Sample records for temperature programmed desorption

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

    SciTech Connect

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

    1991-03-15

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

  2. Reduction Kinetics of Graphene Oxide Determined by Electrical Transport Measurements and Temperature Programmed Desorption

    E-print Network

    and Temperature Programmed Desorption Inhwa Jung, Daniel A. Field, Nicholas J. Clark, Yanwu Zhu, Dongxing Yang, Richard D. Piner, Sasha Stankovich,§ Dmitriy A. Dikin,§ Heike Geisler,| Carl A. Ventrice, Jr

  3. An investigation of the desorption of hydrogen from lithium oxide using temperature programmed desorption and diffuse reflectance infrared spectroscopy

    SciTech Connect

    Kopasz, J.P.; Johnson, C.E. [Argonne National Lab., IL (United States). Chemical Technology Div.; Ortiz-Villafuerte, J. [E.S.F.M., I.P.N., Zacatenco (Mexico). Nuclear Engineering Dept.

    1994-09-01

    The addition of hydrogen to the purge stream has been shown to enhance tritium release from ceramic breeder materials. In an attempt to determine the mechanism for this enhancement the authors have investigated the adsorption and desorption of hydrogen and water from lithium oxide (a leading candidate for the breeder material) by temperature programmed desorption and diffuse reflectance infrared spectroscopy. The results from these studies indicate that several different types of hydroxide groups are formed on the lithium oxide surface. They also suggest that under certain conditions hydride species form on the surface. The role of these species in tritium release from lithium oxide is discussed.

  4. Temperature programmed desorption from LiAlO 2 treated with H 2

    NASA Astrophysics Data System (ADS)

    Fischer, Albert K.

    1992-09-01

    Temperature programmed desorption (TPD) measurements have been made of H 2O and H 2 desorption from LiAlO 2 treated at 923 K with He-H 2 mixtures containing 990, 495, and 247 vppm H 2. Desorptions were into sweep gases of pure He and into He-H 2 mixtures. The H 2O and H 2 desorption peaks were shown to be the sums of first order subpeaks which had reproducible desorption activation energy and pre-exponential terms. For H 2O desorption, the activation energies were 96, 117, and 134 kJ/mol (23, 28, and 32 kcal/mol). (Earlier work had identified an additional peak with an activation energy of 75 kJ/mol (18 kcal/mol.) Enhancement of desorption of H 2O by H 2 in the sweep gas was confirmed. The enhancement results not from modifying the activation energies and pre-exponential terms for the various sites but from changes in the populations of sites participating in the desorption process so that sites with lower activation energies are increasingly involved. For those runs with He as the sweep gas, desorption of H 2 could be observed. The subpeaks involved had activation energies within approximately 4 kJ/mol (1 kcal/mol) higher than the analogous peaks for H 2O desorption.

  5. Analysis of molecular hydrogen formation on low-temperature surfaces in temperature programmed desorption experiments.

    PubMed

    Vidali, G; Pirronello, V; Li, L; Roser, J; Manicó, G; Congiu, E; Mehl, H; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

    2007-12-13

    The study of the formation of molecular hydrogen on low-temperature surfaces is of interest both because it enables the exploration of elementary steps in the heterogeneous catalysis of a simple molecule and because of its applications in astrochemistry. Here, we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments, beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations, and the energy barriers of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results are used in order to evaluate the formation rate of H2 on dust grains under the actual conditions present in interstellar clouds. It is found that, under typical conditions in diffuse interstellar clouds, amorphous silicate grains are efficient catalysts of H2 formation when the grain temperatures are between 9 and 14 K. This temperature window is within the typical range of grain temperatures in diffuse clouds. It is thus concluded that amorphous silicates are good candidates to be efficient catalysts of H2 formation in diffuse clouds. PMID:17988107

  6. Apparatus for temperature programmed desorption studies of thin films

    Microsoft Academic Search

    Babu R. Chalamala; David Uebelhoer; Robert H. Reuss

    2000-01-01

    A versatile analytical system based on thermal desorption spectroscopy of thin films is presented. We have found the apparatus to be a useful tool for measuring the desorption characteristics of trapped gases in physical vapor deposited thin films and in determining the thermal stability of multi-component thin film compounds and multilayer structures. The system was also found to be a

  7. Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments

    E-print Network

    Vidali, G; Li, L; Roser, J; Manico, G; Mehl, R; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

    2007-01-01

    The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions...

  8. Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments

    NASA Astrophysics Data System (ADS)

    Vidali, G.; Pirronello, V.; Li, L.; Roser, J.; Manico, G.; Mehl, R.; Lederhendler, A.; Perets, H. B.; Brucato, J. R.; Biham, O.

    The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions present in interstellar clouds.

  9. Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments

    E-print Network

    G. Vidali; V. Pirronello; L. Li; J. Roser; G. Manico; R. Mehl; A. Lederhendler; H. B. Perets; J. R. Brucato; O. Biham

    2008-11-21

    The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions present in interstellar clouds.

  10. Temperature programmed desorption studies of water interactions with Apollo lunar samples 12001 and 72501

    NASA Astrophysics Data System (ADS)

    Poston, Michael J.; Grieves, Gregory A.; Aleksandrov, Alexandr B.; Hibbitts, Charles A.; Dyar, M. Darby; Orlando, Thomas M.

    2015-07-01

    The desorption activation energies for water molecules chemisorbed on Apollo lunar samples 72501 (highlands soil) and 12001 (mare soil) were determined by temperature programmed desorption experiments in ultra-high vacuum. A significant difference in both the energies and abundance of chemisorption sites was observed, with 72501 retaining up to 40 times more water (by mass) and with much stronger adsorption interactions, possibly approaching 1.5 eV. The dramatic difference between the samples may be due to differences in mineralogy and surface exposure age. The distribution function of water desorption activation energies for sample 72501 was used as an initial condition to simulate water persistence through a temperature profile matching the lunar day.

  11. CF3I on a silicon surface: Adsorption, temperature-programmed desorption, and electron-stimulated desorption

    NASA Astrophysics Data System (ADS)

    Sanabia, Jason E.; Moore, John H.; Tossell, John A.

    2002-06-01

    CF3I adsorption on a silicon surface and the effect of low-energy electron bombardment of a CF3I-covered silicon surface are relevant to plasma etching. Dissociative chemisorption of CF3I on Si(100) surface is observed at 370 K. Uptake measurements corroborated by work-function change measurements and temperature-programmed desorption (TPD) gives a sticking probability of at least 0.34plus-or-minus0.05. Molecular orbital calculations yield an adsorption energy greater than 3 eV for dissociative chemisorption of CF3X (X=F, Cl, Br, and I) on Si(100) (modeled by Si9H12) with X transferred to a silicon atom. We conclude that the variation in the sticking probability across the CF3X family is a consequence of the activation energy barrier for C-X bond cleavage. In TPD, SiF4 desorbs at 370 and 840 K, SiF3 radical at 770 K, and atomic iodine at 790 K. The parent CF3I does not desorb. Electron-stimulated desorption (ESD) yields F+, F- and a trace of I+. The threshold for the appearance of F+ is 20 eV and for F- is 29 eV. Dissociative ionization and dipolar dissociation are possible mechanisms for ESD of F+. Dipolar dissociation and harpooning are possible mechanisms for ESD of F-. There is evidence that iodine on the surface quenches the electronically excited states that lead to desorption of F-.

  12. Using temperature-programmed desorption and the condensation approximation to determine surface site-energy distributions: examining the approximation's bases.

    SciTech Connect

    Brown, L. F. (Lee F.); Travis, B. J. (Bryan J.)

    2004-01-01

    Investigators (e.g., Seebauer 1994, Bogillo and Shkilev 1999) have used the condensation approximation (CA) successfully for determining broad nonuniform surface site-energy distributions (SEDs) from temperature-programmed desorption (TPD) spectra and for identifying constant pre-exponential factors from peak analysis. The CA assumes that at any temperature T, desorption occurs only at sites with a single desorption activation energy (E{sub cdn}). E{sub cdn} is of course a function of T. Further, the approximation assumes that during TPD all sites with desorption energy E{sub cdn} empty at T.

  13. Analyte separation utilizing temperature programmed desorption of a preconcentrator mesh

    DOEpatents

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

    2007-11-27

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

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

    SciTech Connect

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

    2004-10-01

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

  15. Qualitative and quantitative analysis of complex temperature-programmed desorption data by multivariate curve resolution

    NASA Astrophysics Data System (ADS)

    Rodríguez-Reyes, Juan Carlos F.; Teplyakov, Andrew V.; Brown, Steven D.

    2010-10-01

    The substantial amount of information carried in temperature-programmed desorption (TPD) experiments is often difficult to mine due to the occurrence of competing reaction pathways that produce compounds with similar mass spectrometric features. Multivariate curve resolution (MCR) is introduced as a tool capable of overcoming this problem by mathematically detecting spectral variations and correlations between several m/z traces, which is later translated into the extraction of the cracking pattern and the desorption profile for each desorbate. Different from the elegant (though complex) methods currently available to analyze TPD data, MCR analysis is applicable even when no information regarding the specific surface reaction/desorption process or the nature of the desorbing species is available. However, when available, any information can be used as constraints that guide the outcome, increasing the accuracy of the resolution. This approach is especially valuable when the compounds desorbing are different from what would be expected based on a chemical intuition, when the cracking pattern of the model test compound is difficult or impossible to obtain (because it could be unstable or very rare), and when knowing major components desorbing from the surface could in more traditional methods actually bias the quantification of minor components. The enhanced level of understanding of thermal processes achieved through MCR analysis is demonstrated by analyzing three phenomena: i) the cryogenic desorption of vinyltrimethylsilane from silicon, an introductory system where the known multilayer and monolayer components are resolved; ii) acrolein hydrogenation on a bimetallic Pt-Ni-Pt catalyst, where a rapid identification of hydrogenated products as well as other desorbing species is achieved, and iii) the thermal reaction of Ti[N(CH 3) 2] 4 on Si(100), where the products of surface decomposition are identified and an estimation of the surface composition after the thermal reaction is afforded. Since this work constitutes, to the best of our knowledge, the first effort to introduce multivariate analysis to TPD data, the procedures, algorithms and strategies employed are described in full detail.

  16. Solid-phase microextraction with temperature-programmed desorption for the analysis of iodination disinfection byproducts.

    PubMed

    Frazey, P A; Barkley, R M; Sievers, R E

    1998-02-01

    An analytical approach for the determination of chlorination and iodination disinfection byproducts based on solid-phase microextraction (SPME) was developed. Solid-phase microextraction presents a simple, rapid, sensitive, and solvent-free approach to sample preparation in which analytes in either air or water matrixes are extracted into the polymeric coating of an optical fiber. Analytes are subsequently thermally desorbed in the injection port of a gas chromatograph for separation, detection, and quantitation. Thermal degradation of iodoform was observed during desorption from a polyacrylate fiber in initial GC/MS and GC/ECD experiments. Experiments were designed to determine SPME conditions that would allow quantification without significant degradation of analytes. Isothermal and temperature-programmed thermal desorptions were evaluated for efficacy in transferring analytes with wide-ranging volatilities and thermal stabilities into chromatographic analysis columns. A temperature-programmed desorption (TPD) (120-200 degrees C at 5 degrees C/min with an on-column injection port or 150-200 degrees C at 25 degrees C/min with a split/splitless injection port) was able to efficiently remove analytes with wide-ranging volatilities without causing thermal degradation. The SPME-TPD method was linear over 2-3 orders of magnitude with an electron capture detector and detection limits were in the submicrogram per liter range. Precision and detection limits for selected trihalomethanes were comparable to those of EPA method 551. Extraction efficiencies were not affected by the presence of 10 mg/L soap, 15 mg/L sodium iodide, and 6000 mg/L sodium thiosulfate. The SPME-TPD technique was applied to the determination of iodination disinfection byproducts from individual precursor compounds using GC/MS and to the quantitation of iodoform at trace levels in a water recycle system using GC/ECD. PMID:9470491

  17. A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages

    Microsoft Academic Search

    Stefan Haegel; Thomas Zecho; Stefan Wehner

    2010-01-01

    In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved.

  18. The dissociation kinetics of NO on Rh(111) as studied by temperature programmed static secondary ion mass spectrometry and desorption

    NASA Astrophysics Data System (ADS)

    Borg, H. J.; Reijerse, J. F. C.-J. M.; van Santen, R. A.; Niemantsverdriet, J. W.

    1994-12-01

    Temperature programmed static secondary ion mass spectrometry (TPSSIMS) and temperature programmed desorption (TPD) have been used to study the kinetics of adsorption, dissociation, and desorption of NO on Rh(111). At 100 K, NO adsorption is molecular and proceeds via mobile precursor state kinetics with a high initial sticking probability. SSIMS indicates the presence of two distinct NO adsorption states, indicative of threefold adsorption at low coverage, and occupation of bridge sites at higher coverages. Three characteristic coverage regimes appear with respect to NO dissociation. At low coverages ?NO<0.25 ML, NO dissociates completely at temperatures between 275 and 340 K. If we neglect lateral interactions and assume pure first order dissociation kinetics, we find effective values for the activation barrier and preexponential factor of 40±6 kJ/mol and 106±1 s-1 for the dissociation of 0.15-0.20 ML NO. However, if we assume that a NO molecule needs an ensemble of three to four vacant sites in order to dissociate, the preexponential factor and activation energy are ˜1011 s-1 and 65 kJ/mol, in better agreement with transition state theory expectations. The Nads and Oads dissociation products desorb as N2 and O2, respectively, with desorption parameters Edes=118±10 kJ/mol and ?des=1010.1±1.0 s-1 for N2 in the zero coverage limit. At higher coverages, the desorption kinetics of N2 is strongly influenced by the presence of coadsorbed oxygen. In the medium coverage range 0.25desorption barrier of 113±10 kJ/mol and a preexponential of 1013.5±1.0 s-1. Dissociation of NO becomes progressively inhibited due to site blocking, the onset shifting from 275 K at 0.25 ML to 400 K, coinciding with the NO desorption temperature, at a coverage of 0.50 ML. The accumulation of nitrogen and oxygen atoms on the highly covered surface causes a destabilization of the nitrogen atoms, which results in an additional low-temperature desorption state for N2. For high initial NO coverages above 0.50 ML, the dissociation is completely self-inhibited, indicating that all sites required for dissociation are blocked. The desorption of the more weakly bound—presumably bridged—NO does not generate the sites required for dissociation; these become only available after the desorption of—presumably triply coordinated—NO.

  19. Interactions of N-alcohols with self-assembled monolayer surfaces on nickel(111) studied by temperature-programmed desorption

    NASA Astrophysics Data System (ADS)

    Vogt, Andrew Dale

    1999-12-01

    The interactions of molecules with self-assembled monolayer (SAM) surfaces formed on nickel (111) as studied by temperature-programmed desorption (TPD) are discussed. First, the adsorption of 11-mercaptoundecanoic acid (HS(CH 2)10COOH), 11-mercaptoundecanol (HS(CH2) 11OH) and octadecyl mercaptan (HS(CH2)17CH 3) was characterized by X-ray photoelectron spectroscopy (XPS) and angle-dependent XPS (ADXPS). These long-chain functionalized n-alkanethiols adsorbed onto a clean nickel (111) single crystal via their sulfur atom and the alkyl chain and the carboxyl-, hydroxyl- and methyl-terminal groups were disposed away from the nickel surface. The basic concepts of XPS, AMPS and TPD are discussed. Second, TPD showed that the interactions of low-molecular-weight straight-chain alcohols (n- CxH2x+1 OH for x = 1 through 6) with the carboxyl-, hydroxyl- and methyl-terminated SAM surfaces exhibited an alcohol-coverage-dependent effect on the alcohol's desorption energy based on their respective sets of TPD spectra at different alcohol coverages and based on the desorption spectra's subsequent analysis for desorption energy. The threshold TPD method (TTPD) was used to determine the desorption energy as a function of coverage for all alcohol-substrate pairs. For these adsorbate-substrate systems the desorption energies (TTPD) were the lowest (10--25 kJ mol-1) for the lowest relative alcohol coverages and increased to a desorption energy of 40--60 kJ mol-1 that was invariant with relative coverage after reaching a monolayer. The constant desorption energy (TTPD) at high relative coverages suggests there might be a completely formed hydrogen bonding network between adsorbates on the surfaces at alcohol coverages near a monolayer. The Redhead method, the "complete analysis" and the TTPD method are discussed and compared.

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

    SciTech Connect

    Zhuang, G.; Chottiner, G.; Scherson, D.A. [Case Western Univ., Cleveland, OH (United States)

    1995-05-04

    This paper presents temperature programmed desorption (TPD) data for perdeuterated propylene carbonate (PC-d{sub 6}) condensed at cryogenic temperatures on Li films vapor deposited onto polycrystalline (poly) Au and Ag foils and represents an extension of previous work involving the reactivity of tetrahydrofuran (THF) toward Li supported on Ag(poly). The findings suggest that the product of the reaction between PC and metallic Li is a lithium alkylcarbonate. The same type of species has been proposed to be the major constituent of the passive film on Li in PC in electrochemical environments based on in situ Fourier transform infrared spectroscopic studies. Experiments in which PC-d{sub 6} was intentionally mixed with CO{sub 2}, O{sub 2}, or H{sub 2}O showed that in each case the impurity reacts with Li to form the expected products without affecting, other than the net amount, the PC-d{sub 6}Li thermal decomposition pathway. 15 refs., 8 figs., 2 tabs.

  1. Study of the Evolution of Carbon Dioxide from Active Carbon by a Threshold Temperature-Programmed Desorption Method

    Microsoft Academic Search

    S. Haydar; J. P. Joly

    1998-01-01

    A particular Temperature-Programmed Desorption (TPD) method, called ‘Intermittent TPD’, has been applied to the decomposition\\u000a of oxygen groups naturally present at the surface of a microporous active carbon. It is shown that this method provides more\\u000a information on the kinetics of the thermal decomposition of these species than the classical TPD technique. The main result\\u000a is that the decomposition of

  2. New method for the temperature-programmed desorption (TPD) of ammonia experiment for characterization of zeolite acidity: a review.

    PubMed

    Niwa, Miki; Katada, Naonobu

    2013-10-01

    In this review, a method for the temperature-programmed desorption (TPD) of ammonia experiment for the characterization of zeolite acidity and its improvement by simultaneous IR measurement and DFT calculation are described. First, various methods of ammonia TPD are explained, since the measurements have been conducted under the concepts of kinetics, equilibrium, or diffusion control. It is however emphasized that the ubiquitous TPD experiment is governed by the equilibrium between ammonia molecules in the gas phase and on the surface. Therefore, a method to measure quantitatively the strength of the acid site (?H upon ammonia desorption) under equilibrium-controlled conditions is elucidated. Then, a quantitative relationship between ?H and H0 function is proposed, based on which the acid strength ?H can be converted into the H0 function. The identification of the desorption peaks and the quantitative measurement of the number of acid sites are then explained. In order to overcome a serious disadvantage of the method (i.e., no information is provided about the structure of acid sites), the simultaneous measurement of IR spectroscopy with ammonia TPD, named IRMS-TPD (infrared spectroscopy/mass spectrometry-temperature-programmed desorption), is proposed. Based on this improved measurement, Brønsted and Lewis acid sites were differentiated and the distribution of Brønsted OH was revealed. The acidity characterized by IRMS-TPD was further supported by the theoretical DFT calculation. Thus, the advanced study of zeolite acidity at the molecular level was made possible. Advantages and disadvantages of the ammonia TPD experiment are discussed, and understanding of the catalytic cracking activity based on the derived acidic profile is explained. PMID:23868494

  3. Interaction between water molecules and zinc sulfide nanoparticles studied by temperature-programmed desorption and molecular dynamics simulations.

    PubMed

    Zhang, Hengzhong; Rustad, James R; Banfield, Jillian F

    2007-06-14

    We have investigated the bonding of water molecules to the surfaces of ZnS nanoparticles (approximately 2-3 nm sphalerite) using temperature-programmed desorption (TPD). The activation energy for water desorption was derived as a function of the surface coverage through kinetic modeling of the experimental TPD curves. The binding energy of water equals the activation energy of desorption if it is assumed that the activation energy for adsorption is nearly zero. Molecular dynamics (MD) simulations of water adsorption on 3 and 5 nm sphalerite nanoparticles provided insights into the adsorption process and water binding at the atomic level. Water binds with the ZnS nanoparticle surface mainly via formation of Zn-O bonds. As compared with bulk ZnS crystals, ZnS nanoparticles can adsorb more water molecules per unit surface area due to the greatly increased curvature, which increases the distance between adjacent adsorbed molecules. Results from both TPD and MD show that the water binding energy increases with decreasing the water surface coverage. We attribute the increase in binding energy with decreasing surface water coverage to the increasing degree of surface under-coordination as removal of water molecules proceeds. MD also suggests that the water binding energy increases with decreasing particle size due to the further distance and hence lower interaction between adsorbed water molecules on highly curved smaller particle surfaces. Results also show that the binding energy, and thus the strength of interaction of water, is highest in isolated nanoparticles, lower in nanoparticle aggregates, and lowest in bulk crystals. Given that water binding is driven by surface energy reduction, we attribute the decreased binding energy for aggregated as compared to isolated particles to the decrease in surface energy that occurs as the result of inter-particle interactions. PMID:17518448

  4. Selectivity of dielectric heating: temperature-programmed desorption (TPD) experiments and initiation of thermo-chromatographic pulses.

    PubMed

    Roland, Ulf; Buchenhorst, Daniel; Kraus, Markus; Kopinke, Frank-Dieter

    2008-01-01

    The occurrence and extent of selective dielectric heating with microwaves (MW) and radio waves (RW) was studied with a variety of model systems using temperature-programmed desorption (TPD). Over a wide pressure and temperature range, selectivity effects were neither found for polar adsorbates (compared to non-polar compounds) nor expressed by an overheating of metal clusters supported on a nearly MW- and RW-transparent support. In contrast, significant temperature gradients between particles consisting of materials with various dielectric losses could be established under certain conditions. The utilization of adsorbates significantly modifying the dielectric properties of a material was investigated as a further approach to initiate selective dielectric heating. Applying water as a coupling medium, a combined heat and mass transport, which we call a thermo-chromatographic pulse, can be created in a packed-bed column consisting of various zeolites. In this case, selective heating of bed zones by more than 100 K was observed. The suitability of a material for the creation of thermo-chromatographic pulses depends on its dielectric properties as well as on its sorption properties with respect to water or other coupling media. The study provided further insight into not only the potential but also the limitations of selective dielectric heating of solid materials relevant to chemical engineering, environmental technology and sorption processing. PMID:19227066

  5. Interaction between Water Molecules and Zinc Sulfide Nanoparticles Studied by Temperature-Programmed Desorption and Molecular Dynamics Simulations.

    SciTech Connect

    Zhang, Hengzon; Rustad, James R.; Banfield, Jillian F.

    2007-05-23

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We have investigated the bonding of water molecules to the surfaces of ZnS nanoparticles (2-3 nm sphalerite) using temperature-programmed desorption (TPD). The activation energy for water desorption was derived as a function of the surface coverage through kinetic modeling of the experimental TPD curves. The binding energy of water equals the activation energy of desorption if it is assumed that the activation energy for adsorption is nearly zero. Molecular dynamics (MD) simulations of water adsorption on 3 and 5 nm sphalerite nanoparticles provided insights into the adsorption process and water binding at the atomic level. Water binds with the ZnS nanoparticle surface mainly via formation of Zn-O bonds. As compared with bulk ZnS crystals, ZnS nanoparticles can adsorb more water molecules per unit surface area due to the greatly increased curvature, which increases the distance between adjacent adsorbed molecules. Results from both TPD and MD show that the water binding energy increases with decreasing the water surface coverage. We attribute the increase in binding energy with decreasing surface water coverage to the increasing degree of surface under-coordination as removal of water molecules proceeds. MD also suggests that the water binding energy increases with decreasing particle size due to the further distance and hence lower interaction between adsorbed water molecules on highly curved smaller particle surfaces. Results also show that the binding energy, and thus the strength of interaction of water, is highest in isolated nanoparticles, lower in nanoparticle aggregates, and lowest in bulk crystals. Given that water binding is driven by surface energy reduction, we attribute the decreased binding energy for aggregated as compared to isolated particles to the decrease in surface energy that occurs as the result of inter-particle interactions.

  6. Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.

    PubMed

    Field, Christopher R; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C; Rose-Pehrsson, Susan L

    2014-01-01

    The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples. PMID:25145416

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

    PubMed Central

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

    2013-01-01

    An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release. PMID:23549366

  8. A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages

    NASA Astrophysics Data System (ADS)

    Haegel, Stefan; Zecho, Thomas; Wehner, Stefan

    2010-03-01

    In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach.

  9. A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages.

    PubMed

    Haegel, Stefan; Zecho, Thomas; Wehner, Stefan

    2010-03-01

    In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach. PMID:20370189

  10. A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages

    SciTech Connect

    Haegel, Stefan [Experimentalphysik III, Universitaet Bayreuth, 95440 Bayreuth (Germany); Zecho, Thomas [Nuclear Instrumentation, Areva NP GmbH, Paul-Gossen-Strasse 100, 91052 Erlangen (Germany); Wehner, Stefan [Experimentalphysik III, Universitaet Bayreuth, 95440 Bayreuth (Germany); Institut fuer Integrierte Naturwissenschaften-Physik, Universitaet Koblenz-Landau, Universitaetsstrasse 1, 56070 Koblenz (Germany)

    2010-03-15

    In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach.

  11. Surface hydration states of commercial high purity ?-Al 2O 3 powders evaluated by temperature programmed desorption mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

    Microsoft Academic Search

    Takashi Shirai; Jin Wang Li; Koji Matsumaru; Chanel Ishizaki; Kozo Ishizaki

    2005-01-01

    The surface of three different grades of commercial high-purity ?-Al2O3 powders produced by hydrolysis of aluminum alkoxide, which differ each other in SSA are evaluated by temperature programmed desorption mass spectrometry (TPDMS) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. For the DRIFT evaluation the powders were heated in situ under vacuum from 25 to 700°C. The TPDMS spectra of

  12. Molecular hydrogen desorption from amorphous surfaces at low temperature

    NASA Astrophysics Data System (ADS)

    Vidali, G.; Li, L.

    2010-08-01

    We studied the desorption of hydrogen molecules from amorphous silicates of composition (FexMg1 - x)2SiO4 (0 < x < 1) using thermal programmed desorption (TPD). Selected measurements of formation of molecular hydrogen on and desorption from a single crystal olivine sample were done for comparison. The experiments were conducted in conditions as close as technically possible to those found in selected interstellar medium environments, where the formation of molecular hydrogen takes place on dust grains. From molecular desorption data, we derive the energy distribution of binding sites using a direct inversion method. The application of this type of data to the study of elementary processes of migration of atoms and molecules on and ejection from disordered surfaces at low temperature is discussed.

  13. Molecular hydrogen desorption from amorphous surfaces at low temperature.

    PubMed

    Vidali, G; Li, L

    2010-08-01

    We studied the desorption of hydrogen molecules from amorphous silicates of composition (Fe(x)Mg(1 - x))(2)SiO(4) (0 < x < 1) using thermal programmed desorption (TPD). Selected measurements of formation of molecular hydrogen on and desorption from a single crystal olivine sample were done for comparison. The experiments were conducted in conditions as close as technically possible to those found in selected interstellar medium environments, where the formation of molecular hydrogen takes place on dust grains. From molecular desorption data, we derive the energy distribution of binding sites using a direct inversion method. The application of this type of data to the study of elementary processes of migration of atoms and molecules on and ejection from disordered surfaces at low temperature is discussed. PMID:21399344

  14. Gas chromatography/mass spectrometry analysis of components of pyridine temperature-programmed desorption spectra from surface of copper-supported catalysts.

    PubMed

    Pribylová, Lenka; Dvorák, Bohumír

    2009-05-01

    The method of pyridine temperature-programmed desorption (TPD) was applied for the measurement of acid properties of in situ reduced copper catalysts on silicate support. A thermal-conductivity detector (TCD) was used for the detection of TPD spectra of pyridine. The combination of flame-ionization detector and thermal conductivity detector shows that the region of TPD spectrum with the peak maxima T(MAX1)=350 degrees C is a superposition of the TCD response on spectra of desorbed pyridine, water and carbon dioxide, desorbing simultaneously from the catalyst surface. The method for the elimination of H(2)O and CO(2) on the layer of NaOH was tested and the pure TPD spectrum of pyridine was obtained. The exact determination of pyridine concentration allows to estimate the amount of weak and medium acid centers of the catalyst. The gas chromatography with the mass spectroscopy (GC-MS) analyses was used for the interpretation of high temperature region of the pyridine TPD spectra (T(MAX2)=620 degrees C). It was found that pyridine bonded on the strong acid centers is decomposed to N(2) and CO under very high temperature. The available chromatographic method for the separation of components present in pyridine TPD spectrum in the high-temperature region was suggested. The method for the quantification of strong acidity of copper-supported catalyst was found. PMID:19303075

  15. A Study of the Reactions of Ethanol on CeO 2 and Pd\\/CeO 2 by Steady State Reactions, Temperature Programmed Desorption, and In Situ FT-IR

    Microsoft Academic Search

    A. Yee; S. J. Morrison; H. Idriss

    1999-01-01

    The reaction of ethanol on unreduced and H2-reduced CeO2 and 1 wt% Pd\\/CeO2 has been investigated by steady state reactions, temperature programmed desorption (TPD), and in situ Fourier transform infrared (FT-IR) spectroscopy. Steady state reactions have shown a zero reaction order dependency for diatomic oxygen at and above 20%, whilst the addition of Pd to CeO2 decreases the apparent activation

  16. Electronic Desorption from Internal Surfaces of Porous Low Temperature Ice

    NASA Astrophysics Data System (ADS)

    Grieves, G. A.; Orlando, T. M.

    2006-05-01

    Radiation induced surface desorption from low temperature water ice plays a crucial role in the astrochemistry of icy planetary surfaces, comets and ice-covered interstellar grains. Excitations from low energy electrons (5- 100 eV) or VUV photons can hop between the strongly coupled hydrogen bonding network and migrate until they encounter a surface or a defect where they localize and induce dissociation. Ices deposited at very low temperatures, such as those in interstellar space, exhibit an exceptionally low density and have a highly porous amorphous structure. These pores represent large open structures and enclose a volume of vacuum and give the porous ice an enormous internal surface area. These pores are also likely to play an important role in spontaneous segregation of hydrophobic organic contaminants. The electronic structure of ice at the interface of these pores should resemble that of the outer surface vacuum interface. The effects of porosity and morphology of amorphous and crystalline D2O ices on the electron stimulated generation and trapping of D2 and O2 have been studied by post-irradiation thermal desorption. Molecular deuterium is released in the temperature range from 55 - 105 K for each of the samples, with two notable bursts at 115 and 132 K for porous amorphous ice. The majority of trapped O2 coevolves with desorption of the ice matrix, suggesting that clathrate hydrates may be important trapping sites. Production and trapping of organic polymers within pores from coadsorbed methane and ammonia are also discussed.

  17. Thermal Programmed Desorption of C32 H 66

    NASA Astrophysics Data System (ADS)

    Cisternas, M.; Del Campo, V.; Cabrera, A. L.; Volkmann, U. G.; Hansen, F. Y.; Taub, H.

    2011-03-01

    Alkanes are of interest as prototypes for more complex molecules and membranes. In this work we study the desorption kinetics of dotriacontane C32 adsorbed on Si O2 /Si substrate. We combine in our instrument High Resolution Ellipsometry (HRE) and Thermal Programmed Desorption (TPD). C32 monolayers were deposited in high vacuum from a Knudsen cell on the substrate, monitorizing sample thickness in situ with HRE. Film thickness was in the range of up to 100 AA, forming a parallel bilayer and perpendicular C32 layer. The Mass Spectrometer (RGA) of the TPD section was detecting the shift of the desorption peaks at different heating rates applied to the sample. The mass registered with the RGA was AMU 57 for parallel and perpendicular layers, due to the abundance of this mass value in the disintegration process of C32 in the mass spectrometers ionizer. Moreover, the AMU 57 signal does not interfere with other signals coming from residual gases in the vacuum chamber. The desorption energies obtained were ?Edes = 11,9 kJ/mol for the perpendicular bilayer and ?Edes = 23 ,5 kJ/mol for the parallel bilayer.

  18. Thermal desorption for passive dosimeter 

    E-print Network

    Liu, Wen-Chen

    1981-01-01

    temperature for 21 a passive dosimeter loaded vrith an organic chemical that ould provide the maximum desorption effi- ciency during thermal desorption; 2. To compare desorption efficiencies determined using thermal desorption and solvent desorption... S LIST CF FIGUHES II, THODUCT CI LIT=HATUHE BEVIES . Passive Dosimeter Activated Charcoal Theories of Adsorption Desorption IIethods Solvent Desorption Thermal Desorption Desorption Efficiency Determination Objectives NETHODOLOGY Chemicals...

  19. Temperature dependence of CO chemisorption and its oxidative desorption on the Pt(111) electrode

    Microsoft Academic Search

    Enrique Herrero; Juan M. Feliu; Sonia Blais; Zorana Radovic-Hrapovic; Gregory Jerkiewicz

    2000-01-01

    The influence of temperature variation on the CO{sub chem} oxidative desorption on Pt(111) electrodes is examined. A distinct shift of the CO{sub chem} stripping peak towards less-positive potentials is observed as the temperature is increased from 273 to 333 K. Despite the displacement of the desorption peak towards lower potentials, its current density and shape remain unaffected (for T â¤

  20. Reversibility, Dopant Desorption, and Tunneling in the Temperature-Dependent Conductivity of Type-Separated, Conductive Carbon Nanotube Networks

    SciTech Connect

    Barnes, T. M.; Blackburn, J. L.; van de Lagemaat, J.; Coutts, T. J.; Heben, M. J.

    2008-09-01

    We present a comprehensive study of the effects of doping and temperature on the conductivity of single-walled carbon nanotube (SWNT) networks. We investigated nearly type-pure networks as well as networks comprising precisely tuned mixtures of metallic and semiconducting tubes. Networks were studied in their as-produced state and after treatments with nitric acid, thionyl chloride, and hydrazine to explore the effects of both intentional and adventitious doping. For intentionally and adventitiously doped networks, the sheet resistance (R{sub s}) exhibits an irreversible increase with temperature above {approx}350 K. Dopant desorption is shown to be the main cause of this increase and the observed hysteresis in the temperature-dependent resistivity. Both thermal and chemical dedoping produced networks free of hysteresis. Temperature-programmed desorption data showed that dopants are most strongly bound to the metallic tubes and that networks consisting of metallic tubes exhibit the best thermal stability. At temperatures below the dopant desorption threshold, conductivity in the networks is primarily controlled by thermally assisted tunneling through barriers at the intertube or interbundle junctions.

  1. Low-Temperature, Vacuum-Aided Thermal Desorption Studies on a Simulated Organic Sludge Waste

    SciTech Connect

    R. K. Farnsworth; D. R. Peterman; Gary L. Anderson; T. G. Garn

    2002-12-01

    This report describes an initial set of small scale lab tests conducted on surrogate waste materials to investigate mass release behavior of volatile organics (VOC’s) from a solidified liquid organic sludge matrix under vacuumaided, low-temperature thermal desorption conditions. Low temperature thermal desorption is being considered as a potential processing technology alternative to incineration, to remove gas generation limitations affecting the transportation of transuranic (TRU) contaminated organic sludge wastes to a designated off-site repository (i.e., the Waste Isolation Pilot Plant). The lab-scale tests provide initial exploratory level information on temperature profiles and rates of volatile organic desorption for a range of initial VOC/oil liquid mixture concentrations in a calcium silicate matrix, under low temperature heating and vacuum boundary conditions that are representative of potentially desirable “in-drum desorption” conditions. The results of these tests indicate that reduced operating pressures have a potential for significantly enhancing the rate of thermal desorption experienced from a liquid organic/oil solidified “sludge” waste. Furthermore, the results indicate that in-drum thermal desorption can be performed on organic sludge wastes, at reduced pressures, while maintaining an operating temperature sufficiently low to prevent destruction of the waste drum packaging materials (confinement) surrounding the waste. The results also indicate that VOC release behavior/rates in the vacuum thermal desorption process cannot be represented by a simple liquid-liquid mass-diffusion model, since overall mass release rates observed are generally two orders of magnitude greater than predicted by simple liquid-liquid mass diffusion. This is partially attributed to the effects of the transient temperature profiles within the sludge during heat up; however, the primary cause is thought to be micro boiling of the volatile organics within the simulated sludge. Micro boiling of VOC’s would be expected to occur in localized volumes within the organic sludge where temperatures exceed the volatile organic saturation temperature sufficiently to form vapor bubbles. Further model based evaluations reflecting the transient temperatures, local boiling, and subsequent vapor in liquid/sludge transport conditions are needed, with supporting controlled testing of the vacuum-aided thermal desorption process at small and full-scale conditions in order to fully develop this process.

  2. Moisture adsorption–desorption isotherms of Citrus reticulata leaves at three temperatures

    Microsoft Academic Search

    A. Jamali; M. Kouhila; L. Ait Mohamed; A. Idlimam; A. Lamharrar

    2006-01-01

    The equilibrium moisture contents of Citrus reticulata leaves were measured by the gravimetric static method. The equilibrium was achieved after 12days for desorption and 10days for adsorption at 30, 40 and 50°C with water activity ranging from 5% to 90%. The sorption isotherms of C. reticulata leaves decreased with increase in temperature at constant relative humidity. An hysteresis effect was

  3. Study of atomic/molecular hydrogen diffusion on/desorption from amorphous surfaces at low temperature

    NASA Astrophysics Data System (ADS)

    Vidali, Gianfranco; Li, Ling

    2010-03-01

    We present results of experiments and calculations of the interaction of atomic and molecular hydrogen with amorphous solid surfaces at low (5-20 K) temperature. We obtain information on the mechanisms and energetics of atom/molecule diffusion and desorption, and on the efficiency of molecular hydrogen formation.

  4. CHARACTERISTICS OF MERCURY DESORPTION FROM SORBENTS AT ELEVATED TEMPERATURES. (R822721C697)

    EPA Science Inventory

    This study investigated the dynamic desorption characteristics of mercury during the thermal treatment of mercury-loaded sorbents at elevated temperatures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. ...

  5. CHARACTERISTICS OF MERCURY DESORPTION FROM SORBENTS AT ELEVATED TEMPERATURES. (R826694C697)

    EPA Science Inventory

    This study investigated the dynamic desorption characteristics of mercury during the thermal treatment of mercury-loaded sorbents at elevated temperatures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. ...

  6. Effect of temperature on Cs+ sorption and desorption in subsurface sediments at the Hanford Site, U.S.A.

    PubMed

    Liu, Chongxuan; Zachara, John M; Qafoku, Odeta; Smith, Steve C

    2003-06-15

    The effects of temperature on Cs+ sorption and desorption were investigated in subsurface sediments from the U.S. Department of Energy Hanford Site. The site has been contaminated at several locations by the accidental leakage of high-level nuclear waste (HLW) containing 137Cs+. The high temperature of the self-boiling, leaked HLW fluid and the continuous decay of various radionuclides carried by the waste supernatant have resulted in elevated vadose temperatures (currently up to 72 degrees C) below the Hanford S-SX tank farm that have dissipated slowly from the time of leakage (1970). The effect of temperature on Cs+ sorption was evaluated through batch binary Cs(+)-Na+ exchange experiments on pristine sediments, while Cs+ desorption was studied in column experiments using 137Cs(+)-contaminated sediments. Cs+ adsorption generally decreased with increasing temperature, with a more apparent decrease at low aqueous Cs+ concentration (10(-10)-10(-6) mol/L). Cs+ desorption from the contaminated sediments increased with increasing temperature. The results indicated that the free energy of Na(+)-Cs+ exchange on the Hanford sediment had a significant enthalpy component that was estimated to be -17.87 (+/- 2.01) and -4.82 (+/- 0.44) kJ/mol (at 298 degrees C) for the high- and low-affinity exchange sites, respectively. Both Cs+ adsorption and desorption at elevated temperature could be well simulated by a two-site ion exchange model, with the conditional exchange constants corrected by the exchange enthalpy effect. The effect of temperature on Cs+ desorption kinetics was also evaluated using a stop-flow technique. The kinetics of desorption of the exchangeable pool (which was less than the total adsorbed concentration) were found to be rapid under the conditions studied. PMID:12854700

  7. Temperature Programmed Liquid Chromatography

    Microsoft Academic Search

    Brian A. Jones

    2005-01-01

    Temperature programming in liquid chromatography is reviewed with an emphasis on instrumental methods, and emerging techniques. Column formats and stationary phases, both open tubular and packed, along with normal, reversed?phase and water—only mobile phases—are discussed. Attention is given particularly to separations with larger bore columns.

  8. Desorption Kinetics of Methanol, Ethanol, and Water from Graphene

    SciTech Connect

    Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.

    2014-09-18

    The desorption kinetics of methanol, ethanol, and water from graphene covered Pt(111) are investigated. The temperature programmed desorption (TPD) spectra for both methanol and ethanol have well-resolved first, second, third, and multilayer layer desorption peaks. The alignment of the leading edges is consistent with zero-order desorption kinetics from all layers. In contrast, for water the first and second layers are not resolved. At low water coverages (< 1 ML) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10 to 100 ML), the desorption leading edges are in alignment throughout the desorption of the film. The coverage dependence of the desorption behavoir suggests that at low water coverages the non-alignment of the desorption leading edges is due to water dewetting from the graphene substrate. Kinetic simulations reveal that the experimental results are consistent with zero-order desorption. The simulations also show that fractional order desorption kinetics would be readily apparent in the experimental TPD spectra.

  9. Material properties controlling adsorption kinetics and temperature programmed desorption spectra

    E-print Network

    Ward, Charles A.

    statistical rate theory (SRT) is applied to obtain the expression for the gas adsorption rate on a solid; Chemical potential 1. Introduction When adsorption at a gas­solid interface occurs, there is molecular 0 0 5 8 - 2 #12;SRT receives important experimental support from these cases. For gas adsorption

  10. Thermal desorption effects in chemical vapor deposition of silicon nanoparticles

    Microsoft Academic Search

    W. Thomas Leach; Jian-hong Zhu; John G Ekerdt

    2002-01-01

    Silicon nanoparticles are grown via ultra high vacuum chemical vapor deposition (UHV-CVD) on SiO2 and Si3N4 covered Si(100) substrates using disilane. Temperature programmed desorption spectra demonstrate the presence of H2 and SiO desorption features at 770 and 900K, respectively, which are in the 750–1000K temperature range that is typical for nanoparticle growth via CVD. The lower temperature limit (?750K) for

  11. Effects of temperature on trichloroethylene desorption from silica gel and natural sediments. 1. Isotherms

    SciTech Connect

    Werth, C.J.; Reinhard, M. [Stanford Univ., CA (United States)] [Stanford Univ., CA (United States)

    1997-03-01

    Aqueous phase isotherms were calculated from vapor phase desorption isotherms measured at 15, 30, and 60{degree}C for trichloroethylene on a silica gel, an aquifer sediment, a soil, a sand fraction, and a clay and silt fraction, all at 100% relative humidity. Isosteric heats of adsorption (Q{sub st}(q)) were calculated as a function of the sorbed concentration, q, and examined with respect to the following mechanisms: adsorption on water wet mineral surfaces, sorption in amorphous organic matter (AOM), and adsorption in hydrophobic micropores. Silica gel, sand fraction, and clay and silt fraction 60{degree}C isotherms are characterized by a Freundlich region and a region at very low concentrations where isotherm points deviate from log-log linear behavior. The latter is designated the non-Freundlich region. For the silica gel, values of Q{sub st}(q) (9.5-45 kJ/mol) in both regions are consistent with adsorption in hydrophobic micropores. For the natural solids, values of Q{sub st}(q) in the Freundlich regions are less than or equal to zero and are consistent with sorption on water wet mineral surfaces and in AOM. In the non-Freundlich regions, diverging different temperature isotherms with decreasing q and Q{sub st}(q) value of 34 kJ/mol for the clay and silt fraction suggest that adsorption is occurring in hydrophobic micropores. The General Adsorption Isotherm is used to capture this adsorption heterogeneity. 57 refs., 5 figs., 2 tabs.

  12. Moisture desorption rates from TATB formulations: experiments and kinetic models.

    PubMed

    Glascoe, Elizabeth A; Dinh, Long N; Small, Ward; Overturf, George E

    2012-06-01

    The rate of water desorption from PBX-9502, a formulation containing 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), is measured using temperature-programmed desorption and modeled using conventional kinetic modeling methods. The results of these studies show two stages of moisture release. At lower temperatures, the release is likely assisted by thermal expansion of the TATB and melting of the Kel-F binder. At higher temperatures, a considerable amount of water is released and is attributed to sublimation of the TATB, which exposes new surfaces for water desorption. PMID:22591128

  13. A program for evaluating dual-equilibrium desorption effects on remediation.

    PubMed

    Chen, Wei; Lakshmanan, Kalyan; Kan, Amy T; Tomson, Mason B

    2004-01-01

    Desorption is one of the most critical processes affecting the effectiveness of soil and ground water remediation. None of the currently adopted desorption models can accurately quantify desorption of low-hydrophobicity organic chemicals, and thus could potentially mislead remediation design and decision-making. A recently developed dual-equilibrium desorption (DED) model was found to be much more accurate in quantifying desorption. A screening-level transport model, DED-Transport, was developed to simulate the DED effect on behaviors of organic contaminant plumes during remediation. DED-Transport requires only simple parameters, but is applicable to many remediation scenarios. DED-Transport can be used as a decision-support tool in site remediation to more precisely predict the time required for cleanup. PMID:15318785

  14. Reproducibility of Temperature-Selected Mass Spectra in Matrix-Assisted Laser Desorption Ionization of Peptides

    E-print Network

    Kim, Myung Soo

    Ionization of Peptides Yong Jin Bae, Kyung Man Park, and Myung Soo Kim* Department of Chemistry, Seoul desorption ionization of peptides was investigated using -cyano-4-hydroxycinnamic acid as the matrix. In each kinetic analysis of the peptide ion survival probability. Tearly decreased as the shot continued because

  15. Adsorption and desorption of small molecules for the characterization of solid acids

    Microsoft Academic Search

    Hiromi Matsuhashi; Kazushi Arata

    2006-01-01

    The relative acid strength and acid amount of solid acids has been determined from the adsorption and desorption of small molecules, such as argon. The order of activation energy for desorption of Ar from a solid acid, determined using temperature-programmed desorption (TPD), is sulfated zirconia > Cs2.5H0.5PW12O40 > proton-type zeolites > silica–alumina. The adsorption isotherms were analyzed using Langmuir and Henry equations. The Henry-type adsorption isotherms

  16. Desorption of organic species from the GaAs (100) surface at low temperatures using low energy electron irradiation in a hydrogen ambient

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Schmidt, J.; Šiller, L.; Barnard, J. C.; Palmer, R. E.; Burke, T. M.; Smith, M. P.; Brown, S. J.; Ritchie, D. A.; Pepper, M.

    2000-05-01

    We present a technique for the controlled removal of organic adsorbates from the GaAs (100) surface incorporating hydrogen dosing (atomic or molecular) combined with low-energy electron irradiation. High-resolution electron energy-loss and Auger electron spectroscopes verify a considerable desorption of carbon/hydrocarbons following electron irradiation at 50 eV under a hydrogen atom flux even at room temperature. At a sample temperature of 500 °C, static secondary ion mass spectroscopy data demonstrate selective area removal of carbon from the surface following 25 eV electron irradiation in a molecular hydrogen ambient, with a desorption rate controlled by the incident electron flux.

  17. Thermally stimulated desorption of neutral CF3 from CF3I on Ag(111)

    NASA Astrophysics Data System (ADS)

    Junker, K. H.; Sun, Z.-J.; Scoggins, T. B.; White, J. M.

    1996-03-01

    The low temperature thermal chemistry of CF3I on Ag (111) presents an example of competing reaction pathways; molecular desorption vs desorption of radical CF3. Temperature programmed desorption and angle resolved temperature programmed desorption, complemented with Auger electron spectroscopy and low energy electron diffraction, were used to discern the mechanism of the CF3 radical desorption channel. CF3 desorption is limited to the first monolayer of CF3I; 0.75 ML CF3I is the coverage used for angular dependence measurements. At 90 K most of the CF3I adsorbs molecularly to the metal, but also present under these conditions are dissociative adsorption and thermal decomposition channels limited to C-I bond cleavage. The decomposition product, CF3, desorbs as a radical at high temperatures (˜320 K) with the I remaining on the surface until 850 K. At submonolayer CF3I coverages, thermal activation produces a low temperature (100-150 K) radical desorption channel. Results indicate that low temperature CF3 thermal desorption occurs via dissociative electron attachment to molecular CF3I, yielding radical CF3 and adsorbed iodine.

  18. Application of a diffusion-desorption rate equation model in astrochemistry.

    PubMed

    He, Jiao; Vidali, Gianfranco

    2014-01-01

    Desorption and diffusion are two of the most important processes on interstellar grain surfaces; knowledge of them is critical for the understanding of chemical reaction networks in the interstellar medium (ISM). However, a lack of information on desorption and diffusion is preventing further progress in astrochemistry. To obtain desorption energy distributions of molecules from the surfaces of ISM-related materials, one usually carries out adsorption-desorption temperature programmed desorption (TPD) experiments, and uses rate equation models to extract desorption energy distributions. However, the often-used rate equation models fail to adequately take into account diffusion processes and thus are only valid in situations where adsorption is strongly localized. As adsorption-desorption experiments show that adsorbate molecules tend to occupy deep adsorption sites before occupying shallow ones, a diffusion process must be involved. Thus, it is necessary to include a diffusion term in the model that takes into account the morphology of the surface as obtained from analyses of TPD experiments. We take the experimental data of CO desorption from the MgO(100) surface and of D2 desorption from amorphous solid water ice as examples to show how a diffusion-desorption rate equation model explains the redistribution of adsorbate molecules among different adsorption sites. We extract distributions of desorption energies and diffusion energy barriers from TPD profiles. These examples are contrasted with a system where adsorption is strongly localized--HD from an amorphous silicate surface. Suggestions for experimental investigations are provided. PMID:25302396

  19. Chemometric optimization of a low-temperature plasma source design for ambient desorption/ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Albert, Anastasia; Engelhard, Carsten

    2015-03-01

    Low-temperature plasmas (LTPs) are attractive sources for atomic and molecular mass spectrometry (MS). In the past, the LTP probe, which was first described by Harper et al., was used successfully for direct molecular mass spectrometric analysis with minimal sample pretreatment in a variety of applications. Unfortunately, the desorption/ionization source itself is commercially not available and custom-built LTP set-ups with varying geometry and operational configurations were utilized in the past. In the present study, a rapid chemometrics approach based on systematic experiments and multivariate data analysis was used to optimize the LTP probe geometry and positioning relative to the atmospheric-pressure inlet of a mass spectrometer. Several parameters were studied including the probe geometry, electrode configuration, quartz tube dimensions, probe positioning and operating conditions. It was found that the plasma-to-MS-inlet distance, the plasma-to-sample-plate distance, and the angle between the latter are very important. Additional effects on the analytical performance were found for the outer electrode width, the positioning of the electrodes, the inner diameter of the quartz tube, the quartz wall thickness, and the gas flow. All experiments were performed using additional heating of the sample to enhance thermal desorption and maximize the signal (T = 150 °C). After software-assisted optimization, attractive detection limits were achieved (e.g., 1.8 × 10- 7 mol/L for 4-acetamidothiophenol). Moreover, relative standard deviation (RSD) improved from values of up to 30% before optimization to < 15% RSD after the procedure was completed. This chemometrics approach for method optimization is not limited to LTP-MS and considered to be attractive for other plasma-based instrumentation as well.

  20. Temperature-dependent phase transition and desorption free energy of sodium dodecyl sulfate at the water/vapor interface: approaches from molecular dynamics simulations.

    PubMed

    Chen, Meng; Lu, Xiancai; Liu, Xiandong; Hou, Qingfeng; Zhu, Youyi; Zhou, Huiqun

    2014-09-01

    Adsorption of surfactants at the water/vapor interface depends upon their chemical potential at the interface, which is generally temperature-dependent. Molecular dynamics simulations have been performed to reveal temperature influences on the microstructure of sodium dodecyl sulfate (SDS) molecule adsorption layer. At room temperature, SDS molecules aggregate at the interface, being in a liquid-expanded phase, whereas they tend to spread out and probably transit to a gaseous phase as the temperature increases to above 318 K. This phase transition has been confirmed by the temperature-dependent changes in two-dimensional array, tilt angles, and immersion depths to the aqueous phase of SDS molecules. The aggregation of SDS molecules accompanies with larger immersion depths, more coordination of Na(+) ions, and less coordination of water. Desorption free energy profiles show that higher desorption free energy appears for SDS molecules at the aggregate state at low temperatures, but no energy barrier is observed. The shapes of desorption free energy profiles depend upon the distribution of SDS at the interface, which, in turn, is related to the phase state of SDS. Our study sheds light on the development of adsorption thermodynamics and kinetics theories. PMID:25127193

  1. Desorption of dye from activated carbon beds: effects of temperature, pH, and alcohol

    Microsoft Academic Search

    Jia-Ming Chern; Chia-Yuan Wu

    2001-01-01

    The adsorption isotherms of yellow and red dye solutions onto granular activated carbon at varying solution pHs (2–8), temperatures (15–50°C), and alcohol concentrations (0–20%) were experimentally determined by batch tests and the Tóth model was found to best fit the adsorption isotherm data for varying solution pHs, temperatures, and alcohol concentrations. The maximum adsorption capacity was found to decrease with

  2. Moisture adsorption–desorption isotherms of prickly pear cladode ( Opuntia ficus indica) at different temperatures

    Microsoft Academic Search

    S Lahsasni; M Kouhila; M Mahrouz; M Fliyou

    2003-01-01

    The equilibrium moisture contents of cladode of Opuntia ficus indica were determined using the gravimetric static method at 30, 40 and 50 °C over a range of relative humidity (Rh) from 0.05 to 0.9. The sorption capacity of cladode decreased with increase in temperature at constant Rh. The experimental sorption curves are then described by the GAB, Henderson’s and BET

  3. Oxygen sorption and desorption properties of selected lanthanum manganites and lanthanum ferrite manganites.

    PubMed

    Nielsen, Jimmi; Skou, Eivind M; Jacobsen, Torben

    2015-06-01

    Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La0.85 Sr0.15 )0.95 MnO3+? (LSM) and La0.60 Sr0.40 Fe0.80 Mn0.20 O3-? (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order. PMID:25784205

  4. Ultra high vacuum high precision low background setup with temperature control for thermal desorption mass spectroscopy (TDA-MS) of hydrogen in metals.

    PubMed

    Merzlikin, Sergiy V; Borodin, S; Vogel, D; Rohwerder, M

    2015-05-01

    In this work, a newly developed UHV-based high precision low background setup for hydrogen thermal desorption analysis (TDA) of metallic samples is presented. Using an infrared heating with a low thermal capacity enables a precise control of the temperature and rapid cool down of the measurement chamber. This novel TDA-set up is superior in sensitivity to almost every standard hydrogen analyzer available commercially due to the special design of the measurement chamber, resulting in a very low hydrogen background. No effects of background drift characteristic as for carrier gas based TDA instruments were observed, ensuring linearity and reproducibility of the analysis. This setup will prove to be valuable for detailed investigations of hydrogen trapping sites in steels and other alloys. With a determined limit of detection of 5.9×10(-3)µg g(-1) hydrogen the developed instrument is able to determine extremely low hydrogen amounts even at very low hydrogen desorption rates. This work clearly demonstrates the great potential of ultra-high vacuum thermal desorption mass spectroscopy instrumentation. PMID:25702992

  5. Desorption of chlorine organic solvents

    SciTech Connect

    Petrova, N.I.; Nikolaev, K.M.

    1982-03-01

    Adsorption methods are being used more and more widely to treat gaseous discharges containing chlorohydrocarbons. However, recovery of the chlorohydrocarbons has not been studied sufficiently, and the desorption of the solvents with steam is particularly understudied. We investigated desorption of a number of solvents from industrial active carbon AR-3. Desorption was done with live steam in the 105 to 150/sup 0/C. It can be seen from the data that with an increase of the molecular weight of the chlorohydrocarbon, the process of desorption slows down. This is clearly due to the fact that with an increase of the number of chlorine atoms in the molecule there is an increase of dispersion interaction (size of parachors) and latent heat of vaporization, which cause a decrease of the degree of desorption. The rate of desorption increases with an increase in temperature, but most of the investigated chlorine derivatives detach a chlorine ion at elevated temperature in the presence of water and carbon, with formation of HCl, which causes severe equipment corrosion. In addition, phosgene (in the decomposition of C/sub 2/HCl/sub 3/), chlorine organic acids and certain other toxic compounds may be produced. Thus, to reduce the rate of hydrolysis in the desorption of chlorohydrocarbons, especially polychlorinated ones, one should use steam with minimum possible temperature (no more than 110/sup 0/C) with a desorption time of no more than 30 minutes for poorly adsorbable compounds and no more than 45 to 60 minutes for readily absorbable ones. Here the degree of desorption of poorly absorbed compounds is about 100% while that of the readily absorbed ones is from 50 to 75%. The results were used in the design of units for recovery of methylene chloride, dichloroethane and trichloroethylene.

  6. Waste Isolation Safety Assessment Program. Task 4. Third Contractor Information Meeting. [Adsorption-desorption on geological media

    SciTech Connect

    Not Available

    1980-06-01

    The study subject of this meeting was the adsorption and desorption of radionuclides on geologic media under repository conditions. This volume contans eight papers. Separate abstracts were prepared for all eight papers. (DLC)

  7. Thermal desorption of circumstellar and cometary ice analogs

    NASA Astrophysics Data System (ADS)

    Martín-Doménech, R.; Muñoz Caro, G. M.; Bueno, J.; Goesmann, F.

    2014-04-01

    Context. Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. Aims: For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2O, CO, CO2, CH3OH, and NH3. Methods: The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. Results: The TPD curves of water ice containing CO, CO2, CH3OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and co-desorption peaks with water. Desorption peaks of CH3OH and NH3 at temperatures similar to the pure ices takes place when their abundance relative to water is above ~3% in the ice matrix. We found that CO, CO2, and NH3 also present co-desorption peaks with CH3OH, which cannot be reproduced in experiments with binary water-rich ice mixtures. These are extensively used in the study of thermal desorption of interstellar ices. Conclusions: These results reproduce the heating of circumstellar ices in hot cores and can be also applied to the late thermal evolution of comets. In particular, TPD curves represent a benchmark for the analysis of the measurements that mass spectrometers on board the ESA-Rosetta cometary mission will perform on the coma of comet 67P/Churyumov-Gerasimenko, which will be active before the arrival of Rosetta according to our predictions.

