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Sample records for temperature programmed desorption

  1. Temperature programmed desorption of weakly bound adsorbates on Au(111)

    NASA Astrophysics Data System (ADS)

    Engelhart, Daniel P.; Wagner, Roman J. V.; Meling, Artur; Wodtke, Alec M.; Schäfer, Tim

    2016-08-01

    We have performed temperature programmed desorption (TPD) experiments to analyze the desorption kinetics of Ar, Kr, Xe, C2H2, SF6, N2, NO and CO on Au(111). We report desorption activation energies (Edes), which are an excellent proxy for the binding energies. The derived binding energies scale with the polarizability of the molecules, consistent with the conclusion that the surface-adsorbate bonds arise due to dispersion forces. The reported results serve as a benchmark for theories of dispersion force interactions of molecules at metal surfaces.

  2. 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.; Ortiz-Villafuerte, J.

    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.

  3. 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.

  4. The oxidized soot surface: Theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments

    NASA Astrophysics Data System (ADS)

    Barco, Gianluca; Maranzana, Andrea; Ghigo, Giovanni; Causà, Mauro; Tonachini, Glauco

    2006-11-01

    The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially, the study is carried out on unimolecular fragmentation (extrusion, in some cases) processes producing HO, CO, or CO2, in model ketones, carboxylic acids, lactones, anhydrides, in one aldehyde, one peroxyacid, one hydroperoxide, one secondary alcohol, and one phenol. Then, a bimolecular process is considered for one of the carboxylic acids. Furthermore, some cooperative effect which can take place by involving two vicinal carboxylic groups (derived from anhydride hydrolysis) is investigated for other four bifunctionalized models. The comparison between the computed fragmentation (desorption) barriers for the assessed mechanisms and the temperature at which maxima occur in TPD spectra (for HO, CO, or CO2 desorption) offers a suggestion for the assignment of these maxima to specific functional groups, i.e., a key to the description of the oxidized surface. Notably, the computations suggest that (1) the desorption mode from a portion of a graphenic platelet functionalized by a carboxylic or lactone groups is significantly dependent from the chemical and geometric local environment. Consequently, we propose that (2) not all carboxylic groups go lost at the relatively low temperatures generally stated, and (3) lactone groups can be identified as producing not only CO2 but also CO.

  5. 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.

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

    DOEpatents

    Linker, Kevin L.; Bouchier, Frank A.; Theisen, Lisa; Arakaki, Lester H.

    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.

  7. Monte Carlo simulations of temperature-programmed and isothermal desorption from single-crystal surfaces

    SciTech Connect

    Lombardo, S.J. . Dept. of Chemical Engineering Lawrence Berkeley Lab., CA )

    1990-08-01

    The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

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

    SciTech Connect

    Brown, L. F.; Travis, B. 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.

  9. Effects of surface coordination on the temperature-programmed desorption of oxalate from goethite

    SciTech Connect

    Boily, Jean F.; Szanyi, Janos; Felmy, Andrew R.

    2007-11-15

    The temperature-programmed desorption (TPD) of weakly-bound, hydrogen-bonded and metal-bonded oxalate complexes at the goethite surface was investigated in the 300-900 K range with concerted Fourier Transform Infrared (FTIR) measurements (TPD-FTIR). These reactions took place with the concomitant dehydroxylation reaction of goethite to hematite and decarbonation of bulk-occluded carbonate. The measurements revealed three important stages of desorption. Stage I (300-440 K) corresponds to the desorption of weakly-and/or un-bound oxalate molecules in the goethite powder with a thermal decomposition reaction pathway characteristic of oxalic acid. Stage II (440-520 K) corresponds to a thermally-driven dehydration of hydrogen-bonded surface complexes, leading to a partial desorption via oxalic acid thermal decomposition pathways and to a partial conversion to metal-bonded surface complexes. This latter mechanism led to the increase in FTIR bands characteristic of these complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of the metal-bonded oxalate complex, proceeding through a 2 electron reduction pathway.

  10. Electron Radiation Effects on Diethylsilane Covered Si (100) Surfaces Studied by Temperature Programmed Desorption

    NASA Astrophysics Data System (ADS)

    Petrany, Peter; Young, Vashawn; Kimberlin, Kevin R.; Lozano, Jose; Craig, James H.; Wang, Paul W.

    2003-03-01

    Ethylated silicon or germanium containing molecules are promising candidates to fabricate hetero-junction atomic layer epitaxy SiGe devices. However, thermal processes to dissociate unwanted ligands from parent molecules after dosing are not suitable for low thermal budget fabrication processes. Preliminary results of the electron radiation induced dissociation and/or desorption of diethylsilane (DES) covered Si (100) surfaces are reported. DES molecules were dosed onto Si surfaces at 120 K and the thermally desorbed species with and without 600 eV electron radiation were investigated by temperature programmed desorption (TPD). Electron beam dissociation effects as well as electron induced state changes reflected in TPD spectra will be discussed for several different initial gas exposures at 120 K. * Corresponding author

  11. Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments.

    PubMed

    Tonks, James P; Galloway, Ewan C; King, Martin O; Kerherve, Gwilherm; Watts, John F

    2016-08-01

    A dual purpose mass spectrometer chamber capable of performing molecular beam scattering (MBS) and temperature programmed desorption (TPD) is detailed. Two simple features of this design allow it to perform these techniques. First, the diameter of entrance aperture to the mass spectrometer can be varied to maximize signal for TPD or to maximize angular resolution for MBS. Second, the mass spectrometer chamber can be radially translated so that it can be positioned close to the sample to maximize signal or far from the sample to maximize angular resolution. The performance of this system is described and compares well with systems designed for only one of these techniques.

  12. Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments

    NASA Astrophysics Data System (ADS)

    Tonks, James P.; Galloway, Ewan C.; King, Martin O.; Kerherve, Gwilherm; Watts, John F.

    2016-08-01

    A dual purpose mass spectrometer chamber capable of performing molecular beam scattering (MBS) and temperature programmed desorption (TPD) is detailed. Two simple features of this design allow it to perform these techniques. First, the diameter of entrance aperture to the mass spectrometer can be varied to maximize signal for TPD or to maximize angular resolution for MBS. Second, the mass spectrometer chamber can be radially translated so that it can be positioned close to the sample to maximize signal or far from the sample to maximize angular resolution. The performance of this system is described and compares well with systems designed for only one of these techniques.

  13. Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments.

    PubMed

    Tonks, James P; Galloway, Ewan C; King, Martin O; Kerherve, Gwilherm; Watts, John F

    2016-08-01

    A dual purpose mass spectrometer chamber capable of performing molecular beam scattering (MBS) and temperature programmed desorption (TPD) is detailed. Two simple features of this design allow it to perform these techniques. First, the diameter of entrance aperture to the mass spectrometer can be varied to maximize signal for TPD or to maximize angular resolution for MBS. Second, the mass spectrometer chamber can be radially translated so that it can be positioned close to the sample to maximize signal or far from the sample to maximize angular resolution. The performance of this system is described and compares well with systems designed for only one of these techniques. PMID:27587173

  14. 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

  15. H(2)O Outgassing Properties of Fumed and Precipitated Silica Particles by Temperature-Programmed Desorption.

    PubMed

    Dinh; Balooch; LeMay

    2000-10-15

    Temperature-programmed desorption was performed at temperatures up to 850 K on as-received fumed and precipitated silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 38-61 kJ/mol. However, the activation energies of desorption for chemisorbed water varied from approximately 80 to >247 kJ/mol for fumed silica, Cab-O-Sil-M-7D, and approximately 96 to 155 kJ/mol for precipitated silica, Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>126 kJ/mol) will not escape silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (80-109 kJ/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies <126 kJ/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1-0.4 wt% of water in silica-reinforced polysiloxane formulations containing approximately 21% Cab-O-Sil-M-7D and approximately 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that the adsorbed H(2)O and the Si-OH bonds on the silica surfaces are the major contributors to water outgassing from these types of silica-filled polymers. Copyright 2000 Academic Press.

  16. 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.

  17. Selective Concentration of Ultra-trace Acetone in the Air by Cryogenic Temperature Programmed Desorption (cryo-TPD).

    PubMed

    Suzuki, Taku T; Sakaguchi, Isao

    2016-01-01

    A gas analytical technique with compact size, low cost, sufficient sensitivity, and excellent reproducibility is required in many fields including exhaled breath analysis for medical monitoring. In the present study, we examined selective acetone concentration by quench condensation at cryogenic temperature followed by temperature programmed desorption (cryogenic temperature programmed desorption (cryo-TPD)) for possible applications to breath analysis for medical monitoring. The essence of cryo-TPD is rough mass selection by thermal desorption followed by quantification of certain species using mass spectrometry. The performance of cryo-TPD was investigated in the acetone concentration range below 1 × 10(-6) volume fraction (1 ppmv). It was found that acetone is selectively quench-condensed on a tungsten substrate at 50 K without the major components of air, such as N2 and O2. The concentrated acetone gas was obtained by the following thermal desorption at around 151 K. Under conditions of condensation for 1 min and pressure of 1 × 10(-2) Pa, the lowest limit of detection reached well below 10 × 10(-9) volume fraction (10 ppbv). The relationship between the cetone intensity of cryo-TPD and the acetone concentration in the gas was almost linear in the ppbv range. The separation of acetone and propanal using the fragmentation pattern, which have almost the identical molecular mass, was also demonstrated in the present study. PMID:27682397

  18. Kinetic Monte Carlo simulations of temperature programed desorption of O/Rh(111).

    PubMed

    Franz, T; Mittendorfer, F

    2010-05-21

    We present a kinetic Monte Carlo simulation based on ab initio calculations for the thermal desorption of oxygen from a Rh(111) surface. Several models have been used for the parametrization of the interaction between the adsorbed atoms. We find that models based on a parametrization with only pairwise interactions have a relatively large error in the predicted adsorption energies. This error can be significantly reduced by including three- and four-body interactions. In addition, we find that a significant amount of atoms adsorb in a second adsorption site - the hcp-hollow site - at an elevated temperature. Consequently, only a many-body multisite model of the oxygen interactions yields appropriate desorption spectra for the full coverage range, while more simple models only capture the correct shape in the low-coverage case. Our parametrization allows us to predict the adsorption energies of an arbitrary configuration of adsorbates with a mean average error of less than 6 meV/atom.

  19. Temperature-programmed desorption study of NO reactions on rutile TiO2(110)-1 × 1

    NASA Astrophysics Data System (ADS)

    Kim, Boseong; Dohnálek, Zdenek; Szanyi, János; Kay, Bruce D.; Kim, Yu Kwon

    2016-10-01

    Systematic temperature-programmed desorption (TPD) studies of NO adsorption and reactions on rutile TiO2(110)-1 × 1 surface reveal several distinct reaction channels in a temperature range of 50-500 K. NO readily reacts on TiO2(110) to form N2O, which desorbs between 50 and 200 K (LT N2O channels), which leaves the TiO2 surface populated with adsorbed oxygen atoms (Oa) as a by-product of N2O formation. In addition, we observe simultaneous desorption peaks of NO and N2O at 270 K (HT1 N2O) and 400 K (HT2 N2O), respectively, both of which are attributed to reaction-limited processes. No N-derived reaction product desorbs from TiO2(110) surface above 500 K or higher, while the surface may be populated with Oa's and oxidized products such as NO2 and NO3. The adsorbate-free TiO2 surface with oxygen vacancies can be regenerated by prolonged annealing at 850 K or higher. Detailed analysis of the three N2O desorption yields reveals that the surface species for the HT channels are likely to be various forms of NO dimers.

  20. Temperature-programmed desorption study of NO reactions on rutile TiO2(110)-1×1

    DOE PAGES

    Kim, Boseong; Dohnalek, Zdenek; Szanyi, Janos; Kay, Bruce D.; Kim, Yu Kwon

    2016-02-24

    In this study, systematic temperature-programmed desorption (TPD) studies of NO adsorption and reactions on rutile TiO2(110)-1 × 1 surface reveal several distinct reaction channels in a temperature range of 50–500 K. NO readily reacts on TiO2(110) to form N2O, which desorbs between 50 and 200 K (LT N2O channels), which leaves the TiO2 surface populated with adsorbed oxygen atoms (Oa) as a by-product of N2O formation. In addition, we observe simultaneous desorption peaks of NO and N2O at 270 K (HT1 N2O) and 400 K (HT2 N2O), respectively, both of which are attributed to reaction-limited processes. No N-derived reaction productmore » desorbs from TiO2(110) surface above 500 K or higher, while the surface may be populated with Oa's and oxidized products such as NO2 and NO3. The adsorbate-free TiO2 surface with oxygen vacancies can be regenerated by prolonged annealing at 850 K or higher. Detailed analysis of the three N2O desorption yields reveals that the surface species for the HT channels are likely to be various forms of NO dimers.« less

  1. Temperature Programmed Desorption of Quench-condensed Krypton and Acetone in Air; Selective Concentration of Ultra-trace Gas Components.

    PubMed

    Suzuki, Taku T; Sakaguchi, Isao

    2016-01-01

    Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD.

  2. Temperature Programmed Desorption of Quench-condensed Krypton and Acetone in Air; Selective Concentration of Ultra-trace Gas Components.

    PubMed

    Suzuki, Taku T; Sakaguchi, Isao

    2016-01-01

    Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD. PMID:27063719

  3. 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

    2014-07-25

    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.

  4. 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

  5. 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

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

    PubMed Central

    Groβ, 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

  7. Temperature-programmed desorption study of the selective oxidation of alcohols on silica-supported vanadium oxide.

    PubMed

    Feng, T; Vohs, J M

    2005-02-17

    The partial oxidation of methanol and ethanol on silica-supported vanadium oxide catalysts was studied using temperature-programmed desorption (TPD), Raman spectroscopy, and diffuse reflectance infrared spectroscopy (DRIFTS). Methanol TPD results for V2O5/SiO2 samples as a function of vanadia loading in conjunction with X-ray diffraction data and Raman spectra indicated that dispersed vanadia on silica agglomerates into vanadia crystallites during a CH3OH TPD experiment. For ethanol-dosed samples, agglomeration of the dispersed vanadia was less severe, and it was possible to measure the activation energy for the dehydrogenation of adsorbed ethoxides to produce CH3CHO. Assuming a preexponential factor of 10(13) s(-1), the activation energy for this reaction was estimated to be 132 kJ/mol. The results of this study further demonstrate that there is a relatively weak interaction between vanadia and silica and suggest that adsorbed methoxide species help facilitate agglomeration of dispersed vanadia. PMID:16851203

  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. UV-Raman spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption studies of model and bulk heterogeneous catalysts

    SciTech Connect

    Tewell, Craig R.

    2002-08-19

    X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (TPD) have been used to investigate the surface structure of model heterogeneous catalysts in ultra-high vacuum (UHV). UV-Raman spectroscopy has been used to probe the structure of bulk model catalysts in ambient and reaction conditions. The structural information obtained through UV-Raman spectroscopy has been correlated with both the UHV surface analysis and reaction results. The present day propylene and ethylene polymerization catalysts (Ziegler-Natta catalysts) are prepared by deposition of TiCl{sub 4} and a Al(Et){sub 3} co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl{sub 2} and ethanol. A model thin film catalyst is prepared by depositing metallic Mg on a Au foil in a UHV chamber in a background of TiCl{sub 4} in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl{sub 2} by TiCl{sub 4} resulting in a thin film of MgCl{sub 2}/TiCl{sub x}, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl{sub 2}/TiCl{sub x} on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to {approx}1 Torr of Al(Et){sub 3}.

  10. Thermal transformation of bioactive caffeic acid on fumed silica seen by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry and quantum chemical methods.

    PubMed

    Kulik, Tetiana V; Lipkovska, Natalia O; Barvinchenko, Valentyna M; Palyanytsya, Borys B; Kazakova, Olga A; Dudik, Olesia O; Menyhárd, Alfréd; László, Krisztina

    2016-05-15

    Thermochemical studies of hydroxycinnamic acid derivatives and their surface complexes are important for the pharmaceutical industry, medicine and for the development of technologies of heterogeneous biomass pyrolysis. In this study, structural and thermal transformations of caffeic acid complexes on silica surfaces were studied by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry (TPD MS) and quantum chemical methods. Two types of caffeic acid surface complexes are found to form through phenolic or carboxyl groups. The kinetic parameters of the chemical reactions of caffeic acid on silica surface are calculated. The mechanisms of thermal transformations of the caffeic chemisorbed surface complexes are proposed. Thermal decomposition of caffeic acid complex chemisorbed through grafted ester group proceeds via three parallel reactions, producing ketene, vinyl and acetylene derivatives of 1,2-dihydroxybenzene. Immobilization of phenolic acids on the silica surface improves greatly their thermal stability.

  11. Chemistry of L-proline on Pd(1 1 1): Temperature-programmed desorption and X-ray photoelectron spectroscopic study

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Wang, Yilin; Burkholder, Luke; Tysoe, W. T.

    2007-09-01

    The surface chemistry of proline is explored on Pd(1 1 1) using a combination of temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy. Proline adsorbs on Pd(1 1 1) at temperatures of 250 K and below into second and subsequent layers prior to the saturation of the first layer, where approximately 70% of the adsorbed proline is present in its zwitterionic form. Molecular proline desorbs between ˜315 K and ˜333 K depending on coverage. When adsorbed at ˜300 K, only the first monolayer is formed, and the proline is present as zwitterions, oriented such that all of the carbons are detected equally by XPS. Proline decomposes by scission of the C-COO bond, where the carboxylate moiety desorbs as carbon monoxide and carbon dioxide, while the nitrogen-containing moiety desorbs as to HCN, and evolves pyrrole at ˜390 K, pyrrolidine at ˜410 K, and final species that desorbs at ˜450 K that cannot be unequivocally assigned but may be 2-butenenitrile (CH 3-CH dbnd CH-CN), 3-butenenitrile (CH 2dbnd CH-CH 2-CN), 2-methyl-2-propenenitrile (CH 2dbnd C(CH 3)-CN) or cyclopropanecarbonitrile.

  12. Adsorption of acrolein, propanal, and allyl alcohol on Pd(111): a combined infrared reflection–absorption spectroscopy and temperature programmed desorption study

    PubMed Central

    Dostert, Karl-Heinz; O'Brien, Casey P.; Mirabella, Francesca; Ivars-Barceló, Francisco

    2016-01-01

    Atomistic-level understanding of the interaction of α,β-unsaturated aldehydes and their derivatives with late transition metals is of fundamental importance for the rational design of new catalytic materials with the desired selectivity towards C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C vs. CO bond partial hydrogenation. In this study, we investigate the interaction of acrolein, and its partial hydrogenation products propanal and allyl alcohol, with Pd(111) as a prototypical system. A combination of infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) experiments was applied under well-defined ultrahigh vacuum (UHV) conditions to obtain detailed information on the adsorption geometries of acrolein, propanal, and allyl alcohol as a function of coverage. We compare the IR spectra obtained for

  13. Dependence of effective desorption kinetic parameters on surface coverage and adsorption temperature: CO on Pd(111)

    NASA Astrophysics Data System (ADS)

    Guo, Xingcai; Yates, John T., Jr.

    1989-06-01

    The effective desorption kinetic parameters of CO on the Pd(111) surface have been studied by thermal desorption spectroscopy. The zero coverage effective desorption activation energy and the preexponential factor were found to be 35.5 kcal/mol and 1013.5 s-1, respectively. As a function of CO coverage, a four-stage correlation between Ed(θ) and the development of stable low-energy electron desorption (LEED) structures was observed for the first time at Tads= 200 K. Ed and ν1 showed a strong compensation effect with Tc=519 K. The adsorption temperature dependence of Ed from Tads=87 to 200 K was observed and interpreted qualitatively by a model involving the production of different domain structures at various adsorption temperatures and the preservation of domain structures at higher coverages during temperature programmed desorption.

  14. Plasma-assisted CuO/CeO2/TiO2-γ-Al2O3 catalysts for NO + CH4 reaction and NO temperature programmed desorption studies

    NASA Astrophysics Data System (ADS)

    Li, Huijuan; Jiang, Xiaoyuan; Zheng, Xiaoming

    2013-09-01

    The removal of NO and CH4 has been studied with a hybrid system integrating plasma activation and four Cu-based catalysts. The best catalytic performance was observed for catalysts obtained from CuO/CeO2/TiO2/γ-Al2O3.The efficiency of NO removal decreased with the order: 12%CuO/10%CeO2/15%TiO2/γ-Al2O3 > 12%CuO/15%TiO2/γ-Al2O3 > 12%CuO/γ-Al2O3 > 12% CuO/TiO2. Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) Temperature-programmed reduction (H2-TPR) and NO temperature-programmed desorption (NO-TPD) experiments were carried out to gain insight into the synergetic effects with the catalysts. The results revealed that copper species existed as bulk CuO crystalline for all the catalysts, H2-TPR suggested that the Cu2+ incorporated TiO2 or CeO2 lattice and crystalline CuO might be the most active component for NO removal, and NO-TPD studies indicated that 12%CuO/10%CeO2/15%TiO2/γ-Al2O3 catalyst had lower NO desorption temperature and larger peak area, which seemed to be responsible for the better catalytic activity over NO + CH4 reactions than other catalysts.

  15. Temperature Dependence in Desorption Induced by Electronic Transitions.

    NASA Astrophysics Data System (ADS)

    Heinz, T. F.; Misewich, J. A.

