new light-weight and low-cost hydrogen-storage material. We construct a numerical model to represent the hydrogen dynamics on Mg, comprising dissociative adsorption, desorption, bulk diffusion, and chemical reaction. Our calculation shows a good agreement with experimental data for hydrogen absorption and desorption on Mg. Our model clarifies the evolution of the rate-determining processes as absorption and desorption proceed. Furthermore, we investigate the optimal condition and materials design for efficient hydrogen storage in Mg. By properly understanding the rate-determining processes using our model, one can determine the design principle for high-performance hydrogen-storage systems.

  11. Regulatory and standard issues on hydrogen in 2009. Investigation report

    International Nuclear Information System (INIS)

    Tigreat, Delphine

    2009-01-01

    This report proposes an overview of the French and European regulations and standards regarding the use of hydrogen as an energy vector. The European and French regulations concern hydrogen production, storage and use on site and in transports of hazardous goods, the homologation of hydrogen powered vehicles, or the transport of hydrogen in ducts. Some standards are presented. A comparison is proposed between France and Germany, other European countries and the USA

  12. Investigating the Chemical Reactivity for Hydrogen in Siliciclastic Sediments: two Work Packages of the H2STORE Project

    Science.gov (United States)

    De Lucia, M.; Pilz, P.

    2014-12-01

    The H2STORE ("Hydrogen to Store") collaborative project, funded by the German government, investigates the feasibility of industrial-scale hydrogen storage from excess wind energy in siliciclastic depleted gas and oil reservoirs or suitable saline aquifers. In particular, two work packages (geochemical experiments and modelling) hosted at the German Research Centre for Geosciences (GFZ) focus on the possible impact of hydrogen on formation fluids and on the mineralogical, geochemical and petrophysical properties of reservoirs and caprocks. Laboratory experiments expose core samples from several potential reservoirs to pure hydrogen or hydrogen mixtures under site-specific conditions (temperatures up to 200 °C and pressure up to 300 bar). The resulting qualitative and, whereas possible, quantitative data are expected to ameliorate the precision of predictive geochemical and reactive transport modelling, which is also performed within the project. The combination of experiments and models will improve the knowledge about: (1) solubility model and mixing rule for of hydrogen and its gas mixtures in high saline formation fluids; (2) hydrogen reactivity in a broad spectrum of P-T conditions; (3) thermodynamics and kinetics of mineral dissolution or precipitation reactions and redox processes. It is known that under specific P-T conditions reactions between hydrogen and anorganic rock components such as carbonates can occur. However these conditions have never been precisely defined to date. A precise estimation of the hydrogen impact on reservoir behavior of different siliciclastic rock types is crucial for site selection and optimization of storage depth. Enhancing the overall understanding of such systems will benefit the operational reliability, the ecological tolerance, and the economic efficiency of future energy storing plants, crucial aspects for public acceptance and for industrial investors.

  13. Investigation of the explosion hazards of hydrogen sulphide. (Phase II)

    International Nuclear Information System (INIS)

    Moen, I.O.

    1986-01-01

    The results of Phase II of an investigation directed towards quantifying the explosive hazards of hydrogen sulphide in air are described. This second and final phase is focussed on flame acceleration until detonation in obstacle environments simulating a heavy water plant. The results of previous experimental tests, both small and large scale, are compiled and summarized and the results of a series of flame acceleration tests are reported. These tests were performed in order to assess the potential for damaging explosions in simulated industrial environments with repeated obstacles. The experimented apparatus consisted of a channel 1.8 m x 1.8 m in cross-section and 15.5 m long. Two obstacle configurations were tested, corresponding to 500 mm or 220 mm diameter tubes mounted across the channel at regular intervals. Tests were performed with acetylene, propane and hydrogen sulphide fuels. The results of numerical simulation are also reported and compared with the observed results. Scaling predictions are also made. The key results are summarized in the main text, and detailed reports covering the various aspects are included in three annexes

  14. Investigation of the explosion hazards of hydrogen sulphide. Phase II

    International Nuclear Information System (INIS)

    Moen, I.O.

    1986-01-01

    The results of Phase II of an investigation directed towards quantifying the explosive hazards of hydrogen sulphide in air are described. This second and final phase is focussed on flame acceleration until detonation in obstacle environments simulating a heavy water plant. The results of previous experimental tests, both small and large scale, are compiled and summarized and the results of a series of flame acceleration tests are reported. These tests were performed in order to assess the potential for damaging explosions in simulated industrial environments with repeated obstacles. The experimented apparatus consisted of a channel 1.8 m x 1.8 m in cross-section and 15.5 m long. Two obstacle configurations were tested, corresponding to 500 mm or 220 mm diameter tubes mounted across the channel at regular intervals. Tests were performed with acetylene, propane and hydrogen sulphide fuels. The results of numerical simulation are also reported and compared with the observed results. Scaling predictions are also made. The key results are summarized in the main text, and detailed reports covering the various aspects are included in three annexes

  15. Hydrogen/Oxygen Reactions at High Pressures and Intermediate Temperatures: Flow Reactor Experiments and Kinetic Modeling

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Glarborg, Peter

    A series of experimental and numerical investigations into hydrogen oxidation at high pressures and intermediate temperatures has been conducted. The experiments were carried out in a high pressure laminar flow reactor at 50 bar pressure and a temperature range of 600–900 K. The equivalence ratio......, the mechanism is used to simulate published data on ignition delay time and laminar burning velocity of hydrogen. The flow reactor results show that at reducing, stoichiometric, and oxidizing conditions, conversion starts at temperatures of 750–775 K, 800–825 K, and 800–825 K, respectively. In oxygen atmosphere......, ignition occurs at the temperature of 775–800 K. In general, the present model provides a good agreement with the measurements in the flow reactor and with recent data on laminar burning velocity and ignition delay time....

  16. Field-controlled electron transfer and reaction kinetics of the biological catalytic system of microperoxidase-11 and hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    Yongki Choi

    2011-12-01

    Full Text Available Controlled reaction kinetics of the bio-catalytic system of microperoxidase-11 and hydrogen peroxide has been achieved using an electrostatic technique. The technique allowed independent control of 1 the thermodynamics of the system using electrochemical setup and 2 the quantum mechanical tunneling at the interface between microperoxidase-11 and the working electrode by applying a gating voltage to the electrode. The cathodic currents of electrodes immobilized with microperoxidase-11 showed a dependence on the gating voltage in the presence of hydrogen peroxide, indicating a controllable reduction reaction. The measured kinetic parameters of the bio-catalytic reduction showed nonlinear dependences on the gating voltage as the result of modified interfacial electron tunnel due to the field induced at the microperoxidase-11-electrode interface. Our results indicate that the kinetics of the reduction of hydrogen peroxide can be controlled by a gating voltage and illustrate the operation of a field-effect bio-catalytic transistor, whose current-generating mechanism is the conversion of hydrogen peroxide to water with the current being controlled by the gating voltage.

  17. Co-fermentation of sewage sludge with ryegrass for enhancing hydrogen production: Performance evaluation and kinetic analysis.

    Science.gov (United States)

    Yang, Guang; Wang, Jianlong

    2017-11-01

    The low C/N ratio and low carbohydrate content of sewage sludge limit its application for fermentative hydrogen production. In this study, perennial ryegrass was added as the co-substrate into sludge hydrogen fermentation with different mixing ratios for enhancing hydrogen production. The results showed that the highest hydrogen yield of 60mL/g-volatile solids (VS) added was achieved when sludge/perennial ryegrass ratio was 30:70, which was 5 times higher than that from sole sludge. The highest VS removal of 21.8% was also achieved when sludge/perennial ryegrass ratio was 30:70, whereas VS removal from sole sludge was only 0.7%. Meanwhile, the co-fermentation system simultaneously improved hydrogen production efficiency and organics utilization of ryegrass. Kinetic analysis showed that the Cone model fitted hydrogen evolution better than the modified Gompertz model. Furthermore, hydrogen yield and VS removal increased with the increase of dehydrogenase activity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. A study on the kinetics of hydrogen reduction of molybdenum disulphide powders

    International Nuclear Information System (INIS)

    Mehdi Afsahi, M.; Sohrabi, Morteza; Vasant Kumar, R.; Ale Ebrahim, Habib

    2008-01-01

    In order to achieve direct reduction of molybdenite in presence of a sulphur scavenger such as CaO such that SO 2 emission is completely avoided, it is important to maximise the rate of the partial reaction involving molybdenite and hydrogen (without lime) given the low thermodynamic driving force for this reaction. Accordingly, reaction of molybdenum disulphide powders with hydrogen was investigated by thermogravimetric method. Effect of temperature and concentration on the reaction rate was studied under such conditions that resistance to mass transfer arising from external film, between particles and intra-grain was negligible. The operating temperature ranged between 973 and 1173 K while the hydrogen concentration was varied between 30 and 100%. The experimental data obtained under the above conditions were analyzed by applying 'the shrinking unreacted core model'. The reduction reaction was found to be first order with respect to the gaseous reactant. Pre-exponential factor and activation energy have been determined to be 3.91 x 10 3 cm min -1 and 139.0 kJ mol -1 , respectively. Activation energy obtained from a fitted model, agreed well with the values determined from the model-free methods using isothermal measurements

  19. A study on the kinetics of hydrogen reduction of molybdenum disulphide powders

    Energy Technology Data Exchange (ETDEWEB)

    Mehdi Afsahi, M. [Amirkabir University of Technology, Department of Chemical Engineering, Tehran 15914 (Iran, Islamic Republic of); University of Cambridge, Department of Materials Sciences and Metallurgy, Cambridge CB2 3QZ (United Kingdom)], E-mail: mma50@cam.ac.uk; Sohrabi, Morteza [Amirkabir University of Technology, Department of Chemical Engineering, Tehran 15914 (Iran, Islamic Republic of); Vasant Kumar, R. [University of Cambridge, Department of Materials Sciences and Metallurgy, Cambridge CB2 3QZ (United Kingdom); Ale Ebrahim, Habib [Amirkabir University of Technology, Department of Chemical Engineering, Tehran 15914 (Iran, Islamic Republic of)

    2008-07-10

    In order to achieve direct reduction of molybdenite in presence of a sulphur scavenger such as CaO such that SO{sub 2} emission is completely avoided, it is important to maximise the rate of the partial reaction involving molybdenite and hydrogen (without lime) given the low thermodynamic driving force for this reaction. Accordingly, reaction of molybdenum disulphide powders with hydrogen was investigated by thermogravimetric method. Effect of temperature and concentration on the reaction rate was studied under such conditions that resistance to mass transfer arising from external film, between particles and intra-grain was negligible. The operating temperature ranged between 973 and 1173 K while the hydrogen concentration was varied between 30 and 100%. The experimental data obtained under the above conditions were analyzed by applying 'the shrinking unreacted core model'. The reduction reaction was found to be first order with respect to the gaseous reactant. Pre-exponential factor and activation energy have been determined to be 3.91 x 10{sup 3} cm min{sup -1} and 139.0 kJ mol{sup -1}, respectively. Activation energy obtained from a fitted model, agreed well with the values determined from the model-free methods using isothermal measurements.

  20. Kinetics of oxidation of bilirubin and its protein complex by hydrogen peroxide in aqueous solutions

    Science.gov (United States)

    Solomonov, A. V.; Rumyantsev, E. V.; Antina, E. V.

    2010-12-01

    A comparative study of oxidation reactions of bilirubin and its complex with albumin was carried out in aqueous solutions under the action of hydrogen peroxide and molecular oxygen at different pH values. Free radical oxidation of the pigment in both free and bound forms at pH 7.4 was shown not to lead to the formation of biliverdin, but to be associated with the decomposition of the tetrapyrrole chromophore into monopyrrolic products. The effective and true rate constants of the reactions under study were determined. It was assumed that one possible mechanism of the oxidation reaction is associated with the interaction of peroxyl radicals and protons of the NH groups of bilirubin molecules at the limiting stage with the formation of a highly reactive radical intermediate. The binding of bilirubin with albumin was found to result in a considerable reduction in the rate of the oxidation reaction associated with the kinetic manifestation of the protein protection effect. It was found that the autoxidation of bilirubin by molecular oxygen with the formation of biliverdin at the intermediate stage can be observed with an increase in the pH of solutions.

  1. Correlation between Gas Bubble Formation and Hydrogen Evolution Reaction Kinetics at Nanoelectrodes.

    Science.gov (United States)

    Chen, Qianjin; Luo, Long

    2018-04-17

    We report the correlation between H 2 gas bubble formation potential and hydrogen evolution reaction (HER) activity for Au and Pt nanodisk electrodes (NEs). Microkinetic models were formulated to obtain the HER kinetic information for individual Au and Pt NEs. We found that the rate-determining steps for the HER at Au and Pt NEs were the Volmer step and the Heyrovsky step, respectively. More interestingly, the standard rate constant ( k 0 ) of the rate-determining step was found to vary over 2 orders of magnitude for the same type of NEs. The observed variations indicate the HER activity heterogeneity at the nanoscale. Furthermore, we discovered a linear relationship between bubble formation potential ( E bubble ) and log( k 0 ) with a slope of 125 mV/decade for both Au and Pt NEs. As log ( k 0 ) increases, E bubble shifts linearly to more positive potentials, meaning NEs with higher HER activities form H 2 bubbles at less negative potentials. Our theoretical model suggests that such linear relationship is caused by the similar critical bubble formation condition for Au and Pt NEs with varied sizes. Our results have potential implications for using gas bubble formation to evaluate the HER activity distribution of nanoparticles in an ensemble.

  2. Two-dimensional kinetic model for the evaporation of hydrogen pellets in a tokamak

    International Nuclear Information System (INIS)

    Kuteev, B.V.; Umov, A.P.; Tsendin, L.D.

    1985-01-01

    The problem of the evaporation of a hydrogen fuel pellet in a hot plasma is solved for the case with a Maxwellian electron velocity distribution and a nonuniform evaporation over the surface of the pellet. An expression derived for the evaporation rate N describes this rate within 10% as a function of the temperature, the plasma density, and the pellet radius. The values found for N are only slightly higher than the values calculated in the model of Parks et al. [Nucl. Fusion 17, 539 (1977)], Milora and Foster [IEEE Trans. Plasma Sci. 6, 578, (1978)], and Parks and Turnbull [Phys. Fluids 21, 1735 (1978)]. The reason is a mutual cancellation of some factors ignored in that model: the electron distribution as a function of energy and angle and the nonuniformity of the evaporation. In a kinetic model, the heat flux to the pellet is carried by electrons with an initial energy (6--8)T/sub e/. This circumstance explains why the electric fields have only a weak effect on the evaporation rate near the surface. A refined model is used to calculate the evaporation rates in existing devices

  3. Kinetics of Heterogeneous Reaction of Sulfur Dioxide on Authentic Mineral Dust: Effects of Relative Humidity and Hydrogen Peroxide.

    Science.gov (United States)

    Huang, Liubin; Zhao, Yue; Li, Huan; Chen, Zhongming

    2015-09-15

    Heterogeneous reaction of SO2 on mineral dust seems to be an important sink for SO2. However, kinetic data about this reaction on authentic mineral dust are scarce and are mainly limited to low relative humidity (RH) conditions. In addition, little is known about the role of hydrogen peroxide (H2O2) in this reaction. Here, we investigated the uptake kinetics of SO2 on three authentic mineral dusts (i.e., Asian mineral dust (AMD), Tengger desert dust (TDD), and Arizona test dust (ATD)) in the absence and presence of H2O2 at different RHs using a filter-based flow reactor, and applied a parameter (effectiveness factor) to the estimation of the effective surface area of particles for the calculation of the corrected uptake coefficient (γc). We found that with increasing RH, the γc decreases on AMD particles, but increases on ATD and TDD particles. This discrepancy is probably due to the different mineralogy compositions and aging extents of these dust samples. Furthermore, the presence of H2O2 can promote the uptake of SO2 on mineral dust at different RHs. The probable explanations are that H2O2 rapidly reacts with SO2 on mineral dust in the presence of adsorbed water, and OH radicals, which can be produced from the heterogeneous decomposition of H2O2 on the mineral dust, immediately react with adsorbed SO2 as well. Our results suggest that the removal of SO2 via the heterogeneous reaction on mineral dust is an important sink for SO2 and has the potential to alter the physicochemical properties (e.g., ice nucleation ability) of mineral dust particles in the atmosphere.

  4. Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg2Ni-type Alloy by Melt Spinning

    Directory of Open Access Journals (Sweden)

    Hui-Ping Ren

    2011-01-01

    Full Text Available Mg2Ni-type Mg2Ni1−xCox (x = 0, 0.1, 0.2, 0.3, 0.4 alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD and transmission electron microscopy (TEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1 alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4 alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg2Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s to 30 m/s, the hydrogen absorption saturation ratio ( of the (x = 0.4 alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio ( from 54.5 to 70.2%, the hydrogen diffusion coefficient (D from 0.75 × 10−11 to 3.88 × 10−11 cm2/s and the limiting current density IL from 150.9 to 887.4 mA/g.

  5. Experimental and modeling investigation on structure H hydrate formation kinetics

    International Nuclear Information System (INIS)

    Mazraeno, M. Seyfi; Varaminian, F.; Vafaie sefti, M.

    2013-01-01

    Highlights: • Applying affinity model for the formation kinetics of sH hydrate and two stage kinetics. • Performing the experiments of hydrate formation of sH with MCP. • A unique path for the SH hydrate formation. - Abstract: In this work, the kinetics of crystal H hydrate and two stage kinetics formation is modeled by using the chemical affinity model for the first time. The basic idea is that there is a unique path for each experiment by which the crystallization process decays the affinity. The experiments were performed at constant temperatures of 274.15, 275.15, 275.65, 276.15 and 277.15 K. The initial pressure of each experiment is up to 25 bar above equilibrium pressure of sI. Methylcyclohexane (MCH), methylcyclopentane (MCP) and tert-butyl methyl ether (TBME) are used as sH former and methane is used as a help gas. The parameters of the affinity model (A r and t k ) are determined and the results show that the parameter of (A r )/(RT) has not a constant value when temperature changes in each group of experiments. The results indicate that this model can predict experimental data very well at several conditions

  6. Investigation of Chemical Equilibrium Kinetics by the Electromigration Method

    CERN Document Server

    Bozhikov, G A; Bontchev, G D; Maslov, O D; Milanov, M V; Dmitriev, S N

    2002-01-01

    Measurement of the chemical reaction rates for complex formation as well as hydrolysis type reactions by the method of horizontal zone electrophoresis is outlined. The correlation between chemical equilibrium kinetics and electrodiffusion processes in a constant d.c. electric field is described. In model electromigration experiments the reaction rate constant of the complex formation of Hf(IV) and DTPA is determined.

  7. Kinetic spectrophotometric determination of Bi(III based on its catalytic effect on the oxidation of phenylfluorone by hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    SOFIJA M. RANČIĆ

    2009-08-01

    Full Text Available A new reaction was suggested and a new kinetic method was elaborated for determination of Bi(III in solution, based on its catalytic effect on the oxidation of phenyl-fluorone (PF by hydrogen peroxide in ammonia buffer. By application of spectrophotometric technique, a limit of quantification (LQ of 128 ng cm-3 was reached, and the limit of detection (LD of 37 ng cm-3 was obtained, where LQ was defined as the ratio signal:noise = 10:1 and LD was defined as signal 3:1 against the blank. The RSD value was found to be in the range 2.8–4.8 % for the investigated concentration range of Bi(III. The influence of some ions upon the reaction rate was tested. The method was confirmed by determining Bi(III in a stomach ulcer drug (“Bicit HP”, Hemofarm A.D.. The obtained results were compared to those obtained by AAS and good agreement of results was obtained.

  8. Kinetic investigation of heterogeneous catalytic reactions by means of the kinetic isotope method

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, F; Dermietzel, J [Akademie der Wissenschaften der DDR, Leipzig. Zentralinstitut fuer Isotopen- und Strahlenforschung

    1978-09-01

    The application of the kinetic isotope method to heterogeneous catalytic processes is possible for surface compounds by using the steady-state relation. However, the characterization of intermediate products becomes ambiguous if sorption rates are of the same order of magnitude as surface reactions rates. The isotopic exchange reaction renders possible the estimation of sorption rates.

  9. Superior hydrogen storage kinetics of MgH{sub 2} nanoparticles doped with TiF{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Xie, L. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Liu, Y. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Wang, Y.T. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Zheng, J. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Li, X.G. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China) and College of Engineering, Peking University, Beijing 100871 (China)]. E-mail: xgli@pku.edu.cn

    2007-08-15

    MgH{sub 2} nanoparticles were obtained by hydriding ultrafine magnesium particles which were prepared by hydrogen plasma-metal reaction. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the obtained sample is almost pure MgH{sub 2} phase, without residual magnesium and with an average particle size of {approx}300 nm. Milled with 5 wt.% TiF{sub 3} as a doping precursor in a hydrogen atmosphere, the sample desorbed 4.5 wt.% hydrogen in 6 min under an initial hydrogen pressure of {approx}0.001 bar at 573 K and absorbed 4.2 wt.% hydrogen in 1 min under {approx}20 bar hydrogen at room temperature. Compared with MgH{sub 2} micrometer particles doped with 5 wt.% TiF{sub 3} under the same conditions as the MgH{sub 2} nanoparticles, it is suggested that decrease of particle size is beneficial for enhancing absorption capacity at low temperatures, but has no effect on desorption. In addition, the catalyst was mainly responsible for improving the sorption kinetics and its catalytic mechanism is discussed.

  10. Investigation of nanocrystalline Gd films loaded with hydrogen

    KAUST Repository

    Hruška, Petr; Čí žek, Jakub; Dobroň, Patrik; Anwand, Wolfgang; Mü cklich, Arndt; Gemma, Ryota; Wagner, Stefan; Uchida, Helmut; Pundt, Astrid

    2015-01-01

    The present work reports on microstructure studies of hydrogen-loaded nanocrystalline Gd films prepared by cold cathode beam sputtering on sapphire (112¯0) substrates. The Gd films were electrochemically step-by-step charged with hydrogen and the structural development with increasing concentration of absorbed hydrogen was studied by transmission electron microscopy and in-situ   X-ray diffraction using synchrotron radiation. The relaxation of hydrogen-induced stresses was examined by acoustic emission measurements. In the low concentration range absorbed hydrogen occupies preferentially vacancy-like defects at GBs typical for nanocrystalline films. With increasing hydrogen concentration hydrogen starts to occupy interstitial sites. At the solid solution limit the grains gradually transform into the ββ-phase (GdH2). Finally at high hydrogen concentrations xH>2.0xH>2.0 H/Gd, the film structure becomes almost completely amorphous. Contrary to bulk Gd specimens, the formation of the γγ-phase (GdH3) was not observed in this work.

  11. Investigating Elevated Concentrations of Hydrogen in the LAX region

    Science.gov (United States)

    Rund, P.; Hughes, S.; Blake, D. R.

    2017-12-01

    The growing interest in hydrogen (H2) fuel cell vehicles has created a need to study the atmospheric H2 budget. While there is resounding agreement that hydrogen would escape into the atmosphere due to fuel transport/storage processes, there is disagreement over the amount that would be leaked in a hydrogen fuel economy. Leakage rate estimates range from 2% to 10% for total hydrogen production and transport. A hydrogen based energy infrastructure seems a viable clean alternative to oil because, theoretically, the only waste products are H2O and heat. However, hydrogen leads to the formation of water vapor, polar stratospheric clouds, and a decrease in stratospheric temperatures, which contribute to the depletion of stratospheric ozone. Whole air samples (WAS) collected aboard the NASA Sherpa C-23 during the Student Airborne Research Program (SARP) showed elevated concentrations of hydrogen near LAX (950 ± 110 ppbv) compared to global average concentrations of 560 ± 20 ppbv. Trace gas analysis along with wind trajectories obtained with the NOAA HySPLIT models indicate that the source of elevated mixing ratios was leakage from H2 fuel stations in the surrounding areas. Correlation and ratio analyses eliminate the potential for common photochemical sources of H2 in the LAX area. This project could elucidate new and potential factors that contribute to the global atmospheric hydrogen budget.

  12. Investigation of nickel hydrogen battery technology for the RADARSAT spacecraft

    Science.gov (United States)

    Mccoy, D. A.; Lackner, J. L.

    1986-01-01

    The low Earth orbit (LEO) operations of the RADARSAT spacecraft require high performance batteries to provide energy to the payload and platform during eclipse period. Nickel Hydrogen cells are currently competing with the more traditional Nickel Cadmium cells for high performance spacecraft applications at geostationary Earth orbit (GEO) and Leo. Nickel Hydrogen cells appear better suited for high power applications where high currents and high Depths of Discharge are required. Although a number of GEO missions have flown with Nickel Hydrogen batteries, it is not readily apparent that the LEO version of the Nickel Hydrogen cell is able to withstand the extended cycle lifetime (5 years) of the RADARSAT mission. The problems associated with Nickel Hydrogen cells are discussed in the contex of RADARSAT mission and a test program designed to characterize cell performance is presented.

  13. Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

    Directory of Open Access Journals (Sweden)

    Zun Maria

    2014-12-01

    Full Text Available In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w of urea had the best constancy.

  14. Sum Frequency Generation Vibrational Spectroscopy and Kinetic Study of 2-Methylfuran and 2,5-Dimethylfuran Hydrogenation over 7 nm Platinum Cubic Nanoparticles

    KAUST Repository

    Aliaga, Cesar; Tsung, Chia-Kuang; Alayoglu, Selim; Komvopoulos, Kyriakos; Yang, Peidong; Somorjai, Gabor A.

    2011-01-01

    Sum frequency generation vibrational spectroscopy and kinetic measurements obtained from gas chromatography were used to study the adsorption and hydrogenation of 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) over cubic Pt nanoparticles of 7 nm

  15. Thermodynamic Driving Force of Hydrogen on Rumen Microbial Metabolism: A Theoretical Investigation.

    Science.gov (United States)

    van Lingen, Henk J; Plugge, Caroline M; Fadel, James G; Kebreab, Ermias; Bannink, André; Dijkstra, Jan

    2016-01-01

    Hydrogen is a key product of rumen fermentation and has been suggested to thermodynamically control the production of the various volatile fatty acids (VFA). Previous studies, however, have not accounted for the fact that only thermodynamic near-equilibrium conditions control the magnitude of reaction rate. Furthermore, the role of NAD, which is affected by hydrogen partial pressure (PH2), has often not been considered. The aim of this study was to quantify the control of PH2 on reaction rates of specific fermentation pathways, methanogenesis and NADH oxidation in rumen microbes. The control of PH2 was quantified using the thermodynamic potential factor (FT), which is a dimensionless factor that corrects a predicted kinetic reaction rate for the thermodynamic control exerted. Unity FT was calculated for all glucose fermentation pathways considered, indicating no inhibition of PH2 on the production of a specific type of VFA (e.g., acetate, propionate and butyrate) in the rumen. For NADH oxidation without ferredoxin oxidation, increasing PH2 within the rumen physiological range decreased FT from unity to zero for different NAD+ to NADH ratios and pH of 6.2 and 7.0, which indicates thermodynamic control of PH2. For NADH oxidation with ferredoxin oxidation, increasing PH2 within the rumen physiological range decreased FT from unity at pH of 7.0 only. For the acetate to propionate conversion, FT increased from 0.65 to unity with increasing PH2, which indicates thermodynamic control. For propionate to acetate and butyrate to acetate conversions, FT decreased to zero below the rumen range of PH2, indicating full thermodynamic suppression. For methanogenesis by archaea without cytochromes, FT differed from unity only below the rumen range of PH2, indicating no thermodynamic control. This theoretical investigation shows that thermodynamic control of PH2 on individual VFA produced and associated yield of hydrogen and methane cannot be explained without considering NADH

  16. Thermodynamic Driving Force of Hydrogen on Rumen Microbial Metabolism: A Theoretical Investigation.

    Directory of Open Access Journals (Sweden)

    Henk J van Lingen

    Full Text Available Hydrogen is a key product of rumen fermentation and has been suggested to thermodynamically control the production of the various volatile fatty acids (VFA. Previous studies, however, have not accounted for the fact that only thermodynamic near-equilibrium conditions control the magnitude of reaction rate. Furthermore, the role of NAD, which is affected by hydrogen partial pressure (PH2, has often not been considered. The aim of this study was to quantify the control of PH2 on reaction rates of specific fermentation pathways, methanogenesis and NADH oxidation in rumen microbes. The control of PH2 was quantified using the thermodynamic potential factor (FT, which is a dimensionless factor that corrects a predicted kinetic reaction rate for the thermodynamic control exerted. Unity FT was calculated for all glucose fermentation pathways considered, indicating no inhibition of PH2 on the production of a specific type of VFA (e.g., acetate, propionate and butyrate in the rumen. For NADH oxidation without ferredoxin oxidation, increasing PH2 within the rumen physiological range decreased FT from unity to zero for different NAD+ to NADH ratios and pH of 6.2 and 7.0, which indicates thermodynamic control of PH2. For NADH oxidation with ferredoxin oxidation, increasing PH2 within the rumen physiological range decreased FT from unity at pH of 7.0 only. For the acetate to propionate conversion, FT increased from 0.65 to unity with increasing PH2, which indicates thermodynamic control. For propionate to acetate and butyrate to acetate conversions, FT decreased to zero below the rumen range of PH2, indicating full thermodynamic suppression. For methanogenesis by archaea without cytochromes, FT differed from unity only below the rumen range of PH2, indicating no thermodynamic control. This theoretical investigation shows that thermodynamic control of PH2 on individual VFA produced and associated yield of hydrogen and methane cannot be explained without

  17. Investigation of binary solid phases by calorimetry and kinetic modelling

    OpenAIRE

    Matovic, M.

    2007-01-01

    The traditional methods for the determination of liquid-solid phase diagrams are based on the assumption that the overall equilibrium is established between the phases. However, the result of the crystallization of a liquid mixture will typically be a non-equilibrium or metastable state of the solid. For a proper description of the crystallization process the equilibrium approach is insufficient and a kinetic approach is actually required. In this work, we show that during slow crystallizatio...

  18. Investigations on the heterogenous catalytic hydrogenation using isotope effect and gamma- and neutron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kudlacek, R; Cabicar, J [Ceske Vysoke Uceni Technicke, Prague (Czechoslovakia). Katedra Jaderne Chemie

    1976-01-01

    The kinetic and solvent isotope effects during the maleic acid heterogeneous catalytic hydrogenation and deuteration in light and heavy water have been studied. Also the effect of the gamma and neutron irradiation on the Ni-ZnO catalysts (with various ratios of components) on the reaction kinetics and mechanism has been measured, as well as the effect of pH on the adsorption behaviour of maleic acid and the temperature dependence of the reaction rate. Existence of different adsorption centers for hydrogen and maleic acid could be deduced from these experiments. A reaction mechanism based on the two-dimensional diffusion of components in the surface is proposed. The catalyst is formed from Ni and ZnO-microspheres. Hydrogen is bound to nickel and maleic acid is adsorbed on the ZnO-microspheres. The reaction takes place on the boundary layers of these microspheres.

  19. Investigation related to hydrogen isotopes separation by cryogenic distillation

    International Nuclear Information System (INIS)

    Bornea, A.; Zamfirache, M.; Stefanescu, I.; Preda, A.; Balteanu, O.; Stefan, I.

    2008-01-01

    Research conducted in the last fifty years has shown that one of the most efficient techniques of removing tritium from the heavy water used as moderator and coolant in CANDU reactors (as that operated at Cernavoda (Romania)) is hydrogen cryogenic distillation. Designing and implementing the concept of cryogenic distillation columns require experiments to be conducted as well as computer simulations. Particularly, computer simulations are of great importance when designing and evaluating the performances of a column or a series of columns. Experimental data collected from laboratory work will be used as input for computer simulations run at larger scale (for The Pilot Plant for Tritium and Deuterium Separation) in order to increase the confidence in the simulated results. Studies carried out were focused on the following: - Quantitative analyses of important parameters such as the number of theoretical plates, inlet area, reflux flow, flow-rates extraction, working pressure, etc. - Columns connected in series in such a way to fulfil the separation requirements. Experiments were carried out on a laboratory-scale installation to investigate the performance of contact elements with continuous packing. The packing was manufactured in our institute. (authors)

  20. A Kinetic Platform to Determine the Fate of Hydrogen Peroxide in Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Kristin J Adolfsen

    2015-11-01

    Full Text Available Hydrogen peroxide (H2O2 is used by phagocytic cells of the innate immune response to kill engulfed bacteria. H2O2 diffuses freely into bacteria, where it can wreak havoc on sensitive biomolecules if it is not rapidly detoxified. Accordingly, bacteria have evolved numerous systems to defend themselves against H2O2, and the importance of these systems to pathogenesis has been substantiated by the many bacteria that require them to establish or sustain infections. The kinetic competition for H2O2 within bacteria is complex, which suggests that quantitative models will improve interpretation and prediction of network behavior. To date, such models have been of limited scope, and this inspired us to construct a quantitative, systems-level model of H2O2 detoxification in Escherichia coli that includes detoxification enzymes, H2O2-dependent transcriptional regulation, enzyme degradation, the Fenton reaction and damage caused by •OH, oxidation of biomolecules by H2O2, and repair processes. After using an iterative computational and experimental procedure to train the model, we leveraged it to predict how H2O2 detoxification would change in response to an environmental perturbation that pathogens encounter within host phagosomes, carbon source deprivation, which leads to translational inhibition and limited availability of NADH. We found that the model accurately predicted that NADH depletion would delay clearance at low H2O2 concentrations and that detoxification at higher concentrations would resemble that of carbon-replete conditions. These results suggest that protein synthesis during bolus H2O2 stress does not affect clearance dynamics and that access to catabolites only matters at low H2O2 concentrations. We anticipate that this model will serve as a computational tool for the quantitative exploration and dissection of oxidative stress in bacteria, and that the model and methods used to develop it will provide important templates for the

  1. Investigation of low emission combustors using hydrogen lean direct injection

    Directory of Open Access Journals (Sweden)

    Robert ISAC

    2011-09-01

    Full Text Available One of the key technology challenges for the use of hydrogen in gas turbine engines is the performance of the combustion system, in particular the fuel injectors. Tests were conducted to measure the nitrogen oxide (NOx emissions and combustion performance at inlet conditions of 588 to 811 K, 0.4 to 1.4 MPa, and equivalence ratios up to 0.48. All the injectors were based on Lean Direct Injection (LDI technology with multiple injection points and quick mixing. One challenge to hydrogen-based premixing combustion systems is flashback since hydrogen has a reaction rate over 7 times that of Jet-A.

  2. Surface properties of hydrogenated nanodiamonds: a chemical investigation.

    Science.gov (United States)

    Girard, H A; Petit, T; Perruchas, S; Gacoin, T; Gesset, C; Arnault, J C; Bergonzo, P

    2011-06-28

    Hydrogen terminations (C-H) confer to diamond layers specific surface properties such as a negative electron affinity and a superficial conductive layer, opening the way to specific functionalization routes. For example, efficient covalent bonding of diazonium salts or of alkene moieties can be performed on hydrogenated diamond thin films, owing to electronic exchanges at the interface. Here, we report on the chemical reactivity of fully hydrogenated High Pressure High Temperature (HPHT) nanodiamonds (H-NDs) towards such grafting, with respect to the reactivity of as-received NDs. Chemical characterizations such as FTIR, XPS analysis and Zeta potential measurements reveal a clear selectivity of such couplings on H-NDs, suggesting that C-H related surface properties remain dominant even on particles at the nanoscale. These results on hydrogenated NDs open up the route to a broad range of new functionalizations for innovative NDs applications development. This journal is © the Owner Societies 2011

  3. Investigation of cadmium(2) electrolytic reduction kinetics from α-aminoacetic solutions

    International Nuclear Information System (INIS)

    Nikitenko, V.N.; Litovchenko, K.I.; Kublanovskij, V.S.

    1980-01-01

    Kinetics and reduction mechanism of cadmium(2) reduction from α-amino acetic solutions is studied. It is shown that glycine and hydrogen ions take part directly in the electrode reaction of cadmium (2) reduction from α-amino acetic solutions. It is established that complex ion of the composition CdCl + is electroactive forM of the substance, which takes part in the transfer reaction. The rate of electrode process is limited with reduced ion supply to the electrode surface

  4. Hydrogen absorption kinetics of niobium with an ion-plated nickel overlayer

    International Nuclear Information System (INIS)

    Nakamura, K.

    1981-01-01

    The hydrogen absorption rate for nickel-ion-plated niobium was measured as a function of hydrogen pressure and temperature. The observed absorption curves of c(mean)/csub(e) against time (c(mean) and csub(e) are the mean and equilibrium hydrogen concentrations respectively) exhibited a marked hydrogen pressure dependence below 628 K but this was less marked above 723 K. The results were analysed on the basis of the proposed model that the rate-determining step is the hydrogen permeation through the nickel overlayer and that the permeation is driven by the hydrogen activity difference between the two interfaces, namely the H 2 -Ni and Ni-Nb interfaces. The marked pressure dependence can be attributed to the fact that the hydrogen activity coefficient in nickel is constant and that in niobium it varies markedly with concentration, i.e. with hydrogen pressure and temperature. It was also found that the change in the nickel overlayer structure caused by the dilatation of bulk niobium during hydrogen absorption enhances the hydrogen absorption rates. The temperature dependence of the hydrogen absorption rate is also discussed in comparison with that for tantalum with a vacuum-deposited nickel overlayer. (Auth.)

  5. Carbon Dioxide Hydrogenation into Higher Hydrocarbons and Oxygenates: Thermodynamic and Kinetic Bounds and Progress with Heterogeneous and Homogeneous Catalysis.

    Science.gov (United States)

    Prieto, Gonzalo

    2017-03-22

    Under specific scenarios, the catalytic hydrogenation of CO 2 with renewable hydrogen is considered a suitable route for the chemical recycling of this environmentally harmful and chemically refractory molecule into added-value energy carriers and chemicals. The hydrogenation of CO 2 into C 1 products, such as methane and methanol, can be achieved with high selectivities towards the corresponding hydrogenation product. More challenging, however, is the selective production of high (C 2+ ) hydrocarbons and oxygenates. These products are desired as energy vectors, owing to their higher volumetric energy density and compatibility with the current fuel infrastructure than C 1 compounds, and as entry platform chemicals for existing value chains. The major challenge is the optimal integration of catalytic functionalities for both reductive and chain-growth steps. This Minireview summarizes the progress achieved towards the hydrogenation of CO 2 to C 2+ hydrocarbons and oxygenates, covering both solid and molecular catalysts and processes in the gas and liquid phases. Mechanistic aspects are discussed with emphasis on intrinsic kinetic limitations, in some cases inevitably linked to thermodynamic bounds through the concomitant reverse water-gas-shift reaction, which should be considered in the development of advanced catalysts and processes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Study on the effects of titanium oxide based nanomaterials as catalysts on the hydrogen sorption kinetics of magnesium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Anderson de Farias; Jardim, Paula Mendes; Santos, Dilson Silva dos, E-mail: anderso.n@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Conceicao, Monique Osorio Talarico da [Centro Universitario de Volta Redonda (UniFOA), RJ (Brazil)

    2016-07-01

    Full text: Magnesium hydride is highly attractive for hydrogen storage in solid state in reason of its high gravimetric capacity (7,6 wt% of H{sub 2}) and low density (1,7 g/cm³), making it a promissory candidate for mobile applications [1]. However, its low sorption kinetics and desorption temperature are the main obstacles for its application. In the present study the catalytic role of TiO{sub 2} based nanomaterials with different morphologies on the sorption kinetics of MgH{sub 2} was evaluated. The additions consisted on titanate nanotubes (TTNT-Low), TiO{sub 2} nanorods (TTNT-550) and nanoparticles (KA-100, TTNT-ACID). Transmission and Scanning Transmission Electron Microscopy (S/TEM) associated with X-ray Energy Dispersive Spectroscopy (XEDS) mapping was used to characterize the catalysts' morphology and crystalline structure and their dispersion within magnesium hydride, altogether with other characterization techniques such as X-ray diffraction (XRD) and BET technique for structure and surface area analysis. The sorption kinetics were evaluated by means of a volumetric gas absorption/desorption (Sievert-type) apparatus. The results indicated that all additives improved the sorption kinetics of MgH{sub 2}, but the samples with TTNT-550 (TiO{sub 2} nanorods) and TTNT-ACID (TiO{sub 2} nanoparticles) presented the best and the second best performances, respectively, suggesting that the 1D morphology may promote a slightly superior kinetics than particulate catalysts. (author)

  7. Study of hydrogen mobility by hydrogen-deuterium exchange. II. Theoretical kinetic study in alkyl and amino-alkyl pyrimidines

    International Nuclear Information System (INIS)

    Pompon, Alain

    1975-01-01

    Alkyl groups bound to the pyrimidine ring can be deuterium substituted on the carbon adjacent to the ring, in acidic D 2 O; kinetic equations corresponding to various exchange mechanism hypothesis are established. It is shown that theoretical and experimental results can be compared in order to precise the mechanism and to measure the characteristic parameters of the exchange reaction [fr

  8. Hydrogen-Induced Adsorption of Carbon Monoxide on the Gold Dimer Cation: A Joint Experimental and DFT Investigation.

    Science.gov (United States)

    Vojkovic, Marin; Rayane, Driss; Antoine, Rodolphe; Broyer, Michel; Allouche, Abdul-Rahman; Mignon, Pierre; Dugourd, Philippe

    2017-06-15

    It is demonstrated, using tandem mass spectrometry and radio frequency ion trap, that the adsorption of a H atom on the gold dimer cation, Au 2 H + , prevents its dissociation and allows for adsorption of CO. Reaction kinetics are measured by employing a radio frequency ion trap, where Au 2 + and CO interact for a given reaction time. The effect of a hydrogen atom is evaluated by comparing reaction rate constants measured for Au 2 + and Au 2 H + . The theoretical results for the adsorption of CO molecules and their reaction characteristics with Au 2 + and Au 2 H + are found to agree with the experimental findings. The joint investigations provide insights into hydrogen atom adsorption effects and consequent reaction mechanisms.

  9. Investigation of hydrogen-deformation interactions in β-21S titanium alloy using thermal desorption spectroscopy

    International Nuclear Information System (INIS)

    Tal-Gutelmacher, E.; Eliezer, D.; Boellinghaus, Th.

    2007-01-01

    The focus of this paper is the investigation of the combined influence of hydrogen and pre-plastic deformation on hydrogen's absorption/desorption behavior, the microstructure and microhardness of a single-phased β-21S alloy. In this study, thermal desorption analyses (TDS) evaluation of various desorption and trapping parameters provide further insight on the relationships between hydrogen absorption/desorption processes and deformation, and their mutual influence on the microstructure and the microhardness of β-21S alloy. TDS spectra were supported by other experimental techniques, such as X-ray diffraction, scanning and transmission electron microscopy, hydrogen quantity analyses and microhardness tests. Pre-plastic deformation, performed before the electrochemical hydrogenation of the alloy, increased significantly the hydrogen absorption capacity. Its influence was also evident on the notably expanded lattice parameter of β-21S alloy after hydrogenation. However, no hydride precipitation was observed. An interesting softening effect of the pre-deformed hydrogenated alloy was revealed by microhardness tests. TDS demonstrated the significant effect of pre-plastic deformation on the hydrogen evolution process. Hydrogen desorption temperature and the activation energy for hydrogen release increased, additional trap states were observed and the amount of desorbed hydrogen decreased

  10. Investigate of analysis for hydrogen contents in carbon films

    International Nuclear Information System (INIS)

    Yasui, Haruyuki; Hirose, Yukio; Sasaki, Toshihiko; Awazu, Kaoru; Naramoto, Hiroshi

    2001-01-01

    Hydrogen is a very common contaminant in carbon films. It can strongly influences on mechanical, physical and chemical properties of the films. The analysis of hydrogen is therefore a crucial problem to prepare the films with the reproducible property. We were measured two kinds of methods. Ion beam techniques using nuclear reactions are established methods for the quantitative determination of hydrogen concentration. A spectrometer has been constructed for the determination of hydrogen concentrations by detecting 4.43 MeV γ-rays from the resonant nuclear reactions 1 H( 15 N, α γ) 12 C at the 6.385 MeV. And the other measurement of hydrogen is GDOES (Glow Discharge Optical Emission Spectroscopy), with its high sputtering rates, had been used previously for depth profiling analysis of thin films. The depth profiling analysis was carried out at an argon atmosphere by applying an RF of 13.56 MHz. The sampling time interval was 0.1 sec. The detailed hydrogen analysis was made on BCN (Boron Carbonitride) and DLC (Diamond-like Carbon) thin films. The BCN films were prepared by ion beam assisted deposition, in which boron and carbon were deposited by electron beam heating of B 4 C solid and nitrogen was supplied by implantation simultaneously. The DLC films were prepared by HPPC (Hybrid-pulse plasma coating) system. It was a new coating system that we developed which consists fundamentally of plasma CVD (chemical vapor deposition) and ion-mixing. In this paper, we reported the comparison of analysis for hydrogen contents between RNRA and GDOES. (author)

  11. Investigate of analysis for hydrogen contents in carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Yasui, Haruyuki; Hirose, Yukio; Sasaki, Toshihiko [Kanazawa Univ., Kanazawa, Ishikawa (Japan); Awazu, Kaoru [Industrial Research Institute of Ishikawa, Kanazawa, Ishikawa (Japan); Naramoto, Hiroshi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    2001-07-01

    Hydrogen is a very common contaminant in carbon films. It can strongly influences on mechanical, physical and chemical properties of the films. The analysis of hydrogen is therefore a crucial problem to prepare the films with the reproducible property. We were measured two kinds of methods. Ion beam techniques using nuclear reactions are established methods for the quantitative determination of hydrogen concentration. A spectrometer has been constructed for the determination of hydrogen concentrations by detecting 4.43 MeV {gamma}-rays from the resonant nuclear reactions {sup 1}H({sup 15}N, {alpha} {gamma}){sup 12}C at the 6.385 MeV. And the other measurement of hydrogen is GDOES (Glow Discharge Optical Emission Spectroscopy), with its high sputtering rates, had been used previously for depth profiling analysis of thin films. The depth profiling analysis was carried out at an argon atmosphere by applying an RF of 13.56 MHz. The sampling time interval was 0.1 sec. The detailed hydrogen analysis was made on BCN (Boron Carbonitride) and DLC (Diamond-like Carbon) thin films. The BCN films were prepared by ion beam assisted deposition, in which boron and carbon were deposited by electron beam heating of B{sub 4}C solid and nitrogen was supplied by implantation simultaneously. The DLC films were prepared by HPPC (Hybrid-pulse plasma coating) system. It was a new coating system that we developed which consists fundamentally of plasma CVD (chemical vapor deposition) and ion-mixing. In this paper, we reported the comparison of analysis for hydrogen contents between RNRA and GDOES. (author)

  12. An investigation of a household size trigeneration running with hydrogen

    International Nuclear Information System (INIS)

    Wang, Yaodong; Huang, Ye; Chiremba, Elijah; Roskilly, Anthony P.; Hewitt, Neil; Ding, Yulong; Wu, Dawei; Yu, Hongdong; Chen, Xiangping; Li, Yapeng; Huang, Jincheng; Wang, Ruzhu; Wu, Jingyi; Xia, Zaizhong; Tan, Chunqing

    2011-01-01

    This study examined the performance and emission characteristics of a household size trigeneration based on a diesel engine generator fuelled with hydrogen comparing to that of single generation, cogeneration using ECLIPSE simulation software. In single generation simulation, the engine genset is used to produce electricity only and the heat from the engine is rejected to the atmosphere. In cogeneration and trigeneration, in addition to the electricity generated from the genset, the waste heat rejected from the hot exhaust gases and engine cooling system, is captured for domestic hot water supply using heat exchangers and hot water tank; and a part of the waste heat is used to drive absorption cooling in trigeneration. Comparisons have been made for the simulated results of these three modes of operation for hydrogen and diesel. The results prove that hydrogen is a potential energy vector in the future which is a key to meeting upcoming stringent greenhouse gases emissions. The study show that hydrogen has very good prospects to achieve a better or equal performance to conventional diesel fuel in terms of energetic performance, and a near zero carbon emission, depending on the life cycle analysis of the way the hydrogen is produced. The results also show enormous potential fuel savings and massive reductions in greenhouse gas emissions per unit of useful energy outputs with cogeneration and trigeneration compared with that of single generation.

  13. Gas-Phase Hydrogen-Deuterium Exchange Labeling of Select Peptide Ion Conformer Types: a Per-Residue Kinetics Analysis.

    Science.gov (United States)

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Tafreshian, Amirmahdi; Valentine, Stephen J

    2015-07-01

    The per-residue, gas-phase hydrogen deuterium exchange (HDX) kinetics for individual amino acid residues on selected ion conformer types of the model peptide KKDDDDDIIKIIK have been examined using ion mobility spectrometry (IMS) and HDX-tandem mass spectrometry (MS/MS) techniques. The [M + 4H](4+) ions exhibit two major conformer types with collision cross sections of 418 Å(2) and 446 Å(2); the [M + 3H](3+) ions also yield two different conformer types having collision cross sections of 340 Å(2) and 367 Å(2). Kinetics plots of HDX for individual amino acid residues reveal fast- and slow-exchanging hydrogens. The contributions of each amino acid residue to the overall conformer type rate constant have been estimated. For this peptide, N- and C-terminal K residues exhibit the greatest contributions for all ion conformer types. Interior D and I residues show decreased contributions. Several charge state trends are observed. On average, the D residues of the [M + 3H](3+) ions show faster HDX rate contributions compared with [M + 4H](4+) ions. In contrast the interior I8 and I9 residues show increased accessibility to exchange for the more elongated [M + 4H](4+) ion conformer type. The contribution of each residue to the overall uptake rate showed a good correlation with a residue hydrogen accessibility score model calculated using a distance from charge site and initial incorporation site for nominal structures obtained from molecular dynamic simulations (MDS).

  14. Investigations into the process kinetics of immobilized microorganisms

    Energy Technology Data Exchange (ETDEWEB)

    Voss, H; Geipel, F

    1987-01-01

    The authors present a population-structured process model of ethanol production by S. cerevisiae cells fixed in Ca alginate. Experiments were made in discontinuous and continuous fluidized-bed reactors. Living cells, both reproductive and non-reproductive, are distinguished from dead cells in the segregated reactor model. The rates of cell state change are described as a function of the ethanol concentration. The growth rate is described by a Monod model extended by inhibition functions and supplemented by a cell inhibition function. Product formation comprises a growth-associated component and a non-associated component resulting from the endogenous and maintenance metabolism. Further, a cell discharge rate from the gel is considered which is dependent both on growth and on the biomass concentration. The simulation of process kinetics and reactor dynamics with an optimum parameter vector shows an excellent adaptation for all experiments.

  15. Investigation of chemical equilibrium kinetics by the electromigration method

    International Nuclear Information System (INIS)

    Bozhikov, G.A.; Ivanov, P.I.; Maslov, O.D.; Dmitriev, S.N.; Bontchev, G.D.; Milanov, M.V.