  8. Time-resolved photodissociation study of singly protonated peptides with a histidine residue generated by matrix-assisted laser desorption ionization: Dissociation rate constant and internal temperature

    Microsoft Academic Search

    So Hee Yoon; Jeong Hee Moon; Myung Soo Kim

    2009-01-01

    Product ion yields in post-source decay and time-resolved photodissociation at 193 and 266 nm were measured for some peptide\\u000a ions with a histidine residue ([HF6+H]+, [F6H+H]+, and [F3HF3+H]+) formed by matrix-assisted laser desorption ionization (MALDI). Compared with similar data for peptide ions without any basic\\u000a residue reported previously, significant reduction in dissociation efficiency was observed. Internal temperatures (T) of the

  9. Electron stimulated molecular desorption of a non-evaporable Zr-V-Fe alloy getter at room temperature

    Microsoft Academic Search

    F. Le Pimpec; O. Gröbner; J. M. Laurent

    2002-01-01

    Electron stimulated molecular desorption (ESD) from a non-evaporable getters (NEG) St 707® (SAES Getters) sample after conditioning and after saturation with isotopic carbon monoxide (cf. nomenclature in Handbook of Chemistry and Physics, CRC Press, 1994), 13C18O, has been studied on a laboratory setup. Measurements were performed using an electron beam of 300 eV kinetic energy, with an average electron intensity

  10. Electron stimulated molecular desorption of a non-evaporable Zr–V–Fe alloy getter at room temperature

    Microsoft Academic Search

    F. Le Pimpec; O. Gröbner; J. M. Laurent

    2002-01-01

    Electron stimulated molecular desorption (ESD) from a non-evaporable getters (NEG) St 707® (SAES Getters™) sample after conditioning and after saturation with isotopic carbon monoxide (cf. nomenclature in Handbook of Chemistry and Physics, CRC Press, 1994), 13C18O, has been studied on a laboratory setup. Measurements were performed using an electron beam of 300 eV kinetic energy, with an average electron intensity

  11. Atomic oxygen diffusion on and desorption from amorphous silicate surfaces.

    PubMed

    He, Jiao; Jing, Dapeng; Vidali, Gianfranco

    2014-02-28

    Surface reactions involving atomic oxygen have attracted much attention in astrophysics and astrochemistry, but two of the most fundamental surface processes, desorption and diffusion, are not well understood. We studied diffusion and desorption of atomic oxygen on or from amorphous silicate surfaces under simulated interstellar conditions using a radio-frequency dissociated oxygen beam. Temperature programmed desorption (TPD) experiments were performed to study the formation of ozone from reaction of atomic and molecular oxygen deposited on the surface of a silicate. It is found that atomic oxygen begins to diffuse significantly between 40 K and 50 K. A rate equation model was used to study the surface kinetics involved in ozone formation experiments. The value of atomic oxygen desorption energy has been determined to be 152 ± 20 meV (1764 ± 232 K). The newly found atomic oxygen desorption energy, which is much higher than the well-accepted value, might explain the discrepancy in abundance of molecular oxygen in space between observations and chemical models. PMID:24434834

  12. The Release of Trapped Gases from Amorphous Solid Water Films: II. “Bottom-Up” Induced Desorption Pathways

    SciTech Connect

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

    2013-03-14

    In this (Paper II) and the preceding companion paper (Paper I) we investigate the mechanisms for the release of trapped gases from underneath of amorphous solid water (ASW) films. In Paper I, we focused on the low coverage (pressure) regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage (pressure) regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that abrupt desorption bursts are due to pressure induced structural failure of the ASW overlyaer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores and connected pathways formed during ASW deposition. The extent of desorption and the lineshape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of the ASW is used vary the porosity of overlayer and confirm that the low temperature desorption pathway is due to porosity that is inherent in the ASW overlayer during deposition.

  13. Desorption of a two-state system: Laser probing of gallium atom spin-orbit states from silicon (100)

    NASA Astrophysics Data System (ADS)

    Carleton, Karen L.; Bourguignon, Bernard; Leone, Stephen R.

    The interactions of gallium atom spin-orbit states with silicon (100) surfaces are studied by temperature programmed desorption (TPD) using laser-induced fluorescence detection. State-resolved sticking coefficients are measured and are found to be unity for both spin-orbit states ( 2P{1}/{2}, 2P{3}/{2}, ?E = 2.5 kcal mol-1, 10.5 kJ mol-1) up to surface temperatures of 1000 K. A Redhead analysis of the state-specific TPD spectra yields essentially identical energies and pre-exponential factors for both spin-orbit states. A statistical branching ratio is observed between the 2P {1}/{2} and 2P {3}/{2} Ga states at the peak of the TPD curves. These results may be accounted for by a rapid interconversion between the two states during the desorption. Since the spin-orbit splitting in this case is small, a rapid interconversion may be anticipated; however, modeling the desorption kinetics yields important features for the desorption of a two-state system. The model shows that the Redhead analysis is not adequate to measure the desorption kinetic parameters of the individual states. The TPD spectra of the two states differ only very slightly because their shape is mainly controlled by the overall rate of desorption for the sum of the two channels. The population ratio between the states allows a direct comparison of the desorption energetics of the two channels. Errors of 5-10 kcal mol -1 can occur in a determination of the desorption energy of a hypothetical, slowly desorbing state if the presence of a rapid desorption channel is ignored. The model can be generalized to describe any multiple channel surface process, including multi-state desorption of the competition between desorption and diffusion into the bulk. These results are of interest in the epitaxial growth of GaAs on Si(100).

  14. Program predicts reservoir temperature and geothermal gradient

    SciTech Connect

    Kutasov, I.M.

    1992-06-01

    This paper reports that a Fortran computer program has been developed to determine static formation temperatures (SFT) and geothermal gradient (GG). A minimum of input data (only two shut-in temperature logs) is required to obtain the values of SFT and GG. Modeling of primary oil production and designing enhanced oil recovery (EOR) projects requires knowing the undisturbed (static) reservoir temperature. Furthermore, the bottom hole circulating temperature (BHCT) is an important factor affecting a cement's thickening time, rheological properties, compressive strength, development, and set time. To estimate the values of BHCT, the geothermal gradient should be determined with accuracy. Recently we obtained an approximate analytical solution which describes the shut-in temperature behavior.

  15. Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)

    E-print Network

    Reisler, Hanna

    ) S. Hawkins, G. Kumi, S. Malyk, H. Reisler *, C. Wittig * Department of Chemistry, University.cplett.2005.01.049 * Corresponding authors. Fax: +213 746 4945 (C. Wittig). E-mail addresses: reisler@usc.edu (H. Reisler), wittig@usc.edu (C. Wittig). www.elsevier.com/locate/cplett Chemical Physics Letters 404

  16. Dimensionality changes in the solid phase at room temperature: 2D ? 1D ? 3D evolution induced by ammonia sorption-desorption on zinc phosphates.

    PubMed

    Amghouz, Zakariae; Ramajo, Beatriz; Khainakov, Sergei A; da Silva, Iván; Castro, Germán R; García, José R; García-Granda, Santiago

    2014-06-28

    Two-dimensional zinc phosphate NH4Zn2(PO4)(HPO4) (), via ammonia vapor interaction at room temperature, transforms to a one-dimensional novel compound NH4Zn(NH3)PO4 (). By ammonia desorption (in air at room temperature) transforms to NH4ZnPO4 () with a well-known ABW-zeolitic topology. The crystal structure of was solved ab initio using synchrotron powder X-ray diffraction data (monoclinic, P21/a, a = 16.5227(2) Å, b = 6.21780(8) Å, c = 5.24317(6) Å, ? = 91.000(2)°, Z = 4). The structures of three compounds include extra-framework ammonium cations to the 4-fold coordinated zinc (ZnO4 tetrahedra for and , and ZnO3N tetrahedra for ) and phosphorus (PO4 tetrahedra) with bi-, mono- or three-dimensional linkages, respectively for , or . To our knowledge, the process described here constitutes the first example of dimensionality change in the solid phase promoted by a solid-gas interaction at room temperature in metal phosphates. PMID:24829098

  17. Effects of Varied pH, Growth Rate and Temperature using Controlled fermentation and Batch culture on Matrix Assisted Laser Desorption/Ionization Whole Cell Protein Fingerprints.

    SciTech Connect

    Wunschel, David S.; Hill, Eric A.; Mclean, Jeffrey S.; Jarman, Kristin H.; Gorby, Yuri A.; Valentine, Nancy B.; Wahl, Karen L.

    2005-09-01

    Rapid identification of microorganisms using matrix assisted laser desorption/ionization (MALDI) is a rapidly growing area of research due to the minimal sample preparation, speed of analysis and broad applicability of the technique. This approach relies on protein markers to identify microorganisms. Therefore, variations in culture conditions that affect protein expression may limit the ability of MALDI-MS to correctly identify an organism. We have expanded our efforts to investigate the effects of culture conditions on MALDI-MS protein signatures to examine the effects of pH, growth rate and temperature. Continuous cultures maintained in bioreactors were used to maintain specific growth rates and pH for E. coli HB 101. Despite measurable morphological differences between growth conditions, the MALDI-MS data associated each culture with the appropriate library entry (E. coli HB 101 generated using batch culture on a LB media), independent of pH or growth rate. The lone exception was for a biofilm sample collected from one of the reactors which had no appreciable degree of association with the correct library entry. Within the data set for planktonic organisms, variations in growth rate created the largest variation between fingerprints. The effect of varying growth temperature on Y. enterocolitica was also examined. While the anticipated effects on phenotype were observed, the MALDI-MS technique provided the proper identification.

  18. In?uence of temperature and atmosphere on polychlorinated dibenzo-p-dioxins and dibenzofurans desorption from waste incineration fly ash.

    PubMed

    Yang, Jie; Yan, Mi; Li, Xiaodong; Chen, Tong; Lu, Shengyong; Yan, Jianhua; Buekens, Alfons

    2015-01-01

    A fly ash sample was heated for 1?h to 200°C, 300°C and 400°C, in order to study the influence of temperature and gas phase composition on the removal of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from fly ash derived from municipal solid waste incineration. The tests were conducted by treating a fixed bed of fly ash both in an inert (nitrogen) and in a reducing (nitrogen+hydrogen) gas flow in a horizontal bench-scale quartz tubular reactor, heated by a surrounding tubular furnace. The results indicate that most of the PCDD/Fs in fly ash were removed by thermal treatment, especially when the temperature was higher than 300°C: the PCDD/Fs' removal efficiency attained up to 96%. PCDD/Fs dechlorination and destruction were much more important than PCDD/Fs desorption, under either inert or reducing atmosphere. At 200°C and 300°C, the experiments with reducing atmosphere yielded slightly better results than those in nitrogen; yet, this tendency was reversed at 400°C. In general, both treatment modes can fully meet the requirements regarding the concentration of dioxins in fly ash to be sent for landfill in China. PMID:25241904

  19. GaN CVD Reactions: Hydrogen and Ammonia Decomposition and the Desorption of Gallium

    SciTech Connect

    Bartram, Michael E.; Creighton, J. Randall

    1999-05-26

    Isotopic labeling experiments have revealed correlations between hydrogen reactions, Ga desorption, and ammonia decomposition in GaN CVD. Low energy electron diffraction (LEED) and temperature programmed desorption (TPD) were used to demonstrate that hydrogen atoms are available on the surface for reaction after exposing GaN(0001) to deuterium at elevated temperatures. Hydrogen reactions also lowered the temperature for Ga desorption significantly. Ammonia did not decompose on the surface before hydrogen exposure. However, after hydrogen reactions altered the surface, N15H3 did undergo both reversible and irreversible decomposition. This also resulted in the desorption of N2 of mixed isotopes below the onset of GaN sublimation, This suggests that the driving force of the high nitrogen-nitrogen bond strength (226 kcal/mol) can lead to the removal of nitrogen from the substrate when the surface is nitrogen rich. Overall, these findings indicate that hydrogen can influence G-aN CVD significantly, being a common factor in the reactivity of the surface, the desorption of Ga, and the decomposition of ammonia.

  20. Interfacial chemistry of a perfluoropolyether lubricant studied by X-ray photoelectron spectroscopy and temperature desorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Herrera-Fierro, Pilar; Jones, William R., Jr.; Pepper, Stephen V.

    1993-01-01

    The interfacial chemistry of Fomblin Z25, a commercial perfluoropolyether used as lubricant for space applications was studied with different metallic surfaces: 440C steel, gold, and aluminum. Thin layers of Fomblin Z25 were evaporated onto the oxide-free substrates, and the interfacial chemistry was studied using XPS and TDS. The reactions were induced by heating the substrate and by rubbing the substrate with a steel ball. Gold was found to be completely unreactive towards Fomblin at any temperature. Reaction at room temperature was observed only in the case of the aluminum substrate, the most reactive towards Fomblin Z25 of the substrates studied. It was necessary to heat the 440C steel substrate to 190 C to induce decomposition of the fluid. The degradation of the fluid was indicated by the formation of a debris layer at the interface. This debris layer, composed of inorganic and organic reaction products, when completely formed, passivated the surface from further attack to the Fromblin on top. The tribologically induced reactions on 440C steel formed a debris layer of similar chemical characteristics to the thermally induced layer. In all cases, the degradation reaction resulted in preferential consumption of the difluoroformyl carbon (-OCF2O-).

  1. Effect of Rh particle size on CO desorption from Rh/alumina model catalysts

    NASA Astrophysics Data System (ADS)

    Belton, David N.; Schmieg, Steven J.

    1988-08-01

    The adsorption of CO on small Rh particles on oxidized Al(100) was studied using temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). The desorption data for CO were obtained for two {Rh}/{Al 2O 3} samples as well as for Rh(111). The supported Rh model catalysts were prepared from thermal decomposition of [Rh(CO 2Cl] 2 on an oxidized Al(100) substrate. By varying the substrate temperature and the amount of deposited Rh, samples were prepared with average Rh particles sizes of 20 and 70 Å. TPD data from the 70 Å Rh particles were similar to that from Rh(111), with a major peak at 500 K and a shoulder at 400 K for a saturation CO exposure. TPD from the small particles was very different from Rh(111) and the larger particles, showing a single broad peak centered at 415 K. The data show a particle size effect for the desorption on CO from supported Rh. Redhead analysis of the data for first-order desorption gave an activation energy of 30 kcal/mol for all of the samples at low CO coverages. A more detailed analysis using peak widths and peak temperatures was also performed. These calculations gave a very low activation energy, 19.8 kcal/mol, and preexponential, 1×10 8{cm2}/{s} for the small particles. These very low values were interpreted to mean that multiple desorption states, mobile precursors, or coverage dependent activation energies were affecting the data from the small particles. Calculations of first-order desorption rates showed that desorption states different than those on Rh(111) are the dominant species on the small particles at high CO coverages.

  2. Temperature programmed decomposition of thorium nitrate pentahydrate

    NASA Astrophysics Data System (ADS)

    Dash, S.; Kamruddin, M.; Ajikumar, P. K.; Tyagi, A. K.; Raj, Baldev; Bera, Santanu; Narasimhan, S. V.

    2000-02-01

    Temperature programmed decomposition (TPD) of thorium nitrate pentahydrate has been studied using evolved gas analysis-mass spectrometry (EGA-MS) in the temperature range 300-1200 K. A thermogravimetric (TGA) investigation was also carried out in the same temperature range. Complexity of the TGA decomposition profile was resolved through use of EGA-MS data. The activation energies and pre-exponential factors were determined for various gas release stages from the fractional extent of decomposition plots. Residues left over after each decomposition stage were analysed using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD investigations revealed formation of a nanocrystalline thoria intermediate product, ultimately agglomerating to a microcrystalline phase. The XPS investigations indicated systematic alteration in the chemical environment around the thorium atom while the Th 4+ oxidation state remained unchanged. This was further corroborated from the analysis of shake-up satellites of Th (4f 5/2) spectra. The O/Th ratios for various intermediate products were also determined.

  3. Temperature programmed decomposition of uranyl nitrate hexahydrate

    NASA Astrophysics Data System (ADS)

    Dash, S.; Kamruddin, M.; Bera, Santanu; Ajikumar, P. K.; Tyagi, A. K.; Narasimhan, S. V.; Raj, Baldev

    1999-01-01

    Temperature programmed decomposition (TPD) of uranyl nitrate hexahydrate has been studied using evolved gas analysis mass spectrometry (EGA-MS) in the temperature range 300-1400 K. Thermogravimetric (TGA) investigations were performed in the temperature range 300-1100 K. An attempt has been made to resolve the complexity of decomposition behaviour through suitable comparison of TGA and EGA-MS data. Kinetic control regimes for various decomposition stages could be deduced from EGA-MS data. The corresponding activation energies and frequency factors were also evaluated. Kinetics based on random nucleation and diffusion was found to be rate controlling. The residue left over after each decomposition stage was analysed by XRD and XPS to determine structure and composition. The ultimate product was found to be a mixture of UO 3H 1.17 and U 3O 8: the former being a topotactic hydrogen spill over compound of UO 3. Complete conversion of this residue to U 3O 8 was noticed during ion beam exposure of the residue which was performed in the course of XPS investigations.

  4. Temperature programmed decomposition of thorium oxalate hexahydrate

    NASA Astrophysics Data System (ADS)

    Dash, S.; Krishnan, R.; Kamruddin, M.; Tyagi, A. K.; Raj, Baldev

    2001-06-01

    Temperature programmed decomposition (TPD) of thorium oxalate hexahydrate (TOH) was studied by evolved gas analysis-mass spectrometry (EGA-MS), thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). The microcrystalline solid exhibited sequential dehydration. The anhydrous compound yielded amorphous phase Th(CO 3) 2 upon CO release arising out of the bond cleavage. The Th(CO 3) 2 phase transformed to nano-crystalline thoria upon decomposition through an oxycarbonate intermediate. The mechanism underlying various conversion stages exhibited control by random nucleation, diffusion and phase boundary interface motion. From the fractional extent of decomposition data, Arrhenius factors like activation energy and pre-exponential factors were evaluated. Based on these studies, a chemical pathway is proposed for the entire decomposition process.

  5. THERMAL DESORPTION TREATMENT

    EPA Science Inventory

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

  6. Rapid screening of pharmaceutical drugs using thermal desorption - SALDI mass spectrometry

    NASA Astrophysics Data System (ADS)

    Grechnikov, A. A.; Kubasov, A. E.; Georgieva, V. B.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Alimpiev, S. S.

    2012-12-01

    A novel approach to the rapid screening of pharmaceutical drugs by surface assisted laser desorption-ionization (SALDI) mass spectrometry with the rotating ball interface coupled with temperature programmed thermal desorption has been developed. Analytes were thermally desorbed and deposited onto the surface of amorphous silicon substrate attached to the rotating ball. The ball was rotated and the deposited analytes were analyzed using SALDI. The effectiveness of coupling SALDI mass spectrometry with thermal desorption was evaluated by the direct and rapid analysis of tablets containing lidocaine, diphenhydramine and propranolol without any sample pretreatment. The overall duration of the screening procedure was 30÷40 sec. Real urine samples were studied for drug analysis. It is shown that with simple preparation steps, urine samples can be quantitatively analyzed using the proposed technique with the detection limits in the range of 0.2÷0.5 ng/ml.

  7. Evaluation of biochars by temperature programmed oxidation/mass spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar from the thermochemical conversion of biomass was evaluated by Temperature Programmed Oxidation (TPO) coupled with mass spectroscopy. This technique can be used to assess the oxidative reactivity of carbonaceous solids where higher temperature reactivity indicates greater structural order. ...

  8. Effects of varied pH, growth rate and temperature using controlled fermentation and batch culture on Matrix Assisted Laser Desorption\\/Ionization whole cell protein fingerprints

    Microsoft Academic Search

    David S. Wunschel; Eric A. Hill; Jeffrey S. McLean; Kristin H. Jarman; Yuri A. Gorby; Nancy B. Valentine; Karen L. Wahl

    2005-01-01

    Rapid identification of microorganisms using matrix assisted laser desorption\\/ionization (MALDI) is a rapidly growing area of research due to the minimal sample preparation, speed of analysis and broad applicability of the technique. This approach relies on expressed biochemical markers, often proteins, to identify microorganisms. Therefore, variations in culture conditions that affect protein expression may limit the ability of MALDI-MS to

  9. MatrixGuest Energy Transfer in Matrix-assisted Laser Desorption

    E-print Network

    Vertes, Akos

    indicates that in the case of 1500 K and 3000 K the desorption process is complete, whereas at 900 K and guest molecules depend on the initial matrix temperature jump. The initial matrix temperature of 900 K leads to incomplete desorption, whereas at 1500 K complete desorption and the formation of an energy

  10. Surface diffusion and desorption kinetics for perfluoro-n-butane on Ru(001)

    NASA Astrophysics Data System (ADS)

    Arena, M. V.; Westre, E. D.; George, S. M.

    1991-03-01

    The surface diffusion and desorption kinetics for perfluoro-n-butane on Ru(001) were examined using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The surface diffusion displayed Arrhenius behavior and was coverage independent. The surface diffusion parameters for perfluoro-n-butane on Ru(001) were Edif=2.9±0.3 kcal/mol and D0=5.9×10-2±0.2 cm2/s. The desorption parameters for perfluoro-n-butane on Ru(001) were Edes=13.8±0.6 kcal/mol and ?des=2.8×1021±0.1 s-1. In comparison, the surface diffusion parameters for n-butane on Ru(001) were Edif=3.5±0.2 kcal/mol and D0=1.4×10-1±0.2 cm2/s. The desorption parameters for n-butane on Ru(001) were Edes=11.9±0.5 kcal/mol and ?des=3.6×1015±0.1 s-1. The corrugation ratio, defined as ??Edif/Edes, was determined to be ?=0.21 for perfluoro-n-butane on Ru(001). This corrugation ratio was substantially different than the corrugation ratio of ??0.30 measured for n-butane and various other n-alkanes, cycloalkanes and branched alkanes on Ru(001). The comparison between perfluoro-n-butane and the other alkanes indicates that fluorination lowers the surface corrugation ratio on Ru(001). Likewise, fluorination significantly increases the preexponential for desorption from Ru(001). This study illustrates the magnitude of substituent effects on surface diffusion and desorption kinetics for a physisorbed molecule on a single-crystal metal surface.

  11. Desorption of water from distinct step types on a curved silver crystal.

    PubMed

    Janlamool, Jakrapan; Bashlakov, Dima; Berg, Otto; Praserthdam, Piyasan; Jongsomjit, Bunjerd; Juurlink, Ludo B F

    2014-01-01

    We have investigated the adsorption of H2O onto the A and B type steps on an Ag single crystal by temperature programmed desorption. For this study, we have used a curved crystal exposing a continuous range of surface structures ranging from [5(111) × (100)] via (111) to [5(111) × (110)]. LEED and STM studies verify that the curvature of our sample results predominantly from monoatomic steps. The sample thus provides a continuous array of step densities for both step types. Desorption probed by spatially-resolved TPD of multilayers of H2O shows no dependence on the exact substrate structure and thus confirms the absence of thermal gradients during temperature ramps. In the submonolayer regime, we observe a small and linear dependence of the desorption temperature on the A and B step density. We argue that such small differences are only observable by means of a single curved crystal, which thus establishes new experimental benchmarks for theoretical calculation of chemically accurate binding energies. We propose an origin of the observed behavior based on a "two state" desorption model. PMID:25068782

  12. Molecular desorption of a nonevaporable getter St 707 irradiated at room temperature with synchrotron radiation of 194 eV critical photon energy

    NASA Astrophysics Data System (ADS)

    Le Pimpec, F.; Gröbner, O.; Laurent, J. M.

    2003-05-01

    Photon stimulated molecular desorption from a nonevaporable getter (NEG) St 707® (SAES Getters™) surface after conditioning and after saturation with isotopic carbon monoxide [cf. nomenclature in Handbook of Chemistry and Physics, 74th edition, edited by D. R. Lide (CRC Press, Boca Raton, 1994)] 13C18O, has been studied on a dedicated beamline at the EPA ring at CERN. The synchrotron radiation of 194 eV critical energy and with an average photon intensity of ~1×1017 photons s-1 was impinging on the sample at perpendicular incidence. It is found that the desorption yields ? (molecules/photon) of the characteristic gases in an UHV system (hydrogen, methane, carbon monoxide, and carbon dioxide) for a freshly activated NEG and for a NEG fully saturated with 13C18O are lower than that of 300 °C baked stainless steel.

  13. THERMAL DESORPTION...NOW YOU'RE COOKIN'

    EPA Science Inventory

    Thermal desorption includes a number of ex situ processes that use either direct or indirect heat exchange to heat a waste material to volatilize organic materials. hermal desorption systems typically operate at soil treatment temperatures in the range of 400 to 600 degrees F to ...

  14. High-Temperature Combustion Gas Turbine Program. [Operation at 2600°F firing temperature

    Microsoft Academic Search

    Rose

    1980-01-01

    This is the final report of the High-Temperature Combustion Gas Turbine Program conducted by the General Electric Company with the New York State Energy Research and Development Authority. This program was implemented to support the development of high-temperature gas turbines in New York State. The overall objective of this work is to enhance the ongoing national effort to develop a

  15. Silicone rod extraction followed by liquid desorption-large volume injection-programmable temperature vaporiser-gas chromatography-mass spectrometry for trace analysis of priority organic pollutants in environmental water samples.

    PubMed

    Delgado, Alejandra; Posada-Ureta, Oscar; Olivares, Maitane; Vallejo, Asier; Etxebarria, Nestor

    2013-12-15

    In this study a priority organic pollutants usually found in environmental water samples were considered to accomplish two extraction and analysis approaches. Among those compounds organochlorine compounds, pesticides, phthalates, phenols and residues of pharmaceutical and personal care products were included. The extraction and analysis steps were based on silicone rod extraction (SR) followed by liquid desorption in combination with large volume injection-programmable temperature vaporiser (LVI-PTV) and gas chromatography-mass spectrometry (GC-MS). Variables affecting the analytical response as a function of the programmable temperature vaporiser (PTV) parameters were firstly optimised following an experimental design approach. The SR extraction and desorption conditions were assessed afterwards, including matrix modification, time extraction, and stripping solvent composition. Subsequently, the possibility of performing membrane enclosed sorptive coating extraction (MESCO) as a modified extraction approach was also evaluated. The optimised method showed low method detection limits (3-35 ng L(-1)), acceptable accuracy (78-114%) and precision values (<13%) for most of the studied analytes regardless of the aqueous matrix. Finally, the developed approach was successfully applied to the determination of target analytes in aqueous environmental matrices including estuarine and wastewater samples. PMID:24209370

  16. THERMAL DESORPTION OF PETROLEUM CONTAMINATED SOILS

    EPA Science Inventory

    The U.S. Environmental Protection Agency recently funded a study which addresses the treatment of soils contaminated by petroleum hydrocarbons using low temperature thermal desorption (LTTD). he proposed paper will summarize some of the results of that study. TTD has become a maj...

  17. Computational simulation characteristics desorption in TPS aggregates

    NASA Astrophysics Data System (ADS)

    Goldaev, Sergey; Khushvaktov, Alisher

    2014-08-01

    The article describes the modified model of desorption in a continuously operating apparatus in fluidized bed, which allows for a refined timing warm adsorbent particles of spherical shape at a flow of hot air to equalize the temperature along the radius of granules and assess relevant energy costs.

  18. Moisture Absorption and Desorption of Composite Materials

    Microsoft Academic Search

    Chi-Hung Shen; George S. Springer

    1976-01-01

    Expressions are presented for the moisture distribution and the mois ture content as a function of time of one dimensional homogeneous and composite materials exposed either on one side or on both sides to humid air or to water. The results apply during both moisture absorption and desorption when the moisture content and the temperature of the environ ment are

  19. Temperature lowering program for homogeneous doping in flux growth

    NASA Astrophysics Data System (ADS)

    Qiwei, Wang; Shouquan, Jia

    1989-10-01

    Based on the mass conservation law and the Burton-Prim-Slichter equation, the temperature program for homogeneous doping in flux growth by slow cooling was derived. The effect of various factors, such as initial supersaturation, solution volume, growth kinetic coefficient and degree of mixing in the solution on growth rate, crystal size and temperature program is discussed in detail. Theoretical analysis shows that there is a critical crystal size above which homogeneous doping is impossible.

  20. FINAL REPORT. HIGH TEMPERATURE CONDENSED PHASE MASS SPECTROMETRIC ANALYSIS PROGRAM

    EPA Science Inventory

    This project was funded by the EM Science Program for the development of an integrated mass spectrometric analysis system capable of analyzing materials from room up to high temperatures, with the practical upper temperature limit to be experimentally determined. A primary object...

  1. Progress in BNL High-Temperature Hydrogen Combustion Research Program

    Microsoft Academic Search

    G. Ciccarelli; T. Ginsberg; J. Boccio; J. Curtiss; C. Economos; J. Jahelka; K. Sato

    1992-01-01

    The objectives of the BNL High-Temperature Hydrogen Combustion Research Program are discussed. The experimental facilities are described and two sets of preliminary experiments are presented. Chemical reaction time experiments have been performed to determine the length of time reactive mixtures of interest can be kept at temperature before reaction in the absence of ignition sources consumes the reactants. Preliminary observations

  2. The desorption purge time and thermal stability of 1,3-butadiene in a charcoal sampling tube

    E-print Network

    Xie, Jianghua

    1997-01-01

    desorption process. Two major variables, which affect the desorption purge time when organic compounds are desorbed from a charcoal tube by thermal means, are the temperature and carrier gas flow rate. In this study, a modified gas chromatograph apparatus...

  3. Fundamental data on the desorption of pure interstellar ices

    NASA Astrophysics Data System (ADS)

    Brown, Wendy A.; Bolina, Amandeep S.

    2007-01-01

    The desorption of molecular ices from grain surfaces is important in a number of astrophysical environments including dense molecular clouds, cometary nuclei and the surfaces and atmospheres of some planets. With this in mind, we have performed a detailed investigation of the desorption of pure water, pure methanol and pure ammonia ices from a model dust-grain surface. We have used these results to determine the desorption energy, order of desorption and the pre-exponential factor for the desorption of these molecular ices from our model surface. We find good agreement between our desorption energies and those determined previously; however, our values for the desorption orders, and hence also the pre-exponential factors, are different to those reported previously. The kinetic parameters derived from our data have been used to model desorption on time-scales relevant to astrophysical processes and to calculate molecular residence times, given in terms of population half-life as a function of temperature. These results show the importance of laboratory data for the understanding of astronomical situations whereby icy mantles are warmed by nearby stars and by other dynamical events.

  4. Desorption of hot molecules from photon irradiated interstellar ices

    E-print Network

    J. D. Thrower; D. J. Burke; M. P. Collings; A. Dawes; P. J. Holtom; F. Jamme; P. Kendall; W. A. Brown; I. P. Clark; H. J. Fraser; M. R. S. McCoustra; N. J. Mason; A. W. Parker

    2007-08-28

    We present experimental measurements of photodesorption from ices of astrophysical relevance. Layers of benzene and water ice were irradiated with a laser tuned to an electronic transition in the benzene molecule. The translational energy of desorbed molecules was measured by time-of-flight (ToF) mass spectrometry. Three distinct photodesorption processes were identified - a direct adsorbate-mediated desorption producing benzene molecules with a translational temperature of around 1200 K, an indirect adsorbate-mediated desorption resulting in water molecules with a translational temperature of around 450 K, and a substrate-mediated desorption of both benzene and water producing molecules with translational temperatures of around 530 K and 450 K respectively. The translational temperature of each population of desorbed molecules is well above the temperature of the ice matrix. The implications for gas-phase chemistry in the interstellar medium are discussed.

  5. A metal-organic framework as a chemical guide to control hydrogen desorption pathways of ammonia borane.

    PubMed

    Jeong, Hyung Mo; Shin, Weon Ho; Park, Jung Hyo; Choi, Jung Hoon; Kang, Jeung Ku

    2014-06-21

    We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption. PMID:24842695

  6. Hydrogen absorption and desorption by the Li-Al-N-H system.

    PubMed

    Kojima, Yoshitsugu; Matsumoto, Mitsuru; Kawai, Yasuaki; Haga, Tetsuya; Ohba, Nobuko; Miwa, Kazutoshi; Towata, Shin-ichi; Nakamori, Yuko; Orimo, Shin-ichi

    2006-05-18

    Lithium hexahydridoaluminate Li(3)AlH(6) and lithium amide LiNH(2) with 1:2 molar ratio were mechanically milled, yielding a Li-Al-N-H system. LiNH(2) destabilized Li(3)AlH(6) during the dehydrogenation process of Li(3)AlH(6), because the dehydrogenation starting temperature of the Li-Al-N-H system was lower than that of Li(3)AlH(6). Temperature-programmed desorption scans of the Li-Al-N-H system indicated that a large amount of hydrogen (6.9 wt %) can be released between 370 and 773 K. After initial H(2) desorption, the H(2) absorption and the desorption capacities of the Li-Al-N-H system with a nano-Ni catalyst exhibited 3-4 wt % at 10-0.004 MPa and 473-573 K, while the capacities of the system without the catalyst were 1-2 wt %. The remarkably increased capacity was due to the fact that the kinetics was improved by addition of the nano-Ni catalyst. PMID:16686512

  7. Thermal Desorption and Infrared Studies of Plasma-Enhanced Chemical Vapor Deposited SiO Films with Tetraethylorthosilicate

    Microsoft Academic Search

    Norio Hirashita; Shunichi Tokitoh; Hidetsugu Uchida

    1993-01-01

    Thermal desorption and Fourier transform infrared spectroscopies were used to study plasma-enhanced chemical vapor deposited SiO films from tetraethylorthosilicate. Significant water desorption and concomitant structural changes were observed for the films during subsequent heat treatments between 100 and 700°C. The films exhibited three distinct water desorption states. The desorption temperatures were approximately 100-200°C for the first state, 150-300°C for the

  8. Low-temperature copper etching via reactions with Cl2 and PEt3 under ultrahigh vacuum conditions

    Microsoft Academic Search

    J. Farkas; K.-M. Chi; M. J. Hampden-Smith; T. T. Kodas; L. H. Dubois

    1993-01-01

    Reflection–absorption infrared spectroscopy, Auger electron spectroscopy (AES), temperature programmed desorption, and reactive scattering were used to investigate the adsorption and desorption behavior of PEt3 on copper and chlorinated copper surfaces under ultrahigh vacuum conditions. No reaction was observed between PEt3 and clean Cu(100) or between PEt3 and a c(2×2)–Cl overlayer. At temperatures above 320 K, PEt3 reacted rapidly with a

  9. NASA's high-temperature engine materials program for civil aeronautics

    SciTech Connect

    Gray, H.R.; Ginty, C.A. (NASA Lewis Research Center, Cleveland, OH (US))

    1992-05-01

    This paper discusses the Advanced High Temperature Engine Materials Technology Program (HTEMP) of NASA which is directed toward enabling the development of 22st-centruy civil aeronautics propulsion systems by generating he technology necessary for revolutionary advances in structural materials and analysis. Major consideration is being given to propulsion systems that are: Friendly to the environment in terms of minimized pollution and noise; Economical with regard to reduced fuel consumption per passenger mile, lower direct operating costs, longer life, and improved system reliability. To achieve such advances, developments in high-temperature materials are considered key.

  10. Air stability of low-temperature dehydrogenation of Pd-decorated Mg blades.

    PubMed

    Liu, Yu; Wang, Gwo-Ching

    2012-01-20

    We demonstrated that Pd-decorated Mg blades are air-stable for hydrogen storage with a low desorption temperature of 373 K. Pd-catalyst-decorated Mg blades were prepared by 64° oblique incident angle thermal deposition on a rotatable substrate with the rotation axis perpendicular to the substrate. The hydrogen desorption from Pd-decorated Mg blades was performed and recorded by temperature-programmed desorption (TPD) for repeated hydrogenation–dehydrogenation cycles. The near-surface structural and compositional changes were characterized in situ by reflection high energy electron diffraction (RHEED). The Mg blades were intentionally exposed to air at elevated temperatures (333 or 358 K) between certain cycles. It was found that the degradation of the storage capacity was affected weakly by the air exposure at moderate temperatures. The kinetics of the hydrogen desorption was sensitive to air exposure but recoverable through a replenishment of fresh catalyst Pd on the surface of the oxidized Mg blades. PMID:22166731

  11. USGS Coal Desorption Equipment and a Spreadsheet for Analysis of Lost and Total Gas from Canister Desorption Measurements

    USGS Publications Warehouse

    Barker, Charles E.; Dallegge, Todd A.; Clark, Arthur C.

    2002-01-01

    We have updated a simple polyvinyl chloride plastic canister design by adding internal headspace temperature measurement, and redesigned it so it is made with mostly off-the-shelf components for ease of construction. Using self-closing quick connects, this basic canister is mated to a zero-head manometer to make a simple coalbed methane desorption system that is easily transported in small aircraft to remote localities. This equipment is used to gather timed measurements of pressure, volume and temperature data that are corrected to standard pressure and temperature (STP) and graphically analyzed using an Excel(tm)-based spreadsheet. Used together these elements form an effective, practical canister desorption method.

  12. Laser desorption fast gas chromatography–Mass spectrometry in supersonic molecular beams

    Microsoft Academic Search

    Tzvi Shahar; Shai Dagan; Aviv Amirav

    1998-01-01

    A novel method for fast analysis is presented. It is based on laser desorption injection followed by fast gas chromatography-mass\\u000a spectrometry (GC-MS) in supersonic molecular beams. The sample was placed in an open air or purged laser desorption compartment,\\u000a held at atmospheric pressure and near room temperature conditions. Desorption was performed with a XeCl Excimer pulsed laser\\u000a with pulse energy

  13. Desorption of Mercury(II) on Kaolinite in the Presence of Oxalate or Cysteine

    SciTech Connect

    Senevirathna, W. U. [Tennessee Technological University; Zhang, Hong [ORNL; Gu, Baohua [ORNL

    2011-01-01

    Sorption and desorption of Hg(II) on clay minerals can impact the biogeochemical cycle and bio- uptake of Hg in aquatic systems. We studied the desorption of Hg(II) on kaolinite in the presence of oxalate or cysteine, representing the ligands with carboxylic and thiol groups of different affinities for Hg(II). The effects of pH (3, 5, 7), ligand concentration (0.25, 1.0 mM), and temperature (15, 25, 35 C) on the Hg(II) desorption were investigated through desorption kinetics. Our study showed that the Hg(II) desorption was pH-dependant. In the absence of any organic ligand, >90% of the previously adsorbed Hg(II) desorbed at pH 3 within 2 h, compared to <10% at pH 7. Similar results were observed in the presence of oxalate, showing that it hardly affected the Hg(II) desorption. Cysteine inhibited the Hg(II) desorption significantly at all the pH tested, especially in the first 80 min with the desorption less than 20%, but it appeared to enhance the Hg(II) desorption afterwards. The effect of ligand concentration on the Hg(II) desorption was small, especially in the presence of oxalate. The effect of temperature on the desorption was nearly insignificant. The effect of the organic acids on the Hg(II) sorption and desorption is explained by the formation of the ternary surface complexes involving the mineral, ligand, and Hg(II). The competition for Hg(II) between the cysteine molecules adsorbed on the particles and in the solution probably can also affect the Hg(II) desorption.

  14. n-Alkanes on MgO(100). I: Coverage-Dependent Desorption Kinetics of n-Butane

    SciTech Connect

    Tait, Steven L.; Dohnalek, Zdenek; Campbell, C T.; Kay, Bruce D.

    2005-04-22

    High quality temperature programmed desorption (TPD) measurements of n-butane from MgO(100) have been made for a large number of initial butane coverages (0-3.70 ML) and a wide range of heating ramp rates (0.3-10 K/s). We present a TPD analysis technique which allows the coverage-dependent desorption energy to be accurately determined by mathematical inversion of a TPD spectrum, assuming only that the prefactor is coverage-independent. A variational method is used to determine the prefactor that minimizes the difference between a set of simulated TPD spectra and corresponding experimental data. The best fit for butane desorption from MgO is obtained with a prefactor of 1015.7?1.6 s-1. The desorption energy is 34.9?3.4 kJ/mol at 0.5 ML coverage, and varies with coverage. Simulations based on these results can accurately reproduce TPD experiments for submonolayer initial coverages over a wide range of heating ramp rates (0.3-10 K/s). Advantages and limitations of this method are discussed.

  15. Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on Forsterite, Mg2SiO4(011)

    SciTech Connect

    Smith, R. Scott; Li, Zhenjun; Dohnalek, Zdenek; Kay, Bruce D.

    2014-12-18

    We have examined the adsorbate-substrate interaction kinetics of CO2 and H2O on a natural forsterite crystal surface, Mg2SiO4(011), with 10-15% of substitutional Fe2+. We use temperature programmed desorption (TPD) and molecular beam techniques to determine the adsorption, desorption, and displacement kinetics for H2O and CO2. Neither CO2 nor H2O has distinct sub-monolayer desorption peaks but instead both have a broad continuous desorption feature that evolve smoothly into multilayer desorption. Inversion of the monolayer coverage spectra for both molecules reveals that the corresponding binding energies for H2O are greater than that for CO2 on all sites. The relative strength of these interactions is the dominant factor in the competitive adsorption/displacement kinetics. In experiments where the two adsorbates are co-dosed, H2O always binds to the highest energy binding sites available and displaces CO2. The onset of CO2 displacement by H2O occurs between 65 and 75 K.

  16. Desorption of hydrogen trapped in carbon and graphite

    NASA Astrophysics Data System (ADS)

    Atsumi, H.; Takemura, Y.; Miyabe, T.; Konishi, T.; Tanabe, T.; Shikama, T.

    2013-11-01

    Thermal desorption behavior of deuterium (D2) from isotropic graphites and a carbon fiber carbon composite (CFC) charged with D2 gas has been investigated to obtain information concerning hydrogen recycling and tritium inventory in fusion experimental devices as well as a futuristic fusion reactor. After thermal desorption experiments were conducted at temperatures up to 1740 K, a desorption peak at approximately 1600 K (peak 4) was discovered. This is in addition to the previously known peak at approximately 1300 K (peak 3). Peak 3 can be attributed to the release of deuterium controlled by the diffusion process in a graphite filler grain and peak 4 can be attributed to the detrapping of deuterium released from an interstitial cluster loop edge site. Activation energies of peaks 3 and 4 are estimated to be 3.48 and 6.93 eV, respectively. TDS spectra of D2 from graphite and CFCs had previously not been thoroughly investigated. A desorption peak at approximately 1600 K was discovered in the TDS spectra for all samples heated with a linear ramp rate of 0.1 K/s. For an isotropic graphite, ISO-880U, four desorption peaks were recognized in the TDS spectra at approximately 660 K, 900 K, 1300 K, and 1600 K. These peaks were named as peaks 1, 2, 3, and 4 in order of increasing temperature. Major desorption peaks (i.e., peaks 3 and 4) were analyzed and discussed in detail. The temperature of peak 3 was dependent on the size of a graphite filler grain. The desorption process is suggested to be controlled by deuterium diffusion within the filler grain with a strong influence of trapping sites, where the migration takes place as a sequence of detrapping and retrapping. The desorption for peak 4 can be ascribed to the detrapping reaction from an interstitial cluster loop edge site. Activation energies were estimated from the peak shift by varying the heating rate of TDS to be 3.48 and 6.93 eV for peaks 3 and 4, respectively. Theoretical desorption curves for peaks 3 and 4 with the above mentioned activation energies were narrower than those for the experimental desorption curve. The observed peak broadening can be attributed to the effects of grain size and activation energy distributions.

  17. High temperature static strain gage alloy development program

    NASA Technical Reports Server (NTRS)

    Hulse, C. O.; Bailey, R. S.; Lemkey, F. D.

    1985-01-01

    The literature, applicable theory and finally an experimental program were used to identify new candidate alloy systems for use as the electrical resistance elements in static strain gages up to 1250K. The program goals were 50 hours of use in the environment of a test stand gas turbine engine with measurement accuracies equal to or better than 10 percent of full scale for strains up to + or - 2000 microstrain. As part of this effort, a computerized electrical resistance measurement system was constructed for use at temperatures between 300K and 1250K and heating and cooling rates of 250K/min and 10K/min. The two best alloys were an iron-chromium-aluminum alloy and a palladium base alloy. Although significant progress was made, it was concluded that a considerable additional effort would be needed to fully optimize and evaluate these candidate systems.

  18. Ion Desorption Stability in Superconducting High Energy Physics Proton Colliders

    SciTech Connect

    Turner, W.C.

    1995-05-29

    In this paper we extend our previous analysis of cold beam tube vacuum in a superconducting proton collider to include ion desorption in addition to thermal desorption and synchrotron radiation induced photodesorption. The new ion desorption terms introduce the possibility of vacuum instability. This is similar to the classical room temperature case but now modified by the inclusion of ion desorption coefficients for cryosorbed (physisorbed) molecules which can greatly exceed the coefficients for tightly bound molecules. The sojourn time concept for physisorbed H{sub 2} is generalized to include photodesorption and ion desorption as well as the usually considered thermal desorption. The ion desorption rate is density dependent and divergent so at the onset of instability the sojourn time goes to zero. Experimental data are used to evaluate the H{sub 2} sojourn time for the conditions of the Large Hadron Collider (LHC) and the situation is found to be stable. The sojourn time is dominated by photodesorption for surface density s(H{sub 2}) less than a monolayer and by thermal deposition for s(H{sub 2}) greater than a monolayer. For a few percent of a monolayer, characteristic of a beam screen, the photodesorption rate exceeds ion desorption rate by more than two orders of magnitude. The photodesorption rate corresponds to a sojourn time of approximately 100 sec. The paper next turns to the evaluation of stability margins and inclusion of gases heavier than H{sub 2} (CO, CO{sub 2} and CH{sub 4}), where ion desorption introduces coupling between molecular species. Stability conditions are worked out for a simple cold beam tube, a cold beam tube pumped from the ends and a cold beam tube with a co-axial perforated beam screen. In each case a simple inequality for stability of a single component is replaced by a determinant that must be greater than zero for a gas mixture. The connection with the general theory of feedback stability is made and it is shown that the gains of the diagonal uncoupled feedback loops are first order in the ion desorption coefficients whereas the gains of the off diagonal coupled feedback loops are second and higher order. For this reason it turns out that in practical cases stability is dominated by the uncoupled diagonal elements and the inverse of the largest first order closed loop gain is a useful estimate of the margin of stability. In contrast to the case of a simple cold beam tube, the stability condition for a beam screen does not contain the desorption coefficient for physisorbed molecules, even when the screen temperature is low enough that there is a finite surface density of them on the screen surface. Consequently there does not appear to be any particular advantage to operating the beam screen at high enough temperature to avoid physisorption. Numerical estimates of ion desorption stability are given for a number of cases relevant to LHC and all of the ones likely to be encountered were found to be stable. The most important case, a I % transparency beam screen at {approx}4.2 K, was found to have a stability safety margin of approximately thirty determined by ion desorption of CO. Ion desorption of H{sub 2} is about a factor of eighty less stringent than CO. For these estimates the beam tube surface was assumed to be solvent cleaned but otherwise untreated, for example by a very high temperature vacuum bakeout or by glow discharge cleaning.

  19. Water Adsorption, Desorption, and Clustering on FeO(111)

    SciTech Connect

    Daschbach, John L.; Dohnalek, Zdenek; Liu, Shurong; Smith, R. Scott; Kay, Bruce D.

    2005-05-26

    The adsorption of water on FeO(111) is investigated using temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS). Well-ordered 2 ML thick FeO(111) films are grown epitaxially on a Pt(111) substrate. Water adsorbs molecularly on FeO(111) and desorbs with a well resolved monolayer peak. IRAS measurements as a function of coverage are performed for water deposited at 30 and 135 K. For all coverages (0.2 ML and greater) the adsorbed water exhibits significant hydrogen bonding. Differences in IRAS spectra for water adsorbed at 30 and 135 K are subtle but suggest that water adsorbed at 135 K is well ordered. Monolayer nitrogen TPD spectra from water covered FeO(111) surfaces are used to investigate the clustering of the water as a function of deposition or annealing temperature. Temperature dependent water overlayer structures result from differences in water diffusion rates on bare FeO(111) and on water adsorbed on FeO(111). Features in the nitrogen TPD spectra allow the monolayer wetting and 2-dimensional (2D) ordering of water on FeO(111) to be followed. Voids in a partially disordered first water layer exist for water deposited below 120 K and ordered 2D islands are found when depositing water above 120 K.

  20. Shell/METC high temperature high pressure filtration program

    SciTech Connect

    Salter, J.A. [Shell Synthetic Fuels Inc., Houston, TX (United States); Rockey, J.M. [Dept. of Energy, Morgantown, WV (United States). Morgantown Energy Technology Center

    1995-12-31

    The purpose of this paper is to present the program objectives and non-proprietary results of the high temperature, high pressure filtration work done under the Shell/METC Cooperative Research and Development Agreement (CRADA) 93-011. The primary purpose of this CRADA was to collect data relevant to the design and operation of dry particulate solids filters employing rigid ceramic (silicon carbide) filter elements in a gasifying environment at conditions of commercial interest; e.g., temperatures up to 1,100 F and system pressures between 300 and 350 psia. Shell provided the ceramic filter elements and evaluated the exposed filter elements. METC installed the filter elements and operated their 10-inch Fluid Bed Gasification and Cleanup facility as required for their Hot Gas Clean-up Test Program. Filter elements were removed from service after approximately 254, 525 and 868 hours of on-line operation. The exposed filter elements were analyzed and compared to an unexposed element with respect to changes in physical property.

  1. Continuum models of crystal growth from atomic beams with and without desorption

    Microsoft Academic Search

    J. Villain

    1991-01-01

    Continuum equations appropriate to describe crystal growth from atom beams are derived in various cases. When desorption is important, the growth is described on very long lengthscales by the Kardar-Parisi-Zhang equation, but should be corrected for shorter lengthscales where surface diffusion is the dominant mechanism. In the absence of desorption, an important effect at sufficiently low temperature comes from the

  2. Ga assisted oxide desorption on GaAs(0 0 1) studied by scanning tunnelling microscopy

    Microsoft Academic Search

    F. Bastiman; J. C. Lin; A. G. Cullis; R. Hogg; M. Skolnick

    2010-01-01

    Native oxide removal on GaAs wafers under conventional thermal desorption causes severe surface degradation. Recently a new method of Ga assisted oxide removal has reported improved initial surface conditions. A precise dosing of Ga is required to optimise the oxide removal, however the effects of alternate temperatures on the desorption process effects the reaction kinetics. By using selected bias imaging,

  3. Progress in BNL High-Temperature Hydrogen Combustion Research Program

    SciTech Connect

    Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Curtiss, J.; Economos, C.; Jahelka, J.; Sato, K.

    1992-01-01

    The objectives of the BNL High-Temperature Hydrogen Combustion Research Program are discussed. The experimental facilities are described and two sets of preliminary experiments are presented. Chemical reaction time experiments have been performed to determine the length of time reactive mixtures of interest can be kept at temperature before reaction in the absence of ignition sources consumes the reactants. Preliminary observations are presented for temperatures in the range 588K--700K. Detonation experiments are described in which detonation cell width is measured as a measure of mixture sensitivity to detonation. Preliminary experiments are described which are being carried out to establish data reproducibility with previous measurements in the literature and to test out and refine experimental methods. Intensive studies of hydrogen combustion phenomena were carried out during the 1980s. Much of this effort was driven by issues related to nuclear reactor safety. The high-speed'' combustion phenomena of flame acceleration, deflagration-to-detonation transition, direct initiation of detonation, detonation propagation, limits of detonation in tubes and channels, transmission of detonations from confined to unconfined geometry and other related phenomena were studied using a variety of gaseous fuel-oxidant systems, including hydrogen-steam-air systems of interest in reactor safety studies. Several reviews are available which document this work [Lee, 1989; Berman, 1986].

  4. Progress in BNL High-Temperature Hydrogen Combustion Research Program

    SciTech Connect

    Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Curtiss, J.; Economos, C.; Jahelka, J.; Sato, K.

    1992-12-31

    The objectives of the BNL High-Temperature Hydrogen Combustion Research Program are discussed. The experimental facilities are described and two sets of preliminary experiments are presented. Chemical reaction time experiments have been performed to determine the length of time reactive mixtures of interest can be kept at temperature before reaction in the absence of ignition sources consumes the reactants. Preliminary observations are presented for temperatures in the range 588K--700K. Detonation experiments are described in which detonation cell width is measured as a measure of mixture sensitivity to detonation. Preliminary experiments are described which are being carried out to establish data reproducibility with previous measurements in the literature and to test out and refine experimental methods. Intensive studies of hydrogen combustion phenomena were carried out during the 1980s. Much of this effort was driven by issues related to nuclear reactor safety. The ``high-speed`` combustion phenomena of flame acceleration, deflagration-to-detonation transition, direct initiation of detonation, detonation propagation, limits of detonation in tubes and channels, transmission of detonations from confined to unconfined geometry and other related phenomena were studied using a variety of gaseous fuel-oxidant systems, including hydrogen-steam-air systems of interest in reactor safety studies. Several reviews are available which document this work [Lee, 1989; Berman, 1986].

  5. Microstructure and thermal desorption of deuterium in heavy-ion-irradiated pure tungsten

    NASA Astrophysics Data System (ADS)

    Watanabe, Hideo; Futagami, Naoki; Naitou, Shiori; Yoshida, Naoaki

    2014-12-01

    To understand the fundamental processes of deuterium retention and desorption of irradiated plasma facing materials, thermal desorption of deuterium in pure W with and without ion irradiation up to 2 dpa by 2.4 MeV Cu2+ have been investigated. After the ion irradiation at room temperature, high density of small interstitial typed dislocation loops and also nano-voids due to cascade collisions were detected by TEM observation. Thermal desorption of spectra of D showed that fine vacancy clusters are formed even at low fluence and at room temperature irradiation, these defects act as the strong trapping center of deuterium in the temperature range of 660-900 K.

  6. Atomic Oxygen Desorption from an Amorphous Silicate Surface

    NASA Astrophysics Data System (ADS)

    He, Jiao; Vidali, Gianfranco

    2014-06-01

    Oxygen is the third most abundant element in space. How oxygen-containing molecules form in space, and whether they form through gas-phase or grain-surface reactions, depends largely on the availability of atomic oxygen in gas-phase versus on surfaces of dust grains. The relative abundance of O in gas-phase versus on grain surfaces is determined by the residence time, or equivalently, desorption energy, of atomic oxygen on grain surfaces. Though important in astrochemical modeling, experimental investigations of atomic oxygen desorption from grain surfaces are lacking in the literature. In most astrochemical models, the O desorption energy value has been taken to be 800 K, which is a guessed value without experimental support. Based on this value, the predicted molecular oxygen abundance in space is at least 2 orders of magnitude higher than what space observations have found. This long running discrepancy of molecular oxygen abundance could be resolved if the O desorption energy is twice as the widely used value (Melnick, G., Tolls, V., et al. 2012, Astrophys. J., 752, 26). We performed TPD (thermal programmed desorption) experiments to study the ozone formation process via O+O2 on an amorphous silicate surface that emulates interstellar conditions. A rate equation model was used to characterize the surface kinetics of both atomic and molecular oxygen. The O desorption energy was extracted from rate equation simulations that best fit the TPD data. The value was found to be 1764±232 K, which agrees with what Melnick et al. proposed. We suggest that the newly found value for the O desorption energy should be used in astrochemical modeling. This work is supported by NSF, Astronomy & Astrophysics Division (Grants No. 0908108 and 1311958), and NASA (Grant No. NNX12AF38G). We thank Dr. J.Brucato of the Astrophysical Observatory of Arcetri for providing the samples used in these experiments.

  7. Characterization of nanoporous materials from adsorption and desorption isotherms

    Microsoft Academic Search

    Peter I. Ravikovitch; Alexander V. Neimark

    2001-01-01

    We present a consistent method for calculation of pore size distributions in nanoporous materials from adsorption and desorption isotherms, which form the hysteresis loop H1 by the IUPAC classification. The method is based on the nonlocal density functional theory (NLDFT) of capillary condensation hysteresis in cylindrical pores. It is implemented for the nitrogen and argon sorption at their boiling temperatures.

  8. Desorption isotherm and heat pump drying kinetics of peas

    Microsoft Academic Search

    M. Shafiur Rahman; Conrad O. Perera; Caroline Thebaud

    1997-01-01

    Moisture desorption isotherms and thin layer drying kinetices of peas in a laboratory pilot heat pump dryer were measured and modeled. A mesh bottom tray was used and air flow was parallel to the two faces of the thin layer. Air drying temperature, and relative humidity were varied from 25 to 65 °C and 0.20 to 0.60, respectively. The air

  9. Characterization of carbonaceous deposits by temperature-programmed oxidation

    SciTech Connect

    Bond, G.C. [Brunel Univ., Uxbridge (United Kingdom)] [Brunel Univ., Uxbridge (United Kingdom); Dias, C.R.; Portela, M.F. [Instituto Superior Tecnico, Lisbon (Portugal)] [Instituto Superior Tecnico, Lisbon (Portugal)

    1995-10-01

    The reactions of organic compounds on solid catalysts can be accompanied by the formation of heavy by-products which can form a carbonaceous deposit on the surface and cause deactivation. They are of major importance in catalysis research and stimulate considerable interest. Temperature-programmed oxidation (TPO) can play an important role in their characterization: it consists of exposing a sample to a flowing O{sub 2}/inert gas mixture while increasing its temperature, the amount of carbonaceous compounds oxidized being determined by quantification of the O{sub 2} consumed or CO{sub 2} formed. In this work, the authors have used the former method because of the availability of apparatus to measure O{sub 2} concentration by thermal conductivity. The problem with measuring O{sub 2} consumption is that one cannot be certain that only CO{sub 2} is formed, and no CO. The authors report here on the TPO of pure carbon (activated charcoal) in the presence and in the absence of a palladium catalyst, the function of which was to oxidise any CO formed to CO{sub 2} 14 refs., 3 figs., 1 tab.

  10. Sorption/desorption reversibility of phenanthrene in soils and carbonaceous materials

    SciTech Connect

    Guohui Wang; Sybille Kleineidam; Peter Grathwohl [University of Tuebingen, Tuebingen (Germany). Center for Applied Geoscience

    2007-02-15

    Sorption/desorption of phenanthrene in two soil samples and carbonaceous materials was found to yield co-incident equilibrium isotherms and no significant hysteresis was observed. Additionally, release of native phenanthrene was investigated. Equilibrium sorption and desorption isotherms were determined using pulverized samples of Pahokee peat, lignite, and high-volatile bituminous coal, a mineral soil, and an anthropogenic soil. Instead of the conventional decant-and-refill batch method, sorption/desorption was driven by temperature changes using consistent samples. Sorption started at 77{sup o}C and was increased by reducing the temperature stepwise to 46, 20, and finally 4{sup o}C. For desorption the temperature was increased stepwise again until 77{sup o}C was reached. Besides the co-incident sorption and desorption isotherms at each temperature step, the solubility-normalized sorption/desorption isotherms of all different temperatures collapse to unique overall isotherms. Leaching of native phenanthrene occurred at much lower concentrations but was well predicted by extrapolation of the spiked sorption isotherms indicating that the release of native phenanthrene involves the same sorption/desorption mechanisms as those for newly added phenanthrene. 35 refs., 4 figs., 5 tabs.

  11. Tunneling effects in the kinetics of helium and hydrogen isotopes desorption from single-walled carbon nanotube bundles

    SciTech Connect

    Danilchenko, B. A., E-mail: danil@iop.kiev.ua; Yaskovets, I. I.; Uvarova, I. Y. [Institute of Physics NASU, Pr. Nauki 46, 03680 Kiev (Ukraine); Dolbin, A. V.; Esel'son, V. B.; Basnukaeva, R. M.; Vinnikov, N. A. [B. Verkin Institute for Low Temperature Physics and Engineering NASU, 47 Lenin Ave., Kharkov 61103 (Ukraine)

    2014-04-28

    The kinetics of desorption both helium isotopes and molecules of hydrogen and deuterium from open-ended or ?-irradiated single-walled carbon nanotube bundles was investigated in temperature range of 10–300?K. The gases desorption rates obey the Arrhenius law at high temperatures, deviate from it with temperature reduction and become constant at low temperatures. These results indicate the quantum nature of gas outflow from carbon nanotube bundles. We had deduced the crossover temperature below which the quantum corrections to the effective activation energy of desorption become significant. This temperature follows linear dependence against the inverse mass of gas molecule and is consistent with theoretical prediction.