    1996-03-01

    The process of desorption induced by electronic transitions (DIET) is a subject of great theoretical and experimental interest. We have extended the classic MGR model for DIET to include initial thermal excitation of the adsorbate. In the MGR model, an electronic transition causes the adsorbate to move on excited potential energy surface. Desorption ensues whenever the adsorbate stays in the excited state long enough to acquire the necessary energy to escape from the surface. At finite temperatures, the initial transition occurs from a distribution of ground-state vibrational energies and momenta. Compared with the zero temperature desorption yield some components of the finite-temperature distribution will have enhanced yields while others will have suppressed yields. Averaging over the initial distribution, we find that the desorption yield increases substantially with temperature, particularly for short excited-state lifetimes. These findings and their extension to the multiple excitation regime are relevant to understanding the long-time scale response observed in femtosecond two-pulse correlation measurements of O_2/Pd(111). J. A. Misewich et al., J. Chem. Phys. 100, 736 (1994)

  16. Temperature Dependence in Femtosecond Desorption at Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Misewich, James

    1998-03-01

    Femtosecond laser induced desorption at metal surfaces is distinguished by two salient observations: the high yield of the reaction and the short correlation time in pump-probe measurements. This has led to the proposal of a model for desorption induced by multiple electronic transitions (DIMET). (J.A. Misewich, T.F. Heinz, and D.M. Newns, Phys. Rev. Lett. v.68 (1992) 3737.) The effect of the adsorbate temperature in DIMET has been studied using stochastic trajectory calculations with initial adsorbate vibrational quantum state occupation. We find that initial vibrational excitation substantially increases the desorption yield. These findings are related to two experimental observations. The long time-scale wings found in femtosecond time-resolved correlation measurements are thought to reflect the residual vibrational excitation left in the undesorbed adlayer following the first laser pulse. (J.A. Misewich, A. Kalamarides, T.F. Heinz, U. Hoefer, and M.M.T. Loy, J. Chem. Phys. v.100 (1994) 736.) Also, the wavelength dependence of femtosecond desorption experiments (S. Deliwala, R.J. Finlay, J.R. Goldman, T.H. Her, W.D. Mieher, and E. Mazur, Chem. Phys. Lett. v.242 (1995) 617 and D.G. Busch and W. Ho, Phys. Rev. Lett. v.77 (1996) 1338.) suggests a role for nonthermalized electrons which is interpreted in terms of the vibrational excitation left in the adlayer from unsuccessful DIET (single excitation) events as a result of the wavelength dependent nonthermalized electron distribution.

  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 ΔEdes = 11,9 kJ/mol for the perpendicular bilayer and ΔEdes = 23 ,5 kJ/mol for the parallel bilayer.

  18. Coadsorbed species explain the mechanism of methanol temperature-desorption on CeO2(111)

    DOE PAGES

    Sutton, Jonathan E.; Steven H. Overbury; Beste, Ariana

    2016-03-24

    Here, we have used density functional theory calculations to investigate the temperature-programmed desorption (TPD) of methanol from CeO2(111). For the first time, low-temperature water formation and high-temperature methanol desorption are explained by our calculations. High coverages of methanol, which correspond to experimental conditions, are required to properly describe these features of the TPD spectrum. We identify a mechanism for the low-temperature formation of water involving the dissociation of two methanol molecules on the same surface O atom and filling of the resulting surface vacancy with one of the methoxy products. After water desorption, methoxy groups are stabilized on the surfacemore » and react at higher temperatures to form methanol and formaldehyde by a disproportionation mechanism. Alternatively, the stabilized methoxy groups undergo sequential C–H scission reactions to produce formaldehyde. Calculated energy requirements and methanol/formaldehyde selectivity agree with the experimental data.« less

  19. 2,5-Dihydroxybenzoic acid: laser desorption/ionisation as a function of elevated temperature

    NASA Astrophysics Data System (ADS)

    Wallace, W. E.; Arnould, M. A.; Knochenmuss, R.

    2005-03-01

    The temperature dependence of laser desorption/ionization (LDI) ion yields has been measured for 2,5-dihydroxybenzoic acid (2,5-DHB) single crystals from room temperature to 160 °C using time-of-flight (TOF) mass spectrometry. A steep rise in ion production occurs at 90 °C, achieving a maximum at 120 °C, then decreases sharply to a minimum at 140 °C, and returns to a second maximum at 150 °C. Above 160 °C, useful information could not be obtained because of rapid volatilization of the sample into the vacuum. The overall trend in ion production, but not some of the details, is well described by a recent two-step theory of the laser desorption/ionization process, which takes into account the temperature-dependent effects of plume expansion. Measuring the background vacuum composition with a quadrupole mass spectrometer residual gas analyzer (RGA) showed an increase in thermal desorption of 2,5-DHB starting at 90 °C and maximizing at 130 °C. The increased neutral production by thermal desorption is believed to be the cause of the decrease in LDI ion production due to reduced pooling probabilities for laser-excited 2,5-DHB molecules. Thermal dehydration, condensation, and decarboxylation increase the volume of gas released at high temperatures which also serve to decrease LDI ion production at elevated temperatures. Lastly, to confirm the mass spectrometry results, the thermal desorption of 2,5-DHB single crystals under vacuum was measured using a quartz-crystal microbalance (QCM). The onset of desorption was found to occur at 90 °C and the maximum desorption rate was found at 135 °C.

  20. A FORTRAN program for modeling methane gas desorption from coal

    NASA Astrophysics Data System (ADS)

    Nguyen, V. U.

    Coal has a strong affinity for methane gas, and the process of gas adsorption (or desorption) is modeled customarily by empirical relations between the amount of gas adsorbed (or desorbed) and time. In this paper, a new and unified theory formulated to depict the process and mechanism of methane gas transport in coal is presented. The theory is validated by conventional sorption tests on cylindrical cores, and its description coded in FORTRAN is presented.

  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

  2. 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. ...

  3. 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. ...

  4. EFFECTS OF TEMPERATURE ON TRICHLOROETHYLENE DESORPTION FROM SILICA GEL AND NATURAL SEDIMENTS. 2. KINETICS. (R822626)

    EPA Science Inventory

    Isothermal desorption rates were measured at 15, 30, and 60 src="/ncer/pubs/images/deg.gif">C for trichloroethylene (TCE) on a silica gel,
    an aquifer sediment, a soil, a sand fraction, and a clay and silt fraction, all
    at 100% relative humidity. Temperature-st...

  5. SUPERFUND TREATABILITY CLEARINGHOUSE: LOW TEMPERATURE TREATMENT OF CERCLA SOILS AND DEBRIS USING THE IT LABORATORY SCALE THERMAL DESORPTION FURNACES

    EPA Science Inventory

    This study report on laboratory experiments on low temperature treatment of soils using thermal desorption. The purpose of the study was to determine if thermal desorption could remove volatile and semi-volatile contaminants from a synthetically prepared soil spiked with pre...

  6. Variable Temperature Infrared Spectroscopy Investigations of Benzoic Acid Desorption from Sodium and Calcium Montmorillonite Clays.

    PubMed

    Nickels, Tara M; Ingram, Audrey L; Maraoulaite, Dalia K; White, Robert L

    2015-12-01

    Processes involved in thermal desorption of benzoic acid from sodium and calcium montmorillonite clays are investigated by using variable temperature diffuse reflection Fourier transform infrared spectroscopy (DRIFTS). By monitoring the temperature dependence of infrared absorbance bands while heating samples, subtle changes in molecular vibrations are detected and employed to characterize specific benzoic acid adsorption sites. Abrupt changes in benzoic acid adsorption site properties occur for both clay samples at about 125 °C. Difference spectra absorbance band frequency variations indicate that adsorbed benzoic acid interacts with interlayer cations through water bridges and that these interactions can be disrupted by the presence of organic anions, in particular, benzoate. PMID:26647147

  7. Isothermal-desorption-rate measurements in the vicinity of the Curie temperature for H2 chemisorbed on nickel films

    NASA Technical Reports Server (NTRS)

    Shanabarger, M. R.

    1979-01-01

    Measurements of the isothermal desorption rate of H2 chemisorbed onto polycrystalline nickel films made for temperatures spanning the Curie temperature of the nickel film are presented. Desorption kinetics were followed by measuring the decay of the change in resistance of the nickel film brought about by hydrogen chemisorption after gas-phase H2 had been rapidly evacuated. The desorption rate is found to undergo an anomalous decrease in the vicinity of the Curie temperature, accompanied by an increase in the desorption activation energy and the equilibrium constant for the chemisorbed hydrogen. The results are interpreted in terms of anomalous variations in rate constants for the formation of the precursor molecular adsorbed state and the chemisorbed atomic state due to the phase transition in the nickel. The changes in rate constants are also considered to be in qualitative agreement with theoretical predictions based on a spin coupling between the adatom and the magnetic substrate.

  8. Effect of temperature on the desorption and decomposition of mustard from activated carbon

    SciTech Connect

    Karwacki, C.J.; Buchanan, J.H.; Mahle, J.J.; Buettner, L.C.; Wagner, G.W.

    1999-12-07

    Experimental data are reported for the desorption of bis-2-chloroethyl sulfide, (a sulfur mustard or HD) and its decomposition products from activated coconut shell carbon (CSC). The results show that under equilibrium conditions changes in the HD partial pressure are affected primarily by its loading and temperature of the adsorbent. The partial pressure of adsorbed HD is found to increase by about a decade for each 25 C increase in temperature for CSC containing 0.01--0.1 g/g HD. Adsorption equilibria of HD appear to be little affected by coadsorbed water. Although complicated by its decomposition, the distribution of adsorbed HD (of known amount) appears to occupy pores of similar energy whether dry or in the presence of adsorbed water. On dry CSC adsorbed HD appears stable, while in the presence of water its decomposition is marked by hydrolysis at low temperature and thermal decomposition at elevated temperatures. The principal volatile products desorbed are 1,4-thioxane, 2-chloroethyl vinyl sulfide and 1,4-dithiane, with the latter favoring elevated temperatures.

  9. Residual thermal desorption study of the room-temperature-formed Sb/Si(111) interface

    NASA Astrophysics Data System (ADS)

    Paliwal, Vinod Kumar; Vedeshwar, A. G.; Shivaprasad, S. M.

    2002-12-01

    This paper addresses issues of the subtle kinetic changes on the superstructural phase formation in the technologically important Sb/Si system. The thermal stability of the room-temperature (RT) deposited Sb on a (7×7) reconstructed Si(111) surface by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and electron energy-loss spectroscopy (EELS) is reported. At a very low Sb flux rate of 0.03 ML/min Sb uptake shows that it grows in the Frank-van der Merwe mode yielding a (1×1) LEED pattern for coverages of 1.0 ML and above. On annealing, AES shows that initially Sb adatoms agglomerate into large islands on top of a stable monolayer, before the Sb islands desorb in the temperature range of 350° C-480° C, to leave a sharp (1×1) stable Sb monolayer. Monolayer desorption from about 650° C results in several surface phases such as d(2×1), (5×5), ((3)×(3)-R30°) and (5(3)×5(3)-R30°). The (5×5) at 0.4 ML and the (5(3)×5(3)-R30°) at 0.2 ML are novel phases observed only during this desorption route. However, the 0.5-0.7-ML (5(3)×5(3)-R30°) phase, observed while desorbing from a 1.0-ML ((3)×(3)-R30°) initial phase, is not observed here. The EELS studies show the differences in the surface-related electronic features of the various superstructural phases. The results demonstrate the differences in the superstructural phase formation due to differences in the formation pathways adopted.

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

    SciTech Connect

    Werth, C.J.; Reinhard, M.

    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.

  11. 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.

  12. Desorption kinetics of methanol, ethanol, and water from graphene.

    PubMed

    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 monolayer (ML)) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10-100 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 nonalignment 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. PMID:24654652

  13. EFFECTS OF TEMPERATURE ON TRICHLOROETHYLENE DESORPTION FROM SILICA GEL AND NATURAL SEDIMENTS. 1. ISOTHERMS. (R822626)

    EPA Science Inventory

    Aqueous phase isotherms were calculated from vapor phase desorption isotherms
    measured at 15, 30, and 60 C for
    trichloroethylene on a silica gel, an aquifer sediment, a soil, a sand fraction,
    and a clay and silt fraction, all at...

  14. The use of thermal desorption in monitoring for the chemical weapons demilitarization program.

    PubMed

    Harper, Martin

    2002-10-01

    Under international treaty, the United States and Russia are disposing of their aging stockpile of chemical weapons. Incineration and chemical neutralization are options for sites in the United States, although Russia prefers the latter. The storage and disposal of bulk and chemical agents and weapons involve unique hazards of handling extremely toxic materials. There are three major areas of concern--the storage stockpile, the disposal area, and the discovery and destruction of "found" material not considered part of the stockpile. Methods have been developed to detect the presence of chemical agents in the air, and these are used to help assure worker protection and the safety of the local population. Exposure limits for all chemical agents are low, sometimes nanograms per cubic meter for worker control limits and picograms per cubic meter for general population limits. There are three types of monitoring used in the USA: alarm, confirmation, and historical. Alarm monitors are required to give relatively immediate real-time responses to agent leaks. They are simple to operate and rugged, and provide an alarm in near real-time (generally a few minutes). Alarm monitors for the demilitarization program are based on sorbent pre-concentration followed by thermal desorption and simple gas chromatography. Alarms may need to be confirmed by another method, such as sample tubes collocated with the alarm monitor and analyzed in a laboratory by more sophisticated chromatography. Sample tubes are also used for historical perimeter monitoring, with sample periods typically of 12 h. The most common detector is the flame photometric detector, in sulfur or phosphorous mode, although others, such as mass-selective detectors, also have been used. All agents have specific problems with collection, chromatography and detection. Monitoring is not made easier by interferences from pesticide spraying, busy roadways or military firing ranges. Exposure limits drive the requirements for

  15. 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.

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

    SciTech Connect

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

    2014-05-08

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

  17. N2 and CO Desorption Energies from Water Ice

    NASA Astrophysics Data System (ADS)

    Fayolle, Edith C.; Balfe, Jodi; Loomis, Ryan; Bergner, Jennifer; Graninger, Dawn; Rajappan, Mahesh; Öberg, Karin I.

    2016-01-01

    The relative desorption energies of CO and N2 are key to interpretations of observed interstellar CO and N2 abundance patterns, including the well-documented CO and N2H+ anti-correlations in disks, protostars, and molecular cloud cores. Based on laboratory experiments on pure CO and N2 ice desorption, the difference between CO and N2 desorption energies is small; the N2-to-CO desorption energy ratio is 0.93 ± 0.03. Interstellar ices are not pure, however, and in this study we explore the effect of water ice on the desorption energy ratio of the two molecules. We present temperature programmed desorption experiments of different coverages of 13CO and 15N2 on porous and compact amorphous water ices and, for reference, of pure ices. In all experiments, 15N2 desorption begins a few degrees before the onset of 13CO desorption. The 15N2 and 13CO energy barriers are 770 and 866 K for the pure ices, 1034-1143 K and 1155-1298 K for different submonolayer coverages on compact water ice, and 1435 and 1575 K for ˜1 ML of ice on top of porous water ice. For all equivalent experiments, the N2-to-CO desorption energy ratio is consistently 0.9. Whenever CO and N2 ice reside in similar ice environments (e.g., experience a similar degree of interaction with water ice) their desorption temperatures should thus be within a few degrees of one another. A smaller N2-to-CO desorption energy ratio may be present in interstellar and circumstellar environments if the average CO ice molecules interacts more with water ice compared to the average N2 molecules.

  18. N2 and CO Desorption Energies from Water Ice

    NASA Astrophysics Data System (ADS)

    Fayolle, Edith C.; Balfe, Jodi; Loomis, Ryan; Bergner, Jennifer; Graninger, Dawn; Rajappan, Mahesh; Öberg, Karin I.

    2016-01-01

    The relative desorption energies of CO and N2 are key to interpretations of observed interstellar CO and N2 abundance patterns, including the well-documented CO and N2H+ anti-correlations in disks, protostars, and molecular cloud cores. Based on laboratory experiments on pure CO and N2 ice desorption, the difference between CO and N2 desorption energies is small; the N2-to-CO desorption energy ratio is 0.93 ± 0.03. Interstellar ices are not pure, however, and in this study we explore the effect of water ice on the desorption energy ratio of the two molecules. We present temperature programmed desorption experiments of different coverages of 13CO and 15N2 on porous and compact amorphous water ices and, for reference, of pure ices. In all experiments, 15N2 desorption begins a few degrees before the onset of 13CO desorption. The 15N2 and 13CO energy barriers are 770 and 866 K for the pure ices, 1034–1143 K and 1155–1298 K for different submonolayer coverages on compact water ice, and 1435 and 1575 K for ∼1 ML of ice on top of porous water ice. For all equivalent experiments, the N2-to-CO desorption energy ratio is consistently 0.9. Whenever CO and N2 ice reside in similar ice environments (e.g., experience a similar degree of interaction with water ice) their desorption temperatures should thus be within a few degrees of one another. A smaller N2-to-CO desorption energy ratio may be present in interstellar and circumstellar environments if the average CO ice molecules interacts more with water ice compared to the average N2 molecules.

  19. 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.

  20. Desorption of Hg(II) and Sb(V) on extracellular polymeric substances: effects of pH, EDTA, Ca(II) and temperature shocks.

    PubMed

    Zhang, Daoyong; Lee, Duu-Jong; Pan, Xiangliang

    2013-01-01

    Extracellular polymeric substances (EPS) existed ubiquitously in biological systems affect the mobility and availability of heavy metals in the environments. The adsorption-desorption behaviors of Hg(II) and Sb(V) on EPS were investigated. The sorption rates follow Sb(V) > Hg(II), and the desorption rates follow reverse order. Applications of ethylene diamine tetraacetic acid (EDTA), Ca(II) and pH shocks affect desorption rates and desorbed quantities of Hg(II) from EPS-Hg complex. Temperature shock minimally affects the desorption rate of Hg(II). Conversely, the EPS-Sb complex is stable subjected to EDTA, Ca(II), temperature or pH shocks. The excitation-emission matrix (EEM) fluorescence spectroscopy and fast-Fourier (FT-IR) analysis showed that Hg(II) and Sb(V) principally interacted with polysaccharides and protein-like compounds in the EPS, respectively. The EPS-Hg complex presents a time bomb that may release high levels of Hg(II) in short time period under environmental shocks. PMID:23247408

  1. Desorption of Hg(II) and Sb(V) on extracellular polymeric substances: effects of pH, EDTA, Ca(II) and temperature shocks.

    PubMed

    Zhang, Daoyong; Lee, Duu-Jong; Pan, Xiangliang

    2013-01-01

    Extracellular polymeric substances (EPS) existed ubiquitously in biological systems affect the mobility and availability of heavy metals in the environments. The adsorption-desorption behaviors of Hg(II) and Sb(V) on EPS were investigated. The sorption rates follow Sb(V) > Hg(II), and the desorption rates follow reverse order. Applications of ethylene diamine tetraacetic acid (EDTA), Ca(II) and pH shocks affect desorption rates and desorbed quantities of Hg(II) from EPS-Hg complex. Temperature shock minimally affects the desorption rate of Hg(II). Conversely, the EPS-Sb complex is stable subjected to EDTA, Ca(II), temperature or pH shocks. The excitation-emission matrix (EEM) fluorescence spectroscopy and fast-Fourier (FT-IR) analysis showed that Hg(II) and Sb(V) principally interacted with polysaccharides and protein-like compounds in the EPS, respectively. The EPS-Hg complex presents a time bomb that may release high levels of Hg(II) in short time period under environmental shocks.

  2. Hydrogen desorption kinetics for aqueous hydrogen fluoride and remote hydrogen plasma processed silicon (001) surfaces

    SciTech Connect

    King, Sean W. Davis, Robert F.; Carter, Richard J.; Schneider, Thomas P.; Nemanich, Robert J.

    2015-09-15

    The desorption kinetics of molecular hydrogen (H{sub 2}) from silicon (001) surfaces exposed to aqueous hydrogen fluoride and remote hydrogen plasmas were examined using temperature programmed desorption. Multiple H{sub 2} desorption states were observed and attributed to surface monohydride (SiH), di/trihydride (SiH{sub 2/3}), and hydroxide (SiOH) species, subsurface hydrogen trapped at defects, and hydrogen evolved during the desorption of surface oxides. The observed surface hydride species were dependent on the surface temperature during hydrogen plasma exposure with mono, di, and trihydride species being observed after low temperature exposure (150 °C), while predominantly monohydride species were observed after higher temperature exposure (450 °C). The ratio of surface versus subsurface H{sub 2} desorption was also found to be dependent on the substrate temperature with 150 °C remote hydrogen plasma exposure generally leading to more H{sub 2} evolved from subsurface states and 450 °C exposure leading to more H{sub 2} desorption from surface SiH{sub x} species. Additional surface desorption states were observed, which were attributed to H{sub 2} desorption from Si (111) facets formed as a result of surface etching by the remote hydrogen plasma or aqueous hydrogen fluoride treatment. The kinetics of surface H{sub 2} desorption were found to be in excellent agreement with prior investigations of silicon surfaces exposed to thermally generated atomic hydrogen.

  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.; Ortiz-Villafuerte, J.