    2003-01-01

    The measurement of the chemical reaction rates for complex formation as well as hydrolysis type reactions by the method of horizontal zone electrophoresis is outlined. The correlation between chemical equilibrium kinetics and electrodiffusion processes in a constant d.c. electric field is described. In model electromigration experiments the reaction rate constant of the formation a complex by Hf(IV) and diethylenetriaminepentaacetic acid (DTPA) is determined. The electrophoretic mobility, diffusion coefficient and stability constant of the [HfDTPA] - complex are calculated, taking into account experimental electrophoretic data obtained at 298.15±0.05 K and constant ionic strength. No-carrier-added 175 Hf radionuclide was used in electromigration experiments at concentrations of 10 -10 -10 -11 M. (orig.)

  16. Kinetic modeling study of homogeneous ignition of dimethyl ether/hydrogen and dimethyl ether/methane

    International Nuclear Information System (INIS)

    Wang, Ying; Liu, Hong; Ke, Xichun; Shen, Zhenxing

    2017-01-01

    Highlights: • Kinetic effects on the homogeneous ignitions of DME/H_2 and DME/CH_4 were studied. • Ignition delays with different DME blending ratio were determined and analyzed. • Different DME ignition combustion trends are found for H_2 and CH_4 addition. • Key elementary reactions are identified at different DME ratios and temperatures. - Abstract: Homogeneous ignition combustion of different proportion DME/H_2 and DME/CH_4 blend fuels in the air is investigated through the numerical simulation with the detailed chemistry at the low and high temperatures in this paper. The emphasis is the assessment of the kinetic effects involved in the ignition combustion of DME/H_2 and DME/CH_4 dual-fuel. It is found that the homogeneous ignition process has a clear distinction at the different temperatures. At the low temperature (900 K), the ignition delay times of DME/H_2 blends and DME/CH_4 blends both show an increase with a decrease of the DME blending ratio; furthermore, it is observed that CH_4 addition is more effective than H_2 addition in terms of delaying the DME homogeneous ignition due to the stable molecular structure of CH_4. At the high temperature (1400 K), with the decrease of DME blending ratio, the ignition delay time of DME/CH_4 blends is still increased, whereas, the ignition delay time of DME/H_2 blends is shortened. Sensitivity analysis, reaction path analysis and main pollutant species calculation are carried out and key elementary reactions involved in homogeneous ignition of DME/H_2 and DME/CH_4 dual fuel are also identified in this paper.

  17. The kinetic and mechanical aspects of hydrogen-induced failure in metals. Ph.D. Thesis, 1971

    Science.gov (United States)

    Nelson, H. G.

    1972-01-01

    Premature hydrogen-induced failure observed to occur in many metal systems involves three stages of fracture: (1) crack initiation, (2) stable slow crack growth, and (3) unstable rapid crack growth. The presence of hydrogen at some critical location on the metal surface or within the metal lattice was shown to influence one or both of the first two stages of brittle fracture but has a negligible effect on the unstable rapid crack growth stage. The relative influence of the applied parameters of time, temperature, etc., on the propensity of a metal to exhibit hydrogen induced premature failure was investigated.

  18. Investigation of coupling between chemistry and discharge dynamics in radio frequency hydrogen plasmas in the Torr regime

    International Nuclear Information System (INIS)

    Kalache, B; Novikova, T; Morral, A Fontcuberta i; Cabarrocas, P Roca i; Morscheidt, W; Hassouni, K

    2004-01-01

    We present the results of a study of a capacitively coupled hydrogen discharge by means of a one-dimensional numerical fluid model and experiments. The model includes a detailed description of the gas-phase chemistry taking into account the production of H - ions by dissociative attachment of H 2 vibrational levels. The population of these levels is described by a Boltzmann vibrational distribution function characterized by a vibrational temperature T V . The effect of the dissociative-attachment reaction on the discharge dynamics was investigated by varying the vibrational temperature, which was used as a model input parameter. Increasing the vibrational temperature from 1000 to 6000 K affects both the chemistry and the dynamics of the electrical discharge. Because of dissociative attachment, the H - ion density increases by seven orders of magnitude and the H - ion density to electron density ratio varies from 10 -7 to 6, while the positive ion density increases slightly. As a consequence, the atomic hydrogen density increases by a factor of three, and the sheath voltage drops from 95 to 75 V. Therefore, clear evidence of a strong coupling between chemistry and electrical dynamics through the production of H - ions is demonstrated. Moreover, satisfactory agreement between computed and measured values of atomic hydrogen and H - ion densities gives further support to the requirement of a detailed description of the hydrogen vibrational kinetics for capacitively coupled radio frequency discharge models in the Torr regime

  19. Heavy fuel oil pyrolysis and combustion: kinetics and evolved gases investigated by TGA-FTIR

    KAUST Repository

    Abdul Jameel, Abdul Gani; Han, Yunqing; Brignoli, Omar; Telalovic, Selvedin; Elbaz, Ayman M.; Im, Hong G.; Roberts, William L.; Sarathy, Mani

    2017-01-01

    investigated using non-isothermal thermo-gravimetric analysis (TGA) coupled with a Fourier-transform infrared (FTIR) spectrometer. TG and DTG (differential thermo-gravimetry) were used for the kinetic analysis and to study the mass loss characteristics due

  20. Kinetics of Oxidation of Cobalt(III Complexes of a Acids by Hydrogen Peroxide in the Presence of Surfactants

    Directory of Open Access Journals (Sweden)

    Mansur Ahmed

    2008-01-01

    Full Text Available Hydrogen peroxide oxidation of pentaamminecobalt(III complexes of α-hydroxy acids at 35°C in micellar medium has been attempted. In this reaction the rate of oxidation shows first order kinetics each in [cobalt(III] and [H2O2]. Hydrogen peroxide induced electron transfer in [(NH35 CoIII-L]2+ complexes of α-hydroxy acids readily yields 100% of cobalt(II with nearly 100% of C-C bond cleavage products suggesting that it behaves mainly as one equivalent oxidant in micellar medium. With unbound ligand also it behaves only as C-C cleavage agent rather than C-H cleavage agent. With increasing micellar concentration an increase in the rate is observed.

  1. Site-Specific Hydrogen Isotope Composition of Propane: Mass spectrometric methods, equilibrium temperature dependence, and kinetics of exchange

    Science.gov (United States)

    Xie, H.; Ponton, C.; Kitchen, N.; Lloyd, M. K.; Lawson, M.; Formolo, M. J.; Eiler, J. M.

    2016-12-01

    Intramolecular isotope ordering can constrain temperatures of synthesis, mechanisms of formation, and/or source substrates of organic compounds. Here we explore site-specific hydrogen isotope variations of propane. Statistical thermodynamic models predict that at equilibrium methylene hydrogen (-CH2-) in propane will be 10's of per mil higher in D/H ratio than methyl hydrogen (-CH3) at geologically relevant temperatures, and that this difference is highly temperature dependent ( 0.5-1 ‰/°C). Chemical-kinetic controls on site-specific D/H in propane could constrain the mechanisms, conditions and extents of propane synthesis or destruction. We have developed a method for measuring the difference in D/H ratio between methylene and methyl hydrogen in propane by gas source mass spectrometry. The data were measured using the Thermo Fisher Double Focusing Sector high resolution mass spectrometer (DFS), and involve comparison of the D/H ratios of molecular ion (C3H8+) and the ethyl fragmental ion (C2H5+). We demonstrate the accuracy and precision of this method through analysis of D-labeled and independently analyzed propanes. In the exchange experiments, propane was heated (100-200 oC) either alone or in the presence of D-enriched water (δD=1,1419 ‰ SMOW), with or without one of several potentially catalytic substrates for hours to weeks. Propane was found to exchange hydrogen with water vigorously at 200 °C in the presence of metal catalysts. In the presence of Ni catalyst, methylene hydrogen exchanges 2.5 times faster than methyl hydrogen. Hydrogen exchange in the presence of Pd catalyst is more effective and can equilibrate hydrogen isotope distribution on propane on the order of 7 days. Isotopic exchange in the presence of natural materials have also been tested, but is only measurable in the methylene group at 200 °C. High catalytic activity of Pd permits attainment of a bracketed, time-invariant equilibrium state that we use to calibrate the site

  2. Growth kinetics of hydrogen sulfide oxidizing bacteria in corroded concrete from sewers

    International Nuclear Information System (INIS)

    Jensen, Henriette Stokbro; Lens, Piet N.L.; Nielsen, Jeppe L.; Bester, Kai; Nielsen, Asbjorn Haaning; Hvitved-Jacobsen, Thorkild; Vollertsen, Jes

    2011-01-01

    Hydrogen sulfide oxidation by microbes present on concrete surfaces of sewer pipes is a key process in sewer corrosion. The growth of aerobic sulfur oxidizing bacteria from corroded concrete surfaces was studied in a batch reactor. Samples of corrosion products, containing sulfur oxidizing bacteria, were suspended in aqueous solution at pH similar to that of corroded concrete. Hydrogen sulfide was supplied to the reactor to provide the source of reduced sulfur. The removal of hydrogen sulfide and oxygen was monitored. The utilization rates of both hydrogen sulfide and oxygen suggested exponential bacterial growth with median growth rates of 1.25 d -1 and 1.33 d -1 as determined from the utilization rates of hydrogen sulfide and oxygen, respectively. Elemental sulfur was found to be the immediate product of the hydrogen sulfide oxidation. When exponential growth had been achieved, the addition of hydrogen sulfide was terminated leading to elemental sulfur oxidation. The ratio of consumed sulfur to consumed oxygen suggested that sulfuric acid was the ultimate oxidation product. To the knowledge of the authors, this is the first study to determine the growth rate of bacteria involved in concrete corrosion with hydrogen sulfide as source of reduced sulfur.

  3. Improvement of hydrogen storage kinetics in ball-milled magnesium doped with antimony

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jiří; Král, Lubomír; Roupcová, Pavla

    2017-01-01

    Roč. 42, č. 9 (2017), s. 6144-6151 ISSN 0360-3199 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Hydrogen * Hydrogen storage * Storage capacity * Magnesium alloys * Antimony Subject RIV: JJ - Other Materials OBOR OECD: Materials engineering Impact factor: 3.582, year: 2016

  4. Merging Iron Catalysis and Biocatalysis-Iron Carbonyl Complexes as Efficient Hydrogen Autotransfer Catalysts in Dynamic Kinetic Resolutions

    KAUST Repository

    El-Sepelgy, Osama

    2016-09-29

    A dual catalytic iron/lipase system has been developed and applied in the dynamic kinetic resolution of benzylic and aliphatic secondary alcohols. A detailed study of the Knölker-type iron complexes demonstrated the hydrogen autotransfer of alcohols to proceed under mild reaction conditions and allowed the combination with the enzymatic resolution. Different racemic alcohols were efficiently converted to chiral acetates in good yields and with excellent enantioselectivities. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  5. Molecular projectile effects for kinetic electron emission from carbon- and metal-surfaces bombarded by slow hydrogen ions

    Science.gov (United States)

    Cernusca, S.; Winter, HP.; Aumayr, F.; Díez Muiño, R.; Juaristi, J. I.

    2003-04-01

    Total yields for kinetic electron emission (KE) have been determined for impact of hydrogen monomer-, dimer- and trimer-ions (impact energy armour in magnetic fusion devices. The data are compared with KE yields for impact of same projectile ions on atomically clean highly oriented pyrolytic graphite and polycrystalline gold. We discuss KE yields for the different targets if bombarded by equally fast molecular and atomic ions in view to "projectile molecular effects" (different yields per proton for equally fast atomic and molecular ions), which are expected from calculated electronic projectile energy losses in these target materials.

  6. Merging Iron Catalysis and Biocatalysis-Iron Carbonyl Complexes as Efficient Hydrogen Autotransfer Catalysts in Dynamic Kinetic Resolutions

    KAUST Repository

    El-Sepelgy, Osama; Alandini, Nurtalya; Rueping, Magnus

    2016-01-01

    A dual catalytic iron/lipase system has been developed and applied in the dynamic kinetic resolution of benzylic and aliphatic secondary alcohols. A detailed study of the Knölker-type iron complexes demonstrated the hydrogen autotransfer of alcohols to proceed under mild reaction conditions and allowed the combination with the enzymatic resolution. Different racemic alcohols were efficiently converted to chiral acetates in good yields and with excellent enantioselectivities. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  7. Investigation of electro-kinetic methods for soil decontamination

    International Nuclear Information System (INIS)

    Shabanova, A.N.

    2000-01-01

    The choices of effective methods for ecological system decontamination, their perfection and introduction into practical use have been actual tasks for the Ural region. The objective of this work has been to study the potentials of electrical kinetics method of ISOTRON Corporation (US) for decontamination of the Urals soils. Results obtained have shown the method proposed to be usable for decontaminating some types of soils from strontium and plutonium; it is low effective for decontamination in the area of South-Urals radioactive plume. Thus, a low effectiveness can be expected in podsolic and leached laterite characterized by a high content of loamy sand and sandy soils, as well as for sobby-podsolic ones. The method can be promising for decontamination of soils and wastes from chemical contaminants, such as Zn, Ni, Cu, Pb, Hg, and others. Important advantages of this method compared to others have been its simplicity, small amount of wastes, and feasibility of decontamination in areas difficult to access. (authors)

  8. Kinetic investigation of uranyl-uranophile complexation. 1. Macrocyclic kinetic effect and macrocyclic protection effect

    International Nuclear Information System (INIS)

    Tabushi, I.; Yoshizawa, A.

    1986-01-01

    Equilibria and rates of ligand-exchange reactions between uranyl tricarbonate and dithiocarbamates and between uranyl tris-(dithiocarbamates) and carbonate were studied under a variety of conditions. The dithiocarbamates used were acyclic diethyl-dithiocarbamate and macrocyclic tris(dithiocarbamate). The acyclic ligand showed a triphasic (successive three-step) equilibrium with three different equilibrium constants while the macrocyclic ligand showed a clear monophasic (one-step) equilibrium with a much larger stability constant for the dithiocarbamate-uranyl complex. The macrocyclic ligand showed the S/sub N/2-type ligand-exchange rate in the forward as well as reverse process, while the first step of the acyclic ligand-exchange reaction proceeded via the S/sub N/1-type mechanism. This kinetic macrocyclic effect on molecularity is interpreted as the result of a unique topological requirement of uranyl complexation. The macrocyclic ligand also exhibited a clear protection effect, leading to the large stability constant. 19 references, 10 figures, 2 tables

  9. Kinetic investigations of quinoline oxidation by ferrate(VI).

    Science.gov (United States)

    Luo, Zhiyong; Li, Xueming; Zhai, Jun

    2016-01-01

    Quinoline is considered as one of the most toxic and carcinogenic compounds and is commonly found in industrial wastewaters, which require treatment before being discharged. Removal of quinoline by the use of an environmentally friendly oxidant, potassium ferrate(VI) (K2FeO4), was assessed by studying the kinetics of the oxidation of quinoline by ferrate(VI) (Fe(VI)) as a function of pH (8.53-10.53) and temperature (21-36°C) in this work. The reaction of quinoline with Fe(VI) was found to be first order in Fe(VI), half order in quinoline, and 1.5 order overall. The observed rate constant at 28°C decreased non-linearly from 0.5334 to 0.2365 M(-0.5) min(-1) with an increase in pH from 8.53 to 10.03. Considering the equilibria of Fe(VI) and quinoline, the reaction between quinoline and Fe(VI) contained two parallel reactions under the given pH conditions. The individual rate constants of these two reactions were determined. The results indicate that the protonated species of Fe(VI) reacts more quickly with quinoline than the deprotonated form of Fe(VI). The reaction activation energy Ea was obtained to be 51.44 kJ·mol(-1), and it was slightly lower than that of conventional chemical reaction. It reveals that the oxidation of quinoline by Fe(VI) is feasible in the routine water treatment.

  10. Kinetics on NiZn Bimetallic Catalysts for Hydrogen Evolution via Selective Dehydrogenation of Methylcyclohexane to Toluene

    KAUST Repository

    Shaikh Ali, Anaam

    2017-01-18

    Liquid organic chemical hydrides are effective hydrogen storage media for easy and safe transport. The chemical couple of methylcyclohexane (MCH) and toluene (TOL) has been considered one of the feasible cycles for a hydrogen carrier, but the selective dehydrogenation of MCH to TOL has been reported using only Pt-based noble metal catalysts. This study reports MCH dehydrogenation to TOL using supported NiZn as a selective, non-noble-metal catalyst. A combined experimental and computational study was conducted to provide insight into the site requirements and reaction mechanism for MCH dehydrogenation to TOL, which were compared with those for cyclohexane (CH) dehydrogenation to benzene (BZ). The kinetic measurements carried out at 300-360°C showed an almost zero order with respect to MCH pressure in the high-pressure region (≥10 kPa) and nearly a positive half order with respective to H pressure (≤40 kPa). These kinetic data for the dehydrogenation reaction paradoxically indicate that hydrogenation of a strongly chemisorbed intermediate originating from TOL is the rate-determining step. Density functional theory (DFT) calculation confirms that the dehydrogenated TOL species at the aliphatic (methyl) position group (CHCH) were strongly adsorbed on the surface, which must be hydrogenated to desorb as TOL. This hydrogen-assisted desorption mechanism explains the essential role of excess H present in the feed in maintaining the activity of the metallic surface for hydrogenation. The rate of the CH to BZ reaction was less sensitive to H pressure than that of MCH to TOL, which can be explained by the absence of a methyl group in the structure, which in turn reduces the binding energy of the adsorbed species. DFT suggests that the improved TOL selectivity by adding Zn to Ni was due to Zn atoms preferentially occupying low-coordination sites on the surface (the corner and edge sites), which are likely the unselective sites responsible for the C-C dissociation of the

  11. Kinetics on NiZn Bimetallic Catalysts for Hydrogen Evolution via Selective Dehydrogenation of Methylcyclohexane to Toluene

    KAUST Repository

    Shaikh Ali, Anaam; Jedidi, Abdesslem; Anjum, Dalaver H.; Cavallo, Luigi; Takanabe, Kazuhiro

    2017-01-01

    Liquid organic chemical hydrides are effective hydrogen storage media for easy and safe transport. The chemical couple of methylcyclohexane (MCH) and toluene (TOL) has been considered one of the feasible cycles for a hydrogen carrier, but the selective dehydrogenation of MCH to TOL has been reported using only Pt-based noble metal catalysts. This study reports MCH dehydrogenation to TOL using supported NiZn as a selective, non-noble-metal catalyst. A combined experimental and computational study was conducted to provide insight into the site requirements and reaction mechanism for MCH dehydrogenation to TOL, which were compared with those for cyclohexane (CH) dehydrogenation to benzene (BZ). The kinetic measurements carried out at 300-360°C showed an almost zero order with respect to MCH pressure in the high-pressure region (≥10 kPa) and nearly a positive half order with respective to H pressure (≤40 kPa). These kinetic data for the dehydrogenation reaction paradoxically indicate that hydrogenation of a strongly chemisorbed intermediate originating from TOL is the rate-determining step. Density functional theory (DFT) calculation confirms that the dehydrogenated TOL species at the aliphatic (methyl) position group (CHCH) were strongly adsorbed on the surface, which must be hydrogenated to desorb as TOL. This hydrogen-assisted desorption mechanism explains the essential role of excess H present in the feed in maintaining the activity of the metallic surface for hydrogenation. The rate of the CH to BZ reaction was less sensitive to H pressure than that of MCH to TOL, which can be explained by the absence of a methyl group in the structure, which in turn reduces the binding energy of the adsorbed species. DFT suggests that the improved TOL selectivity by adding Zn to Ni was due to Zn atoms preferentially occupying low-coordination sites on the surface (the corner and edge sites), which are likely the unselective sites responsible for the C-C dissociation of the

  12. A theoretical and shock tube kinetic study on hydrogen abstraction from phenyl formate.

    Science.gov (United States)

    Ning, Hongbo; Liu, Dapeng; Wu, Junjun; Ma, Liuhao; Ren, Wei; Farooq, Aamir

    2018-06-12

    The hydrogen abstraction reactions of phenyl formate (PF) by different radicals (H/O(3P)/OH/HO2) were theoretically investigated. We calculated the reaction energetics for PF + H/O/OH using the composite method ROCBS-QB3//M06-2X/cc-pVTZ and that for PF + HO2 at the M06-2X/cc-pVTZ level of theory. The high-pressure limit rate constants were calculated using the transition state theory in conjunction with the 1-D hindered rotor approximation and tunneling correction. Three-parameter Arrhenius expressions of rate constants were provided over the temperature range of 500-2000 K. To validate the theoretical calculations, the overall rate constants of PF + OH → Products were measured in shock tube experiments at 968-1128 K and 1.16-1.25 atm using OH laser absorption. The predicted overall rate constants agree well with the shock tube data (within 15%) over the entire experimental conditions. Rate constant analysis indicates that the H-abstraction at the formic acid site dominates the PF consumption, whereas the contribution of H-abstractions at the aromatic ring increases with temperature. Additionally, comparisons of site-specific H-abstractions from PF with methyl formate, ethyl formate, benzene, and toluene were performed to understand the effects of the aromatic ring and side-chain substituent on H-abstraction rate constants.

  13. Investigation of microstructure changes in ODS-EUROFER after hydrogen loading

    International Nuclear Information System (INIS)

    Emelyanova, O.V.; Ganchenkova, M.G.; Malitskii, E.; Yagodzinskyy, Y.N.; Klimenkov, M.; Borodin, V.A.; Vladimirov, P.V.; Lindau, R.; Möslang, A.; Hänninen, H.

    2016-01-01

    The effect of hydrogen on the microstructure of mechanically tested ODS-EUROFER steel was investigated by means of transmission electron microscopy, thermal desorption spectroscopy, and atomistic simulations. The presence of yttrium oxide particles notably increases hydrogen uptake in ODS-EUROFER steel as compared to ODS-free EUROFER 97. Under tensile loading, hydrogen accumulation promotes the loss of cohesion at the oxide particle interfaces. First-principles molecular dynamics simulations indicate that hydrogen can be trapped at nanoparticle/matrix interface, creating OH-groups. The accumulation of hydrogen atoms at the oxide particle surface can be the reason for the observed hydrogen-induced oxide/matrix interface weakening and de-cohesion under the action of external tensile stress.

  14. A computational investigation of the red and blue shifts in hydrogen

    Indian Academy of Sciences (India)

    The presentwork reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters ...

  15. The kinetics of Cr layer coated on TiNi films for hydrogen absorption

    Indian Academy of Sciences (India)

    Abstract. The effect of hydrogen absorption on electrical resistance with temperature ... pressure by thermal evaporation on the glass substrate at room temperature. ... and charging rate becomes faster in comparison to FeTi and TiNi thin films.

  16. Modeling the reaction kinetics of a hydrogen generator onboard a fuel cell -- Electric hybrid motorcycle

    Science.gov (United States)

    Ganesh, Karthik

    Owing to the perceived decline of the fossil fuel reserves in the world and environmental issues like pollution, conventional fuels may be replaced by cleaner alternative fuels. The potential of hydrogen as a fuel in vehicular applications is being explored. Hydrogen as an energy carrier potentially finds applications in internal combustion engines and fuel cells because it is considered a clean fuel and has high specific energy. However, at 6 to 8 per kilogram, not only is hydrogen produced from conventional methods like steam reforming expensive, but also there are storage and handling issues, safety concerns and lack of hydrogen refilling stations across the country. The purpose of this research is to suggest a cheap and viable system that generates hydrogen on demand through a chemical reaction between an aluminum-water slurry and an aqueous sodium hydroxide solution to power a 2 kW fuel cell on a fuel cell hybrid motorcycle. This reaction is essentially an aluminum-water reaction where sodium hydroxide acts as a reaction promoter or catalyst. The Horizon 2000 fuel cell used for this purpose has a maximum hydrogen intake rate of 28 lpm. The study focuses on studying the exothermic reaction between the reactants and proposes a rate law that best describes the rate of generation of hydrogen in connection to the surface area of aluminum available for the certain reaction and the concentration of the sodium hydroxide solution. Further, the proposed rate law is used in the simulation model of the chemical reactor onboard the hybrid motorcycle to determine the hydrogen flow rate to the fuel cell with time. Based on the simulated rate of production of hydrogen from the chemical system, its feasibility of use on different drive cycles is analyzed. The rate of production of hydrogen with a higher concentration of sodium hydroxide and smaller aluminum powder size was found to enable the installation of the chemical reactor on urban cycles with frequent stops and starts

  17. Kinetic Models Study of Hydrogenation of Aromatic Hydrocarbons in Vacuum Gas Oil and Basrah Crude Oil Reaction

    Directory of Open Access Journals (Sweden)

    Muzher M. Ibraheem

    2013-05-01

    Full Text Available             The aim of this research is to study the kinetic reaction models for catalytic hydrogenation of aromatic content for Basrah crude oil (BCO and vacuum gas oil (VGO derived from Kirkuk crude oil which has the boiling point rang of (611-833K.            This work is performed using a hydrodesulphurization (HDS pilot plant unit located in AL-Basil Company. A commercial (HDS catalyst cobalt-molybdenum (Co-Mo supported in alumina (γ-Al2O3 is used in this work. The feed is supplied by North Refinery Company in Baiji. The reaction temperatures range is (600-675 K over liquid hourly space velocity (LHSV range of (0.7-2hr-1 and hydrogen pressure is 3 MPa with H2/oil ratio of 300 of Basrah Crude oil (BCO, while the corresponding conditions for vacuum gas oil (VGO are (583-643 K, (1.5-3.75 hr-1, 3.5 MPa and 250  respectively .            The results showed that the reaction kinetics is of second order for both types of feed. Activation energies are found to be 30.396, 38.479 kJ/mole for Basrah Crude Oil (BCO and Vacuum Gas Oil (VGO respectively.

  18. Investigation of the Alkaline Electrochemical Interface and Development of Composite Metal/Metal-Oxides for Hydrogen and Oxygen Electrodes

    Science.gov (United States)

    Bates, Michael

    electrolyte. The HER kinetics of numerous binary & ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. Furthermore a model of the double layer interface is proposed, which helps explain the observed ensemble effect in the presence of AEI. In Chapter 3, Ni-Fe and Ni-Fe-Co mixed-metal-oxide (MMO) films were investigated for oxygen evolution reaction (OER) activity in 0.1M KOH on high surface area Raney-Nickel supports. During investigations of MMO activity, aniline was identified as a useful "capping agent" for synthesis of high-surface area MMO-polyaniline (PANI) composite materials. A Ni-Fe-Co/PANI-Raney-Ni catalyst was developed which exhibits enhanced mass-activity compared to state-of-the-art Ni-Fe OER electrocatalysts reported to date. The morphology of the MMO catalyst film on PANI/Raney-Ni support provides excellent dispersion of active-sites and should maintain high active-site utilization for catalyst loading on gas-diffusion electrodes. In Chapter 4, the de-activation of reversible-hydrogen electrode catalysts was investigated and the development of a Pt-Ir-Nx/C catalyst is reported, which exhibits significantly increased stability in the HBr/Br 2 electrolyte. In contrast a Pt-Ir/C catalyst exhibited increased tolerance to high-voltage cycling and in particular showed recovery of electrocatalytic activity after reversible de-activation (presumably from bromide adsorption and subsequent oxidative bromide stripping). Under the harshest testing conditions of high-voltage cycling or exposure to Br2 the Pt-based catalyst showed a trend in stability: Pt < Pt-Ir < Pt-Ir-Nx. (Abstract shortened by UMI.).

  19. Kinetic Investigations on Pd(II) Catalyzed Oxidation of Some Amino ...

    African Journals Online (AJOL)

    Kinetic investigations on Pd(II) catalyzed oxidation of dl-serine and dl-threonine by acidic solution of potassium bromate in the presence of mercuric acetate, as a scavenger have been made in the temperature range of 30–45°C. The rate shows zero order kinetics in bromate [BrO3‾] and order of reaction is one with respect ...

  20. Effect of Human and Bovine Serum Albumin on kinetic Chemiluminescence of Mn (III-Tetrakis (4-Sulfonatophenyl Porphyrin-Luminol-Hydrogen Peroxide System

    Directory of Open Access Journals (Sweden)

    Sayed Yahya Kazemi

    2012-01-01

    Full Text Available The present work deals with an attempt to study the effect of human and bovine serum albumin on kinetic parameters of chemiluminescence of luminol-hydrogen peroxide system catalyzed by manganese tetrasulfonatophenyl porphyrin (MnTSPP. The investigated parameters involved pseudo-first-order rise and fall rate constant for the chemiluminescence burst, maximum level intensity, time to reach maximum intensity, total light yield, and values of the intensity at maximum CL which were evaluated by nonlinear least square program KINFIT. Because of interaction of metalloporphyrin with proteins, the CL parameters are drastically affected. The systems resulted in Stern-Volmer plots with values of 3.17×105 and 3.7×105M−1 in the quencher concentration range of 1.5×10−6 to 1.5×10−5 M for human serum albumin (HSA and bovine serum albumin (BSA, respectively.

  1. NMR and IR Investigations of Strong Intramolecular Hydrogen Bonds

    Directory of Open Access Journals (Sweden)

    Poul Erik Hansen

    2017-03-01

    Full Text Available For the purpose of this review, strong hydrogen bonds have been defined on the basis of experimental data, such as OH stretching wavenumbers, νOH, and OH chemical shifts, δOH (in the latter case, after correction for ring current effects. Limits for O–H···Y systems are taken as 2800 > νOH > 1800 cm−1, and 19 ppm > δOH > 15 ppm. Recent results as well as an account of theoretical advances are presented for a series of important classes of compounds such as β-diketone enols, β-thioxoketone enols, Mannich bases, proton sponges, quinoline N-oxides and diacid anions. The O···O distance has long been used as a parameter for hydrogen bond strength in O–H···O systems. On a broad scale, a correlation between OH stretching wavenumbers and O···O distances is observed, as demonstrated experimentally as well as theoretically, but for substituted β-diketone enols this correlation is relatively weak.

  2. A kinetic model of the formation of organic monolayers on hydrogen-terminated silicon by hydrosilation of alkenes.

    Science.gov (United States)

    Woods, M; Carlsson, S; Hong, Q; Patole, S N; Lie, L H; Houlton, A; Horrocks, B R

    2005-12-22

    We have analyzed a kinetic model for the formation of organic monolayers based on a previously suggested free radical chain mechanism for the reaction of unsaturated molecules with hydrogen-terminated silicon surfaces (Linford, M. R.; Fenter, P. M.; Chidsey, C. E. D. J. Am. Chem. Soc 1995, 117, 3145). A direct consequence of this mechanism is the nonexponential growth of the monolayer, and this has been observed spectroscopically. In the model, the initiation of silyl radicals on the surface is pseudo first order with rate constant, ki, and the rate of propagation is determined by the concentration of radicals and unreacted Si-H nearest neighbor sites with a rate constant, kp. This propagation step determines the rate at which the monolayer forms by addition of alkene molecules to form a track of molecules that constitute a self-avoiding random walk on the surface. The initiation step describes how frequently new random walks commence. A termination step by which the radicals are destroyed is also included. The solution of the kinetic equations yields the fraction of alkylated surface sites and the mean length of the random walks as a function of time. In mean-field approximation we show that (1) the average length of the random walk is proportional to (kp/ki)1/2, (2) the monolayer surface coverage grows exponentially only after an induction period, (3) the effective first-order rate constant describing the growth of the monolayer and the induction period (kt) is k = (2ki kp)1/2, (4) at long times the effective first-order rate constant drops to ki, and (5) the overall activation energy for the growth kinetics is the mean of the activation energies for the initiation and propagation steps. Monte Carlo simulations of the mechanism produce qualitatively similar kinetic plots, but the mean random walk length (and effective rate constant) is overestimated by the mean field approximation and when kp > ki, we find k approximately ki0.7kp0.3 and Ea = (0.7Ei+ 0.3Ep

  3. Reaction kinetics of hydrogen atom abstraction from isopentanol by the H atom and HO2˙ radical.

    Science.gov (United States)

    Parab, Prajakta Rajaram; Heufer, K Alexander; Fernandes, Ravi Xavier

    2018-04-25

    Isopentanol is a potential next-generation biofuel for future applications to Homogeneous Charge Compression Ignition (HCCI) engine concepts. To provide insights into the combustion behavior of isopentanol, especially to its auto-ignition behavior which is linked both to efficiency and pollutant formation in real combustion systems, detailed quantum chemical studies for crucial reactions are desired. H-Abstraction reaction rates from fuel molecules are key initiation steps for chain branching required for auto-ignition. In this study, rate constants are determined for the hydrogen atom abstraction reactions from isopentanol by the H atom and HO2˙ radical by implementing the CBS-QB3 composite method. For the treatment of the internal rotors, a Pitzer-Gwinn-like approximation is applied. On comparing the computed reaction energies, the highest exothermicity (ΔE = -46 kJ mol-1) is depicted for Hα abstraction by the H atom whereas the lowest endothermicity (ΔE = 29 kJ mol-1) is shown for the abstraction of Hα by the HO2˙ radical. The formation of hydrogen bonding is found to affect the kinetics of the H atom abstraction reactions by the HO2˙ radical. Further above 750 K, the calculated high pressure limit rate constants indicate that the total contribution from delta carbon sites (Cδ) is predominant for hydrogen atom abstraction by the H atom and HO2˙ radical.

  4. Investigation of transfer parameters from the radiochromium on erythrocyte kinetic

    International Nuclear Information System (INIS)

    Tavares, J.L.M.

    1980-01-01

    This study analyzes and interprets results of destruction and survival data from 51 Cr labeled red cells to the more common and realistic situations for diagnostic applications in clinical and nuclear hematology. The destructive process and the deviation of the cell system from the equilibrium state can be conveniently studied in terms of the disappearance rate of labeled red blood cells, using some transfer parameters. The investigation was concentrated on selection and study of a mathematical model to describe significantly the elimination process and to improve and simplify the computational analysis of data in chromium erythrokinetics from patients and normal individuals for control. (author)

  5. Theoretical investigation on the alkali-metal doped BN fullerene as a material for hydrogen storage

    International Nuclear Information System (INIS)

    Venkataramanan, Natarajan Sathiyamoorthy; Belosludov, Rodion Vladimirovich; Note, Ryunosuke; Sahara, Ryoji; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2010-01-01

    Graphical abstract: First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. Adsorption of alkali atoms involves a charge transfer process, creating positively-charged alkali atoms and this polarizes the H 2 molecules and increases their binding energy. The maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 H 2 were adsorbed in molecular form. - Abstract: First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. The alkali atom adsorption takes place near the six tetragonal bridge sites available on the cage, thereby avoiding the notorious clustering problem. Adsorption of alkali atoms involves a charge transfer process, creating positively charged alkali atoms and this polarizes the H 2 molecules thereby, increasing their binding energy. Li atom has been found to adsorb up to three hydrogen molecules with an average binding energy of 0.189 eV. The fully doped Li 6 B 36 N 36 cluster has been found to hold up to 18 hydrogen molecules with the average binding energy of 0.146 eV. This corresponds to a gravimetric density of hydrogen storage of 3.7 wt.%. Chemisorption on the Li 6 B 36 N 36 has been found to be an exothermic reaction, in which 60 hydrogen atoms chemisorbed with an average chemisorption energy of -2.13 eV. Thus, the maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 hydrogen molecules were adsorbed in molecular form.

  6. Kinetics Investigation on Mushroom Tyrosinase Inhibition of Proso Millet

    Directory of Open Access Journals (Sweden)

    Wen-Ying Huang

    2018-01-01

    Full Text Available Proso millet (Panicum miliaceum is rich in nutritive components and is widely used as a human food, feed and forage for animals, and fuel. This study investigated the effect of a proso millet extract on the inhibition of tyrosinase, a key enzyme in melanogenesis. High performance liquid chromatography analysis indicated that the proso millet extract contained phenolic tyrosinase inhibitors, such as syringic acid, p-coumaric acid, and ferulic acid. The extract had an IC50 for inhibition of tyrosinase activity of 14.02 mg/mL. A Lineweaver-Burk double reciprocal plot showed that the proso millet extract functioned as a mixed competitive and noncompetitive inhibitor. Proso millet has potential as a tyrosinase inhibitor that may have applications in the cosmetics industry.

  7. NMR and IR investigations of strong intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Spanget-Larsen, Jens

    2017-01-01

    been used as a parameter for hydrogen bond strength in O–H···O systems. On a broad scale, a correlation between OH stretching wavenumbers and O···O distances is observed, as demonstrated experimentally as well as theoretically, but for substituted beta-diketone enols this correlation is relatively weak.......–1, and 19 >  dOH > 15 ppm. Recent results as well as an account of theoretical advances are presented for a series of important classes of compounds such as beta-diketone enols, beta-thioxoketone enols, Mannich bases, proton sponges, quinoline N-oxides and diacid anions. The O···O distance has long...

  8. Investigations in the field of photoelectrochemical production of hydrogen in Armenia

    International Nuclear Information System (INIS)

    Aroutiounian, V.M.; Arakelyan, V.M.; Shahnazaryan, G.E.

    2006-01-01

    Results of last years investigations of different metal oxide semiconductor photo electrodes for photoelectrochemical hydrogen production by method of water photo electrolysis are presented. It is shown that the investigations concerning the development of new photo electrodes made of solid solutions and more complicate multicomponent compositions are most promising. Possibilities of the use of porous and nanocrystalline oxide photo electrodes in photo electrochemistry are discussed also. Photo electrolysis setups for the photoelectrochemical conversion of solar energy in hydrogen are described

  9. FUNDAMENTAL KINETICS OF SUPERCRITICAL COAL LIQUEFACTION: EFFECT OF CATALYSTS AND HYDROGEN-DONOR SOLVENTS; FINAL

    International Nuclear Information System (INIS)

    Benjamin J. McCoy; J.M. Smith

    1998-01-01

    This report outlines a distribution kinetics approach to macromolecular reactions that has been applied to several processes. The objective was to develop an understanding of high-temperature, dense-phase thermolytic processes for complex macromolecular systems, such as coal. Experiments and theory are described for chemical models that simulate depolymerization of coal. The approach has been exceptionally successful for the model macromolecular systems. Development of a novel chemical reaction engineering analysis, based on distribution kinetics, was a major accomplishment of the current research

  10. Kinetic investigation of the chlorine reduction reaction on electrochemically oxidised ruthenium

    International Nuclear Information System (INIS)

    Thomassen, M.; Karlsen, C.; Borresen, B.; Tunold, R.

    2006-01-01

    The rate and mechanism of the electroreduction of chlorine on electrooxidised ruthenium has been investigated with focus on the effect of solution pH. Current/potential curves for the reduction process in solutions with constant chloride concentration of 1.0 mol dm -3 and varying H + concentration have been obtained with the use of the rotating disk electrode technique (RDE). It was found that the chlorine reduction rate is highly inhibited in solutions with high H + concentrations and that it can be satisfactorily described by the Erenburg mechanism, previously suggested for the chlorine evolution on RuO 2 and RTO. The expression of the kinetic current as a function of chlorine and H + concentration was obtained by solving the elementary rate equations of the kinetic mechanism. The kinetic constants obtained from the correlation of the kinetic current expression to the experimental data were used to simulate the dependence of the surface coverages and elementary reaction rates on overpotential

  11. Probing the hydrogen equilibrium and kinetics in zeolite imidazolate frameworks via molecular dynamics and quasi-elastic neutron scattering experiments.

    Science.gov (United States)

    Pantatosaki, Evangelia; Jobic, Hervé; Kolokolov, Daniil I; Karmakar, Shilpi; Biniwale, Rajesh; Papadopoulos, George K

    2013-01-21

    The problem of simulating processes involving equilibria and dynamics of guest sorbates within zeolitic imidazolate frameworks (ZIF) by means of molecular dynamics (MD) computer experiments is of growing importance because of the promising role of ZIFs as molecular "traps" for clean energy applications. A key issue for validating such an atomistic modeling attempt is the possibility of comparing the MD results, with real experiments being able to capture analogous space and time scales to the ones pertained to the computer experiments. In the present study, this prerequisite is fulfilled through the quasi-elastic neutron scattering technique (QENS) for measuring self-diffusivity, by elaborating the incoherent scattering signal of hydrogen nuclei. QENS and MD experiments were performed in parallel to probe the hydrogen motion, for the first time in ZIF members. The predicted and measured dynamics behaviors show considerable concentration variation of the hydrogen self-diffusion coefficient in the two topologically different ZIF pore networks of this study, the ZIF-3 and ZIF-8. Modeling options such as the flexibility of the entire matrix versus a rigid framework version, the mobility of the imidazolate ligand, and the inclusion of quantum mechanical effects in the potential functions were examined in detail for the sorption thermodynamics and kinetics of hydrogen and also of deuterium, by employing MD combined with Widom averaging towards studying phase equilibria. The latter methodology ensures a rigorous and efficient way for post-processing the dynamics trajectory, thereby avoiding stochastic moves via Monte Carlo simulation, over the large number of configurational degrees of freedom a nonrigid framework encompasses.

  12. On battery-less autonomous polygeneration microgrids: Investigation of the combined hybrid capacitors/hydrogen alternative

    International Nuclear Information System (INIS)

    Kyriakarakos, George; Piromalis, Dimitrios D.; Arvanitis, Konstantinos G.; Dounis, Anastasios I.; Papadakis, George

    2015-01-01

    Highlights: • A battery-less autonomous polygeneration microgrid is technically feasible. • Laboratory testing of hybrid capacitors. • Investigation of hybrid capacitors utilization along with hydrogen subsystem. - Abstract: The autonomous polygeneration microgrid topology aims to cover holistically the needs in remote areas as far as electrical power, potable water through desalination, fuel for transportation in the form of hydrogen, heating and cooling are concerned. Deep discharge lead acid batteries are mostly used in such systems, associated with specific disadvantages, both technical and environmental. This paper investigated the possibility of replacing the battery bank from a polygeneration microgrid with a hybrid capacitor bank and more intensive utilization of a hydrogen subsystem. Initially commercial hybrid capacitors were tested under laboratory conditions and based on the respective results a case study was performed. The optimized combination of hybrid capacitors and higher hydrogen usage was then investigated through simulations and compared to a polygeneration microgrid featuring deep discharge lead acid batteries. From the results it was clear that it is technically possible to exchange the battery bank with a hybrid capacitor bank and higher hydrogen utilization. From the economic point of view, the current cost of the hybrid capacitors and the hydrogen components is high which leads to higher overall cost in comparison with deep discharge lead acid batteries. Taking into account, though, the decreasing cost prospects and trends of both the hybrid capacitors and the hydrogen components it is expected that this approach will become economically competitive in a few years

  13. Dual Studies on a Hydrogen-Deuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    Science.gov (United States)

    Giles, Richard; Kim, Iris; Chao, Weyjuin Eric; Moore, Jennifer; Jung, Kyung Woon

    2014-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogen-deuterium (H-D) exchange of resorcinol by electrophilic aromatic substitution using D[subscript 2]O and a catalytic amount of H[subscript 2]SO[subscript 4]. The resulting labeled product is characterized by [superscript 1]H NMR. Students also…

  14. Qualitative relations between the kinetics of sintering in hydrogen and the observed microstructures of uranium dioxide

    International Nuclear Information System (INIS)

    Francois, B.; Delmas, R.; Caillat, F.; Lacombe, P.

    1975-01-01

    The microscopic study of uranium dioxide sintered in hydrogen, together with density measurements, shows on the one hand that the large scale appearance of pores trapped at the grain boundaries in the course of sintering has the effect of practically stopping densification, and on the other hand that this particular microstructure is stable over a wide range of time and temperature. (author)

  15. Kinetics and the mass transfer mechanism of hydrogen sulfide removal by biochar derived from rice hull.

    Science.gov (United States)

    Shang, Guofeng; Liu, Liang; Chen, Ping; Shen, Guoqing; Li, Qiwu

    2016-05-01

    The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperature has great influence on the adsorption of H2S. At the different pyrolysis temperature, the H2S removal efficiency of rice hull-derived biochar was different. The adsorption capacities of biochar were 2.09 mg·g(-1), 2.65 mg·g(-1), 16.30 mg·g(-1), 20.80 mg·g(-1), and 382.70 mg·g(-1), which their pyrolysis temperatures were 100 °C, 200 °C, 300 °C, 400 °C and 500 °C respectively. Based on the Yoon-Nelson model, it analyzed the mass transfer mechanism of hydrogen sulfide adsorption by biochar. The paper focuses on the biochar derived from rice hull-removed hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperatures have great influence on the adsorption of H2S. At the different pyrolysis temperatures, the H2S removal efficiency of rice hull-derived biohar was different. The adsorption capacities of biochar were 2.09, 2.65, 16.30, 20.80, and 382.70 mg·g(-1), and their pyrolysis temperatures were 100, 200, 300, 400, and 500 °C, respectively. Based on the Yoon-Nelson model, the mass transfer mechanism of hydrogen sulfide adsorption by biochar was analyzed.

  16. Ortho-para forms of hydrogen, deuterium, and tritium: radiation and self-induced conversion kinetics and equilibria

    International Nuclear Information System (INIS)

    Pyper, J.W.; Briggs, C.K.

    1977-01-01

    The theory of the ortho-para transitions in H 2 , D 2 , and T 2 is developed. Experimental and calculated values of the ortho-para compositions of the three hydrogen isotopes mentioned in the literature are correlated as a function of temperature, and are discussed critically. The kinetics of the radiation and self-induced ortho-para transitions are reviewed. In general, the radiation-induced transitions are more rapid than the self-induced transitions. We estimate (based on data for other systems) that the β-ray-induced ortho-para transitions in liquid D 2 or T 2 would be fast, with a half time on the order of a few minutes. Experiments are proposed to study these transitions in the liquid phase using infrared spectroscopy

  17. Molecular projectile effects for kinetic electron emission from carbon- and metal-surfaces bombarded by slow hydrogen ions

    International Nuclear Information System (INIS)

    Cernusca, S.; Winter, H.P.; Aumayr, F.; Diez Muino, R.; Juaristi, J.I.

    2003-01-01

    Total yields for kinetic electron emission (KE) have been determined for impact of hydrogen monomer-, dimer- and trimer-ions (impact energy <10 keV) on atomically clean surfaces of carbon-fiber inforced graphite used as first-wall armour in magnetic fusion devices. The data are compared with KE yields for impact of same projectile ions on atomically clean highly oriented pyrolytic graphite and polycrystalline gold. We discuss KE yields for the different targets if bombarded by equally fast molecular and atomic ions in view to 'projectile molecular effects' (different yields per proton for equally fast atomic and molecular ions), which are expected from calculated electronic projectile energy losses in these target materials

  18. Annealing Kinetic Model Using Fast and Slow Metastable Defects for Hydrogenated-Amorphous-Silicon-Based Solar Cells

    Directory of Open Access Journals (Sweden)

    Seung Yeop Myong

    2007-01-01

    Full Text Available The two-component kinetic model employing “fast” and “slow” metastable defects for the annealing behaviors in pin-type hydrogenated-amorphous-silicon- (a-Si:H- based solar cells is simulated using a normalized fill factor. Reported annealing data on pin-type a-Si:H-based solar cells are revisited and fitted using the model to confirm its validity. It is verified that the two-component model is suitable for fitting the various experimental phenomena. In addition, the activation energy for annealing of the solar cells depends on the definition of the recovery time. From the thermally activated and high electric field annealing behaviors, the plausible microscopic mechanism on the defect removal process is discussed.

  19. Swelling and hydrolysis kinetics of Kraft pulp fibers in aqueous 1-butyl-3-methylimidazolium hydrogen sulfate solutions.

    Science.gov (United States)

    Mao, Jia; Abushammala, Hatem; Pereira, Laura Barcellos; Laborie, Marie-Pierre

    2016-11-20

    1Butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) is efficient at extracting cellulose nanocrystals from pulp fibers. To shed some light on the respective contributions of swelling and hydrolysis of pulp fibers by [Bmim]HSO4, the physical, structural and morphological characteristics of hardwood Kraft pulp fibers were monitored under various conditions of temperature, water content and time. Swelling was largely compounded by hydrolysis at the highest temperatures (120°C) as evidenced by mass loss and reduced degree of polymerization (DPn) at this temperature. At 120°C only, water content appeared to play a significant role on the extent of hydrolysis. At this temperature, a heterogeneous kinetic model involving weak links and amorphous regions best described the experimental data. Hydrolysis rates were maximum at 25% water content in the aqueous ionic liquid. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Molecular projectile effects for kinetic electron emission from carbon- and metal-surfaces bombarded by slow hydrogen ions

    CERN Document Server

    Cernusca, S; Aumayr, F; Diez-Muino, R; Juaristi, J I

    2003-01-01

    Total yields for kinetic electron emission (KE) have been determined for impact of hydrogen monomer-, dimer- and trimer-ions (impact energy <10 keV) on atomically clean surfaces of carbon-fiber inforced graphite used as first-wall armour in magnetic fusion devices. The data are compared with KE yields for impact of same projectile ions on atomically clean highly oriented pyrolytic graphite and polycrystalline gold. We discuss KE yields for the different targets if bombarded by equally fast molecular and atomic ions in view to 'projectile molecular effects' (different yields per proton for equally fast atomic and molecular ions), which are expected from calculated electronic projectile energy losses in these target materials.

  1. Multi-scale theoretical investigation of hydrogen storage in covalent organic frameworks.

    Science.gov (United States)

    Tylianakis, Emmanuel; Klontzas, Emmanouel; Froudakis, George E

    2011-03-01

    The quest for efficient hydrogen storage materials has been the limiting step towards the commercialization of hydrogen as an energy carrier and has attracted a lot of attention from the scientific community. Sophisticated multi-scale theoretical techniques have been considered as a valuable tool for the prediction of materials storage properties. Such techniques have also been used for the investigation of hydrogen storage in a novel category of porous materials known as Covalent Organic Frameworks (COFs). These framework materials are consisted of light elements and are characterized by exceptional physicochemical properties such as large surface areas and pore volumes. Combinations of ab initio, Molecular Dynamics (MD) and Grand Canonical Monte-Carlo (GCMC) calculations have been performed to investigate the hydrogen adsorption in these ultra-light materials. The purpose of the present review is to summarize the theoretical hydrogen storage studies that have been published after the discovery of COFs. Experimental and theoretical studies have proven that COFs have comparable or better hydrogen storage abilities than other competitive materials such as MOF. The key factors that can lead to the improvement of the hydrogen storage properties of COFs are highlighted, accompanied with some recently presented theoretical multi-scale studies concerning these factors.