  12. Changes induced on the surfaces of small Pd clusters by the thermal desorption of CO

    NASA Technical Reports Server (NTRS)

    Doering, D. L.; Poppa, H.; Dickinson, J. T.

    1980-01-01

    The stability and adsorption/desorption properties of supported Pd crystallites less than 5 nm in size were studied by Auger electron spectroscopy and repeated flash thermal desorption of CO. The Pd particles were grown epitaxially on heat-treated, UHV-cleaved mica at a substrate temperature of 300 C and a Pd impingement flux of 10 to the 13th atoms/sq cm s. Auger analysis allowed in situ measurement of relative particle dispersion and contamination, while FTD monitored the CO desorption properties. The results show that significant changes in the adsorption properties can be detected. Changes in the Pd Auger signal and the desorption spectrum during the first few thermal cycles are due to particle coalescence and facetting and the rate of this change is dependent on the temperature and duration of the desorption. Significant reductions in the amplitude of the desorptions peak occur during successive CO desorptions which are attributed to increases of surface carbon, induced by the desorption of CO. The contamination process could be reversed by heat treatment in oxygen or hydrogen

  13. Direct observation of isothermal adsorption and desorption processes of CO on the Ni(100) surface

    NASA Astrophysics Data System (ADS)

    Takagi, N.; Yoshinobu, J.; Kawai, Maki

    1993-11-01

    Isothermal adsorption and desorption processes of CO on the Ni(100) surface have been investigated using time-resolved infrared reflection absorption spectroscopy at several temperatures from 310 to 415 K. The following information on the kinetics of CO adsorption and desorption is obtained by direct observation of the adsorbed CO. The initial sticking coefficient is found to be constant within this temperature range. The desorption energy and the preexponential factor are determined to be 127 kJ mol -1 and 1.6 × 10 14 s -1, respectively.

  14. DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART I.

    SciTech Connect

    Shanahan, K; Jeffrey Holder, J

    2006-07-10

    Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I will discuss the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

  15. A metal-organic framework as a chemical guide to control hydrogen desorption pathways of ammonia borane

    NASA Astrophysics Data System (ADS)

    Jeong, Hyung Mo; Shin, Weon Ho; Park, Jung Hyo; Choi, Jung Hoon; Kang, Jeung Ku

    2014-05-01

    We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption.We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01296h

  16. Low-Temperature Geothermal Resources, Geothermal Technologies Program (GTP) (Fact Sheet)

    SciTech Connect

    Not Available

    2010-05-01

    This document highlights the applications of low-temperature geothermal resources and the potential for future uses as well as current Geothermal Technologies Program-funded projects related to low-temperature resources.

  17. Effect of surface nanostructure on temperature programmed reaction spectroscopy

    NASA Astrophysics Data System (ADS)

    Rieger, Michael; Rogal, Jutta; Reuter, Karsten

    2008-03-01

    Using the catalytic CO oxidation at RuO2(110) as a showcase, we employ first-principles kinetic Monte Carlo simulations to illustrate the intricate effects on temperature programmed reaction (TPR) spectroscopy data brought about by the mere correlations between the locations of the active sites at a nanostructured surface. Even in the absence of lateral interactions, this nanostructure alone can cause inhomogeneities that cannot be grasped by prevalent mean-field data analysis procedures, which thus lead to wrong conclusions on the reactivity of the different surface species. The RuO2(110) surface studied here exhibits only two prominent active sites, arranged in simple alternating rows. Yet, the mere neglection of this still quite trivial nanostructure leads mean-field TPR data analysis [1] to extract kinetic parameters that are in error by several orders of magnitude and that do not even reflect the relative reactivity of the different surface species correctly [2].[1] S. Wendt, M. Knapp, and H. Over, JACS 126, 1537 (2004).[2] M. Rieger, J. Rogal, and K. Reuter, Phys. Rev. Lett (in press).

  18. Desorption characteristics of mechanically and chemically modified LiNH 2 and (LiNH 2 + LiH)

    Microsoft Academic Search

    J. H. Yao; C. Shang; K. F. Aguey-Zinsou; Z. X. Guo

    2007-01-01

    Considerable effort has been devoted to the Li–N–H system for solid-state hydrogen storage. However, the desorption mechanism is still unclear, the desorption kinetics is too low, and the desorption temperature is too high for practical considerations. Here, the characteristics of LiNH2 and a (LiNH2+LiH) mixture were comparatively studied by simultaneous thermogravimetry, differential scanning calorimetry and mass spectrometry for further understanding

  19. Experimental setup for analysis of sorption and desorption of tritium in liquid lithium under different external conditions

    NASA Astrophysics Data System (ADS)

    Lescinskis, A.; Kizane, G.; Vitins, A.; Platacis, E.; Lielausis, O.; Romanchuks, A.; Kravalis, K.

    2013-12-01

    An original complex device has been designed and created specially for this research. Some of tritium sorption and thermal desorption in liquid lithium experiments has been successfully done already. First experiment series were carried out under reduced pressure (vacuum) to rule out other operating gases (like Ar) that may squeeze out tritium from lithium. Experiments showed good tritium desorption from lithium which highly depends on the temperature. A proportional gas counter tritium monitor was used to collect data from tritium thermal desorption experiments.

  20. Adsorption and desorption processes of CO on the Pd(110) surface: Isothermal kinetics measurements

    NASA Astrophysics Data System (ADS)

    Yagi-Watanabe, Kazutoshi; Fukutani, Hirohito

    2000-05-01

    The adsorption and desorption kinetics of carbon monoxide from a Pd(110) surface were studied under isothermal conditions using a differentially pumped line of sight mass spectrometer. A number of isothermal adsorption and desorption kinetics were taken by repeating the measurements at different surface temperatures. The sticking probability profiles are fit by the Kisliuk model with initial sticking probability of 0.95. The isothermal desorption rates show nonlinear function of coverage and the apparent desorption rate orders by means of the slope of the van't Hoff plots show unusually high values. The temporal desorption rate curves are discussed in terms of a model which requires the presence of two CO surface phases in equilibrium.

  1. A study of the kinetics of isothermal nicotine desorption from silicon dioxide

    NASA Astrophysics Data System (ADS)

    Adnadjevic, Borivoj; Lazarevic, Natasa; Jovanovic, Jelena

    2010-12-01

    The isothermal kinetics of nicotine desorption from silicon dioxide (SiO 2) was investigated. The isothermal thermogravimetric curves of nicotine at temperatures of 115 °C, 130 °C and 152 °C were recorded. The kinetic parameters ( Ea, ln A) of desorption of nicotine were calculated using various methods (stationary point, model constants and differential isoconversion method). By applying the "model-fitting" method, it was found that the kinetic model of nicotine desorption from silicon dioxide was a phase boundary controlled reaction (contracting volume). The values of the kinetic parameters, Ea,? and ln A?, complexly change with changing degree of desorption and a compensation effect exists. A new mechanism of activation for the desorption of the absorbed molecules of nicotine was suggested in agreement with model of selective energy transfer.

  2. Effect of carboxylic and thiol ligands (oxalate, cysteine) on the kinetics of desorption of Hg(II) from kaolinite

    SciTech Connect

    Senevirathna, W. U. [Tennessee Technological University; Zhang, Hong [ORNL; Gu, Baohua [ORNL

    2010-01-01

    Sorption and desorption of Hg(II) on clay minerals can impact the biogeochemical cycle and bio-uptake of Hg in the environment. We studied the kinetics of the desorption of Hg(II) from kaolinite as affected by oxalate and cysteine, representing the ligands with carboxylic and thiol groups of different affinities for Hg(II). The effects of pH (3, 5, and 7), ligand concentration (0.25 and 1.0 mM), and temperature (15 C, 25 C, and 35 C) on the Hg(II) desorption were investigated through desorption kinetics. Our study showed that the Hg(II) desorption was pH dependent. In the absence of any organic ligand, >90% of the previously adsorbed Hg(II) desorbed at pH 3 within 2 h, compared to <10% at pH 7. Similar results were observed in the presence of oxalate, showing that it hardly affected the Hg(II) desorption. Cysteine inhibited the Hg(II) desorption significantly at all the pH tested, especially in the first 80 min with the desorption less than 20%, but the inhibition of the desorption appeared to be less prominent afterwards. The effect of the ligand concentration on the Hg(II) desorption was small, especially in the presence of oxalate. The effect of temperature on the Hg(II) desorption was nearly insignificant. The effect of the organic acids on the Hg(II) sorption and desorption is explained by the formation of the ternary surface complexes involving the mineral, ligand, and Hg(II). The competition for Hg(II) between the cysteine molecules adsorbed on the particle surfaces and in the solution phase probably can also affect the Hg(II) desorption.

  3. Analysis of 35 priority semivolatile compounds in water by stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry. I. Method optimisation.

    PubMed

    León, V M; Alvarez, B; Cobollo, M A; Muñoz, S; Valor, I

    2003-05-30

    A multiresidue method for the determination of 35 organic micropollutants (pesticides and polycyclic aromatic hydrocarbons) in water has been optimised using stir bar sorptive extraction (SBSE) and thermal desorption coupled to capillary gas chromatography-mass spectrometry (GC-MS). In the present work, the different parameters affecting the extraction of the analytes from the water samples to the PDMS-coated stir bars and optimisation of conditions affecting thermal desorption are investigated. The optimised conditions consist of a 100-ml water sample with 20% NaCl addition extracted with 20 mm length x 0.5 mm film thickness stir bars at 900 rpm during 14 h at ambient temperature. Desorption is carried out at 280 degrees C during 6 min under a helium flow of 75 ml/min in the splitless mode while maintaining a cryofocusing temperature of 20 degrees C in the programmed-temperature vaporisation (PTV) injector of the GC-MS system. Finally, the PTV injector is ramped to a temperature of 280 degrees C and the analytes are separated in the GC and detected by MS using full scan mode (m/z 60-400). Under the described conditions, the good repeatability, high analyte recoveries and robustness, make SBSE a powerful tool for routine quality control analysis of the selected semivolatile compounds in water samples. PMID:12885055

  4. Tritium permeation and desorption in reduced activation martensitic steels studied in EXOTIC-9/1 irradiation experiment

    NASA Astrophysics Data System (ADS)

    Fedorov, A. V.; van Til, S.; Magielsen, A. J.; Stijkel, M. P.

    2013-11-01

    The EXOTIC-9/1 has been irradiated in the High Flux Reactor in Petten within the European framework for the development of the helium cooled pebble bed breeder concept. The EXOTIC-9/1 irradiation assembly consists of a pebble bed with Li2TiO3 pebbles enclosed in a EUROFER97 containment. The irradiation of EXOTIC-9/1 proceeded for 301 full power days reaching 1.3 dpa in steel. Irradiation temperatures varied between 613 and 853 K. Tritium permeation in a EUROFER97 containment wall was studied, in-pile, during temperature and purge gas chemistry transients. Under reference purge gas conditions (He + 0.1%H2) permeation proceeded in the diffusion-limited regime. Tritium permeability in EUROFER97 was obtained from analysis of the in-pile data. During the post irradiation examination program a number of EUROFER97 containment wall segments were ramp annealed in a temperature programmed desorption setup. This study determines the amount of tritium retained in the samples and presents analysis of the desorption spectra.

  5. DESORPTION OF PYRETHROIDS FROM SUSPENDED SOLIDS

    PubMed Central

    Fojut, Tessa L.; Young, Thomas M.

    2014-01-01

    Pyrethroid insecticides have been widely detected in sediments at concentrations that can cause toxicity to aquatic organisms. Desorption rates play an important role in determining the bioavailability of hydrophobic organic compounds, such as pyrethroids, because these compounds are more likely to be sorbed to solids in the environment and times to reach sorptive equilibrium can be long. In this study, sequential Tenax desorption experiments were performed with three sorbents, three aging times, and four pyrethroids. A biphasic rate model was fit to the desorption data with r2 > 0.99 and the rapid and slow compartment desorption rate constants and compartment fractions are reported. Suspended solids from irrigation runoff water collected from a field that had been sprayed with permethrin one day prior were used in the experiments to compare desorption rates for field-applied pyrethroids to those for laboratory-spiked materials. Suspended solids were used in desorption experiments because suspended solids can be a key source of hydrophobic compounds to surface waters. The rapid desorption rate parameters of field-applied permethrin were not statistically different than those of laboratory spiked permethrin, indicating that the desorption of the spiked pyrethroids is comparable to those added and aged in the field. Sorbent characteristics had the greatest effect on desorption rate parameters; as organic carbon content of the solids increased, the rapid desorption fractions and rapid desorption rate constants both decreased. The desorption rate constant of the slow compartment for sediment containing permethrin aged for 28 d was significantly different from those aged 1 d and 7 d, while desorption in the rapid and slow compartments did not differ between these treatments. PMID:21538493

  6. Photon stimulated desorption of and nuclear resonant scattering by noble gas atoms at solid surfaces

    E-print Network

    Ikeda, Akihiko

    2015-01-01

    When a noble gas atom approaches a solid surface, it is adsorbed via the Van der Waals force, which is called physisorption. In this thesis, several experimental results concerning physisorbed atoms at surfaces are presented. First, photon stimulated desorption of Xe atoms from a Au substrate using nano-second laser is presented. With the time-of-flight measurements, the translational temperature and the desorption yield of desorbing Xe as a function of laser fluence are obtained. It is discovered that there are non-thermal and thermal desorption pathways. It is discussed that the former path involves a transient formation of the negative ion of Xe. The desorption flux dependence of the thermal pathway is also investigated. We found that at a large desorption fluxes the desorption flow is thermalized due to the post-desorption collisions. The resultant velocity and the temperature of the flow is found to be in good agreement with the theoretical predictions based on the Knudsen layer formation. Lastly, nuclea...

  7. The Generation of Surface-bound Exospheres via Electron-Stimulated Desorption (and Related Phenomena): Results from Apollo samples and Hermian Regolith Simulants

    NASA Astrophysics Data System (ADS)

    Bennett, C.; Poston, M.; McLain, J. L.; Orlando, T. M.

    2014-12-01

    The generation of surface-bound exospheres present around the Moon, Mercury and other airless rocky bodies are produced primarily by the interaction of micrometeoroid impacts and charged particles from the solar wind, and magnetospheres with those surfaces. While the study of the interactions of both micrometeoroids and ion sputtering are well investigated, the contributions arising from energetic electron interactions are typically less-well established. Observations from the Fast Imaging Plasma Spectrometer (FIPS), taken < 400 km from the surface, have shown a plasma cusp with energetic heavy ions (i.e. Na+- and O+-groups) for which the source has not been determined. However, the precipitation of keV electrons onto the surfaces of Mercury has recently been inferred from measurements using the X-Ray Spectrometer (XRS) instrument onboard the MESSENGER spacecraft observations of the night-side of Mercury. A newly developed global kinetic transport model suggests that electron-stimulated desorption (ESD), and possibly light ion stimulated desorption (ISD), can directly yield ions that can be transported and dynamically accelerated to the plasma cusp regions observed by FIPS. In addition, keV electrons and ions from the solar wind and Earth's magnetosphere frequently bombard with the lunar surface. Here, we present some of the most recent results from our ongoing work studying the effects of photon-stimulated desorption (PSD), ion-stimulated desorption (ISD) and implantation, as well as electron-stimulated desorption (ESD). Apollo samples collected from both the lunar highland and Mare regions, as well as simulants of the Mercury Regolith have been investigated. The temperature- (100-600 K) and energy-dependence (threshold - 2 keV) of ESD time-of-flight (ToF) results will be presented for these materials along with some preliminary results from our group based on photon-desorption studies of water on lunar material, temperature-programmed desorption (TPD) studies of water covered regolith and dusts, as well as the effects of ion implantation/sputtering using keV H+ ions on ESD-ToF results. The implications of these results in the context of current observations will be discussed.

  8. Hydrogen desorption properties of multiwall carbon nanotubes with closed and open structures

    NASA Astrophysics Data System (ADS)

    Lee, Ho; Kang, Youn-Seon; Kim, Seoung-Hoe; Lee, Jai-Young

    2002-01-01

    The multiwall carbon nanotubes (MWNTs) synthesized by microwave plasma enhanced chemical vapor deposition in 0.1% CH4 (H2 dilution) reaction gas were shaped in curly structures with the blocked nanoholes and closed caps. On the contrary, the carbon nanotubes with different structures could be obtained in oxygen loaded reaction gas, showing aligned structures with connected holes and open caps. The hydrogen desorption properties of the carbon nanotubes (CNTs) with these closed and open structures were compared by thermal desorption technique. The MWNTs with closed structure desorbed hydrogen at two different temperature ranges such as 290-330 and ˜420 K, where the evolved hydrogen amount were ˜0.64 and ˜0.03 wt %, respectively. In case of aligned and open MWNTs, hydrogen as high as ˜1.97 wt % was released at ambient temperature. The hydrogen desorption of MWNTs with open and closed structure at ambient temperature showed the hydrogen desorption activation energies of -16.5 kJ/mol H2 and -18.5 kJ/mol H2, respectively. The high temperature hydrogen desorption observed only in CNTs with closed and highly defective structure was high desorption activation energy of -124.4 kJ/mol.

  9. Material evaluation program, high-temperature nitriding environment

    NASA Technical Reports Server (NTRS)

    Marcy, R. D.

    1973-01-01

    Results of a program conducted to evaluate materials for construction of a space shuttle hydrazine monopropellant gas generator are presented. The program was designed to select those materials that maintain the properties of strength and ductility after exposure to an 1800 F nitriding environment for 1000 hours.

  10. Low energy electron stimulated desorption from DNA films dosed with oxygen

    SciTech Connect

    Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Cloutier, Pierre; Massey, Sylvain; Sanche, Leon [Groupe en sciences des radiations, Faculte de medecine et des sciences de la sante, Universite de Sherbrooke, Sherbrooke, Quebec J1H 5N4 (Canada)

    2012-06-21

    Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O{sub 2}. The OH{sup -} desorption yields increase markedly with exposure to O{sub 2} at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O{sup -}, attributable to dissociative electron attachment to trapped O{sub 2} molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O{sub 2} shows that this surprising increase in OH{sup -} desorption, at elevated temperatures, arises from the reaction of O{sub 2} with damaged DNA sites. These results thus appear to be a manifestation of the so-called 'oxygen fixation' effect, well known in radiobiology.

  11. H2 adsorption on multiwalled carbon nanotubes at low temperatures and low pressures

    NASA Astrophysics Data System (ADS)

    Xu, F.; Barberio, M.; Vasta, R.; Barone, P.; Bonanno, A.; Pirronello, V.

    2008-11-01

    We present an experimental study on H2 adsorption on multiwalled carbon nanotubes (MWCNTs) at low temperatures (12-30 K) and low pressures (2×10-5Torr) using the temperature programmed desorption technique. Our results show that the molecular hydrogen uptake increases nearly exponentially from 6×10-9wt.% at 24.5 K to 2×10-7wt.% at 12.5 K and that the desorption kinetics is of the first order. Comparative measurements indicate that MWCNTs have an adsorption capacity about two orders higher than that of activated carbon (charcoal) making them a possible candidate as hydrogen cryosorber for eventual applications in accelerators and synchrotrons.

  12. Influence of H_2O coadsorption on Electron-Stimulated Desorption of SF_6

    NASA Astrophysics Data System (ADS)

    Kusmierek, D. O.; Faradzhev, N. S.; Madey, T. E.

    2004-03-01

    This work focuses on scattering processes affecting the survival probability and "depth of origin" of low-energy ions (F+, F-), that pass through condensed ultrathin layers of polar H_2O molecules. The ions are generated by electron stimulated desorption (ESD) of SF6 adsorbed on Ru(0001) at 25K. ESD ion angular distribution (ESDIAD) and temperature programmed desorption (TPD) reveal predominantly molecular adsorption of SF6 on Ru(0001) via three F atoms, with the other three pointing away from the surface. Adsorption of overlayers of H_2O leads to changes in both the F+ and F- ion intensities (attenuation and enhancement) as well as dramatic changes in the ion angular distributions. Analysis of these changes gives insight into the role of charge-transfer and elastic scattering processes during the passage of ions through ultrathin polar films, as well as the influence of coadsorbates on adsorption geometry. Interaction of low-energy electrons with condensed SF6 + H_2O films results in the formation of a new chemical species, SOF_2. This has interesting implications for environmental chemistry.

  13. In-situ moisture desorption characterization of epoxy mold compound

    Microsoft Academic Search

    Xuejun Fan; Vishal Nagaraj

    2012-01-01

    Moisture desorption characteristics of an epoxy mold compound (EMC) at 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, and 260°C, respectively, is studied in this paper. A high resolution moisture analyzer is used to measure in-situ moisture weight loss as a function of time at different temperatures. The specimens are preconditioned (e.g. 85°C \\/85%RH) before they are placed in the

  14. The influence of desorption kinetics on hydrogen permeation in iron

    NASA Astrophysics Data System (ADS)

    Arbab, M.; Hudson, J. B.

    1987-09-01

    The common observation that the diffusivity of hydrogen in iron decreases anomalously at low temperatures is treated in terms of the barrier to adatom recombination and desorption that is known to be associated with the surfaces of this metal. Results obtained are in good agreement both with data on deuterium permeation through a polycrystalline iron sample, obtained in this study, and with the body of measurements for hydrogen diffusion through iron found in the literature.

  15. Oregon Low-Temperature-Resource Assessment Program. Final technical report

    SciTech Connect

    Priest, G.R.; Black, G.L.; Woller, N.M.

    1981-01-01

    Numerous low-temperature hydrothermal systems are available for exploitation throughout the Cascades and eastern Oregon. All of these areas have heat flow significantly higher than crustal averages and many thermal aquifers. In northeastern Oregon, low temperature geothermal resources are controlled by regional stratigraphic aquifers of the Columbia River Basalt Group at shallow depths and possibly by faults at greater depths. In southeastern Oregon most hydrothermal systems are of higher temperature than those of northeastern Oregon and are controlled by high-angle fault zones and layered volcanic aquifers. The Cascades have very high heat flow but few large population centers. Direct use potential in the Cascades is therefore limited, except possibly in the cities of Oakridge and Ashland, where load may be great enough to stimulate development. Absence of large population centers also inhibits initial low temperature geothermal development in eastern Oregon. It may be that uses for the abundant low temperature geothermal resources of the state will have to be found which do not require large nearby population centers. One promising use is generation of electricity from freon-based biphase electrical generators. These generators will be installed on wells at Vale and Lakeview in the summer of 1982 to evaluate their potential use on geothermal waters with temperatures as low as 80/sup 0/C (176/sup 0/F).

  16. Analysis of waterborne paints by gas chromatography–mass spectrometry with a temperature-programmable pyrolyzer

    Microsoft Academic Search

    Sadao Nakamura; Masahiko Takino; Shigeki Daishima

    2001-01-01

    Gas chromatography–mass spectrometry (GC–MS) with a temperature-programmable pyrolyzer was used for the analysis of waterborne paints. Evolved gas analysis (EGA) profiles of the waterborne paints were obtained by this temperature-programmed pyrolysis directly coupled with MS via a deactivated metal capillary tube. The EGA profile suggested the optimal thermal desorption conditions for solvents and additives and the subsequent optimal pyrolysis temperature

  17. High Temperature Materials Laboratory User Program: 19th Annual Report, October 1, 2005 - September 30, 2006

    SciTech Connect

    Pasto, Arvid [ORNL

    2007-08-01

    Annual Report contains overview of the High Temperature Materials Laboratory User Program and includes selected highlights of user activities for FY2006. Report is submitted to individuals within sponsoring DOE agency and to other interested individuals.

  18. Adsorption and desorption of mixed molecular ices from a cosmic dust grain analogue surface

    NASA Astrophysics Data System (ADS)

    Wolff, Angela Jean

    Surface science is playing an ever more prominent role in the field of astronomy. More than 220 different molecules have so far been observed in the interstellar medium (ISM), and for several of these molecules, the observed abundance is such that the molecules cannot be formed by gas phase reactions alone. Astronomers have proposed that they are instead formed by heterogeneous reactions that take place on the surface of dust grains. The two alcohols methanol and ethanol are just two of the molecules typically observed in both the gas and solid phase in the ISM. In the solid phase, they are found frozen out with the more abundant water, as molecular ices on the surface of dust grains. Both alcohols can be viewed as evolutionary indicators in the vicinity of hot cores. Hot cores are compact objects found in close to newly formed massive stars they are dense and relatively warm and show atypical gas-phase molecular compositions. The gas-phase composition, and therefore the evolutionary stage of the hot core, can be understood by considering the sublimation behaviour of molecular ices on the dust grains within the molecular cloud. This thesis presents the results of investigations on the adsorption and desorption of methanol and ethanol in both the pure state and in combination with water. In each case the deposition occurs on a highly oriented pyrolytic graphite (HOPG) surface. HOPG is considered to be a suitable interstellar dust grain analogue, as dust grains in the ISM are composed of mainly carbonaceous and silicaceous material. Temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) studies of methanol and ethanol ices, mixed with water, are presented. The adsorption and desorption of each species deposited on a layer of amorphous solid water ice is compared to those of codeposited ice layers. In all systems, there is evidence for molecular adsorption in a physisorbed state and for interactions between the investigated molecule and the water ice. As expected, the sequentially deposited systems show different behaviour when compared with the codeposited systems. The information obtained from these experiments is of direct relevance to astronomers, as the measured desorption energies can be incorporated directly into astronomical models. This, in turn, helps to lead to a greater understanding of star formation, and hence of the Universe in which we live.

  19. Estimation of retention times of homologous series in temperature programmed gas chromatography

    Microsoft Academic Search

    P. E. Kavanagh; D. Balder; G. Franklin

    1999-01-01

    Summary  It is shown how to estimate the retention times of homologous series members in linear temperature programmed gas chromatography\\u000a with the aid of a spread-sheet. Both the ease of estimation and the accuracy of the estimation depend on whether the homologue\\u000a is eluted during the rising portion of the temperature program or the hold time at the end, and also

  20. Desorption Kinetics of Polyether Lubricants from Surfaces

    Microsoft Academic Search

    Andrew J. Gellman; Kris R. Paserba; Nithya Vaidyanathan

    2002-01-01

    Desorption or evaporation is one of the mechanisms for loss of perfluoropolyalkylether (PFPE) lubricants from the surfaces of data storage media. One approach to minimizing PFPE loss to desorption is the use of lubricants with increasing molecular weight or increasing average chain length. In order to understand the effects of chain length on the lubricant evaporation kinetics we have studied

  1. On metal desorption and brucite regeneration

    Microsoft Academic Search

    G. R. Bochkarev; G. I. Pushkareva

    2006-01-01

    The data on metal desorption from brucite surface under the action of acid and alkaline dissolvents are reported. The desorption\\u000a process is found to associate with the regeneration of a sorbent along with the substantial improvement of its sorption capacity.

  2. 1992--1993 low-temperature geothermal assessment program, Colorada

    SciTech Connect

    Cappa, J.A.; Hemborg, H.T.

    1995-01-01

    Previous assessments of Colorado`s low-temperature geothermal resources were completed by the Colorado Geological Survey in 1920 and in the mid- to late-1970s. The purpose of the 1992--1993 low-temperature geothermal resource assessment is to update the earlier physical, geochemical, and utilization data and compile computerized databases of the location, chemistry, and general information of the low-temperature geothermal resources in Colorado. The main sources of the data included published data from the Colorado Geological Survey, the US Geological Survey WATSTOR database, and the files of the State Division of Water Resources. The staff of the Colorado Geological Survey in 1992 and 1993 visited most of the known geothermal sources that were recorded as having temperatures greater than 30{degrees}C. Physical measurements of the conductivity, pH, temperature, flow rate, and notes on the current geothermal source utilization were taken. Ten new geochemical analyses were completed on selected geothermal sites. The results of the compilation and field investigations are compiled into the four enclosed Quattro Pro 4 databases. For the purposes of this report a geothermal area is defined as a broad area, usually less than 3 sq mi in size, that may have several wells or springs. A geothermal site is an individual well or spring within a geothermal area. The 1992-1993 assessment reports that there are 93 geothermal areas in the Colorado, up from the 56 reported in 1978; there are 157 geothermal sites up from the 125 reported in 1978; and a total of 382 geochemical analyses are compiled, up from the 236 reported in 1978. Six geothermal areas are recommended for further investigation: Trimble Hot Springs, Orvis Hot Springs, an area southeast of Pagosa Springs, the eastern San Luis Valley, Rico and Dunton area, and Cottonwood Hot Springs.

  3. Computer program calculates the effective temperature for a crystalline solid /DETS/

    NASA Technical Reports Server (NTRS)

    Johnston, A. S.; Sowden, M. M.

    1969-01-01

    Computer program computes and prints out both the Debye and resulting effective temperatures for each Debye model-dependent average energy per vibrational mode, Debye-Waller factor, and specific heat. The program calculates by the trapezodial rule and then Simpsons rule.

  4. Patterning graphene at the nanometer scale via hydrogen desorption.

    SciTech Connect

    Sessi, P.; Guest, J. R.; Bode, M.; Guisinger, N.; Center for Nanoscale Materials; Politecnico di Milano

    2009-12-01

    We have demonstrated the reversible and local modification of the electronic properties of graphene by hydrogen passivation and subsequent electron-stimulated hydrogen desorption with an scanning tunneling microscope tip. In addition to changing the morphology, we show that the hydrogen passivation is stable at room temperature and modifies the electronic properties of graphene, opening a gap in the local density of states. This insulating state is reversed by local desorption of the hydrogen, and the unaltered electronic properties of graphene are recovered. Using this mechanism, we have 'written' graphene patterns on nanometer length scales. For patterned regions that are roughly 20 nm or greater, the inherent electronic properties of graphene are completely recovered. Below 20 nm we observe dramatic variations in the electronic properties of the graphene as a function of pattern size. This reversible and local mechanism for modifying the electronic properties of graphene has far-reaching implications for nanoscale circuitry fabricated from this revolutionary material.

  5. Fortran computer programs to plot and process aquifer pressure and temperature data

    USGS Publications Warehouse

    Czarnecki, J.B.

    1983-01-01

    Two FORTRAN computer programs have been written to process water-well temperature and pressure data recorded automatically by a datalogger on magnetic tape. These programs process the data into tabular and graphical form. Both programs are presented with documentation. Sample plots of temperature versus time, water levels versus time, aquifer pressure versus log time , log drawdown versus log 1/time, and log drawdown versus log time/radius squared are presented and are obtained using standard CALCOM directives. Drawdown plots may be used directly to obtain aquifer transmissivities and storage coefficients as well as leakance coefficients. (USGS)

  6. Treating high-mercury-containing lamps using full-scale thermal desorption technology.

    PubMed

    Chang, T C; You, S J; Yu, B S; Chen, C M; Chiu, Y C

    2009-03-15

    The mercury content in high-mercury-containing lamps are always between 400 mg/kg and 200,000 mg/kg. This concentration is much higher than the 260 mg/kg lower boundary recommended for the thermal desorption process suggested by the US Resource Conservation and Recovery Act. According to a Taiwan EPA survey, about 4,833,000 cold cathode fluorescent lamps (CCFLs), 486,000 ultraviolet lamps and 25,000 super high pressure mercury lamps (SHPs) have been disposed of in the industrial waste treatment system, producing 80, 92 and 9 kg-mercury/year through domestic treatment, offshore treatment and air emissions, respectively. To deal with this problem we set up a full-scale thermal desorption process to treat and recover the mercury from SHPs, fluorescent tube tailpipes, fluorescent tubes containing mercury-fluorescent powder, and CCFLs containing mercury-fluorescent powder and monitor the use of different pre-heating temperatures and desorption times. The experimental results reveal that the average thermal desorption efficiency of SHPs and fluorescent tube tailpipe were both 99.95%, while the average thermal desorption efficiencies of fluorescent tubes containing mercury-fluorescent powder were between 97% and 99%. In addition, a thermal desorption efficiency of only 69.37-93.39% was obtained after treating the CCFLs containing mercury-fluorescent powder. These differences in thermal desorption efficiency might be due to the complexity of the mercury compounds contained in the lamps. In general, the thermal desorption efficiency of lamps containing mercury-complex compounds increased with higher temperatures. PMID:18603361

  7. Research and development program for the development of advanced time-temperature dependent constitutive relationships. Volume 2: Programming manual

    NASA Technical Reports Server (NTRS)

    Cassenti, B. N.

    1983-01-01

    The results of a 10-month research and development program for nonlinear structural modeling with advanced time-temperature constitutive relationships are presented. The implementation of the theory in the MARC nonlinear finite element code is discussed, and instructions for the computational application of the theory are provided.

  8. A control system for maintaining a predetermined temperature program 

    E-print Network

    Roots, Edmund Nelson

    1956-01-01

    to raise the temperature to To is a function of tsmpsx'ature an& time. The heat energy stored in the system vill bs m(T -T ) where m is the, so called, fictitious mass of' the o a system, To 1s the tempsxatuxe desired in ths system, nnd. Ta is ths... current, Xc, of the first power stage vill then have the de ired. range of -@ma to +16ma. Next to be considered is the power control stage. It was estimated, that e maximu~ of 500 to 600 w. =. tts output would be necessazy for the heatin;;. unit...

  9. Interaction of Atomic and Molecular Hydrogen with Tholin Surfaces at Low Temperatures

    E-print Network

    Li, Ling; Vidali, Gianfranco; Frank, Yechiel; Lohmar, Ingo; Perets, Hagai B; Biham, Ofer; 10.1021/jp104944y

    2010-01-01

    We study the interaction of atomic and molecular hydrogen with a surface of tholin, a man-made polymer considered to be an analogue of aerosol particles present in Titan's atmosphere, using thermal programmed desorption at low temperatures below 30 K. The results are fitted and analyzed using a fine-grained rate equation model that describes the diffusion, reaction and desorption processes. We obtain the energy barriers for diffusion and desorption of atomic and molecular hydrogen. These barriers are found to be in the range of 30 to 60 meV, indicating that atom/molecule-surface interactions in this temperature range are dominated by weak adsorption forces. The implications of these results for the understanding of the atmospheric chemistry of Titan are discussed.

  10. Interaction of atomic and molecular hydrogen with tholin surfaces at low temperatures.

    PubMed

    Li, Ling; Zhao, Hui; Vidali, Gianfranco; Frank, Yechiel; Lohmar, Ingo; Perets, Hagai B; Biham, Ofer

    2010-10-01

    We study the interaction of atomic and molecular hydrogen with a surface of tholin, a man-made polymer considered to be an analogue of aerosol particles present in Titan's atmosphere, using thermal programmed desorption at low temperatures below 30 K. The results are fitted and analyzed using a fine-grained rate equation model that describes the diffusion, reaction, and desorption processes. We obtain the energy barriers for diffusion and desorption of atomic and molecular hydrogen. These barriers are found to be in the range of 30-60 meV, indicating that atom/molecule-surface interactions in this temperature range are dominated by weak adsorption forces. The implications of these results for the understanding of the atmospheric chemistry of Titan are discussed. PMID:20831204

  11. Modelling deuterium release during thermal desorption of D +-irradiated tungsten

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    Thermal desorption profiles were modelled based on SIMS measurements of implantation profiles and using the multi-trap diffusion code TMAP7 [G.R. Longhurst, TMAP7: Tritium Migration Analysis Program, User Manual, Idaho National Laboratory, INEEL/EXT-04-02352 (2004)]. The thermal desorption profiles were the result of 500 eV/D + irradiations on single crystal tungsten at 300 and 500 K to fluences of 10 22-10 24 D +/m 2. SIMS depth profiling was performed after irradiation to obtain the distribution of trapped D within the top 60 nm of the surface. Thermal desorption spectroscopy (TDS) was performed subsequently to obtain desorption profiles and to extract the total trapped D inventory. The SIMS profiles were calibrated to give D concentrations. To account for the total trapped D inventory measured by TDS, SIMS depth distributions were used in the near-surface (surface to 30 nm), NRA measurements [V.Kh. Alimov, J. Roth, M. Mayer, J. Nucl. Mater. 337-339 (2005) 619] were used in the range 1-7 ?m, and a linear drop in the D distribution was assumed in the intermediate sub-surface region (˜30 nm to 1 ?m). Traps were assumed to be saturated so that the D distribution also represented the trap distribution. Three trap energies, 1.07 ± 0.03, 1.34 ± 0.03 and 2.1 ± 0.05 eV were required to model the 520, 640 and 900 K desorption peaks, respectively. The 1.34 and 1.07 eV traps correspond to trapping of a first and second D atom at a vacancy, respectively, while the 2.1 eV trap corresponds to atomic D trapping at a void. A fourth trap energy of 0.65 eV was used to fit the 400 K desorption peak observed by Quastel et al. [A.D. Quastel, J.W. Davis, A.A. Haasz, R.G. Macaulay-Newcombe, J. Nucl. Mater. 359 (2006) 8].

  12. Desorption induced by multiple electronic transitions

    NASA Astrophysics Data System (ADS)

    Misewich, J. A.; Heinz, T. F.; Newns, D. M.

    1992-06-01

    A new mechanism is introduced to describe desorption from surfaces under conditions of strong electronic excitation. When repetitive excitations occur within the relaxation time for the adsorbate-surface vibration, the process of desorption induced by multiple electronic transitions may provide an enhancement of orders of magnitude over a single-excitation mechanism. This generalization of the classic Menzel-Gomer-Redhead picture encompasses within one formalism both single-excitation processes and a thermal limit. The mechanism may be operative in desorption by femtosecond laser pulses.

  13. Interaction of Acetone with Single Wall Carbon Nanotubes at Cryogenic Temperatures: A Combined Temperature Programmed

    E-print Network

    Borguet, Eric

    Interaction of Acetone with Single Wall Carbon Nanotubes at Cryogenic Temperatures: A CombinedVersity, Philadelphia, PennsylVania 19122, Department of Chemical Engineering, UniVersity of Pittsburgh, Pittsburgh, PennsylVania 15261, Department of Chemistry and Institute for AdVanced Research, Nagoya UniVersity, Nagoya

  14. Desorption corona beam ionization source for mass spectrometry.

    PubMed

    Wang, Hua; Sun, Wenjian; Zhang, Junsheng; Yang, Xiaohui; Lin, Tao; Ding, Li

    2010-04-01

    A novel Desorption Corona Beam Ionization (DCBI) source for direct analysis of samples from surface in mass spectrometry is reported. The DCBI source can work under ambient conditions without time-consuming sample pretreatments. The source shares some common features with another ionization source - Direct Analysis in Real Time (DART), developed earlier. For example, helium was used as the discharge gas (although only corona discharge is involved in the present source), and heating of the discharge gas is required for sample desorption. However, the difference between the two sources is substantial. In the present source, a visible thin corona beam extending out around 1 cm can be formed by using a hollow needle/ring electrode structure. This feature would greatly facilitate localizing sampling areas and performing imaging/profiling experiments. The DCBI source is also capable of performing progressive temperature scans between room temperature and 450 degrees C in order to sequentially desorb samples from the surface and, therefore, to achieve a rough separation of the individual components in a complex mixture, resulting in less congestion in the mass spectrum acquired. Mass spectra for a broad range of compounds (pesticides, veterinary additives, OTC drugs, explosive materials) have been acquired using the DCBI source. For most of the compounds tested, the heater temperature required for efficient desorption is at least 150 degrees C. The molecular weight of the sample that can be desorbed/ionized is normally below 600 dalton even at the highest heater temperature, which is mainly limited by the volatility of the sample. PMID:20349536

  15. Adsorption of CH3OD on Si(111) Surface at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Zhuying; Huang, Hongwu; T, Hein; K, D. Brzoska

    1991-04-01

    Adsorption of deuterated methanol (CH3OD) on Si(111) surface has been studied at different temperatures by means of thermal desorption spectroscopy. For the adsorption temperature below 420° C, the desorption peak of hydrogen kept up almost unchanged at 510° C(±7° C). But the desorption peak temperature of hydrogen increased obviously for the adsorption temperature above 420° C. We have also found an interesting change in desorption energy of hydrogen.

  16. Desorption behavior of sorbed flavor compounds from packaging films with ethanol solution.

    PubMed

    Hwang, Y H; Matsui, T; Hanada, T; Shimoda, M; Matsumoto, K; Osajima, Y

    2000-09-01

    Desorption behavior of sorbed flavor compounds such as ethyl esters, n-aldehydes, and n-alcohols from LDPE and PET films was investigated in 0 to 100% (v/v) ethanol solutions at 20 degrees C, 50 degrees C, and 60 degrees C. In both films, the desorption apparently increased with increasing ethanol concentration and treatment temperature, depending on the compatibility of the flavor compound with the solvent. Namely, the partition coefficient of ethyl esters, n-aldehydes, and n-alcohols in the LDPE film turned out to be approximately zero at >/=60%, >/=80%, and >/=40% (v/v) ethanol, respectively (for PET film, >/=80%, >/=80%, and >/=40% (v/v) ethanol concentrations were required for complete desorption, respectively). As for physical properties (heat of fusion, melting point, and tensile strength and elongation at break) of LDPE and PET films, there were no significant differences between intact film and the treated film with 60% (v/v) ethanol for 30 min at 60 degrees C. These results suggest that it is possible to apply a desorption solvent such as ethanol solution for desorption of sorbed flavor compounds from packaging films with no physical change in the film properties by this desorption treatment. PMID:10995356

  17. Photon-stimulated desorption as a substantial source of sodium in the lunar atmosphere.

    PubMed

    Yakshinskiy, B V; Madey, T E

    1999-08-12

    Mercury and the Moon both have tenuous atmospheres that contain atomic sodium and potassium. These chemicals must be continuously resupplied, as neither body can retain the atoms for more than a few hours. The mechanisms proposed to explain the resupply include sputtering of the surface by the solar wind, micrometeorite impacts, thermal desorption and photon-stimulated desorption. But there are few data and no general agreement about which processes dominate. Here we report laboratory studies of photon-stimulated desorption of sodium from surfaces that simulate lunar silicates. We find that bombardment of such surfaces at temperatures of approximately 250 K by ultraviolet photons (wavelength lambda < 300 nm) causes very efficient desorption of sodium atoms, induced by electronic excitations rather than by thermal processes or momentum transfer. The flux at the lunar surface of ultraviolet photons from the Sun is sufficient to ensure that photon-stimulated desorption of sodium contributes substantially to the Moon's atmosphere. On Mercury, solar heating of the surface implies that thermal desorption will also be an important source of atmospheric sodium. PMID:10458159

  18. Matrix effects in plasma desorption mass spectrometry

    Microsoft Academic Search

    Stephane Bouchonnet; Yannik Hoppilliard; Christine Mauriac

    1993-01-01

    In Plasma Desorption (PD) Mass Spectrometry, valine\\/matrix mixtures have been studied in order to specify the influence of a matrix during the desorption-ionization (DI) of volume. The different matrices used were carboxylic acids (barbituric acid, 2-chloronicotinic acid, 3-chloropropionic acid, cysteine, pentafluorobenzoic acid, picric acid, sinapinic acid) and CsI, an inorganic salt. Three effects are proposed to explain the influence of

  19. Novel devices for solvent delivery and temperature programming designed for capillary liquid chromatography.

    PubMed

    Coutinho, Lincoln Figueira Marins; Nazario, Carlos Eduardo Domingues; Monteiro, Alessandra Maffei; Lanças, Fernando Mauro

    2014-08-01

    Analyses in chromatographic systems able to save mobile and stationary phases without reducing efficiency and resolution are of current interest. These advantages regarding savings have challenged us to develop a system dedicated to miniaturized liquid chromatography. This paper reports on the development of a high-pressure syringe-type pump, an oven able to perform isothermal and temperature programming and a software program to control these chromatographic devices. The experimental results show that the miniaturized system can generate reproducible and accurate temperature and flow rate. The system was applied to the separation of statins and tetracylines and showed excellent performance. PMID:24838528

  20. Two-factor simplex optimization of a programmed temperature gas chromatographic separation. [Ethylbenzene, butycyclohexane

    SciTech Connect

    Walters, F.H.; Deming, S.N.

    1984-01-01

    Simplex optimization was used to optimize the temperature programmed gas chromatographic separation of octane, 2-methyl-tetrahydrofuran, butylcyclohexane, and ethylbenzene. The initial temperature and the programming rate were the factors studied and a 5 minute time constraint was placed on the system. The Chromatographic Response Function (CRF) used by Deming and Morgan was used as an operational measure of performance. Further experiments in the region of the optimum and regression analysis of the data obtained were carried out to further understand the factor effects. 9 references, 2 figures, 2 tables.

  1. Desorption of bis(2-chloroethyl) sulfide, mustard agent, from the surface of hardened cement paste (HCP) wafers.

    PubMed

    Tang, Hairong; Zhou, Xuezhi; Guan, Yingqiang; Zhou, Liming; Wang, Xinming; Yan, Huijuan

    2013-05-01

    The decontamination of surfaces exposed to chemical warfare agents is an interesting scientific topic. The desorption behavior of bis(2-chloroethyl) sulfide (sulfur mustard, HD) from the surface of the HD-contaminated hardened cement paste (HCP) was investigated under different weather conditions, which should provide scientific reference data for protection and decontamination projects involving HD-contaminated HCP in different conditions. The desorption of HD from the surface of HCP wafers was studied, and the effects of the purge air flow rate, water content, sorption temperature, and substrate age were investigated. HD desorption was detected from the surface of HD-contaminated HCP, but the desorption velocity was relatively slow. The desorption quantity remained within an order of magnitude throughout a time span of 36h (25°C at 200mL/min of purge air), and the amount of HD that was desorbed from each square meter of HCP surface was approximately 1.1g (25°C at 200mL/min of purge air), which was approximately 5.5 percent of the total HD that was initially applied. A higher flow rate of the purge air, increased water content, and longer substrate age of HCP all increased the HD desorption. In contrast, increased temperatures suppressed HD desorption. PMID:23395389

  2. A New Method for Studying Thermal Desorption of Hydrogen from Metals Based on Internal Friction Technique

    NASA Astrophysics Data System (ADS)

    Yagodzinskyy, Yu.; Yagodzinskyy, Yu.; Tarasenko, O.; Smuk, S.; Aaltonen, P.; Hänninen, H.; Hänninen, H.

    Many hydrogenated pure metals and industrial alloys with FCC lattices show a distinct internal friction peak above room temperature caused by the thermal desorption of hydrogen. Based on these observations, a new method for studying the hydrogen diffusivity and the interaction of hydrogen with lattice defects is proposed for the temperature range of 250-500 K. The desorption origin of the peak was studied in detail in hydrogen-charged Inconel 600 alloys with different carbon contents. The peak was shown to possess transient and non-relaxation nature. In some cases, a fine structure of the peak caused by hydrogen traps can be observed. A theoretical model of the thermal desorption effects on the losses of mechanical energy, i.e., internal friction, in metals is developed.

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

    PubMed

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  5. Direct thermal desorption of semivolatile organic compounds from diffusion denuders and gas chromatographic analysis for trace concentration measurement.

    SciTech Connect

    Tobias, D. E.; Perlinger, J. A.; Morrow, P. S.; Doskey, P. V.; Perram, D.L.; Environmental Science Division; Michigan Technological Univ.

    2007-01-01

    A novel method for collection and analysis of vapor-phase semivolatile organic compounds (SOCs) in ambient air is presented. The method utilizes thermal desorption of SOCs trapped in diffusion denuders coupled with cryogenic preconcentration on Tenax-TA and analysis by high resolution gas chromatography (GC)-electron-capture detection (ECD). The sampling and analysis methods employ custom-fabricated multicapillary diffusion denuders, a hot gas spike (HGS) apparatus to load known quantities of thermally stable standards into diffusion denuders prior to sample collection, a custom-fabricated oven to thermally desorb SOCs from the diffusion denuder, and a programmable temperature vaporization (PTV) inlet containing a liner packed with Tenax-TA for effective preconcentration of the analytes and water management. High flow rates into the PTV inlet of 750 mL min-1during thermal desorption are ca. a factor of ten greater than typically used. To improve resolution and retention time stability, the thermal desorption and PTV inlet programming procedure includes three steps to prevent water from entering the analytic column while effectively transferring the analytes into the GC system. The instrumentation and procedures provide virtually complete and consistent transfer of analytes collected from ambient air into the GC evidenced by recovery of seven replicates of four internal standards of 90.7 {+-} 4.0-120 {+-} 23% (mean {+-} 95% confidence interval, CI). Retention time based compound identification is facilitated by low retention time variability with an average 95% CI of 0.024 min for sixteen replicates of eight standards. Procedure details and performance metrics as well as ambient sampling results are presented.

  6. Determination of five booster biocides in seawater by stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry.

    PubMed

    Giráldez, I; Chaguaceda, E; Bujalance, M; Morales, E

    2013-01-01

    Stir bar sorptive extraction (SBSE) and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS) have been optimized for the determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in seawater samples. The parameters affecting the desorption and absorption steps were investigated using 10 mL seawater samples. The optimised conditions consisted of an addition of 0.2 g mL(-1) KCl to the sample, which was extracted with 10mm length, 0.5mm film thickness stir bars coated with polydimethylsiloxane (PDMS), and stirred at 900 rpm for 90 min at room temperature (25 °C) in a vial. Desorption was carried out at 280 °C for 5 min under 50 mL min(-1) of helium flow in the splitless mode while maintaining a cryotrapping temperature of 20 °C in the programmed-temperature vaporization (PTV) injector of the GC-MS system. Finally, the PTV injector was ramped to a temperature of 280 °C and the analytes were separated in the GC and detected by MS using the selected-ion monitoring (SIM) mode. The detection limits of booster biocides were found to be in the range of 0.005-0.9 ?g L(-1). The regression coefficients were higher than 0.999 for all analytes. The average recovery was higher than 72% (R.S.D.: 7-15%). All these figures of merit were established running samples in triplicate. This simple, accurate, sensitive and selective analytical method may be used for the determination of trace amounts of booster biocides in water samples from marinas. PMID:23246091

  7. AISI/DOE Advanced Process Control Program Vol. 6 of 6: Temperature Measurement of Galvanneal Steel

    SciTech Connect

    S.W. Allison; D.L. Beshears; W.W. Manges

    1999-06-30

    This report describes the successful completion of the development of an accurate in-process measurement instrument for galvanneal steel surface temperatures. This achievement results from a joint research effort that is a part of the American Iron and Steel Institute's (AISI) Advanced Process Control Program, a collaboration between the U.S> Department of Energy and fifteen North American Steelmakers. This three-year project entitled ''Temperature Measurement of Galvanneal Steel'' uses phosphor thermography, and outgrowth of Uranium enrichment research at Oak Ridge facilities. Temperature is the controlling factor regarding the distribution of iron and zinc in the galvanneal strip coating, which in turn determines the desired product properties

  8. UV laser desorption of nitric oxide from semiconducting C60/Cu(111)

    NASA Astrophysics Data System (ADS)

    Hoger, T.; Grimmer, D.; Zacharias, H.

    2007-08-01

    The desorption of NO from a well-characterized, epitaxially grown semiconducting C60 surface is reported. Two different channels are identified in the laser desorption. Both channels yield a comparably high desorption cross section of ?1=7.0×10-17 cm2 and ?2=5.5×10-17 cm2 for the first and second channel, respectively. The laser desorbed NO molecules are detected with rovibrational state selectivity by (1+1) REMPI in the A^2?^+ to{X}^2 Pi ?-bands. In the first channel the desorbing molecules are highly excited with an average kinetic energy of =174 meV. The rotational population distribution can be fitted by a rotational temperature of Trot=800 K. A rotational translational coupling is observed, with velocities ranging from 1000 m/s for low to 1300 m/s for high rotational states. The vibrationally excited population is estimated to be less than 1% of the ground state. The second channel yields less excited molecules and an almost Boltzmann distributed rotational population with a temperature of Trot=280 K. The apparent velocity distribution derived from the pump-probe delay yields molecules much too slow to be explained by even a thermal desorption. This desorption is probably caused by a long-lived electronic excitation in the substrate for which a lifetime of ??160 ?s is estimated.

  9. Programmed temperature gasification study. Final report, October 1, 1979November 30, 1980

    Microsoft Academic Search

    M. J. Spoon; M. P. Gardner; J. A. Starkovich; H. L. Fein; A. J. Apte

    1980-01-01

    An experimental, modeling and conceptual engineering analysis study has been performed to assess the feasibility of TRW's Programmed Temperature Gasification (PTG) concept for carbonizing caking coals without severe agglomeration. The concept involves control of carbonizing heating rate to maintain metaplast concentration at a level equal to or slightly below that which causes agglomeration. The experimental studies required the contruction of

  10. Determination of the Arrhenius Activation Energy Using a Temperature-Programmed Flow Reactor.

    ERIC Educational Resources Information Center

    Chan, Kit-ha C.; Tse, R. S.

    1984-01-01

    Describes a novel method for the determination of the Arrhenius activation energy, without prejudging the validity of the Arrhenius equation or the concept of activation energy. The method involves use of a temperature-programed flow reactor connected to a concentration detector. (JN)

  11. Detecting Chemical Hazards with Temperature-Programmed Microsensors: Overcoming Complex Analytical Problems with Multidimensional Databases

    Microsoft Academic Search

    Douglas C. Meier; Baranidharan Raman; Steve Semancik

    2009-01-01

    Complex analytical problems, such as detecting trace quantities of hazardous chemicals in challenging environments, require solutions that most effectively extract relevant information about a sample's composition. This review presents a chemiresistive microarray-based approach to identifying targets that combines temperature-programmed elements capable of rapidly generating analytically rich data sets with statistical pattern recognition algorithms for extracting multivariate chemical fingerprints. We describe

  12. Temperature-programmed sputtered micromachined gas chromatography columns: an approach to fast separations in oilfield applications.

    PubMed

    Haudebourg, R; Vial, J; Thiebaut, D; Danaie, K; Breviere, J; Sassiat, P; Azzouz, I; Bourlon, B

    2013-01-01

    In a previous study, a new stationary phase deposition technique for micromachined gas chromatography columns was presented. The rerouting of the sputtering technique to this purpose enabled collective and reproducible fabrication of microcolumns in a silicon wafer. Silica-sputtered micromachined columns showed promising separations of light alkanes in isothermal conditions. In order to go beyond the limitations of isothermal separations, the columns were equipped with sputtered platinum filaments to enable high-speed and low-power temperature programming. The separation performances of temperature-programmed silica- or graphite-sputtered microcolumns were investigated: a separation of light alkanes (C1-C5) was completed in 9 s, and heavier alkanes (until C9), cyclic, isomeric, and unsaturated hydrocarbons were also successfully separated. Versatility of these microcolumns was demonstrated with a high-temperature C1-C2 separation and a C1-C5 separation with nitrogen as carrier gas instead of helium. By matching the requirements of a gas chromatography-based monitoring sensor, in terms of low-cost and industry-ready fabrication process, fast temperature programming and analysis, low power consumption, and good versatility (ambient temperature, carrier gas), these columns should be used in various applications related to oilfield gas analyses. PMID:23231068

  13. NO x sorption–desorption study: application to diesel and lean-burn exhaust gas (selective NO x recirculation technique)

    Microsoft Academic Search

    S Hodjati; K Vaezzadeh; C Petit; V Pitchon; A Kiennemann

    2000-01-01

    NOx adsorption\\/desorption capacities of barium aluminates and BaSnO3 were measured under representative exhaust gas mixture at temperatures below 550°C and compared to those of bulk BaO. The capacities are high and the test of sorption–desorption is reproducible on barium aluminate and BaSnO3, while this is not the case on BaO. The difference is due to the electronic environment of barium

  14. DEMONSTRATION BULLETIN: X*TRAX MODEL 200 THERMAL DESORPTION SYSTEMS - CHEMICAL WASTE MANAGEMENT, INC.

    EPA Science Inventory

    The X*TRAX? Mode! 200 Thermal Desorption System developed by Chemical Waste Management, Inc. (CWM), is a low-temperature process designed to separate organic contaminants from soils, sludges, and other solid media. The X*TRAX? Model 200 is fully transportable and consists of thre...

  15. Effects of conformational isomerism on the desorption kinetics of n-alkanes from graphite

    E-print Network

    Gellman, Andrew J.

    -alkane with the minimum free energy at the desorption temperature. These results reveal that conformational isomerism also find that Edes has a nonlinear dependence on chain length and takes the empirical form Edes a b exponent in empirical fit I. INTRODUCTION The molecular structure and dynamics of macromolecu- lar films

  16. A method for measuring vapor pressures of low-volatility organic aerosol compounds using a thermal desorption particle beam mass spectrometer.

    PubMed

    Chattopadhyay, S; Tobias, H J; Ziemann, P J

    2001-08-15

    A temperature-programmed thermal desorption method for measuring vapor pressures of low-volatility organic aerosol compounds has been developed. The technique employs a thermal desorption particle beam mass spectrometer we have recently developed for real-time composition analysis of organic aerosols. Particles are size selected using a differential mobility analyzer, sampled into a high-vacuum chamber as an aerodynamically focused beam, collected by impaction on a cryogenically cooled surface, slowly vaporized by resistive heating, and analyzed in a quadrupole mass spectrometer. A simple evaporation model developed from the kinetic theory of gases is used to calculate compound vapor pressures over the temperature range of evaporation. The data are fit to a Clausius-Clapeyron equation to obtain a relationship between vapor pressure and temperature and to determine the heat of vaporization. The technique has been evaluated using C13-C18 monocarboxylic and C6-C8 dicarboxylic acids, which have vapor pressures at 25 degrees C of approximately 10(-4) - 10(-6) Pa, but less volatile compounds can also be analyzed. The method is relatively simple and rapid and yields vapor pressures and heats of vaporization that are in good agreement with literature values. The technique will be used to generate a new database of vapor pressures for low-volatility atmospheric organic compounds. PMID:11534699

  17. Geothermal low-temperature reservoir assessment program: A new DOE geothermal initiative

    SciTech Connect

    Wright, P.M.; Lienau, P.J.; Mink, L.L.

    1992-08-01

    In Fiscal Year 1991, Congress appropriated money for the Department of Energy to begin a new program in the evaluation and use of low- and moderate-temperature geothermal resources. The objective of this program is to promote accelerated development of these resources to offset fossil-fuel use and help improve the environment. The program will consist of several components, including: (1) compilation of all available information on resource location and characteristics, with emphasis on resources located within 5 miles of population centers; (2) development and testing of techniques to discover and evaluate low- and moderate-temperature geothermal resources; (3) technical assistance to potential developers of low- and moderate-temperature geothermal resources; and (4) evaluation of the use of geothermal heat pumps in domestic and commercial applications. Program participants will include the Geo-Heat Center at the Oregon Institute of Technology, the University of Utah Research Institute, the Idaho Water Resources Research Institute and agencies of state governments in most of the western states.

  18. Thermal Desorption/GCMS Analysis of Astrobiologically Relevant Organic Materials

    NASA Technical Reports Server (NTRS)

    McDonald, Gene D.