    1995-04-01

    The addition of hydrogen to the purge stream has been shown to enhance tritium release from ceramic breeder materials; however, this added hydrogen can lead to increased costs in the tritium purification system. The objective of this work is to develop an understanding of the interactions between hydrogen and lithium oxide surfaces so that the authors can take full advantage of the observed enhancement of tritium release caused by hydrogen addition without incurring high costs in the tritium purification plant.

  4. Laser-induced thermal desorption of aniline from silica surfaces

    NASA Astrophysics Data System (ADS)

    Voumard, Pierre; Zenobi, Renato

    1995-10-01

    A complete study on the energy partitioning upon laser-induced thermal desorption of aniline from silica surfaces was undertaken. The measurements include characterization of the aniline-quartz adsorption system using temperature-programmed desorption, the extrapolation of quasiequilibrium desorption temperatures to the regime of laser heating rates on the order of 109-1010 K/s by computational means, measurement of the kinetic energy distributions of desorbing aniline using a pump-probe method, and the determination of internal energies with resonance-enhanced multiphoton ionization spectroscopy. The measurements are compared to calculations of the surface temperature rise and the resulting desorption rates, based on a finite-difference mathematical description of pulsed laser heating. While the surface temperature of laser-heated silica reaches about 600-700 K at the time of desorption, the translational temperature of laser-desorbed aniline was measured to be Tkin=420±60 K, Tvib was 360±60 K, and Trot was 350±100 K. These results are discussed using different models for laser-induced thermal desorption from surfaces.

  5. 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.

  6. Thermal decomposition pathway and desorption study of isopropanol and tert-butanol on Si(100)

    NASA Astrophysics Data System (ADS)

    Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

    2002-09-01

    Thermal decomposition pathway and desorption of isopropanol (IPA) and tert-butanol on Si(100) were studied using temperature programed desorption. Adsorbed alcohols studied were decomposed into atomic hydrogen and alkoxy on the surface. During heating the sample up to 1000 K, acetone, propylene, and hydrogen were desorbed as decomposition products of IPA on Si(100). Desorption pathways of IPA on Si(100) were largely consistent with those on metal surfaces: beta-hydride elimination reaction to acetone and C-O scission to propylene. For tert-butanol, which has no beta-hydrogen, isobutene and hydrogen were observed as main desorption products. copyright 2002 American Vacuum Society.

  7. 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)

  8. Probing Electron Transfer Dynamics at MgO Surfaces by Mg-Atom Desorption

    SciTech Connect

    Joly, Alan G.; Henyk, Matthias; Beck, Kenneth M.; Trevisanutto, P. E.; Sushko, Petr V.; Hess, Wayne P.; Shluger, Alexander L.

    2006-08-14

    Desorption of a weakly bound adsorbate from a porous solid was studied for the case of N2 on amorphous solid water (ASW). Porous ASW films of different thickness were grown on Pt(111) by ballistic deposition. N2 adsorption and desorption kinetics were monitored mass-spectrometrically. Temperature programmed desorption spectra show that with the increasing film thickness, the N2 desorption peak systematically shifts to higher temperatures. The results are explained and quantitatively reproduced by a simple model, which assumes that the N2 transport within the film is faster than the depletion rate to vacuum. The local coverage at the pore mouth determines the desorption rate. For thick ASW films (>1 μm), the assumption of the fast equilibration within the film is shown to be no longer valid due to diffusion limitations. The mechanisms of the adsorbate transport are discussed.

  9. Sorption/desorption behavior of iodine on graphite. [HTGR

    SciTech Connect

    Lorenz, R.A.; Dyer, F.F.; Towns, R.L.

    1982-11-01

    An experimental program was undertaken to extend the data on the sorption and desorption of iodine on graphite to more realistic high-temperature gas-cooled reactor (HTGR) operating conditions. This was accomplished by heating compacts of H-451 or S-2020 graphite at 250 to 1000/sup 0/C in continuously flowing helium (at atmospheric pressure) that contained iodine at pressures of 10/sup -6/ Pa (10/sup -11/ to 10/sup -1/ to 10/sup -6/ bar). Equilibrium adsorption data were generally well-behaved and reproducible with the H-451 graphite. Type S-2020 graphite sorbed more iodine, especially in the temperature range 700 to 800/sup 0/C. Although desorption appeared to initiate as reversible sorption, the rate of loss of iodine decreased with time. During desorption from the S-2020 graphite at 700 and 800/sup 0/C, a temporary plateau was reached that was sensitive to helium flow and pressure.

  10. 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.

  11. Low-Cost Programmed Oven Temperature Controller.

    ERIC Educational Resources Information Center

    Clubine, Gerald D.

    1982-01-01

    A remote, programed oven temperature controller unit was built for about $425.00. Specifications, circuit diagrams, design details, and operations are discussed. Detailed information including complete schematics, parts list, and detailed theory of operation may be obtained by contacting the author. (Author/SK)

  12. Low-Temperature Power Electronics Program

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Dickman, John E.; Hammoud, Ahmad; Gerber, Scott

    1997-01-01

    Many space and some terrestrial applications would benefit from the availability of low-temperature electronics. Exploration missions to the outer planets, Earth-orbiting and deep-space probes, and communications satellites are examples of space applications which operate in low-temperature environments. Space probes deployed near Pluto must operate in temperatures as low as -229 C. Figure 1 depicts the average temperature of a space probe warmed by the sun for various locations throughout the solar system. Terrestrial applications where components and systems must operate in low-temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation system, and arctic exploration. The development of electrical power systems capable of extremely low-temperature operation represents a key element of some advanced space power systems. The Low-Temperature Power Electronics Program at NASA Lewis Research Center focuses on the design, fabrication, and characterization of low-temperature power systems and the development of supporting technologies for low-temperature operations such as dielectric and insulating materials, power components, optoelectronic components, and packaging and integration of devices, components, and systems.

  13. 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.

  14. Associative Electron Stimulated Desorption of Neutral CO Molecules

    NASA Astrophysics Data System (ADS)

    Šutara, F.; Matolín, V.

    2001-11-01

    The Electron Stimulated Desorption (ESD) of neutral CO molecules was studied on polycrystalline Ni surface. Combined ESD and temperature programmed desorption (TPD) measurements were used to observe the variations of neutral ESD yield in dependence on CO coverage, containing direct information about the cross section for ESD of neutral CO molecules in relation to various CO adsorption states. The results show evidence of ESD of neutral CO molecules from dissociative adsorption states. The cross section for this associative ESD process is relatively high in comparison with the CO ESD cross section for molecular CO adsorption.

  15. Hydrogen desorption from hydrogen fluoride and remote hydrogen plasma cleaned silicon carbide (0001) surfaces

    SciTech Connect

    King, Sean W. Tanaka, Satoru; Davis, Robert F.; Nemanich, Robert J.

    2015-09-15

    Due to the extreme chemical inertness of silicon carbide (SiC), in-situ thermal desorption is commonly utilized as a means to remove surface contamination prior to initiating critical semiconductor processing steps such as epitaxy, gate dielectric formation, and contact metallization. In-situ thermal desorption and silicon sublimation has also recently become a popular method for epitaxial growth of mono and few layer graphene. Accordingly, numerous thermal desorption experiments of various processed silicon carbide surfaces have been performed, but have ignored the presence of hydrogen, which is ubiquitous throughout semiconductor processing. In this regard, the authors have performed a combined temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) investigation of the desorption of molecular hydrogen (H{sub 2}) and various other oxygen, carbon, and fluorine related species from ex-situ aqueous hydrogen fluoride (HF) and in-situ remote hydrogen plasma cleaned 6H-SiC (0001) surfaces. Using XPS, the authors observed that temperatures on the order of 700–1000 °C are needed to fully desorb C-H, C-O and Si-O species from these surfaces. However, using TPD, the authors observed H{sub 2} desorption at both lower temperatures (200–550 °C) as well as higher temperatures (>700 °C). The low temperature H{sub 2} desorption was deconvoluted into multiple desorption states that, based on similarities to H{sub 2} desorption from Si (111), were attributed to silicon mono, di, and trihydride surface species as well as hydrogen trapped by subsurface defects, steps, or dopants. The higher temperature H{sub 2} desorption was similarly attributed to H{sub 2} evolved from surface O-H groups at ∼750 °C as well as the liberation of H{sub 2} during Si-O desorption at temperatures >800 °C. These results indicate that while ex-situ aqueous HF processed 6H-SiC (0001) surfaces annealed at <700 °C remain terminated by some surface C–O and

  16. 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.

  17. Model verification of thermal programmed desorption-mass spectrometry for estimation of release energy values for polycyclic aromatic hydrocarbons on mineral sorbents.

    PubMed

    Nicholl, Sara I; Talley, Jeffrey W; Silliman, Stephan

    2004-11-01

    The physical availability of organic compounds in soil and sediment strongly influences their bioavailability and toxicity. Previous work has indicated that physical availability changes throughout the processes of aging and treatment and that it can be linked to the energy required to release the compound from its sorbent matrix, with a higher energy indicating a more tightly bound compound. This study focused on determining release energy values for various mineral geosorbents (glass beads, sand, and kaolin) contaminated with a 16 polycyclic aromatic hydrocarbon (PAH) mixture. The sorbents were analyzed using thermal program desorption/mass spectrometry (TPD/MS) and the release energy values were calculated from the resulting thermograms utilizing a nonlinear fit of the analytical solution to a simplified version of the Polanyi-Wigner equation. This solution method resulted in a series of combinations of values for the pre-exponential factor (v) and release energy (E) that produced desorption rate curves with similar errors when fit to actual data sets. These combinations can be viewed as an error surface, which clearly shows a valley of minimum error values spanning the range of both E and v. This indicates that this method may not provide a unique set of E- and v-values and suggests that the simplified version of the Polanyi-Wigner equation cannot be used to determine release energy based on TPD data alone.

  18. Model verification of thermal programmed desorption-mass spectrometry for estimation of release energy values for polycyclic aromatic hydrocarbons on mineral sorbents.

    PubMed

    Nicholl, Sara I; Talley, Jeffrey W; Silliman, Stephan

    2004-11-01

    The physical availability of organic compounds in soil and sediment strongly influences their bioavailability and toxicity. Previous work has indicated that physical availability changes throughout the processes of aging and treatment and that it can be linked to the energy required to release the compound from its sorbent matrix, with a higher energy indicating a more tightly bound compound. This study focused on determining release energy values for various mineral geosorbents (glass beads, sand, and kaolin) contaminated with a 16 polycyclic aromatic hydrocarbon (PAH) mixture. The sorbents were analyzed using thermal program desorption/mass spectrometry (TPD/MS) and the release energy values were calculated from the resulting thermograms utilizing a nonlinear fit of the analytical solution to a simplified version of the Polanyi-Wigner equation. This solution method resulted in a series of combinations of values for the pre-exponential factor (v) and release energy (E) that produced desorption rate curves with similar errors when fit to actual data sets. These combinations can be viewed as an error surface, which clearly shows a valley of minimum error values spanning the range of both E and v. This indicates that this method may not provide a unique set of E- and v-values and suggests that the simplified version of the Polanyi-Wigner equation cannot be used to determine release energy based on TPD data alone. PMID:15559267

  19. ENGINEERING BULLETIN: THERMAL DESORPTION TREATMENT.

    EPA Science Inventory

    Thermal desorption is an EX SITU means to physically separate volatile and some semivolatile contaminants from soil, sediments, sludge, and filter cakes by heating them at temperatures high enough to volatilize the organic contaminants. For wastes containing up to 10 percent orga...

  20. 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.

  1. Influence 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.

  2. 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.

  3. The NASA high temperature superconductivity program

    NASA Technical Reports Server (NTRS)

    Sokoloski, Martin M.; Romanofsky, Robert R.

    1990-01-01

    It has been recognized from the onset that high temperature superconductivity held great promise for major advances across a broad range of NASA interests. The current effort is organized around four key areas: communications and data, sensors and cryogenics, propulsion and power, and space materials technology. Recently, laser ablated YBa2Cu3O(7-x) films on LaAIO produced far superior RF characteristics when compared to metallic films on the same substrate. This achievement has enabled a number of unique microwave device applications, such as low insertion loss phase shifters and high Q filters. Melt texturing and melt quenched techniques are being used to produce bulk materials with optimized magnetic properties. These yttrium enriched materials possess enhanced flux pinning characteristics and will lead to prototype cryocooler bearings. Significant progress has also occurred in bolometer and current lead technology. Studies are being conducted to evaluate the effect of high temperature superconducting materials on the performance and life of high power magneto-plasma-dynamic thrusters. Extended studies were also performed to evaluate the benefit of superconducting magnetic energy storage for LEO space station, lunar and Mars mission applications. The project direction and level of effort of the program are also described.

  4. 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-).

  5. Adsorption, Desorption, and Diffusion of Nitrogen in a Model Nanoporous Material: I. Surface Limited Desorption Kinetics in Amorphous Solid Water

    SciTech Connect

    Zubkov, Tykhon; Smith, R. Scott; Engstrom, Todd R.; Kay, Bruce D.

    2007-11-14

    The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programmed desorption (TPD), and reflection-absorption infrared spectroscopy (RAIRS). The ASW films were grown on Pt(111) at 23 K by ballistic deposition from a collimated H2O beam at various incident angles to control the film porosity. The experimental results show that the N2 condensation coefficient is essentially unity until near saturation, independent of the ASW film thickness. This means that N2 transport within the porous films is rapid. The TPD results show that the desorption of a fixed dose of N2 shifts to higher temperature with ASW film thickness. Kinetic analysis of the TPD spectra shows that a film thickness rescaling of the coverage dependent activation energy curve results in a single master curve. Simulation of the TPD spectra using this master curve results in a quantitative fit to the experiments over a wide range of ASW thicknesses (up to 1000 layers, ~0.5 mm). The success of the rescaling model indicates that N2 transport within the porous film is rapid enough to maintain a uniform distribution throughout the film on a time scale faster than desorption.

  6. Desorption of TEDA from impregnated charcoals

    SciTech Connect

    Wood, G.

    1980-01-01

    Triethylenediamine (TEDA) is one of the most effective charcoal impregnants for trapping organic forms of radioiodine from air. It is used in air cleaning adsorbers, air samplers, and air purifying respirator canisters and cartridges for airborne radioiodine. Volatility of the pure crystals suggested the possibility of significant TEDA desorption in these applications, resulting in toxic levels of amine and/or degradation of sorbent efficiency. Measurements of TEDA desorption rates were made for four commercial charcoals. Temperatures of 70 to 120/sup 0/C were used to give levels detectable with a photoionization detector. Extrapolations to temperatures nearer normal ambient were made by using Clapeyron equation plots. Among three charcoals with the same 5% level of TEDA impregnation, desorption rates varied over factors as great as 10. Slopes of Clapeyron plots were similar, giving an average 25 kcal/mol heat of desorption. This corresponds to a doubling of the TEDA desorption rate with each 5/sup 0/C (9/sup 0/F) rise in temperature. Desorption rates were directly proportional to airflow rates or velocities through the test beds and independent of humidity. Desorption rates per unit weight of charcoal decreased exponentially with bed depth, presumably due to TEDA readsorption. Calculations based on this data and the geometry of a standard adsorber cell showed that at normal ambient temperatures: (1) concentrations of TEDA in effluent air are well below expected toxic levels; and (2) losses of TEDA may be significant. At elevated temperatures TEDA desorption rates are high enough to affect methyl iodide trapping efficiencies and, possibly, charcoal ignition temperatures.

  7. Photon simulated desorption revisited

    NASA Astrophysics Data System (ADS)

    Menzel, D.

    A promising new method for surface investigations is discussed: Photon stimulated desorption. The electronic excitations of adsorbate complexes on surfaces, either by electron impact or photon absorption, which can lead to repulsive states of the complex and therefore to expulsion of ions and neutrals are considered. Such processes are termed electron (or photon) stimulated desorption, ESD and PSD, respectively. Apart from the primary agent (electrons or photons), these processes are similar, and common label "desorption induced by electronic transitions" (acronym DIET) was proposed. Desorption effects, intrinsic photoneffects, and some of the advantages of PSD over ESD are discussed.

  8. Glycolaldehyde, methyl formate and acetic acid adsorption and thermal desorption from interstellar ices

    NASA Astrophysics Data System (ADS)

    Burke, Daren J.; Puletti, Fabrizio; Brown, Wendy A.; Woods, Paul M.; Viti, Serena; Slater, Ben

    2015-02-01

    We have undertaken a detailed investigation of the adsorption, desorption and thermal processing of the astrobiologically significant isomers glycolaldehyde, acetic acid and methyl formate. Here, we present the results of laboratory infrared and temperature programmed desorption (TPD) studies of the three isomers from model interstellar ices adsorbed on a carbonaceous dust grain analogue surface. Laboratory infrared data show that the isomers can be clearly distinguished on the basis of their infrared spectra, which has implications for observations of interstellar ice spectra. Laboratory TPD data also show that the three isomers can be distinguished on the basis of their thermal desorption behaviour. In particular, TPD data show that the isomers cannot be treated the same way in astrophysical models of desorption. The desorption of glycolaldehyde and acetic acid from water-dominated ices is very similar, with desorption being mainly dictated by water ice. However, methyl formate also desorbs from the surface of the ice, as a pure desorption feature, and therefore desorbs at a lower temperature than the other two isomers. This is more clearly indicated by models of the desorption on astrophysical time-scales corresponding to the heating rate of 25 and 5 M⊙ stars. For a 25 M⊙ star, our model shows that a proportion of the methyl formate can be found in the gas phase at earlier times compared to glycolaldehyde and acetic acid. This has implications for the observation and detection of these molecules, and potentially explains why methyl formate has been observed in a wider range of astrophysical environments than the other two isomers.

  9. Implementation of New TPD Analysis Techniques in the Evaluation of Second Order Desorption Kinetics of Cyanogen from Cu(001)

    SciTech Connect

    Hinch, B.J.; Senanayake, S.; Ciftlikli, E.Z.; Lee, E.Y.M.; Lallo, J.; Rangan, S.

    2010-12-21

    The interactions of cyanide species with a copper (001) surface were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Adsorbed cyanide species (CN{sub (a)}) undergo recombinative desorption evolving molecular cyanogen (C{sub 2}N{sub 2}). As the adsorbed CN species charge upon adsorption, mutually repulsive dipolar interactions lead to a marked desorption energy reduction with increasing CN{sub (a)} coverages. Two new TPD analysis approaches were developed, which used only accurately discernible observables and which do not assume constant desorption energies, E{sub d}, and pre-exponential values, v. These two approaches demonstrated a linear variation of E{sub d} with instantaneous coverage. The first approach involved an analysis of the variations of desorption peak asymmetry with initial CN coverages. The second quantitative approach utilized only temperatures and intensities of TPD peaks, together with deduced surface coverages at the peak maxima, also as a function of initial surface coverages. Parameters derived from the latter approach were utilized as initial inputs for a comprehensive curve fit analysis technique. Excellent fits for all experimental desorption curves were produced in simulations. The curve fit analysis confirms that the activation energy of desorption of 170-180 kJ/mol at low coverage decreases by up to 14-15 kJ/mol at CN saturation.

  10. Implementation of New TPD Analysis Techniques in the Evaluation of Second Order Desorption Kinetics of Cyanogen from Cu(001)

    SciTech Connect

    E Ciftlikli; E Lee; J Lallo; S Rangan; S Senanayake; B Hinch

    2011-12-31

    The interactions of cyanide species with a copper (001) surface were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Adsorbed cyanide species (CN{sub (a)}) undergo recombinative desorption evolving molecular cyanogen (C{sub 2}N{sub 2}). As the adsorbed CN species charge upon adsorption, mutually repulsive dipolar interactions lead to a marked desorption energy reduction with increasing CN{sub (a)} coverages. Two new TPD analysis approaches were developed, which used only accurately discernible observables and which do not assume constant desorption energies, E{sub d}, and pre-exponential values, v. These two approaches demonstrated a linear variation of E{sub d} with instantaneous coverage. The first approach involved an analysis of the variations of desorption peak asymmetry with initial CN coverages. The second quantitative approach utilized only temperatures and intensities of TPD peaks, together with deduced surface coverages at the peak maxima, also as a function of initial surface coverages. Parameters derived from the latter approach were utilized as initial inputs for a comprehensive curve fit analysis technique. Excellent fits for all experimental desorption curves were produced in simulations. The curve fit analysis confirms that the activation energy of desorption of 170-180 kJ/mol at low coverage decreases by up to 14-15 kJ/mol at CN saturation.

  11. Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces

    SciTech Connect

    King, Sean W. Davis, Robert F.; Nemanich, Robert J.