  2. Improvement in low-temperature and instantaneous high-rate output performance of Al-free AB5-type hydrogen storage alloy for negative electrode in Ni/MH battery: Effect of thermodynamic and kinetic regulation via partial Mn substituting

    Science.gov (United States)

    Zhou, Wanhai; Zhu, Ding; Tang, Zhengyao; Wu, Chaoling; Huang, Liwu; Ma, Zhewen; Chen, Yungui

    2017-03-01

    A series of Al-free Mn-modified AB5-type hydrogen storage alloys have been designed and the effects of thermodynamic stability and electrochemical kinetics on electrochemical performance via Mn substituting have been investigated. Compared with high-Al alloys, the Al-free alloys in this study have better low-temperature performance and instantaneous high-rate output because of the higher surface catalytic ability. After partial substitution of Ni by Mn, both the hydrogen desorption capacity and plateau pressure decrease, and correspondingly results in an improved thermodynamic stability which is adverse to low-temperature delivery. Additionally, with the improvement of charge acceptance ability and anti-corrosion property via Mn substitution, the room-temperature discharge capacity and cycling stability increase slightly. However, Mn adversely affects the electrochemical kinetics and deteriorates both the surface catalytic ability and the bulk hydrogen diffusion ability, leading to the drop of low-temperature dischargeability, high-rate dischargeability and peak power (Ppeak). Based on the thermodynamic and kinetic regulation and overall electrochemical properties, the optimal composition is obtained when x = 0.2, the discharge capacity is 243.6 mAh g-1 at -40 °C with 60 mA g-1, and the Ppeak attains to 969.6 W kg-1 at -40 °C.

  3. Investigation into periodic process of hydrogen isotope separation by counterflow method in the hydrogen-palladium system

    International Nuclear Information System (INIS)

    Andreev, B.M.; Selivanenko, I.L.; Vedeneev, A.I.; Golubkov, A.N.; Tenyaev, B.N.

    1999-01-01

    The key diagram and results of the investigation into working conditions of the pilot plant for hydrogen isotope separation embodying the concept of continuous counterflow separation in the hydrogen-palladium system are shown. The counterflow of phases in the plant is attained under the motion of palladium solid hydride phase relative to stationary blocks of flow rotation. The column separator is defined as section type one. The plant performs in periodic regime with accumulating vessels for light and heavy components of the separated mixture. Maximum concentration of the separated tritium ranged up to ∼ 96 % in the experiments of the deuterium-tritium separation. Minimum concentration of the residual tritium in the mixture ranged up to ∼ 0.1 %. The plant provides to reprocessing 4.5 moles of the gas a day [ru

  4. Kinetic Studies on Enzyme-Catalyzed Reactions: Oxidation of Glucose, Decomposition of Hydrogen Peroxide and Their Combination

    Science.gov (United States)

    Tao, Zhimin; Raffel, Ryan A.; Souid, Abdul-Kader; Goodisman, Jerry

    2009-01-01

    The kinetics of the glucose oxidase-catalyzed reaction of glucose with O2, which produces gluconic acid and hydrogen peroxide, and the catalase-assisted breakdown of hydrogen peroxide to generate oxygen, have been measured via the rate of O2 depletion or production. The O2 concentrations in air-saturated phosphate-buffered salt solutions were monitored by measuring the decay of phosphorescence from a Pd phosphor in solution; the decay rate was obtained by fitting the tail of the phosphorescence intensity profile to an exponential. For glucose oxidation in the presence of glucose oxidase, the rate constant determined for the rate-limiting step was k = (3.0 ± 0.7) ×104 M−1s−1 at 37°C. For catalase-catalyzed H2O2 breakdown, the reaction order in [H2O2] was somewhat greater than unity at 37°C and well above unity at 25°C, suggesting different temperature dependences of the rate constants for various steps in the reaction. The two reactions were combined in a single experiment: addition of glucose oxidase to glucose-rich cell-free media caused a rapid drop in [O2], and subsequent addition of catalase caused [O2] to rise and then decrease to zero. The best fit of [O2] to a kinetic model is obtained with the rate constants for glucose oxidation and peroxide decomposition equal to 0.116 s−1 and 0.090 s−1 respectively. Cellular respiration in the presence of glucose was found to be three times as rapid as that in glucose-deprived cells. Added NaCN inhibited O2 consumption completely, confirming that oxidation occurred in the cellular mitochondrial respiratory chain. PMID:19348778

  5. Beneficial effect of carbon on hydrogen desorption kinetics from Mg–Ni–In alloy

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jiří; Král, Lubomír

    2013-01-01

    Roč. 546, JAN (2013), s. 129-137 ISSN 0925-8388 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA ČR GA106/09/0814; GA ČR(CZ) GAP108/11/0148 Institutional research plan: CEZ:AV0Z20410507 Keywords : Energy storage materials * Hydrogen absorbing materials * Metal hydrides Subject RIV: JG - Metallurgy Impact factor: 2.726, year: 2013

  6. A Kinetic Study of a Homodienyl-[1,5]-Hydrogen Shift in a Vinylaziridine

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Hussenius, Anita; Somfai, Peter

    1996-01-01

    The thermal rearrangement of an N-substituted vinylaziridine to the corresponding Z-allylic amine, i.e. a homodienyl-[1,5]-hydrogen shift was studied at various temperatures in the reange 40 90 oC, and NMR spectroscopy was used to follow the reactiuon. The activation enthalpiies and entropies...... measured clearly indicate a concerted mechanism for the rearrangement, via a cyclic transition state....

  7. One-step reduced kinetics for lean hydrogen-air deflagration

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Galisteo, D.; Sanchez, A.L. [Area de Mecanica de Fluidos, Univ. Carlos III de Madrid, Leganes 28911 (Spain); Linan, A. [ETSI Aeronauticos, Pl. Cardenal Cisneros 3, Madrid 28040 (Spain); Williams, F.A. [Dept. of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093-0411 (United States)

    2009-05-15

    A short mechanism consisting of seven elementary reactions, of which only three are reversible, is shown to provide good predictions of hydrogen-air lean-flame burning velocities. This mechanism is further simplified by noting that over a range of conditions of practical interest, near the lean flammability limit all reaction intermediaries have small concentrations in the important thin reaction zone that controls the hydrogen-air laminar burning velocity and therefore follow a steady state approximation, while the main species react according to the global irreversible reaction 2H{sub 2} + O{sub 2} {yields} 2H{sub 2}O. An explicit expression for the non-Arrhenius rate of this one-step overall reaction for hydrogen oxidation is derived from the seven-step detailed mechanism, for application near the flammability limit. The one-step results are used to calculate flammability limits and burning velocities of planar deflagrations. Furthermore, implications concerning radical profiles in the deflagration and reasons for the success of the approximations are clarified. It is also demonstrated that adding only two irreversible direct recombination steps to the seven-step mechanism accurately reproduces burning velocities of the full detailed mechanism for all equivalence ratios at normal atmospheric conditions and that an eight-step detailed mechanism, constructed from the seven-step mechanism by adding to it the fourth reversible shuffle reaction, improves predictions of O and OH profiles. The new reduced-chemistry descriptions can be useful for both analytical and computational studies of lean hydrogen-air flames, decreasing required computation times. (author)

  8. Kinetic study of the effects of calcium ions on cationic artichoke (Cynara scolymus L.) peroxidase: calcium binding, steady-state kinetics and reactions with hydrogen peroxide.

    Science.gov (United States)

    Hiner, Alexander N P; Sidrach, Lara; Chazarra, Soledad; Varón, Ramón; Tudela, José; García-Cánovas, Francisco; Rodríguez-López, José Neptuno

    2004-01-01

    The apparent catalytic constant (k(cat)) of artichoke (Cynara scolymus L.) peroxidase (AKPC) with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) increased 130-fold in the presence of calcium ions (Ca2+) but the affinity (K(m)) of the enzyme for ABTS was 500 times lower than for Ca2+-free AKPC. AKPC is known to exhibit an equilibrium between 6-aquo hexa-coordinate and penta-coordinate forms of the haem iron that is modulated by Ca2+ and affects compound I formation. Measurements of the Ca2+ dissociation constant (K(D)) were complicated by the water-association/dissociation equilibrium yielding a global value more than 1000 times too high. The value for the Ca2+ binding step alone has now been determined to be K(D) approximately 10 nM. AKPC-Ca2+ was more resistant to inactivation by hydrogen peroxide (H(2)O(2)) and exhibited increased catalase activity. An analysis of the complex H(2)O(2) concentration dependent kinetics of Ca2+-free AKPC is presented.

  9. Investigation of Hydrogen and Nitrogen Content in Compacted Graphite Iron Production

    OpenAIRE

    Siafakas, Dimitrios

    2013-01-01

    The aim of this research, part of a wider program called SPOFIC, is to investigate how the casting procedure affects the concentration of hydrogen and nitrogen gases in Compacted Graphite Iron used for the production of truck cylinder blocks. Hydris equipment was used for the Hydrogen measurements and the Optical Emission Spectroscopy and combustion analysis methods were used for the nitrogen measurements. The experiment was performed in one of the cooperating foundries. It was found that Hyd...

  10. High-yield hydrogen production from biomass by in vitro metabolic engineering: Mixed sugars coutilization and kinetic modeling

    Science.gov (United States)

    Rollin, Joseph A.; Martin del Campo, Julia; Myung, Suwan; Sun, Fangfang; You, Chun; Bakovic, Allison; Castro, Roberto; Chandrayan, Sanjeev K.; Wu, Chang-Hao; Adams, Michael W. W.; Senger, Ryan S.; Zhang, Y.-H. Percival

    2015-01-01

    The use of hydrogen (H2) as a fuel offers enhanced energy conversion efficiency and tremendous potential to decrease greenhouse gas emissions, but producing it in a distributed, carbon-neutral, low-cost manner requires new technologies. Herein we demonstrate the complete conversion of glucose and xylose from plant biomass to H2 and CO2 based on an in vitro synthetic enzymatic pathway. Glucose and xylose were simultaneously converted to H2 with a yield of two H2 per carbon, the maximum possible yield. Parameters of a nonlinear kinetic model were fitted with experimental data using a genetic algorithm, and a global sensitivity analysis was used to identify the enzymes that have the greatest impact on reaction rate and yield. After optimizing enzyme loadings using this model, volumetric H2 productivity was increased 3-fold to 32 mmol H2⋅L−1⋅h−1. The productivity was further enhanced to 54 mmol H2⋅L−1⋅h−1 by increasing reaction temperature, substrate, and enzyme concentrations—an increase of 67-fold compared with the initial studies using this method. The production of hydrogen from locally produced biomass is a promising means to achieve global green energy production. PMID:25848015

  11. High-yield hydrogen production from biomass by in vitro metabolic engineering: Mixed sugars coutilization and kinetic modeling.

    Science.gov (United States)

    Rollin, Joseph A; Martin del Campo, Julia; Myung, Suwan; Sun, Fangfang; You, Chun; Bakovic, Allison; Castro, Roberto; Chandrayan, Sanjeev K; Wu, Chang-Hao; Adams, Michael W W; Senger, Ryan S; Zhang, Y-H Percival

    2015-04-21

    The use of hydrogen (H2) as a fuel offers enhanced energy conversion efficiency and tremendous potential to decrease greenhouse gas emissions, but producing it in a distributed, carbon-neutral, low-cost manner requires new technologies. Herein we demonstrate the complete conversion of glucose and xylose from plant biomass to H2 and CO2 based on an in vitro synthetic enzymatic pathway. Glucose and xylose were simultaneously converted to H2 with a yield of two H2 per carbon, the maximum possible yield. Parameters of a nonlinear kinetic model were fitted with experimental data using a genetic algorithm, and a global sensitivity analysis was used to identify the enzymes that have the greatest impact on reaction rate and yield. After optimizing enzyme loadings using this model, volumetric H2 productivity was increased 3-fold to 32 mmol H2⋅L(-1)⋅h(-1). The productivity was further enhanced to 54 mmol H2⋅L(-1)⋅h(-1) by increasing reaction temperature, substrate, and enzyme concentrations--an increase of 67-fold compared with the initial studies using this method. The production of hydrogen from locally produced biomass is a promising means to achieve global green energy production.

  12. Kinetic energy measurement of hydrogen in LHD peripheral plasma with a multi-wavelength-range fine-resolution spectrometer

    International Nuclear Information System (INIS)

    Fujii, Keisuke; Mizushiri, Keisuke; Nishioka, Tomomi; Shikama, Taiichi; Iwamae, Atsushi; Goto, Motoshi; Morita, Shigeru; Hasuo, Masahiro

    2010-01-01

    We have simultaneously measured high resolution emission spectra of the hydrogen atomic Balmer-α, -β, -γ lines and molecular Fulcher-α band for a LHD peripheral plasma generated under a central magnetic field strength of 0.4 T. It is found that the velocity distributions of excited atoms calculated from the Balmer-α, -β, and -γ line shapes show similar profiles to each other. The translational kinetic energy corresponding to the average velocity is about 13 eV, which is about 300 times larger than the rotational energy of hydrogen molecules estimated from the line intensities in the Fulcher-α band. The velocity distributions differ from Maxwellian and have a high velocity tail over 1x10 5 m/s. A correlation between the high velocity tail and the electron temperature and density is seen and suggesting the excited atoms having such high velocities to be generated by the charge exchange collisions from high velocity protons in the peripheral region.

  13. Hydrogen peroxide release kinetics into saliva from different whitening products: a double-blind, randomized clinical trial.

    Science.gov (United States)

    Marques, Duarte Nuno da Silva; da Mata, António Duarte Sola Pereira; Silveira, João Miguel Lourenço; Marques, Joana Rita Oliveira Faria; Amaral, João Pedro de Almeida Rato; Guilherme, Nuno Filipe Rito Parada Marques

    2012-02-01

    The objective of this study is to compare salivary hydrogen peroxide (HP) release kinetics and potential toxicity of systemic exposure of four different whitening products. A double-blind, randomized controlled trial was conducted in a Portuguese dental faculty clinic. Two hundred forty volunteers were randomized to eight intervention groups. Participants were randomly assigned to receive active or placebo applications of one of four different products: Opalescence 10% PF™ (OPL), Vivastyle® 10%™ (VS10%), Vivadent Paint On Plus™ (PO+), and Trés White Supreme™ (TWS). Saliva collection was obtained by established methods at different times. The HP salivary content was determined by a photometric method. Salivary HP variations, total amount of salivary HP, and counts of subjects above the safe daily HP dose were the main outcome measures. All whitening systems significantly released HP to the saliva when compared to placebo, and all showed different release kinetics. The adaptable tray system (TWS) presented a risk increase of 37% [20-54%, 95% confidence interval] when compared to the other systems. The use of an adaptable tray whitening system with higher concentration of HP increases the toxicity potential.

  14. Degradation kinetics and mechanism of trace nitrobenzene by granular activated carbon enhanced microwave/hydrogen peroxide system.

    Science.gov (United States)

    Tan, Dina; Zeng, Honghu; Liu, Jie; Yu, Xiaozhang; Liang, Yanpeng; Lu, Lanjing

    2013-07-01

    The kinetics of the degradation of trace nitrobenzene (NB) by a granular activated carbon (GAC) enhanced microwave (MW)/hydrogen peroxide (H202) system was studied. Effects of pH, NB initial concentration and tert-butyl alcohol on the removal efficiency were examined. It was found that the reaction rate fits well to first-order reaction kinetics in the MW/GAC/H202 process. Moreover, GAC greatly enhanced the degradation rate of NB in water. Under a given condition (MW power 300 W, H202 dosage 10 mg/L, pH 6.85 and temperature (60 +/- 5)degrees C), the degradation rate of NB was 0.05214 min-1when 4 g/L GAC was added. In general, alkaline pH was better for NB degradation; however, the optimum pH was 8.0 in the tested pH value range of 4.0-12.0. At H202 dosage of 10 mg/L and GAC dosage of 4 g/L, the removal of NB was decreased with increasing initial concentrations of NB, indicating that a low initial concentration was beneficial for the degradation of NB. These results indicated that the MW/GAC/H202 process was effective for trace NB degradation in water. Gas chromatography-mass spectrometry analysis indicated that a hydroxyl radical addition reaction and dehydrogenation reaction enhanced NB degradation.

  15. Plutonium(IV) peroxide formation in nitric medium and kinetics Pu(VI) reduction by hydrogen peroxide

    International Nuclear Information System (INIS)

    Maillard, C.; Adnet, J.M.

    2001-01-01

    Reduction of plutonium (VI) to Pu(IV) with hydrogen peroxide is a step in industrial processes used to purify plutonium nitrate solutions. This operation must be carefully controlled, in order to avoid any formation of the Pu(IV) peroxide green precipitate and to obtain exclusively Pu(IV). This led us to study the acidity and Pu and H 2 O 2 concentrations influences on the precipitate appearance and to perform a Pu(VI) reduction kinetic study on a wide range of acidities ([HNO 3 ]: 0.5 to 8 M), plutonium concentrations ([Pu(VI)]: 0.1 to 0.8 M) and [H 2 O 2 ]/[Pu(VI)] ratio (from 1 to 8). Thus, the domain of Pu(IV) peroxide formation and the reactional paths were established. With the exception of 0.5 M nitric acid medium, the kinetic curves show two distinct regims: the first one corresponds to an induction period where the Pu(VI) concentration doesn't change, the second corresponds to a linear decrease of Pu(VI). An increase of the temperature greatly accelerates the Pu(VI) reduction rate while [H 2 O 2 ]/[Pu(VI)] has almost no influence. The Pu(VI) total reduction time decreases when initial concentration of plutonium increases. By increasing nitric acid concentration from 0.5 M to 6 M, the total Pu(VI) reduction time decreases. This time increases when [HNO 3 ] varies from 6 M to 8 M. (orig.)

  16. Investigation on the Structure and Electrochemical Properties of La-Ce-Mg-Al-Ni Hydrogen Storage Alloy

    Directory of Open Access Journals (Sweden)

    Yuqing Qiao

    2013-01-01

    Full Text Available Structure and electrochemical characteristics of La0.96Ce0.04Mg0.15Al0.05Ni2.8 hydrogen storage alloy have been investigated. X-ray diffraction analyses reveal that the La0.96Ce0.04Mg0.15Al0.05Ni2.8 hydrogen storage alloy consisted of a (La, MgNi3 phase with the rhombohedral PuNi3-type structure and a LaNi5 phase with the hexagonal CaCu5-type structure. TEM shows that the alloy is multicrystal with a lattice space 0.187 nm. EDS analyse shows that the content of Mg is 3.48% (atom which coincide well with the designed composition of the electrode alloy. Electrochemical investigations show that the maximum discharge capacity of the alloy electrode is 325 mAh g−1. The alloy electrode has higher discharge capacity within the discharge current density span from 60 mA g−1 to 300 mA g−1. Electrochemical impedance spectroscopy measurements indicate that the charge transfer resistance RT on the alloy electrode surface and the calculated exchange current density I0 are 0.135 Ω and 1298 mA g−1, respectively; the better eletrochemical reaction kinetic of the alloy electrode may be responsible for the better high-rate dischargeability.

  17. Investigation on CO catalytic oxidation reaction kinetics of faceted perovskite nanostructures loaded with Pt

    KAUST Repository

    Yin, S. M.

    2017-01-18

    Perovskite lead titanate nanostructures with specific {111}, {100} and {001} facets exposed, have been employed as supports to investigate the crystal facet effect on the growth and CO catalytic activity of Pt nanoparticles. The size, distribution and surface chemical states of Pt on the perovskite supports have been significantly modified, leading to a tailored conversion temperature and catalytic kinetics towards CO catalytic oxidation.

  18. Kinetic investigation of the oxidation of N-alkyl anilines by ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 112; Issue 6. Kinetic investigation of the oxidation of N-alkyl anilines by peroxomonophosphoric acid in anionic surfactant sodium lauryl sulphate. G P Panigrahi Jagannath Panda. Physical and Theoretical Volume 112 Issue 6 December 2000 pp 615-622 ...

  19. Investigating High-School Chemical Kinetics: The Greek Chemistry Textbook and Students' Difficulties

    Science.gov (United States)

    Gegios, Theodoros; Salta, Katerina; Koinis, Spyros

    2017-01-01

    In this study we present an analysis of how the structure and content of the Greek school textbook approaches the concepts of chemical kinetics, and an investigation of the difficulties that 11th grade Greek students face regarding these concepts. Based on the structure and content of the Greek textbook, a tool was developed and applied to…

  20. Investigation on CO catalytic oxidation reaction kinetics of faceted perovskite nanostructures loaded with Pt

    KAUST Repository

    Yin, S. M.; Duanmu, J. J.; Zhu, Yihan; Yuan, Y. F.; Guo, S. Y.; Yang, J. L.; Ren, Z. H.; Han, G. R.

    2017-01-01

    Perovskite lead titanate nanostructures with specific {111}, {100} and {001} facets exposed, have been employed as supports to investigate the crystal facet effect on the growth and CO catalytic activity of Pt nanoparticles. The size, distribution and surface chemical states of Pt on the perovskite supports have been significantly modified, leading to a tailored conversion temperature and catalytic kinetics towards CO catalytic oxidation.

  1. Doping kinetics of organic semiconductors investigated by field-effect transistors

    NARCIS (Netherlands)

    Maddalena, F.; Meijer, E.J.; Asadi, K.; Leeuw, D.M. de; Blom, P.W.M.

    2010-01-01

    The kinetics of acid doping of the semiconductor regioregular poly-3-hexylthiophene with vaporized chlorosilane have been investigated using field-effect transistors. The dopant density has been derived as a function of temperature and exposure time from the shift in the pinch-off voltage, being the

  2. Experimental investigations of the hydrogen addition effects on diesel engine performance

    Science.gov (United States)

    Mirica, I.; Pana, C.; Negurescu, N.; Cernat, A.; Nutu, C.

    2016-08-01

    In the global content regarding the impact on the environmental of the gases emissions resulted from the fossil fuels combustion, an interest aspect discussed on the 21st Session of the Conference of the Parties from the 2015 Paris Climate Conference and the gradual diminution of the worldwide oil reserves contribute to the necessity of searching of alternative energy from durable and renewable resources. At the use of hydrogen as addition in air to diesel engine, the level of CO, HC and smoke from the exhaust gases will decrease due to the improvement of the combustion process. At low and medium partial loads and low hydrogen energetic ratios used the NOX emission level can decrease comparative to classic diesel engine. The hydrogen use as fuel for diesel engine leads to the improving of the energetic and emissions performance of the engine due to combustion improvement and reduction of carbon content. The paper presents, in a comparative way, results of the experimental researches carried on a truck compression ignition engine fuelled with diesel fuel and with hydrogen diesel fuel and hydrogen as addition in air at different engine operation regimes. The results obtained during experimental investigations show better energetic and pollution performance of the engine fuelled with hydrogen as addition in air comparative to classic engine. The influences of hydrogen addition on engine operation are shown.

  3. Kinetics and mechanism of the furan peroxide formation in the reaction of furfural with hydrogen peroxide in the presence and absence of sodium molybdate

    International Nuclear Information System (INIS)

    Grunskaya, E.P.; Badovskaya, L.A.; Kaklyugina, T.Ya.; Poskonin, V.V.

    2000-01-01

    Kinetics of the initial stage of the reaction of furfural with hydrogen peroxide are studied in the presence of Na 2 MoO 4 in water and without catalytic additions in n-butanol. Organic peroxide having in its disposal Mo(6), which is the only product on the initial stage of the reaction, is formed since the first minutes of oxidation of furfural by hydrogen peroxide with the presence of Na 2 MoO 4 . The mechanisms of conversion of furfural in the Na 2 MoO 4 - H 2 O system and its oxidation by peroxide without sodium molybdate are discussed. Schemes of formation of furfural complexes based on the results of kinetic studies are suggested. Comparison of obtained data demonstrates that presence of the sodium molybdates in the reaction medium trends to change of reaction procedure in the hydrogen peroxide [ru

  4. Kinetics of solid-phase in ion exchange on tin hydrogen phosphate

    International Nuclear Information System (INIS)

    Kislitsyn, M.N.; Ketsko, V.A.; Yaroslavtsev, A.B.

    2004-01-01

    Solid state reactions in mixture of tin hydrogen phosphate and alkali metal (M=Na, K, Cs) chlorides have been studied both in the mode of polythermal heating and at a fixed temperature, using data of X-ray phase and thermogravimetric analyses. In the range 400-750 Deg C solid state ion exchange reactions occur in the systems studied and yield mono-- and dialkali phosphates MHSn(PO 4 ) 2 and M 2 Sn(PO 4 ) 2 . Counter diffusion coefficients for alkali metal cations and protons in the matrices of compositions MHSn(PO 4 ) 2 and M 2 Sn(PO 4 ) 2 have been determined [ru

  5. Hydrogen.

    Science.gov (United States)

    Bockris, John O'M

    2011-11-30

    The idea of a "Hydrogen Economy" is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO₂ in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H₂ from the electrolyzer. Methanol made with CO₂ from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan). Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs) by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  6. Kinetic investigation of the immobilization of chromotropic acid derivatives onto anion exchange resin

    Directory of Open Access Journals (Sweden)

    Savić Jasmina

    2007-01-01

    Full Text Available The adsorption kinetics of pyrazol- (РАСА and imidazol-azo-chromo-tropic acid (IACA onto Dowex 1-X8 resin, as a function of the dye concentration and temperature were investigated at pH 4.5. The pseudo-first- and second-order kinetic models and intraparticle diffusion model were used to describe the obtained kinetic data. The adsorption rate constants were found to be in the order of magnitude 10-2 min-1 for all of the used kinetics models. The adsorption capacity increases with increasing initial dye concentration. The study of adsorption kinetics at different temperatures (in the range from 5 to 25 °C reveals an increase in the rate of adsorption and adsorption capacity with increasing temperature. The activation energy (in the case of РАСА 16.6 kJ/mol, and for IACA 11.3 kJ/mol was determined using the Arrhenius dependence. Electrostatic interactions between the dye and resin beads were shown to be the adsorption mechanism.

  7. Catalytic Reforming of Higher Hydrocarbon Fuels to Hydrogen: Process Investigations with Regard to Auxiliary Power Units

    OpenAIRE

    Kaltschmitt, Torsten

    2012-01-01

    This thesis discusses the investigation of the catalytic partial oxidation on rhodium-coated honeycomb catalysts with respect to the conversion of a model surrogate fuel and commercial diesel fuel into hydrogen for the use in auxiliary power units. Furthermore, the influence of simulated tail-gas recycling was investigated.

  8. Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

    Science.gov (United States)

    Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

    2015-12-21

    A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Investigation of Zirconium Oxide Films in Different Dissolved Hydrogen Concentration

    International Nuclear Information System (INIS)

    Kim, Taeho; Choi, Kyoung Joon; Yoo, Seung Chang; Kim, Ji Hyun

    2016-01-01

    It has been reported that in pre-transition zirconium oxide, the volume fraction of tetragonal zirconium oxide increased near the oxide/metal (O/M) interface, and the sub-stoichiometric zirconium oxide layer was observed. The diffusion of oxygen ion through the oxide layer is the rate-limiting process during the pre-transition oxidation process, and this diffusion mainly occurs in the grain boundaries. The two layered oxide structure is formed in pre-transition oxide for the zirconium alloy in high-temperature water environment. It is known that the corrosion rate is related to the volume fraction of zirconium oxide and the pores in the oxides; therefore, the aim of this paper is to investigate the oxidation behavior in the pre-transition zirconium oxide in high-temperature water chemistry. In this study, in situ Raman and TEM analysis were conducted for investigating the phase transformation of zirconium alloy in primary water. From this study, the following conclusions are drawn: 1. The zirconium alloy was oxidized in primary water chemistry for 100 d, and Raman and TEM were measured after 30, 50, 80, and 100 d from start-up. 2. TEM and FFT analysis showed that the zirconium oxide mostly consisted of the monoclinic phase. The tetragonal zirconium oxide was just found near the O/M interface

  10. The role of hydrogen bonding on kinetics of rearrangement of heterocyclic aldoximes in perchloric acide

    International Nuclear Information System (INIS)

    Azzouz, A.S.; Abdullah, K.A.; Al-Niemi, I.

    1995-01-01

    Four paris of syn and anti aromatic heterocyclic aldoximes as 2-thiophenealdoxime, 2- furfuraladoxime, 2-pyridinealdoxime and 2-pyrrolealdoxime are prepared. The strcutures of these geometrical isomers are confirmed by the meaasurements of their U.V. I, R and melting points. Experiments show the existence of these aldoximers in an intramolecular hy-drogen bonding with variable strength depending on the hetero ztoms in the aldoximes. The first order rate constants of the rearrangement of syn aldoximes follow the order of hetero S>O>N, while the anti aldoximes show irregular order, Factors governing the aniti constants of the rearrangement of syn and anti aldoximes are analysed. Activation parameters are estimated and discussed on the basis of isokinetic relation-ship. The differences in physical and spectroscpic behavior of aldoximes lead to an important suggestion regarding the configuration of oxime. (author). 27 refs., 2 figs., 2 tabs

  11. Detailed kinetic and heat transport model for the hydrolysis of lignocellulose by anhydrous hydrogen fluoride vapor

    Energy Technology Data Exchange (ETDEWEB)

    Rorrer, G.L.; Mohring, W.R.; Lamport, D.T.A.; Hawley, M.C.

    1988-01-01

    Anhydrous Hydrogen Fluoride (HF) vapor at ambient conditions efficiently and rapidly hydrolyzed lignocellulose to glucose and lignin. The unsteady-state reaction of HF vapor with a single lignocellulose chip was mathematically modeled under conditions where external and internal mass-transfer resistances were minimized. The model incorporated physical adsorption of HF vapor onto the lignocellulosic matrix and solvolysis of cellulose to glucosyl fluoride by adsorbed HF into the differential material and energy balance expressions. Model predictions for the temperature distribution and global glucose yield in the HF-reacting lignocellulose chip as a function of reaction time and HF vapor stream temperature agreed reasonably with the complimentary experimental data. The model correctly predicted that even when mass-transfer resistances for the reaction of HF vapor with a single lignocellulose chip are minimized, external and internal heat-transfer resistances are still significant.

  12. Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase*

    Science.gov (United States)

    Mishanina, Tatiana V.; Yadav, Pramod K.; Ballou, David P.; Banerjee, Ruma

    2015-01-01

    The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H2S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be −123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation. PMID:26318450

  13. Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase.

    Science.gov (United States)

    Mishanina, Tatiana V; Yadav, Pramod K; Ballou, David P; Banerjee, Ruma

    2015-10-09

    The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H2S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be -123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  14. Hydrogen disposal investigation for the Space Shuttle launch complex at Vandenberg Air Force Base

    Science.gov (United States)

    Breit, Terry J.; Elliott, George

    1987-01-01

    The concern of an overpressure condition on the aft end of the Space Shuttle caused by ignition of unburned hydrogen being trapped in the Space Shuttle Main Engine exhaust duct at the Vandenberg AFB launch complex has been investigated for fifteen months. Approximately twenty-five concepts have been reviewed, with four concepts being thoroughly investigated. The four concepts investigated were hydrogen burnoff ignitors (ignitors located throughout the exhaust duct to continuously ignite any unburned hydrogen), jet mixing (utilizing large volumes of high pressure air to ensure complete combustion of the hydrogen), steam inert (utilizing flashing hot water to inert the duct with steam) and open duct concept (design an open duct or above grade J-deflector to avoid trapping hydrogen gas). Extensive studies, analyses and testing were performed at six test sites with technical support from twenty-two major organizations. In December 1986, the Air Force selected the steam inert concept to be utilized at the Vandenberg launch complex and authorized the design effort.

  15. Investigation on hydrogen permeation on heat exchanger materials in conditions of steam coal gasification

    International Nuclear Information System (INIS)

    Moellenhoff, H.

    1984-01-01

    The permeation of hydrogen through iron-based alloys of different compositions in the temperature range between 700 and 1000 0 C was examined in a laboratory fluidized bed in the conditions of steam/coal gasification. Apart from tests on bright metal samples, measurement in the gasification atmosphere at a maximum pressure of 1 bar were carried out during oxidation of the metal. Experiments in a steam/hydrogen/argon mixture with the same oxidation potential were used for comparison purposes. The hydrogen permeated through the metal sample was taken to a gas chromatograph with argon flushing gas and analyzed there. The investigations on bright steel samples of various composition showed that their permeabilities for hydrogen at temperatures around 900 0 C only differed by a maximum of ± 30%. Effective prevention of permeation is therefore not possible simply by choosing a suitable alloy. If the steels are oxidized during permeation measurements, there is a reduction of the hydrogen permeability by 2 or 3 orders of magnitude due to the oxidation process, both in the steam/coal gasification fluidized bed and in a pure steam/hydrogen/argon mixture. (orig./GG) [de

  16. Hydrogen

    Directory of Open Access Journals (Sweden)

    John O’M. Bockris

    2011-11-01

    Full Text Available The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan. Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  17. Kinetic theory of weakly ionized dilute gas of hydrogen-like atoms of the first principles of quantum statistics and dispersion laws of eigenwaves

    Science.gov (United States)

    Slyusarenko, Yurii V.; Sliusarenko, Oleksii Yu.

    2017-11-01

    We develop a microscopic approach to the construction of the kinetic theory of dilute weakly ionized gas of hydrogen-like atoms. The approach is based on the statements of the second quantization method in the presence of bound states of particles. The basis of the derivation of kinetic equations is the method of reduced description of relaxation processes. Within the framework of the proposed approach, a system of common kinetic equations for the Wigner distribution functions of free oppositely charged fermions of two kinds (electrons and cores) and their bound states—hydrogen-like atoms— is obtained. Kinetic equations are used to study the spectra of elementary excitations in the system when all its components are non-degenerate. It is shown that in such a system, in addition to the typical plasma waves, there are longitudinal waves of matter polarization and the transverse ones with a behavior characteristic of plasmon polaritons. The expressions for the dependence of the frequencies and Landau damping coefficients on the wave vector for all branches of the oscillations discovered are obtained. Numerical evaluation of the elementary perturbation parameters in the system on an example of a weakly ionized dilute gas of the 23Na atoms using the D2-line characteristics of the natrium atom is given. We note the possibility of using the results of the developed theory to describe the properties of a Bose condensate of photons in the diluted weakly ionized gas of hydrogen-like atoms.

  18. Investigation of thermolytic hydrogen generation rate of tank farm simulated and actual waste

    Energy Technology Data Exchange (ETDEWEB)

    Martino, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Newell, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Woodham, W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Pareizs, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Edwards, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Howe, A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-11-15

    To support resolution of Potential Inadequacies in the Safety Analysis for the Savannah River Site (SRS) Tank Farm, Savannah River National Laboratory conducted research to determine the thermolytic hydrogen generation rate (HGR) with simulated and actual waste. Gas chromatography methods were developed and used with air-purged flow systems to quantify hydrogen generation from heated simulated and actual waste at rates applicable to the Tank Farm Documented Safety Analysis (DSA). Initial simulant tests with a simple salt solution plus sodium glycolate demonstrated the behavior of the test apparatus by replicating known HGR kinetics. Additional simulant tests with the simple salt solution excluding organics apart from contaminants provided measurement of the detection and quantification limits for the apparatus with respect to hydrogen generation. Testing included a measurement of HGR on actual SRS tank waste from Tank 38. A final series of measurements examined HGR for a simulant with the most common SRS Tank Farm organics at temperatures up to 140 °C. The following conclusions result from this testing.

  19. Investigating and modeling the pyrolysis kinetic of leaves and stems of pistachio trees for biofuel production

    Directory of Open Access Journals (Sweden)

    M Ostad Hoseini

    2016-09-01

    Full Text Available Introduction The lignocelluloses materials have high potential for producing various types of biofuels. These materials include various parts of plants, especially leaves and stems that are left without a specific usage after annual pruning. These residues can be used through slow or fast pyrolysis process for production of liquid and gaseous biofuels. The slow pyrolysis is taking place at temperatures below 500°C while fast pyrolysis process takes place at a temperature above 700°C. Various studies on production of biofuels from plant residues have shown that the temperature, heating rate and the resident time of pyrolysis process are the main factors that affect the final product quality. At present time, in Iran, there are more than 360 thousands hectares of pistachio growing fields which annually produce over 215 thousands metric tons residues which are mainly leaves and stems. The main objective of this study was to measure the heating properties of the powders prepared from the leaves and the stem of pistachio trees. These properties include higher heating value (HHV, lower heating value (LHV and thermal gravimetric analysis (TGA of the powders. Then the powders were separately pyrolysed and the kinetic of the pyrolysis process for producing charcoal from them was investigated. Materials and Methods In this research, leaves and stems of pistachio trees were initially analyzed to determine their chemical constituents including moisture content, volatile compounds, carbon (C, hydrogen (H, nitrogen (N, sulfur (S and oxygen (O content. Using these constituents the height heating value and low heating value for the leaves and the stems were determined. The thermal gravimetric analysis (TGA of the powders was made to select a proper heating temperature for pyrolysis of the powders. In each experiment about 10 g of powder powders were pyrolyzed to produce char. Based on TGA results, the pyrolysis experiments were performed at 350, 400, 450 and

  20. Simulation Investigation on Combustion Characteristics in a Four-Point Lean Direct Injection Combustor with Hydrogen/Air

    Directory of Open Access Journals (Sweden)

    Jianzhong Li

    2017-06-01

    Full Text Available To investigate the combustion characteristics in multi-point lean direct injection (LDI combustors with hydrogen/air, two swirl–venturi 2 × 2 array four-point LDI combustors were designed. The four-point LDI combustor consists of injector assembly, swirl–venturi array and combustion chamber. The injector, swirler and venturi together govern the rapid mixing of hydrogen and air to form the mixture for combustion. Using clockwise swirlers and anticlockwise swirlers, the co-swirling and count-swirling swirler arrays LDI combustors were achieved. Using Reynolds-Averaged Navier–Stokes (RANS code for steady-state reacting flow computations, the four-point LDI combustors with hydrogen/air were simulated with an 11 species and 23 lumped reaction steps H2/Air reaction mechanism. The axial velocity, turbulence kinetic energy, total pressure drop coefficient, outlet temperature, mass fraction of OH and emission of pollutant NO of four-point LDI combustors, with different equivalence ratios, are here presented and discussed. As the equivalence ratios increased, the total pressure drop coefficient became higher because of increasing heat loss. Increasing equivalence ratios also corresponded with the rise in outlet temperature of the four-point LDI combustors, as well as an increase in the emission index of NO EINO in the four-point LDI combustors. Along the axial distance, the EINO always increased and was at maximum at the exit of the dump. Along the chamber, the EINO gradually increased, maximizing at the exit of chamber. The total temperature of four-point LDI combustors with different equivalence ratios was identical to the theoretical equilibrium temperature. The EINO was an exponential function of the equivalence ratio.

  1. In-situ investigation of hydrogen evolution behavior in vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Wei, L.; Zhao, T.S.; Xu, Q.; Zhou, X.L.; Zhang, Z.H.

    2017-01-01

    Highlights: • An in-situ method to investigate hydrogen evolution in VRFBs is developed. • The rate of hydrogen evolution during battery operation is quantified. • The gas evolution behaviors in the charge process of VRFBs are observed. - Abstract: In this work, we conceived and fabricated a three-electrode electrochemical cell and transparent vanadium redox flow battery to in-situ investigate the hydrogen evolution reaction during battery operation. Experimental results show that operating temperature has a strong influence on the HER rate. In particular, compared with V"3"+ reduction reaction, HER is more sensitive to temperature variation. It is also found that, contrary to the conventional wisdom that side reactions occur at the late stage of the charge process, H_2 evolves at a relatively low SOC. About 0.26 and 1.94 mL H_2 were collected at an early (SOC lower than 20%) and end of the charge process, respectively, suggesting that attention to the hydrogen formation at the negative electrode in the early charge process should also be paid to during long-term battery operations. Moreover, the produced hydrogen gas at the negative side prefers to form macroscopically observable bubbles onto the electrode surface, covering the active sites for vanadium redox reactions, while oxygen evolution (including CO_2 production) at the positive side corrodes electrode surface and introduces certain oxygen-containing functional groups.

  2. Reaction of hydrogen with Ag(111): binding states, minimum energy paths, and kinetics.

    Science.gov (United States)

    Montoya, Alejandro; Schlunke, Anna; Haynes, Brian S

    2006-08-31

    The interaction of atomic and molecular hydrogen with the Ag(111) surface is studied using periodic density functional total-energy calculations. This paper focuses on the site preference for adsorption, ordered structures, and energy barriers for H diffusion and H recombination. Chemisorbed H atoms are unstable with respect to the H(2) molecule in all adsorption sites below monolayer coverage. The three-hollow sites are energetically the most favorable for H chemisorption. The binding energy of H to the surface decreases slightly up to one monolayer, suggesting a small repulsive H-H interaction on nonadjacent sites. Subsurface and vacancy sites are energetically less favorable for H adsorption than on-top sites. Recombination of chemisorbed H atoms leads to the formation of gas-phase H(2) with no molecular chemisorbed state. Recombination is an exothermic process and occurs on the bridge site with a pronounced energy barrier. This energy barrier is significantly higher than that inferred from experimental temperature-programmed desorption (TPD) studies. However, there is significant permeability of H atoms through the recombination energy barrier at low temperatures, thus increasing the rate constant for H(2) desorption due to quantum tunneling effects, and improving the agreement between experiment and theory.

  3. Mechanism and kinetics of the electrocatalytic reaction responsible for the high cost of hydrogen fuel cells.

    Science.gov (United States)

    Cheng, Tao; Goddard, William A; An, Qi; Xiao, Hai; Merinov, Boris; Morozov, Sergey

    2017-01-25

    The sluggish oxygen reduction reaction (ORR) is a major impediment to the economic use of hydrogen fuel cells in transportation. In this work, we report the full ORR reaction mechanism for Pt(111) based on Quantum Mechanics (QM) based Reactive metadynamics (RμD) simulations including explicit water to obtain free energy reaction barriers at 298 K. The lowest energy pathway for 4 e - water formation is: first, *OOH formation; second, *OOH reduction to H 2 O and O*; third, O* hydrolysis using surface water to produce two *OH and finally *OH hydration to water. Water formation is the rate-determining step (RDS) for potentials above 0.87 Volt, the normal operating range. Considering the Eley-Rideal (ER) mechanism involving protons from the solvent, we predict the free energy reaction barrier at 298 K for water formation to be 0.25 eV for an external potential below U = 0.87 V and 0.41 eV at U = 1.23 V, in good agreement with experimental values of 0.22 eV and 0.44 eV, respectively. With the mechanism now fully understood, we can use this now validated methodology to examine the changes upon alloying and surface modifications to increase the rate by reducing the barrier for water formation.

  4. Hydrogenation of the alpha,beta-Unsaturated Aldehydes Acrolein, Crotonaldehyde, and Prenal over Pt Single Crystals: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

    Energy Technology Data Exchange (ETDEWEB)

    Kliewer, C.J.; Somorjai, G.A.

    2008-11-26

    Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three {alpha},{beta}-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr aldehyde, 100 Torr hydrogen) in the temperature range of 295K to 415K. SFG-VS data showed that acrolein has mixed adsorption species of {eta}{sub 2}-di-{sigma}(CC)-trans, {eta}{sub 2}-di-{sigma}(CC)-cis as well as highly coordinated {eta}{sub 3} or {eta}{sub 4} species. Crotonaldehyde adsorbed to Pt(111) as {eta}{sub 2} surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the {eta}{sub 2} adsorption species, and became more highly coordinated as the temperature was raised to 415K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation 'cracking' product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotylalcohol.

  5. Testing machine for fatigue crack kinetic investigation in specimens under bending

    International Nuclear Information System (INIS)

    Panasyuk, V.V.; Ratych, L.V.; Dmytrakh, I.N.

    1978-01-01

    A kinematic diagram of testing mashine for the investigation of fatigue crack kinetics in prismatic specimens, subjected to pure bending is described. Suggested is a technique of choosing an optimum ratio of the parameters of ''the testing machine-specimen'' system, which provide the stabilization of the stress intensity coefficient for a certain region of crack development under hard loading. On the example of the 40KhS and 15Kh2MFA steel specimens the pliability of the machine constructed according to the described diagram and designed for the 30ONxm maximum bending moment. The results obtained can be used in designing of the testing machines for studying pure bending under hard loading and in choosing the sizes of specimens with rectangular cross sections for investigations into the kinetics of the fatigue crack

  6. Investigation the Kinetic Models of Biological Removal of Petroleum Contaminated Soil Around Oil Pipeline Using Ryegrass

    Directory of Open Access Journals (Sweden)

    Elham Ghaheri

    2014-04-01

    Full Text Available The industrial revolution of the past century has resulted in significant damage to environmental resources such as air, water and soil. Petroleum contamination of soil is a serious problem throughout the oil producer countries. Remediation of petroleum contamination of soils is generally a slow and expensive process. Phytoremediation is a potentially less-damaging, cost-effective, but needs longer-term for remediation of contaminated land compared to the alternative methods. In this study the kinetics of petroleum hydrocarbon contaminated soils in Khozestan were investigated. For this paper Ryegrass (Lolium perenne plant selected and the decline of total petroleum hydrocarbon (TPH was analyzed after growth stage, every 10 days up to 90 days. The results of TPH concentration was fitted with zero-order kinetic, first-order kinetic and Higuchi model. The result indicated that degradation of TPH with presence of plants as a function of time was well fitted with the first-order kinetic model. The first-order rate constants (K and half-lives (T1/2 for TPH degradation were 0.0098 1/day and 71 day; respectively. The results of phytoremediation showed that there were 65% decreases in TPH concentration with Ryegrass during the 17 weeks.

  7. Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

    OpenAIRE

    Rizvi, Masood Ahmad; Teshima, Norio; Maqsood, Syed Raashid; Akhoon, Showket Ahmad; Peerzada, Ghulam Mustafa

    2015-01-01

    Transition metal ions in their free state bring unwanted biological oxidations generating oxidative stress. The ligand modulated redox potential can be indispensable in prevention of such oxidative stress by blocking the redundant bio-redox reactions. In this study we investigated the comparative ligand effect on the thermo-kinetic aspects of biologically important cysteine iron (III) redox reaction using spectrophotometric and potentiometric methods. The results were corroborated...

  8. EXPERIMENTAL INVESTIGATION OF IRRADIATION-DRIVEN HYDROGEN ISOTOPE FRACTIONATION IN ANALOGS OF PROTOPLANETARY HYDROUS SILICATE DUST

    Energy Technology Data Exchange (ETDEWEB)

    Roskosz, Mathieu; Remusat, Laurent [IMPMC, CNRS UMR 7590, Sorbonne Universités, Université Pierre et Marie Curie, IRD, Muséum National d’Histoire Naturelle, CP 52, 57 rue Cuvier, Paris F-75231 (France); Laurent, Boris; Leroux, Hugues, E-mail: mathieu.roskosz@mnhn.fr [Unité Matériaux et Transformations, Université Lille 1, CNRS UMR 8207, Bâtiment C6, F-59655 Villeneuve d’Ascq (France)

    2016-11-20

    The origin of hydrogen in chondritic components is poorly understood. Their isotopic composition is heavier than the solar nebula gas. In addition, in most meteorites, hydrous silicates are found to be lighter than the coexisting organic matter. Ionizing irradiation recently emerged as an efficient hydrogen fractionating process in organics, but its effect on H-bearing silicates remains essentially unknown. We report the evolution of the D/H of hydrous silicates experimentally irradiated by electrons. Thin films of amorphous silica, amorphous “serpentine,” and pellets of crystalline muscovite were irradiated at 4 and 30 keV. For all samples, irradiation leads to a large hydrogen loss correlated with a moderate deuterium enrichment of the solid residue. The entire data set can be described by a Rayleigh distillation. The calculated fractionation factor is consistent with a kinetically controlled fractionation during the loss of hydrogen. Furthermore, for a given ionizing condition, the deuteration of the silicate residues is much lower than the deuteration measured on irradiated organic macromolecules. These results provide firm evidence of the limitations of ionizing irradiation as a driving mechanism for D-enrichment of silicate materials. The isotopic composition of the silicate dust cannot rise from a protosolar to a chondritic signature during solar irradiations. More importantly, these results imply that irradiation of the disk naturally induces a strong decoupling of the isotopic signatures of coexisting organics and silicates. This decoupling is consistent with the systematic difference observed between the heavy organic matter and the lighter water typically associated with minerals in the matrix of most carbonaceous chondrites.

  9. Thermoanalytical investigation of the hydrogen absorption behaviour of Sm{sub 2}Fe{sub 17-x}Ga{sub x} at high hydrogen pressures

    Energy Technology Data Exchange (ETDEWEB)

    Handstein, A.; Kubis, M.; Gebel, B.; Mueller, K.-H.; Schultz, L. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe; Gutfleisch, O.; Harris, I.R. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe]|[Birmingham Univ. (United Kingdom). School of Metallurgy and Materials

    1998-07-01

    The complete disproportionation of Sm{sub 2}Fe{sub 17-x}Ga{sub x} during annealing in hydrogen is hindered due to an increased stability of the compounds with a higher Ga content (x {>=} 1). Therefore the HD process as the first step of HDDR (hydrogenation-disproportionation-desorption-recombination) has to be carried out at a high hydrogen pressure for x {>=} 1. The hydrogen absorption behaviour of Sm{sub 2}Fe{sub 17-x}Ga{sub x} (x = 0, 0.5, 1 and 2) was investigated by means of hydrogen differential thermal analysis (HDTA) and high pressure differential scanning calorimetry (HPDSC) at hydrogen pressures up to 70 bar. A dependency of hydrogenation and disproportionation temperatures on hydrogen pressure and Ga content was found. The comparison with other substituents (M = Al and Si) instead of M = Ga showed an increased stability of Sm{sub 2}Fe{sub 17-x}M{sub x} compounds against disproportionation by hydrogen in the sequence Al, Ga and Si. The Curie temperatures of the interstitially hydrogenated Th{sub 2}Zn{sub 17}-type materials increase with the hydrogen pressure. In order to produce coercive and thermally stable Sm{sub 2}Fe{sub 15}Ga{sub 2}C{sub y} powder by means of the HDDR process, we recombined material disproportionated at different hydrogen pressures. Preliminary results of magnetic properties of this HDDR treated and gas-carburized Sm{sub 2}Fe{sub 15}Ga{sub 2}C{sub y} are discussed. (orig.)