    2001-01-01

    Several macromolecular organic materials, both biologically-derived (type II kerogen and humic acid) and abiotic in origin (Murchison insoluble organic material, cyanide polymer, and Titan tholin) were subjected to thermal desorption using a Chromatoprobe attachment on a Varian Saturn 2000 GCMS system. Each sample was heated sequentially at 100, 200, and 300 C to release volatile components. The evolved compounds were then separated on a Supelco EC-1 dimethylsilica GC column and detected by the Saturn 2000 ion trap mass spectrometer. The various types of macromolecular organic material subjected to thermal desorption produced distinctly different GCMS chromatograms at each temperature, containing fractions of both low and high chromatographic mobility. The relative amounts of detectable volatiles released at each temperature also differed, with type II kerogen and cyanide polymer containing the highest percentage of low-temperature components. In all the samples, the highest yield of released compounds occurred at 300 C. Only cyanide polymer evolved a homologous hydrocarbon series, suggesting that it is the only material among those examined that contains a truly polymeric structure. Pyrolysis/gas chromatography/mass spectrometry has been used extensively for analysis of terrestrial organic macromolecular materials, and was also part of the instrument package on the Viking landers. Thorough analysis by pyrolysis usually employs temperatures of 500 C or higher, which for in situ analyses can be problematic given spacecraft power and materials constraints. This study demonstrates that heating of organic materials of astrobiological relevance to temperatures as low as 200-300 C for short periods releases volatile components that can be analyzed by gas chromatography and mass spectrometry. Even in the absence of full pyrolysis, useful chemical information on samples can be obtained, and materials from different biological and abiological sources can be distinguished. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  19. NMR study of the adsorption-desorption kinetics of dissolved tetraalanine in MCM-41 mesoporous material.

    PubMed

    Pizzanelli, Silvia; Kababya, Shifi; Frydman, Veronica; Landau, Miron; Vega, Shimon

    2005-04-28

    In this study we show how deuterium magic-angle spinning NMR spectroscopy can be used to investigate the adsorption-desorption kinetics of molecules in solution at surface-liquid interfaces. An aqueous solution of deuterium-labeled tetraalanine is inserted in the pores of MCM-41 mesoporous material, and its 2H MAS NMR spectrum is measured as a function of temperature and fraction of filling of the pores. Prior to this study, the different types of water in MCM-41 are characterized as a function of water loading of the pores. Analysis of 2H MAS sideband line shapes enabled the determination of the adsorption and desorption rates and the activation energies of desorption. PMID:16851938

  20. Competitive Sorption and Desorption of Chlorinated Organic Solvents (DNAPLs) in Engineered Natural Organic Matter

    SciTech Connect

    Tang, Jixin; Weber, Walter J., Jr.

    2004-03-31

    The effects of artificially accelerated geochemical condensation and maturation of natural organic matter on the sorption and desorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) were studied. The sorption and desorption of TCE in the presence and absence of the competing PCE and 1,2-dichlorobenzene (DCB) were also examined. A sphagnum peat comprising geologically young organic matter was artificially ''aged'' using superheated water, thus increasing the aromaticity and the degree of condensation of its associated organic matter. The sorption of all solutes tested were increased remarkably and their respective desorptions reduced, by the aged peat. The sorption capacities and isotherm nonlinearities of the peat for both TCE and PCE were found to increase as treatment temperature increased. In the competitive sorption studies, both PCE and DCB were found to depress TCE sorption, with PCE having greater effects than DCB, presumably because the molecular structure o f the former is more similar to that of TCE.

  1. Temperature-Programmed Gas-Sensing With Microhotplates: an Opportunity to Enhance Microelectronic Gas Sensor Metrology

    NASA Astrophysics Data System (ADS)

    Geist, Jon; Afridi, Muhammad

    2009-09-01

    It is only recently that the ITRS (International Technical Roadmap for Semiconductors) has identified functional diversification through heterogeneous integration as a key enabler of future industry growth. This paper describes a powerful temperature-programmed gas-sensing technique that has the potential to convert low-cost, integrated, microhotplate-based non-selective, metal-oxide gas sensors into stable, sensitive, and highly selective gas-sensor systems. The paper also points out the importance of heterogeneous integration and temperature sensor stability to support this measurement technique.

  2. Enhanced desorption of 2,4,6 Trinitrotoluene

    E-print Network

    Aturaliye, Upul Anuruddha

    1997-01-01

    requires that the 'TNT be desorbed and transferred into the aqueous phase. The purpose of this research was to study the influence of surfactants on the desorption of TNT. Furthermore, a comparison of the desorption enhancement capabilities of synthetic...

  3. High-temperature turbine technology program. Turbine subsystem design report: Low-Btu gas

    SciTech Connect

    Horner, M.W.

    1980-12-01

    The objective of the US Department of Energy High-Temperature Turbine Technology (DOE-HTTT) program is to bring to technology readiness a high-temperature (2600/sup 0/F to 3000/sup 0/F firing temperature) turbine within a 6- to 10-year duration, Phase II has addressed the performance of component design and technology testing in critical areas to confirm the design concepts identified in the earlier Phase I program. Based on the testing and support studies completed under Phase II, this report describes the updated turbine subsystem design for a coal-derived gas fuel (low-Btu gas) operation at 2600/sup 0/F turbine firing temperature. A commercial IGCC plant configuration would contain four gas turbines. These gas turbines utilize an existing axial flow compressor from the GE product line MS6001 machine. A complete description of the Primary Reference Design-Overall Plant Design Description has been developed and has been documented. Trends in overall plant performance improvement at higher pressure ratio and higher firing temperature are shown. It should be noted that the effect of pressure ratio on efficiency is significally enhanced at higher firing temperatures. It is shown that any improvement in overall plant thermal efficiency reflects about the same level of gain in Cost of Electricity (COE). The IGCC concepts are shown to be competitive in both performance and cost at current and near-term gas turbine firing temperatures of 1985/sup 0/F to 2100/sup 0/F. The savings that can be accumulated over a thirty-year plant life for a water-cooled gas turbine in an IGCC plant as compared to a state-of-the-art coal-fired steam plant are estimated. A total of $500 million over the life of a 1000 MW plant is projected. Also, this IGCC power plant has significant environmental advantages over equivalent coal-fired steam power plants.

  4. Generation IV Reactors Integrated Materials Technology Program Plan: Focus on Very High Temperature Reactor Materials

    Microsoft Academic Search

    William R Corwin; Timothy D Burchell; Yutai Katoh; Timothy E McGreevy; Randy K Nanstad; Weiju Ren; Lance Lewis Snead; Dane F Wilson

    2008-01-01

    Since 2002, the Department of Energy's (DOE's) Generation IV Nuclear Energy Systems (Gen IV) Program has addressed the research and development (R&D) necessary to support next-generation nuclear energy systems. The six most promising systems identified for next-generation nuclear energy are described within this roadmap. Two employ a thermal neutron spectrum with coolants and temperatures that enable hydrogen or electricity production

  5. High temperature gas turbine engine component materials testing program: Task I. Annual report for 1977

    Microsoft Academic Search

    Sims

    1978-01-01

    The objective of this program is to provide a data base for performance of gas turbine nozzle and bucket materials in coal-derived liquid (CDL) and low-Btu gas environments at temperatures up to 2200°F. This report covers accomplishments during the year 1977, the last 12 months of the 30 month effort. Activity consists of ''Initial Tests'' to define the problems, ''Screening

  6. The potential for and challenges of detecting chemical hazards with temperature-programmed microsensors

    Microsoft Academic Search

    D. C. Meier; J. K. Evju; Z. Boger; B. Raman; K. D. Benkstein; C. J. Martinez; C. B. Montgomery; S. Semancik

    2007-01-01

    Several recent demonstrations of the abilities of micro-electromechanical systems (MEMS)-based microsensor technology to detect hazardous compounds and their simulants in a variety of background conditions are presented. In each case, two pairs of conductometric metal oxide sensors (TiO2 and SnO2) produced via chemical vapor deposition are operated using temperature-programmed sensing (TPS). NIST microdevices can utilize this operating mode to sample

  7. High performance ²?²Cf plasma desorption mass spectrometry 

    E-print Network

    McIntire, Thomas Shane

    1991-01-01

    Track and the Dissemination of Energy. . . 4. The Desorption-Ionization Mechanism Thesis Objectives 1. Instrumental Design Improvements. . . . . . . . . . . 2. Mass Calibration and Accuracy Acceleration Systems . . . . . . . . . , 1. Grid.... Operating the EPG in the Pulsed Deflection Mode . 3. Operating the EPG in the Pulsed Transmission Mode F. Gridless Acceleration Electrode System . G. Calibration and Mass Accuracy . 1. Calibration Methods . 2. Selection of Calibration Ions 3. TOF...

  8. Improved micromachined column design and fluidic interconnects for programmed high-temperature gas chromatography separations.

    PubMed

    Gaddes, David; Westland, Jessica; Dorman, Frank L; Tadigadapa, Srinivas

    2014-07-01

    This work focuses on the development and experimental evaluation of micromachined chromatographic columns for use in a commercial gas chromatography (GC) system. A vespel/graphite ferrule based compression sealing technique is presented using which leak-proof fluidic interconnection between the inlet tubing and the microchannel was achieved. This sealing technique enabled separation at temperatures up to 350°C on a ?GC column. This paper reports the first high-temperature separations in microfabricated chromatographic columns at these temperatures. A 2m microfabricated column using a double Archimedean spiral design with a square cross-section of 100?m×100?m has been developed using silicon microfabrication techniques. The microfabricated column was benchmarked against a 2m 100?m diameter commercial column and the performance between the two columns was evaluated in tests performed under identical conditions. High temperature separations of simulated distillation (ASTM2887) and polycyclic aromatic hydrocarbons (EPA8310) were performed using the ?GC column in temperature programmed mode. The demonstrated ?GC column along with the high temperature fixture offers one more solution toward potentially realizing a portable ?GC device for the detection of semi-volatile environmental pollutants and explosives without the thermal limitations reported to date with ?GC columns using epoxy based interconnect technology. PMID:24866564

  9. Desorption of intrinsic cesium from smectite: inhibitive effects of clay particle organization on cesium desorption.

    PubMed

    Fukushi, Keisuke; Sakai, Haruka; Itono, Taeko; Tamura, Akihiro; Arai, Shoji

    2014-09-16

    Fine clay particles have functioned as transport media for radiocesium in terrestrial environments after nuclear accidents. Because radiocesium is expected to be retained in clay minerals by a cation-exchange reaction, ascertaining trace cesium desorption behavior in response to changing solution conditions is crucially important. This study systematically investigated the desorption behavior of intrinsic Cs (13 nmol/g) in well-characterized Na-montmorillonite in electrolyte solutions (NaCl, KCl, CaCl2, and MgCl2) under widely differing cation concentrations (0.2 mM to 0.2 M). Batch desorption experiments demonstrated that Cs(+) desorption was inhibited significantly in the presence of the environmental relevant concentrations of Ca(2+) and Mg(2+) (>0.5 mM) and high concentrations of K(+). The order of ability for Cs desorption was Na(+) = K(+) > Ca(2+) = Mg(2+) at the highest cation concentration (0.2 M), which is opposite to the theoretical prediction based on the cation-exchange selectivity. Laser diffraction grain-size analyses revealed that the inhibition of Cs(+) desorption coincided with the increase of the clay tactoid size. Results suggest that radiocesium in the dispersed fine clay particles adheres on the solid phase when the organization of swelling clay particles occurs because of changes in solution conditions caused by both natural processes and artificial treatments. PMID:25144123

  10. On factors controlling activity of submonolayer bimetallic catalysts: Nitrogen desorption

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Vlachos, Dionisios G.

    2014-01-01

    We model N2 desorption on submonolayer bimetallic surfaces consisting of Co clusters on Pt(111) via first-principles density functional theory-based kinetic Monte Carlo simulations. We find that submonolayer structures are essential to rationalize the high activity of these bimetallics in ammonia decomposition. We show that the N2 desorption temperature on Co/Pt(111) is about 100 K higher than that on Ni/Pt(111), despite Co/Pt(111) binding N weaker at low N coverages. Co/Pt(111) has substantially different lateral interactions than single metals and Ni/Pt. The lateral interactions are rationalized with the d-band center theory. The activity of bimetallic catalysts is the result of heterogeneity of binding energies and reaction barriers among sites, and the most active site can differ on various bimetallics. Our results are in excellent agreement with experimental data and demonstrate for the first time that the zero-coverage descriptor, used until now, for catalyst activity is inadequate due not only to lacking lateral interactions but importantly to presence of multiple sites and a complex interplay of thermodynamics (binding energies, occupation) and kinetics (association barriers) on those sites.

  11. On factors controlling activity of submonolayer bimetallic catalysts: nitrogen desorption.

    PubMed

    Guo, Wei; Vlachos, Dionisios G

    2014-01-01

    We model N2 desorption on submonolayer bimetallic surfaces consisting of Co clusters on Pt(111) via first-principles density functional theory-based kinetic Monte Carlo simulations. We find that submonolayer structures are essential to rationalize the high activity of these bimetallics in ammonia decomposition. We show that the N2 desorption temperature on Co?Pt(111) is about 100 K higher than that on Ni?Pt(111), despite Co?Pt(111) binding N weaker at low N coverages. Co?Pt(111) has substantially different lateral interactions than single metals and Ni?Pt. The lateral interactions are rationalized with the d-band center theory. The activity of bimetallic catalysts is the result of heterogeneity of binding energies and reaction barriers among sites, and the most active site can differ on various bimetallics. Our results are in excellent agreement with experimental data and demonstrate for the first time that the zero-coverage descriptor, used until now, for catalyst activity is inadequate due not only to lacking lateral interactions but importantly to presence of multiple sites and a complex interplay of thermodynamics (binding energies, occupation) and kinetics (association barriers) on those sites. PMID:24410233

  12. Thermal desorption mass analysis of carbon fiber surfaces: surface oxygen complexes

    SciTech Connect

    Fagan, D.T.; Kuwana, T.

    1989-05-01

    A thermal desorption mass spectrometry (TDMS) system was constructed and applied to study the removal of adsorbed material and the decomposition of surface oxygen complexes from carbon fiber surfaces. The system consisted of a Balzers QMG 511 quadrupole mass spectrometer contained within a vacuum system employing separate chambers for analysis and adsorption. Carbon fiber samples were heated by direct resistive heating in a linear increase up to 1000/degree/C under high vacuum. An initial desorption of as-received pitch-based fibers produced a variety of carbon-, oxygen-, hydrogen-, and nitrogen-containing fragments, as well as traces of species apparently containing chlorine and sulfur. The initial degassing step served to clean the carbon fibers for subsequent oxidation of the carbon with oxygen to form surface oxygen complexes. Such fibers then subjected to TDMS yielded carbon monoxide, CO, and carbon dioxide, CO/sub 2/ as the major desorption products resulting from the decomposition of the surface carbon-oxygen complexes. The observation of multiple peaks in the desorption rate versus temperature profiles indicates that CO originates from possibly more than four different sites, and CO/sub 2/ from at least two sites. The number of sites and the quantity of CO or CO/sub 2/ produced at each site depended on the time and temperature of the prior oxidative treatment with oxygen. The activation energy for CO/sub 2/ generation from the oxidized carbon surface was determined to be 187 /plus minus/ 13 kJ/mol.

  13. Thermal desorption study of physical forces at the PTFE surface

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Pepper, S. V.

    1987-01-01

    Thermal desorption spectroscopy (TDS) of the polytetrafluoroethylene (PTFE) surface was successfully employed to study the possible role of physical forces in the enhancement of metal-PTFE adhesion by radiation. The thermal desorption spectra were analyzed without assumptions to yield the activation energy for desorption over a range of xenon coverage from less than 0.1 monolayer to more than 100 monolayers. For multilayer coverage, the desorption is zero-order with an activation energy equal to the sublimation energy of xenon. For submonolayer coverages, the order for desorption from the unirradiated PTFE surface is 0.73 and the activation energy for desorption is between 3.32 and 3.36 kcal/mol; less than the xenon sublimation energy. The effect of irradiation is to increase the activation energy for desorption to as high as 4 kcal/mol at low coverage.

  14. Thermal desorption study of physical forces at the PTFE surface

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Pepper, S. V.

    1985-01-01

    Thermal desorption spectroscopy (TDS) of the polytetrafluoroethylene (PTFE) surface was successfully employed to study the possibile role of physical forces in the enhancement of metal-PTFE adhesion by radiation. The thermal desorption spectra were analyzed without assumptions to yield the activation energy for desorption over a range of xenon coverage from less than 0.1 monolayer to more than 100 monolayers. For multilayer coverage, the desorption is zero-order with an activation energy equal to the sublimation energy of xenon. For submonolayer coverages, the order for desorption from the unirradiated PTFE surface is 0.73 and the activation energy for desorption is between 3.32 and 3.36 kcal/mol; less than the xenon sublimation energy. The effect of irradiation is to increase the activation energy for desorption to as high as 4 kcal/mol at low coverage.

  15. The New Weather Radar for America's Space Program in Florida: A Temperature Profile Adaptive Scan Strategy

    NASA Technical Reports Server (NTRS)

    Carey, L. D.; Petersen, W. A.; Deierling, W.; Roeder, W. P.

    2009-01-01

    A new weather radar is being acquired for use in support of America s space program at Cape Canaveral Air Force Station, NASA Kennedy Space Center, and Patrick AFB on the east coast of central Florida. This new radar replaces the modified WSR-74C at Patrick AFB that has been in use since 1984. The new radar is a Radtec TDR 43-250, which has Doppler and dual polarization capability. A new fixed scan strategy was designed to best support the space program. The fixed scan strategy represents a complex compromise between many competing factors and relies on climatological heights of various temperatures that are important for improved lightning forecasting and evaluation of Lightning Launch Commit Criteria (LCC), which are the weather rules to avoid lightning strikes to in-flight rockets. The 0 C to -20 C layer is vital since most generation of electric charge occurs within it and so it is critical in evaluating Lightning LCC and in forecasting lightning. These are two of the most important duties of 45 WS. While the fixed scan strategy that covers most of the climatological variation of the 0 C to -20 C levels with high resolution ensures that these critical temperatures are well covered most of the time, it also means that on any particular day the radar is spending precious time scanning at angles covering less important heights. The goal of this project is to develop a user-friendly, Interactive Data Language (IDL) computer program that will automatically generate optimized radar scan strategies that adapt to user input of the temperature profile and other important parameters. By using only the required scan angles output by the temperature profile adaptive scan strategy program, faster update times for volume scans and/or collection of more samples per gate for better data quality is possible, while maintaining high resolution at the critical temperature levels. The temperature profile adaptive technique will also take into account earth curvature and refraction when geo-locating the radar beam (i.e., beam height and arc distance), including non-standard refraction based on the user-input temperature profile. In addition to temperature profile adaptivity, this paper will also summarize the other requirements for this scan strategy program such as detection of low-level boundaries, detection of anvil clouds, reducing the Cone Of Silence, and allowing for times when deep convective clouds will not occur. The adaptive technique will be carefully compared to and benchmarked against the new fixed scan strategy. Specific environmental scenarios in which the adaptive scan strategy is able to optimize and improve coverage and resolution at critical heights, scan time, and/or sample numbers relative to the fixed scan strategy will be presented.

  16. High-temperature turbine technology program hot-gas path development test. Part II. Testing

    SciTech Connect

    Horner, M.W.

    1982-03-01

    This topical report of the US Department of Energy High-Temperature Turbine Technology (DOE-HTTT) Phase II program presents the results of testing full-scale water-cooled first-stage and second-stage turbine nozzles at design temperature and pressure to verify that the designs are adequate for operation in a full-scale turbine environment. Low-cycle fatigue life of the nozzles was demonstrated by subjecting cascade assemblies to several hundred simulated startup/shutdown turbine cycles. This testing was accomplished in the Hot-Gas Path Development Test Stand (HGPDTS), which is capable of evaluating full-scale combustion and turbine nozzle components. A three-throat cascade of the first-stage turbine nozzle was successfully tested at a nozzle inlet gas temperature of 2630/sup 0/F and a nozzle inlet pressure of 11.3 atmospheres. In addition to steady-state operation at the design firing temperature, the nozzle cascade was exposed to a simulated startup/shutdown turbine cycle by varying the firing temperature. A total of 42 h at the design point and 617 thermal cycles were accumulated during the test periods. First-stage nozzle test results show that measured metal and coolant temperatures correspond well to the predicted design values. This nozzle design has been shown to be fully satisfactory for the application (2600/sup 0/F), with growth capability to 3000/sup 0/F firing temperature. A post-test metallurgical examination of sectioned portions of the tested nozzles shows a totally bonded structure, confirming the test results and attesting to the successful performance of water-cooled composite nozzle hardware.

  17. Thermal Desorption Behavior of AlF3 Formed on Al2O3

    NASA Astrophysics Data System (ADS)

    Watanabe, Morimichi; Iida, Takashi; Akiyama, Keijiro; Ishikawa, Takahiro; Sakai, Hiroaki; Sawabe, Kyoichi; Shobatake, Kosuke

    2003-06-01

    Thermal desorption behaviors of the AlF3 layer formed on Al2O3 in the sample temperature range from Ts = 300 to 930 K have been studied using molecular beam mass spectrometry combined with a time-of-flight (TOF) technique. Fluorine atoms were detected as the desorbed species at sample temperatures of Ts = 625 to 850 K and the intensity was found to be peaked at Ts = 750 K. AlF2 species whose translational temperature Ttr is approximately 100 K lower than Ts were also detected as desorbed species above Ts = 850 K and the intensity increased exponentially as Ts was raised. Based on these results, the desorption behavior of AlF3 species is discussed.

  18. Operable Unit 7-13/14 in situ thermal desorption treatability study work plan

    SciTech Connect

    Shaw, P.; Nickelson, D.; Hyde, R.

    1999-05-01

    This Work Plan provides technical details for conducting a treatability study that will evaluate the application of in situ thermal desorption (ISTD) to landfill waste at the Subsurface Disposal Area (SDA) at the Idaho National Engineering and Environmental Laboratory (INEEL). ISTD is a form of thermally enhanced vapor vacuum extraction that heats contaminated soil and waste underground to raise its temperature and thereby vaporize and destroy most organics. An aboveground vapor vacuum collection and treatment system then destroys or absorbs the remaining organics and vents carbon dioxide and water to the atmosphere. The technology is a byproduct of an advanced oil-well thermal extraction program. The purpose of the ISTD treatability study is to fill performance-based data gaps relative to off-gas system performance, administrative feasibility, effects of the treatment on radioactive contaminants, worker safety during mobilization and demobilization, and effects of landfill type waste on the process (time to remediate, subsidence potential, underground fires, etc.). By performing this treatability study, uncertainties associated with ISTD as a selected remedy will be reduced, providing a better foundation of remedial recommendations and ultimate selection of remedial actions for the SDA.

  19. MATRIX-ASSISTED LASER DESORPTION MASS SPECTROMETRY

    Microsoft Academic Search

    Michael J. Stump; Richard C. Fleming; Wei-Hong Gong; Arwah J. Jaber; Jeffrey J. Jones; Charles W. Surber; Charles L. Wilkins

    2002-01-01

    Matrix-assisted laser desorption\\/ionization (MALDI) mass spectrometry is a technique that has attracted widespread interest since its introduction in 1988. It is primarily implemented using time-of-flight or trapped ion mass analyzers and greatly facilitates determination of molecular weights for biomolecules, polymers, and natural products. Numerous publications on these and related applications have appeared during the past ten years. The present brief

  20. Desorption of hexachlorobiphenyl from selected particulate matter 

    E-print Network

    Rorschach, Reagan Cartwright

    1989-01-01

    . INTRODUCTION Objectives CHAPTER IL LITERATURE REVIEW Gas Transfer Solvent Sublation . . Solid-Liquid Mass Transfer . Desorption Mechanisms . CHAPTER III. METHODS AND MATERIALS . . Experimental Apparatus and Procedure Liquid Scintillation Theory Quench...*Cht ~CItll (Autenrieth, 1986), uansport to the cell-water interface would be a function of molecular diffusion. The proposed interface between the phases has given rise to many theories concerning liquid-gas and liquid-solid mass transfer. Liquid-gas mass...

  1. Plutonium sorption and desorption behavior on bentonite.

    PubMed

    Begg, James D; Zavarin, Mavrik; Tumey, Scott J; Kersting, Annie B

    2015-03-01

    Understanding plutonium (Pu) sorption to, and desorption from, mineral phases is key to understanding its subsurface transport. In this work we study Pu(IV) sorption to industrial grade FEBEX bentonite over the concentration range 10(-7)-10(-16) M to determine if sorption at typical environmental concentrations (?10(-12) M) is the same as sorption at Pu concentrations used in most laboratory experiments (10(-7)-10(-11) M). Pu(IV) sorption was broadly linear over the 10(-7)-10(-16) M concentration range during the 120 d experimental period; however, it took up to 100 d to reach sorption equilibrium. At concentrations ?10(-8) M, sorption was likely affected by additional Pu(IV) precipitation/polymerization reactions. The extent of sorption was similar to that previously reported for Pu(IV) sorption to SWy-1 Na-montmorillonite over a narrower range of Pu concentrations (10(-11)-10(-7) M). Sorption experiments with FEBEX bentonite and Pu(V) were also performed across a concentration range of 10(-11)-10(-7) M and over a 10 month period which allowed us to estimate the slow apparent rates of Pu(V) reduction on a smectite-rich clay. Finally, a flow cell experiment with Pu(IV) loaded on FEBEX bentonite demonstrated continued desorption of Pu over a 12 day flow period. Comparison with a desorption experiment performed with SWy-1 montmorillonite showed a strong similarity and suggested the importance of montorillonite phases in controlling Pu sorption/desorption reactions on FEBEX bentonite. PMID:25574607

  2. Low-temperature thermal properties from the EU testing program for potential ITER insulation

    SciTech Connect

    Broadbent, A.J.; Crozier, J.; Smith, K.D. [Oxford Instruments Special Projects, Oxon (United Kingdom)] [and others

    1997-06-01

    Insulation systems will be a key element in the future construction and impregnation of the coils for the ITER device. The thermal contraction and thermal conductivity of ten different electrical insulation systems are measured at temperatures from 4 K to 300 K. Several insulation systems incorporate an electrical barrier layer. The insulation systems are all based on identical S2-glass with various epoxy resins, some of which are not believed to have been previously used in superconducting coils. In particular resins with a high functionality are investigated, some of which are suitable for Vacuum Pressure Impregnation (VPI). The final results of this program are presented and compared to the results from a benchmark testing program (insulation system based on anhydride cured DGEBA resin and S2 glass). This work is financed by the EU under NET contract ERB 5000 940023 (NET 93-857) within the framework of MR.

  3. Ambient pressure laser desorption and laser-induced acoustic desorption ion mobility spectrometry detection of explosives.

    PubMed

    Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

    2013-11-19

    The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor pressures of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient pressure laser desorption (APLD) and ambient pressure laser-induced acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock wave. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown. PMID:24116702

  4. History of desorption induced by electronic transitions

    NASA Astrophysics Data System (ADS)

    Madey, Theodore E.

    1994-01-01

    Desorption induced by electronic transitions (DIET) encompasses electron- and photon-stimulated desorption (ESD and PSD) of atoms, molecules and ions from surfaces. In this paper, we focus on the key experimental and theoretical developments that have led to a fundamental understanding of DIET processes. We emphasize the effects of ionizing radiation, i.e., electrons and photons with energies ? 10 eV. The first DIET studies were occasioned mainly by the observation of anomalous peaks in mass spectrometers and spurious signals in ionization gauges. These observations were followed in the early 1960's by systematic studies of Redhead, and Menzel and Gomer, who independently proposed a Franck-Condon excitation model for electron-stimulated desorption of ions and neutrals from surfaces. In the years after this seminal work, ESD and PSD developed as fields of active interest to surface scientists. In addition to providing insights into the fundamental mechanisms linking atomic motion and electronic energy dissipation at surfaces, DIET investigations are continuing to impact upon radiation damage processes in areas as diverse as X-ray optics, semiconductor electronics, surface analysis and synthesis of molecules in interplanetary space.

  5. Determination of the oxygen content in superconducting and related cuprates using temperature-programmed reduction

    NASA Astrophysics Data System (ADS)

    Halasz, Istvan; Jen, Hung-Wen; Brenner, Alan; Shelef, Mordecai; Kao, Sendjaja; Simon Ng, K. Y.

    1991-06-01

    The oxygen content and reducibilities of four base metal oxides, six nonconducting cuprates, and three superconducting cuprates were investigated by temperature-programmed reduction (TPR) from 30 to 900°C. It was shown that the copper, bismuth, and thallium ions of these oxides were reduced to the zero valence state. Thus, TPR is a useful technique for determining the actual oxygen stoichiometry of cuprates. For multiphase Bi 2CaSr 2Cu 2O 8+ x and Tl 2CaBa 2Cu 2O 8+ x superconductors pretreated in air, x was found to be 2 ± 0.2 and 1 ± 0.2, respectively. Both values are significantly higher than previously reported. The reduction of superconducting and related cuprates required higher temperatures than CuO, but the reducibility of CuO decreased when it was calcined in air at 940°C. The Bi- and Y-based superconducting cuprates exhibited the lowest reducibility among the samples investigated.

  6. Lead Research and Development Activity for DOE's High Temperature, Low Relative Humidity Membrane Program (Topic 2)

    SciTech Connect

    James Fenton, PhD; Darlene Slattery, PhD; Nahid Mohajeri, PhD

    2012-09-05

    The Department of Energy’s High Temperature, Low Relative Humidity Membrane Program was begun in 2006 with the Florida Solar Energy Center (FSEC) as the lead organization. During the first three years of the program, FSEC was tasked with developing non-Nafion® proton exchange membranes with improved conductivity for fuel cells. Additionally, FSEC was responsible for developing protocols for the measurement of in-plane conductivity, providing conductivity measurements for the other funded teams, developing a method for through-plane conductivity and organizing and holding semiannual meetings of the High Temperature Membrane Working Group (HTMWG). The FSEC membrane research focused on the development of supported poly[perfluorosulfonic acid] (PFSA) – Teflon membranes and a hydrocarbon membrane, sulfonated poly(ether ether ketone). The fourth generation of the PFSA membrane (designated FSEC-4) came close to, but did not meet, the Go/No-Go milestone of 0.1 S/cm at 50% relative humidity at 120 °C. In-plane conductivity of membranes provided by the funded teams was measured and reported to the teams and DOE. Late in the third year of the program, DOE used this data and other factors to decide upon the teams to continue in the program. The teams that continued provided promising membranes to FSEC for development of membrane electrode assemblies (MEAs) that could be tested in an operating fuel cell. FSEC worked closely with each team to provide customized support. A logic flow chart was developed and discussed before MEA fabrication or any testing began. Of the five teams supported, by the end of the project, membranes from two of the teams were easily manufactured into MEAs and successfully characterized for performance. One of these teams exceeded performance targets, while the other requires further optimization. An additional team developed a membrane that shows great promise for significantly reducing membrane costs and increasing membrane lifetime.

  7. Low-Energy Photodesorption and Electron-Stimulated Desorption Mechanisms in Semiconductors.

    NASA Astrophysics Data System (ADS)

    Ekwelundu, Emmanuel Chikelue

    1988-12-01

    The aim of this research is to investigate low energy photodesorption and electron stimulated desorption mechanisms in semiconductors. Silicon, gallium arsenide and cadmium sulfide single crystals were used as representative semiconductors because their band gaps cut across both narrow and wide band gap semiconductors. Their clean surfaces were exposed to different doses of the following gases: O_2, NO, CO, CO_2 and SO_2 at room temperature but under different adsorption conditions. At low 10 ^{-10} torr pressure, the surfaces were irradiated with low energy (also low flux) photons and electrons. The desorbing species from the sample surfaces were monitored by a quadrupole mass spectrometer. CO, CO_2, NO, SO and SO _2 were observed to photodesorb when irradiated with photons. The desorption threshold energies were found to coincide with electron excitations from surface states within the band gap of the semiconductors to conduction band states; followed by thresholds corresponding to excitations across the direct gap. In GaAs and CdS, additional threshold could be traced to excitations from the high electron density of states within the valence band. The photodesorption signal at any wavelength greater than the threshold was found to be proportional to the incident photon flux, supporting a quantum mechanism for the observed photodesorption. The calculated quantum efficiency (yield) of 10^ {-5} to 10^{-4} molecules/photon is consistent with the value for semiconductors. CO^+, CO_2 ^+, C^+, O ^+, SO^+, S ^+, SO^+ and SO _2^+ were observed to desorb when the surfaces were irradiated with electrons in the energy range 0-200 eV. The desorption threshold energies were found to coincide approximately with electron excitations from the core levels of the semiconductors. From the core levels excited, it was possible to define in GaAs and CdS which of the desorbing species was bonded to which atom. The total desorption cross section for the desorbing species was found to be ~10 ^{-18} cm^2. A photodesorption mechanism was postulated for semiconductors which incorporated the photogeneration of holes in both the surface and valence band states, drift of the holes to the surface and the resultant annihilation of the surface localized bonds between the adsorbate and the semiconductor leading to desorption. For Electron Stimulated Desorption (ESD) from GaAs and CdS, our results could be explained using the Auger Stimulated Desorption (ASD) model. This is an extension of Knotek-Feibelman model to covalent and non-maximal valency systems. Our ESD results from silicon shows Menzel-Gomer -Redhead (MGR) and ASD models as the competitive desorption models.

  8. Temperature-programmed technique accompanied with high-throughput methodology for rapidly searching the optimal operating temperature of MOX gas sensors.

    PubMed

    Zhang, Guozhu; Xie, Changsheng; Zhang, Shunping; Zhao, Jianwei; Lei, Tao; Zeng, Dawen

    2014-09-01

    A combinatorial high-throughput temperature-programmed method to obtain the optimal operating temperature (OOT) of gas sensor materials is demonstrated here for the first time. A material library consisting of SnO2, ZnO, WO3, and In2O3 sensor films was fabricated by screen printing. Temperature-dependent conductivity curves were obtained by scanning this gas sensor library from 300 to 700 K in different atmospheres (dry air, formaldehyde, carbon monoxide, nitrogen dioxide, toluene and ammonia), giving the OOT of each sensor formulation as a function of the carrier and analyte gases. A comparative study of the temperature-programmed method and a conventional method showed good agreement in measured OOT. PMID:25090138

  9. Catalytic oxidation of propylene--7. Use of temperature programmed reoxidation to characterize. gamma. -bismuth molybdate

    SciTech Connect

    Uda, T.; Lin, T.T.; Keulks, G.W.

    1980-03-01

    Temperature-programed reoxidation of propylene-reduced ..gamma..-Bi/sub 2/MoO/sub 6/ revealed a low-temperature peak (LTP) at 158/sup 0/C and a high-temperature peak (HTP) at 340/sup 0/C. Auger spectroscopy and X-ray diffraction of reduced and partially or completely reoxidized bismuth molybdate showed that at the LTP, molybdenum(IV) is oxidized to molybdenum(VI) and bismuth, from the metallic state to an oxidation state between zero and three, and that the HTP is associated with the complete oxidation of bismuth to bismuth(III). Activity tests for propylene oxidation showed lower acrolein formation on the catalyst, on which only the LTP was reoxidized than on catalysts on which both peaks were reoxidized. The reoxidation kinetics of the catalyst under conditions corresponding to the LTP showed an activation energy of 22.9 kcal/mole below 170/sup 0/C and near zero above 170/sup 0/C; the break in the Arrhenius plot of reoxidation of the catalyst under conditions corresponding to the HTP was at 400/sup 0/C, with activation energies of 46 kcal/mole at lower and near zero at higher temperatures. Propylene oxidation was apparently rate-limited by the HTP reoxidation process below 400/sup 0/C and by allylic hydrogen abstraction above 400/sup 0/C.

  10. Interactions of N2O5 and related nitrogen oxides with ice surfaces: desorption kinetics and collision dynamics.

    PubMed

    Romero Lejonthun, Liza S E; Andersson, Patrik U; Hallquist, Mattias; Thomson, Erik S; Pettersson, Jan B C

    2014-11-26

    The detailed interactions of nitrogen oxides with ice are of fundamental interest and relevance for chemistry in cold regions of the atmosphere. Here, the interactions of NO, NO2, N2O4, and N2O5 with ice surfaces at temperatures between 93 and 180 K are investigated with molecular beam techniques. Surface collisions are observed to result in efficient transfer of kinetic energy and trapping of molecules on the ice surfaces. NO and NO2 rapidly desorb from pure ice with upper bounds for the surface binding energies of 0.16 ± 0.02 and 0.26 ± 0.03 eV, respectively. Above 150 K, N2O4 desorption follows first-order kinetics and is well described by the Arrhenius parameters Ea = 0.39 ± 0.04 eV and A = 10((15.4±1.2)) s(-1), while a stable N2O4 adlayer is formed at lower temperatures. A fraction of incoming N2O5 reacts to form HNO3 on the ice surface. The N2O5 desorption rates are substantially lower on pure water ice (Arrhenius parameters: Ea = 0.36 ± 0.02 eV; A = 10((15.3±0.7)) s(-1)) than on HNO3-covered ice (Ea = 0.24 ± 0.02 eV; A = 10((11.5±0.7)) s(-1)). The N2O5 desorption kinetics also sensitively depend on the sub-monolayer coverage of HNO3, with a minimum in N2O5 desorption rate at a low but finite coverage of HNO3. The studies show that none of the systems with resolvable desorption kinetics undergo ordinary desorption from ice, and instead desorption likely involves two or more surface states, with additional complexity added by coadsorbed molecules. PMID:25139130

  11. Size-dependent kinetic enhancement in hydrogen absorption and desorption of the Li-Mg-N-H system.

    PubMed

    Liu, Yongfeng; Zhong, Kai; Luo, Kun; Gao, Mingxia; Pan, Hongge; Wang, Qidong

    2009-02-11

    High operating temperature and slow kinetics retard the practical applications of the Li-Mg-N-H system for hydrogen storage. To alleviate these problems, a first attempt was carried out by synthesizing Li(2)MgN(2)H(2) through sintering a mixture of Mg(NH(2))(2)-2LiNH(2) and investigating its size-dependent hydrogen storage performance. A dramatically enhanced kinetics for hydrogen absorption/desorption was achieved with a reduction in the particle size. For the dehydrogenation reaction, a three-dimensional diffusion-controlled kinetic mechanism was identified for the first time by analyzing isothermal hydrogen desorption curves with a linear plot method. The experimental improvement and mechanistic understanding on the dehydrogenation kinetics of the Li-Mg-N-H system shed light on how to further decrease the operating temperature and enhance the hydrogen absorption/desorption rate of the amide/hydride combined materials. PMID:19191702

  12. Measurements and analysis of water adsorption and desorption

    SciTech Connect

    Monazam, E.R. [West Virginia Univ., Morgantown, WV (United States); Shadle, L.J. [Morgantown Energy Technology Center, Morgantown, WV (United States); Schroeder, K. [Pittsburgh Energy Technology Center, Pittsburgy, PA (United States)

    1996-02-01

    An investigation was carried out on the adsorption and desorption of moisture in chars of low rank coal. Equilibrium moisture sorptions of dry and moist chars were measured at room temperature and relative humidity of 30% and 80%. Based on these measurements, a novel mathematical model was developed to predict both the rate and the level of hydration for coals and chars. The formulation uses a shrinking core model which required only the measurement of the adsorbing material`s equilibrium moisture content at different temperatures and humidities. The model was validated against experimental and literature data. It accurately and reliably predicted both the rate and extent of hydration and dehydration for coals and char. Using this model, the effects of varying temperatures, relative humidities, and size of the particles and coal pile were simulated. The sensitivity study demonstrated that, as expected, relative humidity and temperature had strong effects on both the rate of hydration and-the equilibrium moisture of coal or char. The particle size dramatically influenced the rate of hydration, but had no affect on the equilibrium moisture content. This model can be used effectively to simulate the impact of moisture on drying, storage, and spontaneous combustion of coals and coal-derived chars.

  13. Shell/METC high-temperature, high-pressure filtration program

    SciTech Connect

    Salter, J.A.; Rockey, J.M.

    1995-12-31

    The purpose of this paper is to present the program objectives and non-proprietary results of the high temperature, high pressure filtration work done under the Shell/METC Cooperative Research and Development Agreement (CRADA) 93-011. The primary purpose of this CRADA was to collect data relevant to the design and operation of dry particulate solids filters employing rigid ceramic (silicon carbide) filter elements in a gasifying environment at conditions of commercial interest; e.g., temperatures up to 1100 {degrees}F and system pressures between 300 and 350 psia. Shell provided the ceramic filter elements and evaluated the exposed filter elements. METC installed the filter elements and operated their 10 inch Fluid Bed Gasification and Cleanup facility as required for their Hot Gas Clean-up Test Program. Filter elements were removed from service after approximately 254, 525 and 868 hours of on-line operation. The exposed filter elements were analyzed and compared to an unexposed element with respect to changes in physical property.

  14. A hot hole-programmed and low-temperature-formed SONOS flash memory.

    PubMed

    Chang, Yuan-Ming; Yang, Wen-Luh; Liu, Sheng-Hsien; Hsiao, Yu-Ping; Wu, Jia-Yo; Wu, Chi-Chang

    2013-01-01

    In this study, a high-performance TixZrySizO flash memory is demonstrated using a sol-gel spin-coating method and formed under a low annealing temperature. The high-efficiency charge storage layer is formed by depositing a well-mixed solution of titanium tetrachloride, silicon tetrachloride, and zirconium tetrachloride, followed by 60 s of annealing at 600°C. The flash memory exhibits a noteworthy hot hole trapping characteristic and excellent electrical properties regarding memory window, program/erase speeds, and charge retention. At only 6-V operation, the program/erase speeds can be as fast as 120:5.2 ?s with a 2-V shift, and the memory window can be up to 8 V. The retention times are extrapolated to 106 s with only 5% (at 85°C) and 10% (at 125°C) charge loss. The barrier height of the TixZrySizO film is demonstrated to be 1.15 eV for hole trapping, through the extraction of the Poole-Frenkel current. The excellent performance of the memory is attributed to high trapping sites of the low-temperature-annealed, high-? sol-gel film. PMID:23899050

  15. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Final report

    SciTech Connect

    Chunshan Song; Schobert, H.H.; Parfitt, D.P. [and others

    1997-11-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on exploring novel bimetallic dispersed catalysts for coal liquefaction and the effectiveness of temperature-programmed liquefaction using dispersed catalysts. The primary objective of this research was to explore novel bimetallic dispersed catalysts from organometallic molecular precursors, that could be used in low concentrations but exhibit relatively high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. We have synthesized and tested various catalyst precursors in liquefaction of subbituminous and bituminous coals and in model compound studies to examine how do the composition and structure of the catalytic precursors affect their effectiveness for coal liquefaction under different reaction conditions, and how do these factors affect their catalytic functions for hydrogenation of polyaromatic hydrocarbons, for cleavage of C-C bonds in polycyclic systems such as 4-(1-naphthylmethyl)bibenzyl, for hydrogenolysis of C-O bond such as that in dinaphthylether, for hydrodeoxygenation of phenolic compounds and other oxygen-containing compounds such as xanthene, and for hydrodesulfurization of polycyclic sulfur compounds such as dibenzothiophene. The novel bimetallic and monometallic precursors synthesized and tested in this project include various Mo- and Fe-based compounds.

  16. Sorption and desorption behaviors of diuron in soils amended with charcoal.

    PubMed

    Yu, Xiang-Yang; Ying, Guang-Guo; Kookana, Rai S

    2006-11-01

    Charcoal derived from the partial combustion of vegetation is ubiquitous in soils and sediments and can potentially sequester organic contaminants. To examine the role of charcoal in the sorption and desorption behaviors of diuron pesticide in soil, synthetic charcoals were produced through carbonization of red gum (Eucalyptus spp.) wood chips at 450 and 850 degrees C (referred to as charcoals BC450 and BC850, respectively, in this paper). Pore size distribution analyses revealed that BC850 contained mainly micropores (pores approximately 0.49 nm mean width), whereas BC450 was essentially not a microporous material. Short-term equilibration (< 24 h) tests were conducted to measure sorption and desorption of diuron in a soil amended with various amounts of charcoals of both types. The sorption coefficients, isotherm nonlinearity, and apparent sorption-desorption hysteresis markedly increased with increasing content of charcoal in the soil, more prominently in the case of BC850, presumably due to the presence of micropores and its relatively higher specific surface area. The degree of apparent sorption-desorption hystersis (hysteresis index) showed a good correlation with the micropore volume of the charcoal-amended soils. This study indicates that the presence of small amounts of charcoal produced at high temperatures (e.g., interior of wood logs during a fire) in soil can have a marked effect on the release behavior of organic compounds. Mechanisms of this apparent hysteretic behavior need to be further investigated. PMID:17061832

  17. Desorption of arsenic from exhaust activated carbons used for water purification.

    PubMed

    Di Natale, F; Erto, A; Lancia, A

    2013-09-15

    This work aims to the analysis of arsenic desorption from an exhaust activated carbon used for the purification of a natural water. This last was used to mimic the properties of common groundwater or drinking water. Different low-cost and harmless eluting solutions were considered, including distilled water, natural water, saline (NaCl, CaCl? and NaNO?) and basic (NaOH) solutions. Experimental results showed that, for 1g of activated carbon with arsenic loading close to the maximum value available for the model natural water (? ? 0.1 mg/g), it is possible to recover more than 80% of the arsenic using 20 ml of 0.1 M sodium chloride solution. A temperature variation within 20 and 40 °C has scarce effect on desorption efficiency. A comparison between desorption data and adsorption isotherms data suggests that arsenic adsorption is actually a reversible process. Therefore, it is virtually possible to increase arsenic recovery efficiency close to 100% by increasing the NaCl concentration or the volume of the desorption solution, but a preliminary cost benefit analysis lead to consider a NaCl 0.1M solution as an optimal solution for practical applications. PMID:23811366

  18. The structure and desorption properties of the ammines of the group II halides

    NASA Astrophysics Data System (ADS)

    Jones, Martin Owen; Royse, David M.; Edwards, Peter P.; David, William I. F.

    2013-12-01

    The synthesis of the magnesium halide ammines (Mg(NH3)6Cl2, Mg(NH3)6Br2 and Mg(NH3)6I2) is reported and their structures are identified by high resolution X-ray diffraction. The structures of Mg(NH3)6Br2 and Mg(NH3)6I2 are reported for the first time. The desorption properties of Mg(NH3)6Cl2, Mg(NH3)6Br2 and Mg(NH3)6I2 are examined by thermogravimetric analysis and NMR, and the trends in desorption properties as a function of composition are interpreted using a simple ionic model. It is found that the desorption properties are dependent on the lattice enthalpy of the intermediate and final phases Mg(NH3)2X2, Mg(NH3)X2 and MgX2, that the anion has limited effect on the state of Mg-N bonding and that the desorption temperature of ionic ammines may be tuned by varying the size of the anion.

  19. Sticking and desorption of hydrogen on graphite: A comparative study of different models

    PubMed Central

    Lepetit, Bruno; Lemoine, Didier; Medina, Zuleika; Jackson, Bret

    2011-01-01

    We study the physisorption of atomic hydrogen on graphitic surfaces with four different quantum mechanical methods: perturbation and effective Hamiltonian theories, close coupling wavepacket, and reduced density matrix propagation methods. Corrugation is included in the modeling of the surface. Sticking is a fast process which is well described by all methods. Sticking probabilities are of the order of a few percent in the collision energy range 0–25 meV, but are enhanced for collision energies close to those of diffraction resonances. Sticking also increases with surface temperature. Desorption is a slow process which involves multiphonon processes. We show, however, how to correct the close coupling wavepacket method to account for such phenomena and obtain correct time constants for initial state decay. Desorption time constants are in the range of 20–50 ps for a surface temperature of 300 K. PMID:21428654

  20. Experimental study and modelling of adsorption and desorption isotherms of prickly pear peel ( Opuntia ficus indica)

    Microsoft Academic Search

    S Lahsasni; M Kouhila; M Mahrouz; N Kechaou

    2002-01-01

    Moisture equilibrium data for adsorption and desorption of water from prickly pear peel (Opuntia ficus indica) were investigated at temperatures in the range of 30–50 °C and water activity ranging from 0.05 to 0.9. The experimental procedure used was based on the gravimetric static method. The experimental curves of sorption are then described by GAB, Henderson’s and BET models. The

  1. Plasma desorption mass spectrometry of organics at low temperatures 

    E-print Network

    Shirey, Eldon Lynn

    1993-01-01

    , cyclohexane, cyclohexene, 1,3-cyclohexadiene, benzene, toluene, ortho- xylene, meta-xylene, and para-xylene. PDMS is best carried out on solids; accordingly, the samples were frozen. The experiments were run using a time-of-flight mass spectrometer with a 252...

  2. MAGMIX: a basic program to calculate viscosities of interacting magmas of differing composition, temperature, and water content

    USGS Publications Warehouse

    Frost, T.P.; Lindsay, J.R.

    1988-01-01

    MAGMIX is a BASIC program designed to predict viscosities at thermal equilibrium of interacting magmas of differing compositions, initial temperatures, crystallinities, crystal sizes, and water content for any mixing proportion between end members. From the viscosities of the end members at thermal equilibrium, it is possible to predict the styles of magma interaction expected for different initial conditions. The program is designed for modeling the type of magma interaction between hypersthenenormative magmas at upper crustal conditions. Utilization of the program to model magma interaction at pressures higher than 200 MPa would require modification of the program to account for the effects of pressure on heat of fusion and magma density. ?? 1988.

  3. Progressive Thermal Desorption of Vapor Mixtures from a Preconcentrator with a Porous Metal Foam Internal Architecture and Variable Thermal Ramp Rates

    SciTech Connect

    Grate, Jay W.; Anheier, Norman C.; Baldwin, David L.

    2005-03-15

    A vapor preconcentrator has been designed with the porous polymer (Tenax) packed into a highly porous metal foam to facilitate thermal conductivity and temperature uniformity throughout the bed of the preconcentrator during heating. Vapors were desorbed using linear temperature programming from room temperature to a maximum temperature of 170ºC or 200ºC; the programmed duration of the thermal ramp was varied from 10 to 180 seconds. The thermal desorption of vapor mixtures captured on the preconcentrator has been examined in detail, using methyl ethyl ketone, toluene, and dimethyl methylphosphonate as a test mixture. Vapors desorbed as a sequence of partially separated overlapping peaks as observed with a polymer-coated flexural plate wave sensor. It was shown that vapor mixture resolution improved as the total time of the thermal ramp was extended from 30 seconds to 120 seconds. In this way the preconcentrator serves to act as a preseparator in addition to its usual functions for sampling, signal modulation, and improving sensitivity. Overlapping peaks were modeled and peak areas were extracted using an exponentially modified Gaussian model. Peak areas were independent of the thermal ramp rate. Uses of such preconcentrators with multivariate detectors such as sensor arrays are discussed.

  4. Mass spectrometric study of high-temperature dehydroxylation of disperse silicas and the interpretation of their IR spectra in the region of SiO stretching vibrations

    Microsoft Academic Search

    V. A. Nazarenko; V. I. Furman; A. G. Guzikevich; Yu. I. Gorlov

    1985-01-01

    Field-desorption mass spectrometry has been used to determine the lower boundary of the temperature interval for the removal of surface hydroxyl groups ofaerosil. Both in the regime of cation desorption and in the regime of anion desorption, at temperatures above 900°K, OH ions of the corresponding sign are registered. It is concluded that the thermal decomposition of the surface bonds

  5. Analytical theory of finite-size effects in mechanical desorption of a polymer chain.

    PubMed

    Skvortsov, A M; Klushin, L I; Fleer, G J; Leermakers, F A M

    2010-02-14

    We discuss a unique system that allows exact analytical investigation of first- and second-order transitions with finite-size effects: mechanical desorption of an ideal lattice polymer chain grafted with one end to a solid substrate with a pulling force applied to the other end. We exploit the analogy with a continuum model and use accurate mapping between the parameters in continuum and lattice descriptions, which leads to a fully analytical partition function as a function of chain length, temperature (or adsorption strength), and pulling force. The adsorption-desorption phase diagram, which gives the critical force as a function of temperature, is nonmonotonic and gives rise to re-entrance. We analyze the chain length dependence of several chain properties (bound fraction, chain extension, and heat capacity) for different cross sections of the phase diagram. Close to the transition a single parameter (the product of the chain length N and the deviation from the transition point) describes all thermodynamic properties. We discuss finite-size effects at the second-order transition (adsorption without force) and at the first-order transition (mechanical desorption). The first-order transition has some unusual features: The heat capacity in the transition region increases anomalously with temperature as a power law, metastable states are completely absent, and instead of a bimodal distribution there is a flat region that becomes more pronounced with increasing chain length. The reason for this anomaly is the absence of an excess surface energy for the boundary between adsorbed and stretched coexisting phases (this boundary is one segment only): The two states strongly fluctuate in the transition point. The relation between mechanical desorption and mechanical unzipping of DNA is discussed. PMID:20151736

  6. High temperature experiments on a 4 tons UF6 container TENERIFE program

    SciTech Connect

    Casselman, C.; Duret, B.; Seiler, J.M.; Ringot, C.; Warniez, P.

    1991-12-31

    The paper presents an experimental program (called TENERIFE) whose aim is to investigate the behaviour of a cylinder containing UF{sub 6} when exposed to a high temperature fire for model validation. Taking into account the experiments performed in the past, the modelization needs further information in order to be able to predict the behaviour of a real size cylinder when engulfed in a 800{degrees}C fire, as specified in the regulation. The main unknowns are related to (1) the UF{sub 6} behaviour beyond the critical point, (2) the relationship between temperature field and internal pressure and (3) the equivalent conductivity of the solid UF{sub 6}. In order to investigate these phenomena in a representative way it is foreseen to perform experiments with a cylinder of real diameter, but reduced length, containing 4 tons of UF{sub 6}. This cylinder will be placed in an electrically heated furnace. A confinement vessel prevents any dispersion of UF{sub 6}. The heat flux delivered by the furnace will be calibrated by specific tests. The cylinder will be changed for each test.

  7. Determination of the oxygen content in superconducting and related cuprates using temperature-programmed reduction

    SciTech Connect

    Halasz, I.; Jen, Hungwen; Brenner, A.; Kao, Sendjaja; Ng K.Y.S. (Wayne State Univ., Detroit, MI (United States)); Shelef, M. (Ford Motor Co., Dearborn, MI (United States))

    1991-06-01

    The oxygen content and reducibilities of four base metal oxides, six nonconducting cuprates, and three superconducting cuprates were investigated by temperature-programmed reduction (TPR) from 30 to 900C. It was shown that the copper, bismuth, and thallium ions of these oxides were reduced to the zero valence state. Thus, TPR is a useful technique for determining the actual oxygen stoichiometry of cuprates. For multiphase Bi{sub 2}CaSr{sub 2}Cu{sub 2}O{sub 8+x} and Tl{sub 2}CaBa{sub 2}Cu{sub 2}O{sub 8+x} superconductors pretreated in air, x was found to be 2 {plus minus} 0.2 and 1 {plus minus} 0.2, respectively. Both values are significantly higher than previously reported. The reduction of superconducting and related cuprates required higher temperatures than CuO, but the reducibility of CuO decreased when it was calcined in air at 940C. The Bi- and Y-based superconducting cuprates exhibited the lowest reducibility among the samples investigated.

  8. SOFT LASER DESORPTION IONIZATION -MALDI, DIOS AND NANOSTRUCTURES

    E-print Network

    Vertes, Akos

    Chapter 20 SOFT LASER DESORPTION IONIZATION - MALDI, DIOS AND NANOSTRUCTURES Akos Veites Department desorption ionization (MALDI). In this method, the sample is mixed with an organic matrix that efficiently the mass spectrometric determination of their accurate mass. The combination of MALDI with mass

  9. The regeneration characteristics of various red mud granular adsorbents (RMGA) for phosphate removal using different desorption reagents.

    PubMed

    Zhao, Yaqin; Yue, Qinyan; Li, Qian; Gao, Baoyu; Han, Shuxin; Yu, Hui

    2010-10-15

    In this research, various red mud granular adsorbents (RMGA), which were made from red mud--a kind of waste residue from the alumina industry, were manufactured under different sintering temperatures (ST). For the purpose of investigating the regeneration characteristics of them for phosphate removal, systematic experiments were carried out, including adsorption, desorption (using different desorption reagents) and resorption tests. When RMGA were desorbed by HCl solutions, the desorption efficiencies were relatively higher due to acid erosion, but the corresponding resorption capacities became small owing to extraction of effective components. Although RMGA rarely released phosphate in desorption process when being desorbed by deionised water, it performed well on resorption of phosphate afterwards. It was assumed that the lower pH in resorption process, which was caused by the reductive release of CaO into solution, contributed to a weaker competition of OH(-) on phosphate resorption. When NaOH solution was employed as the desorption reagent, resorption capacities of RMGA were relatively larger and increased with the increase of NaOH concentration, because OH(-) might ameliorate the chemical composition on the surface of RMGA potentially. In addition, several RMGA manufactured under lower ST obtained larger resorption capacities than their original adsorption capacities, because of the comparatively unstable crystal structure which led to a stronger amelioration on them. PMID:20615614

  10. Heavy-ion-induced desorption yields of cryogenic surfaces bombarded with 1.4MeV/u xenon ions

    NASA Astrophysics Data System (ADS)

    Holzer, Donat Philipp; Mahner, Edgar; Kollmus, Holger; Bender, Markus; Severin, Daniel; Wengenroth, Marc

    2013-08-01

    Heavy-ion-induced desorption of two different cryogenic targets was studied with a new experimental setup installed at the GSI High Charge State Injector. One gold-coated and one amorphous-carbon-coated copper target, bombarded under perpendicular impact with 1.4MeV/u Xe18+ ions, were tested. Partial pressure rises of H2, CO, CO2, and CH4 and effective desorption yields were measured at 300, 77, and 8 K using continuous heavy-ion bombardment. We found that the desorption yields decrease with decreasing target temperature and measured the yield rises as a function of CO gas cryosorbed at 8 K. In this paper we describe the experimental system comprising a new cryogenic target assembly, the preparation of the targets, the test procedure, and the evaluation of the effective pumping speed of the setup. Pressure rise and gas adsorption experiments are described; the obtained results are discussed and compared with literature data.

  11. Temperature

    NASA Technical Reports Server (NTRS)

    Berenson, P. J.; Robertson, W. G.

    1973-01-01

    The problems in human comfort in heat stress are emphasized, with less emphasis placed upon cold exposure problems. Physiological parameters related to human thermal interactions are discussed, as well as data concerning thermal protective clothing. The energy balance equation, heat transfer equation, thermal comfort, heat stress, and cold stress are also considered. A two node model of human temperature regulation in FORTRAN is appended.

  12. Impact of molecular clustering inside nanopores on desorption processes.

    PubMed

    Tsotsalas, Manuel; Hejcik, Pavel; Sumida, Kenji; Kalay, Ziya; Furukawa, Shuhei; Kitagawa, Susumu

    2013-03-27

    Understanding the sorption kinetics of nanoporous systems is crucial for the development and design of novel porous materials for practical applications. Here, using a porous coordination polymer/quartz crystal microbalance (PCP/QCM) hybrid device, we investigate the desorption of various vapor molecules featuring different degrees of intermolecular (hydrogen bonding) or molecule-framework interactions. Our findings reveal that strong intermolecular interactions lead to the desorption process proceeding via an unprecedented metastable state, wherein the guest molecules are clustered within the pores, causing the desorption rate to be temporarily slowed. The results demonstrate the considerable impact of the chemical nature of an adsorbate on the kinetics of desorption, which is also expected to influence the efficiency of certain processes, such as desorption by gas purge. PMID:23470206

  13. Charge Assisted Laser Desorption/Ionization Mass Spectrometry of Droplets

    PubMed Central

    Jorabchi, Kaveh; Westphall, Michael S.; Smith, Lloyd M.