    2014-09-01

    The adsorption and desorption of halogen and other gaseous species from surfaces is a key fundamental process for both wet chemical and dry plasma etch and clean processes utilized in nanoelectronic fabrication processes. Therefore, to increase the fundamental understanding of these processes with regard to aluminum nitride (AlN) surfaces, temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) have been utilized to investigate the desorption kinetics of water (H{sub 2}O), fluorine (F{sub 2}), hydrogen (H{sub 2}), hydrogen fluoride (HF), and other related species from aluminum nitride thin film surfaces treated with an aqueous solution of buffered hydrogen fluoride (BHF) diluted in methanol (CH{sub 3}OH). Pre-TPD XPS measurements of the CH{sub 3}OH:BHF treated AlN surfaces showed the presence of a variety of Al-F, N-F, Al-O, Al-OH, C-H, and C-O surfaces species in addition to Al-N bonding from the AlN thin film. The primary species observed desorbing from these same surfaces during TPD measurements included H{sub 2}, H{sub 2}O, HF, F{sub 2}, and CH{sub 3}OH with some evidence for nitrogen (N{sub 2}) and ammonia (NH{sub 3}) desorption as well. For H{sub 2}O, two desorption peaks with second order kinetics were observed at 195 and 460 °C with activation energies (E{sub d}) of 51 ± 3 and 87 ± 5 kJ/mol, respectively. Desorption of HF similarly exhibited second order kinetics with a peak temperature of 475 °C and E{sub d} of 110 ± 5 kJ/mol. The TPD spectra for F{sub 2} exhibited two peaks at 485 and 585 °C with second order kinetics and E{sub d} of 62 ± 3 and 270 ± 10 kJ/mol, respectively. These values are in excellent agreement with previous E{sub d} measurements for desorption of H{sub 2}O from SiO{sub 2} and AlF{sub x} from AlN surfaces, respectively. The F{sub 2} desorption is therefore attributed to fragmentation of AlF{sub x} species in the mass spectrometer ionizer. H{sub 2} desorption exhibited

  12. Finite difference program for calculating hydride bed wall temperature profiles

    SciTech Connect

    Klein, J.E.

    1992-10-29

    A QuickBASIC finite difference program was written for calculating one dimensional temperature profiles in up to two media with flat, cylindrical, or spherical geometries. The development of the program was motivated by the need to calculate maximum temperature differences across the walls of the Tritium metal hydrides beds for thermal fatigue analysis. The purpose of this report is to document the equations and the computer program used to calculate transient wall temperatures in stainless steel hydride vessels. The development of the computer code was motivated by the need to calculate maximum temperature differences across the walls of the hydrides beds in the Tritium Facility for thermal fatigue analysis.

  13. 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.

  14. Segregation of O2 and CO on the surface of dust grains determines the desorption energy of O2

    NASA Astrophysics Data System (ADS)

    Noble, J. A.; Diana, S.; Dulieu, F.

    2015-12-01

    Selective depletion towards pre-stellar cores is still not understood. The exchange between the solid and gas phases is central to this mystery. The aim of this paper is to show that the thermal desorption of O2 and CO from a submonolayer mixture is greatly affected by the composition of the initial surface population. We have performed thermally programmed desorption (TPD) experiments on various submonolayer mixtures of O2 and CO. Pure O2 and CO exhibit almost the same desorption behaviour, but their desorption differs strongly when mixed. Pure O2 is slightly less volatile than CO, while in mixtures, O2 desorbs earlier than CO. We analyse our data using a desorption law linking competition for binding sites with desorption, based on the assumption that the binding energy distribution of both molecules is the same. We apply Fermi-Dirac statistics in order to calculate the adsorption site population distribution, and derive the desorbing fluxes. Despite its simplicity, the model reproduces the observed desorption profiles, indicating that competition for adsorption sites is the reason for lower temperature O2 desorption. CO molecules push-out or `dislodge' O2 molecules from the most favourable binding sites, ultimately forcing their early desorption. It is crucial to consider the surface coverage of dust grains in any description of desorption. Competition for access to binding sites results in some important discrepancies between similar kinds of molecules, such as CO and O2. This is an important phenomenon to be investigated in order to develop a better understanding of the apparently selective depletion observed in dark molecular clouds.

  15. Mechanisms of deep benzene oxidation on the Pt(1 1 1) surface using temperature-programmed reaction methods

    NASA Astrophysics Data System (ADS)

    Marsh, Anderson L.; Gland, John L.

    2003-06-01

    The catalytic oxidation of benzene on the Pt(1 1 1) surface has been characterized using temperature-programmed reaction spectroscopy (TPRS) over a wide range of benzene and oxygen coverages. Coadsorbed atomic oxygen and benzene are the primary reactants on the surface during the initial oxidation step. Benzene is oxidized over the 300-500 K range to produce carbon dioxide and water. Carbon-hydrogen and carbon-carbon bond activation are clearly rate-limiting steps for these reactions. Preferential oxidation causes depletion of bridge-bonded benzene, suggesting enhanced reactivity in this bonding configuration. When oxygen is in excess on the surface, all of the surface carbon and hydrogen is oxidized. When benzene is in excess on the surface, hydrogen produced by dehydrogenation is desorbed after all of the surface oxygen has been consumed. Repulsive interactions between benzene and molecular oxygen dominate at low temperatures. Preadsorption of oxygen inhibits adsorption of less reactive benzene in threefold hollow sites. The desorption temperature of this non-reactive chemisorbed benzene decreases and overlaps with the multilayer desorption peak with increasing oxygen exposure. The results presented here provide a clear picture of rate-limiting steps during deep oxidation of benzene on the Pt(1 1 1) surface.

  16. Program for an improved hypersonic temperature-sensing probe

    NASA Technical Reports Server (NTRS)

    Reilly, Richard J.

    1993-01-01

    Under a NASA Dryden-sponsored contract in the mid 1960s, temperatures of up to 2200 C were successfully measured using a fluid oscillator. The current program, although limited in scope, explores the problem areas which must be solved if this technique is to be extended to 10,000 R. The potential for measuring extremely high temperatures, using fluid oscillator techniques, stems from the fact that the measuring element is the fluid itself. The containing structure of the oscillator need not be brought to equilibrium temperature with with the fluid for temperature measurement, provided that a suitable calibration can be arranged. This program concentrated on review of high-temperature material developments since the original program was completed. Other areas of limited study included related pressure instrumentation requirements, dissociation, rarefied gas effects, and analysis of sensor time response.

  17. High temperature static strain sensor development program

    NASA Technical Reports Server (NTRS)

    Hulse, C.; Lemkey, F.; Bailey, R.; Grant, H.

    1982-01-01

    The development of resistance strain gages which are useful for static strain measurements on nickel or cobalt superalloy parts inside a gas turbine engine on a test stand were examined. These measurements of a strain gage alloy development program which to be followed by an optional investigation of complete strain gage systems which will use the best of the alloys developed together with other system improvements is reviewed. The specific goal for the complete system is to make measurements to 2,000 micro epsilon with error of only + or - 10% over a 50 hour period. In addition to simple survival and stability, attaining a low thermal coefficient to resistivity, of order 100 ppm/K or less, is also a major goal. The first task was to select candidate alloys or alloy systems using a search of the literature and the available metallurgical theory. Alloy candidates were evaluated and compared by a grading system. Equipment and techniques were developed which are suitable for iterative studies of a variety of compositions. Many compositions were examined and significantly improved alloys were identified.

  18. Multilayer water condensation and desorption on hydrophobic and hydrophilic surfaces

    NASA Astrophysics Data System (ADS)

    Kasemo, Bengt; Lindroth, Trolle; Chakarov, Dinko

    2000-03-01

    We are studying water condensation and desorption on hydrophilic (e.g. Pt (111)) and hydrophilic (e.g. octane films on Pt(111) and graphite (0001)), at temperatures around 100-150K. On hydrophilic surfaces the behavior is well known from a manifold of earlier studies. On hydrophobic surfaces there are two qualitatively new behaviors; (i) The effective sticking coefficient can be much less than one because of the much weaker monomer H2O interaction with the surface, compared to hydrophilic surfaces. As a consequence the initial nucleation and growth rate of the film varies strongly with temperature and water vapor pressure (on hydrophobic surfaces) for the studied temperature range. (ii) The required mass of water to reach a coherent and completely covering film is much larger on the hydrophobic surface, i.e. the film morphology differs on the two types of surfaces. These differences are also reflected in differences in the phase transition from amorphous to crystallineof the ice film upon heating through the transition temperature. The measurements were primarily done by temperature programmed desorption. Theoretical modeling can semiquantitatively reproduce the nucleation and growth behavior on the hydrophobic substrate.

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

    NASA Technical Reports Server (NTRS)

    Gray, Hugh R.; Ginty, Carol A.

    1992-01-01

    The Advanced High-Temperature Engine Materials Technology Program is described in terms of its research initiatives and its goal of developing propulsion systems for civil aeronautics with low levels of noise, pollution, and fuel consumption. The program emphasizes the analysis and implementation of structural materials such as polymer-matrix composites in fans, casings, and engine-control systems. Also investigated in the program are intermetallic- and metal-matrix composites for uses in compressors and turbine disks as well as ceramic-matrix composites for extremely high-temperature applications such as turbine vanes.

  20. Computer program to analyze multipass pressure-temperature-spinner surveys

    SciTech Connect

    Spielman, Paul

    1994-01-20

    A computer program has been developed to analyze multipass pressure-temperature-spinner surveys and summarize the data in graphical form on two plots: (1) an overlay of spinner passes along with a fluid velocity profile calculated from the spinner and (2) an overlay of pressure, pressure gradient, and temperature profiles from each pass. The program has been written using SmartWare II Software. Fluid velocity is calculated for each data point using a cross-plot of tool speed and spinner counts to account for changing flow conditions in the wellbore. The program has been used successfully to analyze spinner surveys run in geothermal wells with two-phase flashing flow.

  1. First-principles study of water desorption from montmorillonite surface.

    PubMed

    Zhang, Yao; Meng, Yingfeng; Liu, Houbin; Yang, Mingli

    2016-05-01

    Knowledge about water desorption is important to give a full picture of water diffusion in montmorillonites (MMT), which is a driving factor in MMT swelling. The desorption paths and energetics of water molecules from the surface of MMT with trapped Li(+), Na(+) or K(+) counterions were studied using periodic density functional theory calculations. Two paths--surface and vacuum desorption--were designed for water desorption starting from a stationary structure in which water bonds with both the counterion and the MMT surface. Surface desorption is energetically more favorable than vacuum desorption due to water-surface hydrogen bonds that help stabilize the intermediate structure of water released from the counterion. The energy barriers of water desorption are in the order of Li(+) > Na(+) > K(+), which can be attributed to the short ionic radius of Li(+), which favors strong binding with the water molecule. The temperature dependence of water adsorption and desorption rates were compared based on the computed activation energies. Our calculations reveal that the water desorption on the MMT surface has a different mechanism from water adsorption, which results from surface effects favoring stabilization of water conformers during the desorption process. PMID:27083565

  2. Cyclic CO{sub 2} chemisorption–desorption behavior of Na{sub 2}ZrO{sub 3}: Structural, microstructural and kinetic variations produced as a function of temperature

    SciTech Connect

    Martínez-dlCruz, Lorena; Pfeiffer, Heriberto

    2013-08-15

    A structural, microstructural and kinetic analysis of the Na{sub 2}ZrO{sub 3}–CO{sub 2} system was performed over 20 chemisorption–desorption cycles. Different cyclic experiments were performed between 500 and 800 °C. Although the best results were obtained in Na{sub 2}ZrO{sub 3} sample treated at 550 °C, all the samples treated between 500 and 700 °C presented good CO{sub 2} chemisorption efficiencies and stabilities. On the contrary, Na{sub 2}ZrO{sub 3} sample treated at 800 °C presented a continuous decrement of the CO{sub 2} chemisorption. After 20 cycles all the samples presented a partial Na{sub 2}ZrO{sub 3} decomposition, determined by the ZrO{sub 2} formation, which was associated to sodium sublimation. Additionally, the Na{sub 2}ZrO{sub 3} microstructural analysis showed a systematic morphological evolution. It was microscopically observed that Na{sub 2}ZrO{sub 3} particles tend to fracture due to the Na{sub 2}CO{sub 3} formation. Later, after several cycles these tiny fractured particles sinter producing new polyhedral and dense Na{sub 2}ZrO{sub 3}–ZrO{sub 2} particles. Finally, an exhaustive kinetic analysis showed a high CO{sub 2} chemisorption–desorption stability at different temperatures. - Graphical abstract: A CO{sub 2} chemisorption–desorption analysis was performed in the Na{sub 2}ZrO{sub 3}–CO{sub 2} system. Different cyclic experiments were performed between 500 and 800 °C and the results showed high CO{sub 2} chemisorption efficiencies. Nevertheless the Na{sub 2}ZrO{sub 3} composition and microstructure evolved during the cycles. Highlights: • Different CO{sub 2} chemisorption–desorption cycles were performed in the Na{sub 2}ZrO{sub 3} phase. • Na{sub 2}ZrO{sub 3} presents interesting microstructural changes depending on temperature. • At T≤550 °C, Na{sub 2}ZrO{sub 3} presents the best cyclability due to microstructural factors. • At T≥600 °C, Na{sub 2}ZrO{sub 3} presents a partial decomposition after 20 cycles

  3. DESORPTION OF SORBATES FROM MST, MMST, AND CST UNDER VARIOUS CONDITIONS

    SciTech Connect

    Taylor-Pashow, K.; Hobbs, D.

    2011-06-10

    The Small Column Ion Exchange (SCIX) Program (formerly referred to as the Modular Salt Processing (MSP) Project) seeks to deploy equipment to remove the {sup 134,137}Cs, {sup 90}Sr, and alpha-emitting radionuclides (principally {sup 238,239,240}Pu and {sup 237}Np) from the high level waste salt solutions. The equipment is installed within a high level waste tank to take advantage of the shielding provided by the waste tank. The process will involve adding monosodium titanate (MST) to the waste tank (i.e., Tank 41H) to sorb the Sr and select actinides, removing the MST and entrained sludge with in-riser rotary microfilters, and subsequently using ion-exchange columns containing crystalline silicotitanate (CST) to remove the Cs. After being loaded with Cs, the CST will be ground to reduce the particle size and then transferred into another waste tank (e.g., Tank 40H). The MST and sludge solids stream will be transported to a sludge batch preparation tank (i.e., Tank 42H or Tank 51H) once the SCIX batch is processed. Both streams, MST/solids and CST, will ultimately be transported into and vitrified inside the Defense Waste Processing Facility (DWPF). A series of experiments were performed to examine desorption from monosodium titanate (MST), modified monosodium titanate (mMST), and crystalline silicotitanate (CST) under various conditions. The first two experiments examined desorption from MST and CST under two different sludge treatment processes, aluminum dissolution and sludge washing. Desorption of all sorbates was observed to varying degrees under the aluminum dissolution conditions. The extent of desorption ranged from < 3% to about 50% after 4 weeks, with Pu exhibiting the lowest desorption. At the end of the experiment, the temperature was reduced from 65 C to 25 C and the tests monitored for an additional two weeks. After reducing the temperature, partial resorption of the sorbates was observed with both MST and CST. Under the sludge washing conditions, no

  4. Diffusion Analysis Of Hydrogen-Desorption Measurements

    NASA Technical Reports Server (NTRS)

    Danford, Merlin D.

    1988-01-01

    Distribution of hydrogen in metal explains observed desorption rate. Report describes application of diffusion theory to anaylsis of experimental data on uptake and elimination of hydrogen in high-strength alloys of 25 degree C. Study part of program aimed at understanding embrittlement of metals by hydrogen. Two nickel-base alloys, Rene 41 and Waspaloy, and one ferrous alloy, 4340 steel, studied. Desorption of hydrogen explained by distribution of hydrogen in metal. "Fast" hydrogen apparently not due to formation of hydrides on and below surface as proposed.

  5. Field test of manufactured gas plant remediation technologies: Thermal desorption. Final report

    SciTech Connect

    Nakles, D.V.

    1995-11-01

    Thermal desorption uses heat to remove organic contaminants from surfaces (or pores) of solid materials. Desorption occurs when the materials are heated sufficiently to cause the organic fraction to volatilize. Effective temperatures will vary with each compound. High-molecular-weight compounds such as polycyclic aromatic hydrocarbons (PAHs) usually require more heat for desorption than low-molecular-weight compounds such as volatile organic compounds (VOCs). In the United States, thermal desorption technologies have been applied at relatively low temperatures (300-400{degrees}F) to remediate petroleum-contaminated soils. At high temperatures (1100-1400{degrees}F), thermal desorption technology will remediate polychlorinated biphenyls and pesticide-contaminated soils.

  6. [Comparative study on water desorption and thermal desorption of aromatic hydrocarbons in soils].

    PubMed

    Zhang, Wen; Zhang, Yu; Sun, Hong-Wen

    2010-01-01

    In order to develop a new method to study the mobility and bioavailability of organic contaminants in soils, a set of thermal desorption device was established. Water desorption and thermal desorption of toluene and pyrene in three types of soils were investigated. The two desorption occurred as bi-phase, which indicates that the combination states of the aromatic hydrocarbons in soils are different. The desorption was described by the first-order two compartment model and an exponential decay equation. Parameters, such as fast desorption fraction F(rap), water and thermal desorption rate constants, b(w) and b(t) were derived. For toluene, values of F(rap) in three soils were 27.9%, 12.5%, 16.0%, respectively, and 2.4%, 22.0%, and 19.1% for pyrene. Values of b(w) were 0.241, 0.018, 0.038 for toluene and 0.008, 0.013, 0.012 for pyrene. There is a significantly positive correlation relationship between F (rap) and b(w) (toluene: R2 = 0.982; pyrene: R2 = 0.991). At 250 degrees C, values of b(t) in three soils were 0.167, 0.064, 0.141 for toluene, and 0.036, 0.062, 0.047 for pyrene. At 400 degrees C, the corresponding values were 0.429, 0.084, 0.398 for toluene and 0.066, 0.162, 0.153 for pyrene. Meanwhile, the water b(w) shows a good correlation with b(t) at selected temperatures (250 degrees C: R2 = 0.985; 400 degrees C: R2 = 0.848). Moreover, F(rap) is positively correlated with b(t). As F(rap) has been used to predict bioavailability, thermal desorption can therefore be used to predict bioavailability.

  7. Estimating Arrhenius parameters using temperature programmed molecular dynamics

    NASA Astrophysics Data System (ADS)

    Imandi, Venkataramana; Chatterjee, Abhijit

    2016-07-01

    Kinetic rates at different temperatures and the associated Arrhenius parameters, whenever Arrhenius law is obeyed, are efficiently estimated by applying maximum likelihood analysis to waiting times collected using the temperature programmed molecular dynamics method. When transitions involving many activated pathways are available in the dataset, their rates may be calculated using the same collection of waiting times. Arrhenius behaviour is ascertained by comparing rates at the sampled temperatures with ones from the Arrhenius expression. Three prototype systems with corrugated energy landscapes, namely, solvated alanine dipeptide, diffusion at the metal-solvent interphase, and lithium diffusion in silicon, are studied to highlight various aspects of the method. The method becomes particularly appealing when the Arrhenius parameters can be used to find rates at low temperatures where transitions are rare. Systematic coarse-graining of states can further extend the time scales accessible to the method. Good estimates for the rate parameters are obtained with 500-1000 waiting times.

  8. Estimating Arrhenius parameters using temperature programmed molecular dynamics.

    PubMed

    Imandi, Venkataramana; Chatterjee, Abhijit

    2016-07-21

    Kinetic rates at different temperatures and the associated Arrhenius parameters, whenever Arrhenius law is obeyed, are efficiently estimated by applying maximum likelihood analysis to waiting times collected using the temperature programmed molecular dynamics method. When transitions involving many activated pathways are available in the dataset, their rates may be calculated using the same collection of waiting times. Arrhenius behaviour is ascertained by comparing rates at the sampled temperatures with ones from the Arrhenius expression. Three prototype systems with corrugated energy landscapes, namely, solvated alanine dipeptide, diffusion at the metal-solvent interphase, and lithium diffusion in silicon, are studied to highlight various aspects of the method. The method becomes particularly appealing when the Arrhenius parameters can be used to find rates at low temperatures where transitions are rare. Systematic coarse-graining of states can further extend the time scales accessible to the method. Good estimates for the rate parameters are obtained with 500-1000 waiting times. PMID:27448871

  9. Beryllium Desorption from Sediments

    NASA Astrophysics Data System (ADS)

    Boschi, V.; Willenbring, J. K.

    2015-12-01

    Beryllium isotopes have provided a useful tool in the field of geochronology and geomorphology over the last 25 years. The amount of cosmogenic meteoric 10Be and native 9Be absorbed to soils often scales with the residence time and chemical weathering of sediments in a landscape, respectively. Thus, the concentrations in river sediment may be used to quantify the denudation of specific watersheds. When deposited in ocean sediment, these concentrations are thought to record the history of denudation on Earth over the last ~10 Ma. The use of both isotopes often relies on the premise of beryllium retention to sediment surfaces in order to preserve a landscape's erosion and weathering signature. Changes in setting, en route from the soil to fluvial system to the ocean, can cause beryllium desorption and may preclude some applications of the 10Be/9Be system. Four mechanisms were tested to determine the desorption potential of beryllium including a reduction in pH, an increase in ionic strength and complexation with soluble organic and inorganic species. These processes have the potential to mobilize beryllium into solution. For example, by both reducing the pH and increasing the ionic strength, competition for adsorption sites increases, potentially liberating beryllium from the sediment surface. In addition, organic and inorganic ligands can complex beryllium causing it to become mobilized. To determine which of these alterations influence beryllium desorption and to quantify the effect, we prepared separate solutions of beryllium bound to minerals and organic compounds and measured beryllium concentrations in solution before and after adjusting the pH, ionic strength, and changing inorganic and organic ligand concentrations. We conclude from our observations that overall, beryllium sorbed to organic compounds was more resistant to desorption relative to mineral-associated beryllium. Among the methods tested, a reduction in pH resulted in the greatest amount of

  10. Hydrogenation of CO-bearing species on grains: unexpected chemical desorption of CO

    NASA Astrophysics Data System (ADS)

    Minissale, M.; Moudens, A.; Baouche, S.; Chaabouni, H.; Dulieu, F.