  10. STUDY OF HYDROGEN SULFIDE REMOVAL FROM GROUNDWATER

    Directory of Open Access Journals (Sweden)

    T. Lupascu

    2013-06-01

    Full Text Available The process of the hydrogen sulfide removal from the underground water of the Hancesti town has been investigated. By oxygen bubbling through the water containing hydrogen sulfide, from the Hancesti well tube, sulfur is deposited in the porous structure of studied catalysts, which decreases their catalytic activity. Concomitantly, the process of adsorption / oxidation of hydrogen sulfide to sulfate take place. The kinetic research of the hydrogen sulfide removal from the Hancesti underground water, after its treatment by hydrogen peroxide, proves greater efficiency than in the case of modified carbonic adsorbents. As a result of used treatment, hydrogen sulfide is completely oxidized to sulfates

  11. Kinetics of exchange between zero-, one-, and two-hydrogen-bonded states of methyl and ethyl acetate in methanol.

    Science.gov (United States)

    Chuntonov, Lev; Pazos, Ileana M; Ma, Jianqiang; Gai, Feng

    2015-03-26

    It has recently been shown that the ester carbonyl stretching vibration can be used as a sensitive probe of local electrostatic field in molecular systems. To further characterize this vibrational probe and extend its potential applications, we studied the kinetics of chemical exchange between differently hydrogen-bonded (H-bonded) ester carbonyl groups of methyl acetate (MA) and ethyl acetate (EA) in methanol. We found that, while both MA and EA can form zero, one, or two H-bonds with the solvent, the population of the 2hb state in MA is significantly smaller than that in EA. Using a combination of linear and nonlinear infrared measurements and numerical simulations, we further determined the rate constants for the exchange between these differently H-bonded states. We found that for MA the chemical exchange reaction between the two dominant states (i.e., 0hb and 1hb states) has a relaxation rate constant of 0.14 ps(-1), whereas for EA the three-state chemical exchange reaction occurs in a predominantly sequential manner with the following relaxation rate constants: 0.11 ps(-1) for exchange between 0hb and 1hb states and 0.12 ps(-1) for exchange between 1hb and 2hb states.

  12. Surface kinetics for catalytic combustion of hydrogen-air mixtures on platinum at atmospheric pressure in stagnation flows

    Science.gov (United States)

    Ikeda, H.; Sato, J.; Williams, F. A.

    1995-03-01

    Experimental studies of the combustion of premixed hydrogen-air mixtures impinging on the surface of a heated platinum plate at normal atmospheric pressure were performed and employed to draw inferences concerning surface reaction mechanisms and rate parameters applicable under practical conditions of catalytic combustion. Plate and gas temperatures were measured by thermocouples, and concentration profiles of major stable species in the gas were measured by gas-chromatographic analyses of samples withdrawn by quartz probes. In addition, ignition and extinction phenomena were recorded and interpreted with the aid of a heat balance at the surface and a previous flow-field analysis of the stagnation-point boundary layer. From the experimental and theoretical results, conclusions were drawn concerning the surface chemical-kinetic mechanisms and values of the elementary rate parameters that are consistent with the observations. In particular, the activation energy for the surface oxidation step H + OH → H 2O is found to be appreciably less at these high surface coverages than in the low-coverage limit.

  13. Investigations of the Formation of Molecular Hydrogen on Dust Grain Analogues

    Science.gov (United States)

    Vidali, Gianfranco; Roser, Joseph E.; Manico, Giulio; Pirronello, Valerio

    2002-01-01

    In the last four years we have been working to investigate the formation of molecular hydrogen on surfaces of materials of astrophysical interest, such as silicates, carbonaceous particles and ices, and in conditions approximating the ones present in a variety of astrophysical environments. Our experimental studies - the first of their kind and complemented with computer simulations and theoretical analyses - have given not only hydrogen recombination rates under different ISM conditions, but they have also offered new insights into this fundamental astrophysical problem. Here we summarize our experimental methods and most significant results.

  14. Kinetic investigation of vanadium (V)/(IV) redox couple on electrochemically oxidized graphite electrodes

    International Nuclear Information System (INIS)

    Wang, Wenjun; Wei, Zengfu; Su, Wei; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei; Zeng, Chaoliu

    2016-01-01

    Highlights: • The VO_2"+/VO"2"+ redox reaction of the electrode could be facilitated to some extent with the increasing anodic corrosion. • A real reaction kinetic equation for the oxidation of VO"2"+ on the electrochemically oxidized electrode has been firstly obtained. • The establishment of the kinetic equation is conducive to predict polarization behaviors of the electrodes in engineering application. - Abstract: The morphology, surface composition, wettability and the kinetic parameters of the electrochemically oxidized graphite electrodes obtained under different anodic polarization conditions have been examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurements, steady-state polarization and cyclic voltammetry (CV) tests, with an attempt to investigate the inherent correlation between the physicochemical properties and the kinetic characteristics for carbon electrodes used in an all-vanadium redox flow battery (VRFB). When the anodic polarization potential raises up to 1.8 V vs. SCE, the anodic corrosion of the graphite might happen and a large number of oxygen-containing functional groups generate. The VO_2"+/VO"2"+ redox reaction can be facilitated and the reaction reversibility tends to become better with the increasing anodic potential, possibly owing to the increased surface oxides and the resulting improved wettability of the electrode. Based on this, a real reaction kinetic equation for the oxidation of VO"2"+ has been obtained on the electrode polarized at 1.8 V vs. SCE and it can be also well used to predict the polarization behavior of the oxidized electrode in vanadium (IV) acidic solutions.

  15. Theoretical and experimental investigation of the thermodynamic and kinetic nitrogen absorption by liquid alloys

    Energy Technology Data Exchange (ETDEWEB)

    Grigorenko, G.M.; Pomarin, Yu.M.; Orlovsky, V.Yu. [Natsional' na Akademyiya Nauk Ukrayini, Kiev (Ukraine). E.O. Paton Inst. of Electrical Welding

    1999-07-01

    The work was performed within the framework of the Ukrainian-French program of cooperation in the field of metal of high inclusion and was dedicated to joint fundamental investigation of thermodynamics and kinetics of nitrogen absorption by the Ni-20%Cr liquid alloy. The comparative investigations of kinetic absorption of nitrogen from the gas phase were performed by the method of levitation melting within the temperature range of 1600-1800 C in the atmosphere of pure nitrogen. Using the method of mathematical statistics and experimental Cp values at the different temperatures, the temperature dependence of the equilibrium constant of nitrogen solution reaction in the Ni-20%Cr alloy was obtained (lgK{sub N}=1284/T-1.94). Theoretical and graphical analysis of the experimental data allowed to make the conclusion that the absorption nitrogen process is controlled by the general kinetic equation of the first degree. Using of the aforementioned results the mass transfer factors were calculated with the different temperature and were obtained their mathematical description ({beta}{sub N}{sup Ni-Cr}=-454/T+0.285). (orig.)

  16. The silver catalyst process for converting methanol to formaldehyde - kinetic investigations

    Energy Technology Data Exchange (ETDEWEB)

    Panzer, E.; Emig, G. [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Technische Chemie 1

    1998-12-31

    In pre-experiments a tubular reactor was checked whether it is suitable for kinetic measurement on the system of the silver-catalysed partial oxidation of methanol to formaldehyde. Detrimental effects of heat-transfer and mass-transfer on the experimental results were ruled out. Investigations on the characteristics of the reaction showed that it is possible to manipulate the composition of the product mixture by changing the inlet concentration of the reactants. A modified power-law model was established to describe the reaction kinetics. It considers the preadsorption step of oxygen on the catalysts surface and fits the experimental data quite well. During the rapid oxidation the catalysts surface undergoes a drastic change. It gets coarse and has an adsorption capacity of 11 m{sup 2}/g after being exposed to the reaction mixture. (orig.)

  17. Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

    Directory of Open Access Journals (Sweden)

    Masood Ahmad Rizvi

    2015-03-01

    Full Text Available Transition metal ions in their free state bring unwanted biological oxidations generating oxidative stress. The ligand modulated redox potential can be indispensable in prevention of such oxidative stress by blocking the redundant bio-redox reactions. In this study we investigated the comparative ligand effect on the thermo-kinetic aspects of biologically important cysteine iron (III redox reaction using spectrophotometric and potentiometric methods. The results were corroborated with the complexation effect on redox potential of iron(III-iron(II redox couple. The selected ligands were found to increase the rate of cysteine iron (III redox reaction in proportion to their stability of iron (II complex (EDTA < terpy < bipy < phen. A kinetic profile and the catalytic role of copper (II ions by means of redox shuttle mechanism for the cysteine iron (III redox reaction in presence of 1,10-phenanthroline (phen ligand is also reported.

  18. A fast-kinetic investigation of the redox chemistry of iridium chloride complexes using pulse radiolysis

    International Nuclear Information System (INIS)

    Crawford, C.L.; Gholami, M.R.; Roberts, S.L.; Hanrahan, R.J.

    1992-01-01

    Reactions initiated by OH radicals or e aq - in aqueous IrCl 6 3- solutions were studied by electron pulse radiolysis using a 600 keV Febetron electron accelerator. Solutions of IrCl 6 3- were made basic by adding Na 2 CO 3 ; using the carbonate competition method, we find the rate constant for the reaction of OH . with IrCl 6 3- to be 4.7 x 10 9 M -1 s -1 . The product IrCl 6 2- disappears rapidly in N 2 O-saturated basic solution or in neutral N 2 -saturated solution (N 2 O absent) but is nearly inert in neutral solution with N 2 O present. We find that IrCl 6 2- reacts rapidly with hydrogen peroxide in basic media, as confirmed on the benchtop and by stopped-flow kinetics. We therefore infer that reaction with HO 2 - may account for the loss of IrCl 6 2- under basic conditions. Since e aq - reduces Ir(III) chloride to the Ir(II) state with a rate constant of 6.1 x 10 9 M -1 s -1 , we suggest that loss of Ir(IV) in neutral deaerated solution without added N 2 O may involve electron transfer from Ir(II). Loss of Ir (IV) in aerated solution is attributed to reduction by the superoxide ion, O 2 - . Kinetic simulation of the system on the model described gives good agreement with our experimental results. (author)

  19. Synthesis and electrochemical properties of binary MgTi and ternary MgTiX (X=Ni, Si) hydrogen storage alloys

    NARCIS (Netherlands)

    Gobichettipalayam Manivasagam, T.; Iliksu, M.; Danilov, D.L.; Notten, P.H.L.

    2017-01-01

    Mg-based hydrogen storage alloys are promising candidate for many hydrogen storage applications because of the high gravimetric hydrogen storage capacity and favourable (de)hydrogenation kinetics. In the present study we have investigated the synthesis and electrochemical hydrogen storage properties

  20. Influence of γ-irradiation on the transport kinetics of hydrogen in pre-transition oxidized Zircaloy-4 at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Frantz A., E-mail: frantz.martin@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d' Etude de la Corrosion Aqueuse, F-91191 Gif-sur-Yvette (France); Dauvois, Vincent, E-mail: vincent.dauvois@cea.fr [CEA, DEN, DPC, SECR, Laboratoire de Radiolyse et de la Matière Organique, F-91191 Gif-sur-Yvette (France); Esnouf, Stéphane, E-mail: stephane.esnouf@cea.fr [CEA, DEN, DPC, SECR, Laboratoire de Radiolyse et de la Matière Organique, F-91191 Gif-sur-Yvette (France); CEA, DSM, IRAMIS, LIDYL, PCR, F-91191 Gif-sur-Yvette (France); Fourdrin, Chloé, E-mail: chloe.fourdrin@culture.gouv.fr [CEA, DEN, DPC, SECR, Laboratoire de Radiolyse et de la Matière Organique, F-91191 Gif-sur-Yvette (France); Jomard, François, E-mail: francois.jomard@uvsq.fr [CNRS/UVSQ, UMR 8635, GEMAC, 45 avenue des Etats Unis – Bâtiment Fermat, F-78035 Versailles (France); Chêne, Jacques, E-mail: chene_jacques@orange.fr [CNRS/CEA, UMR 8587, LECA – CEA, Saclay, F-91191 Gif-sur-Yvette (France)

    2015-10-15

    In a context of nuclear fuel reprocessing, the free-of-fuel hulls and ends of cladding tubes are compacted. The possibility of hydrogen degasing or absorption from/into these tubes has been studied with and without gamma irradiation at 293 K by means of deuterium as isotopic tracer for hydrogen. Under irradiation, as without, the hydrides present in the Zircaloy-4 hulls seem stable. The oxide layer present at the surface of the hulls allows a slow diffusion of deuterium, and the irradiation appeared to have no specific effect on the diffusion process: in both cases, hydrogen diffusion coefficients of the order of 5·10{sup −18} cm{sup 2} s{sup −1} have been found. The subsurface activity of deuterium is increased by one order of magnitude at least under irradiation, probably due to an activation of the dissociation/absorption kinetic steps. - Highlights: • Hydrogen diffusion coefficients at RT in zirconia grain boundaries were determined. • γ irradiation increases the hydrogen subsurface activity when exposed to H{sub 2} gas. • The dense thin zirconia film is not altered much by HNO{sub 3} exposure at 90 °C for 24 h. • Hydrogen desorption from Zr hydrides was studied at room temperature under γ rays.

  1. A DFT investigation on group 8B transition metal-doped silicon carbide nanotubes for hydrogen storage application

    Science.gov (United States)

    Tabtimsai, Chanukorn; Ruangpornvisuti, Vithaya; Tontapha, Sarawut; Wanno, Banchob

    2018-05-01

    The binding of group 8B transition metal (TMs) on silicon carbide nanotubes (SiCNT) hydrogenated edges and the adsorption of hydrogen molecule on the pristine and TM-doped SiCNTs were investigated using the density functional theory method. The B3LYP/LanL2DZ method was employed in all calculations for the considered structural, adsorption, and electronic properties. The Os atom doping on the SiCNT is found to be the strongest binding. The hydrogen molecule displays a weak interaction with pristine SiCNT, whereas it has a strong interaction with TM-doped SiCNTs in which the Os-doped SiCNT shows the strongest interaction with the hydrogen molecule. The improvement in the adsorption abilities of hydrogen molecule onto TM-doped SiCNTs is due to the protruding structure and the induced charge transfer between TM-doped SiCNT and hydrogen molecule. These observations point out that TM-doped SiCNTs are highly sensitive toward hydrogen molecule. Moreover, the adsorptions of 2-5 hydrogen molecules on TM-doped SiCNT were also investigated. The maximum storage number of hydrogen molecules adsorbed on the first layer of TM-doped SiCNTs is 3 hydrogen molecules. Therefore, TM-doped SiCNTs are suitable to be sensing and storage materials for hydrogen gas.

  2. Surface analytical investigations of the interaction between the getter material ZrCo and hydrogen and the influence of different contamination gases on the hydrogen storage capacity

    International Nuclear Information System (INIS)

    Glasbrenner, H.

    1991-11-01

    In this work the results of surface analytical investigations of the alloy ZrCo used for hydrogen storage as well as of the interaction of the alloy with hydrogen and various contamination gases present in a nuclear fusion reactor will be presented and discussed with respect to the application of ZrCo as getter material for tritium. The characterization of the ZrCo alloy showed that on the surface a stable ZrO 2 -layer is formed, which is, however, inhomogeneous. On the phase boundary solid / gas of samples exposed to hydrogen up to the stoichiometrical composition ZrCoH 2.8 a Co enrichment was observed. If the alloy ZrCo is activated before hydrogen take-up in the same way as other getter materials by heating under vacuum, the hydrogenation occurs faster and nearly complete. Zirconium is the alloy component responsible for the hydrogen storage. If a gas reacts nearly exclusively with the alloy component Co, a smaller decrease in the hydrogen storage capacity will be noticed. By exposition to CO and CO 2 mainly compounds with cobalt are formed. However, if the gas produces compounds with Zr like carbide, nitride, or oxide, the result is a strong decrease of the hydrogen storage capacity of the getter. (orig./MM) [de

  3. Sum Frequency Generation Vibrational Spectroscopy and Kinetic Study of 2-Methylfuran and 2,5-Dimethylfuran Hydrogenation over 7 nm Platinum Cubic Nanoparticles

    KAUST Repository

    Aliaga, Cesar

    2011-04-28

    Sum frequency generation vibrational spectroscopy and kinetic measurements obtained from gas chromatography were used to study the adsorption and hydrogenation of 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) over cubic Pt nanoparticles of 7 nm average size, synthesized by colloidal methods and cleaned by ultraviolet light and ozone treatment. Reactions carried out at atmospheric pressure in the temperature range of 20-120 °C produced dihydro and tetrahydro species, as well as ring-opening products (alcohols) and ring-cracking products, showing high selectivity toward ring opening throughout the entire temperature range. The aromatic rings (MF and DMF) adsorbed parallel to the nanoparticle surface. Results yield insight into various surface reaction intermediates and the reason for the significantly lower selectivity for ring cracking in DMF hydrogenation compared to MF hydrogenation. © 2011 American Chemical Society.

  4. Kinetics of methane decomposition to CO{sub x}-free hydrogen and carbon nanofiber over Ni-Cu/MgO catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Borghei, Maryam; Karimzadeh, Ramin [Chemical Engineering Department, Tarbiat Modares University, Tehran (Iran); Rashidi, Alimorad; Izadi, Nosrat [Research Center of Nanotechnology, Research Institute of Petroleum Industry, Tehran (Iran)

    2010-09-15

    Kinetic modeling of methane decomposition to CO{sub x}-free hydrogen and carbon nanofiber has been carried out in the temperature range 550-650 C over Ni-Cu/MgO catalyst from CH{sub 4}-H{sub 2} mixtures at atmospheric pressure. Assuming the different mechanisms of the reaction, several kinetic models were derived based on Langmuir-Hinshelwood type. The optimum value of kinetic parameters has been obtained by Genetic Algorithm and statistical analysis has been used for the model discrimination. The suggested kinetic model relates to the mechanism when the dissociative adsorption of methane molecule is the rate-determining stage and the estimated activation energy is 50.4 kJ/mol in agreement with the literature. The catalyst deactivation was found to be dependent on the time, reaction temperature, and partial pressures of methane and hydrogen. Inspection of the behavior of the catalyst activity in relation to time, led to a model of second order for catalyst deactivation. (author)

  5. Thermodynamic investigation and environment impact assessment of hydrogen production from steam reforming of poultry tallow

    International Nuclear Information System (INIS)

    Hajjaji, Noureddine

    2014-01-01

    Highlights: • Thermodynamic analysis and environmental impact assessment of H 2 production system. • Thermodynamic analysis identifies optimal conditions for H 2 production. • LCA is applied to evaluate the environmental impacts of H 2 production system. • Inventories data are derived from process simulation and from literature review. • Thermal energy process is the main contributor to the environmental impact. - Abstract: In this research, various assessment tools are applied to comprehensively investigate hydrogen production from steam reforming of poultry tallow (PT). These tools investigate the chemical reactions, design and simulate the entire hydrogen production process, study the energetic performance and perform an environment impact assessment using life cycle assessment (LCA) methodology. The chemical reaction investigation identifies thermodynamically optimal operating conditions at which PT may be converted to hydrogen via the steam reforming process. The synthesis gas composition was determined by simulations to minimize the Gibbs free energy using the Aspen Plus™ 10.2 software. These optimal conditions are, subsequently, used in the design and simulation of the entire PT-to-hydrogen process. LCA is applied to evaluate the environmental impacts of PT-to-hydrogen system. The system boundaries include rendering and reforming along with the required transportation process. The reforming inventories data are derived from process simulation in Aspen Plus™, whereas the rendering data are adapted from a literature review. The life cycle inventories data of PT-to-hydrogen are computationally implemented into SimaPro 7.3. A set of seven relevant environmental impact categories are evaluated: global warming, abiotic depletion, acidification, eutrophication, ozone layer depletion, photochemical oxidant formation, and cumulative non-renewable fossil and nuclear energy demand. The results are subject to a systematic sensitivity analysis and compared

  6. A model stomach system to investigate disintegration kinetics of solid foods during gastric digestion.

    Science.gov (United States)

    Kong, F; Singh, R P

    2008-06-01

    Knowledge of the disintegration kinetics of food particulates in the human stomach is essential for assessing the bioaccessibility of nutrients in solid foods and understanding stomach emptying. The objective of this study was to develop a model stomach system and to investigate the kinetics of food disintegration. Our system consisted mainly of a turntable and a jacketed glass chamber containing simulated gastric juice in which plastic beads were added to simulate food particulates as well as provide a suitable mechanical destructive force on food samples. The mechanical force on the samples was simultaneously measured using the load cell of a TA-XT2 texture analyzer. Cylindrical carrots and ham samples were used as representative foods. The system is capable of simulating the in vivo stomach in terms of providing a wide range of continuous and periodic forces comparable to those measured in vivo. The modified power exponential function of the form y(t)= 1 - (1 -e(-kt))(beta), where y(t) is the mass retention ratio at time t, provided a reasonable description for the disintegration performance of tested foods. The mass retention curve can be either a sigmoidal decay with an initial delay or an exponential decay, which are decided largely by the hardness of the foods during digestion and the extent of physical force acting on the foods. A good match was observed between the kinetics of food disintegration and in vivo stomach emptying.

  7. Curing kinetics of visible light curing dental resin composites investigated by dielectric analysis (DEA).

    Science.gov (United States)

    Steinhaus, Johannes; Hausnerova, Berenika; Haenel, Thomas; Großgarten, Mandy; Möginger, Bernhard

    2014-03-01

    During the curing process of light curing dental composites the mobility of molecules and molecule segments is reduced leading to a significant increase of the viscosity as well as the ion viscosity. Thus, the kinetics of the curing behavior of 6 different composites was derived from dielectric analysis (DEA) using especially redesigned flat sensors with interdigit comb electrodes allowing for irradiation at the top side and measuring the ion viscosity at the bottom side. As the ion viscosities of dental composites change 1-3 orders of magnitude during the curing process, DEA provides a sensitive approach to evaluate their curing behavior, especially in the phase of undisturbed chain growth. In order to determine quantitative kinetic parameters a kinetic model is presented and examined for the evaluation of the ion viscosity curves. From the obtained results it is seen that DEA might be employed in the investigation of the primary curing process, the quality assurance of ingredients as well as the control of processing stability of the light curing dental composites. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Continuous production of biodiesel under supercritical methyl acetate conditions: Experimental investigation and kinetic model.

    Science.gov (United States)

    Farobie, Obie; Matsumura, Yukihiko

    2017-10-01

    In this study, biodiesel production by using supercritical methyl acetate in a continuous flow reactor was investigated for the first time. The aim of this study was to elucidate the reaction kinetics of biodiesel production by using supercritical methyl. Experiments were conducted at various reaction temperatures (300-400°C), residence times (5-30min), oil-to-methyl acetate molar ratio of 1:40, and a fixed pressure of 20MPa. Reaction kinetics of biodiesel production with supercritical methyl acetate was determined. Finally, biodiesel yield obtained from this method was compared to that obtained with supercritical methanol, ethanol, and MTBE (methyl tertiary-butyl ether). The results showed that biodiesel yield with supercritical methyl acetate increased with temperature and time. The developed kinetic model was found to fit the experimental data well. The reactivity of supercritical methyl acetate was the lowest, followed by that of supercritical MTBE, ethanol, and methanol, under the same conditions. Copyright © 2017. Published by Elsevier Ltd.

  9. A comparative investigation of 18F kinetics in receptors: a compartment model analysis

    International Nuclear Information System (INIS)

    Tiwari, Anjani K.; Swatantra; Kaushik, A.; Mishra, A.K.

    2010-01-01

    Full text: Some authors reported that 18 F kinetics might be useful for evaluation of neuro receptors. We hypothesized that 18 F kinetics may show some information about neuronal damage, and each rate constant might have statistically significant correlation with WO function. The purpose of this study was to investigate 99m Tc MIBI kinetics through a compartment model analysis. Each rate constant from compartment analysis was compared with WO, T1/2, and (H/M) ratio in early and delayed phase. Different animal model were studied. After an injection the dynamic planar imaging was performed on a dual-headed digital gamma camera system for 30 minutes. An ROI was drawn manually to assess the global kinetics of 18 F. By using the time-activity curve (TAC) of ROI as a response tissue function and the TAC of Aorta as an input function, we analysed 18 F pharmacokinetics through a 2-compartment model. We defined k1 as influx rate constant, k2 as out flux rate constant and k3 as specific uptake rate constant. And we calculated k1/k2 as distribution volume (Vd), k1k3/k2 as specific uptake (SU), and k1k3/(k2+k3) as clearance. For non-competitive affinity studies of PET two modelling parameters distribution volume (DV) and Bmax / Kd are also calculated. Results: Statistically significant correlations were seen between k2 and T1/2 (P 18 F at the injection had relation to the uptake of it at 30 minutes and 2 hours after the injection. Furthermore, some indexes had statistically significant correlation with DV and Bmax. These compartment model approaches may be useful to estimate the other related studies

  10. Ab initio investigation on hydrogen adsorption capability in Zn and Cu-based metal organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Tanuwijaya, V. V., E-mail: viny.veronika@gmail.com [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung Jalan Ganeca 10 Gd. T.P. Rachmat, Bandung 40132 (Indonesia); Hidayat, N. N., E-mail: avantgarde.vee@gmail.com; Agusta, M. K., E-mail: kemal@fti.itb.ac.id; Dipojono, H. K., E-mail: dipojono@tf.itb.ac.id

    2015-09-30

    One of the biggest challenge in material technology for hydrogen storage application is to increase hydrogen uptake in room temperature and pressure. As a class of highly porous material, Metal-Organic Frameworks (MOF) holds great potential with its tunable structure. However, little is known about the effect of metal cluster to its hydrogen storage capability. Investigation on this matter has been carried out carefully on small cluster of Zn and Cu-based MOF using first principles method. The calculation of two distinct building units of MOFs, namely octahedral and paddle-wheel models, have been done with B3LYP density functional method using 6-31G(d,p) and LANL2DZ basis sets. From geometry optimization of Zn-based MOF linked by benzene-dicarboxylate (MOF-5), it is found that hydrogen tends to keep distance from metal cluster group and stays above benzene ring. In the other hand, hydrogen molecule prefers to stay atop of the exposed Cu atom in Cu-based MOF system linked by the same linker group (Cu-bdc). Calculated hydrogen binding enthalpies for Zn and Cu octahedral cages at ZnO{sub 3} sites are 1.64kJ/mol and 2.73kJ/mol respectively, while hydrogen binding enthalpies for Zn and Cu paddle-wheel cages calculated on top of metal atoms are found to be at 6.05kJ/mol and 6.10kJ/mol respectively. Major difference between Zn-MOF-5 and Cu-bdc hydrogen uptake performance might be caused by unsaturated metal sites present in Cu-bdc system and the influence of their geometric structures, although a small difference on binding energy in the type of transition metal used is also observed. The comparison between Zn and Cu-based MOF may contribute to a comprehensive understanding of metal clusters and the importance of selecting best transition metal for design and synthesis of metal-organic frameworks.

  11. Time-kill kinetic analysis of antimicrobial chemotherapy based on hydrogen peroxide photolysis against Streptococcus mutans biofilm.

    Science.gov (United States)

    Shirato, Midori; Nakamura, Keisuke; Kanno, Taro; Lingström, Peter; Niwano, Yoshimi; Örtengren, Ulf

    2017-08-01

    A recently developed antimicrobial technique utilizing hydroxyl radicals generated by hydrogen peroxide (H 2 O 2 ) photolysis represents a promising new therapy for preventing and treating dental caries. The present study compared the antimicrobial time-kill kinetics of H 2 O 2 photolysis, conventional antiseptics, and antimicrobial photodynamic therapy (aPDT) against biofilm-forming Streptococcus mutans (cariogenic bacteria) grown on hydroxyapatite disks. H 2 O 2 photolysis was performed by irradiating the biofilm immersed in 3% H 2 O 2 with 365-nm light-emitting diode (LED) light at an irradiance of 1000mW/cm 2 for up to 1.5min. Antiseptic treatments consisted of 0.2% chlorhexidine gluconate, 0.5% povidone-iodine, and 3% H 2 O 2 . The biofilm was immersed in each antiseptic for up to 4min. aPDT was performed by irradiating the biofilm immersed in 100μM methylene blue or toluidine blue O with 655-nm laser light at 1000mW/cm 2 for up to 4min. Based on the time-kill assay, the decimal reduction value (D-value) of each treatment was determined. With a D-value of 0.06min, H 2 O 2 photolysis exhibited the highest bactericidal effect against biofilm-forming S. mutans. In contrast, antiseptics and aPDT exerted a slower bactericidal effect, with D-values of 0.9-2.7min. In conclusion, the antimicrobial technique based on H 2 O 2 photolysis using 365-nm LED represents a strong adjunctive chemotherapy for dental caries treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. The interactive effect of fungicide residues and yeast assimilable nitrogen on fermentation kinetics and hydrogen sulfide production during cider fermentation.

    Science.gov (United States)

    Boudreau, Thomas F; Peck, Gregory M; O'Keefe, Sean F; Stewart, Amanda C

    2017-01-01

    Fungicide residues on fruit may adversely affect yeast during cider fermentation, leading to sluggish or stuck fermentation or the production of hydrogen sulfide (H 2 S), which is an undesirable aroma compound. This phenomenon has been studied in grape fermentation but not in apple fermentation. Low nitrogen availability, which is characteristic of apples, may further exacerbate the effects of fungicides on yeast during fermentation. The present study explored the effects of three fungicides: elemental sulfur (S 0 ) (known to result in increased H 2 S in wine); fenbuconazole (used in orchards but not vineyards); and fludioxonil (used in post-harvest storage of apples). Only S 0 led to increased H 2 S production. Fenbuconazole (≥0.2 mg L -1 ) resulted in a decreased fermentation rate and increased residual sugar. An interactive effect of yeast assimilable nitrogen (YAN) concentration and fenbuconazole was observed such that increasing the YAN concentration alleviated the negative effects of fenbuconazole on fermentation kinetics. Cidermakers should be aware that residual fenbuconazole (as low as 0.2 mg L -1 ) in apple juice may lead to stuck fermentation, especially when the YAN concentration is below 250 mg L -1 . These results indicate that fermentation problems attributed to low YAN may be caused or exacerbated by additional factors such as fungicide residues, which have a greater impact on fermentation performance under low YAN conditions. © 2016 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2016 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

  13. Investigation of cryogenic hydrogen storage on high surface area activated carbon. Equilibrium and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Paggiaro, Ricardo Gaspar

    2008-11-29

    This thesis investigates cryo-adsorptive systems for hydrogen storage for mobile applications. By means of macroscopic and microscopic balance models, an extensive analysis is carried out, including among others the investigation of the thermal effects during high-pressure system filling, venting losses during normal operation and inactivity, time-course of system pressure and temperature and gas delivery under various operating conditions. Model results were compared with experimental data, good agreement was obtained. The analysis also includes a comparison to other storage technologies such as cryo-compressed gas and liquefaction storage. The results show that cryo-adsorptive systems have storage characteristics comparable to compressed gas systems, but at a much lower pressure. They are also energetically more efficient than liquid hydrogen systems. However, the necessity of cryotemperatures and thermal management during operation and filling might limit their application. (orig.)

  14. Investigation on the reactions influencing biomass air and air/steam gasification for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, J.F.; Roman, S.; Bragado, D. [Departamento de Fisica Aplicada, University of Extremadura, 06071 (Spain); Calderon, M. [Departamento de Electronica e Ingenieria Electromecanica, University of Extremadura, 06071 (Spain)

    2008-08-15

    Hydrogen could be the energy carrier of the next world scene provided that its production, transportation and storage are solved. In this work the production of an hydrogen-rich gas by air/steam and air gasification of olive oil waste was investigated. The study was carried out in a laboratory reactor at atmospheric pressure over a temperature range of 700 - 900 C using a steam/biomass ratio of 1.2 w/w. The influence of the catalysts ZnCl{sub 2} and dolomite was also studied at 800 and 900 C. The solid, energy and carbon yield (%), gas molar composition and high heating value of the gas (kJ NL{sup -} {sup 1}), were determined for all cases and the differences between the gasification process with and without steam were established. Also, this work studies the different equilibria taking place, their predominance in each process and how the variables considered affect the final gas hydrogen concentration. The results obtained suggest that the operating conditions were optimized at 900 C in steam gasification (a hydrogen molar fraction of 0.70 was obtained at a residence time of 7 min). The use of both catalysts resulted positive at 800 C, especially in the case of ZnCl{sub 2} (attaining a H{sub 2} molar fraction of 0.69 at a residence time of 5 min). (author)

  15. Polarographic investigation of complexing kinetics of polyacrylate anions with cadmium ions

    International Nuclear Information System (INIS)

    Avlyanov, Zh.K.; Kabanov, N.M.; Zezin, A.B.; Askarov, M.A.

    1990-01-01

    The processes which occur during the reduction of cadmium ions from polymer-metallic complexes (PMC) are studied for the purposes of polarographic investigation of complexing kinetics of polyacrylate anions (PAA) of different molecular masses with cadmium ions in KCl aqueous solutions. An expression is derived for establishing semiwave potential. PMC formation and dissociation reduction rate constants are calculated. It is shown that intramolecular reorderings required for the formation of a two-coordinate complex proceed much slower as compared to the diffusion of free ions

  16. Kinetic study of hydrogen-material interactions in nickel base alloy 600 and stainless steel 316L through coupled experimental and numerical analysis

    International Nuclear Information System (INIS)

    Hurley, Caitlin-Mae

    2015-01-01

    In France all of the nuclear power plant facilities in service today are pressurized water reactors (PWR). Some parts of the PWR in contact with the primary circuit medium, such as the steam generator tubes (fabricated in nickel base alloy A600) and some reactor core internal components (fabricated in stainless steel 316L), can fall victim to environmental degradation phenomena such as stress corrosion cracking (SCC). In the late 1950's, H. Coriou observed experimentally and predicted this type of cracking in alloys traditionally renowned for their SCC resistance (A600). Just some 20 to 30 years later his predictions became a reality. Since then, numerous studies have focused on the description and comprehension of the SCC phenomenon in primary water under reactor operating conditions. In view of reactor lifetime extension, it has become both critical and strategic to be capable of simulating SCC phenomenon in order to optimize construction materials, operating conditions, etc. and to understand the critical parameters in order to limit the damage done by SCC. This study focuses on the role hydrogen plays in SCC phenomenon and in particular H-material interactions. Hydrogen, from primary medium in the form of dissolved H gas or H from the water, can be absorbed by the alloy during the oxidation process taking place under reactor operating conditions. Once absorbed, hydrogen may be transported across the material, diffusing in the interstitial sites of the crystallographic structure and interacting with local defects, such as dislocations, precipitates, vacancies, etc. The presence of these [local defect] sites can slow the hydrogen transport and may provoke local H accumulation in the alloy. This accumulation could modify the local mechanical properties of the material and favor premature rupture. It is therefore essential to identify the nature of these H-material interactions, specifically the rate of H diffusion and hydrogen trapping kinetics at these

  17. Computational investigation of the effects of barrier layers on the permeation of hydrogen through metals

    International Nuclear Information System (INIS)

    Perkins, W.G.

    1975-01-01

    Results of a computational investigation of the permeation behavior of oxide-coated metal membranes are presented. A steady-state permeation model was developed which promises to be useful in evaluation of oxide layers on metals as hydrogen permeation barriers. The pressure and thickness dependence of steady state permeation through oxide-coated metal membranes is described using plots of logarithmic functions. (U.S.)

  18. Single-Site Palladium(II) Catalyst for Oxidative Heck Reaction: Catalytic Performance and Kinetic Investigations

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Hui; Li, Mengyang; Zhang, Guanghui; Gallagher, James R.; Huang, Zhiliang; Sun, Yu; Luo, Zhong; Chen, Hongzhong; Miller, Jeffrey T.; Zou, Ruqiang; Lei, Aiwen; Zhao, Yanli

    2015-01-01

    ABSTRACT: The development of organometallic single-site catalysts (SSCs) has inspired the designs of new heterogeneous catalysts with high efficiency. Nevertheless, the application of SSCs in certain modern organic reactions, such as C-C bond formation reactions, has still been less investigated. In this study, a single-site Pd(II) catalyst was developed, where 2,2'-bipyridine-grafted periodic mesoporous organosilica (PMO) was employed as the support of a Pd(II) complex. The overall performance of the single-site Pd(II) catalyst in the oxidative Heck reaction was then investigated. The investigation results show that the catalyst displays over 99% selectivity for the product formation with high reaction yield. Kinetic profiles further confirm its high catalytic efficiency, showing that the rate constant is nearly 40 times higher than that for the free Pd(II) salt. X-ray absorption spectroscopy reveals that the catalyst has remarkable lifetime and recyclability.

  19. Effects of three methane mitigation agents on parameters of kinetics of total and hydrogen gas production, ruminal fermentation and hydrogen balance using in vitro technique.

    Science.gov (United States)

    Wang, Min; Wang, Rong; Yang, Shan; Deng, Jin Ping; Tang, Shao Xun; Tan, Zhi Liang

    2016-02-01

    Methane (CH4 ) can be mitigated through directly inhibiting methanogen activity and starving methanogens by hydrogen (H2 ) sink. Three types of mechanism (i.e. bromoethanesulphonate (BES), nitrate and emodin) and doses of CH4 mitigation agents were employed to investigate their pathways of CH4 inhibition. Results indicated that both BES and emodin inhibited CH4 production and altered H2 balance, which could be accompanied by decreased dry matter disappearance (DMD), fractional rate of gH2 formation, volatile fatty acid (VFA) production, ability to produce and use reducing equivalences and molecular H2 , and increased final asymptotic gH2 production, time to the peak of gH2 , discrete lag time of gH2 production and fermentation efficiency. However, emodin decreased gas volume produced by rapidly fermentable components of substrate and the rate of fermentation at early stage of incubation, while BES supplementation inhibited gas volume produced by both rapidly and slowly fermentable components of substrate and the rate of fermentation at middle or late stage of incubation. The nitrate supplementation inhibited CH4 production without affecting VFA profile, because of its dual role as H2 sink and being toxic to methanogens. Nitrate supplementation had more complicated pattern of fermentation, VFA production and profile and H2 balance in comparison to BES and emodin supplementation. © 2015 Japanese Society of Animal Science.

  20. Investigation of synthesis, thermal properties and curing kinetics of fluorene diamine-based benzoxazine by using two curing kinetic methods

    International Nuclear Information System (INIS)

    He, Xuan-yu; Wang, Jun; Ramdani, Noureddine; Liu, Wen-bin; Liu, Li-jia; Yang, Lei

    2013-01-01

    Graphical abstract: - Highlights: • A novel diamine-based benzoxazine monomer containing aryl ether and bulky fluorene groups (BEF-p) is synthesized. • Kinetic parameters can be calculated by Starink-LSR method and direct LSR method. • Cure reaction could be successfully described with the autocatalytic model. • The poly(BEF-p) exhibits high T g and superior thermal stability. • Aryl ether linkages had little influence on the thermal stability. - Abstract: A novel diamine-based benzoxazine monomer containing aryl ether and bulky fluorene groups (BEF-p) was prepared from the reaction of 9,9-bis-[4-(p-aminophenoxy)-phenyl]fluorene with paraformaldehyde and phenol. The chemical structure of monomer was confirmed by Fourier-transform infrared (FTIR) and 1 H and 13 C nuclear magnetic resonance spectroscopy ( 1 H and 13 C NMR). The polymerization behavior of monomer was analyzed by differential scanning calorimetry (DSC) and FTIR. The curing kinetics was studied by non-isothermal DSC, and the kinetic parameters were determined. The autocatalytic model based on two kinetic methods (Starink-LSR method and direct LSR method) showed good agreement with experimental results. The thermal and mechanical properties of poly(BEF-p) were evaluated with DSC, dynamic mechanical thermal analysis (DMTA), and thermogravimetric analysis (TGA). The results showed that the cured polymer exhibited higher glass transition temperature (T g ) and better thermal stability compared with diaminodiphenylmethane-based benzoxazine(P-ddm), and was slightly lower than those of fluorene diamine-phenol-based polybenzoxazine (poly(BF-p))

  1. Modeling of hydrogen desorption from tungsten surface

    Energy Technology Data Exchange (ETDEWEB)

    Guterl, J., E-mail: jguterl@ucsd.edu [University of California, San Diego, La Jolla, CA 92093 (United States); Smirnov, R.D. [University of California, San Diego, La Jolla, CA 92093 (United States); Krasheninnikov, S.I. [University of California, San Diego, La Jolla, CA 92093 (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation); Uberuaga, B.; Voter, A.F.; Perez, D. [Los Alamos National Laboratory, Los Alamos, NM 8754 (United States)

    2015-08-15

    Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed.

  2. Kinetic modeling of hydrogenation and hydro-denitrogenation mechanisms on sulfurated catalysts; Etude par modelisation cinetique des mecanismes d'hydrogenation et d'hydrodesazotation sur catalyseurs sulfures

    Energy Technology Data Exchange (ETDEWEB)

    Penet, H.

    1998-10-23

    Toluene hydrogenation on a NiMo/{gamma}-Al{sub 2}O{sub 3} catalyst was studied at 350 deg. C as a function of the partial pressures of H{sub 2}, H{sub 2}S and NH{sub 3}. This experimental study shows the following facts: the effect of the H{sub 2}S partial pressure on the hydrogenation rate is complex. The order with respect to H{sub 2}S varies between -0.05 and -0.5 as the pressure varies between 0.125 and 3 bar; in the presence of NH{sub 3}, the H{sub 2}S inhibiting effect is enhanced. Kinetic modeling was performed with the Chemkin II/Surface Chemkin II software package. On the basis of the effect of contact time and H{sub 2}S on toluene hydrogenation, the adsorption by heterolytic dissociation of H{sub 2} and H{sub 2}S was selected. H{sub 2} provides hydride species (H{sup -}) attacking the aromatic ring in a first step. Proton addition during the hydrogenation of the first double bond is the limiting step. In the presence of ammonia. the kinetic modeling shows that the catalyst surface is modified and that the displacement of the H{sub 2}S adsorption equilibrium is expected. The NH{sub 3} adsorption mode could not be clearly discriminated between a simple adsorption through coordination and an adsorption through protonation. This model was applied to the hydro-denitrogenation of 2,6-diethyl-aniline at 350 deg. C on NiMo/{gamma}-Al{sub 2}O{sub 3} catalyst and showed that the limitation step is the hydrogenation of the aromatic ring. (author)

  3. Numerical investigation of kinetic turbulence in relativistic pair plasmas - I. Turbulence statistics

    Science.gov (United States)

    Zhdankin, Vladimir; Uzdensky, Dmitri A.; Werner, Gregory R.; Begelman, Mitchell C.

    2018-02-01

    We describe results from particle-in-cell simulations of driven turbulence in collisionless, magnetized, relativistic pair plasma. This physical regime provides a simple setting for investigating the basic properties of kinetic turbulence and is relevant for high-energy astrophysical systems such as pulsar wind nebulae and astrophysical jets. In this paper, we investigate the statistics of turbulent fluctuations in simulations on lattices of up to 10243 cells and containing up to 2 × 1011 particles. Due to the absence of a cooling mechanism in our simulations, turbulent energy dissipation reduces the magnetization parameter to order unity within a few dynamical times, causing turbulent motions to become sub-relativistic. In the developed stage, our results agree with predictions from magnetohydrodynamic turbulence phenomenology at inertial-range scales, including a power-law magnetic energy spectrum with index near -5/3, scale-dependent anisotropy of fluctuations described by critical balance, lognormal distributions for particle density and internal energy density (related by a 4/3 adiabatic index, as predicted for an ultra-relativistic ideal gas), and the presence of intermittency. We also present possible signatures of a kinetic cascade by measuring power-law spectra for the magnetic, electric and density fluctuations at sub-Larmor scales.

  4. Numerical investigation on the effects of natural gas and hydrogen blends on engine combustion

    Energy Technology Data Exchange (ETDEWEB)

    Morrone, Biagio; Unich, Andrea [Dipartimento di Ingegneria Aerospaziale e Meccanica (DIAM), Seconda Universita degli Studi di Napoli via Roma 29, 81031 Aversa (CE) (Italy)

    2009-05-15

    The use of hydrogen blended with natural gas is a viable alternative to pure fossil fuels because of the expected reduction of the total pollutant emissions and increase of efficiency. These blends offer a valid opportunity for tackling sustainable transportation, in view of the future stringent emission limits for road vehicles. The aim of the present paper is the investigation of the performance of internal combustion engines fuelled by such blends. A numerical investigation on the characteristics of natural gas-hydrogen blends as well as their effect on engine performance is carried out. The activity is focused on the influence of such blends on flame propagation speed. Combustion pattern modelling allows the comparison of engine brake efficiency and power output using different fuels. Results showed that there is an increase in engine efficiency only if Maximum Brake Torque (MBT) spark advance is used for each fuel. Moreover, an economic analysis has been carried out to determine the over cost of hydrogen in such blends, showing percent increments by using these fuels about between 10 and 34%. (author)

  5. Investigation and analysis of hydrogen ignition and explosion events in foreign nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, Yasunori [Institute of Nuclear Safety System, Inc., Mihama, Fukui (Japan)

    2002-09-01

    Reports about hydrogen ignition and explosion events in foreign nuclear power plants from 1980 to 2001 were investigated, and 31 events were identified. Analysis showed that they were categorized in (1) outer leakage ignition events and (2) inner accumulation ignition events. The dominant event for PWR (pressurized water reactor) was outer leakage ignition in the main generator, and in BWR (boiling water reactor) it was inner accumulation ignition in the off-gas system. The outer leakage ignition was a result of work process failure with the ignition source, operator error, or main generator hydrogen leakage. The inner accumulation ignition events were caused by equipment failure or insufficient monitoring. With careful preventive measures, the factors leading to these events could be eliminated. (author)

  6. Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al{sub 2}O{sub 3} catalysts. Langmuir-Hinshelwood kinetic modelling

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro-Gezork, Ana Cristina Alves; Winterbottom, John Mike [Department of Chemical Engineering, School of Engineering, The University of Birmingham, Birmingham B15 2TT (United Kingdom); Natividad, Reyna [Department of Chemical Engineering, Faculty of Chemistry, Universidad Autonoma del Estado de Mexico, Paseo Colon Esq. Tollocan, Toluca, Edo. de Mexico, Mexico CP 50120 (Mexico)

    2008-01-30

    The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al{sub 2}O{sub 3}) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir-Hinshelwood (L-H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al{sub 2}O{sub 3} catalysts) on the initial reaction rate. The L-H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al{sub 2}O{sub 3} catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al{sub 2}O{sub 3} or the presulphided NiMo/Al{sub 2}O{sub 3} catalyst. (author)

  7. Diffusion and retention of hydrogen in vanadium in presence of Ti and Cr: First-principles investigations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengbo, E-mail: zhangpb@dlmu.edu.cn [Department of Physics, Dalian Maritime University, Dalian 116026 (China); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Zou, Tingting [Information Science and Technology College, Dalian Maritime University, Dalian 116026 (China); Zhao, Jijun [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Zheng, Pengfei; Chen, Jiming [Southwestern Institute of Physics, Chengdu 610041 (China)

    2017-02-15

    We systemically investigated diffusion and retention of hydrogen (H) in vanadium (V) in presence of Ti/Cr and determined the stability of H{sub n} clusters and H{sub n}-vacancy clusters (n = 1–6) near Cr/Ti using first-principles calculations. H prefers a tetrahedral site near Ti than other interstitial sites. H-Cr interactions have a weak repulsion contrarily H-Ti interactions have a weak attraction. Kinetically, H diffusion barrier decreases towards Ti, while it increases towards Cr. Ti and Cr block H mobility in V alloys. Moreover, H{sub n} Ti clusters are quite stable while H{sub n}Cr clusters are less stable. Ti enhances H retention by acting as a trapping site for multiple H atoms in similar with vacancy, and a Ti atom can trap at least six H atoms. The stability of H-vacancy-Cr/Ti complexes and vacancy-Cr/Ti trapping for multiple H atoms are discussed. The findings are valuable for understanding the mechanism of H bubble nucleation and H embrittlement under irradiation. - Highlights: • Ti enhances H retention by trapping for multiple H atoms in similar with vacancy. • H prefers the tetrahedral sites near Ti than other interstitial sites. • H diffusion barrier decreases towards Ti, while it increases towards Cr.

  8. Investigation of Kinetic Hydrate Inhibition Using a High Pressure Micro Differential Scanning Calorimeter

    DEFF Research Database (Denmark)

    Daraboina, Nagu; Malmos, Christine; von Solms, Nicolas

    2013-01-01

    of hydrate growth. Additionally, hydrate formed in the presence of inhibitor decomposed at higher temperatures compared to pure water, indicating that while hydrate formation is initially inhibited; once hydrates form, they are more stable in the presence of inhibitor. Overall, this method proved a viable......Methane hydrate formation and decomposition were investigated in the presence of the kinetic inhibitor (Luvicap EG) and synergist (polyethylene oxide; PEO) using a high pressure micro-differential scanning calorimeter (HP-μDSC) with both temperature ramping and isothermal temperature programs....... These investigations were performed using small samples in four different capillary tubes in the calorimeter cell. When the isothermal method was employed, it was found that Luvicap EG significantly delays the hydrate nucleation time as compared to water. The results obtained from the ramping method demonstrated...

  9. Equilibrium, thermodynamic and kinetic investigations for biosorption of uranium with green algae (Cladophora hutchinsiae).

    Science.gov (United States)

    Bağda, Esra; Tuzen, Mustafa; Sarı, Ahmet

    2017-09-01

    Removal of toxic chemicals from environmental samples with low-cost methods and materials are very useful approach for especially large-scale applications. Green algae are highly abundant biomaterials which are employed as useful biosorbents in many studies. In the present study, an interesting type of green algae, Cladophora hutchinsiae (C. hutchinsiae) was used for removal of highly toxic chemical such as uranium. The pH, biosorbent concentration, contact time and temperature were optimized as 5.0, 12 g/L, 60 min and 20 °C, respectively. For the equilibrium calculations, three well known isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) were employed. The maximum biosorption capacity of the biosorbent was calculated as about 152 mg/g under the optimum batch conditions. The mean energy of biosorption was calculated as 8.39 kJ/mol from the D-R biosorption isotherm. The thermodynamic and kinetic characteristics of biosorption were also investigated to explain the nature of the process. The kinetic data best fits the pseudo-second-order kinetic model with a regression coefficient of >0.99 for all studied temperatures. The calculated ΔH° and ΔG° values showed that the biosorption process is exothermic and spontaneous for temperatures between 293 and 333 K. Furthermore, after seven cycling process, the sorption and desorption efficiencies of the biosorbent were found to be 70, and 58%, respectively meaning that the biosorbent had sufficiently high reusability performance as a clean-up tool. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Numerical Investigation of Desulfurization Kinetics in Gas-Stirred Ladles by a Quick Modeling Analysis Approach

    Science.gov (United States)

    Cao, Qing; Nastac, Laurentiu; Pitts-Baggett, April; Yu, Qiulin

    2018-03-01

    A quick modeling analysis approach for predicting the slag-steel reaction and desulfurization kinetics in argon gas-stirred ladles has been developed in this study. The model consists of two uncoupled components: (i) a computational fluid dynamics (CFD) model for predicting the fluid flow and the characteristics of slag-steel interface, and (ii) a multicomponent reaction kinetics model for calculating the desulfurization evolution. The steel-slag interfacial area and mass transfer coefficients predicted by the CFD simulation are used as the processing data for the reaction model. Since the desulfurization predictions are uncoupled from the CFD simulation, the computational time of this uncoupled predictive approach is decreased by at least 100 times for each case study when compared with the CFD-reaction kinetics fully coupled model. The uncoupled modeling approach was validated by comparing the evolution of steel and slag compositions with the experimentally measured data during ladle metallurgical furnace (LMF) processing at Nucor Steel Tuscaloosa, Inc. Then, the validated approach was applied to investigate the effects of the initial steel and slag compositions, as well as different types of additions during the refining process on the desulfurization efficiency. The results revealed that the sulfur distribution ratio and the desulfurization reaction can be promoted by making Al and CaO additions during the refining process. It was also shown that by increasing the initial Al content in liquid steel, both Al oxidation and desulfurization rates rapidly increase. In addition, it was found that the variation of the initial Si content in steel has no significant influence on the desulfurization rate. Lastly, if the initial CaO content in slag is increased or the initial Al2O3 content is decreased in the fluid-slag compositional range, the desulfurization rate can be improved significantly during the LMF process.