    2008-01-01

    We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet. Implications of the new mechanism, termed charge assisted laser desorption/ionization (CALDI), are discussed and contrasted to those of the laser desorption atmospheric pressure chemical ionization method (LD-APCI). It is also demonstrated that analyte ion generation in CALDI occurs with external electric fields about one order of magnitude lower than those needed for atmospheric pressure matrix assisted laser desorption/ionization or electrospray ionization of droplets. PMID:18387311

  14. High-temperature gas-cooled reactor technology development program. Annual progress report for period ending December 31, 1982

    SciTech Connect

    Kasten, P.R.; Rittenhouse, P.L.; Bartine, D.E.; Sanders, J.P.

    1983-06-01

    During 1982 the High-Temperature Gas-Cooled Reactor (HTGR) Technology Program at Oak Ridge National Laboratory (ORNL) continued to develop experimental data required for the design and licensing of cogeneration HTGRs. The program involves fuels and materials development (including metals, graphite, ceramic, and concrete materials), HTGR chemistry studies, structural component development and testing, reactor physics and shielding studies, performance testing of the reactor core support structure, and HTGR application and evaluation studies.

  15. Application of programmed-temperature split\\/splitless injection to the trace analysis of aliphatic hydrocarbons by gas chromatography

    Microsoft Academic Search

    M Miñones Vázquez; M. E Vázquez Blanco; S Muniategui Lorenzo; P López Mah??a; E Fernández Fernández; D Prada Rodr??guez

    2001-01-01

    The dependence of the programmed-temperature solvent split sampling technique using a PSS (programmed-split\\/splitless) injection mode on different variables affecting the introduction of large sample volumes for a mixture of alkanes in capillary GC was evaluated. Apart from the studies found in the literature on different factors such as speed of injection, presence of adsorbent in the liner, internal diameter of

  16. Effect of partial exfoliation in carbon dioxide adsorption-desorption properties of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tamilarasan, P.; Ramaprabhu, S.

    2014-09-01

    In this study, we have experimentally studied the effect of partial exfoliation in low-pressure (<100 kPa) carbon dioxide adsorption and desorption behavior of multiwalled carbon nanotubes (MWNTs). MWNTs were partially exfoliated by controlled oxidation followed by hydrogen assisted low temperature exfoliation method. The adsorption capacity of partially exfoliated MWNTs (PEMWNTs) is 3.4 times that of MWNTs. Adsorption-desorption isotherms of MWNTs are unique, which shows trapping behavior. The desorption behavior in association with isothermal adsorbate retention of MWNTs and PEMWNTs suggests possible CO2 trapping inside the tubes and at interstitials. It is found that the CO2 adsorbed PEMWNTs system has higher molecular orbital energy than CO2 adsorbed MWNTs system. Areal adsorption capacity analysis suggests the significant influence of surface functional groups on adsorption capacity. Adsorption isosteres of both adsorbents follow the Arrhenius relation stating the temperature dependent adsorption rate. The isosteric heats and change in entropy of adsorption have been determined at multiple adsorbed amounts from the corresponding adsorption isosteres.

  17. Deformation-induced defects controlling fracture toughness of steel revealed by tritium desorption behaviors

    SciTech Connect

    Nagumo, M.; Yagi, T.; Saitoh, H.

    2000-02-25

    Defects induced by plastic deformation have been revealed by means of room temperature desorption and thermal desorption spectroscopy of tritium with regards to the ductile crack growth resistance and brittle fracture initiation in steels in the ductile-to-brittle transition region. Tritium, as a probe for detecting defects, was introduced into non-deformed or deformed samples. Three steels, the microstructures of which are characterized by the constraint factor for slip extension, were employed. The residual tritium in a specimen after three days at room temperature increased to the extent corresponding to the constraint factors when plastic deformation was applied. The thermally desorbed tritium, with a peak desorption rate around 150 C, also increased according to the constraint factors. Referring to the previous analysis of the R-curves, the constraint for the extension of slip across grain boundaries is shown to control both the ductile crack growth resistance and the brittle fracture initiation through the deformation microstructures that evolve vacancy clusters or microvoids.

  18. Mercury recovery from cold cathode fluorescent lamps using thermal desorption technology.

    PubMed

    Chang, T C; Chen, C M; Lee, Y F; You, S J

    2010-05-01

    Cold cathode fluorescent lamps (CCFLs) are globally used components of high technology products. A large amount of mercury in waste CCFLs is being recovered by thermal desorption technology in Taiwan. However, the complexity of the samples affects the thermal desorption efficiency and increases costs. This study identifies the mercury release behaviour of amalgam, phosphor and mercury-containing components as well as waste CCFLs by bench scale thermal desorption test. The results show that the mercury was released from amalgam and mercury/fluorescent powder from a real treatment plant at temperatures between 550 degrees C to 850 degrees C, which is much higher than from cinnabar at 300 degrees C to 380 degrees C and that of pure mercury, high pressure mercury lamps, and fluorescent tubes containing mercury/fluorescent-powder at 50 degrees C to 250 degrees C. In addition, the experiment also showed the mercury release peak of the mercury/fluorescent powders from a real treatment plant occurs at much higher temperatures than that of commercial phosphor at 50 degrees C to 200 degrees C. Thus, complete separation of the cracked CCFLs is necessary to effectively recover phosphor and mercury at low financial and energy cost. PMID:19723829

  19. Enhanced desorption of persistent organic pollutants from microplastics under simulated physiological conditions.

    PubMed

    Bakir, Adil; Rowland, Steven J; Thompson, Richard C

    2014-02-01

    Microplastics have the potential to uptake and release persistent organic pollutants (POPs); however, subsequent transfer to marine organisms is poorly understood. Some models estimating transfer of sorbed contaminants to organisms neglect the role of gut surfactants under differing physiological conditions in the gut (varying pH and temperature), examined here. We investigated the potential for polyvinylchloride (PVC) and polyethylene (PE) to sorb and desorb (14)C-DDT, (14)C-phenanthrene (Phe), (14)C-perfluorooctanoic acid (PFOA) and (14)C-di-2-ethylhexyl phthalate (DEHP). Desorption rates of POPs were quantified in seawater and under simulated gut conditions. Influence of pH and temperature was examined in order to represent cold and warm blooded organisms. Desorption rates were faster with gut surfactant, with a further substantial increase under conditions simulating warm blooded organisms. Desorption under gut conditions could be up to 30 times greater than in seawater alone. Of the POP/plastic combinations examined Phe with PE gave the highest potential for transport to organisms. PMID:24212067

  20. Optical breathing of nano-porous antireflective coatings through adsorption and desorption of water

    PubMed Central

    Nielsen, Karsten H.; Kittel, Thomas; Wondraczek, Katrin; Wondraczek, Lothar

    2014-01-01

    We report on the direct consequences of reversible water adsorption on the optical performance of silica-based nanoporous antireflective (AR) coatings as they are applied on glass in photovoltaic and solar thermal energy conversion systems. In situ UV-VIS transmission spectroscopy and path length measurements through high-resolution interferometric microscopy were conducted on model films during exposure to different levels of humidity and temperature. We show that water adsorption in the pores of the film results in a notable increase of the effective refractive index of the coating. As a consequence, the AR effect is strongly reduced. The temperature regime in which the major part of the water can be driven-out rapidly lies in the range of 55°C and 135°C. Such thermal desorption was found to increase the overall transmission of a coated glass by ~ 1%-point. As the activation energy of isothermal desorption, we find a value of about 18?kJ/mol. Within the experimental range of our data, the sorption and desorption process is fully reversible, resulting in optical breathing of the film. Nanoporous AR films with closed pore structure or high hydrophobicity may be of advantage for maintaining AR performance under air exposure. PMID:25307536

  1. Field desorption mass spectrometry of oligosaccharides

    PubMed Central

    Linscheid, Michael; D'Angona, Jay; Burlingame, Alma L.; Dell, Anne; Ballou, Clinton E.

    1981-01-01

    Field desorption mass spectrometry has been used to analyze carbohydrate polymers with 5 to 14 hexose units without prior derivatization. In all examples, the molecular weight of the oligosaccharide could be determined by means of the abundant quasimolecular ions of the type MNa+, MH+, MNa22+, and MNa33+. Fragmentation at glycosidic linkages was observed in varying extents. The reduced oligosaccharide Man8GlcNAcH2, obtained from IgM [Cohen, R. E. & Ballou, C. E. (1980) Biochemistry 19, 4345-4358], gave quasimolecular ion signals MNa+ at m/z 1544, MH+ at m/z 1522, MNa22+ at m/z 784, and MNa33+ at m/z 530, all corresponding to its assumed molecular weight of 1519.5. Mycobacterial methylmannose polysaccharides with the general structure ManxMeMany-OCH3 [Yamada, H., Cohen, R. E. & Ballou, C. E. (1979) J. Biol. Chem. 254, 1972-1979] were also successfully analyzed. Man1MeMan13-OCH3, the largest homolog, gave the expected signal of the quasimolecular ion MNa+ at m/z 2506. The larger polysaccharides were analyzed by using a KRATOS MS-50 mass spectrometer with a high-field magnet enabling full sensitivity to be maintained up to 3000 atomic mass units. Polysaccharides up to m/z 1978 were analyzed by using a KRATOS MS-9 mass spectrometer operated at 4 Kv. The signal-to-noise ratio, which becomes a serious problem in field desorption mass spectrometry at low accelerating voltages, and the low instrument sensitivity were improved considerably by our use of a method of adding scans with low total ion currents obtained over a longer desorption time. In this way, we obtained complete sequence information on methylmannose polysaccharides up to Man1MeMan9-OCH3(MNa+ at m/z 1802). Analysis of a presumed Man1MeMan7-OCH3, gave a spectrum consistent only with the structure Man2MeMan6-OCH3, revealing the existence of a methylmannose homolog with 2 unmethylated mannoses at the nonreducing end of the chain. PMID:6940169

  2. Comparison of Three Plasma Sources for Ambient Desorption/Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    McKay, Kirsty; Salter, Tara L.; Bowfield, Andrew; Walsh, James L.; Gilmore, Ian S.; Bradley, James W.

    2014-09-01

    Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources.

  3. Role of deuterium desorption kinetics on the thermionic emission properties of polycrystalline diamond films with respect to kinetic isotope effects

    SciTech Connect

    Paxton, W. F., E-mail: william.f.paxton@vanderbilt.edu; Howell, M.; Kang, W. P.; Davidson, J. L. [Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235 (United States); Brooks, M. M. [Department of Cell Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas 76107 (United States); Tolk, N. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)

    2014-06-21

    The desorption kinetics of deuterium from polycrystalline chemical vapor deposited diamond films were characterized by monitoring the isothermal thermionic emission current behavior. The reaction was observed to follow a first-order trend as evidenced by the decay rate of the thermionic emission current over time which is in agreement with previously reported studies. However, an Arrhenius plot of the reaction rates at each tested temperature did not exhibit the typical linear behavior which appears to contradict past observations of the hydrogen (or deuterium) desorption reaction from diamond. This observed deviation from linearity, specifically at lower temperatures, has been attributed to non-classical processes. Though no known previous studies reported similar deviations, a reanalysis of the data obtained in the present study was performed to account for tunneling which appeared to add merit to this hypothesis. Additional investigations were performed by reevaluating previously reported data involving the desorption of hydrogen (as opposed to deuterium) from diamond which further indicated this reaction to be dominated by tunneling at the temperatures tested in this study (<775?°C). An activation energy of 3.19?eV and a pre-exponential constant of 2.3 × 10{sup 12} s{sup ?1} were determined for the desorption reaction of deuterium from diamond which is in agreement with previously reported studies.

  4. Research and development program for non-linear structural modeling with advanced time-temperature dependent constitutive relationships

    NASA Technical Reports Server (NTRS)

    Walker, K. P.

    1981-01-01

    Results of a 20-month research and development program for nonlinear structural modeling with advanced time-temperature constitutive relationships are reported. The program included: (1) the evaluation of a number of viscoplastic constitutive models in the published literature; (2) incorporation of three of the most appropriate constitutive models into the MARC nonlinear finite element program; (3) calibration of the three constitutive models against experimental data using Hastelloy-X material; and (4) application of the most appropriate constitutive model to a three dimensional finite element analysis of a cylindrical combustor liner louver test specimen to establish the capability of the viscoplastic model to predict component structural response.

  5. Sn-Mn binary metal oxides as non-carbon sorbent for mercury removal in a wide-temperature window.

    PubMed

    Xie, Jiangkun; Xu, Haomiao; Qu, Zan; Huang, Wenjun; Chen, Wanmiao; Ma, Yongpeng; Zhao, Songjian; Liu, Ping; Yan, Naiqiang

    2014-08-15

    A series of Sn-Mn binary metal oxides were prepared through co-precipitation method. The sorbents were characterized by powder X-ray diffraction (powder XRD), transmission electronic microscopy (TEM), H2-temperature-programmed reduction (H2-TPR) and NH3-temperature-programmed desorption (NH3-TPD) methods. The capability of the prepared sorbents for mercury adsorption from simulated flue gas was investigated by fixed-bed experiments. Results showed that mercury adsorption on pure SnO2 particles was negligible in the test temperature range, comparatively, mercury capacity on MnOx at low temperature was relative high, but the capacity would decrease significantly when the temperature was elevated. Interestingly, for Sn-Mn binary metal oxide, mercury capacity increased not only at low temperature but also at high temperature. Furthermore, the impact of SO2 on mercury adsorption capability of Sn-Mn binary metal oxides was also investigated and it was noted that the effect at low temperature was different comparing with that of high temperature. The mechanism was investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs). Moreover, a mathematic model was built to calculate mercury desorption activation energy from Sn to Mn binary metal oxides. PMID:24910043

  6. Copper desorption from Gelidium algal biomass.

    PubMed

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-04-01

    Desorption of divalent copper from marine algae Gelidium sesquipedale, an algal waste (from agar extraction industry) and a composite material (the algal waste immobilized in polyacrylonitrile) was studied in a batch system. Copper ions were first adsorbed until saturation and then desorbed by HNO(3) and Na(2)EDTA solutions. Elution efficiency using HNO(3) increases as pH decreases. At pH=1, for a solid to liquid ratio S/L=4gl(-1), elution efficiency was 97%, 95% and 88%, the stoichiometric coefficient for the ionic exchange, 0.70+/-0.02, 0.73+/-0.05 and 0.76+/-0.06 and the selectivity coefficient, 0.93+/-0.07, 1.0+/-0.3 and 1.1+/-0.3, respectively, for algae Gelidium, algal waste and composite material. Complexation of copper ions by EDTA occurs in a molar proportion of 1:1 and the elution efficiency increases with EDTA concentration. For concentrations of 1.4, 0.88 and 0.57 mmoll(-1), the elution efficiency for S/L=4gl(-1), was 91%, 86% and 78%, respectively, for algae Gelidium, algal waste and composite material. The S/L ratio, in the range 1-20gl(-1), has little influence on copper recovery by using 0.1M HNO(3). Desorption kinetics was very fast for all biosorbents. Kinetic data using HNO(3) as eluant were well described by the mass transfer model, considering the average metal concentration in the solid phase and the equilibrium relationship given by the mass action law. The homogeneous diffusion coefficient varied between 1.0 x 10(-7)cm(2)s(-1) for algae Gelidium and 3.0 x 10(-7)cm(2)s(-1) for the composite material. PMID:17276480

  7. Electron-stimulated desorption of D{sup +} from DâO ice: Surface structure and electronic excitations

    Microsoft Academic Search

    M. T. Sieger; W. C. Simpson; T. M. Orlando

    1997-01-01

    We present a study of the electron-stimulated desorption of deuterium cations (D{sup +}) from thin (1â40 ML) DâO ice films vapor deposited on a Pt(111) substrate. Measurements of the total yield and velocity distributions as a function of temperature from 90 to 200 K show that the D{sup +} yield changes with film thickness, surface temperature, and ice phase. We

  8. [Desorption characteristics of phosphorus in tea tree rhizosphere soil].

    PubMed

    Yang, Wei; Zhou, Wei-Jun; Bao, Chun-Hong; Miao, Xiao-Lin; Hu, Wen-Min

    2013-07-01

    In order to explore the phosphorus (P) release process and its supply mechanism in tea tree rhizosphere soil, an exogenous P adsorption and culture experiment was conducted to study the P desorption process and characters in the tea tree rhizosphere soils having been cultivated for different years and derived from different parent materials. The least squares method was used to fit the isotherms of P desorption kinetics. There was an obvious difference in the P desorption process between the rhizosphere soils and non-rhizosphere soils. The P desorption ability of the rhizosphere soils was significantly higher than that of the non-rhizosphere soils. As compared with non-rhizosphere soils, rhizosphere soils had higher available P content, P desorption rate, and beta value (desorbed P of per unit adsorbed P), with the average increment being 5.49 mg x kg(-1), 1.7%, and 24.4%, respectively. The P desorption ability of the rhizosphere soils derived from different parent materials was in the order of granite > quaternary red clay > slate. The average available P content and P desorption ability of the rhizosphere soils increased with increasing cultivation years. PMID:24175512

  9. The Effect of Selective Desorption Mechanisms During Interstellar Ice Formation

    NASA Astrophysics Data System (ADS)

    Kalv?ns, J.

    2015-04-01

    Major components of ices on interstellar grains in molecular clouds—water and carbon oxides—occur at various optical depths. This implies that selective desorption mechanisms are at work. An astrochemical model of a contracting low-mass molecular cloud core is presented. Ice was treated as consisting of the surface and three subsurface layers (i.e., sublayers). Photodesorption, reactive desorption, and indirect reactive desorption were investigated. The latter manifests itself through desorption from H+H reaction on grains. Desorption of shallow subsurface species was also included. Modeling results suggest the existence of a “photon-dominated ice” during the early phases of core contraction. Subsurface ice is chemically processed by interstellar photons, which produces complex organic molecules (COMs). Desorption from the subsurface layer results in high COM gas-phase abundances at AV = 2.4–10 mag. This may contribute toward an explanation for COM observations in dark cores. It was found that photodesorption mostly governs the onset of ice accumulation onto grains. Reaction-specific reactive desorption is efficient for small molecules that form via highly exothermic atom-addition reactions. Higher reactive desorption efficiency results in lower gas-phase abundances of COMs. Indirect reactive desorption allows for closely reproducing the observed H2O:CO:CO2 ratio toward a number of background stars. Presumably, this can be done by any mechanism whose efficiency fits with the sequence CO?slant C{{O}2}\\gg {{H}2}O. After the freeze-out has ended, the three sublayers represent chemically distinct parts of the mantle. The likely AV threshold for the appearance of CO ice is 8–10.5 mag. The lower value is supported by observations.

  10. Effect of temperature on lubrication with biobased oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Temperature is an important parameter affecting the performance of lubricant ingredients. It affects such important tribological characteristics as viscosity, film thickness, adsorption, desorption, friction, and wear. Temperature also promotes oxidation, polymerization, and degradation which nega...

  11. Research and development program for the development of advanced time-temperature dependent constitutive relationships. Volume 1: Theoretical discussion

    NASA Technical Reports Server (NTRS)

    Cassenti, B. N.

    1983-01-01

    The results of a 10-month research and development program for the development of advanced time-temperature constitutive relationships are presented. The program included (1) the effect of rate of change of temperature, (2) the development of a term to include time independent effects, and (3) improvements in computational efficiency. It was shown that rate of change of temperature could have a substantial effect on the predicted material response. A modification to include time-independent effects, applicable to many viscoplastic constitutive theories, was shown to reduce to classical plasticity. The computation time can be reduced by a factor of two if self-adaptive integration is used when compared to an integration using ordinary forward differences. During the course of the investigation, it was demonstrated that the most important single factor affecting the theoretical accuracy was the choice of material parameters.

  12. The Kinetic Study of H2S Formation and Desorption on the S/Pt(111) Surface by Computer Simulation

    NASA Astrophysics Data System (ADS)

    Moshfegh, A. Z.; Zakeri, K. H.

    In this investigation, we have studied the kinetics and mechanism of formation and desorption of H2S on the Pt(111) surface using a kinetic random walk model. The effect of temperature on the H2S formation was studied in the range of 85 150 K. It was observed that a maximum amount of H2S is formed at 90 K and the amount is reduced at higher temperatures. H2S production yield as a function of time at different initial sulfur coverage ranging from 0.02 to 0.33 ML (1 ML ? 1 × 1015 atoms/cm2) was also examined. It was obvious that as the initial S coverage increases, the rate of H2S formation rapidly increases and reaches a maximum value and then declines gradually. Furthermore, according to our simulated TPD spectra, for ? = 1 K/s the maximum desorption rate occurs at Tp = 107.2 K. In addition, analysis of simulated TPD spectra of H2S desorption showed in an activation energy of H2S desorption Ed = 27.2 kcal/mol. Finally, the obtained simulated results were compared with the experimental data reported very recently, showing excellent agreement.

  13. Surfkin: A program to solve transient and steady state heterogeneous reaction kinetics

    SciTech Connect

    COLTRIN,MICHAEL E.; WIXOM,RYAN R.; DANDY,DAVID S.

    2000-05-01

    Heterogeneous chemical reactions occurring at a gas/surface interface are fundamental in a variety of important applications, such as combustion, catalysis, chemical vapor deposition and plasma processing. Detailed simulation of these processes may involve complex, coupled fluid flow, heat transfer, gas-phase chemistry, in addition to heterogeneous reaction chemistry. This report documents the Surfkin program, which simulates the kinetics of heterogeneous chemical reactions. The program is designed for use with the Chemkin and Surface Chemkin (heterogeneous chemistry) programs. It calculates time-dependent or steady state surface site fractions and bulk-species production/destruction rates. The surface temperature may be specified as a function of time to simulate a temperature-programmed desorption experiment, for example. This report serves as a user's manual for the program, explaining the required input and format of the output. Two detailed example problems are included to further illustrate the use of this program.

  14. NOVEL CERAMIC MEMBRANE FOR HIGH TEMPERATURE CARBON DIOXIDE SEPARATION

    SciTech Connect

    Jun-ichi Ida; Zhaohui Yang; Jerry Y.S. Lin

    2001-09-01

    The Objective of this research program is to develop a dense, non porous ceramic membrane for separation of carbon dioxide from flue gas at high temperatures (400-600 C). The research has been focused on addressing several fundamental issues of lithium zirconate (Li{sub 2}ZrO{sub 3}). In the 2nd half research, we conducted various kinds of experiments to understand the CO{sub 2} sorption/desorption mechanism on the pure and modified Li{sub 2}ZrO{sub 3} with the help of TGA, DSC TGA and XRD. DSC TGA results suggest that the melting of Li/K carbonates mixture may play an important role in rapid CO{sub 2} sorption in the case of modified lithium zirconate. The CO{sub 2} desorption experiments show that CO{sub 2} desorption from the modified lithium zirconate follows the same mechanism as that from the pure lithium zirconate. This is different from the CO{sub 2} adsorption on the pure and modified lithium zirconates.

  15. Electron stimulated desorption of atomic oxygen from silver

    NASA Technical Reports Server (NTRS)

    Outlaw, R. A.; Peregoy, W. K.; Hoflund, Gar B.; Corallo, Gregory R.

    1987-01-01

    The electron stimulated desorption (ESD) of neutral oxygen atoms from polycrystalline silver and of oxygen ions from Ag(110) has been studied. Polycrystalline Ag charged with (16)O2 and (18)O2 and bombarded by low-energy electrons (approx 100 eV) under ultrahigh vacuum (UHV) conditions emitted O atom flux levels of 1 x 10 to the 12th power/sq cm/s at a Ag temperature of 300 C. The flux was detected with a quadrupole mass spectrometer operating in the appearance potential mode. The neutral cross section at about 100 C was determined to be 7 x 10 to the -19 sq cm. Ancillary experiments conducted in a UHV chamber equipped with a cylindrical mirror analyzer and rigged for ion energy distribution and ion angular distribution were used to study O ions desorbed from Ag(110). Two primary O(+) energies of 2.4 and 5.4 eV were detected from the Ag(110) after having been dosed with 2500 L of (16)O2. It also appears that in both experiments there was strong evidence for directionality of the emitted flux. The results of this study serve as a proof of concept for the development of a laboratory atomic oxygen beam generator that simulates the gas flux environment experienced by orbiting vehicles.

  16. Adsorption and pressure swing desorption of NOx in Na-Y zeolite: experiments and modeling.

    PubMed

    Brilhac, J F; Sultana, A; Gilot, P; Martens, J A

    2002-03-01

    Pressure swing NOx adsorption-desorption cycles were performed in the temperature range 200-350 degrees C using a fixed adsorbent bed of compressed Na-Y pellets and using a honeycomb coated with Na-Y powder. The experiments were performed using a synthetic gas mixture mimicking exhaust from a lean burn internal combustion engine. Na-Y zeolite coadsorbs NO and NO2 as N2O3, which in the regeneration were displaced by competitively adsorbed water molecules from a hydrated air stream. The performance of the fixed bed in these NOx adsorption and displacement desorption processes were modeled with a one-dimensional model. The kinetic and thermodynamic parameters from the fixed bed model were implemented in a model for the operation of the monolith. The experimental adsorption and desorption NOx concentration profiles in the monolith were reasonably well reproduced by the model. The water content of the flushing stream and the stripping gas flow rate are key process parameters. Technically, both parameters can be optimized in a valveless system with rotating honeycomb adsorbent comprising a NOx adsorption, a water injection and a NOx evacuation section. PMID:11918002

  17. Relaxation of a hydrophilic polymer induced by moisture desorption through the glass transition.

    PubMed

    Zhang, Xiaolong; Hu, Hongjiu; Guo, Manxia

    2015-02-01

    Regarding the underlying special relaxation feature of a water-plasticized hydrophilic polymer during performance evolution with water content change, we report the water desorption kinetics and periodic creep responses of poly(vinyl alcohol) (PVA) films subsequent to rejuvenation by above-glass transition relative humidity (RH) annealing and following RH-jump at various rates. A Moisture Sorption Analyzer and a Dynamic Mechanical Analyzer are utilized to control RH and to capture data to probe the evolving relaxation towards equilibrium under two temperature-RH conditions. This result reveals an evident jump rate dependence of desorption kinetics and recoverable creep deformation. The different target RH yields the different change patterns of normalized water content and retardation time. PVA manifests a rapid relaxation stage with the special viscoelastic response before experience of usual physical aging. By analysis of the superposition principle and the relevant characteristic parameters, the relaxation of the hydrophilic polymer after water desorption through the glass transition is generalized as three successive phases. PMID:25519682

  18. Zero-Headspace Coal-Core Gas Desorption Canister, Revised Desorption Data Analysis Spreadsheets and a Dry Canister Heating System

    USGS Publications Warehouse

    Barker, Charles E.; Dallegge, Todd A.

    2005-01-01

    Coal desorption techniques typically use the U.S. Bureau of Mines (USBM) canister-desorption method as described by Diamond and Levine (1981), Close and Erwin (1989), Ryan and Dawson (1993), McLennan and others (1994), Mavor and Nelson (1997) and Diamond and Schatzel (1998). However, the coal desorption canister designs historically used with this method have an inherent flaw that allows a significant gas-filled headspace bubble to remain in the canister that later has to be compensated for by correcting the measured desorbed gas volume with a mathematical headspace volume correction (McLennan and others, 1994; Mavor and Nelson, 1997).

  19. Non-thermal desorption from interstellar dust grains via exothermic surface reactions

    E-print Network

    R. T. Garrod; V. Wakelam; E. Herbst

    2007-03-08

    Aims: The gas-phase abundance of methanol in dark quiescent cores in the interstellar medium cannot be explained by gas-phase chemistry. In fact, the only possible synthesis of this species appears to be production on the surfaces of dust grains followed by desorption into the gas. Yet, evaporation is inefficient for heavy molecules such as methanol at the typical temperature of 10 K. It is necessary then to consider non-thermal mechanisms for desorption. But, if such mechanisms are considered for the production of methanol, they must be considered for all surface species. Methods: Our gas-grain network of reactions has been altered by the inclusion of a non-thermal desorption mechanism in which the exothermicity of surface addition reactions is utilized to break the bond between the product species and the surface. Our estimated rate for this process derives from a simple version of classical unimolecular rate theory with a variable parameter only loosely contrained by theoretical work. Results: Our results show that the chemistry of dark clouds is altered slightly at times up to 10^6 yr, mainly by the enhancement in the gas-phase abundances of hydrogen-rich species such as methanol that are formed on grain surfaces. At later times, however, there is a rather strong change. Instead of the continuing accretion of most gas-phase species onto dust particles, a steady-state is reached for both gas-phase and grain-surface species, with significant abundances for the former. Nevertheless, most of the carbon is contained in an undetermined assortment of heavy surface hydrocarbons. Conclusions: The desorption mechanism discussed here will be better constrained by observational data on pre-stellar cores, where a significant accretion of species such as CO has already occurred.

  20. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, April--June 1993

    SciTech Connect

    Song, Chunshan; Parfitt, D.P.; Schobert, H.H.

    1993-08-01

    The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular precursors, that can be used in low concentrations (temperature-programmed conditions. Several heterometallic complexes consisting of two transition metals, Mo and Co, and sulfur in a single molecule were synthesized and tested as precursors of bimetallic dispersed catalysts for liquefaction of a Montana subbituminous coal (DECS-9) at the loading level of 0.5 wt% Mo on dmmf coal. It was found that the structure of the precursors, in particular the ligands to the metal species, affect the activity of the resulting catalyst significantly. Among the M-M` type precursors tested, Mo-Co thiocubane, Mo{sub 2}Co{sub 2}S{sub 4}(Cp){sub 2}(CO){sub 2} [Cp = cyclopentadiene], designated as MoCo-TC2, produced in-situ the best catalyst The performance of the Mo-Co bimetallic catalyst was further enhanced by using temperature programmed (TPL) conditions consisting of a low temperature soaking at 200{degrees}C, programmed heat-up to 400 or 425{degrees}C followed by a 30 minutes hold. The pro ed heat-up serves as an in-situ activation of catalyst and coal pretreatment, which contributes to more effective hydrogenation of reactive fragments at high temperature.

  1. Gas desorption and surface conditioning of a synchrotron radiation source

    SciTech Connect

    Mathewson, A.G.; Andritschky, M.; Groebner, O.; Schumann, F.; Strubin, P.; Souchet, R.

    1988-09-30

    Synchrotron radiation induced neutral gas desorption from baked Al alloy vacuum chambers cleaned using alkaline detergents has been measured in a test beam line at the DCI storage ring at LURE, Orsay, France.

  2. Molecular beam-thermal hydrogen desorption from palladium

    SciTech Connect

    Lobo, R. F. M.; Berardo, F. M. V.; Ribeiro, J. H. F. [Grupo de Nanotecnologia e Ciencia a Nano-Escala, Faculdade de Ciencias e Tecnologia da Universidade Nova de Lisboa, 2829-516 Caparica, Portugal and Instituto de Ciencia e Tecnologia de Materiais e Superficies (ICEMS), Av. Rovisco Pais, IST, 1049-001 Lisboa (Portugal)

    2010-04-15

    Among the most efficient techniques for hydrogen desorption monitoring, thermal desorption mass spectrometry is a very sensitive one, but in certain cases can give rise to uptake misleading results due to residual hydrogen partial pressure background variations. In this work one develops a novel thermal desorption variant based on the effusive molecular beam technique that represents a significant improvement in the accurate determination of hydrogen mass absorbed on a solid sample. The enhancement in the signal-to-noise ratio for trace hydrogen is on the order of 20%, and no previous calibration with a chemical standard is required. The kinetic information obtained from the hydrogen desorption mass spectra (at a constant heating rate of 1 deg. C/min) accounts for the consistency of the technique.

  3. Nuclear stimulated desorption of isolated cadmium atoms from structured surfaces

    NASA Astrophysics Data System (ADS)

    Ashkenazy, Y.; Kelson, I.; Bertschat, H. H.; Potzger, K.; Weber, A.; Zeitz, W.-D.; Isolde-Collaboration At Cern

    1999-11-01

    Measurements of nuclear stimulated desorption (NSD) of 107Cd from a (111) nickel single crystal surface covered with a fraction of a monolayer of palladium were performed. The total desorption probability and the polar angular distribution were determined. An anisotropic distribution with a minimum in the upward direction was found. This distribution is compared with molecular dynamics calculations and is shown to be consistent with desorption from step sites. It is also qualitatively consistent with independent results on similar systems obtained by the perturbed angular correlation method using 111 mCd. The total desorption probability agrees with the predicted value. Future work required to turn NSD into a useful analytic tool is discussed.

  4. TREATMENT OF HAZARDOUS PETROLEUM CONTAMINATED SOILS BY THERMAL DESORPTION TECHNOLOGIES

    EPA Science Inventory

    Spills, leaks, and accidental discharges of petroleum products have contaminated soil at thousands of sites in the United States. ne remedial action technique for treating petroleum contaminated soil is the use of thermal desorption technologies. his paper describes key elements ...

  5. Hydrogen Desorption and Adsorption Measurements on Graphite Nanofibers

    NASA Technical Reports Server (NTRS)

    Ahn, C. C.; Ye, Y.; Ratnakumar, B. V.; Witham, C. K.; Bowman, R. C., Jr.; Fultz, B.

    1998-01-01

    Graphite nanofibers were synthesized and their hydrogen desorption and adsorption properties are reported for 77 and 300 K. Catalysts were made by several different methods including chemical routes, mechanical alloying and gas condensation.

  6. Chemisorption, reaction and desorption studies of coal chars in steam, oxygen and carbon dioxide. Final report, January 1986-December 1989

    SciTech Connect

    Radovic, L.R.; Lizzio, A.A.; Jiang, H.

    1990-09-01

    The use of a transient kinetics (TK) technique allowed a direct measurement of reactive surface area (RSA) for chars gasified in both CO{sub 2} and O{sub 2}, i.e., gasification rates normalized with respect to RSA were essentially constant over the entire conversion range. A temperature-programmed desorption (TPD) technique was also used to determine the amount of reactive surface intermediate formed on the chars during gasification in CO{sub 2} and O{sub 2}; the results were in good agreement with those obtained by TK. In addition, TPD allowed an important distinction to be made between the stable C-O complexes and reactive C(O) intermediates residing on the char surface during gasification in CO{sub 2} and O{sub 2}. The application of the two independent but complementary techniques provided a satisfactory quantitative understanding of char reactivity variations with conversion in CO{sub 2} and O{sub 2}. Both techniques possess the unique capability of separately determining the reaction rate constant (site reactivity or turnover frequency) and the number of active sites participating in the reaction (RSA). A comparison of turnover frequencies for different chars gasified in 1 atm CO{sub 2} suggested that char gasification may be a structure sensitive reaction. The concept of reactive surface area was also used to achieve a better quantitative understanding of catalyzed char reactivity variations with conversion in carbon dioxide.

  7. High-temperature performance prediction of iron ore fines and the ore-blending programming problem in sintering

    NASA Astrophysics Data System (ADS)

    Yan, Bing-ji; Zhang, Jian-liang; Guo, Hong-wei; Chen, Ling-kun; Li, Wei

    2014-08-01

    The high-temperature performance of iron ore fines is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.

  8. HeatBalance, a computer program to determine optimum incubator air temperature and humidity. A comparison against nurse settings for infants less than 29 weeks gestation

    Microsoft Academic Search

    A. J Lyon; C Oxley

    2001-01-01

    Background: Very immature newborn infants need close control of their thermal environment. Decisions on incubator temperature and humidity settings can be difficult and available charts are not readily applicable to these babies. A computer program (HeatBalance) using basic principles to calculate heat gains and losses has been developed. The program recommends incubator temperature and humidity settings to keep babies in

  9. ²?²Cf-plasma desorption mass spectrometry of RNA nucleosides 

    E-print Network

    Piper, Duane Gilbert

    1976-01-01

    by Cf-plasma desorption mass spectrometry. Sample molecules are 252 volatilized and ionized by high-energy Cf fission particles. The mass of sample ions is determined by accelerating the volatil- ized tons into a flight tube where the ions separate... Studies . l. Electron Impact. . 2. Chemical Ionization. 3. Field Ionization . 4. Field Desorption . II. EXPERIMENTAL A. General B. Target Preparation. C. Vacuum System . D. Fission Source. E, Gridded Lens System . . F. Ion Detectors G...

  10. Design and evaluation of a miniaturized Particle Desorption Mass Spectrometer 

    E-print Network

    Davis, Kelly Vaughn

    1987-01-01

    Foundation through grant CHE-8310783 is greatfully acknowledged. TABLE OF CONTENTS CHAPTER PAGE I INTRODUCTION CURRENT STATUS OF PARTICLE DESORPTION MASS SPECTROMETRY AND PORTABLE MASS SPECTROMETRY PDMS Portable Mass Spectrometers. EXPERIMENTAL... MASS SPECTROMETRY AND PORTABLE MASS SPECTROMETRY The phenomenon of particle induced desorption was discovered by Macfarlane in the early 1970's (4) and has since been developed as a mass spectrometric technique for molecular weight determinations...

  11. Desorption of polycyclic aromatic hydrocarbons from carbon nanomaterials in water

    Microsoft Academic Search

    Kun Yang; Baoshan Xing

    2007-01-01

    Desorption behavior of pyrene, phenanthrene and naphthalene from fullerene, single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) was examined. Available adsorption space of carbon nanotubes (CNTs) was found to be the cylindrical external surface, neither the inner cavities nor inter-wall spaces due to impurities in the CNTs and restricted spaces (0.335nm) of the MWCNTs, respectively. Desorption hysteresis was observed

  12. Salt Tolerance of Desorption Electrospray Ionization (DESI)

    SciTech Connect

    Jackson, Ayanna U. [Purdue University; Talaty, Nari [Purdue University; Cooks, R G [Purdue University; Van Berkel, Gary J [ORNL

    2007-01-01

    Suppression of ion intensity in the presence of high salt matrices is common in most mass spectrometry ionization techniques. Desorption electrospray ionization (DESI) is an ionization method that exhibits salt tolerance, and this is investigated. DESI analysis was performed on three different drug mixtures in the presence of 0, 0.2, 2, 5, 10, and 20% NaCl:KCl weight by volume from seven different surfaces. At physiological concentrations individual drugs in each mixture were observed with each surface. Collision-induced dissociation (CID) was used to provide additional confirmation for select compounds. Multiple stage experiments, to MS5, were performed for select compounds. Even in the absence of added salt, the benzodiazepine containing mixture yielded sodium and potassium adducts of carbamazepine which masked the ions of interest. These adducts were eliminated by adding 0.1% 7M ammonium acetate to the standard methanol:water (1:1) spray solvent. Comparison of the salt tolerance of DESI with that of electrospray ionization (ESI) demonstrated much better signal/noise characteristics for DESI in this study. The salt tolerance of DESI was also studied by performing limit of detection and dynamic range experiments. Even at a salt concentration significantly above physiological concentrations, select surfaces were effective in providing spectra that allowed the ready identification of the compounds of interest. The already high salt tolerance of DESI can be optimized further by appropriate choices of surface and spray solution.

  13. Desorption of a methamphetamine surrogate from wallboard under remediation conditions

    NASA Astrophysics Data System (ADS)

    Poppendieck, Dustin; Morrison, Glenn; Corsi, Richard

    2015-04-01

    Thousands of homes in the United States are found to be contaminated with methamphetamine each year. Buildings used to produce illicit methamphetamine are typically remediated by removing soft furnishings and stained materials, cleaning and sometimes encapsulating surfaces using paint. Methamphetamine that has penetrated into paint films, wood and other permanent materials can be slowly released back into the building air over time, exposing future occupants and re-contaminating furnishings. The objective of this study was to determine the efficacy of two wallboard remediation techniques for homes contaminated with methamphetamine: 1) enhancing desorption by elevating temperature and relative humidity while ventilating the interior space, and 2) painting over affected wallboard to seal the methamphetamine in place. The emission of a methamphetamine surrogate, N-isopropylbenzylamine (NIBA), from pre-dosed wallboard chambers over 20 days at 32 °C and two values of relative humidity were studied. Emission rates from wallboard after 15 days at 32 °C ranged from 35 to 1400 ?g h-1 m-2. Less than 22% of the NIBA was removed from the chambers over three weeks. Results indicate that elevating temperatures during remediation and latex painting of impacted wallboard will not significantly reduce freebase methamphetamine emissions from wallboard. Raising the relative humidity from 27% to 49% increased the emission rates by a factor of 1.4. A steady-state model of a typical home using the emission rates from this study and typical residential building parameters and conditions shows that adult inhalation reference doses for methamphetamine will be reached when approximately 1 g of methamphetamine is present in the wallboard of a house.

  14. FORTRAN 77 programs for conductive cooling of dikes with temperature-dependent thermal properties and heat of crystallization

    USGS Publications Warehouse

    Delaney, P.T.

    1988-01-01

    Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.

  15. Use of non-porous reversed-phase high-performance liquid chromatography for protein profiling and isolation of proteins induced by temperature variations for Siberian permafrost bacteria with identification by matrix-assisted laser desorption\\/ionization time-of-flight mass spectrometry and capillary electrophoresis–electrospray ionization mass spectrometry

    Microsoft Academic Search

    Bathsheba E. Chong; Jeongkwon Kim; David M. Lubman; James M. Tiedje; Sohpia Kathariou

    2000-01-01

    Non-porous reversed-phase high-performance liquid chromatography (NP-RP-HPLC) has been used to separate and isolate proteins from whole cell lysates of ED 7-3, a bacterium from the buried Siberian permafrost sediment. The proteins collected from the liquid eluent of this separation were then analyzed by matrix-assisted laser desorption\\/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and capillary electrophoresis–electrospray ionization mass spectrometry (CE–ESI-MS). In order to

  16. Characterization of energetic topography of heterogeneous surfaces through the analysis of thermal desorption spectra

    NASA Astrophysics Data System (ADS)

    Gargiulo, M. V.; Sales, J. L.; Ciacera, M.; Zgrablich, G.

    2002-04-01

    Monte Carlo simulations of thermal programmed desorption spectra (TPDS) are obtained and analyzed for general heterogeneous surfaces characterized by a dual-site-bond model, where the adsorptive energy topography is described in terms of a correlation length l0. It is shown that the behavior of TPDS is such that the ambiguity arising in the characterization of the energetic topography through adsorption isotherms, where adsorbate-adsorbate interactions and topography effects compete with each other, is resolved in such a way that TPDS provide a more powerful characterization method.

  17. Smoothness and cleanliness of the GaAs (100) surface after thermal desorption of the native oxide for the synthesis of high mobility structures using molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, J. J. D.; West, K. W.; Baldwin, K. W.; Pfeiffer, L. N.

    2012-10-01

    To prepare a GaAs substrate for molecular beam epitaxial (MBE) growth, the nominal ˜3 nm native oxide is typically thermally desorbed into vacuum. To test the completeness and quality of this desorption, we describe a technique, which combines MBE, thermal desorption, atomic force microscopy (AFM), reflection high-energy electron diffraction (RHEED), and secondary ion mass spectroscopy (SIMS), for detecting roughness and trace residues of contamination on (100) GaAs surfaces before MBE growth. At all desorption temperatures in the range 600-665 °C, our RHEED measurements show that the native oxide is largely desorbed within 4 min. However, the SIMS and AFM data indicate that a residue of carbon invariably remains on the GaAs (100) surface, and tenaciously resists all further attempts at its removal by thermal desorption. Since thermal desorption of the native oxide has long been the standard technique for preparing GaAs substrates for MBE growth, we suggest that MBE growth on GaAs has in general been accomplished by epitaxially growing through a partial monolayer of carbon. We believe this is the likely reason for the generally unsatisfactory quality of GaAs MBE growth after lithographic patterning on previously MBE grown structures. Our AFM data also indicate that extended native oxide desorption times or high desorption temperatures not only are ineffective at removal of the carbon residue, but are always accompanied by additional strong roughening effects on the GaAs surface morphology. Finally, we demonstrate that smoother starting surfaces for MBE growth correlate well with higher two-dimensional carrier mobilities in the resulting AlGaAs/GaAs heterostructures.

  18. Reproducibility of Programmed-Temperature Retention Indices under Average Linear Velocity Carrier Gas Control of GC and GC–MS

    Microsoft Academic Search

    H. Miyagawa; K. Nakagawa; K. Kadokami

    2011-01-01

    Programmed-temperature retention indices (PTRIs) are useful for the identification and quantification of chemicals by means\\u000a of GC and GC\\/MS. To obtain reproducible PTRIs, we studied the influence of average linear velocity and column length under\\u000a the constant average linear velocity control (CVC) using 55 pesticides and 33 fatty acid methyl esters. The PTRIs decreased\\u000a with increasing average linear velocity, and

  19. Formation of metallic particles during temperature-programmed reduction of silica-supported platinum and nickel chlorides

    Microsoft Academic Search

    Andreas Jentys; J. A. Lercher; G. L. Haller

    1993-01-01

    The formation of (bi-) metallic particles during temperature-programmed reduction of silica-supported mixtures of Pt and Ni chlorides was followed by X-ray absorption spectroscopy. The concentration and composition of the metal particles in the final catalysts were derived from the results of the EXAFS analysis. The reduction kinetics followed by XANES were related to the formation of ordered metallic phases. During

  20. Flash Desorption/Mass Spectrometry for the Analysis of Less- and Nonvolatile Samples Using a Linearly Driven Heated Metal Filament

    NASA Astrophysics Data System (ADS)

    Usmanov, Dilshadbek T.; Ninomiya, Satoshi; Hiraoka, Kenzo

    2013-11-01

    In this paper, the important issue of the desorption of less- and nonvolatile compounds with minimal sample decomposition in ambient mass spectrometry is approached using ambient flash desorption mass spectrometry. The preheated stainless steel filament was driven down and up along the vertical axis in 0.3 s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1 mm in 50 ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~104 °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 ?g with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. [Figure not available: see fulltext.

  1. Desorption of cryogenic layers of the solid hydrogens by electron bombardment: The role of the metal substrate

    NASA Astrophysics Data System (ADS)

    Schou, Jørgen; Tratnik, Herbert; Thestrup, Birgitte; Hilleret, Noel

    2008-10-01

    For solid hydrogenic films in the thickness range from ˜50 ML to ˜500 ML the desorption yield falls off inversely proportional to the thickness for both H 2 and D 2 films. This behavior is common for data obtained at CERN for solid H 2 and at Risø National Laboratory for solid D 2 at temperatures below 4.2 K. The thickness range is comparable to the range of the electrons for energies between 0.3 and 2 keV. For these energies less energy is deposited in the metal substrate with increasing film thickness. We have explored how the behavior of the desorption yield may be explained in terms of the energy dissipated in a copper substrate or as the surface value of the energy deposited in electronic excitations in copper, but not found convincing arguments for a close correlation between the desorption yield and these quantities. The decreasing desorption yield for film thicknesses that greatly exceed the electron mean penetration depth evaluated from uniform films, may be explained by nonuniform growth of the hydrogen films on the metal substrate.

  2. Test VLPC Cryostat: Programming and Configuration of Cryogenic and Temperature Instruments

    SciTech Connect

    Zaczek, M.; /Fermilab

    1997-08-11

    Currently, Fermi National Accelerator Laboratory is in the midst of a site wide upgrade. Here at D-Zero, one of the components of this upgrade will be the construction of two 48 cassette VLPC cryostats which will be the heart of the new magnetic central fiber tracker. A VLPC or Visible Light Photon Counter is a device that allows physicists to more accurately calculate the origins of particles ejected during a proton - anti-proton collision in the detector. Inside the detector is an optical fiber barrel which surrounds the collision point. When an ejected particle strikes a fiber the result is the release of photons which travel along the fiber until they reach the bottom of a cassette hitting the VLPC chip. These impacts result in voltages which are read by the VLPC chips and sent to the computer for future analysis. From these voltages, physicists can determine the origins of the particles, their charges, their speeds and other information as well. Within the last few months a test VLPC bas been built at D-Zero. This VLPC is comprised of four rectangular cassettes each equipped with heating elements, RTDs and 1024 VLPC chips. This particular configuration is unique here at Fermilab. Other VLPC cryostats that have been built were usually cylindrical in their geometry. The purpose of this test VLPC is to have on hand a reliable model to aid in understanding the complexities involved in running such devices at approximately 10K, as well as to prepare for the eventual 48 cassette VLPCs to come. In particular, an important aspect of this test phase is to check the engineering involved so that the final cryostats are designed correctly. Also, this test cryostat will enable us to check each of the cassettes to be used in the final cryostat and correct any problems before hand. This engineering note has been written in order to describe the setup of the VLPC as it pertains to the programming, configuration and control of all of the cryogenic and temperature instruments. These instruments include the two pneumatic valves, the pressure transmitter, heating elements of the cassettes, and the various RIDs scattered throughout.

  3. Real-Time Studies of Gallium Adsorption and Desorption Kinetics by Grazing-Incidence Small-Angle X-ray Scattering and X-ray Fluorescence

    SciTech Connect

    Wang, Y.; Ozcan, A; Ludwig, K; Bhattacharyya, A

    2008-01-01

    Gallium adsorption and desorption on c-plane sapphire has been studied by real-time grazing incidence small-angle x-ray scattering and x-ray fluorescence as a function of substrate temperature (680-740 C) and Ga flux. The x-ray techniques monitor the surface morphology evolution and amount of Ga on the surface. During deposition, nanodroplets of liquid Ga are observed to form on the surface and coarsen. The growth of droplet size during continuous deposition follows dynamical scaling, in agreement with expectations from theory and simulations which include deposition-induced droplet coalescence. However, observation of continued droplet distance scale coarsening during desorption points to the necessity of including further physical processes in the modeling. The desorption rate at different substrate temperatures gives the activation energy of Ga desorption as 2.7 eV, comparable to measured activation energies for desorption from Ga droplets on other substrates and to the Ga heat of vaporization.

  4. Real-time studies of gallium adsorption and desorption kinetics on sapphire (0001) by grazing incidence small-angle x-ray scattering and x-ray fluorescence

    SciTech Connect

    Wang Yiyi; Oezcan, Ahmet S.; Ludwig, Karl F. [Physics Department, Boston University, Boston, Massachusetts 02215 (United States); Bhattacharyya, Anirban [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States)

    2008-05-15

    Gallium adsorption and desorption on c-plane sapphire has been studied by real-time grazing incidence small-angle x-ray scattering and x-ray fluorescence as a function of substrate temperature (680-740 deg. C) and Ga flux. The x-ray techniques monitor the surface morphology evolution and amount of Ga on the surface. During deposition, nanodroplets of liquid Ga are observed to form on the surface and coarsen. The growth of droplet size during continuous deposition follows dynamical scaling, in agreement with expectations from theory and simulations which include deposition-induced droplet coalescence. However, observation of continued droplet distance scale coarsening during desorption points to the necessity of including further physical processes in the modeling. The desorption rate at different substrate temperatures gives the activation energy of Ga desorption as 2.7 eV, comparable to measured activation energies for desorption from Ga droplets on other substrates and to the Ga heat of vaporization.

  5. Results of thermal desorption treatability studies on soils from wood treatment sites

    SciTech Connect

    Shealy, S.E.; Lin, W.C. [IT Corp., Knoxville, TN (United States); Richards, M.K. [EPA, Cincinnati, OH (United States); Culp, J. [EA Engineering, San Pedro, CA (United States)

    1997-12-31

    Thermal desorption is one of the most effective technologies for treatment of soils or wastes containing organic contaminants. This includes the polycyclic aromatic hydrocarbons, pentachlorophenol and dioxins/furans that are the typical contaminants of concern at wood treatment sites. This paper summarizes the results of bench-scale thermal desorption treatability studies on soils from two wood treatment sites. The testing identified the time-temperature combination needed for contaminant removal and provided data on the composition of the treatment residuals from the thermal treatment process. This study included testing in static trays and in a small bench-scale rotary kiln. The static tray tests are a bench-scale method of readily evaluating the effect of various target temperatures and residence times on contaminant removal. These tests use 40--50 grams, of soil, which is aliquoted into a tray and placed into a muffle furnace at a pre-determined time and temperature. These tests are used to identify effective treatment conditions. The Rotary Thermal Apparatus (RTA) is also a bench-scale device that is used to treat 1 to 1.5 kilograms of soil in an indirectly heated rotary tube. This device simulates the heat and mass transfer in rotary kiln. The RTA is a batch device and can be purged with nitrogen, oxygen or other gases to simulate the atmosphere of various thermal treatment processes.

  6. Application of programmed-temperature split/splitless injection to the trace analysis of aliphatic hydrocarbons by gas chromatography.

    PubMed

    Miñones Vázquez, M; Vázquez Blanco, M E; Muniategui Lorenzo, S; López Mahía, P; Fernández Fernández, E; Prada Rodríguez, D

    2001-06-15

    The dependence of the programmed-temperature solvent split sampling technique using a PSS (programmed-split/splitless) injection mode on different variables affecting the introduction of large sample volumes for a mixture of alkanes in capillary GC was evaluated. Apart from the studies found in the literature on different factors such as speed of injection. presence of adsorbent in the liner, internal diameter of the liner, initial and final injector temperature, split flow-rate and initial split time, affecting the chromatographic signal of different compounds, others were studied whose influence has not been considered until now. They include length of the microsyringe needle, adsorbent distribution in the liner, injection volume on analyte discrimination, speed of injector heating, time which the column stays at the initial temperature and time that the injector stays at the final temperature. Once finalised, the study of the PSS injection mode was compared with the conventional mode of gas chromatography splitless injection, and found that the proposed method increases sensitivity in GC trace analysis. Finally, the application of both injection modes in the determination of aliphatic hydrocarbons was tested in an atmospheric particulate sample. PMID:11442043

  7. Desorption of copper and cadmium from soils enhanced by organic acids.

    PubMed

    Yuan, Songhu; Xi, Zhimin; Jiang, Yi; Wan, Jinzhong; Wu, Chan; Zheng, Zhonghua; Lu, Xiaohua

    2007-07-01

    The adsorption/desorption behavior of copper and cadmium on soils was investigated in this study. The adsorption isotherm of copper and cadmium conformed to Langmuir equation better than Freundlich equation. The effect of ionic strength, pH, and organic acid, including ethylenediamine tetraacetic disodium acid salt (EDTA), citric acid, oxalic acid and tartaric acid, on the desorption of copper and cadmium was studied. The desorption of copper and cadmium increased with the increase of ionic strength, while the desorption decreased with the rise of pH. The desorption of copper and cadmium enhanced by organic acids was influenced by pH. EDTA showed excellent enhancement on the desorption of both copper and cadmium; citric acid demonstrated great enhancement on the desorption of copper but negligible enhancement on the desorption of cadmium; oxalic acid enhanced the desorption of copper only at pH around 6.4 and enhanced the desorption of cadmium in the pH range from 6.4 to 10.7; tartaric acid slightly enhanced the desorption of copper but negligibly enhanced the desorption of cadmium. The desorption mechanism in the presence of organic acids were explained as the competition of complexation, adsorption and precipitation. The net effect determined the desorption efficiency. This study provided guidance for the selection of organic acids to enhance the electrokinetic (EK) remediation of copper and cadmium from contaminated soils. PMID:17349675

  8. Dispersive micro solid-phase extraction for the rapid analysis of synthetic polycyclic musks using thermal desorption gas chromatography-mass spectrometry.

    PubMed

    Chung, Wu-Hsun; Tzing, Shin-Hwa; Ding, Wang-Hsien

    2013-09-13

    A simple and solvent-free method for the rapid analysis of five synthetic polycyclic musks in water samples is described. The method involves the use of dispersive micro solid-phase extraction (D-?-SPE) coupled with direct thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) operating in the selected-ion-storage (SIS) mode. The parameters affecting the extraction efficiency of the target analytes from water sample and the thermal desorption conditions in the GC injection-port were optimized using a central composite design method. The optimal extraction conditions involved immersing 3.2mg of a typical octadecyl (C18) bonded silica adsorbent (i.e., ENVI-18) in a 10mL water sample. After extraction by vigorously shaking for 1.0min, the adsorbents were collected and dried on a filter. The adsorbents were transferred to a micro-vial, which was directly inserted into GC temperature-programmed injector, and the extracted target analytes were then thermally desorbed in the GC injection-port at 337°C for 3.8min. The limits of quantitation (LOQs) were determined to be 1.2-3.0ng/L. Precision, as indicated by relative standard deviations (RSDs), was less than 9% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was between 74 and 90%. A preliminary analysis of the river water samples revealed that galaxolide (HHCB) and tonalide (AHTN) were the two most common synthetic polycyclic musks present. Using a standard addition method, their concentrations were determined to in the range from 11 to 140ng/L. PMID:23932027

  9. Desorption resistance of polycyclic aromatic hydrocarbons and duration of exposure.

    PubMed

    Chai, Yunzhou; Kochetkov, Alexander; Reible, Danny D

    2006-11-01

    The desorption-resistant fraction of laboratory-spiked phenanthrene in two Louisiana (USA) sediments was not observed to be significantly different, but the two sediments exhibited different condensed-phase organic carbon contents, as defined operationally by the organic carbon remaining after combustion of the sediment at 375 degrees C. Only 3% of the original saturated phenanthrene in the sediments was not readily removed by exposure to a nonpolar polymeric resin and sorbent XAD-2. Allowing the laboratory-spiked contaminants to age for periods of up to three years yielded little difference in the desorption-resistant characteristics of the sediments. Field-contaminated sediments from Utica Harbor (Utica, NY, U.S.A.) and Rouge River (Detroit, MI, USA) that had a lengthy (decades to a century) period of contamination, however, exhibited significantly different desorption-resistant contaminant fractions, consistent with the fractions of condensed-phase organic carbon in the sediments. Measurements of the fraction that could be rapidly desorbed using the XAD-2 sorbent also accounted for essentially all desorption to pore water and, thus, provided a good prediction of effective bulk partition coefficients. It was concluded that the condensed-phase organic carbon was a good indicator of the potential for desorption resistance in field-contaminated sediments and that the rapidly desorbing fraction provided a quantitative indicator of its significance. PMID:17089703

  10. Retention and desorption behavior of tritium in Si related ceramics

    NASA Astrophysics Data System (ADS)

    Oya, Yasuhisa; Hatano, Yuji; Hara, Masanori; Matsuyama, Masao; Okuno, Kenji

    2013-07-01

    Hydrogen isotope retention and desorption behaviors for Silicon carbide (SiC), Silicon nitride (Si3N4) and Silicon dioxide (SiO2) were studied to elucidate the fundamental process of hydrogen isotope in Si related ceramics by means of T-IP (tritium imaging plate), thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The tritium gas exposure at 673 K showed that tritium was precipitated on the surface for SiO2, although that for SiC was uniformly retained inside the bulk. The 0.2 keV D2+ implantation revealed that the deuterium desorption stages for Si related ceramics were consisted of four desorption stages at around 450 K, 650 K, 800 K, and 950 K, attributing to the desorptions of deuterium trapped on the surface, retained in interstitial sites, trapped as Si-D bond and trapped as C/N/O-D bond, respectively. The retention enhancement of deuterium trapped by Si as Si-D bond and the reduction of deuterium trapped on the surface would be associated with the enhancement of covalent bond characteristics for Si related ceramics. These results indicate that the dangling bonds in the covalent ceramics have higher hydrogen isotope trapping efficiency to form chemical bond like Si-D bond. On the other hand, the surface adsorption of hydrogen isotope was enhanced for the higher ionicity ceramics by charge localization.