    2016-05-01

    The amount of methanol in the gas phase and the CO depletion from the gas phase are still open problems in astrophysics. In this work, we investigate solid-state hydrogenation of CO-bearing species via H-exposure of carbon monoxide, formaldehyde, and methanol-thin films deposited on cold surfaces, paying attention to the possibility of a return to the gas phase. The products are probed via infrared spectroscopy (reflection absorption infrared spectroscopy), and two types of mass spectroscopy protocols: temperature-programmed desorption, and during-exposure desorption techniques. In the case of the [CO+H] reactive system, we have found that chemical desorption of CO is more efficient than H-addition reactions and HCO and H2CO formation; the studies of the [H2CO +H] reactive system show a strong competition between all surface processes, chemical desorption of H2CO, H-addition (CH3OH formation) and H-abstraction (CO formation); finally, [CH3OH + H] seems to be a non-reactive system and chemical desorption of methanol is not efficient. CO-bearing species present a see-saw mechanism between CO and H2CO balanced by the competition of H-addition and H2-abstraction that enhances the CO chemical desorption. The chemical network leading to methanol has to be reconsidered. The methanol formation on the surface of interstellar dust grain is still possible through CO+H reaction; nevertheless, its consumption of adsorbed H atoms should be higher than previously expected.

  11. High-pressure temperature-programmed reduction of sulfided catalysts

    SciTech Connect

    Labruyere, F.; Lacroix, M.; Breysse, M.

    1997-04-15

    Temperature-programmed reduction (TPR) of solids materials is a widely used technique of characterization in heterogeneous catalysis. So far all studies dealing with this technique have been carried out at ambient or subambient pressure. Because most catalytic processes are performed at higher hydrogen pressures, the impact of this technique could be enhanced by the development of a new generation of equipment working under conditions approaching those used in reality. This work describes a new experimental temperature-programmed reduction set-up working at hydrogen pressures above 1 atm. Basic hydrodynamic considerations have been employed for correcting the signal from the variations of the residence time distribution of the molecules in the reactor. Model and industrial sulfide catalysts were studied at various pressures. When the raw signals are suitably corrected, it appears that the hydrogen pressure does not influence the TPR patterns. 25 refs., 7 figs.

  12. Programmed temperature vaporizing injector to filter off disturbing high boiling and involatile material for on-line high performance liquid chromatography gas chromatography with on-column transfer.

    PubMed

    Biedermann, Maurus; Grob, Koni

    2013-03-15

    Insertion of a programmed temperature vaporizing (PTV) injector under conditions of concurrent solvent recondensation (CSR) into the on-line HPLC-GC interface for on-column transfer (such as the retention gap technique with partially concurrent eluent evaporation) enables filtering off high boiling or involatile sample constituents by a desorption temperature adjusted to the required cut-off. Details of this technique were investigated and optimized. Memory effects, observed when transferred liquid was sucked backwards between the transfer line and the wall of the injector liner, can be kept low by a small purge flow rate through the transfer line at the end of the transfer and the release of the liquid through a narrow bore capillary kept away from the liner wall. The column entrance should be within the well heated zone of the injector to prevent losses of solute material retained on the liner wall during the splitless period. The desorption temperature must be maintained until an elevated oven temperature is reached to prevent peak broadening resulting of a cool inlet section in the bottom part of the injector.

  13. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that 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 the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. 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 that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  14. Accelerated Molecular Dynamics Simulation of Alkane Desorption

    NASA Astrophysics Data System (ADS)

    McLaughlin, Kelly; Fichthorn, Kristen

    2006-03-01

    Thermal desorption has been the focus of much surface science research. Studies of alkanes on graphite^1 and gold^2 have shown prefactors that are constant with alkane chain length but vary by over six orders of magnitude. Other studies on magnesium oxide^3 and gold^4 show a prefactor that increases with increasing chain length. We have developed an all-atom model to study alkane desorption from graphite. Transition state theory is used to obtain rate constants from the simulation. Accelerated MD is used to extend the desorption simulation to experimentally relevant temperatures. Our results show a prefactor that increases with increasing chain length. We predict that it will become constant as internal conformational changes occur significantly. We examine the effect of desorption environment through varying the alkane surface coverage. 1. K.R. Paserba and A.J. Gellman, J. Chem. Phys. 115, 6737 (2001). 2. S.M. Wetterer et al., J. Phys. Chem. 102, 9266 (1998). 3. S.L. Tait et al., J. Chem. Phys. 122, 164707 (2005). 4. K.A. Fichthorn and R.A. Miron, Phys. Rev. Lett. 89, 196103 (2002).

  15. 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.

  16. Calcium lignosulfonate adsorption and desorption on Berea sandstone.

    PubMed

    Grigg, Reid B; Bai, Baojun

    2004-11-01

    This paper describes adsorption and desorption studies carried out with calcium lignosulfonate (CLS) on Berea sandstone. Circulation experiments were performed to determine CLS adsorption isotherms and the effects of CLS concentration, temperature, salinity, brine hardness, and injection rate on adsorption density. Flow-through experiments were performed to assess the reversibility of CLS adsorption and the influence of postflush rate, brine concentration, brine hardness, brine pH, and temperature on the desorption process. Results indicate that CLS adsorption isotherms on Berea sandstone follow the Freundlich isotherm law. The results presented in this paper on the effects of CLS adsorption and desorption on Berea sandstone show that: (1) increasing CLS concentration and salinity increases CLS adsorption density; (2) increasing temperature will decrease adsorption density; (3) increasing injection rate of CLS solution will slightly decrease CLS adsorption density; (4) postflush rate and salinity of brine have a large impact on the CLS desorption process; (5) the adsorption and desorption process are not completely reversible; and (5) temperature and pH of the postflush brine have little effect on desorption.

  17. Cooled High-temperature Radial Turbine Program 2

    NASA Technical Reports Server (NTRS)

    Snyder, Philip H.

    1991-01-01

    The objective of this program was the design and fabrication of a air-cooled high-temperature radial turbine (HTRT) intended for experimental evaluation in a warm turbine test facility at the LeRC. The rotor and vane were designed to be tested as a scaled version (rotor diameter of 14.4 inches diameter) of a 8.021 inch diameter rotor designed to be capable of operating with a rotor inlet temperature (RIT) of 2300 F, a nominal mass flow of 4.56 lbm/sec, a work level of equal or greater than 187 Btu/lbm, and efficiency of 86 percent or greater. The rotor was also evaluated to determine it's feasibility to operate at 2500 F RIT. The rotor design conformed to the rotor blade flow path specified by NASA for compatibility with their test equipment. Fabrication was accomplished on three rotors, a bladeless rotor, a solid rotor, and an air-cooled rotor.

  18. Multiyear Program Plan for the High Temperature Materials Laboratory

    SciTech Connect

    Arvid E. Pasto

    2000-03-17

    Recently, the U.S. Department of Energy's (DOE) Office of Heavy Vehicle Technologies (OHVT) prepared a Technology Roadmap describing the challenges facing development of higher fuel efficiency, less polluting sport utility vehicles, vans, and commercial trucks. Based on this roadmap, a multiyear program plan (MYPP) was also developed, in which approaches to solving the numerous challenges are enumerated. Additional planning has been performed by DOE and national laboratory staff, on approaches to solving the numerous challenges faced by heavy vehicle system improvements. Workshops and planning documents have been developed concerning advanced aerodynamics, frictional and other parasitic losses, and thermal management. Similarly, the Heavy Vehicle Propulsion Materials Program has developed its own multiyear program plan. The High Temperature Materials Laboratory, a major user facility sponsored by OHVT, has now developed its program plan, described herein. Information was gathered via participation in the development of OHVT's overall Technology Roadmap and MYPP, through personal contacts within the materials-user community, and from attendance at conferences and expositions. Major materials issues for the heavy vehicle industry currently center on trying to increase efficiency of (diesel) engines while at the same time reducing emissions (particularly NO{sub x} and particulates). These requirements dictate the use of increasingly stronger, higher-temperature capable and more corrosion-resistant materials of construction, as well as advanced catalysts, particulate traps, and other pollution-control devices. Exhaust gas recirculation (EGR) is a technique which will certainly be applied to diesel engines in the near future, and its use represents a formidable challenge, as will be described later. Energy-efficient, low cost materials processing methods and surface treatments to improve wear, fracture, and corrosion resistance are also required.

  19. OTEC gas desorption studies

    NASA Astrophysics Data System (ADS)

    Chen, F. C.; Golshani, A.

    1982-02-01

    Experiments on deaeration in packed columns and barometric intake systems, and with hydraulic air compression for open-cycle OTEC systems are reported. A gas desorption test loop consisting of water storage tanks, a vacuum system, a liquid recirculating system, an air supply, a column test section, and two barometric leg test sections was used to perform the tests. The aerated water was directed through columns filled with either ceramic Raschig rings or plastic pall rings, and the system vacuum pressure, which drives the deaeration process, was found to be dependent on water velocity and intake pipe height. The addition of a barometric intake pipe increased the deaeration effect 10%, and further tests were run with lengths of PVC pipe as potential means for noncondensibles disposal through hydraulic air compression. Using the kinetic energy from the effluent flow to condense steam in the noncondensible stream improved the system efficiency.

  20. Thermal desorption of deuterium implanted into beryllium

    SciTech Connect

    Markin, A.V.; Chernikov, V.N.; Zakharov, A.P.

    1995-09-01

    By means of TDS measurements it is shown that the desorption of deuterium from Be implanted with 5 keV D ions to fluences, {Phi}, from 1x10{sup 20} D/m{sup 2} to 1x10{sup 21} D/m{sup 2} proceeds in one high temperature stage B, while at {Phi} {ge} 1.2x10{sup 21}D/m{sup 2} one more stage A is added. The desorption maximum A is narrow and consists of two peaks A{sub 1} and A{sub 2} at about 460 K and 490 K, respectively. Peak A{sub 1} is attributed to the desorption of deuterium from the walls of opened channels formed under D ion implantation. Peak {sub A}2 is a consequence of the opening of a part of closed bubbles/channels to the outer surface. The position of maximum B shifts noticeably and nonsteadily on the fluence in a range from 850 to 1050 K. The origin of this maximum is the liberation of D atoms bound at vacancy complexes discussed previously by Wampler. The dependence of Tm(B) on the fluence is governed by the interaction of freely migrating D atoms with partly opened or fully closed gas cavity arrangements which are created under temperature ramping, but differently in specimens implanted with D ions to different fluences.

  1. Desorption Dynamics, Internal Energies and Imaging of Organic Molecules from Surfaces with Laser Desorption and Vacuum Ultraviolet (VUV) Photoionization

    SciTech Connect

    Kostko, Oleg; Takahashi, Lynelle K.; Ahmed, Musahid

    2011-04-05

    There is enormous interest in visualizing the chemical composition of organic material that comprises our world. A convenient method to obtain molecular information with high spatial resolution is imaging mass spectrometry. However, the internal energy deposited within molecules upon transfer to the gas phase from a surface can lead to increased fragmentation and to complications in analysis of mass spectra. Here it is shown that in laser desorption with postionization by tunable vacuum ultraviolet (VUV) radiation, the internal energy gained during laser desorption leads to minimal fragmentation of DNA bases. The internal temperature of laser-desorbed triacontane molecules approaches 670 K, whereas the internal temperature of thymine is 800 K. A synchrotron-based VUV postionization technique for determining translational temperatures reveals that biomolecules have translational temperatures in the range of 216-346 K. The observed low translational temperatures, as well as their decrease with increased desorption laser power is explained by collisional cooling. An example of imaging mass spectrometry on an organic polymer, using laser desorption VUV postionization shows 5 mu m feature details while using a 30 mu m laser spot size and 7 ns duration. Applications of laser desorption postionization to the analysis of cellulose, lignin and humic acids are briefly discussed.

  2. 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.

  3. Femtosecond laser pulse induced desorption: A molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Lončarić, Ivor; Alducin, Maite; Saalfrank, Peter; Juaristi, J. Iñaki

    2016-09-01

    In recent simulations of femtosecond laser induced desorption of molecular oxygen from the Ag(110) surface, it has been shown that depending on the properties (depth and electronic environment) of the well in which O2 is adsorbed, the desorption can be either induced dominantly by hot electrons or via excitations of phonons. In this work we explore whether the ratios between the desorption yields from different adsorption wells can be tuned by changing initial surface temperature and laser pulse properties. We show that the initial surface temperature is an important parameter, and that by using low initial surface temperatures the electronically mediated process can be favored. In contrast, laser properties seem to have only a modest influence on the results.

  4. Effect of high-temperature on high-performance liquid chromatography column stability and performance under temperature-programmed conditions.

    PubMed

    Marin, Stephanie J; Jones, Brian A; Felix, W Dale; Clark, Jody

    2004-03-19

    Six commercially available analytical (4.1 or 4.6 mm i.d.) columns were evaluated under temperature-programmed high-temperature liquid chromatography (HTLC) conditions to access their stability and performance at extreme temperatures. Seven components consisting of acidic, basic and neutral compounds were analyzed under temperature-programmed conditions and solvent gradient conditions using three different mobile phase compositions (acidic, basic and neutral). Each column was checked with a two-component test mix at various stages of the evaluation to look for signs of stationary phase collapse. Three zirconia based stationary phases studied exhibited column bleed under temperature-programmed conditions. The other three columns, a polydentate silica column, a polystyrene-divinylbenzene (PS-DVB) polymeric column, and a graphitic carbon column performed well with no evidence of stationary phase degradation. The R.S.D. for the retention times and efficiencies were less than 10% for most conditions, and not more than 15% during the course of the evaluation for each column. The polydentate silica stationary phase was temperature programmed to 100 degrees C, the PS-DVB stationary phase was temperature programmed up to 150 degrees C, and the graphitic carbon column was used with temperature programming up to 200 degrees C. Comparable peak capacities and similar retention behaviors were observed under solvent gradient and temperature-programmed conditions. Temperature programming with dynamic mobile phase preheating can replace solvent gradient analysis without a loss of peak capacity when used with 4.1 or 4.6 mm columns. PMID:15043277

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

    SciTech Connect

    Senevirathna, W. U.; Zhang, Hong; Gu, Baohua

    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.

  6. HYDROGEN AND ITS DESORPTION IN RHIC.

    SciTech Connect

    HSEUH,H.C.

    2002-11-11

    Hydrogen is the dominating gas specie in room temperature, ultrahigh vacuum systems of particle accelerators and storage rings, such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. Rapid pressure increase of a few decades in hydrogen and other residual gases was observed during RHIC's recent high intensity gold and proton runs. The type and magnitude of the pressure increase were analyzed and compared with vacuum conditioning, beam intensity, number of bunches and bunch spacing. Most of these pressure increases were found to be consistent with those induced by beam loss and/or electron stimulated desorption from electron multipacting.

  7. Structural analysis and identification of gel-purified proteins, available in the femtomole range, using a novel computer program for peptide sequence assignment, by matrix-assisted laser desorption ionization-reflectron time-of-flight-mass spectrometry.

    PubMed

    Gevaert, K; Verschelde, J L; Puype, M; Van Damme, J; Goethals, M; De Boeck, S; Vandekerckhove, J

    1996-05-01

    A procedure is described for structural characterization and identification of proteins, purified by either one- or two-dimensional gel electrophoresis in the low picomole to femtomole range. The purified proteins are first detected in the primary gels by the sensitive reverse staining procedure described by Fernandez-Patron et al. (Anal. Biochem. 1995, 224, 203-211) and consecutively reeluted from combined get pieces and concentrated in the tip of a Pasteur pipette in a secondary gel matrix consisting of either sodium dodecyl sulfate-polyacrylamide or agarose. The concentrated proteins are in-matrix-digested and the resulting peptides are separated by reverse-phase high performance liquid chromatography (HPLC) combined with microsequencing or analyzed by matrix-assisted laser desorption ionization--time of flight--mass spectrometry. Protein identification is based on sequence homology or on the peptide mass pattern. The matching peptide sequences can additionally be verified by matching their measured post-source decay spectra with the calculated fragmentation patterns of the isobaric candidate peptides appearing on the search list. This is done by a computer program referred to as MassFrag, described in this paper. We demonstrate that it is possible to identify protein that are only available in the femtomole range and whose sequences are stored in nonredundant protein databases or nucleotide and expressed sequence tag databases.

  8. Feasibility of the direct coupling of solid-phase extraction-pipette tips with a programmed-temperature vaporiser for gas chromatographic analysis of drugs in plasma.

    PubMed

    van Hout, M W J; van Egmond, W M A; Franke, J P; de Zeeuw, R A; de Jong, G J

    2002-01-01

    Solid-phase extraction-pipette tips (SPE-PTs) were used for micro solid-phase extraction of lidocaine and diazepam from plasma. Off-line extraction was followed by on-line desorption. On-line desorption was carried out by direct coupling of the SPE-PTs with the liner of the programmed-temperature vaporiser. This coupling only required shortening of the liner by maximally 16 mm, cutting the SPE-PT, and equipping the remaining part with two O-rings. Due to the heating of the injector the SPE-PTs were heated as well, which resulted in a significant amount of impurities. Pre-heating and pre-washing was performed prior to the extraction to reduce the impurity level. The internal coupling device was applied successfully for the analysis of plasma samples with gas chromatography (GC) and mass-selective detection. Detection limits of 0.75 ng/ml and 2.5 ng/ml were obtained for lidocaine and diazepam, respectively, using 200 microl plasma. Recoveries for both compounds were about 80%. Although it is possible, the internal coupling device was not developed to be used as such. The main goal of this coupling was to show the feasibility of the integration of SPE-PTs with GC and to realize an important step to new automated SPE-GC systems. PMID:11824396

  9. 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

  10. 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.

  11. 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.

  12. Defect annealing and thermal desorption of deuterium in low dose HFIR neutron-irradiated tungsten

    SciTech Connect

    Masashi Shimada; M. Hara; T. Otsuka; Y. Oya; Y. Hatano

    2014-05-01

    Accurately estimating tritium retention in plasma facing components (PFCs) and minimizing its uncertainty are key safety issues for licensing future fusion power reactors. D-T fusion reactions produce 14.1 MeV neutrons that activate PFCs and create radiation defects throughout the bulk of the material of these components. Recent studies show that tritium migrates and is trapped in bulk (>> 10 µm) tungsten beyond the detection range of nuclear reaction analysis technique [1-2], and thermal desorption spectroscopy (TDS) technique becomes the only established diagnostic that can reveal hydrogen isotope behavior in in bulk (>> 10 µm) tungsten. Radiation damage and its recovery mechanisms in neutron-irradiated tungsten are still poorly understood, and neutron-irradiation data of tungsten is very limited. In this paper, systematic investigations with repeated plasma exposures and thermal desorption are performed to study defect annealing and thermal desorption of deuterium in low dose neutron-irradiated tungsten. Three tungsten samples (99.99 at. % purity from A.L.M.T. Co., Japan) irradiated at High Flux Isotope Reactor at Oak Ridge National Laboratory were exposed to high flux (ion flux of (0.5-1.0)x1022 m-2s-1 and ion fluence of 1x1026 m-2) deuterium plasma at three different temperatures (100, 200, and 500 °C) in Tritium Plasma Experiment at Idaho National Laboratory. Subsequently, thermal desorption spectroscopy (TDS) was performed with a ramp rate of 10 °C/min up to 900 °C, and the samples were annealed at 900 °C for 0.5 hour. These procedures were repeated three (for 100 and 200 °C samples) and four (for 500 °C sample) times to uncover damage recovery mechanisms and its effects on deuterium behavior. The results show that deuterium retention decreases approximately 90, 75, and 66 % for 100, 200, and 500 °C, respectively after each annealing. When subjected to the same TDS recipe, the desorption temperature shifts from 800 °C to 600 °C after 1st annealing

  13. Ultraviolet Photon-Induced Desorption and Decomposition Kinetics and Dynamics of Methyl Nitrite on SILVER(111)

    NASA Astrophysics Data System (ADS)

    Pressley, Laura Ann

    The wavelength-dependent cross section for decomposition and surface fragment reaction mechanisms for the photon -induced decomposition of CH_3ONO on Ag(111) are determined using the surface analytical techniques of temperature programmed desorption with mass spectroscopy (TPD), x-ray and ultraviolet photoelectron spectroscopy (XPS and UPS, respectively), residual gas analysis with mass spectroscopy (RGA), and secondary ion mass spectroscopy (SIMS). Methyl nitrite adsorbs reversibly on Ag(111) at 100 K with monolayer and multilayer desorption occurring at 131 and 118 K, respectively. The major photodecomposition fragments formed at 100 K include O(a), CH_2 (a), CH_3(a), CH _2O(a), and CH_3O(a). Upon heating to 350 K, these fragments recombine and desorb as H_2 and CH_2OHCH=O. The desorption channel at 350 K accounts for ~ 85% of the available fragments retained on the surface. The remaining fragments react and desorb as CH_3 OCH=O and CH_2OHCH=O at 200 K and 250 K, respectively. The photon-induced desorption dynamics of the nascent fragment, NO, is determined using time-of-flight mass spectroscopy (TOF). At 254, 308, and 313 nm, the translational energy distributions of the desorbing NO is measured at 100 K. Two desorption channels are observed in the TOF spectra at all wavelengths investigated. Irrespective of the excitation wavelength, the flux-weighted mean translational energy, < E_{trans }>/2k, of the slower channel is around 115 +/- 10 K. We propose that this channel results from an extended interaction of the NO with the Ag(111) surface. The measured < E_{trans}>/2k of the faster desorption channel of the nascent NO photofragment at 254, 308, and 351 nm is 1980 +/- 100 K, 617 +/- 100 K, and 846 +/- 100 K, respectively. Comparison of the surface and gas phase photochemical kinetics and dynamics indicates that the dominant photodecomposition mechanism on the Ag(111) surface is the direct absorbance of the photon by the adsorbate.