  11. Heavy fuel oil pyrolysis and combustion: kinetics and evolved gases investigated by TGA-FTIR

    KAUST Repository

    Abdul Jameel, Abdul Gani

    2017-08-24

    Heavy fuel oil (HFO) obtained from crude oil distillation is a widely used fuel in marine engines and power generation technologies. In the present study, the pyrolysis and combustion of a Saudi Arabian HFO in nitrogen and in air, respectively, were investigated using non-isothermal thermo-gravimetric analysis (TGA) coupled with a Fourier-transform infrared (FTIR) spectrometer. TG and DTG (differential thermo-gravimetry) were used for the kinetic analysis and to study the mass loss characteristics due to the thermal degradation of HFO at temperatures up to 1000°C and at various heating rates of 5, 10 and 20°C/min, in air and N2 atmospheres. FTIR analysis was then performed to study the composition of the evolved gases. The TG/DTG curves during HFO combustion show the presence of three distinct stages: the low temperature oxidation (LTO); fuel decomposition (FD); and high temperature oxidation (HTO) stages. The TG/DTG curves obtained during HFO pyrolysis show the presence of two devolatilization stages similar to that seen in the LTO stage of HFO combustion. Apart from this, the TG/DTG curves obtained during HFO combustion and pyrolysis differ significantly. Kinetic analysis was also performed using the distributed activation energy model, and the kinetic parameter (E) was determined for the different stages of HFO combustion and pyrolysis processes, yielding a good agreement with the measured TG profiles. FTIR analysis showed the signal of CO2 as approximately 50 times more compared to the other pollutant gases under combustion conditions. Under pyrolytic conditions, the signal intensity of alkane functional groups was the highest followed by alkenes. The TGA-FTIR results provide new insights into the overall HFO combustion processes, which can be used to improve combustor designs and control emissions.

  12. Numerical Investigation of Desulfurization Kinetics in Gas-Stirred Ladles by a Quick Modeling Analysis Approach

    Science.gov (United States)

    Cao, Qing; Nastac, Laurentiu; Pitts-Baggett, April; Yu, Qiulin

    2018-06-01

    A quick modeling analysis approach for predicting the slag-steel reaction and desulfurization kinetics in argon gas-stirred ladles has been developed in this study. The model consists of two uncoupled components: (i) a computational fluid dynamics (CFD) model for predicting the fluid flow and the characteristics of slag-steel interface, and (ii) a multicomponent reaction kinetics model for calculating the desulfurization evolution. The steel-slag interfacial area and mass transfer coefficients predicted by the CFD simulation are used as the processing data for the reaction model. Since the desulfurization predictions are uncoupled from the CFD simulation, the computational time of this uncoupled predictive approach is decreased by at least 100 times for each case study when compared with the CFD-reaction kinetics fully coupled model. The uncoupled modeling approach was validated by comparing the evolution of steel and slag compositions with the experimentally measured data during ladle metallurgical furnace (LMF) processing at Nucor Steel Tuscaloosa, Inc. Then, the validated approach was applied to investigate the effects of the initial steel and slag compositions, as well as different types of additions during the refining process on the desulfurization efficiency. The results revealed that the sulfur distribution ratio and the desulfurization reaction can be promoted by making Al and CaO additions during the refining process. It was also shown that by increasing the initial Al content in liquid steel, both Al oxidation and desulfurization rates rapidly increase. In addition, it was found that the variation of the initial Si content in steel has no significant influence on the desulfurization rate. Lastly, if the initial CaO content in slag is increased or the initial Al2O3 content is decreased in the fluid-slag compositional range, the desulfurization rate can be improved significantly during the LMF process.

  13. An investigation on the hydrogen storage characteristics of the melt-spun nanocrystalline and amorphous Mg20-xLaxNi10 (x = 0, 2) hydrogen storage alloys

    International Nuclear Information System (INIS)

    Zhang Yanghuan; Li Baowei; Ren Huiping; Guo Shihai; Wu Zhongwang; Wang Xinlin

    2009-01-01

    Mg 2 Ni-type hydrogen storage alloys Mg 20-x La x Ni 10 (x = 0, 2) were prepared by casting and rapid quenching. The structures and morphologies of the as-cast and quenched alloys were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). Thermal stability of the as-quenched alloys was researched by differential scanning calorimetry (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus, and their electrochemical properties were measured by a tri-electrode open cell. The results showed that the no amorphous phase formed in the as-quenched La-free alloy, but the as-quenched alloys containing La held a major amorphous phase. The quenching rate induced a light influence on the crystallization temperature of the amorphous phase, and it significantly improved the initial hydrogenation rate and the hydrogen absorption capacity of the alloys. The discharge capacity and the cycle stability of the alloys grew with the increase of the quenching rate. When the quenching rate increased from 0 (as-cast was defined at a quenching rate of 0 m s -1 ) to 30 m s -1 , the hydrogen absorption capacity of the alloys for x = 0 and 2 at 200 deg. C and 1.5 MPa in 10 min changed from 1.21 to 3.10 wt.% and from 1.26 to 2.60 wt.%, the maximum discharge capacity from 30.26 to 135.51 mAh g -1 and from 197.23 to 406.51 mAh g -1 at a current density of 20 mA g -1 , and the capacity retaining rate at 20th cycle from 36.71 to 27.06% and from 37.26 to 78.33%, respectively

  14. Investigation of the structural and hydrogenation properties of disordered Ti-V-Cr-Mo BCC solid solutions

    International Nuclear Information System (INIS)

    Raufast, C.; Planté, D.; Miraglia, S.

    2014-01-01

    Highlights: • Materials synthesis and structural analysis of selected compositions of TiVCr(Mo) bcc samples. • Extraction of the thermodynamics relevant parameters for hydride formation and dissociation state of Ti 0.3 V 1.7 Cr 0.7 Mo 0.3 sample. • Discussion of the hydrides practicability. - Abstract: Selected compositions in the Ti-Cr-V-Mo system (with the BCC structure-type) have been synthesized and characterized for structural (crystalline structure, solidification microstructure) and thermodynamic properties (equilibrium and reversible hydrogen storage capacity). We present as well the effect of co-melting with a so-called activating phase that results in a secondary phase development and a subsequent enhancement of the hydrogen sorption kinetics. Ageing properties and applicability of such materials for hybrid hydrogen storage systems are also discussed

  15. A reduced chemical kinetic model for the analytical investigations on the oxidation kinetics and performance characteristics of diesel fuel

    International Nuclear Information System (INIS)

    Selvaraj, N.; Manoj Kumar, C.V.; Babu, M.S.

    2010-01-01

    A detailed study of the combustion of diesel fuel has been conducted analytically using a kinetic scheme with 767 elementary reactions and 158 species. A program has been developed in MATLAB for the analysis of ignition delay, performance, soot formation and emission characteristics of diesel fuel. Nitrogen is considered as the diluent and its percentage is assumed as 79%. The criteria used for the determination of ignition delay time are based on OH concentration to reach a value of 1x10 -9 . A brief review of diesel combustion and soot formation is given. (author)

  16. Estudio cinético de la descomposición catalizada de peróxido de hidrógeno sobre carbón activado Kinetic study of the catalyzed decomposition of hydrogen peroxide on activated carbon

    Directory of Open Access Journals (Sweden)

    Elihu Paternina

    2009-01-01

    Full Text Available The kinetic study of decomposition of hydrogen peroxide catalyzed by activated carbon was carried out. The effect of concentrations of reactants and temperature were experimentally studied. Kinetic data were evaluated using differential method of initial rates of reaction. When a typical kinetic law for reactions in homogeneous phase is used, first order of reaction is obtained for hydrogen peroxide and activated carbon, and activation energy of 27 kJ mol-1 for the reaction was estimated. Experimentally was observed that surface of activated carbon is chemically modified during decomposition of hydrogen peroxide, based on this result a scheme of reaction was proposed and evaluated. Experimental data fits very well to a Langmuir- Hinshelwood kinetic model and activation energy of 40 kJ mol-1 was estimated for reaction in heterogeneous phase.

  17. Investigating the conformational stability of prion strains through a kinetic replication model.

    Directory of Open Access Journals (Sweden)

    Mattia Zampieri

    2009-07-01

    Full Text Available Prion proteins are known to misfold into a range of different aggregated forms, showing different phenotypic and pathological states. Understanding strain specificities is an important problem in the field of prion disease. Little is known about which PrP(Sc structural properties and molecular mechanisms determine prion replication, disease progression and strain phenotype. The aim of this work is to investigate, through a mathematical model, how the structural stability of different aggregated forms can influence the kinetics of prion replication. The model-based results suggest that prion strains with different conformational stability undergoing in vivo replication are characterizable in primis by means of different rates of breakage. A further role seems to be played by the aggregation rate (i.e. the rate at which a prion fibril grows. The kinetic variability introduced in the model by these two parameters allows us to reproduce the different characteristic features of the various strains (e.g., fibrils' mean length and is coherent with all experimental observations concerning strain-specific behavior.

  18. Thermoactivated persulfate oxidation of pesticide chlorpyrifos in aquatic system: kinetic and mechanistic investigations.

    Science.gov (United States)

    Zhou, Lei; Zhang, Ya; Ying, Rongrong; Wang, Guoqing; Long, Tao; Li, Jianhua; Lin, Yusuo

    2017-04-01

    The widespread occurrence of organophosphorus pesticides (OPPs) in the environment poses risks to both ecologic system as well as human health. This study investigated the oxidation kinetics of chlorpyrifos (CP), one of the typical OPPs, by thermoactivated persulfate (PS) oxidation process, and evaluated the influence of key kinetic factors, such as PS concentrations, pH, temperature, bicarbonate, and chloride ions. The reaction pathways and mechanisms were also proposed based on products identification by LC-MS techniques. Our results revealed that increasing initial PS concentration and temperature favored the decomposition of CP, whereas the oxidation efficiency was not affected by pH change ranging from 3 to 11. Bicarbonate was found to play a detrimental role on CP removal rates, while chloride showed no effect. The oxidation pathways including initial oxidation of P=S bond to P=O, dechlorination, dealkylation, and the dechlorination-hydroxylation were proposed, and the detailed underlying mechanisms were also discussed. Molecular orbital (MO) calculations indicated that P=S bond was the most favored oxidation site of the molecule. The toxicity of reaction solution was believed to increase due to the formation of products with P=O structures. This work demonstrates that OPPs can readily react with SO 4 ·- and provides important information for further research on the oxidation of these contaminants.

  19. Kinetic investigation of the catalytic mechanism for bovine liver mitochondrial monoamine oxidase

    International Nuclear Information System (INIS)

    Walker, M.C.

    1988-01-01

    The kinetic behavior of the oxidative deamination reaction catalyzed by bovine liver mitochondrial monoamine oxidase was investigated with a series of ring-substituted benzylamines. Oxidation rates were fastest with the meta isomers. Dalziel coefficients were consistent with a mechanism involving a ternary complex for all substrates tested. Alterations in the Michaelis constant for oxygen were similar in magnitude to those for the rate of catalysis. Deuterium and tritium isotope effects were determined to obtain more detailed information on the mechanism of catalysis. Large deuterium isotope effects expressed on k cat were obtained for all substrates. Determination of the tritium isotope effect for benzylamine allowed the calculation of an intrinsic isotope effect of 6.5 and a secondary isotope effect of 1.17. Steady-state experiments were supplemented with pre-steady-state kinetic techniques. Rates of flavin reduction were faster than that of turnover. The deuterium isotope effect obtained for the rate of flavin reduction was 7-15 for the various substrates. The observed isotope effect was found to be an appropriate estimate for the intrinsic isotope effect

  20. Investigation of nucleation kinetics in H2SO4 vapor through modeling of gas phase kinetics coupled with particle dynamics

    Science.gov (United States)

    Carlsson, Philip T. M.; Zeuch, Thomas

    2018-03-01

    We have developed a new model utilizing our existing kinetic gas phase models to simulate experimental particle size distributions emerging in dry supersaturated H2SO4 vapor homogeneously produced by rapid oxidation of SO2 through stabilized Criegee-Intermediates from 2-butene ozonolysis. We use a sectional method for simulating the particle dynamics. The particle treatment in the model is based on first principles and takes into account the transition from the kinetic to the diffusion-limited regime. It captures the temporal evolution of size distributions at the end of the ozonolysis experiment well, noting a slight underrepresentation of coagulation effects for larger particle sizes. The model correctly predicts the shape and the modes of the experimentally observed particle size distributions. The predicted modes show an extremely high sensitivity to the H2SO4 evaporation rates of the initially formed H2SO4 clusters (dimer to pentamer), which were arbitrarily restricted to decrease exponentially with increasing cluster size. In future, the analysis presented in this work can be extended to allow a direct validation of quantum chemically predicted stabilities of small H2SO4 clusters, which are believed to initiate a significant fraction of atmospheric new particle formation events. We discuss the prospects and possible limitations of the here presented approach.

  1. First principle investigations of the physical properties of hydrogen-rich MgH2

    KAUST Repository

    Zarshenas, Mohammed

    2013-11-28

    Hydrogen being a cleaner energy carrier has increased the importance of hydrogen-containing light metal hydrides, in particular those with large gravimetric hydrogen density like magnesium hydride (MgH2). In this study, density functional and density functional perturbation theories are combined to investigate the structural, elastic, thermodynamic, electronic and optical properties of MgH2. Our structural parameters calculated with those proposed by Perdew, Burke and Ernzerof generalized gradient approximation (PBE-GGA) and Wu-Cohen GGA (WC-GGA) are in agreement with experimental measurements, however the underestimated band gap values calculated using PBE-GGA and WC-GGA were greatly improved with the GGA suggested by Engle and Vosko and the modified Becke-Johnson exchange correlation potential by Trans and Blaha. As for the thermodynamic properties the specific heat values at low temperatures were found to obey the T3 rule and at higher temperatures Dulong and Petit\\'s law. Our analysis of the optical properties of MgH2 also points to its potential application in optoelectronics. © 2013 The Royal Swedish Academy of Sciences.

  2. Experimental Investigation of Jet-Induced Mixing of a Large Liquid Hydrogen Storage Tank

    Science.gov (United States)

    Lin, C. S.; Hasan, M. M.; Vandresar, N. T.

    1994-01-01

    Experiments have been conducted to investigate the effect of fluid mixing on the depressurization of a large liquid hydrogen storage tank. The test tank is approximately ellipsoidal, having a volume of 4.89 m(exp 3) and an average wall heat flux of 4.2 W/m(exp 2) due to external heat input. A mixer unit was installed near the bottom of the tank to generate an upward directed axial jet flow normal to the liquid-vapor interface. Mixing tests were initiated after achieving thermally stratified conditions in the tank either by the introduction of hydrogen gas into the tank or by self-pressurization due to ambient heat leak through the tank wall. The subcooled liquid jet directed towards the liquid-vapor interface by the mixer induced vapor condensation and caused a reduction in tank pressure. Tests were conducted at two jet submergence depths for jet Reynolds numbers from 80,000 to 495,000 and Richardson numbers from 0.014 to 0.52. Results show that the rate of tank pressure change is controlled by the competing effects of subcooled jet flow and the free convection boundary layer flow due to external tank wall heating. It is shown that existing correlations for mixing time and vapor condensation rate based on small scale tanks may not be applicable to large scale liquid hydrogen systems.

  3. First principle investigations of the physical properties of hydrogen-rich MgH2

    KAUST Repository

    Zarshenas, Mohammed; Ahmed, Rashid; Kanoun, Mohammed; Ul Haq, Bakhtiar; Isa, Ahmad Radzi Mat; Goumri-Said, Souraya

    2013-01-01

    Hydrogen being a cleaner energy carrier has increased the importance of hydrogen-containing light metal hydrides, in particular those with large gravimetric hydrogen density like magnesium hydride (MgH2). In this study, density functional and density functional perturbation theories are combined to investigate the structural, elastic, thermodynamic, electronic and optical properties of MgH2. Our structural parameters calculated with those proposed by Perdew, Burke and Ernzerof generalized gradient approximation (PBE-GGA) and Wu-Cohen GGA (WC-GGA) are in agreement with experimental measurements, however the underestimated band gap values calculated using PBE-GGA and WC-GGA were greatly improved with the GGA suggested by Engle and Vosko and the modified Becke-Johnson exchange correlation potential by Trans and Blaha. As for the thermodynamic properties the specific heat values at low temperatures were found to obey the T3 rule and at higher temperatures Dulong and Petit's law. Our analysis of the optical properties of MgH2 also points to its potential application in optoelectronics. © 2013 The Royal Swedish Academy of Sciences.

  4. Ir4+-Doped NiFe LDH to expedite hydrogen evolution kinetics as a Pt-like electrocatalyst for water splitting.

    Science.gov (United States)

    Chen, Qian-Qian; Hou, Chun-Chao; Wang, Chuan-Jun; Yang, Xiao; Shi, Rui; Chen, Yong

    2018-06-06

    NiFe-layered double hydroxide (NiFe LDH) is a state-of-the-art oxygen evolution reaction (OER) electrocatalyst, yet it suffers from rather poor catalytic activity for the hydrogen evolution reaction (HER) due to its extremely sluggish water dissociation kinetics, severely restricting its application in overall water splitting. Herein, we report a novel strategy to expedite the HER kinetics of NiFe LDH by an Ir4+-doping strategy to accelerate the water dissociation process (Volmer step), and thus this catalyst exhibits superior and robust catalytic activity for finally oriented overall water splitting in 1 M KOH requiring only a low initial voltage of 1.41 V delivering at 20 mA cm-2 for more than 50 h.

  5. Influence of hydrogen on the behaviour of metals - Mechanical and kinetic properties of fatigue cracking of steady (ZXNCTD-26-15) and unsteady (Z2CN-18-10) austenitic stainless steels. Role of heat treatments and of cathodic hydrogen

    International Nuclear Information System (INIS)

    Huwarts, Pascale; Habashi, Mahmoud

    1984-01-01

    In a context which is characterized by an increased demand in high resistance stainless steels, austenitic stainless steels with structural hardening have been notably studied. These are ductile materials in over-hardened state, therefore machinable, and can be hardened by ageing heat treatment after machining. The author reports the study of the tensile and resilience mechanical behaviour, and of the kinetic fatigue cracking of three austenitic stainless steels in presence of hydrogen. One of them is unsteady and belongs to the 300 family, whereas the two others are grades of a steady steel with structural hardening (26 pc Ni - 15 pc Cr). The author more particularly focused on the influence of thermal treatments and of phase transformation on hydrogen-induced embrittlement of these steels. After a bibliographical study on austenitic stainless steels and on their behaviour with respect to hydrogen, the author reports a detailed analysis of the studied steels. He reports tests and their results, and discusses the role of microstructure in the mechanical behaviour of these steels in presence and in absence of cathodic hydrogen [fr

  6. Impact of Nanostructuring on the Phase Behavior of Insertion Materials: The Hydrogenation Kinetics of a Magnesium Thin Film

    NARCIS (Netherlands)

    Bannenberg, L.J.; Schreuders, H.; van Eijck, L.; Heringa, J.R.; Steinke, N.J.; Dalgliesh, RM; Dam, B.; Mulder, F.M.; van Well, A.A.

    2016-01-01

    Nanostructuring is widely applied in both battery and hydrogen materials to improve the performance of these materials as energy carriers. Nanostructuring changes the diffusion length as well as the thermodynamics of materials. We studied the impact of nanostructuring on the hydrogenation in a model

  7. Hydrogen adsorption on activated carbon nanotubes with an atomic-sized vanadium catalyst investigated by electrical resistance measurements

    International Nuclear Information System (INIS)

    Im, Ji Sun; Yun, Jumi; Kang, Seok Chang; Lee, Sung Kyu; Lee, Young-Seak

    2012-01-01

    Activated multi-walled carbon nanotubes were prepared with appended vanadium as a hydrogen storage medium. The pore structure was significantly improved by an activation process that was studied using Raman spectroscopy, field emission transmission electron microscopy and pore analysis techniques. X-ray photoelectron spectroscopy and X-ray diffraction results reveal that the vanadium catalyst was introduced into the carbon nanotubes in controlled proportions, forming V 8 C 7 . The improved pore structure functioned as a path through the carbon nanotubes that encouraged hydrogen molecule adsorption, and the introduced vanadium catalyst led to high levels of hydrogen storage through the dissociation of hydrogen molecules via the spill-over phenomenon. The hydrogen storage behavior was investigated by electrical resistance measurements for the hydrogen adsorbed on a prepared sample. The proposed mechanism of hydrogen storage suggests that the vanadium catalyst increases not only the amount of hydrogen that is stored but also the speed at which it is stored. A hydrogen storage capacity of 2.26 wt.% was achieved with the activation effects and the vanadium catalyst at 30 °C and 10 MPa.

  8. Hydrogen Absorption in Metal Thin Films and Heterostructures Investigated in Situ with Neutron and X-ray Scattering

    Directory of Open Access Journals (Sweden)

    Sara J. Callori

    2016-05-01

    Full Text Available Due to hydrogen possessing a relatively large neutron scattering length, hydrogen absorption and desorption behaviors in metal thin films can straightforwardly be investigated by neutron reflectometry. However, to further elucidate the chemical structure of the hydrogen absorbing materials, complementary techniques such as high resolution X-ray reflectometry and diffraction remain important too. Examples of work on such systems include Nb- and Pd-based multilayers, where Nb and Pd both have strong affinity to hydrogen. W/Nb and Fe/Nb multilayers were measured in situ with unpolarized and polarized neutron reflectometry under hydrogen gas charging conditions. The gas-pressure/hydrogen-concentration dependence, the hydrogen-induced macroscopic film swelling as well as the increase in crystal lattice plane distances of the films were determined. Ferromagnetic-Co/Pd multilayers were studied with polarized neutron reflectometry and in situ ferromagnetic resonance measurements to understand the effect of hydrogen absorption on the magnetic properties of the system. This electronic effect enables a novel approach for hydrogen sensing using a magnetic readout scheme.

  9. Kinetics and mechanisms of the oxidation of alcohols and hydroxylamines by hydrogen peroxide, catalyzed by methyltrioxorhenium, MTO, and the oxygen binding properties of cobalt Schiff base complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zauche, Timothy [Iowa State Univ., Ames, IA (United States)

    1999-02-12

    Catalysis is a very interesting area of chemistry, which is currently developing at a rapid pace. A great deal of effort is being put forth by both industry and academia to make reactions faster and more productive. One method of accomplishing this is by the development of catalysts. Enzymes are an example of catalysts that are able to perform reactions on a very rapid time scale and also very specifically; a goal for every man-made catalyst. A kinetic study can also be carried out for a reaction to gain a better understanding of its mechanism and to determine what type of catalyst would assist the reaction. Kinetic studies can also help determine other factors, such as the shelf life of a chemical, or the optimum temperature for an industrial scale reaction. An area of catalysis being studied at this time is that of oxygenations. Life on this earth depends on the kinetic barriers for oxygen in its various forms. If it were not for these barriers, molecular oxygen, water, and the oxygenated materials in the land would be in a constant equilibrium. These same barriers must be overcome when performing oxygenation reactions on the laboratory or industrial scale. By performing kinetic studies and developing catalysts for these reactions, a large number of reactions can be made more economical, while making less unwanted byproducts. For this dissertation the activation by transition metal complexes of hydrogen peroxide or molecular oxygen coordination will be discussed.

  10. Investigation of the kinetics of the change in the group composition of the anthracene fraction on heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Belkina, T.V.; Lur' e, M.V.; Stepanenko, M.A.

    1981-01-01

    In the reported experiments, an investigation has been made of the kinetics of the change in the group composition of the anthracene fraction during heat treatment under various conditions. On the basis of the results obtained, a kinetic model of the process has been developed which permits rational conditions for obtaining a heat-treated product of the necessary group composition to be found. 6 refs.

  11. Investigation of Iron Oxide Morphology in a Cyclic Redox Water Splitting Process for Hydrogen Generation

    Directory of Open Access Journals (Sweden)

    Michael M. Bobek

    2012-10-01

    Full Text Available A solar fuels generation research program is focused on hydrogen production by means of reactive metal water splitting in a cyclic iron-based redox process. Iron-based oxides are explored as an intermediary reactive material to dissociate water molecules at significantly reduced thermal energies. With a goal of studying the resulting oxide chemistry and morphology, chemical assistance via CO is used to complete the redox cycle. In order to exploit the unique characteristics of highly reactive materials at the solar reactor scale, a monolithic laboratory scale reactor has been designed to explore the redox cycle at temperatures ranging from 675 to 875 K. Using high resolution scanning electron microscope (SEM and electron dispersive X-ray spectroscopy (EDS, the oxide morphology and the oxide state are quantified, including spatial distributions. These images show the change of the oxide layers directly after oxidation and after reduction. The findings show a significant non-stoichiometric O/Fe gradient in the atomic ratio following oxidation, which is consistent with a previous kinetics model, and a relatively constant, non-stoichiometric O/Fe atomic ratio following reduction.

  12. Investigation of Au/Au(100) film growth with energetic deposition by kinetic Monte Carlo simulation

    International Nuclear Information System (INIS)

    Zhang Qingyu; Ma Tengcai; Pan Zhengying; Tang Jiayong

    2000-01-01

    The Au/Au(100) epitaxial growth with energetic deposition was simulated by using kinetic Monte Carlo method. The influences of energetic atoms on morphology and atomistic processes in the early stage of film growth were investigated. The reentrant layer-by-layer growth was observed in the temperature range of 450 K to 100 K. The authors found the energetic atoms can promote the nucleation and island growth in the early stages of film growth and enhance the smoothness of film surface at temperatures of film growth in 3-dimensional mode and in quasi-two-dimensional mode. The atomistic mechanism that promotes the nucleation and island growth and enhances the smoothness of film surface is discussed

  13. Investigation of the behavior of TMI-2 containment structure for hydrogen burn accidents

    International Nuclear Information System (INIS)

    Kamil, H.; Chen, M.C.; Kost, G.; Miller, A.

    1981-01-01

    The paper describes the following main tasks performed as part of this investigation: 1) definition of design; 2) identification of conservatisms in design; 3) review of load functions; 4) determination of preliminary capacity of the containment. The basic design criteria, acceptance criteria, and analytical procedures which formed the basis of the original containment design were first briefly reviewed. The conservatisms in the various assumptions and parameters used in the design and analysis of the containment were then identified. The postulated load functions for hydrogen burn accidents used in the evaluation of the containment capacity were then reviewed. (orig./HP)

  14. An investigation of turbulent catalytically stabilized channel flow combustion of lean hydrogen - air mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Mantzaras, I; Benz, P; Schaeren, R; Bombach, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The catalytically stabilised thermal combustion (CST) of lean hydrogen-air mixtures was investigated numerically in a turbulent channel flow configuration using a two-dimensional elliptic model with detailed heterogeneous and homogeneous chemical reactions. Comparison between turbulent and laminar cases having the same incoming mean properties shows that turbulence inhibits homogeneous ignition due to increased heat transport away from the near-wall layer. The peak root-mean-square temperature and species fluctuations are always located outside the extent of the homogeneous reaction zone indicating that thermochemical fluctuations have no significant influence on gaseous combustion. (author) 4 figs., 6 refs.

  15. Investigations on Cs-free alternative materials for negative hydrogen ion formation

    Energy Technology Data Exchange (ETDEWEB)

    Kurutz, Uwe

    2017-01-19

    Neutral beam injection (NBI) represents a main auxiliary heating and current drive system for thermonuclear fusion devices. For ITER, a total heating power of up to 33 MW will be delivered for up to one hour pulses at particle energies of up to 1 MeV by two NBI systems. The respective ion sources will therefore have to allow for the extraction and acceleration of negative hydrogen ions at a current density of 200 A/m{sup 2} from a low pressure low temperature hydrogen plasma. Also for the succeeding demonstration reactor DEMO the application of NBI is currently discussed. Respective systems will, however, have to fulfil even higher demands, like higher powers (up to 135 MW), longer pulse lengths (2 h or even cw operation), and more restrictive constrains regarding the reliability and stability. Today efficient NBI negative hydrogen ion sources are based mainly on the conversion of positive hydrogen ions and/or hydrogen atoms at a grid surface coated with caesium. Cs is used for reducing the grid's work function which significantly enhances the particle conversion probability. However, the alkali metal is chemically very reactive and easily forms compounds with residual gas impurities. Furthermore, complex redistribution dynamics of the deposited Cs layer is given. This inherently links the application of Cs with a temporal and spatial non-stability of the negative ion yield, which contradicts the required reliability of a DEMO NBI system. Thus, for DEMO, Cs-free alternative materials for negative ion formation are investigated within this work at a flexible laboratory experiment. An ECR discharge is used which provides comparable parameters (pressure, densities, particle fluxes and -energies) to the NBI ion sources. Negative ion formation is measured above different material samples via laser photodetachment together with global plasma parameters using a Langmuir probe and optical emission spectroscopy. The plasma parameters are used for modelling the

  16. Investigations on Cs-free alternative materials for negative hydrogen ion formation

    International Nuclear Information System (INIS)

    Kurutz, Uwe

    2017-01-01

    Neutral beam injection (NBI) represents a main auxiliary heating and current drive system for thermonuclear fusion devices. For ITER, a total heating power of up to 33 MW will be delivered for up to one hour pulses at particle energies of up to 1 MeV by two NBI systems. The respective ion sources will therefore have to allow for the extraction and acceleration of negative hydrogen ions at a current density of 200 A/m 2 from a low pressure low temperature hydrogen plasma. Also for the succeeding demonstration reactor DEMO the application of NBI is currently discussed. Respective systems will, however, have to fulfil even higher demands, like higher powers (up to 135 MW), longer pulse lengths (2 h or even cw operation), and more restrictive constrains regarding the reliability and stability. Today efficient NBI negative hydrogen ion sources are based mainly on the conversion of positive hydrogen ions and/or hydrogen atoms at a grid surface coated with caesium. Cs is used for reducing the grid's work function which significantly enhances the particle conversion probability. However, the alkali metal is chemically very reactive and easily forms compounds with residual gas impurities. Furthermore, complex redistribution dynamics of the deposited Cs layer is given. This inherently links the application of Cs with a temporal and spatial non-stability of the negative ion yield, which contradicts the required reliability of a DEMO NBI system. Thus, for DEMO, Cs-free alternative materials for negative ion formation are investigated within this work at a flexible laboratory experiment. An ECR discharge is used which provides comparable parameters (pressure, densities, particle fluxes and -energies) to the NBI ion sources. Negative ion formation is measured above different material samples via laser photodetachment together with global plasma parameters using a Langmuir probe and optical emission spectroscopy. The plasma parameters are used for modelling the inherently

  17. Experimental Investigation of the Effect of Hydrogen Manifold Injection on the Performance of Compression Ignition Engines

    OpenAIRE

    Haroun A.K. Shahad; Nabeel Abdul-Hadi

    2011-01-01

    Experiments were carried out to evaluate the influence of the addition of hydrogen to the inlet air on the performance of a single cylinder direct injection diesel engine. Hydrogen was injected in the inlet manifold. The addition of hydrogen was done on energy replacement basis. It was found that the addition of hydrogen improves the combustion process due to superior combustion characteristics of hydrogen in comparison to conventional diesel fuels. It was also found that...

  18. Investigation of hydrogen recombination under natural convection conditions; Untersuchungen zur Wasserstoffrekombination unter Naturkonvektionsbedingungen

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Berno

    2015-09-04

    Passive Autocatalytic Recombiners (PAR) are installed inside the containment of nuclear power plants in order to prevent the build-up of flammable mixtures and to mitigate the effects of hydrogen deflagrations, which can occur in the event of a severe accident combined with the release of hydrogen. In order to simulate the operating behaviour of PARs, the computer program REKO-DIREKT is being developed at the Forschungszentrum Juelich in collaboration with the Institute for Reactor Safety and Reactor Technology at the RWTH Aachen. For the validation of the code, data from experimental facilities operated at Juelich are used. This work focusses on the analysis of the chimney effect through the PAR housing as well as the optimization of the chimney model of REKO-DIREKT. Therefore experimental investigations are carried out in the REKO-4 facility under natural convection conditions. This facility is equipped with numerous measuring devices, e.g. katharometers for in-situ measuring of the hydrogen concentration and the optical flow measurement technique Particle-Image-Velocimetry. In preliminary assessments the equipment is being qualified in order to determine the measurement accuracy. In the following experimental investigations, a small-scale PAR is used, that is built in a modular way allowing it to be equipped with different chimney geometries. The experimental results produce a database that shows the central correlation between the hydrogen concentration, the catalyst temperature and the inlet velocity. The results include the variation of the recombiner's chimney height and experiments at different operating pressures. After optimization of the chimney model, the simulation program is validated against experiments in the large-scale facility THAI in Eschborn, which have been performed subsequent to this thesis in the context of the OECD/NEA-THAI project. Finally, the influence of a downward-directed, near-wall flow on the operational behaviour of the small

  19. Electrochemically controlled release of anticancer drug methotrexate using nanostructured polypyrrole modified with cetylpyridinium: Release kinetics investigation

    International Nuclear Information System (INIS)

    Alizadeh, Naader; Shamaeli, Ehsan

    2014-01-01

    A new simple strategy for direct electrochemical incorporation of chemotherapeutic methotrexate (MTX) into conductive polypyrrole (PPy) has been suggested for an electrochemically controlled loading and release system. Electropolymerization of MTX doped polypyrrole yielded poor quality with low efficiency of doping, but a well-doped, nanostructure and increased capacity of drug loading (24.5 mg g −1 ) has been obtained in the presence of cetylpyridinium (CP) as a modifier. When CP was preloaded onto PPy, the hydrophobic surface of the PPy serves as a backbone to which the hydrophobic chain of the CP can be attached. Electrostatic interaction between cationic CP with anionic MTX and aromatic interaction between pyridinium head of CP with pyrimidine and pyrazine rings of MTX increases drug doping. Then release kinetics were investigated at various applied potentials and temperatures. Kinetics analysis based on Avrami's equation showed that the drug release was controlled and accelerated by increasing temperature and negative potential and sustained by increasing positive potential. At open circuit condition, the release parameter (n) represented a diffusive mechanism and at applying electrochemical potentials, a first-order mode. Activation energy parameters (E a , ΔG ≠ , ΔH ≠ and ΔS ≠ ) and half-life time (t 1/2 ) of drug release are also analyzed as a function of applied potential. The nanostructured polymer films (PPy/CP/MTX) were characterized by several techniques: scanning electron microscopy, Furrier transforms Infrared, UV-vis spectroscopy. Overall, our results demonstrate that the PPy/CP/MTX films, combined with electrical stimulation, permit a programmable release of MTX by altering the interaction strength between the PPy/CP and MTX

  20. Investigation of digestion Kinetics in commercial starches using in-situ small-angle neutron scattering

    International Nuclear Information System (INIS)

    Blazek, Jaroslav; Gilbert, Elliot Paul

    2009-01-01

    Full text: The digestion of starch has been the subject of many investigations, mostly involving in vitro measurement of the susceptibility of starches to attack by different enzymes, rather than measuring actual digestibility in vivo. The rate and extent of amylolytic hydrolysis of granular starches is known to vary according to botanical origin. Granule characteristics considered to influence susceptibility to attack by alpha-amylase include crystallinity, granule size and available specific surface, amylose content, porosity, structural inhomogeneities and degree of integrity. Most in-vitro studies of granular starch digestion have been limited to samples for which aliquots have been removed from the reaction mixture at various time intervals and freeze-dried to be subsequently characterized using a range of techniques. It remains unclear whether sample preparation creates artefacts in the samples. In this study, we have studied the kinetics of starch digestion of several commercial granular starches by time-resolved small-angle neutron scattering using an in-situ digestion chamber allowing, for the first time, to follow structural changes of starch in the course of digestion directly in the digestion mixture. Additionally, samples before and after digestion were studied by x-ray diffraction, small-angle x-ray scattering, differential scanning calorimetry and microscopy. Microscopy revealed that studied starches, which varied in their amylose content and digestion kinetics, followed different modes of attack The multidisciplinary approach allowed the nanostructural changes detected by small-angle scattering in the course of enzymic breakdown to be correlated with changes in crystallinity and functional properties.

  1. Atomic-scale investigation of point defects and hydrogen-solute atmospheres on the edge dislocation mobility in alpha iron

    Energy Technology Data Exchange (ETDEWEB)

    Bhatia, M. A.; Solanki, K. N., E-mail: kiran.solanki@asu.edu [School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287 (United States); Groh, S. [Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg 09556 (Germany)

    2014-08-14

    In this study, we present atomistic mechanisms of 1/2 [111](11{sup ¯}0) edge dislocation interactions with point defects (hydrogen and vacancies) and hydrogen solute atmospheres in body centered cubic (bcc) iron. In metals such as iron, increases in hydrogen concentration can increase dislocation mobility and/or cleavage-type decohesion. Here, we first investigate the dislocation mobility in the presence of various point defects, i.e., change in the frictional stress as the edge dislocation interacts with (a) vacancy, (b) substitutional hydrogen, (c) one substitutional and one interstitial hydrogen, (d) interstitial hydrogen, (e) vacancy and interstitial hydrogen, and (f) two interstitial hydrogen. Second, we examine the role of a hydrogen-solute atmosphere on the rate of local dislocation velocity. The edge dislocation simulation with a vacancy in the compression side of the dislocation and an interstitial hydrogen atom at the tension side exhibit the strongest mechanical response, suggesting a higher potential barrier and hence, the higher frictional stress (i.e., ∼83% higher than the pure iron Peierls stress). In the case of a dislocation interacting with a vacancy on the compressive side, the vacancy binds with the edge dislocation, resulting in an increase in the friction stress of about 28% when compared with the Peierls stress of an edge dislocation in pure iron. Furthermore, as the applied strain increases, the vacancy migrates through a dislocation transportation mechanism by attaining a velocity of the same order as the dislocation velocity. For the case of the edge dislocation interacting with interstitial hydrogen on the tension side, the hydrogen atom jumps through one layer perpendicular to the glide plane during the pinning-unpinning process. Finally, our simulation of dislocation interactions with hydrogen show first an increase in the local dislocation velocity followed by a pinning of the dislocation core in the atmosphere, resulting in

  2. Investigations of the kinetics of surfactant-assisted growth of cobalt/copper multilayers

    Science.gov (United States)

    Peterson, Brennan Lovelace

    Surfactants---a term given to a broad family of surface additives used in thin film growth---provide a potentially useful tool for the deposition engineer. A long history of work on the field has produced a sometimes conflicting view of what surfactants do, and while their efficacy in improving magnetic films is well established, the attendant structural changes remain unclear. Early work on surfactant-assisted growth was generally confined to deposition at near equilibrium conditions: high temperature and very slow deposition rates on very smooth (single crystal) substrates. In the case of low temperature sputter deposition, the kinetic phenomena differ greatly from the near-equilibrium case: high rate, more interlayer diffusive pathways, high grain boundary density, and few well defined atomic steps. There are two major ideas which underlie and explain the use of surfactants. First, they are used to alter growth kinetics of a single material by changing the diffusion barriers on the growing surface. Second, surfactants alter the initial nucleation parameters in heteroepitaxial growth, which is often explained with reference to changes in the surface energy, gamma. Changes to these parameters result, in turn, to variations of the roughness and conformality of thin films grown with the assistance of surfactants. Finally, the roughness and conformality are critical for determining the performance of modern thin film magnetic sensors. As surfactants offer a way to alter the nucleation and growth kinetics, they offer tremendous potential benefits. However, before surfactants are trustworthy deposition tool, a better understanding of their structural effects and underlying surface energy and kinetic changes is necessary. In order to investigate these phenomena, DC magnetron sputtered [Co/Cu] multilayers were deposited on Si/SiO2 substrates using O2 , Ag, Pb, and In as surfactants. Oxygen was introduced during growth at partial pressures ranging from 10-9 to 10-6 Torr

  3. First-principles investigation of hydrogen storage capacity of Y-decorated porous graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Lihua, E-mail: yuanlh@lut.cn [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); School of Sciences, Lanzhou University of Technology, Lanzhou 730050 (China); Chen, Yuhong, E-mail: chenyh@lut.cn [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); School of Sciences, Lanzhou University of Technology, Lanzhou 730050 (China); Kang, Long [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Zhang, Cairong [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); School of Sciences, Lanzhou University of Technology, Lanzhou 730050 (China); Wang, Daobin; Wang, Chunni [School of Sciences, Lanzhou University of Technology, Lanzhou 730050 (China); Zhang, Meiling [School of Sciences, Lanzhou University of Technology, Lanzhou 730050 (China); School of Nuclear Science and Technology, Lanzhou university, 73000 (China); Wu, Xiaojuan [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China)

    2017-03-31

    Highlights: • The bridge of C–C bond is favorable site for a Y atom on the single side of PG and six H{sub 2} can be absorbed around it. • Two Y atoms can be stably adsorbed on the same side of one unit cell of PG, but there isn’t sufficient space for H{sub 2} absorbing around each Y atom. • The maximum number of absorbed Y atoms is two for double side of PG unit cell. • Fourteen H{sub 2} can be absorbed on the both sides of PG, and the hydrogen storage capacity is 7.87 wt.%. - Abstract: Based on first-principles method, the electron structure of porous graphene (PG) and adsorption ability of H{sub 2} molecular on Y-decorated porous graphene are investigated using CASTEP code. It is found that the bridge of C–C bond which connects two C hexagons is favorable site for a Y atom adsorbed on the single side of PG, and six H{sub 2} molecules can be absorbed around a Y atom with average adsorption energy of −0.297 eV/H{sub 2} computed by GGA-PBE functional. Though two Y atoms can be stably adsorbed on the same side of one unit cell of PG, there isn’t sufficient space for H{sub 2} absorbing around each Y atom. To improve capability of hydrogen storage, the unit cell of PG with single side should only contain one Y atom. For the case of double side of porous graphene, two Y atoms are preferably located above the center of the different C hexagon. Fourteen H{sub 2} molecules can be absorbed on both sides of PG, and the gravimetric hydrogen storage capacity is 7.87 wt.% with the average adsorption energy of −0.23 eV/H{sub 2}.

  4. A computational investigation of the red and blue shifts in hydrogen ...

    Indian Academy of Sciences (India)

    MITRADIP Das

    Keywords. Hydrogen bonding; blue shift; red shift; mulliken atomic charge. 1. Introduction ... to the most acceptable theory and has been explained further by Joseph and ... sity transfer from H to Y, an evidence of “anti-hydrogen bonds”.10.

  5. Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

    Czech Academy of Sciences Publication Activity Database

    Asadi, Z.; Asadi, M.; Zeinali, A.; Ranjkeshshorkaei, M.; Fejfarová, Karla; Eigner, Václav; Dušek, Michal; Dehnokhalaji, A.

    2014-01-01

    Roč. 126, č. 6 (2014), s. 1673-1683 ISSN 0974-3626 R&D Projects: GA ČR(CZ) GAP204/11/0809 Institutional support: RVO:68378271 Keywords : uranyl schiff base complexes * kinetic study * kinetics of thermal decomposition * X-ray crystallography * cyclic voltammetry Subject RIV: CA - Inorganic Chemistry Impact factor: 1.191, year: 2014

  6. Investigation of the structure dependence of diffusivity, solubility and permeability of hydrogen in hot-rolled low-carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Forcey, K S; Ross, D K [Birmingham Univ. (UK). Dept. of Physics; Iordanova, I A [Sofia Univ. (Bulgaria). Dept. of Solid State Physics

    1989-01-01

    A time-lag method for estimating the diffusivity, permeability and solubility of hydrogen in low-carbon hot-rolled steels has been applied. Oriani's model has been used to investigate and explain the effects of microstructure on the trapping of hydrogen. The results show that the initial microstructure of steel significantly affects the behaviour of hydrogen atoms. Of the three sites, namely: Dislocations, interstitial atoms and particles, the most effective traps seem to be interfaces between coarse particles and the matrix. (orig.).

  7. Investigation of the structure dependence of diffusivity, solubility and permeability of hydrogen in hot-rolled low-carbon steels

    International Nuclear Information System (INIS)

    Forcey, K.S.; Ross, D.K.; Iordanova, I.A.

    1989-01-01

    A time-lag method for estimating the diffusivity, permeability and solubility of hydrogen in low-carbon hot-rolled steels has been applied. Oriani's model has been used to investigate and explain the effects of microstructure on the trapping of hydrogen. The results show that the initial microstructure of steel significantly affects the behaviour of hydrogen atoms. Of the three sites, namely: Dislocations, interstitial atoms and particles, the most effective traps seem to be interfaces between coarse particles and the matrix. (orig.)

  8. Investigation of Local Hydrogen Risk in the RDT Compartment of OPR1000 under SBO Scenario

    International Nuclear Information System (INIS)

    Kim, Nam Kyung; Jeon, Joon Goo; Choi, Won Jun; Song, Kyu Sang; Jeun, Gyoo Dong; Kim, Sung Joong

    2016-01-01

    As TMI-2 and Fukushima accidents revealed, a high concentration of hydrogen in a nuclear power plant (NPP) could cause hydrogen combustion. In order to take follow-up measures, an average and local hydrogen concentration in the NPP containment are regulated below 0.1 using hydrogen mitigation system such as igniter and/or passive autocatalytic recombiner (PAR). During a severe accident, some compartments of the NPP containment temporarily may show peaks of the local hydrogen concentration over 0.1 depending on the geometry of the containment structure and hydrogen transportation path. For example, the compartment of a reactor drain tank (RDT) is connected to the pressurizer nozzle and if the relieved pressure drives the significant amount of steam and hydrogen, then substantial peaks of the hydrogen concentration can occur. Before the RPV failure under SBO scenario, the RDT compartment was the main region for hydrogen release due to the RDT break. Therefore, confirming the local hydrogen risk in the RDT compartment is very important to verify the integrity of the NPP containment. In this study, the local hydrogen risk in the RDT compartment of OPR1000 under SBO scenario was evaluated using MELCOR 1.8.6 code in terms of the hydrogen volume fraction and the Shapiro diagram. (1) The RDT compartment showed the peaks of the hydrogen volume fraction over 0.1. As a future work, the local hydrogen risk of the compartment of a steam generator (SG) needs to be analyzed under SBLOCA scenario. Because the SG compartment is also a main region of hydrogen release under SBLOCA scenario. In the long run, the analysis for the detailed hydrogen distribution, based on detailed modeling of the whole OPR1000 containment, needs to be performed.

  9. Kinetic formulae for muon-catalyzed fusion of hydrogen isotopes and their application to the description of the data for pure deuterium

    International Nuclear Information System (INIS)

    Gula, A.

    1987-01-01

    The data on the time distributions of muon-catalyzed fusion (μCF) events in pure deuterium targets published before 1987 are analysed using the kinetic formalism developed by the author and collaborators in a series of papers. The formalism enables one to describe these time distributions in an arbitrary mixture of hydrogen isotopes with strict inclusion of registration efficiency and dead time. The kinetic formulae for such distributions can be readily obtained using a prescription based on the theory of signal-flow graphs even for very complicated kinetic situations, thus, allowing one to avoid the simplifying assumptions which have been usually made in earlier analyses. Practically all important processes forming the muon-catalysis chain can be strictly taken into account in the approximation of constant transition rates. Consecutive μCF cycles can be described separately, which provides a useful tool in data analysis. The developed formalism is applied to the existing data for pure deuterium. First cycle-by-cycle time distributions reported for room temperature by the Gatchina group are analysed. 93 refs., 14 figs. (author)

  10. Investigation of Influential Parameters in Deep Oxidative Desulfurization of Dibenzothiophene with Hydrogen Peroxide and Formic Acid

    Directory of Open Access Journals (Sweden)

    Alireza Haghighat Mamaghani

    2013-01-01

    Full Text Available An effective oxidative system consisting of hydrogen peroxide, formic acid, and sulfuric acid followed by an extractive stage were implemented to remove dibenzothiophene in the simulated fuel oil. The results revealed such a great performance in the case of H2O2 in the presence of formic and sulfuric acids that led to the removal of sulfur compounds. Sulfuric acid was employed to increase the acidity of media as well as catalytic activity together with formic acid. The oxidation reaction was followed by a liquid-liquid extraction stage using acetonitrile as a polar solvent to remove produced sulfones from the model fuel. The impact of operating parameters including the molar ratio of formic acid to sulfur (, hydrogen peroxide to sulfur (, and the time of reaction was investigated using Box-Behnken experimental design for oxidation of the model fuel. A significant quadratic model was introduced for the sulfur removal as a function of effective parameters by the statistic analysis.

  11. Numerical and Experimental Investigation of Computed Tomography of Chemiluminescence for Hydrogen-Air Premixed Laminar Flames

    Directory of Open Access Journals (Sweden)

    Liang Lv

    2016-01-01

    Full Text Available Computed tomography of chemiluminescence (CTC is a promising technique for combustion diagnostics, providing instantaneous 3D information of flame structures, especially in harsh circumstance. This work focuses on assessing the feasibility of CTC and investigating structures of hydrogen-air premixed laminar flames using CTC. A numerical phantom study was performed to assess the accuracy of the reconstruction algorithm. A well-designed burner was used to generate stable hydrogen-air premixed laminar flames. The OH⁎ chemiluminescence intensity field reconstructed from 37 views using CTC was compared to the OH⁎ chemiluminescence distributions recorded directly by a single ICCD camera from the side view. The flame structures in different flow velocities and equivalence ratios were analyzed using the reconstructions. The results show that the CTC technique can effectively indicate real distributions of the flame chemiluminescence. The height of the flame becomes larger with increasing flow velocities, whereas it decreases with increasing equivalence ratios (no larger than 1. The increasing flow velocities gradually lift the flame reaction zones. A critical cone angle of 4.76 degrees is obtained to avoid blow-off. These results set up a foundation for next studies and the methods can be further developed to reconstruct 3D structures of flames.