  11. Influence of surface coverage on the chemical desorption process

    SciTech Connect

    Minissale, M.; Dulieu, F., E-mail: francois.dulieu@obspm.fr [LERMA, Université de Cergy Pontoise et Observatoire de Paris, UMR 8112 du CNRS. 5, mail Gay Lussac, 95031 Cergy Pontoise (France)

    2014-07-07

    In cold astrophysical environments, some molecules are observed in the gas phase whereas they should have been depleted, frozen on dust grains. In order to solve this problem, astrochemists have proposed that a fraction of molecules synthesized on the surface of dust grains could desorb just after their formation. Recently the chemical desorption process has been demonstrated experimentally, but the key parameters at play have not yet been fully understood. In this article, we propose a new procedure to analyze the ratio of di-oxygen and ozone synthesized after O atoms adsorption on oxidized graphite. We demonstrate that the chemical desorption efficiency of the two reaction paths (O+O and O+O{sub 2}) is different by one order of magnitude. We show the importance of the surface coverage: for the O+O reaction, the chemical desorption efficiency is close to 80% at zero coverage and tends to zero at one monolayer coverage. The coverage dependence of O+O chemical desorption is proved by varying the amount of pre-adsorbed N{sub 2} on the substrate from 0 to 1.5 ML. Finally, we discuss the relevance of the different physical parameters that could play a role in the chemical desorption process: binding energy, enthalpy of formation, and energy transfer from the new molecule to the surface or to other adsorbates.

  12. Carbon dioxide sorption/ desorption characteristics of coals in Taiwan

    NASA Astrophysics Data System (ADS)

    Chien-Hung, Hsiao; Loung-Yie, Tsai

    2013-04-01

    Geological sequestration of CO2 into depleted oil reservoir, saline aquifer or unmineable coal seam is now being actively investigated for the purpose of reducing greenhouse gas in the atmosphere. Understanding the physical, chemical, and thermodynamic phenomena occurred with CO2 injection is very important in marking a reliable prediction of sequestration. This study examined the feasibility of carbon dioxide sequestration into unmineable coal seams in Taiwan. A total of 20 Miocene-aged coal samples from Western Foothill Belt, NW Taiwan, were collected. The stratigraphy include Mushan, Shihti, and Nanchuang Formation from bottom up. Proximate and petrographic analyses include maceral composition, Vitrinite reflectance were also measured. Carbon dioxide adsorption isotherms were analyzed at 35 degrees Celsius and up to 800 psi, by using a gravimetric ad/desorption apparatus. Isotherms were then fitted with a modified Langmuir Isotherm model by using Langmuir Pressure and Langmuir Volume so the model can be applied to supercritical conditions. According to the result of adsorption experiment, the pressure and temperature were quite significant. The gas storage capacity of CO2 was about 400 600 scf/ton at pressure up to 800 psi. Comparing the results of adsorption capacity with Proximate analysis and vitrinite reflectance, the Langmuir Volume shows a strong positive correlation with fixed carbon and vitrinite content. Furthermore, Adsorption capacity is closely related to micropores which were also rank and maceral dependent. It is noticed that the observed coal pore structures were affected by rank, and then exhibit have different diffusion rate of CO2.Finally, images under SEM were evaluated to understand the pathways of gas sorption.

  13. Si 2H 6 adsorption and hydrogen desorption on Si(100) investigated by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Niwano, Michio; Shinohara, Masanori; Neo, Yoichiro; Yokoo, Kuniyoshi

    2000-08-01

    The adsorption and decomposition of disilane on Si(100)(2×1) was investigated using in-situ infrared (IR) absorption spectroscopy. The IR data demonstrate that upon room-temperature adsorption, disilane dissociatively adsorbs on the unsaturated dangling bonds of dimers with the dimer bonds unbroken, to produce mono-, di-, and tri-hydride species. At low coverages, dissociative adsorption without breaking of the Si?Si bond of Si 2H 6 is favored. Thermal annealing following room-temperature disilane adsorption produces the doubly-occupied adatom dimers (DOD, HSi?SiH) and isolated monohydride species. These hydride species are generated via the rupture of dimer bonds of the substrate. Hydrogen desorption from the isolated monohydride site occurs at lower temperatures than from the DOD site.

  14. Program for the development of high temperature electrical materials and components

    NASA Technical Reports Server (NTRS)

    Neff, W. S.; Lowry, L. R.

    1972-01-01

    Evaluation of high temperature, space-vacuum performance of selected electrical materials and components, high temperature capacitor development, and evaluation, construction, and endurance testing of compression sealed pyrolytic boron nitride slot insulation are described. The first subject above covered the aging evaluation of electrical devices constructed from selected electrical materials. Individual materials performances were also evaluated and reported. The second subject included study of methods of improving electrical performance of pyrolytic boron nitride capacitors. The third portion was conducted to evaluate the thermal and electrical performance of pyrolytic boron nitride as stator slot liner material under varied temperature and compressive loading. Conclusions and recommendations are presented.

  15. Thermal reactions of oxygen atoms with CS2 at low temperatures on interstellar dust

    NASA Astrophysics Data System (ADS)

    Ward, Michael D.; Hogg, Isobel A.; Price, Stephen D.

    2012-09-01

    The heterogeneous thermal reaction between carbon disulphide (CS2) and oxygen (O) atoms, producing carbonyl sulphide (OCS), has been investigated under astrophysically relevant conditions in laboratory experiments. We study this reaction at a range of fixed surface temperatures between 15 and 70 K. Following the interaction of the reactants, on a highly oriented pyrolytic graphite surface at a particular surface temperature, we use temperature-programmed desorption coupled with time-of-flight mass spectrometry to determine the yield of OCS. Consequently, our experimental data reveal the temperature dependence of the OCS yield over the aforementioned range of surface temperatures. Our experimental results indicate that thermal O atoms can readily convert CS2 contained in the icy mantles on interstellar grains to OCS, without the need for energetic processing of the ice. Our data set shows that this reaction proceeds at surface temperatures as low as 15 K. Therefore, contrary to previous suggestions, CS2 molecules in icy mantles are perhaps unlikely to account for a substantial proportion of the sulphur content of dense interstellar clouds. Reaction barriers and Arrhenius pre-exponential factors, and hence rate constants, are derived for this surface reaction by fitting our experimental data using a kinetic model. Additionally, this modelling procedure yields values for the desorption energies of O atoms and OCS.

  16. Adsorption and desorption of noble gases on activated charcoal: II. sup 222 Rn studies in a monolayer and packed bed

    SciTech Connect

    Scarpitta, S.C.; Harley, N.H. (Department of Energy, New York, NY (USA))

    1990-10-01

    The adsorptive and desorptive characteristics of canisters containing a petroleum-based charcoal were investigated under controlled conditions of temperature, relative humidity, and Rn concentration. Charcoals exposed in a monolayer and packed bed during exposure intervals of 1-7 d demonstrate that Rn adsorption and desorption are dependent on bed depth and the amount of water adsorbed. Changes in the adsorptive and desorptive properties of the charcoal occurred near the break-point where the pores became occluded by water vapor that condenses in the entrance capillaries. Radon-222 adsorption is decreased by an order of magnitude as the amount of adsorbed water exceeds the break-point of the charcoal. The reduction in pore surface due to adsorbed water results in a marked increase in the rate of Rn loss from exposed canisters, accounting for reduced adsorption. The apparent desorption time-constant for a 2-cm bed of loose Witco 6 x 10 mesh charcoal containing 0.220-0.365 kg H{sub 2}O kg-1 is typically between 2-8 h. The apparent desorption time-constant for an equivalent packed bed containing a water vapor content of 0.026-0.060 kg H{sub 2}O kg-1, which is below the break-point of the charcoal, is about 15-30 h. Conventional charcoal canisters, if exposed in the fully-opened configuration, can achieve the break-point in less than 4 d at 70% humidity. The use of a diffusion barrier would allow for longer exposure times until the break-point of the charcoal is achieved.

  17. Optimized thermal desorption for improved sensitivity in trace explosives detection by ion mobility spectrometry.

    PubMed

    Najarro, Marcela; Dávila Morris, Melissa E; Staymates, Matthew E; Fletcher, Robert; Gillen, Greg

    2012-06-01

    In this work we evaluate the influence of thermal desorber temperature on the analytical response of a swipe-based thermal desorption ion mobility spectrometer (IMS) for detection of trace explosives. IMS response for several common high explosives ranging from 0.1 ng to 100 ng was measured over a thermal desorber temperature range from 60 °C to 280 °C. Most of the explosives examined demonstrated a well-defined maximum IMS signal response at a temperature slightly below the melting point. Optimal temperatures, giving the highest IMS peak intensity, were 80 °C for trinitrotoluene (TNT), 100 °C for pentaerythritol tetranitrate (PETN), 160 °C for cyclotrimethylenetrinitramine (RDX) and 200 °C for cyclotetramethylenetetranitramine (HMX). By modifying the desorber temperature, we were able to increase cumulative IMS signal by a factor of 5 for TNT and HMX, and by a factor of 10 for RDX and PETN. Similar signal enhancements were observed for the same compounds formulated as plastic-bonded explosives (Composition 4 (C-4), Detasheet, and Semtex). In addition, mixtures of the explosives exhibited similar enhancements in analyte peak intensities. The increases in sensitivity were obtained at the expense of increased analysis times of up to 20 seconds. A slow sample heating rate as well as slower vapor-phase analyte introduction rate caused by low-temperature desorption enhanced the analytical sensitivity of individual explosives, plastic-bonded explosives, and explosives mixtures by IMS. Several possible mechanisms that can affect IMS signal response were investigated such as thermal degradation of the analytes, ionization efficiency, competitive ionization from background, and aerosol emission. PMID:22498665

  18. EFFECTS OF TEMPERATURE AND PRESSURE ON PARTICLE COLLECTION MECHANISMS: EXPERIMENTAL PROGRAM

    EPA Science Inventory

    The report gives results of a theoretical and experimental investigation of the effects of high temperatures and high pressures (HTPs) on fundamental particle collection mechanisms. It gives experimental results of inertial impaction, cyclone separation, Brownian diffusion, and e...

  19. Laser-induced acoustic desorption of natural and functionalized biochromophores.

    PubMed

    Sezer, U?ur; Wörner, Lisa; Horak, Johannes; Felix, Lukas; Tüxen, Jens; Götz, Christoph; Vaziri, Alipasha; Mayor, Marcel; Arndt, Markus

    2015-06-01

    Laser-induced acoustic desorption (LIAD) has recently been established as a tool for analytical chemistry. It is capable of launching intact, neutral, or low charged molecules into a high vacuum environment. This makes it ideally suited to mass spectrometry. LIAD can be used with fragile biomolecules and very massive compounds alike. Here, we apply LIAD time-of-flight mass spectrometry (TOF-MS) to the natural biochromophores chlorophyll, hemin, bilirubin, and biliverdin and to high mass fluoroalkyl-functionalized porphyrins. We characterize the variation in the molecular fragmentation patterns as a function of the desorption and the VUV postionization laser intensity. We find that LIAD can produce molecular beams an order of magnitude slower than matrix-assisted laser desorption (MALD), although this depends on the substrate material. Using titanium foils we observe a most probable velocity of 20 m/s for functionalized molecules with a mass m = 10?000 Da. PMID:25946522

  20. 137Cs desorption from lichen using acid solutions

    NASA Astrophysics Data System (ADS)

    ?u?ulovi?, A. A.; Veselinovi?, D.; Miljani?, S. S.

    2009-09-01

    Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl ( A) and HNO3 ( B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions were the most successful. Lichen desorbed with the stated solutions did not undergo structural changes. The amount of absorbed water from solutions A and B, used for desorption from lichen, in relation to the starting volume (expressed in %) showed that solution concentration did not take place. Lichen act as neutralizing agents because the pH of the lichen thallus is higher than the pH value of the solution used

  1. Laser-Induced Acoustic Desorption of Natural and Functionalized Biochromophores

    PubMed Central

    2015-01-01

    Laser-induced acoustic desorption (LIAD) has recently been established as a tool for analytical chemistry. It is capable of launching intact, neutral, or low charged molecules into a high vacuum environment. This makes it ideally suited to mass spectrometry. LIAD can be used with fragile biomolecules and very massive compounds alike. Here, we apply LIAD time-of-flight mass spectrometry (TOF-MS) to the natural biochromophores chlorophyll, hemin, bilirubin, and biliverdin and to high mass fluoroalkyl-functionalized porphyrins. We characterize the variation in the molecular fragmentation patterns as a function of the desorption and the VUV postionization laser intensity. We find that LIAD can produce molecular beams an order of magnitude slower than matrix-assisted laser desorption (MALD), although this depends on the substrate material. Using titanium foils we observe a most probable velocity of 20 m/s for functionalized molecules with a mass m = 10?000 Da. PMID:25946522

  2. Silicon thermal oxidation and its thermal desorption investigated by Si 2p core-level photoemission

    NASA Astrophysics Data System (ADS)

    Enta, Y.; Nakazawa, H.; Sato, S.; Kato, H.; Sakisaka, Y.

    2010-06-01

    Initial thermal oxidation of silicon and thermal desorption of silicon oxide have been investigated by Si 2p core-level photoemission with synchrotron radiation. The surface reaction processes are discussed from the difference in the chemically-shifted components, especially suboxides. On the thermal oxidation, time evolutions of suboxide intensities show a distinct temperature dependence, which is explained by two growth modes for the oxidation: first-order Langmuir-type adsorption mode and two-dimensional island growth mode at oxidation temperatures below and above 650 °C, respectively. On the thermal desorption, the spectrum for the thermal oxide followed by annealing at 1000 °C for 30 s in vacuum, whose thickness is nominally estimated at 3.7 Å, are compared with the 3.3 Å-thickness thermal oxide without the process of the annealing. The intensities of the suboxide components are considerably different between them, which can be explained by the formation and lateral growth of the voids in the annealed oxide layer.

  3. Distinguishibility of Oxygen Desorption From the Surface Region with Mobility Dominant Effects in Nanocrystalline Ceria Films

    SciTech Connect

    Saraf, Laxmikant V.; Shutthanandan, V.; Zhang, Yanwen; Thevuthasan, Suntharampillai; Wang, Chong M.; El-Azab, Anter; Baer, Donald R.

    2004-11-15

    We present an investigation of oxygen (18O) uptake measurements in 1 ?m thick nanocrystalline ceria films grown on single crystal Al?O? (0001) by nuclear reaction analysis (NRA). Oxygen uptake measurements were carried out in the temperature range of 200 0C-600 0C at a background 18O pressure of 4.0 x 10-6 Torr. Average grain-size in the as-grown films, synthesized by sol-gel process was ~ 3 nm confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) measurements. From the diffusion depth profiles, changes in intensity and slopes in surface and interface regions indicate dominating oxygen mobility effects. Oxygen desorption is clearly distinguishable in the film surface region as a result of shift in the oxygen peak intensity. It is argued that high defect density in nanocrystalline ceria which is associated with nano-grain surface combined with intermediate temperature reducing environment triggers multiple processes like diffusion, desorption and exchange interaction. The promising nature of NRA is realized as an effective tool to acquire the depth-dependent information regarding such complex reactions that exists in nanocrystalline environment.

  4. Distinguishibility of oxygen desorption from the surface region with mobility dominant effects in nanocrystalline ceria films

    NASA Astrophysics Data System (ADS)

    Saraf, Laxmikant; Shutthanandan, V.; Zhang, Y.; Thevuthasan, S.; Wang, C. M.; El-Azab, Anter; Baer, Donald R.

    2004-11-01

    We present an investigation of oxygen (O18) uptake measurements in 1?m thick nanocrystalline ceria films grown on single crystal Al2O3(0001) by nuclear reaction analysis (NRA). Oxygen uptake measurements were carried out in the temperature range of 200-600°C at a background O18 pressure of 4.0×10-6Torr. Average grain size in the as-grown films, synthesized by sol-gel process was ˜3nm confirmed by high-resolution transmission electron microscopy and x-ray diffraction measurements. From the diffusion depth profiles, changes in intensity and slopes in surface and interface regions indicate complex oxygen mobility effects. Oxygen desorption is clearly distinguishable in the film surface region as a result of shift in the oxygen concentration maxima. It is argued that high defect density in nanocrystalline ceria which is associated with nanograin surface combined with intermediate temperature reducing environment triggers multiple processes such as molecular and ionic diffusion, adsorption, desorption, and isotope exchange interactions. The promising nature of NRA is realized as an effective tool to acquire the depth-dependent information from complex reactions existing in nanocrystalline environment.

  5. Positron and thermal desorption studies on He ion implanted nuclear graphite

    NASA Astrophysics Data System (ADS)

    Hu, Z.; Li, Z.; Zhou, Z.; Shi, C.; Schut, H.; Pappas, K.

    2014-04-01

    The positron beam Doppler Broadening (DB) and Thermal Helium Desorption Spectroscopy (THDS) techniques are applied to study the behavior of radiation induced point defects in IG-110 nuclear graphite. The defects are introduced by irradiation at room temperature with 200keV He+ at doses ranging from 1015 to 1017 He/cm2. In the thermal desorption spectroscopy, the release of He+ is observed between 500K and 800K. With increasing He+ implantation dose, the fraction of He+ desorbed decreases from 27% to 3%. In the DB-curves showing the S parameter values versus positron implantation depth, the derived vacancy type defect distribution are in accordance with those obtained by SRIM calculations. Subsequent annealing of the implanted samples in steps of 100K for 5 minutes up to 1200K shows a distinct decrease of the S parameter value to its reference value between 500K and 700K. This temperature interval corresponds to the literature values for single vacancy migration energy of 1-2eV.

  6. Determination of the carbon isotopic composition of whole/intact biological specimens using at-line direct thermal desorption to effect thermally assisted hydrolysis/methylation.

    PubMed

    Akoto, Lawrence; Vreuls, René J J; Irth, Hubertus; Floris, Virgilio; Hoogveld, Hans; Pel, Roel

    2008-04-01

    In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography-combustion isotope-ratio mass spectrometry (GC/C-IRMS) analysis of whole/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped programmed-temperature vaporizer (PTV) liners to the PTV injector and chemical derivatisation (thermally assisted hydrolysis/methylation; THM) such that a profile of a cellular fatty acids is obtained. Flow-cytometric sorted microalgae and handpicked zooplankton are used as samples with trimethylsulfonium hydroxide (TMSH) as methylating reagent. A major advantage of this novel approach over the Curie-point technique is the automation of the total procedure, which allows unattended analysis of large sample series. The profiles and delta(13)C carbon isotopic signatures of the fatty acid methyl esters (FAMEs) produced are very similar to those obtained using the Curie-point flash pyrolysis method. It is shown that algal samples must be kept no longer than 48 h in the DTD sample tray prior to the THM-analysis in order to maintain the integrity of their FAME profile. PMID:17897655

  7. Explosive desorption of icy grain mantles in dense clouds

    NASA Technical Reports Server (NTRS)

    Schutte, W. A.; Greenberg, J. M.

    1991-01-01

    The cycling of the condensible material in dense clouds between the gas phase and the icy grain mantles is investigated. In the model studied, desorption of the ice occurs due to grain mantle explosions when photochemically stored energy is released after transient heating by a cosmic ray particle. It is shown that, depending on the grain size distribution in dense clouds, explosive desorption can maintain up to about eight percent of the carbon in the form of CO in the gas phase at typical cloud densities.

  8. 137 Cs desorption from lichen using acid solutions

    Microsoft Academic Search

    A. A. ?u?ulovi?; D. Veselinovic; S. S. Miljanic

    2009-01-01

    Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl (A) and HNO3 (B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was\\u000a shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions

  9. Results of an interlaboratory fatigue test program conducted on alloy 800H at room and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Ellis, J. R.

    1985-01-01

    The experimental approach adopted for low cycle fatigue tests of alloy 800H involved the use of electrohydraulic test systems, hour glass geometry specimens, diametral extensometers, and axial strain computers. Attempts to identify possible problem areas were complicated by the lack of reliable data for the heat of Alloy 800H under investigation. The method adopted was to generate definitive test data in an Interlaboratory Fatigue Test Program. The laboratories participating in the program were Argonne National Laboratory, Battelle Columbus, Mar-Test, and NASA Lewis. Fatigue tests were conducted on both solid and turbular specimens at temperatures of 20, 593, and 760 C and strain ranges of 2.0, 1.0, and 0.5 percent. The subject test method can, under certain circumstances, produce fatigue data which are serious in error. This approach subsequently was abandoned at General Atomic Company in favor of parallel gage length specimens and axial extensiometers.

  10. Results of an interlaboratory fatigue test program conducted on alloy 800H at room and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Ellis, J. R.

    1987-01-01

    The experimental approach adopted for low cycle fatigue tests of alloy 800H involved the use of electrohydraulic test systems, hour glass geometry specimens, diametral extensometers, and axial strain computers. Attempts to identify possible problem areas were complicated by the lack of reliable data for the heat of Alloy 800H under investigation. The method adopted was to generate definitive test data in an Interlaboratory Fatigue Test Program. The laboratories participating in the program were Argonne National Laboratory, Battelle Columbus, Mar-Test, and NASA Lewis. Fatigue tests were conducted on both solid and turbular specimens at temperatures of 20, 593, and 760 C and strain ranges of 2.0, 1.0, and 0.5 percent. The subject test method can, under certain circumstances, produce fatigue data which are serious in error. This approach subsequently was abandoned at General Atomic Company in favor of parallel gage length specimens and axial extensometers.

  11. Fast DNA separations using poly(ethylene oxide) in non-denaturing medium with temperature programming.

    PubMed

    Fung, E N; Pang, H M; Yeung, E S

    1998-05-01

    We demonstrated fast DNA separations in low viscosity entangled solutions with a temperature gradient in a non-denaturing separation medium. The separations were carried out in a solution of commercially available poly(ethylene oxide) (PEO) [1 x Tris(hydroxymethyl)aminomethane borate buffer, without urea] with a temperature gradient of 2 degrees C/min. The performance was compared with that of a solution of PEO with urea at ambient temperature. We found that the former condition gives sufficient resolution for accurate base calling and that in general, it gave better separation for fragments larger than 450 base pairs (bp). Most importantly, the separation speed approaches 30 bp/min. In addition, we describe a simple yet reliable gel preparation protocol for such separations. PMID:9639886

  12. A report on the use of thermal scanner data in an operational program for monitoring apparent rooftop temperatures

    NASA Technical Reports Server (NTRS)

    Bjorklund, J.; Schmer, F. A.; Isakson, R. E.

    1975-01-01

    CENGAS, a division of Central Telephone and Utilities Corporation in cooperation with the Remote Sensing Institute, South Dakota State University, is using airborne thermal scanner data to monitor relative rooftop temperatures. Four Nebraska communities and one South Dakota community were surveyed by the Remote Sensing Institute for CENGAS. Thermal scanner data were converted to a film format and the resultant imagery has been successfully employed by CENGAS. The program places emphasis on heat losses resulting from inadequate home insulation, offers CENGAS customers the opportunity to observe a thermogram of their rooftop, and assists homeowners in evaluating insulation needs.

  13. Molecular desorption of stainless steel vacuum chambers irradiated with 4.2 MeV/u lead ions

    NASA Astrophysics Data System (ADS)

    Mahner, E.; Hansen, J.; Laurent, J.-M.; Madsen, N.

    2003-01-01

    In preparation for the heavy ion program of the Large Hadron Collider at CERN, accumulation and cooling tests with lead ion beams have been performed in the Low Energy Antiproton Ring. These tests have revealed that due to the unexpected large outgassing of the vacuum system, the dynamic pressure of the ring could not be maintained low enough to reach the required beam intensities. To determine the actions necessary to lower the dynamic pressure rise, an experimental program has been initiated for measuring the molecular desorption yields of stainless steel vacuum chambers by the impact of 4.2 MeV/u lead ions with the charge states +27 and +53. The test chambers were exposed either at grazing or at perpendicular incidence. Different surface treatments (glow discharges, nonevaporable getter coating) are reported in terms of the molecular desorption yields for H2, CH4, CO, Ar, and CO2. Unexpected large values of molecular yields per incident ion up to 2×104 molecules/ion have been observed. The reduction of the ion-induced desorption yield due to continuous bombardment with lead ions (beam cleaning) has been investigated for five different stainless steel vacuum chambers. The implications of these results for the vacuum system of the future Low Energy Ion Ring and possible remedies to reduce the vacuum degradation are discussed.

  14. USING METHANOL-WATER SYSTEMS TO INVESTIGATE PHENANTHRENE SORPTION-DESORPTION ON SEDIMENT

    EPA Science Inventory

    Sorption isotherm nonlinearity, sorption-desorption hysteresis, slow desorption kinetics, and other nonideal phenomena have been attributed to the differing sorptive characteristics of the natural organic matter (NOM) polymers associated with soils and sediments. A conceptualizat...

  15. Assessment of the high temperature fission chamber technology for the French fast reactor program

    SciTech Connect

    Jammes, C.; Filliatre, P.; Geslot, B.; Domenech, T.; Normand, S. [Commissariat a l'Energie Atomique, CEA (France)

    2011-07-01

    High temperature fission chambers are key instruments for the control and protection of the sodium-cooled fast reactor. First, the developments of those neutron detectors, which are carried out either in France or abroad are reviewed. Second, the French realizations are assessed with the use of the technology readiness levels in order to identify tracks of improvement. (authors)

  16. EPA AND ERDA HIGH-TEMPERATURE/HIGH-PRESSURE PARTICULATE CONTROL PROGRAMS

    EPA Science Inventory

    The report describes and compares current projects sponsored by EPA and the U.S. Energy Research and Development Administration (ERDA), relating to the control of particulate matter in fuel gas streams at high temperatures (1000 to 2000F) and high pressures (5 atm and greater). T...

  17. Sorption and desorption characteristics of a packed bed of clay-CaCl{sub 2} desiccant particles

    SciTech Connect

    Tretiak, C.S.; Abdallah, N. Ben [Department of Process Engineering and Applied Science, Dalhousie University, P.O. Box 1000, Halifax, Nova Scotia (Canada)

    2009-10-15

    Desiccants can be used in conjunction with solar energy to provide a viable alternative to traditional air conditioning techniques. A desiccant consisting of clay and calcium chloride was developed and tested using multiple sorption and desorption cycles. During sorption, inlet air temperatures from 23 to 36 C with corresponding relative humidities of 42-66% were tested. Additionally, superficial air velocities from 0.17 to 0.85 m/s were tested. During desorption, inlet air temperatures from 50 to 57 C and superficial air velocities of approximately 0.30 and 0.60 m/s were tested. A regression equation was determined for the mass of water sorbed by the clay-CaCl2 desiccant with a R{sup 2} value of 0.917. The desorption data was regressed to an exponential function and significant k-values were determined. An equation for pressure drop through the desiccant was determined and compared to existing models. The desiccant was found to perform well during the repeated test cycles though small masses of desiccant were lost due to surface disintegration of the desiccant spheres. (author)

  18. Effects of SWNT and metallic catalyst on hydrogen absorption/desorption performance of MgH2.

    PubMed

    Wu, Chengzhang; Wang, Ping; Yao, Xiangdong; Liu, Chang; Chen, Demin; Lu, Gao Qing; Cheng, Huiming

    2005-12-01

    The microstructure and absorption/desorption characteristics of composite MgH2 and 5 wt % as-prepared single-walled carbon nanotubes (MgH2-5ap) obtained by the mechanical grinding method were investigated. Experimental results show that the MgH2-5ap sample exhibits faster absorption kinetics and relatively lower desorption temperature than pure MgH2 or MgH2-purified single-walled carbon nanotube composite. Storage capacities of 6.0 and 4.2 wt % hydrogen for the MgH2-5ap composite were achieved in 60 min at 423 and 373 K, respectively. Furthermore, its desorption temperature was reduced by 70 K due to the introduction of as-prepared single-walled carbon nanotubes (SWNTs). In addition, the different effects of SWNTs and metallic catalysts contained in the as-prepared SWNTs were also investigated and a hydrogenation mechanism was proposed. It is suggested that metallic particles may be mainly responsible for the improvement of the hydrogen absorption kinetics, and SWNTs for the enhancement of hydrogen absorption capacity of MgH2. PMID:16853892

  19. A laser-induced fluorescence study of OH desorption from Pt(111) during oxidation of hydrogen in O2 and decomposition of water

    NASA Astrophysics Data System (ADS)

    Fridell, Erik; Elg, Alf-Peter; Rosén, Arne; Kasemo, Bengt

    1995-04-01

    The desorption of OH radicals from Pt(111) at high temperature, ?1000 K, during the water formation (H2+1/2 O2?H2O) and water decomposition reactions, respectively, was investigated using the laser-induced fluorescence technique. The results are compared with corresponding data from our laboratory for polycrystalline Pt. The OH desorption rate in H2+O2 at 1-100 mTorr total pressure has its maximum at 8%-9% relative H2 concentration for surface temperatures between 1100 and 1400 K. With H2 replaced by D2, the OD desorption rate maximizes at somewhat higher relative hydrogen content. The apparent activation energy for OH desorption increases from about 1.4 eV at low relative hydrogen concentration to about 2.0 eV at hydrogen contents of 25% or more. For the water decomposition reaction, the apparent activation energy for OH desorption was found to be 1.7±0.2 eV at 0.5 Torr and 1.9±0.2 eV at 1 Torr. These differences in apparent activation energies are primarily due to kinetic effects. The results are analyzed within a kinetic model previously developed by Hellsing et al. [J. Catal. 132, 210 (1991)], and are also compared with previous data for polycrystalline Pt. The kinetic model calculations give good overall agreement with the measured OH desorption rates as functions of temperature, H2/O2 mixture and H2O pressure, respectively. A nonuniqueness problem, with respect to the choice of kinetic parameters, is encountered in the simulation of the measured data; quite different sets of two of the kinetic constants, namely the activation energy for water formation (via OH+H?H2O) and the activation energy for OH desorption can reproduce the data as long as their difference is constant. This nonuniqueness problem, which is a consequence of the steady-state nature of the measurements, is analyzed and discussed in some detail, as are some apparent contradictions in the absolute values of reported kinetic constants in the literature. From this analysis two important conclusions are drawn. (i) The apparent contradictions in the literature about absolute values of activation energies for the water formation reaction and for OH-desorption may be less severe than believed or nonexistent. (ii) Coverage dependent activation energies must be considered and experimental exploration of such coverage dependencies are needed to create a firmer base for the kinetic modeling of the H2/O2 reaction on Pt.

  20. Effect of internal and external conditions on ionization processes in the FAPA ambient desorption/ionization source.

    PubMed

    Orejas, Jaime; Pfeuffer, Kevin P; Ray, Steven J; Pisonero, Jorge; Sanz-Medel, Alfredo; Hieftje, Gary M

    2014-11-01

    Ambient desorption/ionization (ADI) sources coupled to mass spectrometry (MS) offer outstanding analytical features: direct analysis of real samples without sample pretreatment, combined with the selectivity and sensitivity of MS. Since ADI sources typically work in the open atmosphere, ambient conditions can affect the desorption and ionization processes. Here, the effects of internal source parameters and ambient humidity on the ionization processes of the flowing atmospheric pressure afterglow (FAPA) source are investigated. The interaction of reagent ions with a range of analytes is studied in terms of sensitivity and based upon the processes that occur in the ionization reactions. The results show that internal parameters which lead to higher gas temperatures afforded higher sensitivities, although fragmentation is also affected. In the case of humidity, only extremely dry conditions led to higher sensitivities, while fragmentation remained unaffected. PMID:25178932

  1. Computer program MCAP-TOSS calculates steady-state fluid dynamics of coolant in parallel channels and temperature distribution in surrounding heat-generating solid

    NASA Technical Reports Server (NTRS)

    Lee, A. Y.

    1967-01-01

    Computer program calculates the steady state fluid distribution, temperature rise, and pressure drop of a coolant, the material temperature distribution of a heat generating solid, and the heat flux distributions at the fluid-solid interfaces. It performs the necessary iterations automatically within the computer, in one machine run.

  2. Summary Report on FY12 Small-Scale Test Activities High Temperature Electrolysis Program

    SciTech Connect

    James O'Brien

    2012-09-01

    This report provides a description of the apparatus and the single cell testing results performed at Idaho National Laboratory during January–August 2012. It is an addendum to the Small-Scale Test Report issued in January 2012. The primary program objectives during this time period were associated with design, assembly, and operation of two large experiments: a pressurized test, and a 4 kW test. Consequently, the activities described in this report represent a much smaller effort.

  3. Desorption of Arsenic from Drinking Water Distribution System Solids

    EPA Science Inventory

    Given the limited knowledge regarding the soluble release of arsenic from DWDS solids, the objectives of this research were to: 1) investigate the effect of pH on the dissolution/desorption of arsenic from DWDS solids, and 2) examine the effect of orthophosphate on the soluble re...

  4. Biosorption of cadmium by algal biomass: Adsorption and desorption characteristics

    Microsoft Academic Search

    K. H. Chu; M. A. Hashim; S. M. Phang; V. B. Samuel

    1997-01-01

    The adsorption and desorption characteristics of a biosorption process comprising the biomass of the marine alga Sargassum baccularia, cadmium ions and desorbing agents hydrochloric acid and ethylenediaminetetraacetic acid (EDTA) were investigated using a batch reactor system. Both desorbents were effective in stripping adsorbed cadmium from the biomass. It was found that HCl at pH 2 could desorb 80% of the

  5. Sorption-desorption of aminocyclopyrachlor in selected Brazilian soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aminocyclopyrachlor sorption and desorption was investigated in 14 soils from Brazil, representing a range of pH, and organic carbon (OC) and clay contents. Sorption kinetics demonstrated that soil-solution equilibrium was attained in a 24-h period. Freundlich equation adequately described behavior ...

  6. Influence of desorption on the indoor concentration of toxic gases

    Microsoft Academic Search

    Edvard Karlsson; Ueli Huber

    1996-01-01

    A theoretical model is developed which considers the influence of both deposition and desorption processes on the indoor concentration of toxic gases. The model is based on a simplification of the Langmuir theory. Model parameters for NH3, Cl2, the nerve agent sarin, and a simulant for the nerve agent VX are calculated from available experiments with common indoor materials. The

  7. Kinetics of nitric oxide desorption from carbonaceous surfaces

    E-print Network

    Truong, Thanh N.

    Kinetics of nitric oxide desorption from carbonaceous surfaces Alejandro Montoya a , Fanor Mondrago of nitrogen-containing chars, the evolution of nitric oxide, (CNO) ! NO+(C*). Density functional theory.V. All rights reserved. Keywords: Nitric oxide; Carbonaceous surface; Chars 1. Introduction

  8. Sorption-desorption of indaziflam in selected agricultural soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sorption and desorption of indaziflam in 6 soils from Brazil and 3 soils from the USA, with different physical chemical properties, were investigated using the batch equilibration method. Sorption kinetics demonstrated that soil-solution equilibrium was attained in a 24-h period. The Freundlich equa...

  9. Nonthermal desorption from surfaces of ices and other oxides

    NASA Astrophysics Data System (ADS)

    Madey, Theodore E.

    2001-03-01

    Non-thermal DIET processes at surfaces (desorption induced by electronic transitions) may affect both terrestrial and planetary atmospheres. One case concerns observations of neutral sodium and potassium vapor in the tenuous atmospheres of the planet Mercury and the Moon, as well as Jupiter's icy satellite, Europa. In a series of model experiments, we find strong evidence that non-thermal processes - mainly photon-stimulated desorption (PSD) by UV photons - play a dominant role in desorption of Na atoms from the lunar surface, and may affect Na and K in the other atmospheres also. The second case involves measurements that may impact on understanding the destruction of ozone-depleting chlorofluorocarbons (CFCs) in the earth's upper atmosphere, via electron-induced processes on ice particles in polar stratospheric clouds. We observe giant Cl^- and F^- enhancements by several orders of magnitude in electron-stimulated desorption (ESD) of a fractional monolayer of CF_2Cl2 coadsorbed with water ice and ammonia ice on a metal surface at ~25 K, respectively. The negative-ion enhancements are attributed to dissociation of CF_2Cl2 by capture of low-energy secondary electrons trapped by coadsorbed polar water or ammonia.

  10. Cadmium Sorption and Desorption in Soils: A Review

    Microsoft Academic Search

    PARIPURNANDA LOGANATHAN; SARAVANAMUTHU VIGNESWARAN; JAYA KANDASAMY; RAVI NAIDU

    2012-01-01

    Cadmium (Cd) is an environmental pollutant that can be readily taken up by plants and may enter the food chain, causing risk to human health. It can also affect soil quality and, if easily leached, has the potential to pollute surface and ground waters. Sorption and desorption are critical processes controlling the phytoavailability and mobility of Cd in soils. The

  11. Cadmium sorption and desorption in soils—a review

    Microsoft Academic Search

    Paripurnanda Loganathan; Saravanamuthu Vigneswaran; Jaya Kandasamy; Ravi Naidu

    2011-01-01

    Cadmium (Cd) is an environmental pollutant that can be readily taken-up by plants and may enter the food chain causing risk to human health. It can also affect soil quality and, if easily leached, has the potential to pollute surface and ground waters. Sorption and desorption are critical processes controlling the phyto-availability and mobility of Cd in soils. This paper

  12. Nitrate sorption and desorption in biochars from fast pyrolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing the nitrate (NO3-) sorption capacity of Midwestern US soils has the potential to reduce nitrate leaching to ground water and reduce the extent of the hypoxia zone in the Gulf of Mexico. The objective of this study was to determine the sorption and desorption capacity of non-activated and ...

  13. Sorption and desorption of quaternary amine cations on clays

    Microsoft Academic Search

    Z. Zhong Zhang; Donald L. Sparks; Noel C. Scrivner

    1993-01-01

    The authors have studied the sorption and desorption of three quaternary amines, namely, nonyltrimethylammonium, dodecyltrimethylammonium, and hexadecyltrimethylammonium, on homoionic Na- and K-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were sorbed on the montmorillonite when the added amines were less than 70% of the cation-exchange capacity of the montmorillonite. Sorption of

  14. Water absorption and desorption in shuttle ablator and insulation materials

    NASA Technical Reports Server (NTRS)

    Whitaker, A. F.; Smith, C. F.; Wooden, V. A.; Cothren, B. E.; Gregory, H.

    1982-01-01

    Shuttle systems ablator and insulation materials underwent water soak with subsequent water desorption in vacuum. Water accumulation in these materials after a soak for 24 hours ranged from +1.1% for orbiter tile to +161% for solid rocket booster MSA-1. After 1 minute in vacuum, water retention ranged from none in the orbiter tile to +70% for solid rocket booster cork.

  15. Liquid chromatography of polymers under limiting conditions of desorption

    Microsoft Academic Search

    Marián Šnauko; Dušan Berek

    2005-01-01

    Liquid chromatography under limiting conditions of desorption (LC LCD) is a method which allows molar mass independent elution of various synthetic polymers. A narrow, slowly moving zone of small molecules, which promotes full adsorption of one kind of polymer species within column (an adsorli) acts as an impermeable barrier for the fast moving macromolecules. The latter accumulate on the barrier

  16. Matrix-assisted Laser Desorption of *Peptidesin Transmission Geometry

    E-print Network

    Vertes, Akos

    ~~~_ Matrix-assisted Laser Desorption of *Peptidesin Transmission Geometry Akos Vertes* Laszlo, Francc The possibility of performing matrix-assisted laser &sorption experiments in trknsmission geometry in the high mass region. The question addressed in this Communication con- cerns the geometry of laser

  17. DEMONSTRATION BULLETIN: THERMAL DESORPTION SYSTEM - CLEAN BERKSHIRES, INC.

    EPA Science Inventory

    A thermal desorption system (TDS) has been developed by Clean Berkshires, Inc. (CBI), Lanesboro, Massachusetts for ex-situ treatment of soils and other media contaminated with organic pollutants. The TDS uses heat as both a physical separation mechanism and as a means to destro...

  18. Desorption Kinetics for Field-Aged Polycyclic Aromatic Hydrocarbons

    E-print Network

    Rockne, Karl J.

    Harbor Estuary. Desorption kinetics for PAHs with a log octanol- water partition coefficient greater than- mesopore diffusion mechanism. The model-predicted fraction of PAHs in the fast-diffusion regime by compound-sediment organic matter (SOM) (6-9). Several reports examining pore dif- fusion versus organic matter diffusion

  19. 182 28th ANNUAL eMS Sorption and Desorption of Quaternary Amine Cations on Clays

    E-print Network

    Sparks, Donald L.

    182 28th ANNUAL eMS Sorption and Desorption of Quaternary Amine Cations on Clays Z. Z. Zhang and D? The present study was conducted to investigate the sorption and desorption of several quaternary amines on Na of amines was conducted at an ionic strength of 0.01 M, and desorption of amines was studied by adding

  20. Angular distribution of the ejecta in matrix-assisted laser desorption/ionization: Model dependence

    E-print Network

    Johnson, Robert E.

    desorption/ionization (MALDI) was found to peak back toward the direction of illumination in the experiments between proposed models for MALDI. (Int J Mass Spectrom 177 (1998) 111­118) © 1998 Elsevier Science B.V. Keywords: Desorption; MALDI; Laser Introduction Matrix-assisted laser desorption/ionization (MALDI) has

  1. Rotational dynamics of desorption and inelastic scattering for the NO/Pt(111) system

    E-print Network

    Zare, Richard N.

    enhanced Raman spectroscopy (SERS), electron stimulated desorption ion angular distri- bution (ESDIADRotational dynamics of desorption and inelastic scattering for the NO/Pt(111) system D. C. Jacobs://avspublications.org/jvsta/about/rights_and_permissions #12;Rotational dynamics of desorption and inelastic scattering for the NO/ Pt(111) system D. C. Jacobs

  2. Development of Designer Diamond Anvils for High Pressure-High-Temperature Experiments in Support of the Stockpile Stewardship Program

    SciTech Connect

    Yogesh K. Vohra

    2005-05-12

    The focus of this program at the University of Alabama at Birmingham (UAB) is to develop the next generation of designer diamond anvils that can perform simultaneous joule heating and temperature profile measurements in a diamond anvil cell. A series of tungsten-rhenium thermocouples will be fabricated onto to the anvil and encapsulated by a chemical vapor deposited diamond layer to allow for a complete temperature profile measurement across the anvil. The tip of the diamond anvil will be engineered to reduce the thermal conductivity so that the tungsten-heating coils can be deposited on top of this layer. Several different approaches will be investigated to engineer the tip of the diamond anvil for reduction in thermal conductivity (a) isotopic mixture of 12C and 13C in the diamond layer, (b) doping of diamond with impurities (nitrogen and/or boron), and (c) growing diamond in a higher concentration of methane in hydrogen plasma. Under this academic alliance with Lawrence Livermore National Laboratory (LLNL), PI and his graduate students will use the lithographic and diamond polishing facility at LLNL. This proposed next generation of designer diamond anvils will allow multi-tasking capability with the ability to measure electrical, magnetic, structural and thermal data on actinide materials with unparallel sensitivity in support of the stockpile stewardship program.

  3. A Computer Program for the Computation of Running Gear Temperatures Using Green's Function

    NASA Technical Reports Server (NTRS)

    Koshigoe, S.; Murdock, J. W.; Akin, L. S.; Townsend, D. P.

    1996-01-01

    A new technique has been developed to study two dimensional heat transfer problems in gears. This technique consists of transforming the heat equation into a line integral equation with the use of Green's theorem. The equation is then expressed in terms of eigenfunctions that satisfy the Helmholtz equation, and their corresponding eigenvalues for an arbitrarily shaped region of interest. The eigenfunction are obtalned by solving an intergral equation. Once the eigenfunctions are found, the temperature is expanded in terms of the eigenfunctions with unknown time dependent coefficients that can be solved by using Runge Kutta methods. The time integration is extremely efficient. Therefore, any changes in the time dependent coefficients or source terms in the boundary conditions do not impose a great computational burden on the user. The method is demonstrated by applying it to a sample gear tooth. Temperature histories at representative surface locatons are given.

  4. A Time-Domain Sub-Micro Watt Temperature Sensor With Digital Set-Point Programming

    Microsoft Academic Search

    Poki Chen; Tuo-Kuang Chen; Yu-Shin Wang; Chun-Chi Chen

    2009-01-01

    To realize the on-chip temperature monitoring of VLSI circuits, an accurate time-domain low-power CMOS thermostat based on delay lines is proposed. Contrary to the voltage-domain predecessors, the proposed circuit can benefit from the performance enhancement due to the scaling down of fabrication processes. By replacing R-string voltage division and voltage comparator with delay line time division and time comparator, only

  5. Concentration-dependent kinetics of pollutant desorption from soils.

    PubMed

    Braida, Washington J; White, Jason C; Zhao, Dongye; Ferrandino, Francis J; Pignatello, Joseph J

    2002-12-01

    Sorption-desorption kinetics play a major role in transport and bioavailability of pollutants in soils. Contaminant concentration is a potentially important factor controlling kinetics. A previous paper dealt with the effect of solute concentration on fractional uptake rates of phenanthrene and pyrene from a finite aqueous source. In this study we determined the effect of initial phenanthrene sorbed concentration (q(0)) on the fractional mass desorption rates from each of six soils to a zero-concentration solution, approximated by including a polymer adsorbent (Tenax) as a third-phase sink. The soils were preequilibrated with phenanthrene for 180 d. Consistent with theory, the fractional desorption rates determined by empirical curve fitting increased with q(0) provided the isotherm was nonlinear. After 500 to 600 d of desorption at the steepest possible concentration gradient, all soils retained a highly resistant fraction, which ranged from 4 to 31% of q(0), except for one soil at a high q(0). The highly resistant fraction decreased with increasing q(0), for nonlinear isotherm cases, but increased with q(0) for linear or nearly linear isotherm cases. Application of a nonlinear diffusion model, the dual-mode diffusion model (DMDM), to the nonresistant fraction gave reasonably good fits. The DMDM attributes the increase with concentration of the apparent diffusivity to a decrease in the proportion of sorbate occupying immobile sites (holes) in soil organic matter. The concentration-dependent term in the expression for the apparent diffusivity correlated with either of two indices that reflect the linearity of the sorption isotherm. Bunker C oil present in one soil acted as a partition domain. The findings of this study are consistent with heterogeneous models of soil organic matter, and indicate that concentration effects should be taken into account whenever desorption rate is important. PMID:12463551

  6. Investigations into ultraviolet matrix-assisted laser desorption

    SciTech Connect

    Heise, T.W.

    1993-07-01

    Matrix-assisted laser desorption (MALD) is a technique for converting large biomolecules into gas phase ions. Some characteristics of the commonly used uv matrices are determined. Solubilities in methanol range from 0.1 to 0.5 M. Solid phase absorption spectra are found to be similar to solution, but slightly red-shifted. Acoustic and quartz crystal microbalance signals are investigated as possible means of uv-MALD quantitation. Evidence for the existence of desorption thresholds is presented. Threshold values are determined to be in the range of 2 to 3 MW/cm{sup 2}. A transient imaging technique based on laser-excited fluorescence for monitoring MALD plumes is described. Sensitivity is well within the levels required for studying matrix-assisted laser desorption, where analyte concentrations are significantly lower than those in conventional laser desorption. Results showing the effect of film morphology, particularly film thickness, on plume dynamics are presented. In particular, MALD plumes from thicker films tend to exhibit higher axial velocities. Fluorescent labeling of protein and of DNA is used to allow imaging of their uv-MALD generated plumes. Integrated concentrations are available with respect to time, making it possible to assess the rate of fragmentation. The spatial and temporal distributions are important for the design of secondary ionization schemes to enhance ion yields and for the optimization of ion collection in time-of-flight MS instruments to maximize resolution. Such information could also provide insight into whether ionization is closely associated with the desorption step or whether it is a result of subsequent collisions with the matrix gas (e.g., proton transfer). Although the present study involves plumes in a normal atmosphere, adaptation to measurements in vacuum (e.g., inside a mass spectrometer) should be straightforward.

  7. Using temperature-programmed reaction for kinetic analysis of reactions in dilute aqueous solutions at high pressure

    SciTech Connect

    Brown, L.F.; Robinson, B.A.

    1986-01-01

    The technique of temperature-programmed reaction (TPR) is shown to be a practical experimental method for determining reaction-rate expressions and kinetics parameters for reactions in dilute aqueous solutions under high ambient pressure. By sampling and measuring the extent of reaction during a rise in temperature, information normally obtained from a series of isothermal batch kinetics experiments can be found in a single TPR test. The use of nonlinear least-squares regression eliminates the need to achieve a constant rate of temperature rise, simplifies the experimental requirements for TPR results, and gives more accurate answers than does a linear analysis of TPR results. Numerical simulations of TPR tests in the presence of random concentration-measurement error is used to assess the accuracy of the technique and to identify the best values of crucial operating parameters. The results of two TPR experiments measuring the alkaline hydrolysis of ethyl acetate demonstrate the applicability of the technique to reactions in dilute aqueous solutions at high pressure. These preliminary experimental results, along with numerical simulations, allow us to chart a course for future TPR kinetics experiments on a large number of similar reactions. 16 refs., 6 figs., 8 tabs.

  8. A low-power pressure-and temperature-programmed separation system for a micro gas chromatograph.

    SciTech Connect

    Sacks, Richard D. (University of Michigan, Ann Arbor, MI); Robinson, Alex Lockwood (Advanced Sensor Technologies, Albuquerque, NM); Lambertus, Gordon R. (University of Michigan, Ann Arbor, MI); Potkay, Joseph A. (University of Michigan, Ann Arbor, MI); Wise, Kensall D. (University of Michigan, Ann Arbor, MI)

    2006-10-01

    This thesis presents the theory, design, fabrication and testing of the microvalves and columns necessary in a pressure- and temperature-programmed micro gas chromatograph ({micro}GC). Two microcolumn designs are investigated: a bonded Si-glass column having a rectangular cross section and a vapor-deposited silicon oxynitride (Sion) column having a roughly circular cross section. Both microcolumns contain integrated heaters and sensors for rapid, controlled heating. The 3.2 cm x 3.2 cm, 3 m-long silicon-glass column, coated with a non-polar polydimethylsiloxane (PDMS) stationary phase, separates 30 volatile organic compounds (VOCs) in less than 6 min. This is the most efficient micromachined column reported to date, producing greater than 4000 plates/m. The 2.7 mm x 1.4 mm Sion column eliminates the glass sealing plate and silicon substrate using deposited dielectrics and is the lowest power and fastest GC column reported to date; it requires only 11 mW to raise the column temperature by 100 C and has a response time of 11s and natural temperature ramp rate of 580 C/min. A 1 m-long PDMS-coated Sion microcolumn separates 10 VOCs in 52s. A system-based design approach was used for both columns.

  9. Measurement of the volatility and glass transition temperatures of glasses produced during the DWPF startup test program

    SciTech Connect

    Marra, J.C.; Harbour, J.R.

    1995-10-18

    The Defense Waste Processing Facility (DWPF) will immobilize high-level radioactive waste currently stored in underground tanks at the Savannah River Site by incorporating the waste into a glass matrix. The molten waste glass will be poured into stainless steel canisters which will be welded shut to produce the final waste form. One specification requires that any volatiles produced as a result of accidentally heating the waste glass to the glass transition temperature be identified. Glass samples from five melter campaigns, run as part of the DWPF Startup Test Program, were analyzed to determine glass transition temperatures and to examine the volatilization (by weight loss). Glass transition temperatures (T{sub g}) for the glasses, determined by differential scanning calorimetry (DSC), ranged between 445 C and 474 C. Thermogravimetric analysis (TGA) scans showed that no overall weight loss occurred in any of the glass samples when heated to 500 C. Therefore, no volatility will occur in the final glass product when heated up to 500 C.

  10. Analysis of organic compounds in water by direct adsorption and thermal desorption. [Dissertation

    SciTech Connect

    Ryan, J.P. Jr.

    1980-03-01

    An instrument was designed and constructed that makes it possible to thermally desorb organic compounds from wet adsorption traps to a gas chromatograph in an efficient and reproducible manner. Based on this device, a method of analyzing organics in water was developed that is rapid, sensitive, and of broader scope than previously published methods. The system was applied to the analysis of compounds with a wide range of volatilities. Temperature and flow parameters were investigated and specific procedures for quantitation were established. Real samples, including tap water and well water, were also analyzed with this system. Depending on the analysis requirements, the thermal desorption instrument can be used with either packed column or high resolution open-tubular column gas chromatography. The construction plans of normal and high-resolution systems are presented along with chromatograms and data produced by each. Finally, an improved thermal desorption instrument is described. Modifications to the basic system, including splitless injection onto a capillary column, automation, dual cryogenic trapping, reduction of scale, and effluent splitting to dual detection are discussed at length as they relate to the improved instrument.

  11. Comparison of three plasma sources for ambient desorption/ionization mass spectrometry.

    PubMed

    McKay, Kirsty; Salter, Tara L; Bowfield, Andrew; Walsh, James L; Gilmore, Ian S; Bradley, James W

    2014-09-01

    Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources. PMID:24894843

  12. Photon- and electron-stimulated desorption from laboratory models of interstellar ice grains

    SciTech Connect

    Thrower, J. D.; Abdulgalil, A. G. M.; Collings, M. P.; McCoustra, M. R. S.; Burke, D. J.; Brown, W. A.; Dawes, A.; Holtom, P. J.; Kendall, P.; Mason, N. J.; Jamme, F.; Fraser, H. J.; Rutten, F. J. M. [School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH 14 4AS (United Kingdom); Department of Chemistry, University College London, 20 Gordon Street, London W1CH 0AJ (United Kingdom); Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); SOLEIL Synchrotron, BP 48, L'Orme des Merisiers, F-91192 Gif surf Yvette Cedex (France); Department of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, John Anderson Building, 107 Rottenrow East, Glasgow G4 0NG (United Kingdom); School of Pharmacy and iEPSAM, Keele University, Keele ST5 5BG (United Kingdom)

    2010-07-15

    The nonthermal desorption of water from ice films induced by photon and low energy electron irradiation has been studied under conditions mimicking those found in dense interstellar clouds. Water desorption following photon irradiation at 250 nm relies on the presence of an absorbing species within the H{sub 2}O ice, in this case benzene. Desorption cross sections are obtained and used to derive first order rate coefficients for the desorption processes. Kinetic modeling has been used to compare the efficiencies of these desorption mechanisms with others known to be in operation in dense clouds.

  13. Low-temperature selective catalytic reduction of NO with NH? over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route.

    PubMed

    Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

    2013-10-01

    Nanoflaky MnO(x) on carbon nanotubes (nf-MnO(x)@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH?. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N? adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H? temperature-programmed reduction (H?-TPR) and NH? temperature-programmed desorption (NH?-TPD). The SEM, TEM, XRD results and N? adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnO(x) and the obtained catalyst exhibited a large surface area as well. Compared with the MnO(x)/CNT and MnO(x)/TiO? catalysts prepared by an impregnation method, the nf-MnO(x)@CNTs presented better NH?-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn(4+) and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnO(x)@CNTs. The H?-TPR and NH?-TPD results demonstrated that the nf-MnO(x)@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnO(x)@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N? with NH?. In addition, the nf-MnO(x)@CNT catalyst also presented favourable stability and H?O resistance. PMID:23928911

  14. [Sorption-desorption of phosphate in wastewater by hydrous iron oxide].

    PubMed

    Xiang, Xue-Min; Liu, Ying; Zhou, Ji-Ti; Wang, Ren

    2008-11-01

    FeCl3 was used t o prepare hydrous iron oxide (HIO) as a n absorbent for phosphate (P) sorption and desorption study. The results showed that as pH decreased, the sorption capacity of HIO increased, and the sorption kinetics followed the second-order model, and the sorption isotherm could be fitted by the Langmuir equation. A 50 g/L NaOH solution was used for desorption of P from HIO, and the desorption rate could be reached over 98% . No relation was found between desorption rate and adsorption capacity. Based on above results, HIO was applied to adsorption of P from supernatant of sludge thickener, and after desorption, more than 90% of P was recovered. According to the results obtained, an effective system for P removal and recovery from municipal wastewater was suggested, which includes the following processes: adsorption, desorption, regeneration of HIO, and of recovery of P from P-rich desorption solution. PMID:19186802

  15. Desorption of polycyclic aromatic hydrocarbons from field-contaminated soil to a two-dimensional hydrophobic surface before and after bioremediation

    PubMed Central

    Hu, Jing; Aitken, Michael D.

    2012-01-01

    Dermal exposure can represent a significant health risk in settings involving potential contact with soil contaminated with polycyclic aromatic hydrocarbons (PAHs). However, there is limited work on the ability of PAHs in contaminated soil to reach the skin surface via desorption from the soil. We evaluated PAH desorption from a field-contaminated soil to a two-dimensional hydrophobic surface (C18 extraction disk) as a measure of potential dermal exposure as a function of soil loading (5 to 100 mg dry soil/cm2), temperature (20 °C to 40 °C), and soil moisture content (2% to 40%) over periods up to 16 d. The efficacy of bioremediation in removing the most readily desorbable PAH fractions was also evaluated. Desorption kinetics were described well by an empirical two-compartment kinetic model. PAH mass desorbed to the C18 disk kept increasing at soil loadings well above the estimated monolayer coverage, suggesting mechanisms for PAH transport to the surface other than by direct contact. Such mechanisms were reinforced by observations that desorption occurred even with dry or moist glass microfiber filters placed between the C18 disk and the soil. Desorption of all PAHs was substantially reduced at a soil moisture content corresponding to field capacity, suggesting that transport through pore air contributed to PAH transport to the C18 disk. The lower molecular weight PAHs had greater potential to desorb from soil than higher molecular weight PAHs. Biological treatment of the soil in a slurry-phase bioreactor completely eliminated PAH desorption to the C18 disks. PMID:22704210

  16. Improving low temperature properties of synthetic diesel fuels derived from oil shale. Alternative fuels utilization program

    SciTech Connect

    Frankenfeld, J.W.; Taylor, W.F.

    1980-11-01

    The ability of additives to improve the cold flow properties of shale oil derived fuels boiling in the diesel fuel range was evaluated. Because a commercial shale oil industry did not exist to provide actual samples of finished fuels, a representative range of hydroprocessed shale oil fractions was prepared for use in the additive testing work. Crude oil shale from Occidental Shale Company was fractionated to give three liquids in the diesel fuel boiling range. The initial boiling point in each case was 325/sup 0/F (163/sup 0/C). The final boiling points were 640/sup 0/F (338/sup 0/C), 670/sup 0/F (354/sup 0/C) and 700/sup 0/F (371/sup 0/F). Each fraction was hydrotreated to three different severities (800, 1200 and 1500 psi total pressure) over a Shell 324 nickel molybdate on alumina catalyst at 710 to 750/sup 0/F to afford 9 different model fuels. A variety of commercial and experimental additives were evaluated as cold flow improvers in the model fuels at treat levels of 0.04 to 0.4 wt %. Both the standard pour point test (ASTM D97) and a more severe low temperature flow test (LTFT) were employed. Reductions in pour points of up to 70/sup 0/F and improvements in LTFT temperatures up to 16/sup 0/F were achieved. It is concluded that flow improver additives can play an important role in improving the cold flow properties of future synthetic fuels of the diesel type derived from oil shale.

  17. Reaction of oxygen-nitrogen mixtures with granular activated carbons below the spontaneous ignition temperature

    SciTech Connect

    Not Available

    1984-08-01

    The presence of oxygen in the carbon network of gas-adsorbent charcoals presents a research problem of long standing. Four pertinent topics now concerned with the oxygen-charcoal reactions are: a) activation of the adsorbent charcoals (manufacture), b) regeneration processes (applications), c) the spontaneous ignition temperature (safety considerations), and d) the use of charcoals as catalyst carriers and impregnation supports. It is desirable to have a deeper knowledge of the initial surface composition of a charcoal that is to be used in a specific process. Thermal desorption behavior can supply such information. The results to be reported cover three characteristic temperature-dependent phenomena: 1) an anomalous desorption in which a number of maxima occur in the concentrations of CO and CO/sub 2/; 2) the formation of a surface barrier causing a decay in the CO and CO/sub 2/ concentrations with the first-order rate constants at constant temperature; and 3) the attainment of a reproducible spontaneous ignition temperature (SIT) during programmed heating at a linear rate. These observations indicate a considerable complexity in the surface structure of an activated carbon.