  14. Mechanistic characterization of adsorption and slow desorption of phenanthrene aged in soils

    SciTech Connect

    Abdul Abu; Steve Smith

    2006-09-01

    Long-term adsorption of phenanthrene to soils was characterized in a silt-loam (LHS), a sandy soil (SBS) from an uncontaminated area of a former coal treatment facility in the north of England and a podzolized soil (CNS) by use of the Polanyi-Manes model, a Langmuir-type model, and a black carbon-water distribution coefficient (K{sub BC}) at a relative aqueous concentration (C{sub e}/S{sub w}) of 0.002 - 0.32. Aqueous desorption kinetic tests and temperature-programmed desorption (TPD) were also used to evaluate phenanthrene diffusivities and desorption activation energies. Adsorption contribution in soils was 48-70% after 30 days and 64-95% after 270 days. Significant increases in adsorption capacity with aging suggest that accessibility of phenanthrene to fractions of SBS soil matrix was controlled by sorptive diffusion at narrow meso- and micropore constrictions. Similar trends were not significant for LHS silt-loam or CNS podzol. Analysis of TPD profiles reveal desorption activation energies of 35-53 kJ/mol and diffusivities of 1.6 x 10{sup -7-}9.7 10{sup -8} cm{sup 2}/s. TPD tests also indicate that the fraction of phenanthrene mass not diffusing from soils was located within micropores and narrow width mesopores with a corresponding volume of 1.83 10{sup -5-}6.3710{sup -5} cm{sup 3}/g. These values were consistent with the modeled adsorption contributions, thus demonstrating the need for such complimentary analytical approach in the risk assessment of organic contaminants. 41 refs., 2 figs., 4 tabs.

  15. 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.

  16. Candida guilliermondii and Other Species of Candida Misidentified as Candida famata: Assessment by Vitek 2, DNA Sequencing Analysis, and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry in Two Global Antifungal Surveillance Programs

    PubMed Central

    Woosley, Leah N.; Diekema, Daniel J.; Jones, Ronald N.; Pfaller, Michael A.

    2013-01-01

    Candida famata (teleomorph Debaryomyces hansenii) has been described as a medically relevant yeast, and this species has been included in many commercial identification systems that are currently used in clinical laboratories. Among 53 strains collected during the SENTRY and ARTEMIS surveillance programs and previously identified as C. famata (includes all submitted strains with this identification) by a variety of commercial methods (Vitek, MicroScan, API, and AuxaColor), DNA sequencing methods demonstrated that 19 strains were C. guilliermondii, 14 were C. parapsilosis, 5 were C. lusitaniae, 4 were C. albicans, and 3 were C. tropicalis, and five isolates belonged to other Candida species (two C. fermentati and one each C. intermedia, C. pelliculosa, and Pichia fabianni). Additionally, three misidentified C. famata strains were correctly identified as Kodomaea ohmeri, Debaryomyces nepalensis, and Debaryomyces fabryi using intergenic transcribed spacer (ITS) and/or intergenic spacer (IGS) sequencing. The Vitek 2 system identified three isolates with high confidence to be C. famata and another 15 with low confidence between C. famata and C. guilliermondii or C. parapsilosis, displaying only 56.6% agreement with DNA sequencing results. Matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) results displayed 81.1% agreement with DNA sequencing. One strain each of C. metapsilosis, C. fermentati, and C. intermedia demonstrated a low score for identification (<2.0) in the MALDI Biotyper. K. ohmeri, D. nepalensis, and D. fabryi identified by DNA sequencing in this study were not in the current database for the MALDI Biotyper. These results suggest that the occurrence of C. famata in fungal infections is much lower than previously appreciated and that commercial systems do not produce accurate identifications except for the newly introduced MALDI-TOF instruments. PMID:23100350

  17. Method of enhancing selective isotope desorption from metals

    DOEpatents

    Knize, Randall J.; Cecchi, Joseph L.

    1984-01-01

    A method of enhancing the thermal desorption of a first isotope of a diatomic gas from a metal comprises the steps of (a) establishing a partial pressure of a second isotope of the diatomic gas in vicinity of the metal; heating the metal to a temperature such that the first isotope is desorbed from the metal; and reducing the partial pressure of the desorbed first isotope while maintaining the partial pressure of the second isotope substantially constant. The method is especially useful for enhancing the desorption of tritium from the Zr-Al getter in a plasma confinement device.

  18. Revisited reaction-diffusion model of thermal desorption spectroscopy experiments on hydrogen retention in material

    SciTech Connect

    Guterl, Jerome Smirnov, R. D.; Krasheninnikov, S. I.

    2015-07-28

    Desorption phase of thermal desorption spectroscopy (TDS) experiments performed on tungsten samples exposed to flux of hydrogen isotopes in fusion relevant conditions is analyzed using a reaction-diffusion model describing hydrogen retention in material bulk. Two regimes of hydrogen desorption are identified depending on whether hydrogen trapping rate is faster than hydrogen diffusion rate in material during TDS experiments. In both regimes, a majority of hydrogen released from material defects is immediately outgassed instead of diffusing deeply in material bulk when the evolution of hydrogen concentration in material is quasi-static, which is the case during TDS experiments performed with tungsten samples exposed to flux of hydrogen isotopes in fusion related conditions. In this context, analytical expressions of the hydrogen outgassing flux as a function of the material temperature are obtained with sufficient accuracy to describe main features of thermal desorption spectra (TDSP). These expressions are then used to highlight how characteristic temperatures of TDSP depend on hydrogen retention parameters, such as trap concentration or activation energy of detrapping processes. The use of Arrhenius plots to characterize retention processes is then revisited when hydrogen trapping takes place during TDS experiments. Retention processes are also characterized using the shape of desorption peaks in TDSP, and it is shown that diffusion of hydrogen in material during TDS experiment can induce long desorption tails visible aside desorption peaks at high temperature in TDSP. These desorption tails can be used to estimate activation energy of diffusion of hydrogen in material.

  19. Formation of a knudsen layer in electronically induced desorption

    NASA Astrophysics Data System (ADS)

    Sibold, D.; Urbassek, H. M.

    1992-10-01

    For intense desorption fluxes, particles desorbed by electronic transitions (DIET) from a surface into a vacuum may thermalize in the gas cloud forming above the surface. In immediate vicinity to the surface, however, a non-equilibrium layer (the Knudsen layer) exists which separates the recently desorbed, non-thermal particles from the thermalized gas cloud. We investigate by Monte Carlo computer simulation the time it takes to form a Knudsen layer, and its properties. It is found that a Knudsen layer, and thus also a thermalized gas cloud, is formed after around 200 mean free flight times of the desorbing particles, corresponding to a desorption of 20 monolayers. At the end of the Knudsen layer, the gas density will be higher, and the flow velocity and temperature smaller, than literature values indicate for thermal desorption. These data are of fundamental interest for the modeling of gas-kinetic and gas-dynamic effects in DIET.

  20. A Non-linear Temperature-Time Program for Non-isothermal Kinetic Measurements

    NASA Astrophysics Data System (ADS)

    Sohn, Hong Yong

    2016-04-01

    A new temperature-time program for non-isothermal measurements of chemical reaction rates has been developed. The major advantages of the proposed temperature-time function are twofold: Firstly, the analysis of kinetic information in the high temperature range of the measurement is improved over the conventional linear temperature program by slowing the rate of temperature increase in the high temperature range and secondly, the new temperature program greatly facilitates the data analysis by providing a closed-form solution of the temperature integral and allows a convenient way to obtain the kinetic parameters by eliminating the need for the approximate evaluation of the temperature integral. The procedures for applying the new temperature-time program to the analysis of experimental data are demonstrated in terms of the determination of the kinetic parameters based on the selection of a suitable conversion function in the rate equation as well as the direct determination of activation energy at different conversion extents without the need for a conversion function. The rate analysis based on the new temperature program is robust and does not appear to be sensitive to errors in experimental measurements.

  1. Erbium hydride thermal desorption : controlling kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2007-08-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

  2. Space exploration with a solar sail coated by materials that undergo thermal desorption

    NASA Astrophysics Data System (ADS)

    Kezerashvili, Roman Ya.

    2015-12-01

    For extrasolar space exploration it is suggested to use space environmental effects such as solar radiation heating to accelerate a solar sail coated by materials that undergo thermal desorption at a particular temperature. The developed approach allows the perihelion of the solar sail orbits to be determined based on the temperature requirement for the solar sail materials. Our study shows that the temperature of a solar sail increases as r - 2 / 5 when the heliocentric distance r decreases. The proposed sail has two coats of the materials that undergo desorption at different solar sail temperatures depending on the heliocentric distance. The first desorption occurs at the Earth orbit and provides the thrust needed to propel the solar sail toward the Sun. When the solar sail approaches the Sun, its temperature increases, and the second coat undergoes desorption at the perihelion of the heliocentric escape orbit. This provides a second thrust and boosts the solar sail to its escape velocity.

  3. High-temperature oxidation and corrosion of materials program

    SciTech Connect

    Whittle, D.P.

    1980-03-01

    Research progress is reported in the behavior of metals and alloys in gas mixtures at high temperature, corrosion mechanisms in complex environments of low oxidizing potential, hot corrosion of nickel-base alloys at intermediate temperatures, corrosion of solid sulfate deposits, adherence of Al/sub 2/O/sub 3/ oxide films, oxidation behavior of a two-phase alloy Fe-44% Cu, and formation of subscales of varying composition. (FS)

  4. 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).

  5. Adsorption and desorption studies of cesium on sapphire surfaces

    SciTech Connect

    Zavadil, K.R.; Ing, J.L.

    1993-12-01

    Adsorption/desorption were studied using combined surface analytical techniques. An approximate initial sticking coefficient for Cs on sapphire was measured using reflection mass spectrometry and found to be 0.9. Thermal Desorption Mass Spectrometry (TDMS) and Auger Electron Spectroscopy (AES) were used to verify that a significant decrease in sticking coefficient occurs as the Cs coverage reaches a critical submonolayer value. TDMS analysis demonstrates that Cs is stabilized on a clean sapphire surface at temperatures (1200 K) in excess of the temperatures experienced by sapphire in a TOPAZ-2 thermionic fuel element (TFE). Surface contaminants on sapphire can enhance Cs adsorption relative to the clean surface. C contamination eliminates the high temperature state of Cs desorption found on clean sapphire but shifts the bulk of the C desorption from 400 to 620 K. Surface C is a difficult contaminant to remove from sapphire, requiring annealing above 1400 K. Whether Cs is stabilized on sapphire in a TFE environment will most likely depend on relation between surface contamination and surface structure.

  6. Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on TiO2(110)

    SciTech Connect

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

    2014-07-17

    The adsorption, desorption, and displacement kinetics of H2O and CO2 on TiO2(110) are investigated using temperature programmed desorption (TPD) and molecular beam techniques. The TPD spectra for both H2O and CO2 have well-resolved peaks corresponding to desorption from bridge-bonded oxygen (BBO), Ti, and oxygen vacancies (VO) sites in order of increasing peak temperature. Analysis of the saturated monolayer peak for both species reveals that the corresponding adsorption energies on all sites are greater for H2O and for CO2. Sequential dosing of H2O and CO2 reveals that, independent of the dose order, H2O molecules will displace CO2 in order to occupy the highest energy binding sites available. Isothermal experiments show that the displacement of CO2 by H2O occurs between 75 and 80 K. Further analysis shows that a ratio of 4 H2O to 3 CO2 molecules is needed to displace CO2 from the TiO2(110) surface.

  7. OTEC gas-desorption studies

    SciTech Connect

    Chen, F.C.; Golshani, A.

    1981-01-01

    OTEC gas desorption studies were initiated with the goal of mitigating these effects and were carried out in four areas: (1) vacuum deaeration in a packed column, (2) deaeration in a barometric water intake system, (3) noncondensibles disposal through hydraulic air compression, and (4) OTEC deaeration subsystems' analysis. Laboratory experiments to date have completed the vacuum deaeration test of three different kinds of packings, barometric intake deaeration experiments, and a series of hydraulic air compression tests. Preliminary analyses based on the experimental data have shown that, as compared to the previous baseline study, reduction both in deaerator cost and pumping power can be realized with a combination of barometric intake and packed column deaeration. The design and operation of the gas desorption test loop, experimental and computer simulation results obtained, and an analysis of OTEC deaeration subsystem design based on the test results and their implication on OTEC open-cycle power systems are presented.

  8. 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

  9. Low-temperature resource assessment program. Final report

    SciTech Connect

    Lienau, P.J.; Ross, H.

    1996-02-01

    The US Department of Energy - Geothermal Division (DOE/GD) recently sponsored the Low-Temperature Resource Assessment project to update the inventory of the nation`s low- and moderate-temperature geothermal resources and to encourage development of these resources. A database of 8,977 thermal wells and springs that are in the temperature range of 20{degrees}C to 150{degrees}C has been compiled for ten western states, an impressive increase of 82% compared to the previous assessments. The database includes location, descriptive data, physical parameters, water chemistry and references for sources of data. Computer-generated maps are also available for each state. State Teams have identified 48 high-priority areas for near-term comprehensive resource studies and development. Resources with temperatures greater than 50{degrees}C located within 8 km of a population center were identified for 271 collocated cities. Geothermal energy cost evaluation software has been developed to quickly identify the cost of geothermally supplied heat to these areas in a fashion similar to that used for conventionally fueled heat sources.

  10. 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.

  11. Desorption of pyrethroids from suspended solids.

    PubMed

    Fojut, Tessa L; Young, Thomas M

    2011-08-01

    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 the present 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 r(2)  > 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 1 d before were used in the experiments to compare desorption rates for field-applied pyrethroids with those for laboratory-spiked materials. Suspended solids were used in desorption experiments because suspended solids can be a key source of hydrophobic compounds in surface waters. The rapid desorption rate parameters of field-applied permethrin were not statistically different from those of laboratory spiked permethrin, indicating that desorption of the spiked pyrethroids is comparable to desorption of the pyrethroids 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 compared to aging for 1 d and 7 d, whereas desorption in the rapid and slow compartments did not differ between these treatments.

  12. 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.

  13. DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART II.

    SciTech Connect

    Shanahan, K; Jeffrey Holder, J

    2006-08-17

    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 discussed 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.

  14. [Adsorption and Desorption Characteristics of Endosulfan in Purple Soil].

    PubMed

    Zhao, Yan; Zheng, Guo-can; Zhu, Heng; Zhang, Jin-zhong; Zhu, Xiu-ying; Hu, Shu-chun; Wu, Ya-lin

    2015-09-01

    In order to reveal the residual process of endosulfan in purple soil and protect soil ecological environment, the adsorption and desorption characteristics of endosulfan in purple soil were investigated, and effects of temperature, adsorbent amount, and initial pH of adsorption solution on the adsorption capacity were also examined by static adsorption and desorption experiments. The results showed that the adsorption kinetic process could be well described by the second-order kinetic equation with the initial rate constants of α-, β-endosulfan as 0. 157 and 0. 115 mg.(g.min)-1, respectively. The adsorption thermodynamic process could be well described by the Langmuir isotherm with the maximum adsorption capacities of α-, β-endosulfan as 0. 257 mg . g -1 and 0. 155 mg . g -1, respectively. The adsorption process of endosulfan in purple soil may be an exothermic physicochemical process, and is dominated by physical adsorption. Under the experimental conditions examined in this study, the initial pH of adsorption solution had a relative great influence on the adsorption capacity, whereas the temperature and adsorbent amount had no significant influence. The desorption experiments found that the maximum desorption capacities of α-, β-endosulfan adsorbed in purple soil were 0. 029 mg . g -1 and 0. 017 mg . g -1 at 6 and 4 h, and accounted for 10. 5% and 16. 1% in the maximum adsorption capacities, respectively. PMID:26717711

  15. [Adsorption and Desorption Characteristics of Endosulfan in Purple Soil].

    PubMed

    Zhao, Yan; Zheng, Guo-can; Zhu, Heng; Zhang, Jin-zhong; Zhu, Xiu-ying; Hu, Shu-chun; Wu, Ya-lin

    2015-09-01

    In order to reveal the residual process of endosulfan in purple soil and protect soil ecological environment, the adsorption and desorption characteristics of endosulfan in purple soil were investigated, and effects of temperature, adsorbent amount, and initial pH of adsorption solution on the adsorption capacity were also examined by static adsorption and desorption experiments. The results showed that the adsorption kinetic process could be well described by the second-order kinetic equation with the initial rate constants of α-, β-endosulfan as 0. 157 and 0. 115 mg.(g.min)-1, respectively. The adsorption thermodynamic process could be well described by the Langmuir isotherm with the maximum adsorption capacities of α-, β-endosulfan as 0. 257 mg . g -1 and 0. 155 mg . g -1, respectively. The adsorption process of endosulfan in purple soil may be an exothermic physicochemical process, and is dominated by physical adsorption. Under the experimental conditions examined in this study, the initial pH of adsorption solution had a relative great influence on the adsorption capacity, whereas the temperature and adsorbent amount had no significant influence. The desorption experiments found that the maximum desorption capacities of α-, β-endosulfan adsorbed in purple soil were 0. 029 mg . g -1 and 0. 017 mg . g -1 at 6 and 4 h, and accounted for 10. 5% and 16. 1% in the maximum adsorption capacities, respectively.

  16. A soil-column gas chromatography (SCGC) approach to explore the thermal desorption behavior of hydrocarbons from soils.

    PubMed

    Yu, Ying; Liu, Liang; Shao, Ziying; Ju, Tianyu; Sun, Bing; Benadda, Belkacem

    2016-01-01

    A soil-column gas chromatography approach was developed to simulate the mass transfer process of hydrocarbons between gas and soil during thermally enhanced soil vapor extraction (T-SVE). Four kinds of hydrocarbons-methylbenzene, n-hexane, n-decane, and n-tetradecane-were flowed by nitrogen gas. The retention factor k' and the tailing factor T f were calculated to reflect the desorption velocities of fast and slow desorption fractions, respectively. The results clearly indicated two different mechanisms on the thermal desorption behaviors of fast and slow desorption fractions. The desorption velocity of fast desorption fraction was an exponential function of the reciprocal of soil absolute temperature and inversely correlated with hydrocarbon's boiling point, whereas the desorption velocity of slow desorption fraction was an inverse proportional function of soil absolute temperature, and inversely proportional to the log K OW value of the hydrocarbons. The higher activation energy of adsorption was found on loamy soil with higher organic content. The increase of carrier gas flow rate led to a reduction in the apparent activation energy of adsorption of slow desorption fraction, and thus desorption efficiency was significantly enhanced. The obtained results are of practical interest for the design of high-efficiency T-SVE system and may be used to predict the remediation time.

  17. A soil-column gas chromatography (SCGC) approach to explore the thermal desorption behavior of hydrocarbons from soils.

    PubMed

    Yu, Ying; Liu, Liang; Shao, Ziying; Ju, Tianyu; Sun, Bing; Benadda, Belkacem

    2016-01-01

    A soil-column gas chromatography approach was developed to simulate the mass transfer process of hydrocarbons between gas and soil during thermally enhanced soil vapor extraction (T-SVE). Four kinds of hydrocarbons-methylbenzene, n-hexane, n-decane, and n-tetradecane-were flowed by nitrogen gas. The retention factor k' and the tailing factor T f were calculated to reflect the desorption velocities of fast and slow desorption fractions, respectively. The results clearly indicated two different mechanisms on the thermal desorption behaviors of fast and slow desorption fractions. The desorption velocity of fast desorption fraction was an exponential function of the reciprocal of soil absolute temperature and inversely correlated with hydrocarbon's boiling point, whereas the desorption velocity of slow desorption fraction was an inverse proportional function of soil absolute temperature, and inversely proportional to the log K OW value of the hydrocarbons. The higher activation energy of adsorption was found on loamy soil with higher organic content. The increase of carrier gas flow rate led to a reduction in the apparent activation energy of adsorption of slow desorption fraction, and thus desorption efficiency was significantly enhanced. The obtained results are of practical interest for the design of high-efficiency T-SVE system and may be used to predict the remediation time. PMID:26335523

  18. Superior hydrogen absorption and desorption behavior of Mg thin films

    NASA Astrophysics Data System (ADS)

    Qu, Jianglan; Wang, Yuntao; Xie, Lei; Zheng, Jie; Liu, Yang; Li, Xingguo

    Pd-capped Mg films prepared by magnetron sputtering achieved complete dehydrogenation in air at room temperature and behaved as favorable gasochromic switchable mirrors. Their cyclic hydrogen absorption and desorption kinetics in air were investigated by using the Bruggeman effective medium approximation. The overall activation energy was 80 kJ mol -1, while the reaction orders controlling desorption were deduced to be n = 2 at 328 K and n = 1 at lower temperatures by analyzing the transmittance data. The hydrogen diffusion coefficient and the corresponding activation energy were calculated by electrochemical measurements. Mg thin films exhibited the smaller activation energy and remarkable diffusion kinetics at room temperature which implied potential applications in smart windows.