  12. Direct-injection strategies for a hydrogen-fueled engine : an optical and numerical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, S.; Salazar, V. [Sandia National Labs, Albuquerque, NM (United States); Scarcelli, R.; Wallner, T. [Argonne National Lab, Argonne, IL (United States)

    2009-07-01

    Vehicles with hydrogen-fueled engines are competitive with systems based on fuel cells. There is a lack of fundamental knowledge about in-cylinder processes in hydrogen direct injection engines. This presentation discussed a study that used a variety of injector configurations to establish a broad database. A light-load conditions that can profit from stratification was investigated. Several results were presented, including the 5-hole nozzle produced an asymmetric jet pattern which may be good for late injection. Very lean regions in the wake of the transient jets were found to be similar to those found in diesel injection. The 13-hole nozzle demonstrated complete jet collapse, consistent with Schlieren imaging by Petersen. Stratification made efficiency sensitive to the targeting of the single-hole injector. Computational fluid dynamics with a commercially available code aimed to improve the process of design optimization. The simulation predicted less fuel dispersion than was experimentally measured. Details of the fuel penetration were captured. It was concluded that for the single-hole nozzle, the pre-spark fuel distribution is consistent with results from the fired engine. tabs., figs.

  13. TEM studies of nanostructure in melt-spun Mg-Ni-La alloy manifesting enhanced hydrogen desorbing kinetics

    International Nuclear Information System (INIS)

    Tanaka, K.; Miwa, T.; Sasaki, K.; Kuroda, K.

    2009-01-01

    The hydrogen storage properties of a magnesium-rich Mg-Ni-La alloy prepared by melt-spinning are significantly improved by nanostructure formation during crystallization and activation. It can absorb and desorb ∼5 wt% hydrogen at temperatures as low as 200 deg. C in moderate time periods. Transmission electron microscopic (TEM) studies on this alloy indicate that the nanostructure, consisting of LaH 3 and Mg 2 NiH 4 nano-particles dispersed homogeneously in MgH 2 matrices after hydrogenation, is rather stable at temperatures below 300 deg. C but undergoes coarsening and segregation of these particles and matrices above ∼400 deg. C. These structural changes have been confirmed by electron energy-loss spectroscopic (EELS) imaging as well as high-resolution TEM techniques. A new EELS peak associated with a plasmon excitation in the MgH 2 phase (H-plasmon) is found for the first time in this study. By imaging the H-plasmon peak, the hydrogen distribution in the alloy has been clearly visualized. We have succeeded in observing the hydrogen desorption process at ∼400 deg. C in-situ in the microscope using this EELS imaging technique.

  14. In-depth investigation on the pyrolysis kinetics of raw biomass. Part I: kinetic analysis for the drying and devolatilization stages.

    Science.gov (United States)

    Chen, Dengyu; Zheng, Yan; Zhu, Xifeng

    2013-03-01

    An in-depth investigation was conducted on the kinetic analysis of raw biomass using thermogravimetric analysis (TGA), from which the activation energy distribution of the whole pyrolysis process was obtained. Two different stages, namely, drying stage (Stage I) and devolatilization stage (Stage II), were shown in the pyrolysis process in which the activation energy values changed with conversion. The activation energy at low conversions (below 0.15) in the drying stage ranged from 10 to 30 kJ/mol. Such energy was calculated using the nonisothermal Page model, known as the best model to describe the drying kinetics. Kinetic analysis was performed using the distributed activation energy model in a wide range of conversions (0.15-0.95) in the devolatilization stage. The activation energy first ranged from 178.23 to 245.58 kJ/mol and from 159.66 to 210.76 kJ/mol for corn straw and wheat straw, respectively, then increasing remarkably with an irregular trend. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Investigations on the kinetics of the oxygen reduction in high temperature fuel cells

    International Nuclear Information System (INIS)

    Erning, J.W.

    1998-07-01

    Lanthan-Strontium-Manganite perowskites are the most widespread materials in use for solid oxide fuel cell cathodes. The electrode reaction taking place, i.e. the reduction of oxygen supplied by air, was investigated by electrochemical means to obtain further knowledge about the electrode processes. The high activation energy of this reaction (200 kJ/mol), preventing lower operation temperatures of the SOFC, was the starting point for the investigation. Quasi steady state current voltage measurements and impedance spectroscopy were performed in a three electrode configuration. The electrodes were of circular shape with a diameter of 10 mm. The preparation was made by screen printing as well as wet powder spraying onto plates made of Yttria-stabilized zirconia. Perowskite powders of varying chemical and stoichiometric composition were used. To obtain higher power densities and, more important, lower apparent activation energies, catalytic layers were added at the interface electrode/electrolyte. Additionally, a less complex system, a model electrode/electrolyte setup made from single-crystal YSZ as electrolyte and gold in liquid and solid state as electrode was developed to create a better defined system. This setup was used to investigate the behaviour of the electrode/electrolyte interface. Reliable, reproducible results could be obtained using either setup. The experimental conditions i.e. oxygen partial pressure, temperature and overpotential were varied in order to determine the kinetic properties of the electrodes. Apparent activation energies, pre-exponential factors, apparent charge-transfer coefficients and electrochemical orders of reaction were calculated from the current-voltage data in order to propose possible reaction steps. (orig.)

  16. Investigations on sysnthesis, characterization and hydrogenation behaviour of the spin- and thermal-melted versions of LaNi{sub 5-x}Si{sub x}(x=0.1, 0.3, 0.5) hydrogen storage materials

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, S.; Srivastava, O.N. [Banaras Hindu Univ., Varanasi (India). Dept. of Physics

    1998-03-06

    The present study deals with investigations on the synthesis and characterisation of negative electrode material for high energy density Ni-MH battery. The hydrogen storage material (MH) has been synthesised trough normal casting and melt-spinning techniques. In LaNi{sub 5}/MmNi{sub 5} family various substitutions like Al, Mn, Co have been studied. The substitution of metalloid like Si is known to be very helpful in improving several hydrogenation properties. In the present study, the Si substituted versions of AB{sub 5}-type storage materials typified by LaNi{sub 5-x}Si{sub x} (x=0.1, 0.3, 0.5) habe been investigated. A comparison between the present material and the conventional AB{sub 5}-type material MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4} has been made which has been previously studied. The main features revealed by XRD characterisations are the existence of the free Ni and Si together with AB{sub 5} material for all the three compositions. These free Ni and Si were found to disappear and yield, giving rise to a singular material after hydrogenation. The melt-spun version of the material was found to grow invariably in a direction perpendicular to the c-axis. The kinetics and activation process was better for the melt-spun version of the LaNi{sub 4.7}Si{sub 0.3} alloy than its thermally-melted counterpart (bulk) as well as to the alloy MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4}. For example, the kinetics of the melt-spun version of LaNi{sub 4.7}Si{sub 0.3} is 60% faster than its bulk version and 70% faster than the melt-spun version of MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4}. Similarly, the melt-spund version of the alloy LaNi{sub 4.7}Si{sub 0.3} gets activated in the 2nd cycle itself where as the alloy MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4} attains this stage only in the 6th cycle. (orig.) 13 refs.

  17. The investigation of the kinetics of hydrochemical oxidation of metal sulphides with the aim of determination of the optimal conditions for the selective extraction of molybdenum from ores

    Directory of Open Access Journals (Sweden)

    Lutsik V.

    2005-01-01

    Full Text Available The kinetics of the oxidation of molybdenyte, pyrite and sphalerite in solutions of nitric acid, hydrogen peroxide, and sodium hypochlorite was studied by the rotating disk method. The influence of the molar concentration of reagent, pH of solution, temperature, disk rotation frequency, and duration of measurements on the specific rate of hydrochemical oxidation of sulpfides was determined. The kinetic models allowing to calculate the dissolution rate of sulphides when these parameters change simultaneously were obtained. The conditions of kinetically and diffusion-controlled processes were detected. The details of mechanism of the studied processes were revealed. The nature of intermediate solid products, the reasons and the conditions of their formation as well as the character of their influence on the kinetics of dissolution processes were determined. The probable schemes of interactions corresponding to the observable kinetic dependences were offered. The conditions of the effective and selective molybdenum leaching directly from ore without its concentration were found.

  18. The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations

    Directory of Open Access Journals (Sweden)

    A. Aiuppa

    2007-01-01

    Full Text Available Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcano in eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in the Aeolian Islands (northern Sicily. Sulphur dioxide (SO2, hydrogen sulphide (H2S, hydrogen chloride (HCl and hydrogen fluoride (HF concentrations in the volcanic plumes (typically several minutes to a few hours old were repeatedly determined at distances from the summit vents ranging from 0.1 to ~10 km, and under different environmental conditions. At both volcanoes, acidic gas concentrations were found to decrease exponentially with distance from the summit vents (e.g., SO2 decreases from ~10 000 μg/m3at 0.1 km from Etna's vents down to ~7 μg/m3 at ~10 km distance, reflecting the atmospheric dilution of the plume within the acid gas-free background troposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showed no systematic changes with plume aging, and fit source compositions within analytical error. Assuming that SO2 losses by reaction are small during short-range atmospheric transport within quiescent (ash-free volcanic plumes, our observations suggest that, for these short transport distances, atmospheric reactions for H2S and halogens are also negligible. The one-dimensional model MISTRA was used to simulate quantitatively the evolution of halogen and sulphur compounds in the plume of Mt. Etna. Model predictions support the hypothesis of minor HCl chemical processing during plume transport, at least in cloud-free conditions. Larger

  19. Gaucher disease: Physical, kinetic and immunologic investigations of human and canine acid β-glucosidase

    International Nuclear Information System (INIS)

    Fabbro, D.E.

    1988-01-01

    Kinetic and immunologic techniques were developed to investigate the nature of the acid β-glucosidase (β-Glc) defects which results in human and canine Gaucher disease (GD). Two new affinity columns, using the potent inhibitors of β-Glc (N-alkyl-deoxynojirimycins) as affinity ligands, were synthesized and methods were developed to obtain homogeneous β-Glc from normal human placenta. Polyclonal and monoclonal (representing 14 different epitopes from 18 clones) antibodies were produced to the pure normal β-Glc. Monospecific polyclonal IgG and tritiated-bromo-conduritol B epoxide ([ 3 H]Br-CBE), a specific covalent active site directed inhibitor of β-Glc, were used to quantitate the functional catalytic sites in normal and Type 1 Ashkenazi Jewish GD (AJGD) enzyme preparations: The k cat values for several new substrates with the mutant enzymes from spleen were about 1.5-fold less than the respective normal enzyme, indicating a nearly normal catalytic capacity of the mutant enzymes. Immunoblotting studies with polyclonal or several monoclonal antibodies indicated three molecular forms of β-Glc (M r = 67,000, 62,000 to 65,000 and 58,000) in fibroblast extracts from normals and Type 1 AJGD patients. In comparison, only one form of cross-reacting immunologic material (CRIM) was detected in fibroblast extracts from Types 2 and 3 or several non-Jewish Type 1 GD patients

  20. Mechanistic Investigation of Oxidation of Phenylpropanolamine with N-Bromobenzenesulfonamide in Alkaline Medium: A Kinetic Approach

    Directory of Open Access Journals (Sweden)

    Ningegowda Prasad

    2008-01-01

    Full Text Available The kinetics of oxidation of phenylpropanolamine (PPA with sodium N-bromobenzenesulfonamide or bromamine-B (BAB has been investigated in alkaline medium at 308 K. The oxidation reaction obeys the rate law, – d[BAB]/dt = k [BAB] [PPA]x [OH-], where x is less than unity. The variation of ionic strength of the medium, addition of the reduction product, benzenesulfonamide, and chloride ion had no pronounced effect on the reaction rate. Decrease of dielectric permittivity of the medium by increasing the CH3CN content increased the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated from the Arrhenius plot. The stiochiometry of the reaction was found to be 1:1, and the oxidation product of phenylpropanolamine was identified as benzaldehyde and ethylideneamine. The rate decreased in D2O medium and the normal isotope effect k' (H2O / k' (D2O is 2.18. Proton inventory studies have been made in H2O - D2O mixtures. Formation and decomposition constant of BAB-PPA complexes in the reaction scheme have been determined. The conjugate acid, C6H5SO2NHBr is assumed to be the reactive species. The proposed mechanism and the derived rate law are consistent with the observed experimental results.

  1. Theoretical Investigation of Kinetic Processes in Small Radicals of Importance in Combustion

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, Millard [Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry and Biochemistry; Dagdigian, Paul J. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Chemistry

    2017-12-12

    Our group studies inelastic and reactive collisions of small molecules, focusing on radicals important in combustion environments. The goal is the better understanding of kinetic processes that may be difficult to access experimentally. An essential component is the accurate determination and fitting of potential energy surfaces (PESs). After fitting the ab initio points to obtain global PESs, we treat the dynamics using time-independent (close-coupling) methods. Cross sections and rate constants for collisions of are determined with our Hibridon program suite . We have studied energy transfer (rotationally, vibrationally, and/or electronically inelastic) in small hydrocarbon radicals (CH2 and CH3) and the CN radical. We have made a comparison with experimental measurements of relevant rate constants for collisions of these radicals. Also, we have calculated accurate transport properties using state-of-the-art PESs and to investigate the sensitivity to these parameters in 1-dimensional flame simulations. Of particular interest are collision pairs involving the light H atom.

  2. Investigation on the recombination kinetics of the pyrolytic free-radicals in the irradiated polyimide

    International Nuclear Information System (INIS)

    Sun Chengyue; Wu Yiyong; Yue Long; Shi Yaping; Xiao Jingdong

    2012-01-01

    Highlights: ► Free radicals behavior was exposure during the irradiation and anneal during the post storage. ► Both of the recombination and oxygen reaction affect the post-annealing evolution of free radicals. ► The activation energy and the surface reaction rate were calculated by the analysis of the free radical anneal process. - Abstract: The free radical behavior of 60 and 110 keV proton-irradiated polyimide were investigated using electron paramagnetic resonance measurements. The results indicate that during proton irradiation, a type of pyrolytic carbon free radical was formed with a g value of 2.0025. The radical population was found, after proton irradiation to decrease in a combination of an exponential and linear modes with an annealing time in the range of 50–120 °C. The exponential part indicated a radical recombination process while the linear part is due to the reaction of the radical with the ambient. Using the annealing results, the recombination activation energy of the radicals was determined as 12.4 ± 0.2 and 17.6 ± 0.2 kJ/mol for 60 and 110 keV irradiated polyimide, respectively, with a surface reaction rate of about 0.02/h. It is possible that the kinetic study presented here is used as one of the criteria for predicting the optical properties of polyimide material in spacecraft. The mechanism of the free radical evolution will be discussed in this paper.

  3. Kinetic and mechanistic investigations of the degradation of sulfamethazine in heat-activated persulfate oxidation process.

    Science.gov (United States)

    Fan, Yan; Ji, Yuefei; Kong, Deyang; Lu, Junhe; Zhou, Quansuo

    2015-12-30

    Sulfamethazine (SMZ) is widely used in livestock feeding and aquaculture as an antibiotic agent and growth promoter. Widespread occurrence of SMZ in surface water, groundwater, soil and sediment has been reported. In this study, degradation of SMZ by heat-activated persulfate (PS) oxidation was investigated in aqueous solution. Experimental results demonstrated that SMZ degradation followed pseudo-first-order reaction kinetics. The pseudo-first-order rate constant (kobs) was increased markedly with increasing concentration of PS and temperature. Radical scavenging tests revealed that the predominant oxidizing species was SO4·(-) with HO playing a less important role. Aniline moiety in SMZ molecule was confirmed to be the reactive site for SO4·(-) attack by comparison with substructural analogs. Nontarget natural water constituents affected SMZ removal significantly, e.g., Cl(-) and HCO3(-) improved the degradation while fulvic acid reduced it. Reaction products were enriched by solid phase extraction (SPE) and analyzed by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). 6 products derived from sulfonamide S--N bond cleavage, aniline moiety oxidation and Smiles-type rearrangement were identified, and transformation pathways of SMZ oxidation were proposed. Results reveal that heat-activated PS oxidation could be an efficient approach for remediation of water contaminated by SMZ and related sulfonamides. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Investigation of the combustion kinetics and polycyclic aromatic hydrocarbon emissions from polycaprolactone combustion.

    Science.gov (United States)

    Chien, Y C; Yang, S H

    2013-01-01

    Polycaprolactone (PCL) is one of the most attractive biodegradable plastics that has been widely used in medicine and agriculture fields. Because of the large increase in biodegradable plastics usage, the production of waste biodegradable plastics will be increasing dramatically, producing a growing environmental problem. Generally, waste PCL is collected along with municipal solid wastes and then incinerated. This study investigates the combustion kinetics and emission factors of 16 US Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs) in the PCL combustion. Experimentally, two reactions are involved in the PCL combustion process, possibly resulting in the emission of carbon dioxide, propanal, protonated caprolactone and very small amounts of PAH produced by incomplete combustion. The intermediate products may continuously be oxidized to form CO2. The emission factors for 16 US EPA priority PAHs are n.d. -2.95 microg/g, which are much lower than those of poly lactic acid and other plastics combustion. The conversion of PCL is 100%. Results from this work suggest that combustion is a good choice for the waste PCL disposal.

  5. Kinetic Investigations of SiMn Slags From Different Mn Sources

    Science.gov (United States)

    Kim, Pyunghwa Peace; Tangstad, Merete

    2018-03-01

    The kinetics of MnO and SiO2 reduction were investigated for Silicomanganese (SiMn) slags using a Thermogravimetric analysis (TGA) between 1773 K and 1923 K (1500 °C and 1650 °C) under CO atmospheric pressure. The charge materials were based on Assmang ore and HC FeMn Slag. Rate models for MnO and SiO2 reduction were applied to describe the metal-producing rates, as shown by the following equations: r_{MnO} = k_{MnO} × A × ( {a_{MnO} - {a_{Mn} }/{K_{T }}} ) r_{{{SiO}2 }} = k_{SiO2} × A × ( {a_{{{SiO}2 }} - {a_{Si} }/{K_{T }}} ). The results show that the choice of raw materials in the charge considerably affected the reduction rate of MnO and SiO2. The highest reduction rate was found to be from charges using HC FeMn slag. The difference in the driving forces was insignificant among the SiMn slags, and the similar slag viscosities could not explain the different reduction rates. Instead, the difference is attributed to small amounts of sulfur and the amount of iron in the charge. In addition, the rate models were applicable to describe the reduction of MnO and SiO2 in SiMn slags.

  6. A kinetic Monte Carlo approach to investigate antibiotic translocation through bacterial porins

    International Nuclear Information System (INIS)

    Ceccarelli, Matteo; Ruggerone, Paolo; Vargiu, Attilio V

    2012-01-01

    Many relevant biological processes take place on time scales not reachable by standard all-atom computer simulations. The translocation of antibiotics through non-specific bacterial porins is an example. Microscopic effects compete to determine penetration routes and, consequently, free energy barriers to be overcome. Since bacteria can develop resistance to treatment also by reducing their antibiotic permeability, to understand the microscopic aspects of antibiotic translocation is an important step to rationalize drug design. Here, to investigate the translocation we propose a complete numerical model that combines the diffusion-controlled rate theory and a kinetic Monte Carlo scheme based on both experimental data and microscopically well-founded all-atom simulations. Within our model, an antibiotic translocating through an hour-glass-shaped channel can be described as a molecule moving on a potential of mean force featuring several affinity sites and a high central barrier. The implications of our results for the characterization of antibiotic translocation at in vivo concentrations are discussed. The presence of an affinity site close to the mouth of the channel seems to favor the translocation of antibiotics, the affinity site acting as a particle reservoir. Possible connections between results and the appearance of mutations in clinical strains are also outlined. (paper)

  7. Design of a high-pressure single pulse shock tube for chemical kinetic investigations

    International Nuclear Information System (INIS)

    Tranter, R. S.; Brezinsky, K.; Fulle, D.

    2001-01-01

    A single pulse shock tube has been designed and constructed in order to achieve extremely high pressures and temperatures to facilitate gas-phase chemical kinetic experiments. Postshock pressures of greater than 1000 atmospheres have been obtained. Temperatures greater than 1400 K have been achieved and, in principle, temperatures greater than 2000 K are easily attainable. These high temperatures and pressures permit the investigation of hydrocarbon species pyrolysis and oxidation reactions. Since these reactions occur on the time scale of 0.5--2 ms the shock tube has been constructed with an adjustable length driven section that permits variation of reaction viewing times. For any given reaction viewing time, samples can be withdrawn through a specially constructed automated sampling apparatus for subsequent species analysis with gas chromatography and mass spectrometry. The details of the design and construction that have permitted the successful generation of very high-pressure shocks in this unique apparatus are described. Additional information is provided concerning the diaphragms used in the high-pressure shock tube

  8. Kinetic investigation and lifetime prediction of Cs-NIPAM-MBA-based thermo-responsive hydrogels.

    Science.gov (United States)

    Othman, Muhammad Bisyrul Hafi; Khan, Abbas; Ahmad, Zulkifli; Zakaria, Muhammad Razlan; Ullah, Faheem; Akil, Hazizan Md

    2016-01-20

    This study attempted to clarify the influence of a cross-linker, N,N-methylenebisacrylamide (MBA), and N-isopropylacrylamide (NIPAM) on the non-isothermal kinetic degradation, solid state and lifetime of hydrogels using the Flynn-Wall-Ozawa (F-W-O), Kissinger, and Coats-Redfern (C-Red) methods. The series of dual-responsive Cs-PNIPAM-MBA microgels were synthesized by soapless-emulsion free radical copolymerization in an aqueous medium at 70 °C. The thermal properties were investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) under nitrogen atmosphere. The apparent activation energy using the chosen Flynn-Wall-Ozawa and Kissinger methods showed that they fitted each other. Meanwhile, the type of solid state mechanism was determined using the Coats-Redfern method proposed for F1 (pure Cs) and F2 (Cs-PNIPAM-MBA hydrogel series) types, which comprise random nucleation with one nucleus reacting on individual particles, and random nucleation with two nuclei reacting on individual particles, respectively. On average, a higher Ea was attributed to the greater cross-linking density of the Cs hydrogel. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Investigation of the degradation of a thin-film hydrogenated amorphous silicon photovoltaic module

    Energy Technology Data Exchange (ETDEWEB)

    van Dyk, E.E.; Audouard, A.; Meyer, E.L. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Woolard, C.D. [Department of Chemistry, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2007-01-23

    The degradation of a thin-film hydrogenated single-junction amorphous silicon (a-Si:H) photovoltaic (PV) module has been studied. We investigated the different modes of electrical and physical degradation of a-Si:H PV modules by employing a degradation and failure assessment procedure used in conjunction with analytical techniques, including, scanning electron microscopy (SEM) and thermogravimetry. This paper reveals that due to their thickness, thin films are very sensitive to the type of degradation observed. Moreover, this paper deals with the problems associated with the module encapsulant, poly(ethylene-co-vinylacetate) (EVA). The main objective of this study was to establish the influence of outdoor environmental conditions on the performance of a thin-film PV module comprising a-Si:H single-junction cells. (author)

  10. Investigation of advanced nanostructured multijunction photoanodes for enhanced solar hydrogen generation via water splitting

    Science.gov (United States)

    Ishihara, Hidetaka

    As the worldwide demand for fossil-based fuel increases every day and the fossil reserve continues to be depleted, the need for alternative/renewable energy sources has gained momentum. Electric, hybrid, and hydrogen cars have been at the center of discussion lately among consumers, automobile manufacturers, and politicians, alike. The development of a fuel-cell based engine using hydrogen has been an ambitious research area over the last few decades-ever since Fujishima showed that hydrogen can be generated via the solar-energy driven photo-electrolytic splitting of water. Such solar cells are known as Photo-Electro-Chemical (PEC) solar cells. In order to commercialize this technology, various challenges associated with photo-conversion efficiency, chemical corrosion resistance, and longevity need to be overcome. In general, metal oxide semiconductors such as titanium dioxide (TiO 2, titania) are excellent candidates for PEC solar cells. Titania nanotubes have several advantages, including biocompatibility and higher chemical stability. Nevertheless, they can absorb only 5-7% of the solar spectrum which makes it difficult to achieve the higher photo-conversion efficiency required for successful commercial applications. A two-prong approach was employed to enhance photo-conversion efficiency: 1) surface modification of titania nanotubes using plasma treatment and 2) nano-capping of the titania nanotubes using titanium disilicide. The plasma surface treatment with N2 was found to improve the photo-current efficiency of titania nanotubes by 55%. Similarly, a facile, novel approach of nano-capping titania nanotubes to enhance their photocurrent response was also investigated. Electrochemically anodized titania nanotubes were capped by coating a 25 nm layer of titanium disilicide using RF magnetron sputtering technique. The optical properties of titania nanotubes were not found to change due to the capping; however, a considerable increase (40%) in the photocurrent

  11. Investigation of hydrogen generation in a three reactor chemical looping reforming process

    International Nuclear Information System (INIS)

    Khan, Mohammed N.; Shamim, Tariq

    2016-01-01

    Highlights: • Three-reactor based chemical looping reforming system for hydrogen production. • Investigation of operating parameters using a system-level model. • Optimum operating conditions for hydrogen production are identified. • Different operating parameters affect the reactor temperatures differently. - Abstract: Chemical looping reforming (CLR) is a relatively new method to produce hydrogen (H_2) and is also used as an energy conversion method for solid, liquid or gaseous fuels. There are various advantages of this method such as inherent carbon dioxide (CO_2) capture, minimal NOx emissions and the H_2 production. In this process, there is no direct contact between the fuel and oxidizer. This method utilizes oxygen from an oxygen carrier which may be a transition metal. The idea is to split the combustion process into three separate sub-processes by employing three separate reactors: air reactor where the oxygen carrier is oxidized by air, fuel reactor where natural gas is oxidized to produce a stream of CO_2 and H_2O and steam reactor where the steam is reduced to produce H_2. In this study, a thermodynamic model with iron oxides as oxygen carrier has been developed using Aspen Plus by employing conservation of mass and energy for all the components of the CLR system. The developed model was employed to investigate the effect of various operating parameters such as mass flow rates of air, fuel, steam and oxygen carrier and fraction of inert material on H_2 and CO_2 production and key reactor temperatures. The results show that the H_2 production increases with the increase in air, fuel and steam flow rates up to a certain limit and stays constant for higher flow rates. The CO_2 production follows a similar trend. Similarly, the H_2 production also increases with the increase in oxide flow rate and fraction of inert material up to a particular value, but then decrease for higher oxide flow rates and inert fractions. Reactor temperatures were also

  12. Kinetic and thermodynamic investigation on ascorbate oxidase activity and stability of a Cucurbita maxima extract.

    Science.gov (United States)

    Porto, Tatiana S; Porto, Camila S; Cavalcanti, Maria T H; Filho, José L Lima; Perego, Patrizia; Porto, Ana L F; Converti, Attilio; Pessoa, Adalberto

    2006-01-01

    The kinetic and thermodynamic properties of ascorbate oxidase (AO) activity and stability of a Cucurbita maxima extract were investigated. Activity tests performed at 25 degrees C using initial ascorbic acid concentration in the range 50-750 M allowed estimating the Michaelis constant for this substrate (Km = 126 microM) and the maximum initial rate of ascorbic acid oxidation (A0,max = 1.57 mM min-1). The main thermodynamic parameters of the enzyme reaction (DeltaH* = 10.3 kJ mol-1; DeltaG* = 87.2 kJ mol-1; DeltaS* = -258 J mol-1 K-1) were estimated through activity tests performed at 25-48 C. Within such a temperature range, no decrease in the initial reaction rate was detected. The long-term thermostability of the raw extract was then investigated by means of residual activity tests carried out at 10-70 degrees C, which allowed estimating the thermodynamic parameters of the irreversible enzyme inactivation as well (DeltaH*D = 51.7 kJ mol-1; DeltaG*D = 103 kJ mol-1; S*D = -160 J mol-1 K-1). Taking into account the specific rate of AO inactivation determined at different temperatures, we also estimated the enzyme half-life (1047 min at 10 degrees C and 21.2 min at 70 degrees C) and predicted the integral activity of a continuous system using this enzyme preparation. This work should be considered as a preliminary attempt to characterize the AO activity of a C. maxima extract before its concentration by liquid-liquid extraction techniques.

  13. A Microscale Approach to Chemical Kinetics in the General Chemistry Laboratory: The Potassium Iodide Hydrogen Peroxide Iodine-Clock Reaction

    Science.gov (United States)

    Sattsangi, Prem D.

    2011-01-01

    A microscale laboratory for teaching chemical kinetics utilizing the iodine clock reaction is described. Plastic pipets, 3 mL volume, are used to store and deliver precise drops of reagents and the reaction is run in a 24 well plastic tray using a total 60 drops of reagents. With this procedure, students determine the rate of reaction and the…

  14. Protein and Peptide Gas-phase Structure Investigation Using Collision Cross Section Measurements and Hydrogen Deuterium Exchange

    Science.gov (United States)

    Khakinejad, Mahdiar

    Protein and peptide gas-phase structure analysis provides the opportunity to study these species outside of their explicit environment where the interaction network with surrounding molecules makes the analysis difficult [1]. Although gas-phase structure analysis offers a unique opportunity to study the intrinsic behavior of these biomolecules [2-4], proteins and peptides exhibit very low vapor pressures [2]. Peptide and protein ions can be rendered in the gas-phase using electrospray ionization (ESI) [5]. There is a growing body of literature that shows proteins and peptides can maintain solution structures during the process of ESI and these structures can persist for a few hundred milliseconds [6-9]. Techniques for monitoring gas-phase protein and peptide ion structures are categorized as physical probes and chemical probes. Collision cross section (CCS) measurement, being a physical probe, is a powerful method to investigate gas-phase structure size [3, 7, 10-15]; however, CCS values alone do not establish a one to one relation with structure(i.e., the CCS value is an orientationally averaged value [15-18]. Here we propose the utility of gas-phase hydrogen deuterium exchange (HDX) as a second criterion of structure elucidation. The proposed approach incudes extensive MD simulations to sample biomolecular ion conformation space with the production of numerous, random in-silico structures. Subsequently a CCS can be calculated for these structures and theoretical CCS values are compared with experimental values to produce a pool of candidate structures. Utilizing a chemical reaction model based on the gas-phase HDX mechanism, the HDX kinetics behavior of these candidate structures are predicted and compared to experimental results to nominate the best in-silico structures which match (chemically and physically) with experimental observations. For the predictive approach to succeed, an extensive technique and method development is essential. To combine CCS

  15. Experimental and Kinetic Investigation of the Influence of OH Groups on NOX Formation

    KAUST Repository

    Bohon, Myles

    2016-05-04

    This work investigates the influence of one or more OH groups present on the fuel molecule and the resultant formation of NOX emissions. Combustion of oxygenated fuels has been increasing globally and such fuels offer significant potential in the reduction of pollutant emissions. One such emission class is the oxides of nitrogen, which typically form through a combination of two regimes: the thermal and non-thermal mechanisms. While thermal NO formation can be reduced by lowering the combustion temperature, non-thermal NO formation is coupled to the fuel chemistry. An experimental and computational investigation of NOX formation in three different burner configurations and under a range of equivalence ratios and temperature regimes explored the differences in NO formation. Measurements of temperature profiles and in-flame species concentrations, utilizing both probed and non-intrusive laser based techniques, allowed for the investigation of NO formation through non-thermal pathways and the differences that exist between fuels with varying numbers of OH groups. The first burner configuration was composed of a high swirl liquid spray burner with insulted combustion chamber walls designed specifically for the combustion of low energy density fuels. In this system the combustion of alcohols and glycerol (the largest by-product of biodiesel production), along with other fuels with multiple hydroxyl groups, was studied. Measurements of the mean flame temperature and exhaust gas measurements of NOX showed significant reductions in non-thermal NO concentrations with increasing numbers of OH groups. An accompanying modeling study and detailed reaction path analysis showed that fuel decomposition pathways through formaldehyde were shown a preference due to the presence of the OH groups which resulted in reduced contributions to the hydrocarbon radical pools subsequent reductions to the Prompt NO mechanism. Two burner configurations with reduced dimensionality facilitated

  16. Purification of 6-phosphogluconate dehydrogenase from parsley (Petroselinum hortense) leaves and investigation of some kinetic properties.

    Science.gov (United States)

    Demir, Hülya; Ciftçi, Mehmet; Küfrevioğlu, O Irfan

    2003-02-01

    In this study, 6-phosphogluconate dehydrogenase (E.C.1.1.44; 6PGD) was purified from parsley (Petroselinum hortense) leaves, and analysis of the kinetic behavior and some properties of the enzyme were investigated. The purification consisted of three steps that are preparation of homogenate ammonium sulfate fractionation and on DEAE-Sephadex A50 ion exchange. The enzyme was obtained with a yield of 49% and had a specific activity of 18.3 U (mg proteins)(-1) (Lehninger, A.L.; Nelson, D.L.; Cox, M.M. Principles of Biochemistry, 2nd Ed.; Worth Publishers Inc.: N.Y., 2000, 558-560). The overall purification was about 339-fold. A temperature of +4 degrees C was maintained during the purification process. Enzyme activity was spectrophotometrically measured according to the Beutler method at 340 mn. In order to control the purification of the enzyme, SDS-polyacrylamide gel electrophoresis was carried out in 4% and 10% acrylamide for stacking and running gel, respectively. SDS-polyacrylamide gel electrophoresis showed a single band for enzyme. The molecular weight was found to be 97.5 kDa by Sephadex G-150 gel filtration chromatography. A protein band corresponding to a subunit molecular weight of 24.1 kDa was obtained on SDS-polyacrylamide gel electrophoresis. For the enzymes, the stable pH, optimum pH, and optimum temperature were found as 8.0, 8.0, and 50 degrees C, respectively. In addition, KM and Vmax values for NADP+ and G6-P at optimum pH and 25 degrees C were determined by means of Lineweaver-Burk plots.

  17. Kinetic investigation of myeloperoxidase upon interaction with copper, cadmium, and lead ions

    International Nuclear Information System (INIS)

    Shabani, M.; Ani, M.; Movahedian, A.; Samsam Shariat, Z. A.

    2011-01-01

    Myeloperoxidase, which is abundantly expressed in neutrophils, catalyzes the formation of a number of reactive oxidant species. However, evidence has emerged that Myeloperoxidase-derived oxidants contribute to tissue damage and initiation and propagation of inflammatory diseases, particularly, cardiovascular diseases. Therefore, studying the regulatory mechanisms of the enzyme activity is of great importance. For clarifying some possible mechanism of the enzyme activity, kinetic investigations of Myeloperoxidase in the presence of Copper, Cadmium, and Lead ions were carried out in vitro. Methods: Myeloperoxidase was partially purified from human white blood cells using ion-exchange and gel-filtration chromatography techniques. Its activity was measured spectrophotometrically by using tetramethyl benzidine as substrate. Results: Purified enzyme had a specific activity of 21.7 U/mg protein with a purity index of about 0.71. Copper inhibited Myeloperoxidase activity progressively up to a concentration of 60 m M at which about 80% of inhibition achieved. The inhibition was non-competitive with respect to tetramethyl benzidine. An inhibitory constant (Ki) of about 19 m M was calculated from the slope of repot. Cadmium and Lead did not show any significant inhibitory effect on the enzyme activity. Conclusion: The results of the present study may indicate that there are some places on the enzyme and enzyme-substrate complex for Copper ions. Binding of Copper ions to these places result in conformational changes of the enzyme and thus, enzyme inhibition. This inhibitory effect of Copper on the enzyme activity might be considered as a regulatory mechanism on Myeloperoxidase activity.

  18. Simulation of uranium oxides reduction kinetics by hydrogen. Reactivities of germination and growth; Modelisation de la cinetique de reduction d`oxydes d`uranium par l`hydrogene. Reactivites de germination et de croissance

    Energy Technology Data Exchange (ETDEWEB)

    Brun, C

    1997-12-04

    The aim of this work is to simulate the reduction by hydrogen of the tri-uranium octo-oxide U{sub 3}O{sub 8} (obtained by uranium trioxide calcination) into uranium dioxide. The kinetics curves have been obtained by thermal gravimetric analysis, the hydrogen and steam pressures being defined. The geometrical modeling which has allowed to explain the trend of the kinetics curves and of the velocity curves is an anisotropic germination-growth modeling. The powder is supposed to be formed of spherical grains with the same radius. The germs of the new UO{sub 2} phase appear at the surface of the U{sub 3}O{sub 8} grains with a specific germination frequency. The growth reactivity is anisotropic and is very large in the tangential direction to the grains surface. Then, the uranium dioxide growths inside the grain and the limiting step is the grain surface. The variations of the growth reactivity and of the germination specific frequency in terms of the gases partial pressures and of the temperature have been explained by two different mechanisms. The limiting step of the growth mechanism is the desorption of water in the uranium dioxide surface. Concerning the germination mechanism the limiting step is a water desorption too but in the tri-uranium octo-oxide surface. The same geometrical modeling and the same germination and growth mechanisms have been applied to the reduction of a tri-uranium octo-oxide obtained by calcination of hydrated uranium trioxide. The values of the germination specific frequency of this solid are nevertheless weaker than those of the solid obtained by direct calcination of the uranium trioxide. (O.M.) 45 refs.

  19. Discussion of the Investigation Method on the Reaction Kinetics of Metallurgical Reaction Engineering

    Science.gov (United States)

    Du, Ruiling; Wu, Keng; Zhang, Jiazhi; Zhao, Yong

    Reaction kinetics of metallurgical physical chemistry which was successfully applied in metallurgy (as ferrous metallurgy, non-ferrous metallurgy) became an important theoretical foundation for subject system of traditional metallurgy. Not only the research methods were very perfect, but also the independent structures and systems of it had been formed. One of the important tasks of metallurgical reaction engineering was the simulation of metallurgical process. And then, the mechanism of reaction process and the conversion time points of different control links should be obtained accurately. Therefore, the research methods and results of reaction kinetics in metallurgical physical chemistry were not very suitable for metallurgical reaction engineering. In order to provide the definite conditions of transmission, reaction kinetics parameters and the conversion time points of different control links for solving the transmission and reaction equations in metallurgical reaction engineering, a new method for researching kinetics mechanisms in metallurgical reaction engineering was proposed, which was named stepwise attempt method. Then the comparison of results between the two methods and the further development of stepwise attempt method were discussed in this paper. As a new research method for reaction kinetics in metallurgical reaction engineering, stepwise attempt method could not only satisfy the development of metallurgical reaction engineering, but also provide necessary guarantees for establishing its independent subject system.

  20. The effect of preparation conditions and the ionizing radiation on the kinetics of cupric oxide reduction by hydrogen

    International Nuclear Information System (INIS)

    Pospisil, M.; Taras, P.

    1977-01-01

    Cupric oxide reduction in the temperature interval 170 to 350 degC was studied by thermogravimetry. The reduction kinetics can be quantitatively described by the modified Prout-Tompkinson equation, with the apparent activation energy varying within the limits (4.94 to 5.82)x10 4 J/mol. Irregularities observed during the reduction of the oxide of the oxalate origin are due to the high content of the metallic phase. The p-semiconducting nature of these oxides was proved for all samples. The effect of the pre-irradiation of samples with γ-rays (with an absorbed dose of (1.4 to 4.75)x10 6 J/kg) on the reduction kinetics depends on the origin of the cupric oxide. In contrast to NiO no correlation between the content of super-stoichiometric oxygen and the reduction kinetics was found. After irradiation with γ-rays or with fast neutrons at a dose of 79.8 J/kg the reduction rate increases and the activation energy decreases regardless of the oxide origin. At the same time the concentration of the ionic form of super-stoichiometric oxygen increases. (author)

  1. Molecular Dynamics Investigation of the Effects of Concentration on Hydrogen Bonding in Aqueous Solutions of Methanol, Ethylene Glycol and Glycerol

    International Nuclear Information System (INIS)

    Zhang, Ning; Li, Weizhong; Chen, Cong; Zuo, Jianguo; Weng, Lindong

    2013-01-01

    Hydrogen bonding interaction between alcohols and water molecules is an important characteristic in the aqueous solutions of alcohols. In this paper, a series of molecular dynamics simulations have been performed to investigate the aqueous solutions of low molecular weight alcohols (methanol, ethylene glycol and glycerol) at the concentrations covering a broad range from 1 to 90 mol %. The work focuses on studying the effect of the alcohols molecules on the hydrogen bonding of water molecules in binary mixtures. By analyzing the hydrogen bonding ability of the hydroxyl (-OH) groups for the three alcohols, it is found that the hydroxyl group of methanol prefers to form more hydrogen bonds than that of ethylene glycol and glycerol due to the intra-and intermolecular effects. It is also shown that concentration has significant effect on the ability of alcohol molecule to hydrogen bond water molecules. Understanding the hydrogen bonding characteristics of the aqueous solutions is helpful to reveal the cryoprotective mechanisms of methanol, ethylene glycol and glycerol in aqueous solutions

  2. Experimental and kinetic modeling investigation of rich premixed toluene flames doped with n-butanol.

    Science.gov (United States)

    Li, Yuyang; Yuan, Wenhao; Li, Tianyu; Li, Wei; Yang, Jiuzhong; Qi, Fei

    2018-04-25

    n-Butanol is a promising renewable biofuel and has a lot of advantages as a gasoline additive compared with ethanol. Though the combustion of pure n-butanol has been extensively investigated, the chemical structures of large hydrocarbons doped with n-butanol, especially for aromatic fuels, are still insufficiently understood. In this work, rich premixed toluene/n-butanol/oxygen/argon flames were investigated at 30 Torr with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The blending ratio of n-butanol was varied from 0 to 50%, while the equivalence ratio was maintained at a quite rich value (1.75) for the purpose of studying the influence of n-butanol on the aromatic growth process. Flame species including radicals, reactive molecules, isomers and polycyclic aromatic hydrocarbons (PAHs) were identified and their mole fraction profiles were measured. A kinetic model of toluene/n-butanol combustion was developed from our recently reported toluene and n-butanol models. It is observed that the production of most toluene decomposition products and larger aromatics was suppressed as the blending ratio of n-butanol increases. Meanwhile, the addition of n-butanol generally enhanced the formation of most observed C2-C4 hydrocarbons and C1-C4 oxygenated species. The rate of production (ROP) analysis and experimental observations both indicate that the interaction between toluene and n-butanol in their decomposition processes mainly occurs at the formation of small intermediates, e.g. acetylene and methyl. In particular, the interaction between toluene and n-butanol in methyl formation influences the formation of large monocyclic aromatics such as ethylbenzene, styrene and phenylacetylene, making their maximum mole fractions decay slowly upon increasing the blending ratio of n-butanol compared with toluene and benzyl. The increase of the blending ratio of n-butanol reduces the formation of key PAH precursors such as benzyl, fulvenallenyl

  3. Experimental, kinetic and numerical modeling of hydrogen production by catalytic reforming of crude ethanol over a commercial catalyst in packed bed tubular reactor and packed bed membrane reactor

    International Nuclear Information System (INIS)

    Aboudheir, Ahmed; Akande, Abayomi; Idem, Raphael

    2006-01-01

    reactor. The model was based on the coupling of mass, momentum and energy balance equations as well as our new kinetic model developed for this process.The simulation results for crude ethanol conversion were found to be in accordance with the experimental data obtained at various operating conditions. In addition, the predicted variations of the concentration and temperature profiles for our process. In the radial direction indicate that the assumption of plug flow and isothermal behaviour is justified within certain kinetics operating conditions. However, even within these operating conditions, our results have proven that the axial dispersion terms in the balance equations (mass, momentum and energy) cannot be neglected, especially in the hypothetical industrial case presented in this work for the reforming of crude ethanol. In addition, in the experimental study of the application of a porous membrane reactor for the crude ethanol reforming process conducted to compare with that for the packed bed tubular reactor, it was found that the membrane reactor outperformed the packed bed tubular reactor in terms of crude ethanol conversion and hydrogen production. This is due to the function of the membrane reactor to shift the thermodynamic equilibrium in favour of the conversion of crude ethanol to hydrogen according to Le Catelier-Braun's law.(Author)

  4. Kinetic evidence for the formation of discrete 1,4-dehydrobenzene intermediates. Trapping by inter- and intramolecular hydrogen atom transfer and observation of high-temperature CIDNP

    Energy Technology Data Exchange (ETDEWEB)

    Lockhart, Thomas P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Comita, Paul B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Bergman, Robert G. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States)

    1981-07-01

    Upon heating, alkyl-substituted cis-1,2-diethynyl olefins undergo cyclization to yield reactive 1,4-dehydrobenzenes; the products isolated may be derived from either unimolecular or bimolecular reactions of the intermediate. (Z)-4,5-Diethynyl-4-octene (4) undergoes rearrangement to yield 2,3-di-n-propyl-1,4-dehydrobenzene (17). Solution pyrolysis of 4 in inert aromatic solvents produces three unimolecular products, (Z)-dodeca-4,8-diyn-6-ene (7), benzocyclooctene (9), and o-allyl-n-propylbenzene (10), in high yield. When 1,4-cyclohexadiene is added to the pyrolysis solution as a trapping agent, high yields of the reduced product o-di-n-propylbenzene (12) are obtained. The kinetics of solution pyrolysis of 4 in the presence and absence of trapping agent establish that 2,3-di-n-propyl-1,4-dehydrobenzene is a discrete intermediate on the pathway leading to products. When the reaction was run in the heated probe of an NMR spectrometer, CIDNP was observed in 10. This observation, along with kinetic and chemical trapping evidence, indicates the presence of two additional intermediates, formed from 17 by sequential intramolecular [1,5] hydrogen transfer, on the pathway to products. The observation of CIDNP, coupled with the reactivity exhibited by 17 and the other two intermediates, implicate a biradical description of these molecules. Biradical 17 has been estimated to have a lifetime of about 10-9 s at 200°C and to lie in a well of about 5 kcal/mol with respect to the lowest energy unimolecular pathway ([1,5] hydrogen transfer). Ring opening (expected to be the lowest energy process for 1,4-dehydrobenzenes in which intramolecular hydrogen transfer is unlikely) to the isomeric diethynyl olefin 7 appears to have an activation enthalpy of about 10 kcal/moL Upon thermal reaction in the gas phase (400°C) or in solution in inert solvents (Z)-hexa-2,3-diethyl-1,5-diyn-3-ene (5) rearranges in good yield to the isomeric diethynyl olefin (Z)-deca-3,7-diyn-5-ene (8

  5. Selective heterogeneous catalytic hydrogenation of ketone (C═O) to alcohol (OH) by magnetite nanoparticles following Langmuir-Hinshelwood kinetic approach.

    Science.gov (United States)

    Shah, Muhammad Tariq; Balouch, Aamna; Rajar, Kausar; Sirajuddin; Brohi, Imdad Ali; Umar, Akrajas Ali

    2015-04-01

    Magnetite nanoparticles were successfully synthesized and effectively employed as heterogeneous catalyst for hydrogenation of ketone moiety to alcohol moiety by NaBH4 under the microwave radiation process. The improvement was achieved in percent recovery of isopropyl alcohol by varying and optimizing reaction time, power of microwave radiations and amount of catalyst. The catalytic study revealed that acetone would be converted into isopropyl alcohol (IPA) with 99.5% yield in short period of reaction time, using 10 μg of magnetite NPs (Fe3O4). It was observed that the catalytic hydrogenation reaction, followed second-order of reaction and the Langmuir-Hinshelwood kinetic mechanism, which elucidated that both reactants get adsorb onto the surface of silica coated magnetite nanocatalyst to react. Consequently, the rate-determining step was the surface reaction of acetone and sodium borohydride. The current study revealed an environment friendly conversion of acetone to IPA on the basis of its fast, efficient, and highly economical method of utilization of microwave irradiation process and easy catalyst recovery.

  6. Efficient Synthesis of Differentiated syn-1,2-Diol Derivatives by Asymmetric Transfer Hydrogenation-Dynamic Kinetic Resolution of α-Alkoxy-Substituted β-Ketoesters.

    Science.gov (United States)

    Monnereau, Laure; Cartigny, Damien; Scalone, Michelangelo; Ayad, Tahar; Ratovelomanana-Vidal, Virginie

    2015-08-10

    Asymmetric transfer hydrogenation was applied to a wide range of racemic aryl α-alkoxy-β-ketoesters in the presence of well-defined, commercially available, chiral catalyst Ru(II) -(N-p-toluenesulfonyl-1,2-diphenylethylenediamine) and a 5:2 mixture of formic acid and triethylamine as the hydrogen source. Under these conditions, dynamic kinetic resolution was efficiently promoted to provide the corresponding syn α-alkoxy-β-hydroxyesters derived from substituted aromatic and heteroaromatic aldehydes with a high level of diastereoselectivity (diastereomeric ratio (d.r.)>99:1) and an almost perfect enantioselectivity (enantiomeric excess (ee)>99 %). Additionally, after extensive screening of the reaction conditions, the use of Ru(II) - and Rh(III) -tethered precatalysts extended this process to more-challenging substrates that bore alkenyl-, alkynyl-, and alkyl substituents to provide the corresponding syn α-alkoxy-β-hydroxyesters with excellent enantiocontrol (up to 99 % ee) and good to perfect diastereocontrol (d.r.>99:1). Lastly, the synthetic utility of the present protocol was demonstrated by application to the asymmetric synthesis of chiral ester ethyl (2S)-2-ethoxy-3-(4-hydroxyphenyl)-propanoate, which is an important pharmacophore in a number of peroxisome proliferator-activated receptor α/γ dual agonist advanced drug candidates used for the treatment of type-II diabetes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Investigating Hydrogen Bonding in Phenol Using Infrared Spectroscopy and Computational Chemistry

    Science.gov (United States)

    Fedor, Anna M.; Toda, Megan J.

    2014-01-01

    The hydrogen bonding of phenol can be used as an introductory model for biological systems because of its structural similarities to tyrosine, a para-substituted phenol that is an amino acid essential to the synthesis of proteins. Phenol is able to form hydrogen bonds readily in solution, which makes it a suitable model for biological…

  8. Investigation of ammonium nitrate effect on kinetics and mechanism of thermal decomposition of ammonium polyuranates

    International Nuclear Information System (INIS)

    Karelin, A.I.; Lobas, O.P.; Zhiganov, A.N.; Vasil'ev, K.F.; Zhiganova, A.A.

    1987-01-01

    A study was made on ammonium nitrate effect on the mechanism and kinetics of dehydration and thermal decomposition of ammonium polyuranates. Sufficient effect of nitrate ion content in ammonium polyuranate samples on their thermal stability was noted. Kinetic parameters of thermal decomposition of ammonium polyuranates were evaluated. Mechanism of dehydration and thermal decomposition of ammonium polyuranates in the presence of ammonium nitrate was suggested. It was shown that increase of ammonium nitrate content in ammonium polyuranate precipitate resulted to reduction of the specific surface of prepared uranium mixed oxide

  9. Investigation on the production of hydrogen rich gas in a plasma converter for motorcycle applications

    International Nuclear Information System (INIS)

    Horng, R.-F.; Chang, Y.-P.; Wu, S.-C.