  18. Adsorption-desorption and leaching behavior of kresoxim-methyl in different soils of India: kinetics and thermodynamic studies.

    PubMed

    Sabale, Rupali P; Shabeer T P, Ahammed; Dasgupta, Soma; Utture, Sagar C; Banerjee, Kaushik; Oulkar, Dasharath P; Adsule, Pandurang G; Deshmukh, Madhukar B

    2015-07-01

    The sorption and leaching behavior of kresoxim-methyl was explored in four different soils, viz., clay, sandy loam, loamy sand, and sandy loam (saline), representing vegetables and fruits growing regions of India. Adsorption of kresoxim-methyl in all the soils reached equilibrium within 48 h. The rate constants for adsorption and desorption at two different temperatures were obtained from the Lindstrom model, which simultaneously evaluated adsorption and desorption kinetics. The data for rate constants, activation energies, enthalpy of activation, entropy of activation, and free energy indicated physical adsorption of kresoxim-methyl on soil. The relative adsorptivity of the test soils could be attributed to different organic matter and clay contents of the soils. A good fit to the linear and Freundlich isotherms was observed for both adsorption as well as desorption. The groundwater ubiquity score (GUS) for different soils varied between 0 and 2.26. The GUS and leaching study indicated moderately low leaching potential of kresoxim-methyl. The adsorption on four soil types largely depended on the soil physicochemical properties such as organic carbon content, cation-exchange capacity, and texture of the soil. PMID:26082423

  19. Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran formation and emission in the thermal desorption waste treatment process

    SciTech Connect

    Leckey, J.H.

    1995-03-01

    It is extremely unlikely that significant amounts of polychlorinated dibenzo-p-dioxins (PCDDs) or polychlorinated dibenzofurans (PCDFs) will be emitted in the off-gas stream from the thermal desorption process, or the treated waste, particularly if the baseline design and anticipated operating conditions of the enhanced bench-scale (EBS) system are used. However, because of the acute toxicity of these compounds and because most of the data on their formation have been extrapolated from studies more related to incineration and fire conditions than thermal desorption, specific laboratory tests and specific EBS runs should be performed to monitor the rate of emission of PCDDs and PCDFs under thermal desorption conditions. In general, the following four conditions need to exist for significant amounts of PCDD or PCDF to be formed: (1) the presence of fly ash; (2) the presence of an oxidizing source; (3) a suitable temperature, and (4) the presence of a suitable precursor. Although the EBS system provides some of these conditions, it is unlikely that enough fly ash will be produced in the system to allow a significant amount of PCDD or PCDF formation. Additionally, particulate matter controls will be used to remove airborne particulates from the gas phase. If PCDD/Fs are presented in a waste stream being evaluated in the EBS, they will likely volatilize in the kiln and subsequently condense in the venturi scrubber system.

  20. Development of Designer Diamond Technology for High Pressure High Temperature Experiments in Support of Stockpile Stewardship Program

    SciTech Connect

    Vohra, Yogesh, K.

    2009-10-28

    The role of nitrogen in the fabrication of designer diamond was systematically investigated by adding controlled amount of nitrogen in hydrogen/methane/oxygen plasma. This has led to a successful recipe for reproducible fabrication of designer diamond anvils for high-pressure high-temperature research in support of stockpile stewardship program. In the three-year support period, several designer diamonds fabricated with this new growth chemistry were utilized in high-pressure experiments at UAB and Lawrence Livermore National Laboratory. The designer diamond anvils were utilized in high-pressure studies on heavy rare earth metals, high pressure melting studies on metals, and electrical resistance measurements on iron-based layered superconductors under high pressures. The growth chemistry developed under NNSA support can be adapted for commercial production of designer diamonds.

  1. Catalytic membrane program novation: High temperature catalytic membrane reactors. Final report

    SciTech Connect

    Kleiner, R.N. [Kleiner (Richard N.), Englewood, CO (United States)] [Kleiner (Richard N.), Englewood, CO (United States)

    1998-08-28

    The original objective was to develop an energy-efficient hydrocarbon dehydrogenation process based on catalytic membrane reactors. Golden Technologies determined that the goals of this contract would be best served by novating the contract to an end user or other interested party which is better informed on the economic justification aspects of petrochemical refining processes to carry out the remaining work. In light of the Chevron results, the program objective was broadened to include development of inorganic membranes for applications in the chemical industry. The proposed membrane technologies shall offer the potential to improve chemical production processes via conversion increase and energy savings. The objective of this subcontract is to seek a party that would serve as a prime contractor to carry out the remaining tasks on the agreement and bring the agreement to a successful conclusion. Four tasks were defined to select the prime contractor. They were (1) prepare a request for proposal, (2) solicit companies as potential prime contractors as well as team members, (3) discuss modifications requested by the potential prime contractors, and (4) obtain, review and rank the proposals. The accomplishments on the tasks is described in detail in the following sections.

  2. Multiple sample characterization of coals and other substances by controlled-atmosphere programmed temperature oxidation

    DOEpatents

    LaCount, Robert B. (403 Arbor Ct., Waynesburg, PA 15370)

    1993-01-01

    A furnace with two hot zones holds multiple analysis tubes. Each tube has a separable sample-packing section positioned in the first hot zone and a catalyst-packing section positioned in the second hot zone. A mass flow controller is connected to an inlet of each sample tube, and gas is supplied to the mass flow controller. Oxygen is supplied through a mass flow controller to each tube to either or both of an inlet of the first tube and an intermediate portion between the tube sections to intermingle with and oxidize the entrained gases evolved from the sample. Oxidation of those gases is completed in the catalyst in each second tube section. A thermocouple within a sample reduces furnace temperature when an exothermic condition is sensed within the sample. Oxidized gases flow from outlets of the tubes to individual gas cells. The cells are sequentially aligned with an infrared detector, which senses the composition and quantities of the gas components. Each elongated cell is tapered inward toward the center from cell windows at the ends. Volume is reduced from a conventional cell, while permitting maximum interaction of gas with the light beam. Reduced volume and angulation of the cell inlets provide rapid purgings of the cell, providing shorter cycles between detections. For coal and other high molecular weight samples, from 50% to 100% oxygen is introduced to the tubes.

  3. From Laser Desorption to Laser Ablation of Biopolymers

    NASA Astrophysics Data System (ADS)

    Franz, Hillenkamp

    1998-03-01

    For selected indications laser ablation and cutting of biological tissues is clinical practice. Preferentially lasers with emission wavelengths in the far UV and the mid IR are used, for which tissue absorption is very high. Morphologically the ablation sites look surprisingly similar for the two wavelength ranges, despite of the very different prim y putative interaction mechanisms. Ablation depth as a function of fluence follows a sigmoidal curve. Even factors below the nominal ablation threshold superficial layers of material get removed from the surface. This is the fluence range for Matrix-Assisted Laser Desorption/Ionization (MALDI). Evidence will be presented which suggest that strong similarities exist between the desorption and ablation processes both for UV- as well as for IR-wavelengths.

  4. System operation: Continuous volatile organic compound air monitoring of 56 ozone precursors with the Perkin-Elmer 8700 GC and automatic thermal desorption system

    SciTech Connect

    Radenheimer, P. [Consolidated Sciences Corp., Pasadena, TX (United States); Gibich, J. [Texas Natural Resource Conservation Commission, Austin, TX (United States); Ogle, L. [Radian Corp., Austin, TX (United States)

    1994-12-31

    As part of the Coastal Oxidant Assessment for Southeast Texas (COAST) program, two sites were chosen by the Texas Natural Resource Conservation Commission (TRNCC) and equipped with a Perkin-Elmer VOC system composed of the 8700 Gas Chromatograph, ATD-400 Automatic Thermal Desorption and Turbochrom III Data system on DEC computers. The systems were equipped with a dual capillary column application capable of resolving 56 distinct target ozone precursors. These components were separated and quantified on an hourly basis 24 hours each day. Each system generated 96 data files and approximately 30 documentation files each day totaling nearly 3 megabytes of information. The system was fully automated and monitored rigorously via high-speed modem communication. The modem communication proved to be essential in the handling of the large volume of data generated each day. A fully automated data transfer system was developed to allow unattended file archiving thus eliminating many problems associated with manual handling of files and facilitating the rapid evaluation of the data. This paper will identify the major issues in operation and maintenance of these systems (not including the chromatographic application). Problems which were encountered can be subdivided into 2 categories, (a) hardware system problems such as power failures, equipment malfunction and temperature/humidity fluctuations, and (b) software issues: capability/incompatibility, bugs, communication problems and a plethora of computer or computer-related issues (confusion).

  5. Increasing ion sorption and desorption rates of conductive electrodes

    DOEpatents

    DePaoli, David William; Kiggans, Jr., James O; Tsouris, Costas; Bourcier, William; Campbell, Robert; Mayes, Richard T

    2014-12-30

    An electrolyte system includes a reactor having a pair of electrodes that may sorb ions from an electrolyte. The electrolyte system also includes at least one power supply in electrical communication with the reactor. The at least one power supply may supply a DC signal and an AC signal to the pair of electrodes during sorption of the ions. In addition, the power supply may supply only the AC signal to the pair of electrodes during desorption of the ions.

  6. Adsorption and desorption of glyphosate in some European soils

    Microsoft Academic Search

    A. Piccolo; G. Celano; M. Arienzo; A. Mirabella

    1994-01-01

    The interaction of glyphosate [N?(phosphonomethyl)?glycine] with four typical European soils is reported. Results of adsorption and desorption isotherms show that the interaction of glyphosate with these soils was mainly related to content of iron and aluminium amorphus hydroxides. Moreover, it was found that the presence of divalent cations in 2: 1 clay minerals also contribute to glyphosate adsorption. The S?type

  7. Adsorption-desorption and leaching of phenylurea herbicides on soils

    Microsoft Academic Search

    Christine M. Fouqué-Brouard; Josette M. Fournier

    1996-01-01

    Adsorption-desorption equilibria of phenylurea herbicides (chlortoluron, isoproturon, metobromuron, chloroxuron, difenoxuron) were determined in two different soils. Organic carbon content of the soils ranged from 1.1–5.6% and the clay fraction from 25–30%. Spiked aqueous suspensions of soils were centrifuged and urea derivative concentrations in the aqueous phase were determined using a HPLC-UV system. Adsorption isotherms conformed to the Freundlich equation. Freundlich

  8. 252Cf Plasma Desorption Mass Spectrometry: Recent Advances and Applications

    Microsoft Academic Search

    I. Kamensky; A. G. Craig

    1987-01-01

    Cf plasma desorption mass spectrometry (PDMS) as utilized in the BIO-ION instruments is described. The sensitivity of the technique is investigated for varying amounts of bovine insulin. The results show accurate mass assignment for pmole amounts of sample.Several methods, currently used for sample preparation in PDMS, are described. Spectra of the antibiotic nisin (3,354.1 Dalton) using two different sample preparation

  9. UV-Illumination Induced Desorption of CNT Sensors

    Microsoft Academic Search

    Li Yang; Mengxing Ouyang; Wen J. Li; Xuliang Han

    2008-01-01

    This paper presents a chemical sensor employing electronic-grade CNTs (EG-CNTs) as the active sensing element for sodium hypochlorite (NaOCl) detection and the-desorption phenomenon of the sensing element by applying UV illumination. By using AC dielectrophoretic (DEP) technique, EG-CNTs are aligned between the microelectrodes fabricated on a glass substrate with a gap distance of 2 mum. A microfluidic chamber is created

  10. Fluridone adsorption–desorption on organo-clays

    Microsoft Academic Search

    Dana Yaron-Marcovich; Shlomo Nir; Yona Chen

    2004-01-01

    The adsorption–desorption of the herbicide fluridone on Na-montmorillonite and several organo-montmorillonite complexes was studied at a variety of loadings of the organic cation and pH levels. The aim was to find the organo-clay complex, which would be an optimal adsorbent for the hydrophobic fluridone. The organic cations studied were hexadecyltrimethylammonium (HDTMA), benzyltriethylammonium (BTEA), benzyltrimethylammonium (BTMA) and methylene blue (MB) at

  11. Thermal desorption of oxides on InP

    Microsoft Academic Search

    Wo M. Lau; R. N. S. Sodhi; S. Ingrey

    1988-01-01

    The thermal desorption of thin oxide films on n- and p-type InP has been studied by using x-ray photoelectron spectroscopy. It was found that oxides formed on InP could be completely desorbed at 458 °C without causing surface decomposition. The phosphorus and indium oxides desorbed together within 5°. However, heating the oxidized surface to about 453 °C, while not changing

  12. Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Laskin, Julia; Heath, Brandi S.; Roach, Patrick J.; Cazares, Lisa H.; Semmes, O. John

    2012-01-03

    We present the first results showing the ambient imaging of biological samples in their native environment using nanospray desorption ionization (nanoDESI) mass spectrometry. NanoDESI is an ambient pressure ionization technique that enables precise control of ionization of molecules from substrates. We demonstrate highly sensitive and robust analysis of tissue samples with high spatial resolution (<12 {mu}m) without sample preparation, which will be essential for applications in clinical diagnostics, drug discovery, molecular biology, and biochemistry.

  13. Nonideal Sorption-Desorption and Extensive Elution Tailing

    NASA Astrophysics Data System (ADS)

    Russo, A. E.; Akyol, N. H.; Schnaar, G. A.; Johnson, G. R.; Yolcubal, I.; Brusseau, M. L.

    2011-12-01

    Contamination of subsurface environments by organic compounds continues to pose a risk to the environment. Sorption is a critical process that influences the transport and fate of organic contaminants. Contaminant mobility, bioavailability, and the effectiveness of remediation efforts are mediated in part by sorption/desorption processes. Miscible-displacement experiments were conducted to characterize long-term, low-concentration elution tailing associated with sorption/desorption processes. A variety of soils and aquifer sediments, representing a range of particle-size distributions and organic-carbon contents, were employed, and trichloroethene (TCE) was used as the model organic compound. Trichloroethene transport exhibited extensive elution tailing for all media, with several hundred to several thousand pore volumes of water flushing required to reach the detection limit (~0.1 ?g/L). The elution tailing was more extensive for the media with higher organic-carbon contents and associated retardation factors. However, when normalized by retardation, the extent of tailing did not correlate directly to organic-carbon content. These latter results suggest that differences in the geochemical nature of organic carbon (e.g., composition, structure) among the various media influenced observed behavior. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous-distribution function was used to successfully simulate trichloroethene transport, including the extensive elution tailing.

  14. Production of negative osmium ions by laser desorption and ionization.

    PubMed

    Rodríguez, D; Sonnenschein, V; Blaum, K; Block, M; Kluge, H-J; Lallena, A M; Raeder, S; Wendt, K

    2010-01-01

    The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs(+) ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionization with pulsed lasers and identification of the ions by time-of-flight mass spectrometry. First investigations of negative osmium ion production using a pulsed laser for desorption and ionization and a commercial matrix-assisted laser desorption/ionization time-of-flight system for identification has demonstrated the suitability of this technique. More than 10(3) negative osmium ions per shot were registered after bombarding pure osmium powder with a 5 ns pulse width Nd:yttrium aluminum garnet laser. The limitation in the ion number was imposed by the detection limit of the microchannel plate detector. PMID:20113087

  15. The desorptivity model of bulk soil-water evaporation

    NASA Technical Reports Server (NTRS)

    Clapp, R. B.

    1983-01-01

    Available models of bulk evaporation from a bare-surfaced soil are difficult to apply to field conditions where evaporation is complicated by two main factors: rate-limiting climatic conditions and redistribution of soil moisture following infiltration. Both factors are included in the "desorptivity model', wherein the evaporation rate during the second stage (the soil-limiting stage) of evaporation is related to the desorptivity parameter, A. Analytical approximations for A are presented. The approximations are independent of the surface soil moisture. However, calculations using the approximations indicate that both soil texture and soil moisture content at depth significantly affect A. Because the moisture content at depth decreases in time during redistribution, it follows that the A parameter also changes with time. Consequently, a method to calculate a representative value of A was developed. When applied to field data, the desorptivity model estimated cumulative evaporation well. The model is easy to calculate, but its usefulness is limited because it requires an independent estimate of the time of transition between the first and second stages of evaporation. The model shows that bulk evaporation after the transition to the second stage is largely independent of climatic conditions.

  16. Production of negative osmium ions by laser desorption and ionization

    NASA Astrophysics Data System (ADS)

    Rodríguez, D.; Sonnenschein, V.; Blaum, K.; Block, M.; Kluge, H.-J.; Lallena, A. M.; Raeder, S.; Wendt, K.

    2010-01-01

    The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs+ ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionization with pulsed lasers and identification of the ions by time-of-flight mass spectrometry. First investigations of negative osmium ion production using a pulsed laser for desorption and ionization and a commercial matrix-assisted laser desorption/ionization time-of-flight system for identification has demonstrated the suitability of this technique. More than 103 negative osmium ions per shot were registered after bombarding pure osmium powder with a 5 ns pulse width Nd:yttrium aluminum garnet laser. The limitation in the ion number was imposed by the detection limit of the microchannel plate detector.

  17. Adsorption and Desorption of Nitrogen and Water Vapor by clay

    NASA Astrophysics Data System (ADS)

    Cui, Deshan; Chen, Qiong; Xiang, Wei; Huang, Wei

    2015-04-01

    Adsorption and desorption of nitrogen and water vapor by clay has a significant impact on unsaturated soil physical and mechanical properties. In order to study the adsorption and desorption characteristics of nitrogen and water vapor by montmorillonite, kaolin and sliding zone soils, the Autosorb-iQ specific surface area and pore size analyzer instrument of United State was taken to carry out the analysis test. The adsorption and desorption of nitrogen at 77K and water vapor at 293K on clay sample were conducted. The theories of BET, FHH and hydration energy were taken to calculate the specific surface, surface fractal dimension and adsorption energy. The results show that the calculated specific surface of water vapor by clay is bigger than nitrogen adsorption test because clay can adsorb more water vapor molecule than nitrogen. Smaller and polar water vapor molecule can access the micropore and then adsorb on the mineral surface and mineral intralayer, which make the mineral surface cations hydrate and the mineral surface smoother. Bigger and nonpolar nitrogen molecule can not enter into the micropore as water vapor molecule and has weak interaction with clay surface.

  18. Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications

    NASA Astrophysics Data System (ADS)

    Taira, Shu; Kitajima, Kenji; Katayanagi, Hikaru; Ichiishi, Eiichiro; Ichiyanagi, Yuko

    2009-06-01

    We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm) and developed nanoparticle-assited laser desorption/ionization (nano-PALDI) mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m/z. The nanoparticles could ionize samples of peptide, drug and proteins (approx. 5000 Da) without using matrix, i.e., 2,5-dihydroxybenzoic acid (DHB), 4-hydroxy-?-cinnamic acid (CHCA) and liquid matrix, as conventional ionization assisting reagents. Post source decay spectra by nano-PALDI mass spectrometry will yield information of the chemical structure of analytes.

  19. N-acetylglucosamine (GlcNAc) Triggers a Rapid, Temperature-Responsive Morphogenetic Program in Thermally Dimorphic Fungi

    PubMed Central

    Gilmore, Sarah A.; Naseem, Shamoon; Konopka, James B.; Sil, Anita

    2013-01-01

    The monosaccharide N-acetylglucosamine (GlcNAc) is a major component of microbial cell walls and is ubiquitous in the environment. GlcNAc stimulates developmental pathways in the fungal pathogen Candida albicans, which is a commensal organism that colonizes the mammalian gut and causes disease in the setting of host immunodeficiency. Here we investigate GlcNAc signaling in thermally dimorphic human fungal pathogens, a group of fungi that are highly evolutionarily diverged from C. albicans and cause disease even in healthy individuals. These soil organisms grow as polarized, multicellular hyphal filaments that transition into a unicellular, pathogenic yeast form when inhaled by a human host. Temperature is the primary environmental cue that promotes reversible cellular differentiation into either yeast or filaments; however, a shift to a lower temperature in vitro induces filamentous growth in an inefficient and asynchronous manner. We found GlcNAc to be a potent and specific inducer of the yeast-to-filament transition in two thermally dimorphic fungi, Histoplasma capsulatum and Blastomyces dermatitidis. In addition to increasing the rate of filamentous growth, micromolar concentrations of GlcNAc induced a robust morphological transition of H. capsulatum after temperature shift that was independent of GlcNAc catabolism, indicating that fungal cells sense GlcNAc to promote filamentation. Whole-genome expression profiling to identify candidate genes involved in establishing the filamentous growth program uncovered two genes encoding GlcNAc transporters, NGT1 and NGT2, that were necessary for H. capsulatum cells to robustly filament in response to GlcNAc. Unexpectedly, NGT1 and NGT2 were important for efficient H. capsulatum yeast-to-filament conversion in standard glucose medium, suggesting that Ngt1 and Ngt2 monitor endogenous levels of GlcNAc to control multicellular filamentous growth in response to temperature. Overall, our work indicates that GlcNAc functions as a highly conserved cue of morphogenesis in fungi, which further enhances the significance of this ubiquitous sugar in cellular signaling in eukaryotes. PMID:24068964

  20. Determination of volatile organic compounds in different microenvironments by multibed adsorption and short-path thermal desorption followed by gas chromatographic-mass spectrometric analysis.

    PubMed

    Kuntasal, Oznur O?uz; Karman, Deniz; Wang, Daniel; Tuncel, Semra G; Tuncel, Gürdal

    2005-12-16

    A multiphase assurance approach was developed for the accurate and precise determination of volatile organic compounds (VOCs) in different microenvironments. This approach includes (i) development of a method including adsorption of VOCs onto a multisorbent media followed by short-path thermal desorption (SPTD) pre-concentration and gas chromatography (GC) coupled to a mass spectrometry (MS) quantification, (ii) validation of the sampling and analytical method and (iii) validation of the data using a multidimensional procedure. Tenax TA and Carbopack B sorbent combinations were used to collect 102 individual VOCs ranging from C5 to C12. Method parameters including thermal desorption temperature, desorption time and cryofocusing temperature were optimized. The average recoveries and method detection limits (MDL) for the target analytes were in the range 80-100% and 0.01-0.14 ppbv, respectively. The method also showed good linearity (R2 > 0.99) and precision (<8%) values. Validation of the method was performed under real environmental conditions at a gas station, in an office and a residential household to examine the influence of variation in meteorological conditions such as temperature and relative humidity and a wide range of VOC concentrations. The sampling and analytical method resulted in successful determination of VOC in different microenvironments. Finally, validation of the data was performed by assessing fingerprint and time series plots and correlation matrices together with meteorological parameters such as mixing height, wind speed and temperature. The data validation procedure provided detection of both faulty data and air pollution episodes. PMID:16330271

  1. High-Temperature-Turbine Technology Program: Phase II. Technology test and support studies. Design and development of the liquid-fueled high-temperature combustor for the Turbine Spool Technology Rig

    SciTech Connect

    None

    1981-06-01

    The concept selected by Curtiss-Wright for this DOE sponsored High Temperature Turbine Technology (HTTT) Program utilizes transpiration air-cooling of the turbine subsystem airfoils. With moderate quantities of cooling air, this method of cooling has been demonstrated to be effective in a 2600 to 3000/sup 0/F gas stream. Test results show that transpiration air-cooling also protects turbine components from the aggressive environment produced by the combustion of coal-derived fuels. A new single-stage, high work transpiration air-cooled turbine has been designed and fabricated for evaluation in a rotating test vehicle designated the Turbine Spool Technology Rig (TSTR). The design and development of the annular combustor for the TSTR are described. Some pertinent design characteristics of the combustor are: fuel, Jet A; inlet temperature, 525/sup 0/F; inlet pressure, 7.5 Atm; temperature rise, 2475/sup 0/F; efficiency, 98.5%; exit temperature pattern, 0.25; and exit mass flow, 92.7 pps. The development program was conducted on a 60/sup 0/ sector of the full-round annular combustor. Most design goals were achieved, with the exception of the peak gas exit temperature and local metal temperatures at the rear of the inner liner, both of which were higher than the design values. Subsequent turbine vane cascade testing established the need to reduce both the peak gas temperature (for optimum vane cooling) and the inner liner metal temperature (for combustor durability). Further development of the 60/sup 0/ combustor sector achieved the required temperature reductions and the final configuration was incorporated in the TSTR full-annular burner.

  2. A temperature-programmed reaction method for catalyst testing in the partial oxidation of methane to formaldehyde

    SciTech Connect

    Not Available

    1993-09-01

    During the last years a large variety of unpromoted and promoted oxide catalysts has been claimed to be effective in the partial oxidation of methane (MPO) to formaldehyde. This reaction proceeds via a very complex network and requires medium-high temperatures (550 < T[sub R] < 650[degrees]C) to attain detectable rates. The unique features of the SiO[sub 2] surface in catalysing the formation of partial oxidation products have been largely documented, while the roles played by MoO[sub 3], V[sub 2]O[sub 5], Nb[sub 2]O[sub 5], WO[sub 3], Cr[sub 2]O[sub 3], and other oxides on the reactivity of the SiO[sub 2] and the nature of the active centers are still topics of debate. A number of papers have particularly addressed the importance of the reaction system and the contribution of the gas phase and/or wall reaction in getting valid and comparable reactivity data. Indeed, given the constraints of the conversion-selectivity relationship, a suitable reactor device must exploit a differential methane conversion level per pass as to ensure high selectivity to HCHO providing also finite conversion values for a reliable kinetic analysis of the data. In this note, the authors present the potentiality of the temperature-programmed reaction (TPR) method in evaluating the activity of the MPO catalysts. A preliminary comparative analysis of the catalytic performances of bare SiO[sub 2] and various silica supported oxide (MoO[sub 3], V[sub 2]O[sub 5], Nb[sub 2]O[sub 5]) catalysts is reported.

  3. Determination of the carbon isotopic composition of whole\\/intact biological specimens using at-line direct thermal desorption to effect thermally assisted hydrolysis\\/methylation

    Microsoft Academic Search

    Lawrence Akoto; René J. J. Vreuls; Hubertus Irth; Virgilio Floris; Hans Hoogveld; Roel Pel

    2008-01-01

    In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography–combustion isotope-ratio mass spectrometry (GC\\/C-IRMS) analysis of whole\\/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped

  4. Laboratory studies of desorption from model interstellar ices using surface science methodologies

    NASA Astrophysics Data System (ADS)

    Collings, M. P.; McCoustra, M. R. S.

    2012-02-01

    Desorption of condensed species is a key process in controlling the balance of material between the solid and gaseous phases in the interstellar medium. Therefore, a quantitative understanding of desorption in astrophysical environments, by both thermal and non-thermal mechanisms, is essential for development of the field of astrochemistry. This paper briefly reviews recent progress in the study of desorption by experimental and computational methods, and identifies some areas with potential for development in the near future.

  5. Site and Interaction Dependence of Nuclear Stimulated Desorption from Structured Surfaces

    NASA Astrophysics Data System (ADS)

    Ashkenazy, Y.; Kelson, I.

    Molecular dynamics calculations of low energy Nuclear Stimulated Desorption (NSD) of 107Cd from a palladium substrate are presented. The characteristics of the desorption probability are shown to be related both to the site occupied by the 107Cd and to the adsorbate-substrate interaction. The quantitative implications of the theoretical calculations to a specific experimental scenario are discussed, based on preliminary measurements of 107Cd desorption from palladium.

  6. Ambient desorption ionization mass spectrometry (DART, DESI) and its bioanalytical applications

    Microsoft Academic Search

    Elena S. Chernetsova; Gertrud E. Morlock

    2011-01-01

    In recent years, ambient desorption ionization techniques for mass spectrometry were introduced. Among them, the most established\\u000a techniques are Direct Analysis in Real Time (DART) and Desorption Electrospray Ionization (DESI). Therefore, the current review\\u000a focuses on the bioanalytical applications of ambient desorption ionization techniques by the example of DART and DESI mass\\u000a spectrometry. The potential and also limitations of both

  7. Combined temperature-programmed reaction and in situ x-ray scattering studies of size-selected silver clusters under realistic reaction conditions in the epoxidation of propene

    NASA Astrophysics Data System (ADS)

    Vajda, Stefan; Lee, Sungsik; Sell, Kristian; Barke, Ingo; Kleibert, Armin; von Oeynhausen, Viola; Meiwes-Broer, Karl-Heinz; Rodríguez, Arantxa Fraile; Elam, Jeffrey W.; Pellin, Michael M.; Lee, Byeongdu; Seifert, Sönke; Winans, Randall E.

    2009-09-01

    The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions for the first time. The approach is illustrated in a chemical industry highly relevant selective partial oxidation of propene on a monodisperse silver nanocatalyst. The shape of the catalyst undergoes rapid change already at room temperature upon the exposure to the reactants, followed by a complex evolution of shape with increasing temperature. Acrolein formation is observed around 50 °C while the formation of the propylene oxide exhibits a sharp onset at 80 °C and is leveling off at 150 °C. At lower temperatures acrolein is produced preferentially to propylene oxide; at temperatures above 100 °C propylene oxide is favored.

  8. Effective desorption of tritium from diverse solid matrices and its application to routine analysis of decommissioning materials.

    PubMed

    Warwick, P E; Kim, D; Croudace, I W; Oh, J

    2010-08-31

    Tritium extraction from materials is most commonly carried out using oxidative thermal desorption in purpose-built furnace systems and typically involves trapping the product in a water bubbler which is sampled for measurement using liquid scintillation counting (LSC). The performance of perhaps the most widely used commercial system, the Raddec Pyrolyser, has been evaluated for a broad range of sample types. Several parameters that were expected to affect tritium desorption and recovery were systematically studied. These included sample heating rates and end-point temperatures, carrier/oxidant gas flows, catalyst temperature, bubbler trapping and carry-over/memory effects. A catalyst such as platinised-alumina is used to ensure the quantitative oxidation of volatile combustion products to HTO and CO(2). This also ensures that the trapped decomposition products do not colourise the bubbler solutions that are subsequently sampled for LSC. Tritium evolution profiles were determined for a range of sample types and were obtained by systematically changing bubblers at a set of progressively increasing temperatures. These experiments showed the maximum heating temperature and total combustion time required for the complete recovery of tritium from samples was dependent on the sample matrix types and the (3)H form. These evolution profiles need only be determined once and are readily transferable to other Pyrolyser systems. For example tritiated water is rapidly liberated from samples at temperature around 100 degrees C whereas (3)H substituted for structural H in organic species can require a temperature in excess of 300 degrees C to be released. Higher temperatures (up to 900 degrees C) are needed to liberate (3)H originating from neutron capture reactions on trace Li or B within a material (e.g. reactor graphite or concrete). The furnace system investigated is highly effective at extracting tritium and (14)C from all sample types studied (soil, sediment, biota, wood, metal, plastic, concrete, graphite, etc.) and overall it demonstrates high and reproducible recoveries. PMID:20800748

  9. The use of temperature-programmed and dynamic\\/transient methods in catalysis: characterization of ceria-based, model three-way catalysts

    Microsoft Academic Search

    Marta Boaro; Michela Vicario; Carla de Leitenburg; Giuliano Dolcetti; Alessandro Trovarelli

    2003-01-01

    Temperature-programmed (TP) methods have been increasingly used in recent years for the characterization of catalytic materials under conditions similar to those encountered in commercial applications. A large variety of complementary TP techniques can be used with minimum variation of experimental conditions, thus allowing great characterization potential in a single apparatus. Modern analytical and numerical tools allow accurate analysis and modeling

  10. Performance of programmed temperature vaporizer, pulsed splitless and on-column injection techniques in analysis of pesticide residues in plant matrices

    Microsoft Academic Search

    Jitka Zrostl??ková; Jana Hajšlová; Michal Godula; Kate?ina Maštovská

    2001-01-01

    A programmed temperature vaporizer (PTV) injection technique has been recently implemented in our laboratory. In present paper its performance is compared with other GC injection techniques commonly used in trace analysis of organic contaminants. Twenty-six pesticides representing different chemical classes were selected for the study. This group comprised compounds typically subjected to discrimination in the injection port of the gas

  11. Evaluation of Water Repellency in Petroleum Drilling Cuttings Treated by Thermal Desorption: Implications for Use in Construction and Agriculture

    NASA Astrophysics Data System (ADS)

    Domínguez-Rodríguez, Verónica I.; Guzmán-Osorio, Francisco J.; Adams Schroeder, Randy H.; Bautista-Margulis, Raúl G.

    2010-05-01

    Thermal desorption is one of many methods used for the remediation of hydrocarbon contaminated soils and similar materials. It has several advantages over competing technologies, especially with respect to treatment times. While the biological treatment of contaminated soils may take several months depending principally on the type of hydrocarbons and starting concentration, thermal desorption typically takes less than one month, depending on the treatment capacities of the equipment involved, and the volume of material requiring treatment. In the petroleum producing region of southeastern Mexico, this has been one of the principal methods used for the treatment of drilling cuttings, due mostly to the short time required. As with most remediation projects, as well as in the treatment of exploration and production (E&P) wastes, the criteria used to consider the remediation finalized is the concentration of hydrocarbons in the treated material. This is based on the supposition that at some (relatively low) hydrocarbon concentration, the toxicological affects are reduced to acceptable levels. However, little attention has been paid to the physical-chemical properties of supposedly treated material, which may suffer from water repellency, especially in thermal treatment methods. This could greatly reduce the options for final use of treated materials, especially to support plant growth. Conversely, there may be some construction uses of treated material in which some water repellence could be beneficial (caps for land fills, for example). Considering the relevance of the physical-chemical impacts of petroleum on soil and similar materials, we felt it was important to evaluate the efficiency of the principal method used to treat E&P wastes in Mexico (thermal desporption) based on these factors. In this study different operating conditions (temperature and residence time) of a sub-pilot scale thermal desorption unit were evaluated with respect not only to reduction in hydrocarbon concentration, but also based on water repellency. To our knowledge this is the first study of this type. Water repellency severity was measured in petroleum drilling cuttings which had been treated by thermal desorption to reduce the concentration of total petroleum hydrocarbons (TPHs). The initial TPH concentration in the untreated material was 16850mg/Kg (dry). The prototype batch rotary oven used in this study was operated at 25 rpm, at three temperatures and three treatment times: at 150, 200, and 300°C, for 10, 15, and 20 minutes. Four of the nine treatments complied with the Mexican environmental norm (TPH less than 3000 mg/Kg), these being: at 200°C for 20 minutes and at 300°C for 10, 15 and 20 minutes. The treatments at 150°C resulted in a TPH reduction insufficient to comply with Mexican norm, and also resulted in high MED values (3,46 - 3,67). At 200°C, the decrease in repellency was directly proportional to the treatment time (r=-0,950), with a final value of MED=2,61 after 20 minutes. At 300°C, an increase in water repellency was observed to be directly proportional to the treatment time (r=0,9997), with a final value of MED=3,73 (severe repellence) after 20 minutes. This may be due to the partial combustion (rather than only desorption) of hydrocarbons at this temperature, and their deposition on soil surfaces. Based on these observations, operating conditions of 200°C for 20 minutes are recommended to achieve effective thermal desorption while reducing water repellency in the treated material. If a final material with more severe water repellency is desired for use in construction, a higher operation temperature is required (300°C) for at least 15-20 minutes.

  12. Interaction of water with a Pd(110) surface, studied by thermal desorption spectroscopy, LEED and ??

    NASA Astrophysics Data System (ADS)

    He, Jian-Wei; Norton, P. R.

    1990-11-01

    The interaction of water with a Pd(110) surface has been studied by thermal desorption spectroscopy (TDS), work function change (??) and low energy electron diffraction (LEED). TD spectra of H 2O adsorbed on Pd(110) at 100 K show two peaks, one (A 2) at ˜ 200 K and the other (C 1) at ˜ 150 K. The A 2 state is interpreted as arising from molecularly chemisorbed H 2O. Saturation of the A 2 state causes a work function decrease of ˜ 780 mV. The chemisorbed water associated with the A 2 state in TDS is associated with a c(2 × 2) LEED pattern. The c(2 × 2) structure of H 2O on Pd(110) is probably analagous to that of H 2O on Ni(110). No dissociation of H 2O is found during adsorption and desorption of the A 2 state. No equivalent of the A 1 state observed on Ni(110) is detected on clean Pd(110). This difference between H 2O/Ni(110) and H 2O/Pd(110) is explained by a larger heat of formation of NiO than that of PdO. The C 1 peak arises from desorption of multilayers of water (so-called ice layers). It exhibits zero order kinetics with an activation energy Ea = 38 kJ mol -1 H 2O. H 2O in the C 1 state contributes ?? = -230 mV, which is m caused by the first layer of ice. A precoverage of oxygen on Pd(110) induces two peaks in TDS of H 2O. One (A 1) at low coverage of oxygen (? o) is believed to arise from dimer clusters of H 2O which are stabilized by the preadsorbed O. The other (C 2) at high ? o is probably from an ice layer that is strongly influenced by the surface O. Preadsorption of deuterium causes a continuous shift of the A 2 peak of H 2O to lower temperature and induces a new peak (A 3) at high deuterium coverages (? D) This shift to lower T is explained as due to the weakining of the surface-water bond by adsorbed D.

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

    PubMed

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

    2012-01-01

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

  14. Adsorption/desorption properties of vacuum materials for the 6 GeV synchrotron

    SciTech Connect

    Krauss, A.R.

    1985-01-01

    Considerable attention must be paid to the vacuum and adsorption/desorption properties of all materials installed inside the vacuum envelope if the design goals of the 6 GeV synchrotron are to be met. Unfortunately, the data is very sparse in several key areas. Additionally, some procedures normally associated with good vacuum practice, such as air baking, may prove to be totally unsuitable on the basis of desorption properties. We present here a brief discussion of the adsorption, outgassing, electron-stimulated desorption (ESD), and photon-stimulated desorption (PSD) properties of vacuum materials as they relate to the design of a 6 GeV synchrotron.

  15. Sequential desorption energy of hydrogen from nickel clusters

    NASA Astrophysics Data System (ADS)

    Deepika, R., Kamal Raj.; Kumar, T. J. Dhilip; Kumar, Rakesh

    2015-06-01

    We report reversible Hydrogen adsorption on Nickel clusters, which act as a catalyst for solid state storage of Hydrogen on a substrate. First-principles technique is employed to investigate the maximum number of chemically adsorbed Hydrogen molecules on Nickel cluster. We observe a maximum of four Hydrogen molecules adsorbed per Nickel atom, but the average Hydrogen molecules adsorbed per Nickel atom decrease with cluster size. The dissociative chemisorption energy per Hydrogen molecule and sequential desorption energy per Hydrogen atom on Nickel cluster is found to decrease with number of adsorbed Hydrogen molecules, which on optimization may help in economical storage and regeneration of Hydrogen as a clean energy carrier.

  16. Desorption electrospray ionization imaging of small organics on mineral surfaces.

    PubMed

    Bennett, Rachel V; Fernández, Facundo M

    2015-01-01

    Desorption electrospray ionization (DESI)-mass spectrometry facilitates the ambient chemical analysis of a variety of surfaces. Here we describe the protocol for using DESI imaging to measure the distributions of small prebiotically relevant molecules on granite surfaces. Granites that contain a variety of juxtaposed mineral species were reacted with formamide in order to study the role of local mineral environment on the production of purines and pyrimidines. The mass spectrometry imaging (MSI) methods described here can also be applied to the surface analysis of rock samples involved in other applications such as petroleum or environmental chemistries. PMID:25361668

  17. SURFACE STUDIES OF SIMPLE HYDROCARBONS ON IRIDIUM BY FLASH DESORPTION.

    SciTech Connect

    Burns, Robert Arthur

    1970-01-01

    Flash desorption of hydrogen and fourteen simple hydrocarbons on iridium was studied with decomposition products analyzed mass spectrometrically. Saturated hydrocarbons were found to absorb more slowly and to a smaller extent than the unsaturated hydrocarbons, and their decomposition was shown to occur below 400 degreesK. The decompositions of the unsaturated hydrocarbons were all similar in their hydrogen decomposition spectra and were not complete until 700 degreesK. Mechanisms are given for adsorption and decomposition which are consistent with the results. A model is proposed of the bonding to the surface to account for the adsorbed species observed. (author)

  18. Analysis of passive dosimeter samples by thermal desorption 

    E-print Network

    Schultz, Sherryl Anne

    1981-01-01

    Office, Washington, D. C. , (1972). 8. Fracchio, N. , et. al. : Desorption of Organic Solvents from Char- coal Tubes. Am. Ind. HyV. Assoc. J. 38: 144-146, (1977). 9. National Institute for Occupational Safety and Health: NIOSH N I of ~A al ti ~ I... Methods. 2nd Edfti ~ , Vol me ill, pp. 5311- 1-8. HEW Publication~No. NIOSH) 77-157C. U. S. Government Printing Office, Washington, D. C. , (1977). 10. National Institute for Occupational Safety and Health: Documenta- tio of NIGSH Validaiion Tests. HEW...

  19. Photochemical desorption from chlorinated Si(100) and Si(111) surfaces — Mechanisms and models

    NASA Astrophysics Data System (ADS)

    Rhodin, T.

    1995-12-01

    Understanding the mechanisms controlling the anisotropy of microetching is particularly critical as the scale of semiconductor devices shrink. Defining complex, dynamic chemical systems such as halogen etching require microscopic measurements combining kinetics, dynamics, surface layer composition and micromorphology on prototypical surfaces. This study is concerned with two important variables in addition to spontaneous chemical etching, the role of electronic defects induced by high level doping in producing site-specefic reaction and the enhancement of etching by irradiation at low fluences. Substitutional defects introduced by selective doping significantly influence the rate of chlorine etching by forming shallow electronic states that are ionized at room temperature 1. We have shown that chlorine sticking coeficients as well as laser-assisted etching are significantly affected by doping at very high dopant levels. Enhancement for n-type doping is consistent with the simple assumption that holes at the surface should enhance Si-Si surface bond breaking and in disagreement with the fact that heavily p-doped silicon has a higher chlorine sticking coefficient than n-doped material 2. Carrier effects generated by photoirradiation with above bandgap photons are considerably more complex than simple doping. A depletion layer and associated electric field are set up at the surface and minority carriers are preferentially swept to the surface. The type of photocarrier present at the surface is determined by both the doping and the photoirradiation. Using photoinduced etching of heavily doped Si(100) and Si(111) by chlorine at low laser fluences, we studied the mechanism of photostimulated desorption using core-level photoemission and time-of-flight measurements of the photoproducts 2. These results will be interpreted in terms of field-modified electron-hole transport together with carrier-modified chlorine adsorption and desorption.

  20. Auger decay mechanism in photon-stimulated desorption of ions from surfaces

    SciTech Connect

    Parks, C.C.

    1983-11-01

    Photon-stimulated desorption (PSD) of positive ions was studied with synchrotron radiation using an angle-integrating time-of-flight mass spectrometer. Ion yields as functions of photon energy near core levels were measured from condensed gases, alkali fluorides, and other alkali and alkaline earth halides. These results are compared to bulk photoabsorption measurements with emphasis on understanding fundamental desorption mechanisms. The applicability of the Auger decay mechanism, in which ion desorption is strictly proportional to surface absorption, is discussed in detail. The Auger decay model is developed in detail to describe Na/sup +/ and F/sup +/ desorption from NaF following Na(1s) excitation. The major decay pathways of the Na(1s) hole leading to desorption are described and equations for the energetics of ion desorption are developed. Ion desorption spectra of H/sup +/, Li/sup +/, and F/sup +/ are compared to bulk photoabsorption near the F(2s) and Li(1s) edges of LiF. A strong photon beam exposure dependence of ion yields from alkali fluorides is revealed, which may indicate the predominance of metal ion desorption from defect sites. The large role of indirect mechanisms in ion desorption condensed N/sub 2/-O/sub 2/ multilayers is demonstrated and discussed. Ion desorption spectra from several alkali halides and alkaline earth halides are compared to bulk photoabsorption spectra. Relative ion yields from BaF/sub 2/ and a series of alkali halides are discussed in terms of desorption mechanisms.

  1. Desorption of biocides from renders modified with acrylate and silicone.

    PubMed

    Styszko, Katarzyna; Bollmann, Ulla E; Wangler, Timothy P; Bester, Kai

    2014-01-01

    Biocides are used in the building industry to prevent algal, bacterial and fungal growth on polymericrenders and thus to protect buildings. However, these biocides are leached into the environment. To better understand this leaching, the sorption/desorption of biocides in polymeric renders was assessed. In this study the desorption constants of cybutryn, carbendazim, iodocarb, isoproturon, diuron, dichloro-N-octylisothiazolinone and tebuconazole towards acrylate and silicone based renders were assessed at different pH values. At pH 9.5 (porewater) the constants for an acrylate based render varied between 8 (isoproturon) and 9634 (iodocarb) and 3750 (dichloro-N-octylisothiazolinone), respectively. The values changed drastically with pH value. The results for the silicone based renders were in a similar range and usually the compounds with high sorption constants for one polymer also had high values for the other polymer. Comparison of the octanol water partitioning constants (Kow) with the render/water partitioning constants (Kd) revealed similarities, but no strong correlation. Adding higher amounts of polymer to the render material changed the equilibria for dichloro-N-octylisothiazolinone, tebuconazole, cybutryn, carbendazim but not for isoproturon and diuron. PMID:24059976

  2. Characterization of polymer decomposition products by laser desorption mass spectrometry

    NASA Technical Reports Server (NTRS)

    Pallix, Joan B.; Lincoln, Kenneth A.; Miglionico, Charles J.; Roybal, Robert E.; Stein, Charles; Shively, Jon H.

    1993-01-01

    Laser desorption mass spectrometry has been used to characterize the ash-like substances formed on the surfaces of polymer matrix composites (PMC's) during exposure on LDEF. In an effort to minimize fragmentation, material was removed from the sample surfaces by laser desorption and desorbed neutrals were ionized by electron impact. Ions were detected in a time-of-flight mass analyzer which allows the entire mass spectrum to be collected for each laser shot. The method is ideal for these studies because only a small amount of ash is available for analysis. Three sets of samples were studied including C/polysulfone, C/polyimide and C/phenolic. Each set contains leading and trailing edge LDEF samples and their respective controls. In each case, the mass spectrum of the ash shows a number of high mass peaks which can be assigned to fragments of the associated polymer. These high mass peaks are not observed in the spectra of the control samples. In general, the results indicate that the ash is formed from decomposition of the polymer matrix.

  3. Sorption and desorption of quaternary amine cations on clays

    SciTech Connect

    Zhang, Z.Z.; Sparks, D.L. (Univ. of Delaware, Newark, DE (United States)); Scrivner, N.C. (DuPont Engineering, Newark, DE (United States))

    1993-08-01

    The authors have studied the sorption and desorption of three quaternary amines, namely, nonyltrimethylammonium, dodecyltrimethylammonium, and hexadecyltrimethylammonium, on homoionic Na- and K-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were sorbed on the montmorillonite when the added amines were less than 70% of the cation-exchange capacity of the montmorillonite. Sorption of quaternary amine cations involves at least two types of reactions, namely, an exchange reaction and the adsorption of amines at nonexchangeable sites. The exchange reaction proceeded almost to completion when Na[sup +] was the exchangeable cation. Exchangeable K[sup +] was much more difficult to replace. The adsorbed quaternary amine cations were not easily desorbed in the presence of 0.1 M NaCl and KCl solutions. In addition, desorption of quaternary amines did not increase with prolonged equilibrium time, up to 180 days. Therefore, it appears that there is good promise in using quaternary amine-modified clays as effective sorbents for removing organic pollutants or mitigating their mobilities in the environment. 26 refs., 5 figs., 6 tabs.

  4. Fundamental studies of matrix-assisted laser desorption/ionization

    SciTech Connect

    Hurst, G.B. [Oak Ridge National Laboratory, TN (United States)

    1994-12-31

    Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has been remarkably successful for molecular weight determination of biomolecules. However, the efficiency of ionization, and therefore the sensitivity of the technique, could be improved if details of the ionization mechanism were understood more thoroughly. The chemical and physical environment in the MALDI plume produced by the desorption laser influences the ionization of the analyte, in analogy to the effect of pH on biomolecules in solution. Optical probing techniques, such as laser-induced fluorescence, allow some characteristics of the plume environment to be studied directly. Fluorescence emitted during MALDI experiments using 2,5-dihydroxybenzoic acid (DHB) as the matrix exhibits a broad feature more similar to the emission spectrum of DHB in acidic solution than in neutral or basic solution, suggesting that proton transfer equilibria in the plume can be probed optically. Additionally, narrower features appear in the DHB fluorescence in the MALDI experiment. The origin of these narrow features is not known, but they may be due to emission from small fragments of the matrix, or to cooling of the matrix due to expansion of the plume into the vacuum. In addition to studying the fundamentals of the MALDI ionization mechanism, correlation of plume fluorescence with the efficacy of a given compound as a MALDI matrix may provide a useful optimization tool.

  5. REACTIVE DESORPTION AND RADIATIVE ASSOCIATION AS POSSIBLE DRIVERS OF COMPLEX MOLECULE FORMATION IN THE COLD INTERSTELLAR MEDIUM

    SciTech Connect

    Vasyunin, A. I. [Department of Chemistry, University of Virginia, Charlottesville, VA (United States); Herbst, Eric, E-mail: anton.vasyunin@gmail.com, E-mail: eh2ef@virginia.edu [Departments of Chemistry, Astronomy, and Physics, University of Virginia, Charlottesville, VA (United States)

    2013-05-20

    The recent discovery of terrestrial-type organic species such as methyl formate and dimethyl ether in the cold interstellar gas has proved that the formation of organic matter in the Galaxy begins at a much earlier stage of star formation than was previously thought. This discovery represents a challenge for astrochemical modelers. The abundances of these molecules cannot be explained by the previously developed ''warm-up'' scenario, in which organic molecules are formed via diffusive chemistry on surfaces of interstellar grains starting at 30 K, and then released to the gas at higher temperatures during later stages of star formation. In this article, we investigate an alternative scenario in which complex organic species are formed via a sequence of gas-phase reactions between precursor species formed on grain surfaces and then ejected into the gas via efficient reactive desorption, a process in which non-thermal desorption occurs as a result of conversion of the exothermicity of chemical reactions into the ejection of products from the surface. The proposed scenario leads to reasonable if somewhat mixed results at temperatures as low as 10 K and may be considered as a step toward the explanation of abundances of terrestrial-like organic species observed during the earliest stages of star formation.

  6. CO adsorption and desorption on size-selected Pd(n)/TiO2(110) model catalysts: size dependence of binding sites and energies, and support-mediated adsorption.

    PubMed

    Kaden, William E; Kunkel, William A; Roberts, F Sloan; Kane, Matthew; Anderson, Scott L

    2012-05-28

    The nature of CO adsorption on Pd(n)/TiO(2)(110) (n = 1, 2, 7, 20) has been examined using temperature-programmed desorption (TPD), temperature-dependent helium ion scattering (TD-ISS), and X-ray photoelectron spectroscopy (XPS). All samples contain the same number of Pd atoms (0.10 ML-equivalent) deposited as different size clusters. The TPD and TD-ISS show that CO binds in two types of sites associated with the Pd clusters. The most stable sites are on top of the Pd clusters ("on-top" sites), however, there are also less stable sites, in which CO is bound in association with, but not on top of the Pd ("peripheral" sites). For saturation CO coverage over a fixed atomic concentration of Pd (present in the form of Pd(n) clusters of varying size), the population of CO in peripheral sites decreases with increasing cluster size, while the on-top site population is size-independent. This is consistent with what geometric considerations would predict for the density of the two types of sites, provided the clusters adsorb predominantly as 2D islands, which ISS results suggest to be the case. The XPS analysis indicates that CO-Pd binding is dominated by ?-backbonding to the Pd(n) clusters. The results also show evidence for efficient support-mediated adsorption (reverse-spillover) of CO initially impinging on TiO(2) to binding sites associated with the Pd clusters. PMID:22667579

  7. CO adsorption and desorption on size-selected Pdn/TiO2(110) model catalysts: Size dependence of binding sites and energies, and support-mediated adsorption

    NASA Astrophysics Data System (ADS)

    Kaden, William E.; Kunkel, William A.; Roberts, F. Sloan; Kane, Matthew; Anderson, Scott L.

    2012-05-01

    The nature of CO adsorption on Pdn/TiO2(110) (n = 1, 2, 7, 20) has been examined using temperature-programmed desorption (TPD), temperature-dependent helium ion scattering (TD-ISS), and X-ray photoelectron spectroscopy (XPS). All samples contain the same number of Pd atoms (0.10 ML-equivalent) deposited as different size clusters. The TPD and TD-ISS show that CO binds in two types of sites associated with the Pd clusters. The most stable sites are on top of the Pd clusters ("on-top" sites), however, there are also less stable sites, in which CO is bound in association with, but not on top of the Pd ("peripheral" sites). For saturation CO coverage over a fixed atomic concentration of Pd (present in the form of Pdn clusters of varying size), the population of CO in peripheral sites decreases with increasing cluster size, while the on-top site population is size-independent. This is consistent with what geometric considerations would predict for the density of the two types of sites, provided the clusters adsorb predominantly as 2D islands, which ISS results suggest to be the case. The XPS analysis indicates that CO-Pd binding is dominated by ?-backbonding to the Pdn clusters. The results also show evidence for efficient support-mediated adsorption (reverse-spillover) of CO initially impinging on TiO2 to binding sites associated with the Pd clusters.

  8. Electrochemical Desorption of Self-Assembled Monolayers Noninvasively Releases Patterned Cells from Geometrical Confinements

    E-print Network

    Mrksich, Milan

    Electrochemical Desorption of Self-Assembled Monolayers Noninvasively Releases Patterned Cells from on the electrochemical desorption of self-assembled monolayers (SAMs) to release pat- terned mammalian cells from steel electrode) on gold caused the SAMs to desorb.5,6 Removal of EG3-terminated SAMs from a gold

  9. AGING EFFECTS ON SORPTION-DESORPTION AND DISSIPATION OF SIMAZINE IN SOIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to protect ground and surface waters from pesticide contamination, broad knowledge is required of sorption-desorption and biodegradation processes since they control the amount of chemical available for pest control and transport. In this study, effects of aging on sorption-desorption and d...

  10. Gas-Well Testing in the Presence of Desorption for Coalbed Methane and Devonian Shale

    Microsoft Academic Search

    A. C. Bumb; C. R. McKee

    1988-01-01

    Very large potential gas reserves are present in both coalbeds and Devonian shales. In both formation types, long-term gas production is the result of gas desorption from the matrix. Experiments on core samples show that the desorption obeys a Langmuir isotherm. An approximate analytic solution is derived for single-phase gas flow when gas is present as both free gas and

  11. Permeability of coals and characteristics of desorption tests: Implications for coalbed methane production

    Microsoft Academic Search

    W. Rupert Bodden; Robert Ehrlich

    1998-01-01

    Desorption tests, conducted before development drilling, can predict early production rates of coalbed methane wells. In this study, results from 136 desorption tests from 30 coreholes are compared to subsequent production histories of surrounding wells. Coals studied are from the Carboniferous Pottsville Formation in the Black Warrior Basin of Alabama, USA. The investigation indicates that the best predictor for gas

  12. Fast production of ultracold sodium gases using lightinduced desorption and optical Emmanuel Mimoun,1,

    E-print Network

    Paris-Sud XI, Université de

    Fast production of ultracold sodium gases using light­induced desorption and optical trapping report on the production of a Bose­Einstein condensate (BEC) of sodium using light­induced desorption) when the sodium cloud is used as a buffer gas for sympathetic cooling [4]. Sodium also has antiferromag

  13. Quantifying Desorption of Saturated Hydrocarbons from Silicon with Quantum Calculations and Scanning Tunneling Microscopy

    E-print Network

    Seideman, Tamar

    hydrocarbon on silicon, desorption is observed at bias magnitudes as low as 2.5 V, albeit the desorption this expectation holds true. On the other hand, it is desirable to explore systems that will provide dynamical yield for sample bias voltages from ÿ5 V to 5 V show a clear turn-on behavior, with asymmetric threshold

  14. Sorption and desorption kinetics of diuron, fluometuron, prometryn and pyrithiobac sodium in soils

    Microsoft Academic Search

    S. Baskaran; I. R. Kennedy

    1999-01-01

    The sorption and desorption characteristics of four herbicides (diuron, fluometuron, prometryn and pyrithiobac?sodium) in three different cotton growing soils of Australia was investigated. Kinetics and equilibrium sorption and desorption isotherms were determined using the batch equilibrium technique. Sorption was rapid (> 80% in 2 h) and sorption equilibrium was achieved within a short period of time (ca 4 h) for

  15. Laser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon microcolumn arrays

    E-print Network

    Vertes, Akos

    -based substrate (a.k.a. black silicon) was developed as a new matrix-free laser desorption ionization surface.k.a. black silicon). Submicron size particles, micro and nanostructured surfaces have been used to facilitateLaser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon

  16. Sorption and desorption of selenium in different soils of the mediterranean area

    Microsoft Academic Search

    B. Pezzarossa; D. Piccotino; G. Petruzzelli

    1999-01-01

    The adsorption of selenium (Se) in the selenate form and its desorption by phosphate in four soils with different physiochemical properties were studied in the laboratory. To determine adsorption isotherms for selenate 25 mL of solutions containing 1 to 100 ppm of Se were added to 2.5 g of soil. Desorption isotherms were determined by resuspending the samples in phosphate

  17. Laser Desorption Single-Photon Ionization of Asphaltenes: Mass Range, Compound Sensitivity, and Matrix Effects

    E-print Network

    Zare, Richard N.

    Laser Desorption Single-Photon Ionization of Asphaltenes: Mass Range, Compound Sensitivity and flow assurance. Laser desorption single-photon ionization mass spectrometry (LDSPI-MS) has emerged, such as their molecular mass distribution and dominant molecular architecture.1,6-11 Laser mass spectrometry, including

  18. Influence of soil properties on heavy metal sequestration by biochar amendment: 2. copper desorption isotherms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Contaminant desorption constrains the long-term effectiveness of remediation technologies, and is strongly influenced by dynamic non-equilibrium states of environmental and biological media. Information is currently lacking in the influence of biochar and activated carbon amendments on desorption of...