  19. Thermal desorption of helium from homogeneously implanted graphite

    NASA Astrophysics Data System (ADS)

    Jung, P.; Schroeder, H.

    1991-11-01

    Super-fine grain graphite (FGG) and pyrolytic carbon (PYC) of thicknesses around 200 μm were homogeneously implanted at room temperature with α-particles (0.5 MeV ≤ Eα ≤ 22 MeV). Thermal helium desorption spectrometry in the temperature range from 400 to 1900 K can be described by diffusion kinetics with an activation energy of 1.1 eV in FGG and about 0.75 eV in PYC. Desorption during temperature ramping at a constant rate of 0.83 K/s also shows significant differences of the two graphite species. It is found that in FGG and especially in PYC a considerable fraction of the implanted helium is retained even beyond 1000 K. This is in contrast to results reported after low energy implantations to high doses for various graphite species.

  20. Programming Enhancements for Low Temperature Thermal Decomposition Workstation

    SciTech Connect

    Igou, R.E.

    1998-10-01

    This report describes a new control-and-measurement system design for the Oak Ridge Y-12 Plant's Low Temperature Thermal Decomposition (LTTD) process. The new design addresses problems with system reliability stemming from equipment obsolescence and addresses specific functional improvements that plant production personnel have identified, as required. The new design will also support new measurement techniques, which the Y-12 Development Division has identified for future operations. The new techniques will function in concert with the original technique so that process data consistency is maintained.

  1. [Thermal desorption behavior of PCDD/Fs on the fly ash].

    PubMed

    Zhang, Feng; Zhang, Hai-jun; Chen, Ji-ping; Liang, Xin-miao

    2008-02-01

    The article studied the thermal desorption behavior of PCDD/Fs on the fly ash under anoxic conditions. From the analysis of the PCDD/Fs concentrations in the gas phrase and solid residual, the several kinds of potential chemical reaction and physical changes of dioxin that occur at the different temperature are concluded. At the same time, desorption ratios of 17 toxic dioxin congers and the better desorption conditions are studied. At 200 degrees C and 300 degrees C, the average desorption ratio of PCDD/Fs are 96.2% and 95.5% respectively. At 400 degrees C, the average desorption ratio of PCDD/Fs is 99.7%. The experiment results show that the PCDD/Fs is dechlorinated at 300 degrees C. At 400 degrees C, a lot of precursor reactions happen in the fly ash, which enhance the content of PCDD/Fs.

  2. Synthesis of 4-vinylpyridine-divinylbenzene copolymer adsorbents for microwave-assisted desorption of benzene.

    PubMed

    Meng, Qing Bo; Yang, Go-Su; Lee, Youn-Sik

    2012-02-29

    Reports on the development of polymer adsorbents for microwave-assisted desorption of nonpolar volatile organic compounds (VOCs) are rare. In this study, we synthesized macroporous polymeric adsorbents with hydrophilic methyl pyridinium units for microwave-assisted desorption of nonpolar VOCs. The benzene adsorption and desorption properties of the adsorbents were investigated under both dry and humid conditions. Under humid conditions, as the content of the hydrophilic methyl pyridinium units in the adsorbents increased from 0 to 20%, the adsorption capacity of benzene decreased from about 21 to 7 mg/g, while the desorption efficiency of benzene increased significantly from 48 to 87%. The maximum concentration of desorbate also increased significantly as the content of the hydrophilic units was increased under humid conditions. We attributed the enhanced desorption efficiency mainly to more adsorbed moisture, which indirectly allowed heating of the polymer adsorbents to higher temperatures upon irradiation with 600 W microwaves. PMID:22236950

  3. 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,α and ln Aα, 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.

  4. Desorption behavior of zinc atoms from zinc-sulfate solution irradiated with pulsed DC plasma

    NASA Astrophysics Data System (ADS)

    Takaba, Takafumi; Suzuki, Haruka; Toyoda, Hirotaka

    2016-07-01

    A DC pulsed plasma ignited between a metal needle and zinc sulfate (ZnSO4) solution electrode was used to investigate Zn metal desorption from an electrolyte solution. Using an ICCD camera and optical band-pass filter, 2D atomic absorption spectroscopy was carried out during irradiation of pulsed plasma to the surface of the solution. The time-resolved measurement of Zn atoms released to the gas phase revealed that the Zn desorption rate monotonically increased with increasing number of discharge repetitions. The surface temperature of the electrolyte solution was observed with a thermographic camera, and correlations between the H2O and Zn desorption rate were inspected. The correlation between the H2O and Zn desorption rate suggested that Zn desorption is assisted not only by the electric field of the discharge but also by H2O evaporating from the solution.

  5. Isotope effects on desorption kinetics of hydrogen isotopes implanted into stainless steel by glow discharge

    SciTech Connect

    Matsuyama, M.; Kondo, M.; Noda, N.; Tanaka, M.; Nishimura, K.

    2015-03-15

    In a fusion device the control of fuel particles implies to know the desorption rate of hydrogen isotopes by the plasma-facing materials. In this paper desorption kinetics of hydrogen isotopes implanted into type 316L stainless steel by glow discharge have been studied by experiment and numerical calculation. The temperature of a maximum desorption rate depends on glow discharge time and heating rate. Desorption spectra observed under various experimental conditions have been successfully reproduced by numerical simulations that are based on a diffusion-limited process. It is suggested, therefore, that desorption rate of a hydrogen isotope implanted into the stainless steel is limited by a diffusion process of hydrogen isotope atoms in bulk. Furthermore, small isotope effects were observed for the diffusion process of hydrogen isotope atoms. (authors)

  6. Internal friction and gas desorption of {C}/{C} composites

    NASA Astrophysics Data System (ADS)

    Serizawa, H.; Sato, S.; Kohyama, A.

    1994-09-01

    {C}/{C} composites are the most promising candidates as high heat flux component materials, where temperature dependence of mechanical properties and gas desorption behavior at elevated temperature are important properties. At the beginning, the newly developed internal friction measurement apparatus, which enables the accurate measurement of dynamic elastic properties up to 1373 K along with the measurement of gas desorption behavior, was used. The materials studied were unidirectional (UD) {C}/{C} composites reinforced with mesophase pitch-based carbon fibers, which were heat treated at temperatures ranging from 1473 to 2773 K which produced a variety of graphitized microstructures. Two-dimensional (2D) {C}/{C} composites reinfored with flat woven fabrics of PAN type carbon fibers were also studied. These materials were heat treated at 1873 K. From the temperature spectrum of internal friction of 2D {C}/{C} composites, these internal friction peaks were detected and were related to gas desorption. Also the temperature dependence of Young's modulus of UD {C}/{C} composites, negative and positive dependence of Young's modulus were observed reflecting microstructure changes resulting from the heat treatments.

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

    SciTech Connect

    Pasto, Arvid

    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.

  8. Heavy metal desorption kinetic as affected by of anions complexation onto manganese dioxide surfaces.

    PubMed

    Zaman, Muhammad Iqbal; Mustafa, Syed; Khan, Sadullah; Xing, Baoshan

    2009-10-01

    Oxides of Fe, Al, and Mn have been studied extensively for heavy metals fixation in soil. However, little is known about the effect of anions on the desorption processes of these metals, especially from manganese dioxide. The purpose of this study was to examine the influence of residence time, temperature, and interacting anions on desorption of Pb(2+), Cd(2+) and Cu(2+) from MnO(2). MnO(2) was characterized by different experimental techniques prior to desorption studies. The sorption-desorption studies were conducted for Pb(2+), Cu(2+), and Cd(2+) ions in the presence of different electrolytes and at different temperature in the range 293-323 K. For all the sorption experiments, Pb(2+) sorption was the greatest and almost 100% sorption occurred in the presence of 0.001 M potassium phosphate. The sorption of metals under investigation followed the order Pb(2+)>Cu(2+)>Cd(2+), whereas the desorption order was Cd(2+)>Cu(2+)>Pb(2+) in 0.01 M potassium nitrate and sulphate. Only a small quantity of desorbed Pb was detected, even at the low value of pH 3. These results indicated the stability of lead phosphate precipitates or that phosphate treatment imparted stability to the ternary complexes formed at the MnO(2) surface. The detailed desorption kinetics were conducted only for Cd(2+) in 0.01 M potassium nitrate or 0.001 M phosphate at pH values of 3 and 4 in the temperature range 303-323 K. A substantial decrease in Cd(2+) desorption was noted with increasing pH and temperature and the desorption process reached equilibration in 3h at pH 4. However, at pH 3 the desorption fluctuated, which is probably due the dissolution of the solid at such low pH values.

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

    SciTech Connect

    Senevirathna, W. U.; Zhang, Hong; Gu, Baohua

    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.

  10. Effects of programming and healing temperatures on the healing efficiency of a confined healable polymer composite

    NASA Astrophysics Data System (ADS)

    Yougoubare, Y. Quentin; Pang, Su-Seng

    2014-02-01

    In previous work, a biomimetic close-then-heal (CTH) healing mechanism was proposed and validated to repeatedly heal wide-open cracks in load carrying engineering structures by using constrained expansion of compression programmed thermoset shape memory polymers (SMPs). In this study, the effects on healing efficiencies of variation of temperature during both thermomechanical programming and shape recovery (healing) under three-dimensional (3D) confinement are evaluated. The polymer considered is a polystyrene shape memory polymer with 6% by volume of thermoplastic particle additives (copolyester) dispersed in the matrix. In addition to the programming and healing temperatures, some of the parameters investigated include the flexural strength, crack width and elemental composition at the crack interface. It is observed that while increase of the programming temperature is slightly beneficial to strength recovery, most of the strength recovered and damage repair are strongly dependent on the healing temperature. The best healing efficiency (63%) is achieved by a combination of a programming temperature above the glass transition temperature of the polymer and a healing temperature above the bonding point of the copolyester.

  11. Computer program simplifies transient and steady-state temperature prediction for complex body shapes

    NASA Technical Reports Server (NTRS)

    Giebler, K. N.

    1966-01-01

    Computer program evaluates heat transfer modes and calculates either the transient or steady-state temperature distributions throughout an object of complex shape when heat sources are applied to specified points on the object. It uses an electrothermal model to simulate the conductance, heat capacity, and temperature potential of the object.

  12. Diurnal Soil Temperature Effects within the Globe[R] Program Dataset

    ERIC Educational Resources Information Center

    Witter, Jason D.; Spongberg, Alison L.; Czajkowski, Kevin P.

    2007-01-01

    Long-term collection of soil temperature with depth is important when studying climate change. The international program GLOBE[R] provides an excellent opportunity to collect such data, although currently endorsed temperature collection protocols need to be refined. To enhance data quality, protocol-based methodology and automated data logging,…

  13. Analysis of the volatile organic matter of engine piston deposits by direct sample introduction thermal desorption gas chromatography/mass spectrometry.

    PubMed

    Diaby, M; Kinani, S; Genty, C; Bouchonnet, S; Sablier, M; Le Negrate, A; El Fassi, M

    2009-12-01

    This article establishes an alternative method for the characterization of volatiles organic matter (VOM) contained in deposits of the piston first ring grooves of diesel engines using a ChromatoProbe direct sample introduction (DSI) device coupled to gas chromatography/mass spectrometry (GC/MS) analysis. The addition of an organic solvent during thermal desorption leads to an efficient extraction and a good chromatographic separation of extracted products. The method was optimized investigating the effects of several solvents, the volume added to the solid sample, and temperature programming of the ChromatoProbe DSI device. The best results for thermal desorption were found using toluene as an extraction solvent and heating the programmable temperature injector from room temperature to 300 degrees C with a temperature step of 105 degrees C. With the use of the optimized thermal desorption conditions, several components have been positively identified in the volatile fraction of the deposits: aromatics, antioxidants, and antioxidant degradation products. Moreover, this work highlighted the presence of diesel fuel in the VOM of the piston deposits and gave new facts on the absence of the role of diesel fuel in the deposit formation process. Most importantly, it opens the possibility of quickly performing the analysis of deposits with small amounts of samples while having a good separation of the volatiles. PMID:19894696

  14. High temperature thermocouple development program, part A and part B

    NASA Technical Reports Server (NTRS)

    Toenshoff, D. A.; Zysk, E. D.; Fleischner, P. L.

    1972-01-01

    The problem of extending the useful life of thermocouples intended for in-core and out-of-core thermionic applications in a vacuum environment at temperatures up to 2273 K for periods of time up to 10,000 hours was investigated. Many factors that may influence this useful life were examined, and a basic probe design was developed. With a few modifications, twenty-three thermocouple assemblies were fabricated. Generally the finished thermocouple consisted of solid doped W-3% Re and W-25% Re wires and high purity and high density BeO insulators, and was sheathed in a high purity tantalum tube. In a few probes, stranded thermocouple wires were substituted; commercial grade BeO was used; and in two cases, CVD W-22% Re tubing was used. Each of the components was made of the highest purity materials available; was subjected to special cleaning steps, and was assembled in a class 10,000 clean room. Pertinent physical and chemical properties were determined on each of the components. Special processing techniques were used in the fabrication of the high purity (99.95%), high density (over 95% of theoretical) BeO.

  15. 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.

  16. 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.

  17. Desorption kinetics of cesium from Fukushima soils.

    PubMed

    Murota, Kento; Saito, Takumi; Tanaka, Satoru

    2016-03-01

    Understanding the behaviors of Cs(+) in soils is crucial for evaluation of the impacts of disposal of soils contaminated by radiocesium, (137)Cs. The desorption rate of Cs(+) evaluated in relatively short periods of time may not be adequate for such a purpose. In this study, we investigated long-term desorption kinetics of (137)Cs and (133)Cs from soils collected in Fukushima Prefecture by batch desorption experiments in the presence of cation exchange resin as a sorbent. The sorbent can keep the concentration of Cs(+) in the aqueous phase low and prevent re-sorption of desorbed Cs(+). Up to 60% of (137)Cs was desorbed after 139 d in dilute KCl media, which was larger than the desorption by conventional short-term extraction with 1 M ammonium acetate. Desorption of (137)Cs continued even after this period. It was also found that high concentration of K(+) prevented desorption of Cs(+) in the initial stage of desorption, but the effect was alleviated with time. The desorbed fraction of stable Cs was smaller than that of (137)Cs. This indicated that (137)Cs may gradually move to more stable states in soils. The half-life of (137)Cs desorption from the slowest sorption site was estimated to be at least two years by a three-site desorption model. PMID:26773507

  18. Desorption of ciprofloxacin from clay mineral surfaces.

    PubMed

    Wu, Qingfeng; Li, Zhaohui; Hong, Hanlie; Li, Rongbiao; Jiang, Wei-Teh

    2013-01-01

    Desorption from soil clay components may affect the transport and fate of antibiotics in the environment. In this study, ciprofloxacin (CIP) desorption from a kaolinite and a montmorillonite was investigated under different pHs, different concentrations of metal cations of various valencies (Na(+), Ca(2+) and Al(3+)) and a cationic surfactant hexadecyltrimethylammonium (HDTMA), and different desorption cycles. Desorption of CIP from kaolinite and montmorillonite was strongly pH-dependent and desorption isotherms were well fitted with the Langmuir equation. The percentage of CIP desorbed increased with increasing initial CIP loadings, desorbing cation concentrations, and desorption cycles. Comparatively, CIP was more readily desorbed from kaolinite than from montmorillonite. Moreover, the hysteresis index values were all negative, suggesting that the presence of metal cations and HDTMA in solution promoted CIP desorption from clay minerals, owing to cation exchange. The XRD analyses indicated that desorption of CIP occurred from both external and interlayer surfaces of montmorillonite. Formation of Al-CIP complex on solid surface and then detachment of Al-CIP from the solid surface may contribute to the higher CIP desorption by Al(3+) in comparison to Na(+) and Ca(2+). PMID:23123088

  19. Synthesis and Hydrogen Desorption Properties of Aluminum Hydrides.

    PubMed

    Jeong, Wanseop; Lee, Sang-Hwa; Kim, Jaeyong

    2016-03-01

    Aluminum hydride (AlH3 or alane) is known to store maximum 10.1 wt.% of hydrogen at relatively low temperature (< 100 degrees C), which partially fulfills the U.S. department of energy requirements for gravimetric loading capacity. However, its detailed mechanisms of appearing of different phases, structural stability, and dynamics of hydrogen desorption are still not clear. To understand the desorption properties of hydrogen in alane, thermodynamically stable α-AlH3 was synthesized by employing an ethereal reaction method. The dependence of pathways on phase formation and the properties of hydrogen evolution were investigated, and the results were compared with the ones for γ-AlH3. It was found that γ-AlH3 requires 10 degrees C higher than that of γ-AlH3 to form, and its decomposition rate demonstrated enhanced endothermic stabilities. For desorption, all hydrogen atoms of alane evolved under an isothermal condition at 138 degrees C in less than 1 hour, and the sample completely transformed to pure aluminum. Our results show that the total amount of desorbed hydrogen from α-AlH3 exceeded 9.05 wt.%, with a possibility of further increase. Easy synthesis, thermal stability, and a large amount of hydrogen desorption of alane fulfill the requirements for light-weight hydrogen storage materials once the pathway of hydrogen cycling is provided. PMID:27455747

  20. Synthesis and Hydrogen Desorption Properties of Aluminum Hydrides.

    PubMed

    Jeong, Wanseop; Lee, Sang-Hwa; Kim, Jaeyong

    2016-03-01

    Aluminum hydride (AlH3 or alane) is known to store maximum 10.1 wt.% of hydrogen at relatively low temperature (< 100 degrees C), which partially fulfills the U.S. department of energy requirements for gravimetric loading capacity. However, its detailed mechanisms of appearing of different phases, structural stability, and dynamics of hydrogen desorption are still not clear. To understand the desorption properties of hydrogen in alane, thermodynamically stable α-AlH3 was synthesized by employing an ethereal reaction method. The dependence of pathways on phase formation and the properties of hydrogen evolution were investigated, and the results were compared with the ones for γ-AlH3. It was found that γ-AlH3 requires 10 degrees C higher than that of γ-AlH3 to form, and its decomposition rate demonstrated enhanced endothermic stabilities. For desorption, all hydrogen atoms of alane evolved under an isothermal condition at 138 degrees C in less than 1 hour, and the sample completely transformed to pure aluminum. Our results show that the total amount of desorbed hydrogen from α-AlH3 exceeded 9.05 wt.%, with a possibility of further increase. Easy synthesis, thermal stability, and a large amount of hydrogen desorption of alane fulfill the requirements for light-weight hydrogen storage materials once the pathway of hydrogen cycling is provided.

  1. Ocean thermal energy conversion gas desorption studies. Volume 1. Design of experiments. [Open-cycle power systems

    SciTech Connect

    Golshani, A.; Chen, F.C.

    1980-10-01

    Seawater deaeration is a process affecting almost all proposed Ocean Thermal Energy Conversion (OTEC) open-cycle power systems. If the noncondensable dissolved air is not removed from a power system, it will accumulate in thecondenser, reduce the effectiveness of condensation, and result in deterioration of system performance. A gas desorption study is being conducted at Oak Ridge National Laboratory (ORNL) with the goal of mitigating these effects; this study is designed to investigate the vacuum deaeration process for low-temperature OTEC conditions where conventional steam stripping deaeration may not be applicable. The first in a series describing the ORNL studies, this report (1) considers the design of experiments and discusses theories of gas desorption, (2) reviews previous relevant studies, (3) describes the design of a gas desorption test loop, and (4) presents the test plan for achieving program objectives. Results of the first series of verification tests and the uncertainties encountered are also discussed. A packed column was employed in these verification tests and test data generally behaved as in previous similar studies. Results expressed as the height of transfer unit (HTU) can be correlated with the liquid flow rate by HTU = 4.93L/sup 0/ /sup 25/. End effects were appreciable for the vacuum deaeration system, and a correlation of them to applied vacuum pressure was derived.

  2. Air separation with temperature and pressure swing

    DOEpatents

    Cassano, Anthony A.

    1986-01-01

    A chemical absorbent air separation process is set forth which uses a temperature swing absorption-desorption cycle in combination with a pressure swing wherein the pressure is elevated in the desorption stage of the process.

  3. THERMTRAJ: A FORTRAN program to compute the trajectory and gas film temperatures of zero pressure balloons

    NASA Technical Reports Server (NTRS)

    Horn, W. J.; Carlson, L. A.

    1983-01-01

    A FORTRAN computer program called THERMTRAJ is presented which can be used to compute the trajectory of high altitude scientific zero pressure balloons from launch through all subsequent phases of the balloon flight. In addition, balloon gas and film temperatures can be computed at every point of the flight. The program has the ability to account for ballasting, changes in cloud cover, variable atmospheric temperature profiles, and both unconditional valving and scheduled valving of the balloon gas. The program was verified for an extensive range of balloon sizes (from 0.5 to 41.47 million cubic feet). Instructions on program usage, listing of the program source deck, input data and printed and plotted output for a verification case are included.