    2006-01-01

    A plasma fuel converter producing a hydrogen rich gas fuel has been designed and constructed. The methodology included using a high voltage electric arc generator to ionize the mixture of methane fuel and air, which was then reformed into a hydrogen rich gas. It transpired from the experiment that the higher the arc frequency, the higher was the generated hydrogen concentration, with a maximum concentration of 43 vol.% attained with an arc frequency of 200 Hz and an O/C (O 2 /CH 4 ) ratio of 0.10. The maximum hydrogen yield of 0.55 was obtained with an arc frequency of 200 Hz and an O/C ratio between 0.20 and 0.25. By fueling a four stroke motorcycle engine with the hydrogen rich gas, low emissions during the cold start idle condition can be obtained

  10. Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

    Energy Technology Data Exchange (ETDEWEB)

    Rosenberg, M. J., E-mail: mrosenbe@mit.edu; Zylstra, A. B.; Séguin, F. H.; Rinderknecht, H. G.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Waugh, C. J.; Sinenian, N.; Li, C. K.; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); McKenty, P. W.; Hohenberger, M.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu.; Betti, R.; Goncharov, V. N.; Knauer, J. P.; Sangster, T. C. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); and others

    2014-12-15

    Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D{sub 2} and D{sup 3}He gas-filled “exploding-pusher” inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to the predictions of 2D DRACO hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.

  11. An investigation of the general regularity of size dependence of reaction kinetics of nanoparticles

    International Nuclear Information System (INIS)

    Cui, Zixiang; Duan, Huijuan; Xue, Yongqiang; Li, Ping

    2015-01-01

    In the processes of preparation and application of nanomaterials, the chemical reactions of nanoparticles are often involved, and the size of nanoparticles has dramatic influence on the reaction kinetics. Nevertheless, there are many conflicts on regularities of size dependence of reaction kinetic parameters, and these conflicts have not been explained so far. In this paper, taking the reaction of nano-ZnO (average diameter is from 20.96 to 53.31 nm) with acrylic acid solution as a system, the influence regularities of the particle size on the kinetic parameters were researched. The regularities were consistent with that in most literatures, but inconsistent with that in a few of literatures, the reasons for the conflicts were interpreted. The reasons can be attributed to two factors: one is improper data processing for fewer data points, and the other is the difference between solid particles and porous particles. A general regularity of the size dependence of reaction kinetics for solid particles was obtained. The regularity shows that with the size of nanoparticles decreasing, the rate constant and the reaction order increase, while the apparent activation energy and the pre-exponential factor decrease; and the relationships of the logarithm of rate constant, the logarithm of pre-exponential factor, and the apparent activation energy to the reciprocal of the particle size are linear, respectively

  12. Investigation of Chemical Kinetics on Soot Formation Event of n-Heptane Spray Combustion

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song

    2014-01-01

    . Numerical computation is performed using OpenFOAM and chemistry coordinate mapping (CCM) approach is used to expedite the calculation. Three n-heptane kinetic mechanisms with different chemistry sizes and comprehensiveness in oxidation pathways and soot precursor formation are adopted. The three examined...

  13. Investigation of Coal-biomass Catalytic Gasification using Experiments, Reaction Kinetics and Computational Fluid Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Battaglia, Francine [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Agblevor, Foster [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Klein, Michael [Univ. of Delaware, Newark, DE (United States); Sheikhi, Reza [Northeastern Univ., Boston, MA (United States)

    2015-12-31

    A collaborative effort involving experiments, kinetic modeling, and computational fluid dynamics (CFD) was used to understand co-gasification of coal-biomass mixtures. The overall goal of the work was to determine the key reactive properties for coal-biomass mixed fuels. Sub-bituminous coal was mixed with biomass feedstocks to determine the fluidization and gasification characteristics of hybrid poplar wood, switchgrass and corn stover. It was found that corn stover and poplar wood were the best feedstocks to use with coal. The novel approach of this project was the use of a red mud catalyst to improve gasification and lower gasification temperatures. An important results was the reduction of agglomeration of the biomass using the catalyst. An outcome of this work was the characterization of the chemical kinetics and reaction mechanisms of the co-gasification fuels, and the development of a set of models that can be integrated into other modeling environments. The multiphase flow code, MFIX, was used to simulate and predict the hydrodynamics and co-gasification, and results were validated with the experiments. The reaction kinetics modeling was used to develop a smaller set of reactions for tractable CFD calculations that represented the experiments. Finally, an efficient tool was developed, MCHARS, and coupled with MFIX to efficiently simulate the complex reaction kinetics.

  14. Esterification of Oleic Acid for Biodiesel Production Catalyzed by SnCl2: A Kinetic Investigation

    Directory of Open Access Journals (Sweden)

    Marcio J. da Silva

    2008-09-01

    Full Text Available The production of biodiesel from low-cost raw materials which generally contain high amounts of free fatty acids (FFAs is a valuable alternative that would make their production costs more competitive than petroleum-derived fuel. Currently, the production of biodiesel from this kind of raw materials comprises a two-stage process, which requires an initial acid-catalyzed esterification of the FFA, followed by a basecatalyzed transesterification of the triglycerides. Commonly, the acid H2SO4 is the catalyst on the first step of this process. It must be said, however, that major drawbacks such as substantial reactor corrosion and the great generation of wastes, including the salts formed due to neutralization of the mineral acid, are negative and virtually unsurmountable aspects of this protocol. In this paper, tin(II chloride dihydrate (SnCl2·2H2O, an inexpensive Lewis acid, was evaluated as catalyst on the ethanolysis of oleic acid, which is the major component of several fat and vegetable oils feedstocks. Tin chloride efficiently promoted the conversion of oleic acid into ethyl oleate in ethanol solution and in soybean oil samples, under mild reaction conditions. The SnCl2 catalyst was shown to be as active as the mineral acid H2SO4. Its use has relevant advantages in comparison to mineral acids catalysts, such as less corrosion of the reactors and as well as avoiding the unnecessary neutralization of products. Herein, the effect of the principal parameters of reaction on the yield and rate of ethyl oleate production has been investigated. Kinetic measurements revealed that the esterification of oleic acid catalyzed by SnCl2·2H2O is first-order in relation to both FFAs and catalyst concentration. Experimentally, it was verified that the energy of activation of the esterification reaction of oleic acid catalyzed by SnCl2 was very close those reported for H2SO4.

  15. Lithium hydride hydrolysis: experimental and kinetic study

    International Nuclear Information System (INIS)

    Charton, S.; Maupoix, C.; Brevet, A.; Delaunay, F.; Heintz, O.; Saviot, L.

    2006-01-01

    In this work has been studied the contribution of various analyses techniques in the framework, on the one hand of revealing the mechanisms implied in lithium hydride hydrolysis, and on the other hand of studying the kinetics of hydrogen production. Among the methods recently investigated, Raman spectroscopy, XPS and SIMS seem to be particularly attractive. (O.M.)

  16. Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET

    NARCIS (Netherlands)

    Lerche, E.; Van Eester, D.; Johnson, T. J.; Hellsten, T.; Ongena, J.; Mayoral, M. L.; Frigione, D.; Sozzi, C.; Calabro, G.; Lennholm, M.; Beaumont, P.; Blackman, T.; Brennan, D.; Brett, A.; Cecconello, M.; Coffey, I.; Coyne, A.; Crombe, K.; Czarnecka, A.; Felton, R.; Giroud, C.; Gorini, G.; Hellesen, C.; Jacquet, P.; Kiptily, V.; Knipe, S.; Krasilnikov, A.; Maslov, M.; Monakhov, I.; Noble, C.; Nocente, M.; Pangioni, L.; Proverbio, I.; Sergienko, G.; Stamp, M.; Studholme, W.; Tardocchi, M.; Vdovin, V.; Versloot, T.; Voitsekhovitch, I.; Whitehurst, A.; Wooldridge, E.; Zoita, V.; JET-EFDA Contributors,

    2012-01-01

    Two ion cyclotron range of frequencies (ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas—fundamental H majority and second harmonic 3 He ICRF heating—were recently investigated in JET. Although the same magnetic field and RF frequencies ( f ≈ 42 MHz and f

  17. Investigating attitudes to hydrogen refuelling facilities and the social cost to local residents

    International Nuclear Information System (INIS)

    O'Garra, Tanya; Mourato, Susana; Pearson, Peter

    2008-01-01

    Vehicles fuelled by hydrogen (H 2 ) have attracted increasing attention because of their potentially enhanced environmental profiles. Their penetration into the vehicle stock will be influenced by the spread of refuelling facilities. This study investigates local attitudes towards the proposed installation of H 2 storage facilities at existing refuelling stations throughout London. Using multinomial logit analysis, we identify the determinants of attitudes. Results suggest that residents living very close to a proposed H 2 facility are less likely to be opposed than residents living 200-500 m away. Opposition appears to be determined by a lack of trust in safety regulations, non-environmental attitudes, and concerns about the existing local refuelling station. The social cost to local residents of a local H 2 storage facility was estimated using a method developed by Atkinson et al. [2004. 'Amenity' or 'eyesore'? Negative willingness to pay for options to replace electricity transmission towers. Applied Economics Letters 11(4), 203-208], which elicits the amount of time respondents are willing to commit to oppose a new facility development. Using the leisure rate of time, the social cost is estimated at just under Pounds 14 per local opposed resident. Add to this the WTP to support opposition efforts by a local group, and the value comes to just under Pounds 25 per opposed resident

  18. Quasiclassical trajectory study of the molecular beam kinetics of the deuterium atom--hydrogen halide exchange reactions

    International Nuclear Information System (INIS)

    Raff, L.M.; Suzukawa, H.H. Jr.; Thompson, D.L.

    1975-01-01

    Unadjusted quasiclassical trajectory computations have been carried out to simulate the molecular beam scattering of thermal D atom beams at 2800 degreeK crossed with beams of HCl and HI at 250 degreeK. Total reaction cross sections, energy partitioning distributions, and differential scattering cross sections have been computed for the exchange reactions D+HCl → DCl+H and D+HI → DI+H while total reaction cross sections are reported for the corresponding abstractions, i.e., D+HCl → HD+Cl and D+HI → HD+I. For the exchange reactions, the computed reaction cross sections are within the range estimated from the crossed beam experiments. The calculated average energy partitioned into relative translational motion of products is in near quantitative agreement with the beam results, and the predicted differential scattering cross sections appear to be in qualitative accord with the beam experiments. The over-all agreement between theory and experiment indicates that previously computed values for the thermal rate coefficients for the exchange reactions are of the right order and that a systematic error exists in the interpretation of photolysis data in the hydrogen--hydrogen halide systems

  19. Kinetic hydrogen isotope effects in the concerted mechanism for the hydrolysis of acetals, ketals, and ortho esters

    International Nuclear Information System (INIS)

    Eliason, R.; Kreevoy, M.M.

    1978-01-01

    The hydrolysis of many ortho esters, and some acetals and ketals, is general acid catalyzed, and in some examples these generate linear Bronsted plots over substantial ranges of catalyst acidity. This suggests that the reaction coordinate is primarily a reorganization of heavy atoms since proton transfer from one oxygen to another has been shown to generate strongly curved Bronsted plots. However, the isotopic fractionation factor for the catalytically active proton in these transition states is substantially less than 1.0; in several examples it is less than 0.5. Such values have been thought to require that the reaction coordinate be largely a motion of the hydrogen giving the low fractionation factor. This dilemma has been resolved by the observation and rationalization of fractionation factors as low as 0.28 for stable, hydrogen bridge-bonded complexes, AHA - . A similar, bounded coordinate is now suggested for the catalytically active protons in question. This permits the reaction coordinate to be pictured. 3 figures, 2 tables

  20. Investigation of the kinetics and mechanism of the glycerol chlorination reaction using gas chromatography–mass spectrometry

    Directory of Open Access Journals (Sweden)

    JUN WANG

    2010-01-01

    Full Text Available As a primary by-product in biodiesel production, glycerol can be used to prepare an important fine chemical, epichlorohydrin, by the glycerol chlorination reaction. Although this process has been applied in industrial production, unfortunately, less attention has been paid to the analysis and separation of the compounds in the glycerol chlorination products. In this study, a convenient and accurate method to determine the products in glycerol chlorination reaction was established and based on the results the kinetic mechanism of the reaction was investigated. The structure of main products, including 1,3--dichloropropan-2-ol, 2,3-dichloropropan-1-ol, 3-chloro-1,2-propanediol, 2-chloro-1,3-propanediol and glycerol was ascertained by gas chromatography–mass spectrometry and the isomers of the products were distinguished. Apidic acid was considered as the best catalyst because of its excellent catalytic effect and high boiling point. The mechanism of the glycerol chlorination reaction was proposed and a new kinetic model was developed. Kinetic equations of the process in the experimental range were obtained by data fitting and the activation energies of each tandem reaction were 30.7, 41.8, 29.4 and 49.5 kJ mol-1, respectively. This study revealed the process and mechanism of the kinetics and provides the theoretical basis for engineering problems.

  1. Electrochemical kinetic performances of electroplating Co–Ni on La–Mg–Ni-based hydrogen storage alloys

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuan; Tao, Yang; Ke, Dandan; Ma, Yufei [Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Han, Shumin, E-mail: hanshm@ysu.edu.cn [Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-12-01

    Graphical abstract: - Highlights: • The Co–Ni composite coating was prepared by electroplating. • The alloy treated at 10 mA/cm{sup 2} has superior kinetic performances. • The Co–Ni layer accelerates the charge transfer rate on the surface of the alloy. - Abstract: Electroplating Co–Ni treatment was applied to the surface of the La{sub 0.75}Mg{sub 0.25}Ni{sub 3.48} alloy electrodes in order to improve the electrochemical and kinetic performances. The Scanning electron microscope-Energy dispersive spectroscopy and X-ray diffraction results showed that the electrodes were plated with a homogeneous Co–Ni alloy film. The alloy coating significantly improved the high rate dischargeability of the alloy electrode, and the HRD value increased to 57.5% at discharge current density 1875 mA/g after the Co–Ni-coating. The exchange current density I{sub 0}, the limiting current density I{sub L} and the oxidation peak current also increased for the coated alloy. The improvement of overall electrode performances was attributed to an enhancement in electro-catalytic activity and conductivity at the alloy surface, owing to the precipitation of the Co–Ni layer.

  2. Liquid-phase chemical hydrogen storage: catalytic hydrogen generation under ambient conditions.

    Science.gov (United States)

    Jiang, Hai-Long; Singh, Sanjay Kumar; Yan, Jun-Min; Zhang, Xin-Bo; Xu, Qiang

    2010-05-25

    There is a demand for a sufficient and sustainable energy supply. Hence, the search for applicable hydrogen storage materials is extremely important owing to the diversified merits of hydrogen energy. Lithium and sodium borohydride, ammonia borane, hydrazine, and formic acid have been extensively investigated as promising hydrogen storage materials based on their relatively high hydrogen content. Significant advances, such as hydrogen generation temperatures and reaction kinetics, have been made in the catalytic hydrolysis of aqueous lithium and sodium borohydride and ammonia borane as well as in the catalytic decomposition of hydrous hydrazine and formic acid. In this Minireview we briefly survey the research progresses in catalytic hydrogen generation from these liquid-phase chemical hydrogen storage materials.

  3. Mechanisms of wet oxidation by hydrogen peroxide

    International Nuclear Information System (INIS)

    Baxter, R.A.

    1987-08-01

    A research programme is currently under way at BNL and MEL to investigate the possible use of Hydrogen Peroxide with metal ion catalysts as a wet oxidation treatment system for CEGB organic radioactive wastes. The published literature relating to the kinetics and mechanism of oxidation and decomposition reactions of hydrogen peroxide is reviewed and the links with practical waste management by wet oxidation are examined. Alternative wet oxidation systems are described and the similarities to the CEGB research effort are noted. (author)

  4. A combinatorial characterization scheme for high-throughput investigations of hydrogen storage materials

    International Nuclear Information System (INIS)

    Hattrick-Simpers, Jason R; Chiu, Chun; Bendersky, Leonid A; Tan Zhuopeng; Oguchi, Hiroyuki; Heilweil, Edwin J; Maslar, James E

    2011-01-01

    In order to increase measurement throughput, a characterization scheme has been developed that accurately measures the hydrogen storage properties of materials in quantities ranging from 10 ng to 1 g. Initial identification of promising materials is realized by rapidly screening thin-film composition spread and thickness wedge samples using normalized IR emissivity imaging. The hydrogen storage properties of promising samples are confirmed through measurements on single-composition films with high-sensitivity (resolution <0.3 μg) Sievert's-type apparatus. For selected samples, larger quantities of up to ∼100 mg may be prepared and their (de)hydrogenation and micro-structural properties probed via parallel in situ Raman spectroscopy. Final confirmation of the hydrogen storage properties is obtained on ∼1 g powder samples using a combined Raman spectroscopy/Sievert's apparatus.

  5. Investigation of hydrogen-burn damage in the Three Mile Island Unit 2 reactor building

    International Nuclear Information System (INIS)

    Alvares, N.J.; Beason, D.G.; Eidem, G.R.

    1982-06-01

    About 10 hours after the March 28, 1979 Loss-of-Coolant Accident began at Three Mile Island Unit 2, a hydrogen deflagration of undetermined extent occurred inside the reactor building. Examinations of photographic evidence, available from the first fifteen entries into the reactor building, yielded preliminary data on the possible extent and range of hydrogen burn damage. These data, although sparse, contributed to development of a possible damage path and to an estimate of the extent of damage to susceptible reactor building items. Further information gathered from analysis of additional photographs and samples can provide the means for estimating hydrogen source and production rate data crucial to developing a complete understanding of the TMI-2 hydrogen deflagration. 34 figures

  6. Investigation of solid-phase hydrogenation of amino acids and peptides

    International Nuclear Information System (INIS)

    Zolotarev, Yu.A.; Myasoedov, N.F.; Zajtsev, D.A.; Lubnin, M.Yu.; Tatur, V.Yu.; Kozik, V.S.; Dorokhova, E.M.; Rozenberg, S.N.

    1990-01-01

    The possibility of synthesizing amino acids and peptides multiply labelled with tritium or deuterium by the method of solid-phase isotopic exchange with gaseous hydrogen isotopes was verified. Establishment of the isotopic hydrogen equilibrium between the gaseous phase and the solid phase formed by the amino acid molecules was found experimentally. The activation energy of the isotopic exchange is 13 kcal/mol. A mathematical model was set up for the isotopic exchange with a probable substitution of hydrogen atoms. Uniformly labelled amino acids were obtained in a high optical purity and with 80 to 90% hydrogen substitution by deuterium and tritium. Tritiated peptides were prepared in high yields at molar activities of 1.5 to 3.7 TBq/mmol. (author). 4 tabs

  7. Investigation of tritium removal by means of organic compounds. Catalytic hydrogenation (tritiation) of linoleic acid

    International Nuclear Information System (INIS)

    El-Sharnouby, A.; Weichselgartner, H.

    1984-11-01

    In the presence of noble-metal catalysts unsaturated fatty acids such as eruic acid and linoleic acid capture hydrogen (and tritium) quantitatively. The hydrogenation reaction of eruic acid has already been reported. The experimental results of the reaction of hydrogen (and tritium) with linoleic acid are now discussed in this paper. Obviously, the use of linoleic acid shows some advantages compared with eruic acid: - the hydrogenation reaction is faster, - linoleic acid is liquid, so that the choice of additional solvents is easier, and - linoleic acid is a more or less cheap natural product, which is available from a series of seeds, so that the cost of a technical tritium removal plant is not increased by the basic chemical material. (orig.)

  8. An investigation of hydrogen storage methods for fuel cell operation with man-portable equipment

    Energy Technology Data Exchange (ETDEWEB)

    Browning, D [Defence Evaluation and Research Agency, Haslar (United Kingdom); Jones, P [Defence Evaluation and Research Agency, Haslar (United Kingdom); Packer, K [Defence Evaluation and Research Agency, Haslar (United Kingdom)

    1997-03-01

    Air breathing proton exchange membrane fuel cells (PEMFC) are being considered as a power source for man-portable equipment, such as army radios. In addition to the weight and volume of the fuel cell itself, the device producing hydrogen with which to fuel the cell is also of crucial importance. This paper describes a number of hydrogen storage methods and discusses their applicability to man-portable equipment. (orig.)

  9. Investigation on the lean combustion performance of a hydrogen-enriched n-butanol engine

    International Nuclear Information System (INIS)

    Zhang, Bo; Ji, Changwei; Wang, Shuofeng

    2017-01-01

    Highlights: • H_2 addition avails improving thermal efficiency of n-butanol engines. • Lean burn limit of n-butanol engine is extended by H_2 addition. • H_2 addition shortens the n-butanol engine combustion duration. • HC and CO from the n-butanol engine are decreased by H_2 addition. - Abstract: n-Butanol is a feasible fuel candidate for spark-ignition engines. The current paper carried out an experiment to explore effects of hydrogen addition on further improving the performance of a n-butanol engine under the part load and lean conditions. Within the test, the engine intake pressure and speed were respectively kept at 61.5 kPa and 1400 rpm. The volumetric fractions of hydrogen in the total intake gas (hydrogen + air) were constrained at 0 and 3%, respectively. Under a certain hydrogen blending level, the global excess air ratio of in-cylinder charge which was changed from the stoichiometric to near the lean burn limit was adjusted by varying the n-butanol injection duration. The experimental results confirmed that the brake thermal efficiency was heightened and the lean burn limit was extended after the hydrogen addition. Besides, compared with the pure n-butanol combustion, the hydrogen enrichment enables the engine to gain dropped ignition delay and rapid combustion duration. Moreover, CO and HC from the pure n-butanol engine were reduced by the hydrogen addition. NOx were generally reduced when the excess air ratio was raised. This suggested that NOx from the hydrogen-enriched butanol engine could also be controlled by lean combustion.

  10. In-situ investigation of the hydrogen release mechanism in bulk Mg2NiH4

    Science.gov (United States)

    Tran, Xuan Quy; McDonald, Stuart D.; Gu, Qinfen; Yamamoto, Tomokazu; Shigematsu, Koji; Aso, Kohei; Tanaka, Eishi; Matsumura, Syo; Nogita, Kazuhiro

    2017-02-01

    Hydrogen storage is an important aspect to enable the so-called hydrogen economy. Mg-Ni alloys are among the most promising candidates for solid-state hydrogen storage systems yet many questions remain unanswered regarding the hydriding/dehydriding mechanism of the alloys. Mg2NiH4 particularly has received much attention both for its potential as a hydrogen storage medium and also exhibits interesting properties relating to its different polymorphs. Here, the dehydriding mechanism in bulk Mg2NiH4 is investigated using in-situ ultra-high voltage transmission electron microscopy (TEM) combined with Synchrotron powder X-ray diffraction (XRPD) and differential scanning calorimetry (DSC). We find that the hydrogen release is based on a mechanism of nucleation and growth of Mg2NiHx (x∼0-0.3) solid solution grains and is greatly enhanced in the presence of crystal defects occurring as a result of the polymorphic phase transformation. Also importantly, with atomic resolution TEM imaging a high density of stacking faults is identified in the dehydrided Mg2NiHx (x∼0-0.3) lattices.

  11. Electrochemical investigations of activation and degradation of hydrogen storage alloy electrodes in sealed Ni/MH battery

    Energy Technology Data Exchange (ETDEWEB)

    Chen, W.X.; Xu, Z.D. [Zhejiang University, Hangzhou (China). Dept. of Chemistry; Tu, J.P. [Zhejiang University, Hangzhou (China). Dept. of Materials Science and Engineering

    2002-04-01

    The M1Ni{sub 0.4}Co{sub 0.6}Al{sub 0.4} alloy was treated with hot alkaline solution containing a small amount of KBH{sub 4} and its effect on the activation and degradation behaviors of the hydrogen storage alloy electrodes in sealed Ni/MH batteries was investigated. It was found that the treated alloy electrode exhibited a better activation property than the untreated one in the sealed battery as well as in open cell. For the treated alloy electrode activating, the polarization resistance in the sealed battery was almost equal to that in the open cell. But in the case of the untreated alloy electrode activating, the polarization resistance in the sealed battery was larger than that in the open cell. The reason is that the oxide film on the untreated alloy surface suppressed the combination of the oxygen evolved on the positive electrode with hydrogen on the negative alloy surface. In addition, the decaying of capacity of the untreated alloy electrode was much faster than that of the treated one. The reasons were, that after surface treatment, the Ni-rich and Al-poor layer on the alloy surface not only had a high electrocatalytic activity for hydrogen electrode reaction, but also facilitated the combination of the oxygen with hydrogen and hydrogen adsorption on the alloy surface. (author)

  12. Experimental methods of investigation of kinetics and dynamics of nuclear reactors

    International Nuclear Information System (INIS)

    Costa Oliveira, Jaime M.

    1969-03-01

    The author presents experimental methods used to study kinetic and dynamic properties of nuclear reactors. Kinetic methods aim at determining characteristic parameters of the behaviour in time of neutrons. Dynamic methods aim at establishing the relationships between the reactor behaviour and its internal and external causes (notably the measurement of transfer functions). The author proposes a classification with respect to the excitation type: periodic excitation (reactivity sinusoidal modulation, source sinusoidal modulation, periodic pulse excitation), non periodic excitation (reactivity monitoring, reactivity linear variation, reactivity variation according to any given law, removal of starting source), random excitation (random reactivity or source excitation), natural fluctuations (alpha-Rossi method, methods of reduced variance, probabilistic methods, correlation methods, spectral analysis method). He also addresses space and energy effects. Applications are reported for low power and power reactors

  13. Thermo analytic investigation of hydrogen effusion behavior - sensor evaluation and calibration

    Energy Technology Data Exchange (ETDEWEB)

    Ried, P.; Gaber, M.; Beyer, K.; Mueller, R.; Kipphardt, H.; Kannengiesser, T. [BAM, Federal Institute for Material Research and Testing, Berlin (Germany)

    2011-01-15

    The well established carrier gas analysis (CGA) method was used to test different hydrogen detectors comprising a thermal conductivity detector (TCD) and a metal oxide semiconducting (MOx) sensor. The MOx sensor provides high hydrogen sensitivity and selectivity, whereas the TCD exhibits a much shorter response time and a linear hydrogen concentration dependency. Therefore, the TCD was used for quantitative hydrogen concentration measurements above 50 {mu}mol/mol. The respective calibration was made using N{sub 2}/H{sub 2} gas mixtures. Furthermore, the hydrogen content and degassing behaviour of titanium hydride (TiH{sub 2-x}) was studied. This material turned out to be a potential candidate for a solid sample calibration. Vacuum hot extraction (VHE) coupled with a mass spectrometer (MS) was then calibrated with TiH{sub 2-x} as transfer standard. The calibration was applied for the evaluation of the hydrogen content of austenitic steel samples (1.4301) and the comparison of CGA-TCD and VHE-MS. (Copyright copyright 2011 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Investigation of kinetics and absorption isotherm models for hydroponic phytoremediation of waters contaminated with sulfate.

    Science.gov (United States)

    Saber, Ali; Tafazzoli, Milad; Mortazavian, Soroosh; James, David E

    2018-02-01

    Two common wetland plants, Pampas Grass (Cortaderia selloana) and Lucky Bamboo (Dracaena sanderiana), were used in hydroponic cultivation systems for the treatment of simulated high-sulfate wastewaters. Plants in initial experiments at pH 7.0 removed sulfate more efficiently compared to the same experimental conditions at pH 6.0. Results at sulfate concentrations of 50, 200, 300, 600, 900, 1200, 1500 and 3000 mg/L during three consecutive 7-day treatment periods with 1-day rest intervals, showed decreasing trends of both removal efficiencies and uptake rates with increasing sulfate concentrations from the first to the second to the third 7-day treatment periods. Removed sulfate masses per unit dry plant mass, calculated after 23 days, showed highest removal capacity at 600 mg/L sulfate for both plants. A Langmuir-type isotherm best described sulfate uptake capacity of both plants. Kinetic studies showed that compared to pseudo first-order kinetics, pseudo-second order kinetic models slightly better described sulfate uptake rates by both plants. The Elovich kinetic model showed faster rates of attaining equilibrium at low sulfate concentrations for both plants. The dimensionless Elovich model showed that about 80% of sulfate uptake occurred during the first four days' contact time. Application of three 4-day contact times with 2-day rest intervals at high sulfate concentrations resulted in slightly higher uptakes compared to three 7-day contact times with 1-day rest intervals, indicating that pilot-plant scale treatment systems could be sized with shorter contact times and longer rest-intervals. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Kinetic and Modeling Investigation to Provide Design Guidelines for the NREL Dilute-Acid Process Aimed at Total Hydrolysis/Fractionation of Lignocellulosic Biomass: July 1998

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y. Y.; Iyer, P.; Xiang, Q.; Hayes, J.

    2004-08-01

    Following up on previous work, subcontractor investigated three aspects of using NREL ''pretreatment'' technology for total hydrolysis (cellulose as well as hemicellulose) of biomass. Whereas historic hydrolysis of biomass used either dilute acid or concentrated acid technology for hydrolysis of both hemicellulose and cellulose, NREL has been pursuing very dilute acid hydrolysis of hemicellulose followed by enzymatic hydrolysis of cellulose. NREL's countercurrent shrinking-bed reactor design for hemicellulose hydrolysis (pretreatment) has, however, shown promise for total hydrolysis. For the first task, subcontractor developed a mathematical model of the countercurrent shrinking bed reactor operation and, using yellow poplar sawdust as a feedstock, analyzed the effect of: initial solid feeding rate, temperature, acid concentration, acid flow rate, Peclet number (a measure of backmixing in liquid flow), and bed shrinking. For the second task, subcontractor used laboratory trials, with yellow poplar sawdust and 0.07 wt% sulfuric acid at various temperatures, to verify the hydrolysis of cellulose to glucose (desired) and decomposition of glucose (undesired) and determine appropriate parameters for use in kinetic models. Unlike cellulose and hemicellulose, lignins, the third major component of biomass, are not carbohydrates that can be broken down into component sugars. They are, however, aromatic complex amorphous phenolic polymers that can likely be converted into low-molecular weight compounds suitable for production of fuels and chemicals. Oxidative degradation is one pathway for such conversion and hydrogen peroxide would be an attractive reagent for this, as it would leave no residuals. For the third task, subcontractor reacted lignin with hydrogen peroxide under various conditions and analyzed the resulting product mix.

  16. Experimental investigations and modeling of devolatilization based on superimposed kinetics of biomass

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Anker Degn

    A non-isothermal one-dimensional model has been developed to describe biomass pyrolysis at fast heating rate (600-104 Ks-1), high temperatures (up to 1500C) and is valid for different biomass particle sizes (< 10 mm). The model was developedto estimate the yields of volatile gas and char. The mod...... the charyield of woody and herbaceous biomass particles using one fixed set of kinetic parameters valid for woody andherbaceous biomass....... relies on the concept applied in fast pyrolysis of cellulose throughthe formation of an intermediate liquid (so called metaplast) which reacts further to char and gas. The kinetics of the fastpyrolysis was described by the Broido-Shafizadeh scheme.The influence of particle size and shape was included...... obtained in the wire mesh and drop tube reactors. Thus, the modelincluding these two parameters provides an acceptable fit of char yield to the experimental data. The present results showedthat the proposed kinetic model for the fast biomass pyrolysis is relatively simple and predicts reasonably accurately...

  17. Correlation between electrochemical impedance measurements and corrosion rate of magnesium investigated by real-time hydrogen measurement and optical imaging

    OpenAIRE

    Curioni, M.; Scenini, F.; Monetta, T.; Bellucci, F.

    2015-01-01

    The corrosion behaviour of magnesium in chloride-containing aqueous environment was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) performed simultaneously with real-time hydrogen evolution measurements and optical imaging of the corroding surface. The potentiodynamic investigation revealed substantial deviations from linearity in close proximity of the corrosion potential. In particular, differences in the slope of the current/potential curves w...

  18. INVESTIGATION OF COMBUSTION, PERFORMANCE AND EMISSION CHARACTERISTICS OF SPARK IGNITION ENGINE FUELLED WITH BUTHANOL – GASOLINE MIXTURE AND A HYDROGEN ENRICHED AIR

    OpenAIRE

    Alfredas Rimkus; Mindaugas Melaika; Jonas Matijošius; Šarūnas Mikaliūnas; Saugirdas Pukalskas

    2016-01-01

    In this study, spark ignition engine fuelled with buthanol-gasoline mixture and a hydrogen-enriched air was investigated. Engine performance, emissions and combustion characteristics were investigated with different buthanol (10% and 20% by volume) gasoline mixtures and additionally supplied oxygen and hydrogen (HHO) gas mixture (3.6 l/min) in the sucked air. Hydrogen, which is in the HHO gas, improves gasoline and gasoline-buthanol mixture combustion, increases indicated pressure during comb...

  19. Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, Glenn Charles [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10

  20. Hydrogen Outgassing from Lithium Hydride

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, L N; Schildbach, M A; Smith, R A; Balazs1, B; McLean II, W

    2006-04-20

    Lithium hydride is a nuclear material with a great affinity for moisture. As a result of exposure to water vapor during machining, transportation, storage and assembly, a corrosion layer (oxide and/or hydroxide) always forms on the surface of lithium hydride resulting in the release of hydrogen gas. Thermodynamically, lithium hydride, lithium oxide and lithium hydroxide are all stable. However, lithium hydroxides formed near the lithium hydride substrate (interface hydroxide) and near the sample/vacuum interface (surface hydroxide) are much less thermally stable than their bulk counterpart. In a dry environment, the interface/surface hydroxides slowly degenerate over many years/decades at room temperature into lithium oxide, releasing water vapor and ultimately hydrogen gas through reaction of the water vapor with the lithium hydride substrate. This outgassing can potentially cause metal hydriding and/or compatibility issues elsewhere in the device. In this chapter, the morphology and the chemistry of the corrosion layer grown on lithium hydride (and in some cases, its isotopic cousin, lithium deuteride) as a result of exposure to moisture are investigated. The hydrogen outgassing processes associated with the formation and subsequent degeneration of this corrosion layer are described. Experimental techniques to measure the hydrogen outgassing kinetics from lithium hydride and methods employing the measured kinetics to predict hydrogen outgassing as a function of time and temperature are presented. Finally, practical procedures to mitigate the problem of hydrogen outgassing from lithium hydride are discussed.

  1. Investigations on the growth kinetics of Laves phase precipitates in 12% Cr creep-resistant steels: Experimental and DICTRA calculations

    International Nuclear Information System (INIS)

    Prat, O.; Garcia, J.; Rojas, D.; Carrasco, C.; Inden, G.

    2010-01-01

    The growth kinetics of Laves phase precipitates (type Fe 2 W) in the early stage of creep (650 deg. C for 10,000 h) in two 12% Cr ferrite-martensitic steels has been investigated. In one alloy the Laves phase formed on tempering, while in the second alloy the Laves phase precipitated during creep. Kinetic simulations were performed using the software DICTRA. The particle size of the Laves phase was measured on transmission electron microscopy samples. The equilibrium phase fraction of the Laves phase was reached in the first thousand hours. Simulations of particle growth showed good agreement with the experimental results. Competitive growth between M 23 C 6 and the Laves phase showed that M 23 C 6 carbides reached their equilibrium after 12 days, whereas the Laves phase reached equilibrium after 3 months. Simulations of the influence of the interfacial energy and addition of Co, Cu and Si on Laves phase precipitation are presented.

  2. Thermodynamic and Kinetic Requirements in Anaerobic Methane Oxidizing Consortia Exclude Hydrogen, Acetate, and Methanol as Possible Electron Shuttles.

    Science.gov (United States)

    Sørensen, K.B.; Finster, K.; Ramsing, N.B.

    2001-07-01

    Anaerobic methane oxidation (AMO) has long remained an enigma in microbial ecology. In the process the net reaction appears to be an oxidation of methane with sulfate as electron acceptor. In order to explain experimental data such as effects of inhibitors and isotopic signals in biomarkers it has been suggested that the process is carried out by a consortium of bacteria using an unknown compound to shuttle electrons between the participants. The overall change in free energy during AMO with sulfate is very small (?22 kJ mol-1) at in situ concentrations of methane and sulfate. In order to share the available free energy between the members of the consortium, the concentration of the intermediate electron shuttle compound becomes crucial. Diffusive flux of a substrate (i.e, the electron shuttle) between bacteria requires a stable concentration gradient where the concentration is higher in the producing organism than in the consuming organism. Since changes in concentrations cause changes in reaction free energies, the diffusive flux of a catabolic product/substrate between bacteria is associated with a net loss of available energy. This restricts maximal inter-bacterial distances in consortia composed of stationary bacteria. A simple theoretical model was used to describe the relationship between inter-bacterial distances and the energy lost due to concentration differences in consortia. Key parameters turned out to be the permissible concentration range of the electron shuttle in the consortium (i.e., the concentration range that allows both participants to gain sufficient energy) and the stoichiometry of the partial reactions. The model was applied to two known consortia degrading ethanol and butyrate and to four hypothetical methane-oxidizing consortia (MOC) based on interspecies transfer of hydrogen, methanol, acetate, or formate, respectively. In the first three MOCs the permissible distances between producers and consumers of the transferred compounds were

  3. An investigation of engine performance parameters and artificial intelligent emission prediction of hydrogen powered car

    International Nuclear Information System (INIS)

    Ho, Tien; Karri, Vishy; Lim, Daniel; Barret, Danny

    2008-01-01

    With the depletion of fossil fuel resources and the potential consequences of climate change due to fossil fuel use, much effort has been put into the search for alternative fuels for transportation. Although there are several potential alternative fuels, which have low impact on the environment, none of these fuels have the ability to be used as the sole 'fuel of the future'. One fuel which is likely to become a part of the over all solution to the transportation fuel dilemma is hydrogen. In this paper, The Toyota Corolla four cylinder, 1.8 l engine running on petrol is systematically converted to run on hydrogen. Several ancillary instruments for measuring various engine operating parameters and emissions are fitted to appraise the performance of the hydrogen car. The effect of hydrogen as a fuel compares with gasoline on engine operating parameters and effect of engine operating parameters on emission characteristics is discussed. Based on the experimental setup, a suite of neural network models were tested to accurately predict the effect of major engine operating conditions on the hydrogen car emissions. Predictions were found to be ±4% to the experimental values. This work provided better understanding of the effect of engine process parameters on emissions. (author)

  4. A statistical mechanical theory of proton transport kinetics in hydrogen-bonded networks based on population correlation functions with applications to acids and bases.

    Science.gov (United States)

    Tuckerman, Mark E; Chandra, Amalendu; Marx, Dominik

    2010-09-28

    Extraction of relaxation times, lifetimes, and rates associated with the transport of topological charge defects in hydrogen-bonded networks from molecular dynamics simulations is a challenge because proton transfer reactions continually change the identity of the defect core. In this paper, we present a statistical mechanical theory that allows these quantities to be computed in an unbiased manner. The theory employs a set of suitably defined indicator or population functions for locating a defect structure and their associated correlation functions. These functions are then used to develop a chemical master equation framework from which the rates and lifetimes can be determined. Furthermore, we develop an integral equation formalism for connecting various types of population correlation functions and derive an iterative solution to the equation, which is given a graphical interpretation. The chemical master equation framework is applied to the problems of both hydronium and hydroxide transport in bulk water. For each case it is shown that the theory establishes direct links between the defect's dominant solvation structures, the kinetics of charge transfer, and the mechanism of structural diffusion. A detailed analysis is presented for aqueous hydroxide, examining both reorientational time scales and relaxation of the rotational anisotropy, which is correlated with recent experimental results for these quantities. Finally, for OH(-)(aq) it is demonstrated that the "dynamical hypercoordination mechanism" is consistent with available experimental data while other mechanistic proposals are shown to fail. As a means of going beyond the linear rate theory valid from short up to intermediate time scales, a fractional kinetic model is introduced in the Appendix in order to describe the nonexponential long-time behavior of time-correlation functions. Within the mathematical framework of fractional calculus the power law decay ∼t(-σ), where σ is a parameter of the

  5. Purdue Hydrogen Systems Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Jay P Gore; Robert Kramer; Timothee L Pourpoint; P. V. Ramachandran; Arvind Varma; Yuan Zheng

    2011-12-28

    The Hydrogen Systems Laboratory in a unique partnership between Purdue University's main campus in West Lafayette and the Calumet campus was established and its capabilities were enhanced towards technology demonstrators. The laboratory engaged in basic research in hydrogen production and storage and initiated engineering systems research with performance goals established as per the USDOE Hydrogen, Fuel Cells, and Infrastructure Technologies Program. In the chemical storage and recycling part of the project, we worked towards maximum recycling yield via novel chemical selection and novel recycling pathways. With the basic potential of a large hydrogen yield from AB, we used it as an example chemical but have also discovered its limitations. Further, we discovered alternate storage chemicals that appear to have advantages over AB. We improved the slurry hydrolysis approach by using advanced slurry/solution mixing techniques. We demonstrated vehicle scale aqueous and non-aqueous slurry reactors to address various engineering issues in on-board chemical hydrogen storage systems. We measured the thermal properties of raw and spent AB. Further, we conducted experiments to determine reaction mechanisms and kinetics of hydrothermolysis in hydride-rich solutions and slurries. We also developed a continuous flow reactor and a laboratory scale fuel cell power generation system. The biological hydrogen production work summarized as Task 4.0 below, included investigating optimal hydrogen production cultures for different substrates, reducing the water content in the substrate, and integrating results from vacuum tube solar collector based pre and post processing tests into an enhanced energy system model. An automated testing device was used to finalize optimal hydrogen production conditions using statistical procedures. A 3 L commercial fermentor (New Brunswick, BioFlo 115) was used to finalize testing of larger samples and to consider issues related to scale up

  6. Purdue Hydrogen Systems Laboratory

    International Nuclear Information System (INIS)

    Gore, Jay P.; Kramer, Robert; Pourpoint, Timothee L.; Ramachandran, P.V.; Varma, Arvind; Zheng, Yuan

    2011-01-01

    The Hydrogen Systems Laboratory in a unique partnership between Purdue University's main campus in West Lafayette and the Calumet campus was established and its capabilities were enhanced towards technology demonstrators. The laboratory engaged in basic research in hydrogen production and storage and initiated engineering systems research with performance goals established as per the USDOE Hydrogen, Fuel Cells, and Infrastructure Technologies Program. In the chemical storage and recycling part of the project, we worked towards maximum recycling yield via novel chemical selection and novel recycling pathways. With the basic potential of a large hydrogen yield from AB, we used it as an example chemical but have also discovered its limitations. Further, we discovered alternate storage chemicals that appear to have advantages over AB. We improved the slurry hydrolysis approach by using advanced slurry/solution mixing techniques. We demonstrated vehicle scale aqueous and non-aqueous slurry reactors to address various engineering issues in on-board chemical hydrogen storage systems. We measured the thermal properties of raw and spent AB. Further, we conducted experiments to determine reaction mechanisms and kinetics of hydrothermolysis in hydride-rich solutions and slurries. We also developed a continuous flow reactor and a laboratory scale fuel cell power generation system. The biological hydrogen production work summarized as Task 4.0 below, included investigating optimal hydrogen production cultures for different substrates, reducing the water content in the substrate, and integrating results from vacuum tube solar collector based pre and post processing tests into an enhanced energy system model. An automated testing device was used to finalize optimal hydrogen production conditions using statistical procedures. A 3 L commercial fermentor (New Brunswick, BioFlo 115) was used to finalize testing of larger samples and to consider issues related to scale up. Efforts

  7. Experimental Investigation of Adsorption Kinetics: Implications for Diurnals Variations of Martian Atmospheric Water.

    Science.gov (United States)

    Slank, R.; Farris, H. N.; Chevrier, V.

    2017-12-01

    Introduction: Ice at Mars' equatorial regions is unstable at geologically short timescales, due to factors like thermal properties of the regolith and depth [1]. The distribution of ice is governed by thermodynamics and kinetics, which largely depends on diffusive and adsorptive properties of the regolith [2] and are studied through simulation experiments on regolith analogs. Numerical models of water ice stability [3] often require kinetic parameters that are lacking for Mars relevant materials. Previous measurements were limited to clays [4] or did not account for temperature dependence [5]. Method: Measurements of input parameters are performed for different regoliths relevant to observations of the Martian surface: smectite, basalt, JSC-Mars 1, and nanophase ferric oxides [6]. While diffusive properties of some of these materials are well understood [7; 1; 8; 9], we seek to determine adsorption parameters, specifically the temperature dependencies for kinetics. Adsorption kinetic constants are derived from the change in mass of water adsorbed as a function of time on a thin layer ( 1mm thick) of regolith, resulting in minimum diffusion and maximum surface in contact with the atmosphere. The samples are baked for 24 hours at 100°C and then sealed in a desiccators placed in a freezer to cool the sample. All experiments are run in the Aries Mars Simulation Chamber. The chamber is evacuated to less that 1 mbar, filled with dry CO2 gas to atmospheric pressure, and chilled to the determined temperature. Once conditions are stable, the sample is measured and placed in the chamber. The sample is then exposed to a 6 mbar CO2 atmosphere at various temperatures (-12 to 3°C) and humidities (5 to 80%). Experiments are run for 4 to 8 hours, to allow the sample to reach steady state. During this time, mass, pressure, temperature, relative humidity, and water vapor pressure are recorded. References: [1] Beck, P. et al. (2010) JGR 115. [2] Chevrier, V.F. et al. (2008) Icarus

  8. Investigation of bleaching kinetics of the photochromic halogen-copper-cadmium glass

    International Nuclear Information System (INIS)

    Marczuk, K.; Ziemba, B.

    1997-01-01

    The curves of the isothermal glass bleaching kinetics of various conditions of exciting radiation are presented. Different values of radiation power, time of irradiation and temperature of samples were applied. analysis of the relaxation curves made it possible to distinguish three exponential components of the bleaching process with different time constants. For each component the relaxation coefficient has been determined. Basing on temperature dependence of the relaxation coefficients for the isothermal glass bleaching the activation energy for slow (E D = 0.46 eV) and fast (E K = 0.13 eV) colour centre decay process have been determined. (author)

  9. Investigation into kinetics of sorption of some radionuclides by mixed sorbents based on amorphous niobium phosphate

    International Nuclear Information System (INIS)

    Belkina, R.M.; Sukharev, Yu.I.; Egorov, Yu.V.; Plotnikov, V.I.

    1977-01-01

    A study has been made of kinetics of sorption of radionuclides 110 Ag, 60 Co, and 51 Cr by samples of amorphous stoichiometric niobium (5) phosphate. Ratios of the concentration conductivity to the mean radius of sorbent particles were calculated which are proportional to diffusivities. Increased specificity towards Cr 3+ ions of samples of ion exchangeable niobium phosphate containing cerium and treated with 0.1N HCl was established. This effect was explained by formation and subsequent destruction of the copolymer oxo-ol matrix of niobium and cerium, as a result of which a gel is formed with mosaic structure being favourable for sorption of three-charged ions

  10. Quantitative Evaluation of Dichloroacetic Acid Kinetics in Human -- A Physiologically-Based Pharmacokinetic Modeling Investigation

    Science.gov (United States)

    2008-01-01

    weight) Plasma VPLAC 4.4 (Merrill et al., 2005) Liver VLC 2.6 (Brown et al., 1997) Kidney VKC 0.44 (Brown et al., 1997) Rapidly perfused VRC 9.86...entire data set with the exception of individual subject optimized kinetic data reported by Schultz and Shangraw (2006). Perhaps the most challenging ...GSTzeta as well as the 0.02 mg/kg DCA administered daily in drinking water between the 2 challenges . If a person is administered 50 mg/kg/day by IV

  11. Equilibrium and kinetic studies of systems of hydrogen isotopes, lithium hydrides, aluminum, and LiAlO2

    International Nuclear Information System (INIS)

    Owen, J.H.; Randall, D.

    1976-01-01

    Tritium might be bred by the 6 Li(n,α)T reaction in a solid lithium alloy or compound in the blanket of a controlled thermonuclear reactor to avoid problems associated with molten lithium or lithium compounds. Li--Al and LiAlO 2 systems containing hydrogen, deuterium, or tritium were studied 10 to 15 years ago at the Savannah River Laboratory. This paper descibes measurements of (1) the distribution of tritium and helium throughout both α and β phases of irradiated Li--Al alloy, (2) the migration rate of tritium to the β phase during moderate heating, (3) equilibrium pressures as functions of temperature of H 2 , D 2 , or T 2 in contact with lithium hydrides + aluminum, Li--Al alloy, or irradiated Li--Al alloy, (4) the equilibrium constant for the reaction LiH + Al → LiAl + 1 / 2 H 2 as a function of temperature, and (5) extraction rates of tritium from irradiated LiAlO 2 targets at elevated temperatures

  12. Kinetic method for determination of molybdenum(6) and tungsten(6) from oxidaton of O-aminophenol with hydrogen peroxide

    International Nuclear Information System (INIS)

    Krejngol'ts, S.U.; Vasnev, A.N.

    1978-01-01

    A new method for determination of Mo(6) and W(6), based on the oxidation of O-aminophenol with hydrogen peroxide, catalysed by Mo and W(6) ions, is suggested. The reaction takes place in the neutral medium at a rather high substrate concentrations. The 1.5 M acetate buffer solution, 0.2N EDTA and 0.1M solution of O-aminophenol in 0.1M HCl were suggested for determination of Mo (0.2N EDTA was used for Fe(3) camouflage). The 1.5M acetate buffer solution with 0.3M K 2 C 2 O 4 xH 2 O additions, for Fe(3) and Mo(6) camouflage, and 0.1M O-aminophenol solution in 0.1M solution of H 2 C 2 O 4 xH 2 O were used for tungsten determination. The range for Mo and W determination is 3x10 -3 and 1x10 -2 mkg/ml respectively. The range of Mo and W concentrations under determination is from 3x10 -3 -10 -2 to 2 mkg/ml. The techniques for the analysis of highly pure substances is developed

  13. [Kinetic characteristics of extracellular catalase from Penicillium piceum F-648 and variants of fungi, adapted to hydrogen peroxide].

    Science.gov (United States)

    Eremin, A N; Metelitsa, D I; Moroz, I V; Pavlovskaia, Zh I; Mikhaĭlova, R V

    2002-01-01

    A comparative kinetic study of extracellular catalases produced by Penicillium piceum F-648 and their variants adapted to H2O2 was performed in culture liquid filtrates. The specific activity of catalase, the maximum rate of catalase-induced H2O2 degradation (Vmax),Vmax/KM ratio, and the catalase inactivation rate constant in the enzymatic reaction (kin, s-1) were estimated in phosphate buffer (pH 7.4) at 30 degrees C. The effective constant representing the rate of catalase thermal inactivation (kin*, s-1) was determined at 45 degrees C. In all samples, the specific activity and KM for catalase were maximum at a protein concentration in culture liquid filtrates of 2.5-3.5 x 10(-4) mg/ml. The effective constants describing the rate of H2O2 degradation (k, s-1) were similar to that observed in the initial culture. These values reflected a twofold decrease in catalase activity in culture liquid filtrates. We hypothesized that culture liquid filtrates contain two isoforms of extracellular catalase characterized by different activities and affinities for H2O2. Catalases from variants 5 and 3 with high and low affinities for H2O2, respectively, had a greater operational stability than the enzyme from the initial culture. The method of adaptive selection for H2O2 can be used to obtain fungal variants producing extracellular catalases with improved properties.