  19. Silica-fiber microextraction for laser desorption ion trap mass spectrometry

    Microsoft Academic Search

    M. E. Cisper; W. L. Earl; N. S. Nogar; P. H. Hemberger

    1994-01-01

    We have coupled sample collection by solid-phase microextraction on disposable fused silica optical fibers with analysis by laser desorption ion trap mass spectrometry for rapid screening of organic contaminants in complex matrices. Because the silica-fiber probe serves as both the sampling medium and the sample support for laser desorption, traditional methods of sample preparation are eliminated with the expected gains

  20. Adsorption and Desorption of Atrazine, Desethylatrazine, Deisopropylatrazine, and Hydroxyatrazine in Vegetated Filter Strip and Cultivated Soil

    Microsoft Academic Search

    Larry Jason Krutz; Scott Allen Senseman; Kevin Joseph McInnes; David Allen Zuberer; Dennis Patrick Tierney

    2003-01-01

    Adsorption and desorption of atrazine and its metabolites in vegetated filter strip soil (VFS) has not been evaluated, yet these data are needed to predict the transport of these compounds through the VFS. Adsorption and desorption parameters for atrazine, desethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA) were compared between a cultivated Houston Black clay (CS) and an adjacent 12-year-old VFS

  1. Surface scanning analysis of planar arrays of analytes with desorption electrospray ionization-mass spectrometry.

    PubMed

    Pasilis, Sofie P; Kertesz, Vilmos; Van Berkel, Gary J

    2007-08-01

    The analysis of analytes deposited on, separated on, or otherwise distributed about a planar surface using desorption electrospray ionization mass spectrometry in a surface scanning sampling mode was investigated. The physical regions of the surface-impacting solvent/gas jet desorption/ionization plume were described. Under the conditions typical for desorption electrospray ionization used here, the impact plume formed an elliptical desorption/ionization region on the surface. Most effective desorption/ionization was obtained from a smaller elliptical area within the larger impact region that was centered on a point on-axis from the sprayer tip to the surface. Maximum signal from a given amount of material on a surface was observed with proper plume and sample alignment when the diameter of the sample spot was less than the diameter of the central high-efficiency desorption/ionization region of the impact plume. Solvent and gas flow out of this high-efficiency desorption/ionization region was found to limit analyte accessibility to this region via a "washing effect" when analytes were on smooth surfaces or on surfaces for which the analyte had little affinity. As such, the direction of surface scanning and scan speed during an analysis was found to be important for maximizing signal levels and signal reproducibility on particular surface types. Overall, the results presented illustrate means to improve analysis of sample spots on various types of surfaces using desorption electrospray ionization mass spectrometry in a surface scanning mode. PMID:17605468

  2. Discovery of spontaneous deformation of Pd metal during hydrogen absorption/desorption cycles

    PubMed Central

    Yamazaki, Toshimitsu; Sato, Masaharu; Itoh, Satoshi

    2009-01-01

    A drastic deformation was observed in Pd metal of various shapes after hydrogen absorption and desorption cycles at 150 °C at a gas pressure of 1–5 MPa. All of the phenomena observed indicate that some strong internal force is induced spontaneously during hydrogen absorption/desorption cycles to produce a collective deformation so as to minimize the surface. PMID:19444010

  3. Discovery of spontaneous deformation of Pd metal during hydrogen absorption/desorption cycles.

    PubMed

    Yamazaki, Toshimitsu; Sato, Masaharu; Itoh, Satoshi

    2009-01-01

    A drastic deformation was observed in Pd metal of various shapes after hydrogen absorption and desorption cycles at 150 degrees C at a gas pressure of 1-5 MPa. All of the phenomena observed indicate that some strong internal force is induced spontaneously during hydrogen absorption/desorption cycles to produce a collective deformation so as to minimize the surface. PMID:19444010

  4. Kinetics of Desorption of Heavy Metals from Polluted Soils: Influence of Soil Type and Metal Source

    Microsoft Academic Search

    Geeta Kandpal; P. C. Srivastava; Bali Ram

    2005-01-01

    Kinetics of desorption of heavy metal ions (Cd, Cu, Ni and Zn) from the surface (0–15 cm) samples of an acidic soil (Inceptisol) and a neutral soil (Mollisol) spiked with inorganic salts of these metals or through an acidic sludge were studied by the column method. The rate of desorption of soil applied heavy metals was initially rapid and gradually

  5. About Temperature

    NSDL National Science Digital Library

    Beverly Lynds at the Unidata Program Center has made available the About Temperature Website. Here Lynds provides a thorough discussion of temperature along with information about and diagrams of thermometers, heat and thermodynamics, kinetic theory, and radiation temperature. Descriptions are brief but clear and well-illustrated with links throughout. In addition, references are cited along with related links. This site is also available in Spanish.

  6. Feasibility of desorption atmospheric pressure photoionization and desorption electrospray ionization mass spectrometry to monitor urinary steroid metabolites during pregnancy.

    PubMed

    Vaikkinen, Anu; Rejšek, Jan; Vrkoslav, Vladimír; Kauppila, Tiina J; Cva?ka, Josef; Kostiainen, Risto

    2015-06-23

    Steroids have important roles in the progress of pregnancy, and their study in maternal urine is a non-invasive method to monitor the steroid metabolome and its possible abnormalities. However, the current screening techniques of choice, namely immunoassays and gas and liquid chromatography-mass spectrometry, do not offer means for the rapid and non-targeted multi-analyte studies of large sample sets. In this study, we explore the feasibility of two ambient mass spectrometry methods in steroid fingerprinting. Urine samples from pregnant women were screened by desorption electrospray ionization (DESI) and desorption atmospheric pressure photoionization (DAPPI) Orbitrap high resolution mass spectrometry (HRMS). The urine samples were processed by solid phase extraction for the DESI measurements and by enzymatic hydrolysis and liquid-liquid-extraction for DAPPI. Consequently, steroid glucuronides and sulfates were detected by negative ion mode DESI-HRMS, and free steroids by positive ion mode DAPPI-HRMS. In DESI, signals of eleven steroid metabolite ions were found to increase as the pregnancy proceeded, and in DAPPI ten steroid ions showed at least an order of magnitude increase during pregnancy. In DESI, the increase was seen for ions corresponding to C18 and C21 steroid glucuronides, while DAPPI detected increased excretion of C19 and C21 steroids. Thus both techniques show promise for the steroid marker screening in pregnancy. PMID:26092341

  7. Bench- and pilot-scale thermal desorption treatability studies on pesticide-contaminated soils from Rocky Mountain Arsenal

    SciTech Connect

    Swanstrom, C.P. [Argonne National Lab., IL (United States); Besmer, M. [Rocky Mountain Arsenal, Denver, CO (United States)

    1995-03-09

    Thermal desorption is being considered as a potential remediation technology for pesticide-contaminated soils at the Rocky Mountain Arsenal (RMA) in Denver, Colorado. From 1988 through 1992, numerous laboratory- and bench-scale indirect-heated thermal desorption (IHTD) treatability studies have been performed on various soil medium groups from the arsenal. RMA has contracted Argonne National Laboratory to conduct a pilot-scale direct-fired thermal desorption (DFTD) treatability study on pesticide-contaminated RMA soil. The purpose of this treatability study is to evaluate the overall effectiveness of the DFTD technology on contaminated RMA soils and to provide data upon which future conceptual design assumptions and cost estimates for a full-scale system can be made. The equipment used in the DFTD treatability study is of large enough scale to provide good full-scale design parameters and operating conditions. The study will also provide valuable-emissions and materials-handling data. Specifically this program will determine if DFTD can achieve reductions in soil contamination below the RMA preliminary remediation goals (PRGs), define system operating conditions for achieving the PRGs, and determine the fate of arsenic and other hazardous metals at these operating conditions. This paper intends to compare existing data from a bench-scale IHTD treatability study using equipment operated in the batch mode to new data from a pilot-scale DFTD operated in a parallel-flow continuous mode. Delays due to materials-handling problems and permit issues have delayed the start of the pilot-scale DFTD testing. The first pilot-scale test is scheduled for the flat week in January 1995. The available data will be presented March 9, 1995, at the Seventh Annual Gulf Coast Environmental Conference in Houston, Texas.

  8. Atmospheric pressure matrix-assisted laser desorption ionization as a plume diagnostic tool in laser evaporation methods

    E-print Network

    Vertes, Akos

    Atmospheric pressure matrix-assisted laser desorption ionization as a plume diagnostic tool introduced analytical method, atmospheric pressure matrix-assisted laser desorption ionization (AP- MALDI write; Atmospheric pressure MALDI; Laser evaporation; Plume diagnostics 1. Introduction Diagnostics

  9. Program

    Cancer.gov

    Through the DCIDE program, the developer of a promising diagnostic agent or probe will be given access to the pre-clinical development resources of the National Cancer Institute in a manner that is intended to remove the most common barriers between laboratory discoveries and IND status.

  10. Diffusion, adsorption, and desorption of molecular hydrogen on graphene and in graphite

    NASA Astrophysics Data System (ADS)

    Petucci, Justin; LeBlond, Carl; Karimi, Majid; Vidali, Gianfranco

    2013-07-01

    The diffusion of molecular hydrogen (H2) on a layer of graphene and in the interlayer space between the layers of graphite is studied using molecular dynamics computer simulations. The interatomic interactions were modeled by an Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. Molecular statics calculations of H2 on graphene indicate binding energies ranging from 41 meV to 54 meV and migration barriers ranging from 3 meV to 12 meV. The potential energy surface of an H2 molecule on graphene, with the full relaxations of molecular hydrogen and carbon atoms is calculated. Barriers for the formation of H2 through the Langmuir-Hinshelwood mechanism are calculated. Molecular dynamics calculations of mean square displacements and average surface lifetimes of H2 on graphene at various temperatures indicate a diffusion barrier of 9.8 meV and a desorption barrier of 28.7 meV. Similar calculations for the diffusion of H2 in the interlayer space between the graphite sheets indicate high and low temperature regimes for the diffusion with barriers of 51.2 meV and 11.5 meV. Our results are compared with those of first principles.

  11. Efficient Methods to Generate Reproducible Mass Spectra in Matrix-Assisted Laser Desorption Ionization of Peptides

    NASA Astrophysics Data System (ADS)

    Ahn, Sung Hee; Park, Kyung Man; Bae, Yong Jin; Kim, Myung Soo

    2013-06-01

    In our previous matrix-assisted laser desorption ionization (MALDI) studies of peptides, we found that their mass spectra were virtually determined by the effective temperature in the early matrix plume, Tearly, when samples were rather homogeneous. This empirical rule allowed acquisition of quantitatively reproducible spectra. A difficulty in utilizing this rule was the complicated spectral treatment needed to get Tearly. In this work, we found another empirical rule that the total number of particles hitting the detector, or TIC, was a good measure of the spectral temperature and, hence, selection of spectra with the same TIC resulted in reproducible spectra. We also succeeded in obtaining reproducible spectra throughout a measurement by controlling TIC near a preset value through feedback adjustment of laser pulse energy. Both TIC selection and TIC control substantially reduced the shot-to-shot spectral variation in a spot, spot-to-spot variation in a sample, and even sample-to-sample variation in MALDI using ?-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic acid as matrix. Based on the utilization of acquired data, TIC control was more efficient than TIC selection by an order of magnitude. Both techniques produced calibration curves with excellent linearity, suggesting their utility in quantification of peptides.

  12. Predictive modeling of sorption and desorption of a reactive azo dye by pumpkin husk.

    PubMed

    Çelekli, Abuzer; Çelekli, Fadime; Çiçek, Erdo?an; Bozkurt, Hüseyin

    2014-04-01

    The use of effective disposal of redundant pumpkin husk (PH) to remove pollutants is an important issue for environmental protection and utilization of resource. The aim of this study was to remove a potentially toxic reactive azo dye, Reactive Red (RR) 120, by widespread PH as a low-cost adsorbent. Particle size, adsorbent dose, pH, temperature, initial dye concentration, and contact time affected the sorption process. Amine, amide, hydroxyl, and carboxyl groups of PH played significant roles on the sorption process. Rapid sorption occurred within the first 2 min and equilibrium was reached within 60 min. Sorption kinetic was well represented by logistic equation. Generated secondary logistic model can be used to describe effects of initial dye concentration, contact time, and temperature by a single equation with high R (2) value. Monolayer sorption capacity was found as 98.61 mg g(-1). Activation energy, thermodynamic, and desorption studies showed that this process was physical, endothermic, and spontaneous. This study indicated that redundant PH as a low-cost adsorbent had a great potential for the removal of RR 120 as an alternative eco-friendly process. PMID:24374618

  13. Diffusion, adsorption, and desorption of molecular hydrogen on graphene and in graphite.

    PubMed

    Petucci, Justin; LeBlond, Carl; Karimi, Majid; Vidali, Gianfranco

    2013-07-28

    The diffusion of molecular hydrogen (H2) on a layer of graphene and in the interlayer space between the layers of graphite is studied using molecular dynamics computer simulations. The interatomic interactions were modeled by an Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. Molecular statics calculations of H2 on graphene indicate binding energies ranging from 41 meV to 54 meV and migration barriers ranging from 3 meV to 12 meV. The potential energy surface of an H2 molecule on graphene, with the full relaxations of molecular hydrogen and carbon atoms is calculated. Barriers for the formation of H2 through the Langmuir-Hinshelwood mechanism are calculated. Molecular dynamics calculations of mean square displacements and average surface lifetimes of H2 on graphene at various temperatures indicate a diffusion barrier of 9.8 meV and a desorption barrier of 28.7 meV. Similar calculations for the diffusion of H2 in the interlayer space between the graphite sheets indicate high and low temperature regimes for the diffusion with barriers of 51.2 meV and 11.5 meV. Our results are compared with those of first principles. PMID:23902002

  14. Studies of pore structure, temperature-programmed reduction performance, and micro-structure of CuO\\/CeO 2 catalysts

    Microsoft Academic Search

    Jiang Xiaoyuan; Lu Guanglie; Zhou Renxian; Mao Jianxin; Chen Yu; Zheng Xiaoming

    2001-01-01

    The reducibility and characteristics of CuO, CeO2 and CuO\\/CeO2 catalysts were examined by means of a CO microreactor gas chromatography, specific surface area, pore volume, H2-temperature-programmed reduction (TPR), and X-ray diffraction Rietveld analysis. Experimental results showed that the specific surface area and pore volume of the CuO\\/CeO2 catalysts decreased with an increase in CuO loading, whereas the average pore diameter

  15. Large-volume injection in residue analysis with capillary gas chromatography using a conventional autosampler and injection by programmed-temperature vaporization with solvent venting

    Microsoft Academic Search

    Hans-Jürgen Stan; Manfred Linkerhägner

    1996-01-01

    Large-volume injection in capillary gas chromatography may be used to compensate for the limited detection sensitivity of selective detectors when further evaporation of sample extracts is not feasible owing to increasing losses of volatile solutes or because the analytical method can no longer be performed automatically. Large-volume injection using programmed-temperature vaporization (PTV) with solvent venting has proved its worth as

  16. Analysis of class 1 residual solvents in pharmaceuticals using headspace-programmed temperature vaporization-fast gas chromatography–mass spectrometry

    Microsoft Academic Search

    José Luis Pérez Pavón; Miguel del Nogal Sánchez; M Fernández Laespada; Carmelo García Pinto; Bernardo Moreno Cordero

    2007-01-01

    A sensitive method is presented for the fast screening and determination of residual class 1 solvents (1,1-dichloroethene, 1,2-dichloroethane, 1,1,1-trichloroethane, carbon tetrachloride and benzene) in pharmaceutical products. The applicability of a headspace (HS) autosampler in combination with GC equipped with a programmed temperature vaporizer (PTV) and a MS detector is explored. Different injection techniques were compared. The benefits of using solvent

  17. The Reduction Behavior of Fe-Mo-O Catalysts Studied by Temperature-Programmed Reduction Combined with in Situ Mössbauer Spectroscopy and X-Ray Diffraction

    Microsoft Academic Search

    Huiliang Zhang; Jianyi Shen; Xin Ge

    1995-01-01

    The reduction processes of Fe-Mo-O catalysts with different Fe\\/Mo atomic ratios were studied by means of temperature-programmed reduction (TPR). In particular, the reduction process of a sample with an Fe\\/Mo ratio of 0.29 was investigated in detail in combination with in situ Mössbauer spectroscopy (MBS) and X-ray diffraction (XRD). Five peaks are observed in the TPR profile of this sample

  18. Combined temperature-programmed reaction and in situ x-ray scattering studies of size-selected silver clusters under realistic reaction conditions in the epoxidation of propene

    Microsoft Academic Search

    Stefan Vajda; Sungsik Lee; Kristian Sell; Ingo Barke; Armin Kleibert; Viola von Oeynhausen; Karl-Heinz Meiwes-Broer; Arantxa Fraile Rodríguez; Jeffrey W. Elam; Michael M. Pellin; Byeongdu Lee; Sönke Seifert; Randall E. Winans; Swiss Light Source

    2009-01-01

    The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions for the first time. The approach is

  19. Kinetics of Potassium Desorption in Soil using Miscible Displacement1 D. L. SPARKS, L. W. ZELAZNY, AND D. C. MARTENSZ

    E-print Network

    Sparks, Donald L.

    Kinetics of Potassium Desorption in Soil using Miscible Displacement1 D. L. SPARKS, L. W. ZELAZNY clay minerals present in the soils. Potassium desorption conformed to first-order kinetics. Ap- parent. Martens. 1980. Kinetics of potassium desorption in soil using miscible displacement. Soil Sci. Soc. Am. J

  20. Enhanced durability of high-temperature desulfurization sorbents for moving-bed applications. Option 2 Program: Development and testing of zinc titanate sorbents

    SciTech Connect

    Ayala, R.E.

    1993-04-01

    One of the most advantageous configurations of the integrated gasification combined cycle (IGCC) power system is coupling it with a hot gas cleanup for the more efficient production of electric power in an environmentally acceptable manner. In conventional gasification cleanup systems, closely heat exchangers are necessary to cool down the fuel gases for cleaning, sometimes as low as 200--300{degree}F, and to reheat the gases prior to injection into the turbine. The result is significant losses in efficiency for the overall power cycle. High-temperature coal gas cleanup in the IGCC system can be operated near 1000{degree}F or higher, i.e., at conditions compatible with the gasifier and turbine components, resulting is a more efficient overall system. GE is developing a moving-bed, high-temperature desulfurization system for IGCC power systems in which mixed-metal oxides are currently being used as desulfurization sorbents. The objective of this contract is to identify and test fabrication methods and sorbent chemical compositions that enhance the long-term chemical reactivity and mechanical durability of zinc ferrite and other novel sorbents for moving-bed, high-temperature desulfurization of coal-derived gases. Zinc ferrite was studied under the base program of this contract. In the next phase of this program novel sorbents, particularly zinc titanate-based sorbents, are being studied under the remaining optional programs. This topical report summarizes only the work performed under the Option 2 program. In the course of carrying out the program, more than 25 zinc titanate formulations have been prepared and characterized to identify formulations exhibiting enhanced properties over the baseline zinc titanate formulation selected by the US Department of Energy.

  1. Adsorption-desorption characteristics of lead in variable charge soils.

    PubMed

    Yang, J Y; Yang, X E; He, Z L; Chen, G C; Shentu, J L; Li, T Q

    2004-01-01

    Adsorption desorption processes of Pb at contaminated levels in two variable charge soils were investigated. The red soil (RAR) developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) adsorbed more Pb2+ than the red soil (REQ) derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 52.6 mmol Pb2+ kg(-1) soil and 29.9 mmol Pb2+ kg(-1) soil, respectively, for the RAR and REQ. Adsorption of Pb2+ decreased soil pH by 1.10 unit for the RAR soil and 1.21 unit for the REQ soil at the highest loading. The adsorption equilibrium pH of RAR was higher than that of REQ at the same Pb2+ concentration. The distribution coefficient (Kd) of Pb in the soils decreased exponentially with increasing Pb2+ loading. Most of the adsorbed Pb2+ in the soils was not desorbed in the 0.01 mol L(-1) NaNO3 solution. After five successive extractions with NaNO3, only 0-11% of the total adsorbed Pb2+ in the RAR soil was desorbed and the corresponding value of the REQ soil was 0-19%, indicating that the RAR soil had a greater affinity for Pb2+ than the REQ soil at the same Pb2+ loading. Different mechanisms might be involved in Pb2+ adsorption/desorption at different levels of Pb2+ loading and between the two soils. PMID:15332661

  2. Sorption and desorption of arsenate and arsenite on calcite

    NASA Astrophysics Data System (ADS)

    Sø, Helle U.; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

    2008-12-01

    The adsorption and desorption of arsenate (As(V)) and arsenite (As(III)) on calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic concentrations were kept low (<33 ?M) to avoid surface precipitation. The results show that little or no arsenite sorbs on calcite within 24 h at an initial As concentration of 0.67 ?M. In contrast, arsenate sorbs readily and quickly on calcite. Likewise, desorption of arsenate from calcite is fast and complete within hours, indicating that arsenate is not readily incorporated into the calcite crystal lattice. The degree of arsenate sorption depends on the solution chemistry. Sorption increases with decreasing alkalinity, indicating a competition for sorption sites between arsenate and (bi)carbonate. pH also affects the sorption behavior, likely in response to changes in arsenate speciation or protonation/deprotonation of the adsorbing arsenate ion. Finally, sorption is influenced by the ionic strength, possibly due to electrostatic effects. The sorption of arsenate on calcite was modeled successfully using a surface complexation model comprising strong and weak sites. In the model, the adsorbing arsenate species were HAsO4- and CaHAsO40. The model was able to correctly predict the adsorption of arsenate in the wide range of calcite-equilibrated solutions used in the batch experiments and to describe the non-linear shape of the sorption isotherms. Extrapolation of the experimental results to calcite bearing aquifers suggests a large variability in the mobility of arsenic. Under reduced conditions, arsenite, which does not sorb on calcite, will dominate and, hence, As will be highly mobile. In contrast, when conditions are oxidizing, arsenate is the predominant species and, because arsenate adsorbs strongly on calcite, As mobility will be significantly retarded. The estimated retardation factors for arsenate in carbonate aquifers range from 25 to 200.

  3. Laser desorption mass spectrometry for DNA analysis and sequencing

    SciTech Connect

    Chen, C.H.; Taranenko, N.I.; Tang, K.; Allman, S.L.

    1995-03-01

    Laser desorption mass spectrometry has been considered as a potential new method for fast DNA sequencing. Our approach is to use matrix-assisted laser desorption to produce parent ions of DNA segments and a time-of-flight mass spectrometer to identify the sizes of DNA segments. Thus, the approach is similar to gel electrophoresis sequencing using Sanger`s enzymatic method. However, gel, radioactive tagging, and dye labeling are not required. In addition, the sequencing process can possibly be finished within a few hundred microseconds instead of hours and days. In order to use mass spectrometry for fast DNA sequencing, the following three criteria need to be satisfied. They are (1) detection of large DNA segments, (2) sensitivity reaching the femtomole region, and (3) mass resolution good enough to separate DNA segments of a single nucleotide difference. It has been very difficult to detect large DNA segments by mass spectrometry before due to the fragile chemical properties of DNA and low detection sensitivity of DNA ions. We discovered several new matrices to increase the production of DNA ions. By innovative design of a mass spectrometer, we can increase the ion energy up to 45 KeV to enhance the detection sensitivity. Recently, we succeeded in detecting a DNA segment with 500 nucleotides. The sensitivity was 100 femtomole. Thus, we have fulfilled two key criteria for using mass spectrometry for fast DNA sequencing. The major effort in the near future is to improve the resolution. Different approaches are being pursued. When high resolution of mass spectrometry can be achieved and automation of sample preparation is developed, the sequencing speed to reach 500 megabases per year can be feasible.

  4. System and method of infrared matrix-assisted laser desorption/ionization mass spectrometry in polyacrylamide gels

    DOEpatents

    Haglund, Jr., Richard F.; Ermer, David R.; Baltz-Knorr, Michelle Lee

    2004-11-30

    A system and method for desorption and ionization of analytes in an ablation medium. In one embodiment, the method includes the steps of preparing a sample having analytes in a medium including at least one component, freezing the sample at a sufficiently low temperature so that at least part of the sample has a phase transition, and irradiating the frozen sample with short-pulse radiation to cause medium ablation and desorption and ionization of the analytes. The method further includes the steps of selecting a resonant vibrational mode of at least one component of the medium and selecting an energy source tuned to emit radiation substantially at the wavelength of the selected resonant vibrational mode. The medium is an electrophoresis medium having polyacrylamide. In one embodiment, the energy source is a laser, where the laser can be a free electron laser tunable to generate short-pulse radiation. Alternatively, the laser can be a solid state laser tunable to generate short-pulse radiation. The laser can emit light at various ranges of wavelength.

  5. Evaluation of solid-phase microextraction desorption parameters for fast GC analysis of cocaine in coca leaves.

    PubMed

    Ilias, Yara; Bieri, Stefan; Christen, Philippe; Veuthey, Jean-Luc

    2006-08-01

    By its simplicity and rapidity, solid-phase microextraction (SPME) appears as an interesting alternative for sample introduction in fast gas chromatography (fast GC). This combination depends on numerous parameters affecting the desorption step (i.e., the release of compounds from the SPME fiber coating to the GC column). In this study, different liner diameters, injection temperatures, and gas flow rates are evaluated to accelerate the thermal desorption process in the injection port. This process is followed with real-time direct coupling a split/splitless injector to a mass spectrometer by means of a short capillary. It is shown that an effective, quantitative, and rapid transfer of cocaine (COC) and cocaethylene (CE) is performed with a 0.75-mm i.d. liner, at 280 degrees C and 4 mL/min gas flow rate. The 7-microm polydimethylsiloxane (PDMS) coating is selected for combination with fast GC because the 100-microm PDMS fiber presents some limitations caused by fiber bleeding. Finally, the developed SPME-fast GC method is applied to perform in less than 5 min, the quantitation of COC extracted from coca leaves by focused microwave-assisted extraction. An amount of 7.6 +/- 0.5 mg of COC per gram of dry mass is found, which is in good agreement with previously published results. PMID:16925937

  6. Direct Detection of a Sulfonate Ester Genotoxic Impurity by Atmospheric-Pressure Thermal Desorption–Extractive Electrospray–Mass Spectrometry

    PubMed Central

    2013-01-01

    A direct, ambient ionization method has been developed using atmospheric pressure thermal desorption–extractive electrospray–mass spectrometry (AP/TD-EESI-MS) for the detection of the genotoxic impurity (GTI) methyl p-toluenesulfonate (MTS) in a surrogate pharmaceutical matrix. A custom-made thermal desorption probe was used to the desorb and vaporize MTS from the solid state, by rapid heating to 200 °C then cooling to ambient temperature, with a cycle time of 6 min. The detection of MTS using EESI with a sodium acetate doped solvent to generate the [MTS+Na]+ adduct ion provided a significant sensitivity enhancement relative to the [M+H]+ ion generated using a 0.1% formic acid solvent modifier. The MTS detection limit is over an order of magnitude below the long-term daily threshold of toxicological concern (TTC) of 1.5 ?g/g and the potential for quantitative analysis has been determined using starch as a surrogate active pharmaceutical ingredient (API). PMID:23750985

  7. Kinetics of Uranium(VI) Desorption from Contaminated Sediments: Effect of Geochemical Conditions and Model Evaluation

    SciTech Connect

    Liu, Chongxuan; Shi, Zhenqing; Zachara, John M.

    2009-09-01

    Stirred-flow cell experiments were performed to investigate the kinetics of uranyl [U(VI)] desorption from a contaminated sediment collected from the Hanford 300 Area at the US Department of Energy (DOE) Hanford Site, Washington. Three influent solutions of variable pH, Ca and carbonate concentrations that affected U(VI) aqueous and surface speciation were used under dynamic flow conditions to evaluate the effect of geochemical conditions on the rate of U(VI) desorption. The measured rate of U(VI) desorption varied with solution chemical composition that evolved as a result of thermodynamic and kinetic interactions between the influent solutions and sediment. The solution chemical composition that led to a lower equilibrium U(VI) sorption to the solid phase yielded a faster desorption rate. The experimental results were used to evaluate a multi-rate, surface complexation model (SCM) that has been proposed to describe U(VI) desorption kinetics in the Hanford sediment that contained complex sorbed U(VI) species in mass transfer limited domains. The model was modified and supplemented by including multi-rate, ion exchange reactions to describe the geochemical interactions between the solutions and sediment. With the same set of model parameters, the modified model reasonably well described the evolution of major ions and the rates of U(VI) desorption under variable geochemical and flow conditions, implying that the multi-rate SCM is an effective way to describe U(VI) desorption kinetics in subsurface sediments.

  8. Long-term kinetics of uranyl desorption from sediments under advective conditions

    NASA Astrophysics Data System (ADS)

    Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John

    2014-02-01

    Long-term (>4 months) column experiments were performed to investigate the kinetics of uranyl (U(VI)) desorption in sediments collected from the Integrated Field Research Challenge site at the U.S. Department of Energy Hanford 300 Area. The experimental results were used to evaluate alternative multirate surface complexation reaction (MRSCR) approaches to describe the short and long-term kinetics of U(VI) desorption under flow conditions. The surface complexation reaction (SCR) stoichiometry and equilibrium constants and multirate parameters in the MRSCR models were independently characterized in batch and stirred flow-cell reactors. MRSCR models that were either additively constructed using the MRSCRs for individual size fractions, or composite in nature, could effectively describe short-term U(VI) desorption under flow conditions. The long-term desorption results, however, revealed that using the labile U concentration measured by carbonate extraction underestimated desorbable U(VI) and the long-term rate of U(VI) desorption. This study also found that the gravel size fraction (2-8 mm), which is typically treated as nonreactive in modeling U(VI) reactive transport because of low external surface area, can have an important effect on the U(VI) desorption in the sediment. This study demonstrates an approach to effectively extrapolate U(VI) desorption kinetics for field-scale application and identifies important parameters and uncertainties affecting model predictions.

  9. A new technique for Auger analysis of surface species subject to electron-induced desorption

    NASA Technical Reports Server (NTRS)

    Pepper, S. V.

    1973-01-01

    A method is presented to observe surface species subject to electron-induced desorption by Auger electron spectroscopy. The surface to be examined is moved under the electron beam at constant velocity, establishing a time independent condition and eliminating the time response of the electron spectrometer as a limiting factor. The dependence of the Auger signal on the surface velocity, incident electron current, beam diameter, and desorption cross section are analyzed. The method is illustrated by the Auger analysis of PTFE, in which the fluorine is removed by electron induced desorption.

  10. Work function and gas desorption studies during turn-on of various shelf-stored cathodes

    NASA Astrophysics Data System (ADS)

    Shih, A.; Haas, G. A.; Jensen, J. T.; Hor, C.

    A comparative study has been made of the oxide-type coated powder cathode (CPC), and impregnated types B, M, tungstate and scandate cathodes in their ability to rapidly turn on after extended periods of shelf life. Particular performance objectives were to attain pulsed emission levels in the 4-5 A/cm 2 region within a few seconds after shelf lives corresponding up to several years. Preliminary surface studies indicate that all cathodes significantly poison within a few hours or days after being shut down in a typical sealed-off tube environment. Therefore, apart from bringing the cathode up to thermionic emission temperature, the kinetics of the turn-on step must also involve the kinetics of reactivation. Comparative data are presented of the work function variation with reactivation temperature for the various cathodes, thus showing the degree of poisoning, the thermal reactivation characteristics and the work function-temperature relationship in their respective active states. The results show that in the active state, the CPC has the highest emission, the M and scandate impregnated cathodes are somewhat lower in emission, i.e. ˜50 K higher temperature for the same emission, while the type-B impregnated cathode requires ˜100 K more. The shelf-life poisoning among the impregnated cathodes, on the other hand, was greatest for the M cathodes, a bit less for the scandate and least for the type B. For typical fast turn-on reactivation schedules, the CPC reactivated below its normal operating temperature of ˜1250 K but all impregnated cathodes required activation temperatures of ˜1500 K and above (i.e., about 200 K above their operating temperatures). Studies were also made on the pick-up and desorption of various gases present in the shelf-life vacuum ambient. The data demonstrated a direct correlation between the chemical reactivity that the different cathodes had with the residual ambient gases and the corresponding extent to which these cathodes poisoned during shelf life. While a study of the shelf-life poisoning and reactivation mechanisms for the impregnated-type cathodes is still in progress, initial results have been completed for the oxide-type cathodes and these are presented elsewhere in this issue.

  11. Gas-cooled reactor programs. High-temperature gas-cooled reactor technology development program. Annual progress report, December 31, 1983

    Microsoft Academic Search

    P. R. Kasten; P. L. Rittenhouse; D. E. Bartine; J. P. Sanders

    1984-01-01

    ORNL continues to make significant contributions to the national program. In the HTR fuels area, we are providing detailed statistical information on the fission product retention performance of irradiated fuel. Our studies are also providing basic data on the mechanical, physical, and chemical behavior of HTR materials, including metals, ceramics, graphite, and concrete. The ORNL has an important role in

  12. Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

    SciTech Connect

    Paardekooper, D. M., E-mail: dmpaardekooper@strw.leidenuniv.nl; Bossa, J.-B.; Isokoski, K.; Linnartz, H., E-mail: linnartz@strw.leidenuniv.nl [Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden (Netherlands)

    2014-10-01

    A new ultra-high vacuum experiment is described that allows studying photo-induced chemical processes in interstellar ice analogues. MATRI²CES - a Mass Analytical Tool to study Reactions in Interstellar ICES applies a new concept by combining laser desorption and time-of-flight mass spectrometry with the ultimate goal to characterize in situ and in real time the solid state evolution of organic compounds upon UV photolysis for astronomically relevant ice mixtures and temperatures. The performance of the experimental setup is demonstrated by the kinetic analysis of the different photoproducts of pure methane (CH?) ice at 20 K. A quantitative approach provides formation yields of several new species with up to four carbon atoms. Convincing evidence is found for the formation of even larger species. Typical mass resolutions obtained range from M/?M ~320 to ~400 for CH? and argon, respectively. Additional tests show that the typical detection limit (in monolayers) is ?0.02 ML, substantially more sensitive than the regular techniques used to investigate chemical processes in interstellar ices.

  13. Effect of nanopore size distributions on trichloroethylene adsorption and desorption on carbogenic adsorbents

    SciTech Connect

    Kane, M.S.; Bushong, J.H.; Foley, H.C. [Univ. of Delaware, Newark, DE (United States)] [Univ. of Delaware, Newark, DE (United States); Brendley, W.H. Jr. [Philadelphia Coll. of Textiles, Philadelphia, PA (United States). Dept. of Chemistry] [Philadelphia Coll. of Textiles, Philadelphia, PA (United States). Dept. of Chemistry

    1998-06-01

    Two carbon adsorbents, Ambersorb-600 and Ambersorb-563 (A-600 and A-563), were compared for vapor-phase trichloroethylene (TCE) adsorption from humid air streams. These adsorbents retained capacity for TCE in humid environments and were regenerable in situ. Enhanced desorption, and hence, increased working capacities, were achieved with bimodal pore size distributions and hydrophobic surface chemistry. Vapor-phase TCE isotherms confirmed that both of these adsorbents have high capacities for TCE. Only a small difference between the micropore size distributions of A-563 and A-600 was determined by room-temperature methyl chloride adsorption and the modified Horvath-Kawazoe model. Besides differences in particle size and pore volume there was a measurable, but small change, in the fraction of the pores in the ultramicropore range (5 {angstrom} or smaller) of the A-600 adsorbent versus that of A-563. In packed-bed breakthrough curve experiments, A-600 displayed a sharper mass-transfer zone than A-563, but maintained essentially the same capacity for TCE in a humid environment. Both materials were amenable to in-situ regeneration, and the A-600 provided higher overall working capacity than that of A-563.

  14. Equipment for hydrogen absorption-desorption cycling characterization of hydride forming materials.

    PubMed

    Meyer, G; Arneodo Larochette, P; Baruj, A; Castro, F J; Lacharmoise, P; Zacur, E; Talagañis, B A

    2007-02-01

    Hydrogen storage materials suffer different degradation processes when they are cycled, forming and decomposing their associated hydride phases. In order to study these processes, we have designed and built an automated apparatus specifically developed for cycling samples of hydride forming materials by changing the external hydrogen pressure. Instead of the standard open configuration involving a high-pressure, high-quality gas bottle and a vacuum pump, the equipment uses another hydride forming material (in our case LaNi5) as a source and sink of hydrogen. The resulting closed-loop configuration eliminates hydrogen waste and ensures that extremely high purity gas is used during the whole experiment, thanks to the purifying properties of the selected hydride as source/sink. Hydrogen pressure is set by changing the source/sink temperature. Cycles can be performed as fast as one cycle every 5 min, a period comparable with typical good hydride forming material kinetics. An example of application of the apparatus is given for 1000 absorption/ desorption cycles on a Mm0.8Ca0.2Ni5 sample. PMID:17578119

  15. Combined Atomic Force Microscope-Based Topographical Imaging and Nanometer Scale Resolved Proximal Probe Thermal Desorption/Electrospray Ionization-Mass Spectrometry

    SciTech Connect

    Ovchinnikova, Olga S [ORNL; Nikiforov, Maxim [ORNL; Bradshaw, James A [ORNL; Jesse, Stephen [ORNL; Van Berkel, Gary J [ORNL

    2011-01-01

    Nanometer scale proximal probe thermal desorption/electrospray ionization mass spectrometry (TD/ESI-MS) was demonstrated for molecular surface sampling of caffeine from a thin film using a 30 nm diameter nano-thermal analysis (nano-TA) probe tip in an atomic force microscope (AFM) coupled via a vapor transfer line and ESI interface to a MS detection platform. Using a probe temperature of 350 C and a spot sampling time of 30 s, conical desorption craters 250 nm in diameter and 100 nm deep were created as shown through subsequent topographical imaging of the surface within the same system. Automated sampling of a 5 x 2 array of spots, with 2 m spacing between spots, and real time selective detection of the desorbed caffeine using tandem mass spectrometry was also demonstrated. Estimated from the crater volume (~2x106 nm3), only about 10 amol (2 fg) of caffeine was liberated from each thermal desorption crater in the thin film. These results illustrate a relatively simple experimental setup and means to acquire in automated fashion sub-micrometer scale spatial sampling resolution and mass spectral detection of materials amenable to TD. The ability to achieve MS-based chemical imaging with 250 nm scale spatial resolution with this system is anticipated.

  16. Methods for Processing and Summarizing Time-Series Temperature Data Collected as Part of the National Water-Quality Assessment Program Studies on the Effects of Urbanization on Stream Ecosystems

    USGS Publications Warehouse

    Cuffney, Thomas F.; Brightbill, Robin A.

    2008-01-01

    Temperature data and summary statistics are presented for 256 sites in 9 metropolitan areas as part of the U.S. Geological Survey National Water-Quality Assessment Program studies of the effects of urbanization on stream ecosystems. The computer program (GRAN) that was developed to derive uniform data granularity and calculate temperature statistics (means, standard deviations, rates of change, degree days) is described, as are the methods used to estimate missing daily mean temperatures, degree days (annual and summer periods), and 7-day running averages of daily mean temperatures.

  17. Shape evolution of new-phased lepidocrocite VOOH from single-shelled to double-shelled hollow nanospheres on the basis of programmed reaction-temperature strategy.

    PubMed

    Wu, Changzheng; Zhang, Xiaodong; Ning, Bo; Yang, Jinlong; Xie, Yi

    2009-07-01

    Solid templates have been long regarded as one of the most promising ways to achieve single-shelled hollow nanostructures; however, few effective methods for the construction of multishelled hollow objects from their solid template counterparts have been developed. We report here, for the first time, a novel and convenient route to synthesizing double-shelled hollow spheres from the solid templates via programming the reaction-temperature procedures. The programmed temperature strategy developed in this work then provides an essential and general access to multishelled hollow nanostructures based on the designed extension of single-shelled hollow objects, independent of their outside contours, such as tubes, hollow spheres, and cubes. Starting from the V(OH)(2)NH(2) solid templates, we show that the relationship between the hollowing rate and the reaction temperature obey the Van't Hoff rule and Arrhenius activation-energy equation, revealing that it is the chemical reaction rather than the diffusion process that guided the whole hollowing process, despite the fact that the coupled reaction/diffusion process is involved in the hollowing process. Using the double-shelled hollow spheres as the PCM (CaCl(2).6H(2)O) matrix grants much better thermal-storage stability than that for the nanoparticles counterpart, revealing that the designed nanostructures can give rise to significant improvements for the energy-saving performance in future "smart house" systems. PMID:19469496

  18. Adsorption-desorption characteristics of cadmium in variable charge soils.

    PubMed

    He, Zhen-Li; Xu, Hai-Ping; Zhu, Ying-Mei; Yang, Xiao-E; Chen, Guo-Chao

    2005-01-01

    Cadmium (Cd) has received considerable attention because of its association with various human health problems. The behavior of adsorption-desorption of Cd at contaminated levels in two variable charge soils were investigated. The red soil (RAR) developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) adsorbed more Cd2+ than the red soil (REQ) derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult). The characteristics of Cd adsorption could be described by the Freundlich equation (r2 = 0.997 and 0.989, respectively, for the RAR and REQ) and the simple Langmuir adsorption equation (r2 = 0.985 and 0.977, respectively, for the RAR and REQ). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 36.23 mmol Cd2+ kg(-1) soil and 31.15 mmol Cd2+ kg(-1) soil, respectively for the RAR and REQ. Adsorption of Cd2+ decreased soil pH by 1.28 unit for the RAR soil and 1.23 unit for the REQ soil at the highest loading. The distribution coefficient (kd) of Cd in the soil decreased exponentially with increasing Cd2+ loading. The adsorption of cadmium in the two variable charge soils was characterized by a rapid process that lasted approximately 15 min, followed by a slower but longer period. 85.5% and 79.4% of the added Cd were adsorbed within two hours by the RAR and REQ soil, respectively. More Cd2+ was adsorbed at 10 degrees C than at 25 degrees C or 40 degrees C. After five successive desorptions with 0.01 mol L(-1) NaNO3 solution, 53.3% of the total adsorbed Cd2+ in the RAR soil was desorbed and the corresponding value of the REQ soil was 46.5%, indicating that the RAR soil had a lower affinity for Cd2+ than the REQ soil at the same Cd2+ loading. PMID:15792301

  19. Regeneration of field-spent activated carbon catalysts for low-temperature selective catalytic reduction of NOx with NH3

    SciTech Connect

    Jeon, Jong Ki; Kim, Hyeonjoo; Park, Young-Kwon; Peden, Charles HF; Kim, Do Heui

    2011-10-15

    In the process of producing liquid crystal displays (LCD), the emitted NOx is removed over an activated carbon catalyst by using selective catalytic reduction (SCR) with NH3 at low temperature. However, the catalyst rapidly deactivates primarily due to the deposition of boron discharged from the process onto the catalyst. Therefore, this study is aimed at developing an optimal regeneration process to remove boron from field-spent carbon catalysts. The spent carbon catalysts were regenerated by washing with a surfactant followed by drying and calcination. The physicochemical properties before and after the regeneration were investigated by using elemental analysis, TG/DTG (thermogravimetric/differential thermogravimetric) analysis, N2 adsorption-desorption and NH3 TPD (temperature programmed desorption). Spent carbon catalysts demonstrated a drastic decrease in DeNOx activity mainly due to heavy deposition of boron. Boron was accumulated to depths of about 50 {mu}m inside the granule surface of the activated carbons, as evidenced by cross-sectional SEM-EDX analysis. However, catalyst activity and surface area were significantly recovered by removing boron in the regeneration process, and the highest NOx conversions were obtained after washing with a non-ionic surfactant in H2O at 70 C, followed by treatment with N2 at 550 C.

  20. DESORPTION KINETICS OF NEUTRAL HYDROPHOBIC ORGANIC COMPOUNDS FROM FIELD CONTAMINATED SEDIMENT. (R825513C024)

    EPA Science Inventory

    The chemical release rates from a field-contaminated sediment (Lake Charles, LA) using Tenax desorption were studied. Two dichlorobenzenes ( m -, p -), hexachlorobutadiene, and hexachlorobenzene were investigated. Contrary to reports that sorption rates are inversel...

  1. Numerical simulation of impurity desorption induced by nanosecond and femtosecond laser pulses

    SciTech Connect

    Chi Yinsheng; Lin Xiaohui; Chen Minhua; Chen Yunfei [Department of Mechanical Engineering, Southeast University, Nanjing 210096 (China); Key Laboratory of MEMS of China Educational Ministry, Southeast University, Nanjing 210096 (China)

    2006-08-01

    A model based on a stochastic process was developed to study the impurity molecule desorption from a substrate induced by nanosecond and femtosecond lasers. The dynamics of adsorbed molecules irradiated by the laser pulses can be considered to be a Brownian motion in the bath of excited energy carriers. A two-step model was used to describe the nonequilibrium heating process induced by the femtosecond laser pulses. The difference between the desorption processes induced by nanosecond and femtosecond lasers was discussed based on the numerical results for the desorption of CO molecules from a Ru surface. Results indicate that the femtosecond laser is a much better tool for desorption than the nanosecond laser.

  2. EFFECTS OF BIOSOLIDS ON SORPTION AND DESORPTION BEHAVIOR OF CADMIUM IN BIOSOLIDS-AMENDED SOILS

    EPA Science Inventory

    Cadmium sorption and desorption experiments were conducted on different fractions of soils amended with different biosolids with varying chemical properties and unamended soil (control). Biosolids addition increased the slope of the Cd sorption isotherms compared to the control s...

  3. CHARACTERIZATION OF CRYPTOSPORIDIUM PARVUM BY MATRIX-ASSISTED LASER DESORPTION -- IONIZATION TIME OF FLIGHT MASS SPECTROMETRY

    EPA Science Inventory

    Matrix assisted laser desorption/ionization (MALDI) mass spectrometry was used to investigate whole and freeze thawed Cryptosporidium parvum oocysts. Whole oocysts revealed some mass spectral features. Reproducible patterns of spectral markers and increased sensitivity were obtai...

  4. Roles of Electron and Photon Induced Desorption in the Formation of Mercury's Exosphere

    NASA Astrophysics Data System (ADS)

    McLain, J.; Grieves, G.; Sprague, A.; Schriver, D.; Travinicek, P.; Orlando, T.

    2011-10-01

    Mercury is surrounded by an exosphere whose properties are determined primarily by its interaction with the surface and the space environment seen by both ground- and space-based observation.[1, 4, 6] The primary processes thought to be governing the ejection of materials into the exosphere are high energy ion sputtering, thermal desorption, micrometeorite impact and non-thermal desorption. When photons or electrons are involved, these nonthermal processes are usually referred to as photon stimulated desorption (PSD) or electron-stimulated desorption (ESD), respectively.[2, 3] These radiolytic and space weathering processes (i.e., ion sputtering, PSD and ESD) are of general importance, not only for Mercury but for other airless bodies, such as moons and asteroids, that interact with solar wind and magnetospheric plasmas. Laboratory measurements are being performed to determine the efficiency of these non-thermal processes in removing ionic and neutral species from minerals likely to be present on Mercury's surface.

  5. In-injection port thermal desorption for explosives trace evidence analysis.

    PubMed

    Sigman, M E; Ma, C Y

    1999-10-01

    A gas chromatographic method utilizing thermal desorption of a dry surface wipe for the analysis of explosives trace chemical evidence has been developed and validated using electron capture and negative ion chemical ionization mass spectrometric detection. Thermal desorption was performed within a split/splitless injection port with minimal instrument modification. Surface-abraded Teflon tubing provided the solid support for sample collection and desorption. Performance was characterized by desorption efficiency, reproducibility, linearity of the calibration, and method detection and quantitation limits. Method validation was performed with a series of dinitrotoluenes, trinitrotoluene, two nitroester explosives, and one nitramine explosive. The method was applied to the sampling of a single piece of debris from an explosion containing trinitrotoluene. PMID:21662844

  6. Simulation of heavy ion induced desorption of biomolecules from surfaces using the popcorn model

    NASA Astrophysics Data System (ADS)

    Lee, Shyi-Long; Lucchese, Robert R.

    1988-01-01

    Trajectory calculations have been performed to study the validity of the recently proposed popcorn model of Williams and Sundqvist [Phys. Rev. Letters 58 (1987) 1031] for the heavy ion induced desorption of biomolecules from surfaces. The adsorbed biomolecule is assumed to be vibrationally excited by the flux of low energy secondary electrons created by the passage of the primary ion through the solid. The post-excitation vibrational motions of the peptide units in the biomolecule are followed with classical trajectories using a one-dimensional chain containing 40 coupled anharmonic oscillators as a model for the biomolecule desorption system. The expansion of the biomolecule due to the excitation of the anharmonic bonds leads to desorption in a fashion analogous to an exploding kernel of popcorn. This popcorn mechanism is found to lead to a factor of three enhancement of the desorption probability over a model of the biomolecule which contains only harmonic internal bonds.

  7. Effects of Material Moisture Adsorption and Desorption on Building Cooling Loads

    E-print Network

    Fairey, P.; Kosar, D.

    1988-01-01

    Moisture adsorption and desorption (MAD) by internal building materials and furnishings can be significant in buildings. For many building cooling strategies, MAD may have overriding effects on building cooling loads. For example, natural...

  8. A postsource decay study of bradykinin by Matrix-assisted laser desorption ionization mass spectrometry

    E-print Network

    Wei, Xiaona

    1996-01-01

    Subject: Chemistry ABSTRACT A Postsource Decay Study of Bradykinin by Matrix-assisted Laser Desorption Ionization Mass Spectrometry. ( August 1996) Xiaona Wei, B. S. , Tsinghua University; M. S. , Academic Sinica of China Chair of Advisory Committee...

  9. Charging effects on electron-stimulated desorption of cations from gadolinia-doped ceria surfaces

    Microsoft Academic Search

    Haiyan Chen; Yanfeng Chen; Alex Aleksandrov; Jian Dong; Meilin Liu; Thomas M. Orlando

    2005-01-01

    Electron beam-induced charging and -stimulated desorption have been used to probe the electronic properties of gadolinia-doped ceria (GDC) surfaces. The main cationic desorption products resulting from electron bombardment are H+, H3O+ and O+. The dependence of the H+ and H3O+ ion kinetic energies and yields on the surface potentials have been systematically investigated. Positive potentials increase the cation kinetic energies

  10. Cross sections for x-ray photoelectron-induced desorption of hydrogen ions from metal surfaces

    SciTech Connect

    Kinney, J.H.; Siekhaus, W.J.; Anderson, R.A.

    1985-09-20

    We have measured the cross sections for x-ray photoelectron-induced desorption of hydrogen ions from beryllium, carbon, aluminum, tantalum, and gold surfaces. This report describes the results of the cross-section measurements, and discusses a time-of-flight technique that allows the determination of ionic-desorption cross sections as small as 10/sup -25/ cm/sup 2/ per photoelectron. 19 refs., 7 figs.

  11. The effect of solvent on matrix-assisted laser desorption ionization mass spectrometry 

    E-print Network

    Campo, Karen Kay

    1996-01-01

    THE EFFECT OF SOLVENT ON MATRIX-ASSISTED LASER DESORPTION IONIZATION MASS SPECTROMETRY A Thesis by KAREN KAY CAMPO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1996 Major Subject: Chemistry THE EFFECT OF SOLVENT ON MATRIX-ASSISTED LASER DESORPTION IONIZATION MASS SPECTROMETRY A Thesis by KAREN KAY CAMPO Submitted to Texas A@M University in partial fulfillment...

  12. Gold nanomaterials as a new tool for bioanalytical applications of laser desorption ionization mass spectrometry

    Microsoft Academic Search

    Rosa Pilolli; Francesco Palmisano; Nicola Cioffi

    Nanomaterials have emerging importance in laser desorption ionization mass spectrometry (LDI–MS) with the ultimate objective\\u000a being to overcome some of the most important limitations intrinsically related to the use of conventional organic matrices\\u000a in matrix-assisted (MA) LDI–MS. This review provides a critical overview of the most recent literature on the use of gold\\u000a nanomaterials as non-conventional desorption ionization promoters in

  13. Effect of soil and sediment composition on acetochlor sorption and desorption

    Microsoft Academic Search

    Edgar Hiller; Slavomír ?er?anský; Zoltán Krascsenits; Ján Mili?ka

    2009-01-01

    Background, aim, and scope  Herbicide fate and its transport in soils and sediments greatly depend upon sorption–desorption processes. Quantitative determination\\u000a of herbicide sorption–desorption is therefore essential for both the understanding of transport and the sorption equilibrium\\u000a in the soil\\/sediment–water system; and it is also an important parameter for predicting herbicide fate using mathematical\\u000a simulation models. The total soil\\/sediment organic carbon content

  14. Pulsed light desorption of molecular nitrogen from a glass surface

    NASA Astrophysics Data System (ADS)

    Atutov, S. N.; Danilina, N. A.; Mikerin, S. L.; Plekhanov, A. I.

    2014-03-01

    Experimental results on the pulsed light desorption (PLD) of molecular Nitrogen from the surface of C-52 and Pyrex glasses are presented. The aim of the study was to determine the experimental conditions to obtain the maximum manifestation of the PLD effect of molecular gases. These studies were conducted in vacuum glass cells of different sizes and shapes filled by Nitrogen, whose inner surface was illuminated by the light of a powerful flash lamp. The variation in the density of the desorbed gas in the cell caused by PLD was studied using both a mass spectrometer and a vacuum gauge attached to the illuminated cells. The experimental results are in qualitative agreement with the theoretical model developed. We demonstrates that PLD can drastically increase a peak density of desorbed Nitrogen in a cell and the maximal Nitrogen density can be achieved in a small diameter long cell of cylindrical form. We believe that the results of this experiment can be applied to the loading of some gases inside a hollow-core, photonic band-gap fiber to generate a large optical depth for an experiment in low-light-level nonlinear optics.

  15. A combined whelk watch suggests repeated TBT desorption pulses.

    PubMed

    Ruiz, J M; Albaina, N; Carro, B; Barreiro, R

    2015-01-01

    Environmental quality in coastal Europe has improved since the complete 2003 ban on the use of tributyltin (TBT) in antifouling paints. However, there is evidence that TBT is entering the water column, presumably from illegal practices. We determined the concentration of butyltins (BTs: TBT and derivatives) in populations of two gastropods, the rock snail Nucella lapillus (n=17) and the mud snail Nassarius reticulatus (n=18) at regular intervals from pre-ban times until 2009 and 2011, respectively, in NW Spain. Although a substantial decline in TBT occurred shortly after the ban, no significant changes were observed in either species over the last 3-year period of study. In addition, the proportion of TBT relative to the sum of BTs (a marker of recent pollution) in the most recent rock snail samples unexpectedly increased; this proportion therefore showed a generally decreasing but oscillatory trend over time. The results are consistent with the theoretical expectation of BT desorption from sediments; however, this natural phenomenon is now interpreted as a recurrent episode rather than a unique, transient event. Evidence of this subtle input improves our understanding of TBT persistence in the environment in Europe and worldwide. PMID:25260162

  16. Laser desorption mass spectrometry for point mutation detection

    SciTech Connect

    Taranenko, N.I.; Chung, C.N.; Zhu, Y.F. [Oak Ridge National Lab., TN (United States)] [and others] [Oak Ridge National Lab., TN (United States); and others

    1996-10-01

    A point mutation can be associated with the pathogenesis of inherited or acquired diseases. Laser desorption mass spectrometry coupled with allele specific polymerase chain reaction (PCR) was first used for point mutation detection. G551D is one of several mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene present in 1-3% of the mutant CFTR alleles in most European populations. In this work, two different approaches were pursued to detect G551D point mutation in the cystic fibrosis gene. The strategy is to amplify the desired region of DNA template by PCR using two primers that overlap one base at the site of the point mutation and which vary in size. If the two primers based on the normal sequence match the target DNA sequence, a normal PCR product will be produced. However, if the alternately sized primers that match the mutant sequence recognize the target DNA, an abnormal PCR product will be produced. Thus, the mass spectrometer can be used to identify patients that are homozygous normal, heterozygous for a mutation or homozygous abnormal at a mutation site. Another approach to identify similar mutations is the use of sequence specific restriction enzymes which respond to changes in the DNA sequence. Mass spectrometry is used to detect the length of the restriction fragments generated by digestion of a PCR generated target fragment. 21 refs., 10 figs., 2 tabs.

  17. Laser desorption mass spectrometry for point mutation detection

    SciTech Connect

    Taranenko, N.I.; Chung, C.N.; Zhu, Y.F. [Oak Ridge National Lab., TN (United States)] [and others

    1996-12-31

    A point mutation can be associated with the pathogenesis of inherited or acquired diseases. Laser desorption mass spectrometry coupled with allele specific polymerase chain reaction (PCR) was first used for point mutation detection. G551D is one of several mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene present in 1-3% of the mutant CFTR alleles in most European populations. In this work, two different approaches were pursued to detect G551D point mutation in the cystic fibrosis gene. The strategy is to amplify the desired region of DNA template by PCR using two primers that overlap one base at the site of the point mutation and which vary in size. If the two primers based on the normal sequence match the target DNA sequence, a normal PCR product will be produced. However, if the alternately sized primers that match the mutant sequence recognize the target DNA, an abnormal PCR product will be produced. Thus, the mass spectrometer can be used to identify patients that are homozygous normal, heterozygous for a mutation or homozygous abnormal at a mutation site. Another approach to identify similar mutations is the use of sequence specific restriction enzymes which respond to changes in the DNA sequence. Mass spectrometry is used to detect the length of the restriction fragments by digestion of a PCR generated target fragment. 21 refs., 10 figs., 2 tabs.

  18. NSLS vacuum system operating experience conditioning and desorption yields

    SciTech Connect

    Halama, H.J.

    1991-01-01

    All straight sections in both the VUV and the X-Ray rings have been filled with various insertion devices, most of them fully operational. Beam lifetime in the VUV ring is limited by the Touschek effect to {approximately}100 minutes at 800 mA due to the small vertical beam size required by users. With no experiments running, X-Ray beam lifetime is >35 hours at 220 mA and is limited by beam gas scattering. During the past several years the U10 beam line was used to measure PSD yields from various metals to study their relative merits for light sources. These yields were also compared to those measured in X-Ray ring dipoles during initial commissioning when desorption was high. Despite the large differences in critical photon energies, agreement was quite good. Both rings are now fully conditioned and their pressures and lifetimes have reached equilibrium. Well established conditioning procedures are followed after every intervention into their vacuum systems.

  19. Imaging of Biological Tissues by Desorption Electrospray Ionization Mass Spectrometry

    PubMed Central

    Fernández, Facundo M.

    2013-01-01

    Mass spectrometry imaging (MSI) provides untargeted molecular information with the highest specificity and spatial resolution for investigating biological tissues at the hundreds to tens of microns scale. When performed under ambient conditions, sample pre-treatment becomes unnecessary, thus simplifying the protocol while maintaining the high quality of information obtained. Desorption electrospray ionization (DESI) is a spray-based ambient MSI technique that allows for the direct sampling of surfaces in the open air, even in vivo. When used with a software-controlled sample stage, the sample is rastered underneath the DESI ionization probe, and through the time domain, m/z information is correlated with the chemical species' spatial distribution. The fidelity of the DESI-MSI output depends on the source orientation and positioning with respect to the sample surface and mass spectrometer inlet. Herein, we review how to prepare tissue sections for DESI imaging and additional experimental conditions that directly affect image quality. Specifically, we describe the protocol for the imaging of rat brain tissue sections by DESI-MSI. PMID:23892773

  20. Laser Desorption Postionization for Imaging MS of Biological Material

    PubMed Central

    Akhmetov, Artem; Moore, Jerry F.; Gasper, Gerald L.; Koin, Peter J.; Hanley, Luke

    2010-01-01

    Vacuum ultraviolet single photon ionization (VUV SPI) is a soft ionization technique that has the potential to address many of the limitations of MALDI for imaging MS. Laser desorption postionization (LDPI) employs VUV SPI for postionization and is experimentally analogous to a MALDI instrument with the addition of a pulsed VUV light source. This review discusses progress in LDPI-MS over the last decade, with an emphasis on imaging MS of bacterial biofilms, analytes whose high salt environment make them particularly resistant to imaging by MALDI-MS. This review first considers fundamental aspects of VUV SPI including ionization mechanisms, cross sections, quantum yields of ionization, dissociation, and potential mass limits. The most common sources of pulsed VUV radiation are then described along with a newly constructed LDPI-MS instrument with imaging capabilities. Next, the detection and imaging of small molecules within intact biofilms is demonstrated by LDPI-MS using 7.87 eV (157.6 nm) VUV photons from a molecular fluorine excimer laser, followed by the use of aromatic tags for detection of selected species within the biofilm. The final section considers the future prospects for imaging intact biological samples by LDPI-MS. PMID:20146224