  14. Investigation of low-resistivity from hydrogenated lightly B-doped diamond by ion implantation

    Directory of Open Access Journals (Sweden)

    Cui Xia Yan et al

    2008-01-01

    Full Text Available We have implanted boron (B ions (dosage: 5×1014 cm-2 into diamond and then hydrogenated the sample by implantating hydrogen ions at room temperature. A p-type diamond material with a low resistivity of 7.37 mΩ cm has been obtained in our experiment, which suggests that the hydrogenation of B-doped diamond results in a low-resistivity p-type material. Interestingly, inverse annealing, in which carrier concentration decreased with increasing annealing temperature, was observed at annealing temperatures above 600 °C. In addition, the formation mechanism of a low-resistivity material has been studied by density functional theory calculation using a plane wave method.

  15. Investigation of hydrogenase molecular marker to optimize hydrogen production from organic wastes and effluents of agro-food industries [abstract

    Directory of Open Access Journals (Sweden)

    Hamilton, C.

    2010-01-01

    Full Text Available In recent years policy makers have started looking for alternatives to fossil fuels, not only to counter the threat of global warming, but also to reduce the risk of overdependence on imported oil and gas supplies. By contrast with hydrocarbon fuels, hydrogen (H2, whether burned directly or used in fuel cells, is intrinsically a clean energy vector with near zero emission. However the main current method of producing hydrogen, steam reforming of methane, involves the release of large quantities of greenhouse gases. So although hydrogen already accounts for around 2% of world consumption of energy, its more widespread adoption is limited by several challenges. Therefore new processes are investigated, especially those using renewable raw material, e.g. woods and organic wastes, and/or involving microorganisms. Indeed, for some algae and bacteria, the generation of molecular hydrogen is an essential part of their energy metabolism. The approach with the greatest commercial potential is fermentative hydrogen generation (dark fermentation by bacteria from the Clostridium genus. This biological process, as a part of the methane-producing anaerobic digestion process, is very promising since it allows the production of hydrogen from a wide variety of renewable resources such as carbohydrate waste from the agricultural and agro-food industries or processed urban waste and sewage. To date most publications on hydrogen production by Clostridium strains have focused on the effects of operating parameters (such as temperature, pH, dilution rate, etc.. We now need to extend this knowledge by identifying and monitoring the various different metabolic agents involved in high H2 activity. Consequently the aim of this research at the CWBI in the University of Liege is to investigate the role of [Fe] hydrogenases, the key enzymes that remove excess electrons accumulating during fermentation. Clostridium butyricum CWBI1009, the strain used for these investigations

  16. An experimental investigation of the rate of hydrogen absorption in zirconium-2.5 wt percent niobium from steam/hydrogen mixtures at elevated temperatures

    International Nuclear Information System (INIS)

    Langman, V.J.

    1984-08-01

    The test specifications for an experimental program to study the rate of hydrogen absorption in zirconium-2.5 weight percent niobium pressure tube material from steam/hydrogen mixtures at elevated temperatures are discussed

  17. Contribution to the investigation of the structure and formation kinetics of a steroid gel

    International Nuclear Information System (INIS)

    Terech, Pierre

    1983-01-01

    This research thesis presents and discusses the results of the study of a thermally reversible gel made of a steroid system (nitroxide or amine)/cyclohexane. After a rheological characterization, the system in studied by EPR (Electronic Paramagnetic Resonance), small-angle neutron scattering, infrared absorption spectroscopy, optical and electronic microscopy, differential thermal analysis, and dichroism measurements (IR - visible - UV). The temperature/concentration phase diagram is determined for this over-saturation gel. The one-dimensional character of elements which make up the gel mesh, the radius of gyration for their section, the fibre linear compactness, and intermolecular distances are determined. Results can be interpreted by means of a hollow cylindrical fibre model in which molecules aggregate in helix. The electronic microscopy performed on the dried gel confirms the existence of long fibres with a secondary helical structure. Gelation kinetics can be described by a two-step model. The study of kinetic parameters confirms that over-saturation and H bonds are at the origin of the process [fr

  18. NMR studies of the influence of dodecyl sulfate on the amide hydrogen exchange kinetics of a micelle-solubilized hydrophobic tripeptide

    International Nuclear Information System (INIS)

    O'Neil, J.D.J.; Sykes, B.D.

    1989-01-01

    Backbone amide hydrogen exchange measurements are an important source of information about the internal dynamics of proteins. Before such measurements can be interpreted unambiguously, contributions to hydrogen exchange rates from the chemical and physical environment of the amides must be taken into account. Membrane proteins are often solubilized in detergents, yet there have not been any systematic investigations of the possible effects detergents may have on the amide hydrogen exchange rates of proteins. To address this question, the authors have measured individual backbone and carboxyl-terminal amide exchange rates for the amphipathic tripeptide Leu-Val-Ile-amide dissolved in water and dodecyl sulfate micelles. Proton NMR spectroscopy was used to measure exchange using the direct exchange-out into D 2 O technique at 5 degree C and using an indirect steady-state saturation-transfer technique at 25 degree C. The broadening effect of micelle-incorporated spin-labeled fatty acid (12-doxylsterate) on the 1 H NMR spectra of both the detergent and the peptide resonances was used to demonstrate that the tripeptide is intimately associated with the micelle. These experiments help to explain the elevated pH min observed for backbone amides in the sodium dodecyl sulfate solubilized M13 coat protein

  19. Ge(001):B gas-source molecular beam epitaxy: B surface segregation, hydrogen desorption, and film growth kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H.; Greene, J.E. [Materials Science Department, the Coordinated Science Laboratory and the Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States)

    1999-03-01

    Ultrahigh B-doped Ge(001) layers, with concentrations C{sub B} up to 8{times}10{sup 21} cm{sup {minus}3}, were grown by gas-source molecular beam epitaxy from Ge{sub 2}H{sub 6} and B{sub 2}H{sub 6} at temperatures T{sub s}=325{degree}C (in the surface-reaction-limited regime) and 600{degree}C (in the flux-limited regime). The samples were quenched, D site exchanged for H, and D{sub 2} temperature-programed desorption (TPD) used to determine B coverages {theta}{sub B} as a function of C{sub B} and T{sub s} by comparison with B-adsorbed Ge(001) reference samples with known {theta}{sub B} values. During Ge(001):B film growth, strong surface B segregation to the second layer was observed with surface-to-bulk B concentration ratios ranging up to 6000. The TPD spectra exhibited {alpha}{sub 2} and {alpha}{sub 1} peaks associated with dideuteride and monodeuteride desorption as well as lower-temperature B-induced {alpha}{sub 2}{sup {asterisk}} and {alpha}{sub 1}{sup {asterisk}} peaks associated with deuterium desorption from Ge{sup {asterisk}} surface atoms with B backbonds. Increasing {theta}{sub B} expanded the area under {alpha}{sub 2}{sup {asterisk}} and {alpha}{sub 1}{sup {asterisk}} at the expense of {alpha}{sub 2} and {alpha}{sub 1} and decreased the total D coverage {theta}{sub D}. The TPD results were used to determine the B segregation enthalpy, {minus}0.64 eV, and to explain and model the effects of high B coverages on Ge(001) growth kinetics. At T{sub s}=325{degree}C, where B segregation is kinetically hindered, film deposition rates R{sub Ge} are not a strong function of C{sub B}, exhibiting only a small decrease at C{sub B}{approx_gt}5{times}10{sup 18} cm{sup {minus}3}. However, at T{sub s}=600{degree}C, R{sub Ge} decreases by up to 40{percent} with increasing C{sub B}{approx_gt}1{times}10{sup 18} cm{sup {minus}3}. This is due primarily to the combination of B-induced Ge dimer vacancies and the deactivation of surface dangling bonds caused by charge transfer

  20. Experimental investigations relevant for hydrogen and fission product issues raised by the Fukushima accident

    Directory of Open Access Journals (Sweden)

    Sanjeev Gupta

    2015-02-01

    Full Text Available The accident at Japan's Fukushima Daiichi nuclear power plant in March 2011, caused by an earthquake and a subsequent tsunami, resulted in a failure of the power systems that are needed to cool the reactors at the plant. The accident progression in the absence of heat removal systems caused Units 1-3 to undergo fuel melting. Containment pressurization and hydrogen explosions ultimately resulted in the escape of radioactivity from reactor containments into the atmosphere and ocean. Problems in containment venting operation, leakage from primary containment boundary to the reactor building, improper functioning of standby gas treatment system (SGTS, unmitigated hydrogen accumulation in the reactor building were identified as some of the reasons those added-up in the severity of the accident. The Fukushima accident not only initiated worldwide demand for installation of adequate control and mitigation measures to minimize the potential source term to the environment but also advocated assessment of the existing mitigation systems performance behavior under a wide range of postulated accident scenarios. The uncertainty in estimating the released fraction of the radionuclides due to the Fukushima accident also underlined the need for comprehensive understanding of fission product behavior as a function of the thermal hydraulic conditions and the type of gaseous, aqueous, and solid materials available for interaction, e.g., gas components, decontamination paint, aerosols, and water pools. In the light of the Fukushima accident, additional experimental needs identified for hydrogen and fission product issues need to be investigated in an integrated and optimized way. Additionally, as more and more passive safety systems, such as passive autocatalytic recombiners and filtered containment venting systems are being retrofitted in current reactors and also planned for future reactors, identified hydrogen and fission product issues will need to be coupled

  1. Hydrogen storage evaluation based on investigations of the catalytic properties of metal/metal oxides in electrospun carbon fibers

    Energy Technology Data Exchange (ETDEWEB)

    Im, Ji Sun; Lee, Young-Seak [Department of Fine Chemical Engineering and Chemistry, Chungnam National University, Daejeon 305-764 (Korea); Park, Soo-Jin [Department of Chemistry, Inha University, Incheon 402-751 (Korea); Kim, Taejin [Core Technology Research Center for Fuel Cell, Jeollabuk-do 561-844 (Korea)

    2009-05-15

    In order to investigate the catalytic capacity of metals and metal oxides based on electrospun carbon fibers for improving hydrogen storage, electrospinning and heat treatments were carried out to obtain metal/metal oxide-embedded carbon fibers. Although the fibers were treated with the same activation procedure, they had different pore structures, due to the nature of the metal oxide. When comparing the catalytic capacity of metal and metal oxide, metal exhibits better performance as a catalyst for the improvement of hydrogen storage, when considering the hydrogen storage system. When a metal oxide with an m.p. lower than the temperature of heat treatment was used, the metal oxide was changed to metal during the heat treatment, developing a micropore structure. The activation process produced a high specific surface area of up to 2900 m{sup 2}/g and a pore volume of up to 2.5 cc/g. The amount of hydrogen adsorption reached approximately 3 wt% at 100 bar and room temperature. (author)

  2. Investigation on molecular interaction of amino acids in aqueous disodium hydrogen phosphate solutions with reference to volumetric and compressibility measurements

    International Nuclear Information System (INIS)

    Kumar, Harsh; Singla, Meenu; Jindal, Rajeev

    2014-01-01

    Highlights: • Densities and speeds of sound of amino acids in aqueous disodium hydrogen phosphate. • Partial molar volumes and compressibility of transfer. • Positive values of transfer volume indicates interactions between ions of amino acids and TSC. • Ion–hydrophilic and hydrophilic–hydrophilic interactions are present. • Pair-wise interactions are dominant in the mixtures. -- Abstract: The interactions of amino acids glycine (Gly), L-alanine (Ala), and L-valine (Val) with disodium hydrogen phosphate (DSHP) as a function of temperature have been investigated by combination of volumetric and acoustic measurements. Densities (ρ) and speeds of sound (u) of amino acids in aqueous solutions of disodium hydrogen phosphate have been measured at T = (288.15, 293.15, 298.15, 303.15 and 308.15) K and atmospheric pressure. The apparent molar volume (V ϕ ), the partial molar volume (V ϕ 0 ) and standard partial molar volumes of transfer (ΔV ϕ 0 ) for amino acids from water to aqueous disodium hydrogen phosphate solutions have been calculated from density data. Partial molar adiabatic compressibility (κ ϕ,s ) and partial molar adiabatic compressibility of transfer (Δκ ϕ,S 0 ) have been calculated from speed of sound data. The pair (V AB , κ AB ) and triplet (V ABB , κ ABB ) interaction coefficient have been calculated from both the properties. The results have been explained based on competing patterns of interactions of co-solvents and the solute

  3. Investigation of Y6Mn23 and YMn12 intermetallic alloys under high hydrogen pressure

    Science.gov (United States)

    Filipek, S. M.; Sato, R.; Kuriyama, N.; Tanaka, H.; Takeichi, N.

    2010-03-01

    Among three intermetallic compounds existing in Y-Mn system the YMn2 and Y6Mn23 can easily form interstitial hydrides while for YMn12 existence of hydride has never been reported. At moderate hydrogen pressure YMn2 and Y6Mn23 transform into YMn2H4.5 and Y6Mn23H25 respectively. At high hydrogen pressure the YMn2 (C15 or C14 parent structure) forms a unique YMn2H6 (s.g. Fm3m) complex hydride of fluorite structure in which one Mn atom Mn(1) and Y randomly occupy the 8c sites while second manganese (Mn2) in position 4a forms complex anion with 6 hydrogen atoms located in positions 24e. Formation of YMn2H6 independently of the structure of parent phase (C14 or C15) as well as occupation of the same site (8c) by Y and Mn(1) atoms suggested that also Y6Mn23 and YMn12 could transform into YMn2H6 - type hydride in which suitable number of Y atoms will be substituted by Mn(1) in the 8c positions. This assumption was confirmed by exposing R6Mn23 and RMn12 to 1 GPa of hydrogen pressure at 1000C. Formation of (RxMn2-x)MnH6 (where x = 18/29 or 3/13 for R6Mn23 and RMn12 hydrides respectively) was confirmed by XRD. Hydrogen concentration in both R6Mn23 and RMn12 based hydrides reached H/Me = 2 thus value two times higher than in R6Mn23H25.

  4. Investigation of Y6Mn23 and YMn12 intermetallic alloys under high hydrogen pressure

    International Nuclear Information System (INIS)

    Filipek, S M; Sato, R; Kuriyama, N; Tanaka, H; Takeichi, N

    2010-01-01

    Among three intermetallic compounds existing in Y-Mn system the YMn 2 and Y 6 Mn 23 can easily form interstitial hydrides while for YMn 12 existence of hydride has never been reported. At moderate hydrogen pressure YMn 2 and Y 6 Mn 23 transform into YMn 2 H 4.5 and Y 6 Mn 23 H 25 respectively. At high hydrogen pressure the YMn 2 (C15 or C14 parent structure) forms a unique YMn 2 H 6 (s.g. Fm3m) complex hydride of fluorite structure in which one Mn atom Mn(1) and Y randomly occupy the 8c sites while second manganese (Mn2) in position 4a forms complex anion with 6 hydrogen atoms located in positions 24e. Formation of YMn 2 H 6 independently of the structure of parent phase (C14 or C15) as well as occupation of the same site (8c) by Y and Mn(1) atoms suggested that also Y 6 Mn 23 and YMn 12 could transform into YMn 2 H 6 - type hydride in which suitable number of Y atoms will be substituted by Mn(1) in the 8c positions. This assumption was confirmed by exposing R 6 Mn 23 and RMn 12 to 1 GPa of hydrogen pressure at 100 0 C. Formation of (R x Mn 2-x )MnH 6 (where x = 18/29 or 3/13 for R 6 Mn 23 and RMn 12 hydrides respectively) was confirmed by XRD. Hydrogen concentration in both R 6 Mn 23 and RMn 12 based hydrides reached H/Me = 2 thus value two times higher than in R 6 Mn 23 H 25 .

  5. Autoradiographic investigation of age-dependent proliferation kinetics in the mucosa of rat small intestine

    International Nuclear Information System (INIS)

    Kranz, D.; Laue, R.; Fuhrmann, I.

    1980-01-01

    Aging of cells depends on mitotic activity which is particularly evident in multicellular organisms. The cell kinetics of the mucosa of the small intestine in a total of 244 Wistar rats aged 6 days, 6 weeks, 6, 12, 23 and 28 months, resp., were studied histoautoradiographically. It could be demonstrated that the regeneration rate of cells per hour in the crypts of the small intestine and the migration velocity of the enterocytes differ in young and old individuals, and that the intermitotic cells have age-dependent properties as well. In addition, it could be proved that intermitotic cells have a non growth fraction, too, which, at an advanced age, decreases only slightly although significantly in terms of statistics. For the easily vulnerable crypt epithelium it is a reserve capacity and ban be included in the proliferating pool if necessary. (author)

  6. Wetting of biopolymer coatings: contact angle kinetics and image analysis investigation.

    Science.gov (United States)

    Farris, Stefano; Introzzi, Laura; Biagioni, Paolo; Holz, Torsten; Schiraldi, Alberto; Piergiovanni, Luciano

    2011-06-21

    The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values (θ(0)) ranged from ∼91° for chitosan to ∼30° for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a three-parameter decay equation [θ(t) = θ(0) exp(kt(n))] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanism of surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses. © 2011 American Chemical Society

  7. Computational investigation of kinetics of cross-linking reactions in proteins: importance in structure prediction.

    Science.gov (United States)

    Bandyopadhyay, Pradipta; Kuntz, Irwin D

    2009-01-01

    The determination of protein structure using distance constraints is a new and promising field of study. One implementation involves attaching residues of a protein using a cross-linking agent, followed by protease digestion, analysis of the resulting peptides by mass spectroscopy, and finally sequence threading to detect the protein folds. In the present work, we carry out computational modeling of the kinetics of cross-linking reactions in proteins using the master equation approach. The rate constants of the cross-linking reactions are estimated using the pKas and the solvent-accessible surface areas of the residues involved. This model is tested with fibroblast growth factor (FGF) and cytochrome C. It is consistent with the initial experimental rate data for individual lysine residues for cytochrome C. Our model captures all observed cross-links for FGF and almost 90% of the observed cross-links for cytochrome C, although it also predicts cross-links that were not observed experimentally (false positives). However, the analysis of the false positive results is complicated by the fact that experimental detection of cross-links can be difficult and may depend on specific experimental conditions such as pH, ionic strength. Receiver operator characteristic plots showed that our model does a good job in predicting the observed cross-links. Molecular dynamics simulations showed that for cytochrome C, in general, the two lysines come closer for the observed cross-links as compared to the false positive ones. For FGF, no such clear pattern exists. The kinetic model and MD simulation can be used to study proposed cross-linking protocols.

  8. The mechanism of ureido-pyrimidinone:2,7-diamido-naphthyridine complexation and the presence of kinetically controlled pathways in multicomponent hydrogen-bonded systems

    OpenAIRE

    de Greef, T.F.A.; Ligthart, G.B.W.L.; Lutz, M.; Spek, A.L.; Meijer, E.W.

    2008-01-01

    The kinetics of association of ureido-pyrimidinone (U) dimers, present either in the 4[1H]-keto form or in the pyrimidin-4-ol form, with 2,7-diamido-1,8-naphthyridine (N) into a complementary heterodimer have been investigated. The formation of heterodimers with 2,7-diamido-1,8-naphthyridine from pyrimidin- 4-ol dimers is much faster than from 4[1H]-pyrimidinone dimers. Using a combination of simple measurements and simulations, evidence for a bimolecular tautomerization step is presented. Fi...

  9. Structural and Kinetic Evidence for an Extended Hydrogen-Bonding Network in Catalysis of Methyl Group Transfer

    International Nuclear Information System (INIS)

    Doukov, T.; Hemmi, H.; Drennan, C.; Ragsdale, S.

    2007-01-01

    The methyltetrahydrofolate (CH 3 -H 4 folate) corrinoid-ironsulfur protein (CFeSP) methyltransferase (MeTr) catalyzes transfer of the methyl group of CH3-H4folate to cob(I)amide. This key step in anaerobic CO and CO 2 fixation is similar to the first half-reaction in the mechanisms of other cobalamin-dependent methyltransferases. Methyl transfer requires electrophilic activation of the methyl group of CH 3 -H 4 folate, which includes proton transfer to the N5 group of the pterin ring and poises the methyl group for reaction with the Co(I) nucleophile. The structure of the binary CH 3 -H 4 folate/MeTr complex (revealed here) lacks any obvious proton donor near the N5 group. Instead, an Asn residue and water molecules are found within H-bonding distance of N5. Structural and kinetic experiments described here are consistent with the involvement of an extended H-bonding network in proton transfer to N5 of the folate that includes an Asn (Asn-199 in MeTr), a conserved Asp (Asp-160), and a water molecule. This situation is reminiscent of purine nucleoside phosphorylase, which involves protonation of the purine N7 in the transition state and is accomplished by an extended H-bond network that includes water molecules, a Glu residue, and an Asn residue (Kicska, G. A., Tyler, P. C., Evans, G. B., Furneaux, R. H., Shi, W., Fedorov, A., Lewandowicz, A., Cahill, S. M., Almo, S. C., and Schramm, V. L. (2002) Biochemistry 41, 14489-14498). In MeTr, the Asn residue swings from a distant position to within H-bonding distance of the N5 atom upon CH 3 -H 4 folate binding. An N199A variant exhibits only ∼20-fold weakened affinity for CH 3 -H 4 folate but a much more marked 20,000-40,000-fold effect on catalysis, suggesting that Asn-199 plays an important role in stabilizing a transition state or high energy intermediate for methyl transfer

  10. Investigations on the influence of ion kinetic energy on mass discrimination in isotope ratio measurements using MC-ICPMS

    International Nuclear Information System (INIS)

    Fontaine, G.H.; Hattendorf, B.; Oberli, F.; Bourdon, B.; Guenther, D.

    2009-01-01

    Full text: Systematic dependence of mass discrimination on ICP operating parameters was investigated for two MCICPMS instruments, a Nu Plasma HR and a Nu Plasma 1700, which differ both in acceleration voltage and spectrometer geometry. Gas temperature variations were determined by absolute pressure measurements at the vacuum interface. Their influence on ion kinetic energy as monitored by means of a retardation filter fitted in front of an ion counting detector will be discussed and compared to effects resulting from variations in acceleration voltage. (author)

  11. Kinetic investigations of emulsion- and solvent-mediated radiation induced graft copolymerization of glycidyl methacrylate onto nylon-6 fibres

    International Nuclear Information System (INIS)

    Teo Ming Ting; Paveswari Sithambaranathan

    2017-01-01

    Kinetic behaviour of graft copolymerisation of glycidyl methacrylate onto nylon-6 fibres in solvent- and emulsion- media was investigated. The order for the dependence of the initial rate of grafting on the monomer concentration for solvent and emulsion grafting systems were found to be 1.65 and 1.57, respectively. The order of dependence of the initial rate of grafting on the absorbed dose was found to be 1.55 for solvent and 0.62 emulsion grafting systems. The results showed that grafting in both systems is controlled by diffusion mechanism and the degree of grafting can be effectively tuned by variation of the grafting parameters. (author)

  12. Actions of four organic acids in radix isatidis on endotoxin-neutralization investigated by kinetic turbidimetric assay.

    Science.gov (United States)

    Ma, Li; He, Ying-jun; Li, You; Gong, Mu-xin

    2012-06-01

    To investigate anti-endotoxin action of four OAs reacted with endotoxin by the LAL assay with KTA. Using a incubating kinetic tube reader and kinetic turbidimetric assay (KTA), the concentration-response time curve of endotoxin reacted with limulus amebocyte lysate (LAL) at 37 degrees C were obtained and the action of four organic acids (OAs) on it were investigated. The four OAs were benzoic acid, salicylic acid, syringic acid and 2-amino-benzoic acid from Radix isatidis. Meanwhile, the temperature variation caused by endotoxin with the four OAs was studied by the rabbit pyrogen test (RPT). It was showed that a low concentration (1 mg/mL) of the four OAs had a little effect of anti-endotoxin, and when the concentrations of the four OAs were 30 mg/mL, the endotoxin was neutralized completely. The relationships between the concentrations of endotoxin and the OAs were all linear with correlation coefficients of greater than 0.9995, indicating that the four OAs all had strong anti-endotoxin action, while syringic acid had the strongest action among the four OAs with IC50 of 12.84 mg/mL. The investigations of KTA agreed well with the results obtained by means of RPT.

  13. Investigation of Acorn fruit Ash Efficiency in Cadmium Removal from Aqueous Solutions: Adsorption Isotherm and Kinetic Studies

    Directory of Open Access Journals (Sweden)

    Salman Zarei

    2014-12-01

    Full Text Available Background: Heavy metals are known as significant pollutants because of toxicity and nonbiodegradable characteristics. Cadmium is one of the heavy metals that have carcinogen potential. So, this study carried out in order to investigate the acorn fruit ash efficiency in cadmium removal from aqueous solutions. Methods: This study was done in the batch laboratory conditions. In this study, the effect of different parameters including pH, contact time, adsorbent dose, and initial cadmium concentration were evaluated. The Langmuir, Freundlich and Temkin isotherm models were used for analysis of the equilibrium isotherm. Adsorption kinetics of cadmium by different models were also investigated. The measurement of residual cadmium in the samples was determined by atomic absorption spectrophotometry at 228.8 nm. The SPSS-16 software was used for analysis of data. Results: According to the results, the maximum adsorption capacity of cadmium was 9.29 mg/g at pH=7 and 8 g/L adsorbent dose. The removal efficiency was increased with increasing contact time and decreased with increasing of cadmium initial concentration. Investigation of achieving data showed that the adsorption process followed better by Freundlich isotherm and the pseudo-second order kinetic. Conclusions: According to the results of this study, it could be concluded that the acorn fruit ash had high ability in cadmium adsorption and could be used as a cheap adsorbent in the removal of cadmium.

  14. Chemical kinetic modeling of H{sub 2} applications

    Energy Technology Data Exchange (ETDEWEB)

    Marinov, N.M.; Westbrook, C.K.; Cloutman, L.D. [Lawrence Livermore National Lab., CA (United States)] [and others

    1995-09-01

    Work being carried out at LLNL has concentrated on studies of the role of chemical kinetics in a variety of problems related to hydrogen combustion in practical combustion systems, with an emphasis on vehicle propulsion. Use of hydrogen offers significant advantages over fossil fuels, and computer modeling provides advantages when used in concert with experimental studies. Many numerical {open_quotes}experiments{close_quotes} can be carried out quickly and efficiently, reducing the cost and time of system development, and many new and speculative concepts can be screened to identify those with sufficient promise to pursue experimentally. This project uses chemical kinetic and fluid dynamic computational modeling to examine the combustion characteristics of systems burning hydrogen, either as the only fuel or mixed with natural gas. Oxidation kinetics are combined with pollutant formation kinetics, including formation of oxides of nitrogen but also including air toxics in natural gas combustion. We have refined many of the elementary kinetic reaction steps in the detailed reaction mechanism for hydrogen oxidation. To extend the model to pressures characteristic of internal combustion engines, it was necessary to apply theoretical pressure falloff formalisms for several key steps in the reaction mechanism. We have continued development of simplified reaction mechanisms for hydrogen oxidation, we have implemented those mechanisms into multidimensional computational fluid dynamics models, and we have used models of chemistry and fluid dynamics to address selected application problems. At the present time, we are using computed high pressure flame, and auto-ignition data to further refine the simplified kinetics models that are then to be used in multidimensional fluid mechanics models. Detailed kinetics studies have investigated hydrogen flames and ignition of hydrogen behind shock waves, intended to refine the detailed reactions mechanisms.

  15. Investigation of hydrogen and chlorine at the SiO2/Si interface

    International Nuclear Information System (INIS)

    Tsong, I.S.T.; Monkowski, M.D.; Monkowski, J.R.; Miller, P.D.; Moak, C.D.; Appleton, B.R.; Wintenberg, A.L.

    1980-01-01

    Silicon oxides thermally grown in H 2 O, O 2 , HCl/O 2 and Cl 2 /O 2 ambients were analyzed, via 1 H( 19 F,αγ) 16 O nuclear reaction and SIMS, for the presence of hydrogen. In addition, those oxides grown in HCl/O 2 and Cl 2 /O 2 ambients were analyzed with SIMS for the presence of chlorine. The SIMS data show that the hydrogen levels in these oxides were below the limit of detection for nuclear reaction experiments. The 35 Cl + depth-profiles show that chlorine is enriched at the SiO 2 interface for the HCl/O 2 grown oxides while it is more evenly distributed in oxide bulk in the Cl 2 /O 2 grown samples

  16. Investigation of confined hydrogen atom in spherical cavity, using B-splines basis set

    Directory of Open Access Journals (Sweden)

    M Barezi

    2011-03-01

    Full Text Available Studying confined quantum systems (CQS is very important in nano technology. One of the basic CQS is a hydrogen atom confined in spherical cavity. In this article, eigenenergies and eigenfunctions of hydrogen atom in spherical cavity are calculated, using linear variational method. B-splines are used as basis functions, which can easily construct the trial wave functions with appropriate boundary conditions. The main characteristics of B-spline are its high localization and its flexibility. Besides, these functions have numerical stability and are able to spend high volume of calculation with good accuracy. The energy levels as function of cavity radius are analyzed. To check the validity and efficiency of the proposed method, extensive convergence test of eigenenergies in different cavity sizes has been carried out.

  17. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    Science.gov (United States)

    Al-Rubaiey, Najem A.; Walsh, Robin

    2017-03-01

    Silylenes (silanediyls) have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD) of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2) are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas) at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using Lindemann

  18. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    Directory of Open Access Journals (Sweden)

    Al-Rubaiey Najem A.

    2017-01-01

    Full Text Available Silylenes (silanediyls have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2 are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using

  19. Investigation of Influential Parameters in Deep Oxidative Desulfurization of Dibenzothiophene with Hydrogen Peroxide and Formic Acid

    OpenAIRE

    Haghighat Mamaghani, Alireza; Fatemi, Shohreh; Asgari, Mehrdad

    2013-01-01

    An effective oxidative system consisting of hydrogen peroxide, formic acid, and sulfuric acid followed by an extractive stage were implemented to remove dibenzothiophene in the simulated fuel oil. The results revealed such a great performance in the case of H2O2 in the presence of formic and sulfuric acids that led to the removal of sulfur compounds. Sulfuric acid was employed to increase the acidity of media as well as catalytic activity together with formic acid. The oxidation reaction was ...

  20. Theoretical investigations into the blue-shifting hydrogen bond in benzene complexes

    Czech Academy of Sciences Publication Activity Database

    Špirko, Vladimír; Hobza, Pavel

    2006-01-01

    Roč. 7, č. 3 (2006), s. 640-643 ISSN 1439-4235 R&D Projects: GA ČR(CZ) GA203/05/0009; GA MŠk(CZ) LC512 Institutional research plan: CEZ:AV0Z40550506 Keywords : blue-shifting hydrogen bond * benzene complexes * London dispersion Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.449, year: 2006

  1. Polymerization kinetics of monomers of importance in biomedicine investigated by γirradiation

    International Nuclear Information System (INIS)

    Bebe, S.; Monteiro, M.J.; Ganachaud, F.; Napper, D.H.; Gilbert, R.G.

    1998-01-01

    Gamma irradiation was used to initiate the polymerization of NIPAM in water below the LCST. Conversion as a function of time was followed with automated tracking dilatometry. The data were used to show that classical kinetics were obeyed. Relaxation experiments (i.e. where the dilatometer is removed from the γ source) then provide reliable values for the reactivity ratio, k i /k p , the ratio of the termination to propagation rate coefficients. It was found at a monomer concentration of 0.442 M, k i k p had a value of 8.1 at 27 deg C . This suggested that either k t was very low, perhaps because the radicals are constrained to some complexation or aggregation mechanism, or k p is extraordinarily high. Pulsed laser polymerizations (in conjunction with size exclusion chromatography, SEC) were performed to obtain accurate k p values for NIPAM in water over a temperature range below the LCST (2 - 27 deg C ). The main difficulty with most functional polymers is obtaining quantitative data from SEC. PNIPAM is no exception to the rule, and meticulous care in molecular weight analysis was necessary. Special insights were developed into sample preparation to obtain accurate molecular weight distributions (MWD). The value k p was found to be high, but not extraordinarily so, and hence the high value of k t must be due to a constrained polymer radical

  2. Investigation into fatigue crack growth and kinetic diagrams of fatigue failure

    International Nuclear Information System (INIS)

    Yarema, S.Ya.

    1977-01-01

    Studies on fatigue failure are discussed in terms of fatigue failure kinetic diagrams (FFKD), in which the fatigue crack growth rate is plotted against the stress intensity coefficient (SIC). The physical sense of the crack growth rate and SIC is discussed and their applicability for description of the material in the destruction zone, particularly in presence of various media. Variation of experimental parameters (loading and environment) is followed by a transition period during which the results of the experiment may depend on its history, so that FFKD would remain invariant. Advantages of tests under constant experimental conditions are shown. The ways to stabilize SIC are indicated and requirements to the samples are given. As an example, the tests of disc samples made of plate materials are given, where SIC does not depend on the crack length. The question of controlling the experimental conditions such as asymmetry and shape of the loading cycle, loading frequency, fluctuations of temperature and air composition is considered. The analytical functions describing FFKD are discussed. It is shown, that in appropriate dimensionless coordinates the FFKD of different materials merge into one curve

  3. Curing behavior and reaction kinetics of binder resins for 3D-printing investigated by dielectric analysis (DEA)

    Science.gov (United States)

    Möginger, B.; Kehret, L.; Hausnerova, B.; Steinhaus, J.

    2016-05-01

    3D-Printing is an efficient method in the field of additive manufacturing. In order to optimize the properties of manufactured parts it is essential to adapt the curing behavior of the resin systems with respect to the requirements. Thus, effects of resin composition, e.g. due to different additives such as thickener and curing agents, on the curing behavior have to be known. As the resin transfers from a liquid to a solid glass the time dependent ion viscosity was measured using DEA with flat IDEX sensors. This allows for a sensitive measurement of resin changes as the ion viscosity changes two to four decades. The investigated resin systems are based on the monomers styrene and HEMA. To account for the effects of copolymerization in the calculation of the reaction kinetics it was assumed that the reaction can be considered as a homo-polymerization having a reaction order n≠1. Then the measured ion viscosity curves are fitted with the solution of the reactions kinetics - the time dependent degree of conversion (DC-function) - for times exceeding the initiation phase representing the primary curing. The measured ion viscosity curves can nicely be fitted with the DC-function and the determined fit parameters distinguish distinctly between the investigated resin compositions.

  4. Investigation of a hydrogen mitigation system during large break loss-of-coolant accident for a two-loop pressurized water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Dehjourian, Mehdi; Rahgoshay, Mohmmad; Jahanfamia, Gholamreza [Dept. of Nuclear Engineering, Science and Research Branch, Islamic Azad University of Tehran, Tehran (Iran, Islamic Republic of); Sayareh, Reza [Faculty of Electrical and Computer Engineering, Kerman Graduate University of Technology, Kerman (Iran, Islamic Republic of); Shirani, Amir Saied [Faculty of Engineering, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

    2016-10-15

    Hydrogen release during severe accidents poses a serious threat to containment integrity. Mitigating procedures are necessary to prevent global or local explosions, especially in large steel shell containments. The management of hydrogen safety and prevention of over-pressurization could be implemented through a hydrogen reduction system and spray system. During the course of the hypothetical large break loss-of-coolant accident in a nuclear power plant, hydrogen is generated by a reaction between steam and the fuel-cladding inside the reactor pressure vessel and also core concrete interaction after ejection of melt into the cavity. The MELCOR 1.8.6 was used to assess core degradation and containment behavior during the large break loss-of-coolant accident without the actuation of the safety injection system except for accumulators in Beznau nuclear power plant. Also, hydrogen distribution in containment and performance of hydrogen reduction system were investigated.

  5. Colloidal nanoparticle size control: experimental and kinetic modeling investigation of the ligand-metal binding role in controlling the nucleation and growth kinetics.

    Science.gov (United States)

    Mozaffari, Saeed; Li, Wenhui; Thompson, Coogan; Ivanov, Sergei; Seifert, Soenke; Lee, Byeongdu; Kovarik, Libor; Karim, Ayman M

    2017-09-21

    Despite the major advancements in colloidal metal nanoparticles synthesis, a quantitative mechanistic treatment of the ligand's role in controlling their size remains elusive. We report a methodology that combines in situ small angle X-ray scattering (SAXS) and kinetic modeling to quantitatively capture the role of ligand-metal binding (with the metal precursor and the nanoparticle surface) in controlling the synthesis kinetics. We demonstrate that accurate extraction of the kinetic rate constants requires using both, the size and number of particles obtained from in situ SAXS to decouple the contributions of particle nucleation and growth to the total metal reduction. Using Pd acetate and trioctylphosphine in different solvents, our results reveal that the binding of ligands with both the metal precursor and nanoparticle surface play a key role in controlling the rates of nucleation and growth and consequently the final size. We show that the solvent can affect the metal-ligand binding and consequently ligand coverage on the nanoparticles surface which has a strong effect on the growth rate and final size (1.4 nm in toluene and 4.3 nm in pyridine). The proposed kinetic model quantitatively predicts the effects of varying the metal concentration and ligand/metal ratio on nanoparticle size for our work and literature reports. More importantly, we demonstrate that the final size is exclusively determined by the nucleation and growth kinetics at early times and not how they change with time. Specifically, the nanoparticle size in this work and many literature reports can be predicted using a single, model independent kinetic descriptor, (growth-to-nucleation rate ratio) 1/3 , despite the different metals and synthetic conditions. The proposed model and kinetic descriptor could serve as powerful tools for the design of colloidal nanoparticles with specific sizes.

  6. Magnesium nanoparticles with transition metal decoration for hydrogen storage

    International Nuclear Information System (INIS)

    Pasquini, Luca; Callini, Elsa; Brighi, Matteo; Boscherini, Federico; Montone, Amelia; Jensen, Torben R.; Maurizio, Chiara; Vittori Antisari, Marco; Bonetti, Ennio

    2011-01-01

    We report on the hydrogen storage behaviour of Mg nanoparticles (NPs) (size range 100 nm–1 μm) with metal-oxide core–shell morphology synthesized by inert gas condensation and decorated by transition metal (TM) (Pd or Ti) clusters via in situ vacuum deposition. The structure and morphology of the as-prepared and hydrogenated NPs is studied by electron microscopy, X-ray diffraction including in situ experiments and X-ray absorption spectroscopy, in order to investigate the relationships with the hydrogen storage kinetics measured by the volumetric Sieverts method. With both Pd and Ti, the decoration deeply improves the hydrogen sorption properties: previously inert NPs exhibit complete hydrogenation with fast transformation kinetics, good stability and reversible gravimetric capacity that can attain 6 wt%. In the case of Pd-decoration, the occurrence of Mg–Pd alloying is observed at high temperatures and in dependence of the hydrogen pressure conditions. These structural transformations modify both the kinetics and thermodynamics of hydride formation, while Ti-decoration has an effect only on the kinetics. The experimental results are discussed in relation with key issues such as the amount of decoration, the heat of mixing between TM and Mg and the binding energy between TM and hydrogen.

  7. Hydrogenations of alloys and intermetallic compounds of magnesium

    International Nuclear Information System (INIS)

    Gavra, Z.

    1981-08-01

    A kinetic and thermodynamic study of the hydrogenation of alloys and intermetallic compounds of magnesium is presented. It was established that the addition of elements of the IIIA group (Al, Ga, In) to magnesium catalyses its hydrogenation. This is explained by the mechanism of diffusion of magnesium cation vacancies. The hydride Mg 2 NiH 4 was characterized by thermal analysis, x-ray diffraction and NMR measurements. The possibility of forming pseudo-binary compounds of Mg 2 Ni by the substitution of nickel or magnesium was examined. The hydrogenation of the inter-metallic compounds of the Mg-Al system was investigated. It was found that the addition of indium and nickel affected the hydrogenation kinetics. A preliminary study of the hydrogenation of various binary and ternary alloys of magnesium was carried out. (Author)

  8. Kinetic Investigations of the Role of Factor Inhibiting Hypoxia-inducible Factor (FIH) as an Oxygen Sensor.

    Science.gov (United States)

    Tarhonskaya, Hanna; Hardy, Adam P; Howe, Emily A; Loik, Nikita D; Kramer, Holger B; McCullagh, James S O; Schofield, Christopher J; Flashman, Emily

    2015-08-07

    The hypoxia-inducible factor (HIF) hydroxylases regulate hypoxia sensing in animals. In humans, they comprise three prolyl hydroxylases (PHD1-3 or EGLN1-3) and factor inhibiting HIF (FIH). FIH is an asparaginyl hydroxylase catalyzing post-translational modification of HIF-α, resulting in reduction of HIF-mediated transcription. Like the PHDs, FIH is proposed to have a hypoxia-sensing role in cells, enabling responses to changes in cellular O2 availability. PHD2, the most important human PHD isoform, is proposed to be biochemically/kinetically suited as a hypoxia sensor due to its relatively high sensitivity to changes in O2 concentration and slow reaction with O2. To ascertain whether these parameters are conserved among the HIF hydroxylases, we compared the reactions of FIH and PHD2 with O2. Consistent with previous reports, we found lower Km(app)(O2) values for FIH than for PHD2 with all HIF-derived substrates. Under pre-steady-state conditions, the O2-initiated FIH reaction is significantly faster than that of PHD2. We then investigated the kinetics with respect to O2 of the FIH reaction with ankyrin repeat domain (ARD) substrates. FIH has lower Km(app)(O2) values for the tested ARDs than HIF-α substrates, and pre-steady-state O2-initiated reactions were faster with ARDs than with HIF-α substrates. The results correlate with cellular studies showing that FIH is active at lower O2 concentrations than the PHDs and suggest that competition between HIF-α and ARDs for FIH is likely to be biologically relevant, particularly in hypoxic conditions. The overall results are consistent with the proposal that the kinetic properties of individual oxygenases reflect their biological capacity to act as hypoxia sensors. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  9. Reactions of oxygen and hydrogen with liquid sodium - a critical survey

    International Nuclear Information System (INIS)

    Ullmann, H.

    1982-01-01

    The fundamentals of solvation chemistry are presented with appropriate components formulated. Methods of investigation and kinetics of the reactions are described. The hydrogen equilibrium pressure and saturation solubilities are described. The chemical equilibrium between O and H in solution is presented with detailed tabulation of the saturation solutions of oxygen, hydrogen and hydroxide in liquid sodium. Agreements and differences with the literature are presented

  10. Determination of the Kinematics of the Qweak Experiment and Investigation of an Atomic Hydrogen Moller Polarimeter

    Energy Technology Data Exchange (ETDEWEB)

    Gray, Valerie M. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2018-01-01

    The Qweak experiment has tested the Standard Model through making a precise measurement of the weak charge of the proton (QpW). This was done through measuring the parity-violating asymmetry for polarized electrons scattering off of unpolarized protons. The parity-violating asymmetry measured is directly proportional to the four-momentum transfer (Q^2) from the electron to the proton. The extraction of QpW from the measured asymmetry requires a precise Q^2 determination. The Qweak experiment had a Q^2 = 24.8 ± 0.1 m(GeV^2) which achieved the goal of an uncertainty of <= 0.5%. From the measured asymmetry and Q^2, QpW was determined to be 0.0719 ± 0.0045, which is in good agreement with the Standard Model prediction. This puts a 7.5 TeV lower limit on possible "new physics". This dissertation describes the analysis of Q^2 for the Qweak experiment. Future parity-violating electron scattering experiments similar to the Qweak experiment will measure asymmetries to high precision in order to test the Standard Model. These measurements will require the beam polarization to be measured to sub-0.5% precision. Presently the electron beam polarization is measured through Moller scattering off of a ferromagnetic foil or through using Compton scattering, both of which can have issues reaching this precision. A novel Atomic Hydrogen Moller Polarimeter has been proposed as a non-invasive way to measure the polarization of an electron beam via Moller scattering off of polarized monatomic hydrogen gas. This dissertation describes the development and initial analysis of a Monte Carlo simulation of an Atomic Hydrogen Moller Polarimeter.

  11. Hydrogen-exchange kinetics of the indole NH proton of the buried tryptophan in the constant fragment of the immunoglobulin light chain

    International Nuclear Information System (INIS)

    Kawata, Y.; Goto, Y.; Hamaguchi, K.; Hayashi, F.; Kobayashi, Y.; Kyogoku, Y.

    1988-01-01

    The constant fragment of the immunoglobulin light chain (type λ) has two trytophyl residues at positions 150 and 187. Trp-150 is buried in the interior, and Trp-187 lies on the surface of the molecule. The hydrogen-deuterium exchange kinetics of the indole NH proton Trp-150 were studied at various pH values at 25 0 C by 1 H nuclear magnetic resonance. Exchange rates were approximately first order in hydroxyl ion dependence above pH 8, were relatively independent of pH between pH 7 and 8, and decreased below pH 7. On the assumption that the exchange above pH 8 proceeds through local fluctuations of the protein molecule, the exchange rates between pH 7 and 8 through global unfolding were estimated. The exchange rate constant within this pH range at 25 0 C thus estimated was consistent with that of the global unfolding of the constant fragment under the same conditions as those reported previously. The activation energy for the exchange process at pH 7.8 was the same as that for the unfolding process by 2 M guanidine hydrochloride. The exchange rates of backbone NH protons were almost the same as that of the indole NH proton of Trp-150 at pH 7.l. These observations also indicated that the exchange between pH 7 and 8 occurs through global unfolding of the protein molecule and is rate-limited by the unfolding. At around pH 9, on the other hand, the activation energy for the exchange process of the indole NH proton of Trp-150 was smaller than that for the unfolding process, and the exchange rates differed according to the different signals of backbone NH protons. These findings together with the pH dependence of the rate constant indicated that exchange due to local fluctuations is predominant above pH 8

  12. The effects of temperature and pH on the kinetics of reactions between catalase and its suicide substrate hydrogen peroxide.

    Science.gov (United States)

    Ghadermarzi, M; Moosavi-Movahedi, A A

    1997-12-01

    Variation of initial (intact) activity (ai), inactivation rate constant (ki) and the partition ratio (r) of bovine liver catalase in the reaction with its suicide substrate, hydrogen peroxide, were determined in workable ranges of temperature (17-42 degrees C) or pH (5-10.5), using the data of progress curves. The changes of temperature had a slight effect on ai, giving a Q10 of 1.15 for the enzymatic breakdown of H2O2, corresponding to an improved value for its activation energy of 8.8 +/- l kJ.mol-1. In contrast, the ki was greatly increased by elevation of temperature, giving a Q10 of 2.1 for the suicide inactivation reaction of catalase. Consequently, a significant decrease of r was observed by increasing of temperature. In pH studies, decreasing of pH from 7.0 to 5.0 led to reduction of ai whereas the ki value was not effected significantly, possibly due to the parallel changes in affinities to free catalase and compound I for H2O2. Reduction of ki and alpha i were observed at pH > 9.5, where reversible dissociation of tetrameric enzyme into catalytically inactive subunits is possible. The r had a maximum value at pH around 7.5, similar to that of catalase activity. The effect of ionic strength on the above kinetic parameters was studied. There was not an observable influence when the ammonium sulfate concentration was below l M.

  13. (e,2e) investigation of atomic hydrogen and helium close to threshold

    International Nuclear Information System (INIS)

    Schlemmer, P.; Rosel, T.; Jung, K.; Ehrhardt, H.

    1989-01-01

    For the first time triple differential cross sections of the electron impact ionization of atomic hydrogen close to threshold have been measured. The angular correlation of the outgoing electrons have been determined at 4 eV excess energy and are compared with results obtained with helium. A method is proposed allowing to measure the range of the threshold law. The data are analyzed using a partial-wave method. Although the asymptotic states of the two processes are the same---the charge of the ion is Z=1 in both cases---the triple differential cross sections are drastically different

  14. Theoretical investigation of image states of the hydrogen covered Cu (100)

    International Nuclear Information System (INIS)

    Steslicka, M.; Zagorski, M.; Jurczyszyn, L.

    1987-08-01

    A model of atomic hydrogen covered Cu(100) is presented and the calculated energy spectrum of localized electronic states in the X gap of Cu(100) is discussed. These states form a series of unoccupied adsorption image states (for n α = 2,3,...) lying below the vacuum level V 0 and having energies E nα which satisfy the formula E nα = V 0 - 10/n n 2 (eV). The lowest state (n α = 1) is expected to lie about 5.5 (eV) below Fermi level. (author). 19 refs, 6 figs, 1 tab

  15. An investigation of hydrogenized amorphous Si structures with Doppler broadening positron annihilation techniques

    International Nuclear Information System (INIS)

    Petkov, M.P.; Marek, T.; Asoka-Kumar, P.; Lynn, K.G.; Crandall, R.S.; Mahan, A.H.

    1998-01-01

    In this letter, we examine the feasibility of applying positron annihilation spectroscopy to the study of hydrogenized amorphous silicon (a-Si:H)-based structures produced by chemical vapor deposition techniques. The positron probe, sensitive to open volume formations, is used to characterize neutral and negatively charged silicon dangling bonds, typical for undoped and n-doped a-Si:H, respectively. Using depth profiling along the growth direction a difference was observed in the electronic environment of these defects, which enables their identification in a p-i-n device. copyright 1998 American Institute of Physics

  16. Hydrogen interaction kinetics of Ge dangling bonds at the Si0.25Ge0.75/SiO2 interface

    International Nuclear Information System (INIS)

    Stesmans, A.; Nguyen Hoang, T.; Afanas'ev, V. V.

    2014-01-01

    The hydrogen interaction kinetics of the GeP b1 defect, previously identified by electron spin resonance (ESR) as an interfacial Ge dangling bond (DB) defect occurring in densities ∼7 × 10 12  cm −2 at the SiGe/SiO 2 interfaces of condensation grown (100)Si/a-SiO 2 /Ge 0.75 Si 0.25 /a-SiO 2 structures, has been studied as function of temperature. This has been carried out, both in the isothermal and isochronal mode, through defect monitoring by capacitance-voltage measurements in conjunction with ESR probing, where it has previously been demonstrated the defects to operate as negative charge traps. The work entails a full interaction cycle study, comprised of analysis of both defect passivation (pictured as GeP b1 -H formation) in molecular hydrogen (∼1 atm) and reactivation (GeP b1 -H dissociation) in vacuum. It is found that both processes can be suitably described separately by the generalized simple thermal (GST) model, embodying a first order interaction kinetics description based on the basic chemical reactions GeP b1  + H 2  → GeP b1 H + H and GeP b1 H → GeP b1  + H, which are found to be characterized by the average activation energies E f  = 1.44 ± 0.04 eV and E d  = 2.23 ± 0.04 eV, and attendant, assumedly Gaussian, spreads σE f  = 0.20 ± 0.02 eV and σE d  = 0.15 ± 0.02 eV, respectively. The substantial spreads refer to enhanced interfacial disorder. Combination of the separately inferred