  4. Thermal desorption of oxygen from near-stoichiometric cationic vanadium oxide clusters

    NASA Astrophysics Data System (ADS)

    Kurokawa, Hodaka; Mafuné, Fumitaka

    2016-05-01

    Oxygen desorption from cationic vanadium oxide clusters, VnOm+ (n = 2-10), composed of a near-stoichiometric (n:m = 2:5) frame with excess oxygen attached was investigated in a thermal energy region by time-of-flight mass spectrometry and thermal desorption spectrometry. Oxygen molecules were observed to desorb from the clusters during heating. The activation energy for desorption was estimated from the temperature dependence of different clusters and exhibited an even-odd alternation with respect to the cluster size, n. This alternation can be explained in terms of oxidation states of the vanadium atoms.

  5. Flight summaries and temperature climatology at airliner cruise altitudes from GASP (Global Atmospheric Sampling Program) data

    NASA Technical Reports Server (NTRS)

    Nastrom, G. D.; Jasperson, W. H.

    1983-01-01

    Temperature data obtained by the Global Atmospheric Sampling Program (GASP) during the period March 1975 to July 1979 are compiled to form flight summaries of static air temperature and a geographic temperature climatology. The flight summaries include the height and location of the coldest observed temperature and the mean flight level, temperature and the standard deviation of temperature for each flight as well as for flight segments. These summaries are ordered by route and month. The temperature climatology was computed for all statistically independent temperture data for each flight. The grid used consists of 5 deg latitude, 30 deg longitude and 2000 feet vertical resolution from FL270 to FL430 for each month of the year. The number of statistically independent observations, their mean, standard deviation and the empirical 98, 50, 16, 2 and .3 probability percentiles are presented.

  6. Adsorption, Desorption, and Clustering H20 on Pt (111)

    SciTech Connect

    Daschbach, John L.; Peden, Brandon M.; Smith, R. Scott; Kay, Bruce D.

    2004-01-15

    The adsorption, desorption, and clustering behavior of H20 on Pt(111) has been investigated by specular He scattering. The data show that water adsorbed on a clean Pt(111) surface undergoes a transition from a random to a clustered structure near 60 K. The initial helium scattering cross sections as a function of temperature are found to be insensitive to H20 flux over a range of 0.005 ML/s to 0.55 ML/s indicating the clustering process is more complex than simple surface diffusion. The coarsening process of an initially random distribution of water deposited at 25 K is found to occur over a broad temperature range, 60 K< T <140 K, during thermal annealing. The desorption kinetics for submonolayer water are determined to be zero-order for surface coverages greater than 0.05 ML and temperatures between 150 K and 174 K. The zero-order desorption kinetics are consistent with a two-dimensional two-phase coexistence between H2O condensed phase and a 2-gas phase on the Pt surface

  7. 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

    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.

  8. Desorption induced by electronic transitions

    NASA Astrophysics Data System (ADS)

    Ageev, V. N.

    1994-10-01

    A survey is presented of the techniques and instruments used in studies of desorption induced by electronic transitions (DIET) that can be stimulated by irradiating a solid surface by electrons (ESD) or photons (PSD). The most general characteristics and aspects of this phenomenon are systematized. An analysis is made of relations between DIET and crystallographic and band structure of the substrate, the nature of adsorption bonding and specific features of desorbing particles. The main DIET models involving various electronic excitations of adsorption bonding and their relaxation as particles escape from the surface are discussed, and their predictions are compared with the available experimental data. Particular attention is focussed on the DIET models involving many-electron excitations. The various applications of DIET techniques to studies of adsorbed layers and of surface processes are considered. The radiation stability of solid surfaces and of film coatings with respect to excitation of their electronic subsystem is discussed.

  9. 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

  10. Behaviour of neutron irradiated beryllium during temperature excursions up to and beyond its melting temperature

    NASA Astrophysics Data System (ADS)

    Pajuste, Elina; Kizane, Gunta; Avotiņa, Līga; Zariņš, Artūrs

    2015-10-01

    Beryllium pebble behaviour has been studied regarding the accidental operation conditions of tritium breeding blanket of fusion reactors. Structure evolution, oxidation and thermal properties have been compared for nonirradiated and neutron irradiated beryllium pebbles during thermal treatment in a temperature range from ambient temperature to 1600 K. For neutron irradiated pebbles tritium release process was studied. Methods of temperature programmed tritium desorption (TPD) in combination with thermogravimetry (TG) and temperature differential analysis (TDA), scanning electron microscopy (SEM) in combination with Energy Dispersive X-ray analysis (EDX) have been used. It was found that there are strong relation between tritium desorption spectra and structural evolution of neutron irradiated beryllium. The oxidation rate is also accelerated by the structure damages caused by neutrons.

  11. Gas Desorption and Electron Emission from 1 MeV Potassium Ion Bombardment of Stainless Steel

    SciTech Connect

    Molvik, A W; Covo, M K; Bieniosek, F M; Prost, L; Seidl, P A; Baca, D; Coorey, A; Sakumi, A

    2004-07-19

    Gas desorption and electron emission coefficients were measured for 1 MeV potassium ions incident on stainless steel at grazing angles (between 80 and 88 from normal incidence) using a new gas-electron source diagnostic (GESD). Issues addressed in design and commissioning of the GESD include effects from backscattering of ions at the surface, space-charge limited emission current, and reproducibility of desorption measurements. We find that electron emission coefficients {gamma}{sub e} scale as 1/cos({theta}) up to angles of 86, where {gamma}{sub e} = 90. Nearer grazing incidence, {gamma}{sub e} is reduced below the 1/cos({theta}) scaling by nuclear scattering of ions through large angles, reaching {gamma}{sub e} = 135 at 88. Electrons were emitted with a measured temperature of {approx}30 eV. Gas desorption coefficients {gamma}{sub sigma} were much larger, of order {gamma}{sub sigma} = 104. They also varied with angle, but much more slowly than 1/cos({theta}). From this we conclude that the desorption was not entirely from adsorbed layers of gas on the surface. Two mitigation techniques were investigated: rough surfaces reduced electron emission by a factor of ten and gas desorption by a factor of two; a mild bake to 230 had no effect on electron emission, but decreased gas desorption by 15% near grazing incidence. We propose that gas desorption is due to electronic sputtering.

  12. Gas Desorption and Electron Emission from 1 MeV Potassium Iion Bombardment of Stainless Steel

    SciTech Connect

    Molvik, A; Covo, M K; Bieniosek, F; Prost, L; Seidl, P; Baca, D; Coorey, A; Sakumi, A

    2004-03-25

    Gas desorption and electron emission coefficients were measured for 1 MeV potassium ions incident on stainless steel at grazing angles (between 80 and 88 degrees from normal incidence) using a new gas-electron source diagnostic (GESD). Issues addressed in design and commissioning of the GESD include effects from backscattering of ions at the surface, space-charge limited emission current, and reproducibility of desorption measurements. We find that electron emission coefficients {gamma}{sub e} scale as 1/cos({theta}) up to angles of 86 degrees, where {gamma}{sub e} = 90. Nearer grazing incidence, {gamma}{sub e} is reduced below the 1/cos({theta}) scaling by nuclear scattering of ions through large angles, reaching {gamma}{sub e} = 135 at 88 degrees. Electrons were emitted with a measured temperature of {approx}30 eV. Gas desorption coefficients {gamma}{sub 0} were much larger, of order {gamma}{sub 0} = 10{sub 4}. They also varied with angle, but much more slowly than 1/cos({theta}). From this we conclude that the desorption was not entirely from adsorbed layers of gas on the surface. Two mitigation techniques were investigated: rough surfaces reduced electron emission by a factor of ten and gas desorption by a factor of two; a mild bake to {approx}220 degrees had no effect on electron emission, but decreased gas desorption by 15% near grazing incidence. We propose that gas desorption is due to electronic sputtering.

  13. Adsorption and desorption characteristics of arsenic onto ceria nanoparticles

    PubMed Central

    2012-01-01

    The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (ΔH0, ΔS0, and ΔG0) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment. PMID:22269298

  14. Determination of surface coverage of catalysts: Temperature programmed experiments on platinum and iridium sponge catalysts after low temperature ammonia oxidation

    SciTech Connect

    Broek, A.C.M. van den; Grondelle, J. van; Santen, R.A. van

    1999-07-25

    The activity of iridium and platinum sponge catalysts was studied in the low temperature gas phase oxidation of ammonia with oxygen. Under the reaction conditions used, iridium was found to be more active and more selective to nitrogen than platinum. Furthermore it was established from activity measurements that both catalysts lose activity as a function of time on stream due to inhibition of the surface by reaction intermediates. The used catalysts were studied by XPS and temperature programmed techniques. It was found that the surface of the catalysts had a high coverage of NH and OH and some additional NH{sub 2}. It seems most likely that the reaction mechanism proceeds through a stepwise dehydrogenation of the ammonia molecule. It appears that the last dehydrogenation step (NH by OH to N and water) is the rate determining step. The high selectivity of iridium to nitrogen can be explained by the higher activity of iridium in dissociating NO.

  15. 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

  16. The desorption of toluene from a montmorillonite clay adsorbent in a rotary kiln environment

    SciTech Connect

    Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Xiao Xue Deng; Pershing, D.W. ); Cundy, V.A.; Leger, C.B.; Jakway, A.L. )

    1992-05-01

    The vaporization of toluene from pre-dried, 3 mm montmorillonite clay particles was studied in a 130 kW pilot-scale rotary kiln with inside dimensions of 0.61 by 0.61 meters. Vaporization rates were obtained with a toluene weight fraction of 0.25 percent as a function of kiln fill fractions from 3 to 8 percent, rotation rates from 0.1 to 0.9 rpm, and kiln wall temperatures from 189 to 793 C. Toluene desorption rates were obtained from gas-phase measurements and interpreted using a desorption model that incorporates the slumping frequency of the solids, the fill fraction of the kiln, the diffusion of toluene in the bed, and the rate of particle desorption using an Arrhenius-type expression that is a function of bed temperature and average bed concentration. The model included three adjustable desorption parameters which were obtained by fitting the experimental data at one set of conditions with a least squares technique. Solid and kiln-wall temperatures were continuously recorded and used in the model at predicting the effects of fill fraction and rotation rate over a range of temperatures. A methodology for predicting full-scale performance was developed. Full-scale toluene desorption predictions were completed for different operating temperatures.

  17. Computer program determines thermal environment and temperature history of lunar orbiting space vehicles

    NASA Technical Reports Server (NTRS)

    Head, D. E.; Mitchell, K. L.

    1967-01-01

    Program computes the thermal environment of a spacecraft in a lunar orbit. The quantities determined include the incident flux /solar and lunar emitted radiation/, total radiation absorbed by a surface, and the resulting surface temperature as a function of time and orbital position.

  18. 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)

  19. An Application of Trimethylsilyl Derivatives with Temperature Programmed Gas Chromatography to the Senior Analytical Laboratory.

    ERIC Educational Resources Information Center

    Kelter, Paul B.; Carr, James D.

    1983-01-01

    Describes an experiment designed to teach temperature programed gas chromatography (TPGC) techniques and importance of derivatizing many classes of substrated to be separated. Includes equipment needed, procedures for making trimethylsilyl derivatives, applications, sample calculations, and typical results. Procedure required one, three-hour…

  20. Advanced High Temperature Polymer Matrix Composites for Gas Turbine Engines Program Expansion

    NASA Technical Reports Server (NTRS)

    Hanley, David; Carella, John

    1999-01-01

    This document, submitted by AlliedSignal Engines (AE), a division of AlliedSignal Aerospace Company, presents the program final report for the Advanced High Temperature Polymer Matrix Composites for Gas Turbine Engines Program Expansion in compliance with data requirements in the statement of work, Contract No. NAS3-97003. This document includes: 1 -Technical Summary: a) Component Design, b) Manufacturing Process Selection, c) Vendor Selection, and d) Testing Validation: 2-Program Conclusion and Perspective. Also, see the Appendix at the back of this report. This report covers the program accomplishments from December 1, 1996, to August 24, 1998. The Advanced High Temperature PMC's for Gas Turbine Engines Program Expansion was a one year long, five task technical effort aimed at designing, fabricating and testing a turbine engine component using NASA's high temperature resin system AMB-21. The fiber material chosen was graphite T650-35, 3K, 8HS with UC-309 sizing. The first four tasks included component design and manufacturing, process selection, vendor selection, component fabrication and validation testing. The final task involved monthly financial and technical reports.

  1. Collision-induced desorption of CO from Ru(0001) by hyperthermal argon and nitrogen

    NASA Astrophysics Data System (ADS)

    Huang, Qiang; Lou, Yuanfu; Kleyn, Aart W.; Zaharia, Teodor; Gleeson, Michael A.

    2016-08-01

    Collision-induced desorption of CO from Ru(0001) by hyperthermal (5-9 eV) effusive beams of Ar and N + N2 has been studied at a sample temperature of 400 K. Prompt desorption occurs with cross sections on the order of 4 Å2. Based on post-exposure thermal desorption measurements, ~ 1/3 of the initial CO coverage cannot be desorbed by Ar on the time scale of the current experiments. In contrast, exposure to the mixed N + N2 beam appears to remove all CO from the irradiated region. This is attributed to a lowering of the CO binding energy by adsorbed N-atoms. While there is no evidence of a large influence of surface diffusion on the time scale of these exposure, desorption simulations suggest that local diffusion in the periphery of the exposed region influences the measured decay.

  2. Carbon dioxide removal from flue gases by absorption/ desorption in aqueous diethanolamine solutions.

    PubMed

    Kierzkowska-Pawlak, Hanna; Chacuk, Andrzej

    2010-08-01

    The carbon dioxide (CO2) desorption rate from CO2- loaded aqueous diethanolamine (DEA) solutions was measured using a stirred cell with a flat gas-liquid interface. The measurements were performed in the temperature range of 293.15-313.15 K and an amine concentration range of 10-20% mass DEA. Measurements were based on a semibatch isothermal absorption of the gas until the equilibrium state was reached, followed by desorption, which was initiated by the pressure release in the system. A simplified mass transfer model based on the film theory coupled with CO2, mass balance was developed to interpret the experimental data. On the basis of the proposed model, the initial mass transfer rates were calculated from the experimental results. The calculated initial desorption rates enabled estimation of the enhancement factor for CO2 mass transfer from aqueous DEA solutions. Analysis of the experimental data showed that desorption took place in the diffusive mass transfer regime.

  3. THE HIGH-TEMPERATURE ELECTROLYSIS PROGRAM AT THE IDAHO NATIONAL LABORATORY: OBSERVATIONS ON PERFORMANCE DEGRADATION

    SciTech Connect

    J. E. O'Brien; C. M. Stoots; J. S. Herring; K. G. Condie; G. K. Housley

    2009-06-01

    This paper presents an overview of the high-temperature electrolysis research and development program at the Idaho National Laboratory, with selected observations of electrolysis cell degradation at the single-cell, small stack and large facility scales. The objective of the INL program is to address the technical and scale-up issues associated with the implementation of solid-oxide electrolysis cell technology for hydrogen production from steam. In the envisioned application, high-temperature electrolysis would be coupled to an advanced nuclear reactor for efficient large-scale non-fossil non-greenhouse-gas hydrogen production. The program supports a broad range of activities including small bench-scale experiments, larger scale technology demonstrations, detailed computational fluid dynamic modeling, and system modeling. A summary of the current status of these activities and future plans will be provided, with a focus on the problem of cell and stack degradation.

  4. Computer Program for Calculation of a Gas Temperature Profile by Infrared Emission: Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Buchele, D. R.

    1977-01-01

    A computer program to calculate the temperature profile of a flame or hot gas was presented in detail. Emphasis was on profiles found in jet engine or rocket engine exhaust streams containing H2O or CO2 radiating gases. The temperature profile was assumed axisymmetric with an assumed functional form controlled by two variable parameters. The parameters were calculated using measurements of gas radiation at two wavelengths in the infrared. The program also gave some information on the pressure profile. A method of selection of wavelengths was given that is likely to lead to an accurate determination of the parameters. The program is written in FORTRAN IV language and runs in less than 60 seconds on a Univac 1100 computer.

  5. VAC*TRAX - Thermal desorption for mixed wastes

    SciTech Connect

    McElwee, M.J.; Palmer, C.R.

    1995-12-01

    The patented VAC*TRAX process was designed in response to the need to remove organic constituents from mixed waste, waste that contains both a hazardous (RCRA or TSCA regulated) component and a radioactive component. Separation of the mixed waste into its hazardous and radioactive components allows for ultimate disposal of the material at existing, permitted facilities. The VAC*TRAX technology consists of a jacketed vacuum dryer followed by a condensing train. Solids are placed in the dryer and indirectly heated to temperatures as high as 260{degrees}C, while a strong vacuum (down to 50 mm Hg absolute pressure) is applied to the system and the dryer is purged with a nitrogen carrier gas. The organic contaminants in the solids are thermally desorbed, swept up in the carrier gas and into the condensing train where they are cooled and recovered. The dryer is fitted with a filtration system that keeps the radioactive constituents from migrating to the condensate. As such, the waste is separated into hazardous liquid and radioactive solid components, allowing for disposal of these streams at a permitted incinerator or a radioactive materials landfill, respectively. The VAC*TRAX system is designed to be highly mobile, while minimizing the operational costs with a simple, robust process. These factors allow for treatment of small waste streams at a reasonable cost. This paper describes the VAC*TRAX thermal desorption process, as well as results from the pilot testing program. Also, the design and application of the full-scale treatment system is presented. Materials tested to date include spiked soil and debris, power plant trash and sludge contaminated with solvents, PCB contaminated soil, solvent-contaminated uranium mill-tailings, and solvent and PCB-contaminated sludge and trash. Over 70 test runs have been performed using the pilot VAC*TRAX system, with more than 80% of the tests using mixed waste as the feed material.

  6. Thermal Desorption Analysis of Hydrogen in High Strength Martensitic Steels

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Hirakami, D.; Tarui, T.

    2012-02-01

    Thermal desorption analyses (TDA) were conducted in high strength martensitic steels containing carbon from 0.33 to 1.0 mass pct, which were charged with hydrogen at 1223 K (950 °C) under hydrogen of one atmospheric pressure and quenched to room temperature. In 0.33C steel, which had the highest M s temperature, only one desorption peak was observed around 373 K (100 °C), whereas two peaks, one at a similar temperature and the other around and above 573 K (300 °C), were observed in the other steels, the height of the second peak increasing with carbon content. In 0.82C steel, both peaks disappeared during exposure at room temperature in 1 week, whereas the peak heights decreased gradually over 2 weeks in specimens electrolytically charged with hydrogen and aged for varying times at room temperature. From computer simulation, by means of the McNabb-Foster theory coupled with theories of carbon segregation, these peaks are likely to be due to trapping of hydrogen in the strain fields and cores of dislocations, and presumably to a lesser extent in prior austenite grain boundaries. The results also indicate that carbon atoms prevent and even expel hydrogen from trapping sites during quenching and aging in these steels.

  7. Thermal desorption of PCB-contaminated soil with sodium hydroxide.

    PubMed

    Liu, Jie; Qi, Zhifu; Zhao, Zhonghua; Li, Xiaodong; Buekens, Alfons; Yan, Jianhua; Ni, Mingjiang

    2015-12-01

    The thermal desorption was combined with sodium hydroxide to remediate polychlorinated biphenyl (PCB)-contaminated soil. The experiments were conducted at different temperatures ranging from 300 to 600 °C with three NaOH contents of 0.1, 0.5, and 1 %. The results showed that thermal desorption was effective for PCB removal, destruction, and detoxication, and the presence of NaOH enhanced the process by significant dechlorination. After treatment with 0.1 % NaOH, the removal efficiency (RE) increased from 84.8 % at 300 °C to 98.0 % at 600 °C, corresponding to 72.7 and 91.7 % of destruction efficiency (DE). With 1 % NaOH content treated at 600 °C, the RE and DE were 99.0 and 93.6 %, respectively. The effect of NaOH content on PCB removal was significant, especially at lower temperature, yet it weakened under higher temperature. The interaction between NaOH content and temperature influenced the PCB composition. The higher temperature with the help of NaOH effectively increased the RE and DE of 12 dioxin-like PCBs (based on WHO-TEQ).

  8. 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.

  9. Analytical solution and computer program (FAST) to estimate fluid fluxes from subsurface temperature profiles

    NASA Astrophysics Data System (ADS)

    Kurylyk, Barret L.; Irvine, Dylan J.

    2016-02-01

    This study details the derivation and application of a new analytical solution to the one-dimensional, transient conduction-advection equation that is applied to trace vertical subsurface fluid fluxes. The solution employs a flexible initial condition that allows for nonlinear temperature-depth profiles, providing a key improvement over most previous solutions. The boundary condition is composed of any number of superimposed step changes in surface temperature, and thus it accommodates intermittent warming and cooling periods due to long-term changes in climate or land cover. The solution is verified using an established numerical model of coupled groundwater flow and heat transport. A new computer program FAST (Flexible Analytical Solution using Temperature) is also presented to facilitate the inversion of this analytical solution to estimate vertical groundwater flow. The program requires surface temperature history (which can be estimated from historic climate data), subsurface thermal properties, a present-day temperature-depth profile, and reasonable initial conditions. FAST is written in the Python computing language and can be run using a free graphical user interface. Herein, we demonstrate the utility of the analytical solution and FAST using measured subsurface temperature and climate data from the Sendia Plain, Japan. Results from these illustrative examples highlight the influence of the chosen initial and boundary conditions on estimated vertical flow rates.

  10. Plasma Desorption Mass Spectrometry: Coming of Age.

    ERIC Educational Resources Information Center

    Cotter, Robert J.

    1988-01-01

    Discusses the history and development of Plasma Desorption Mass Spectrometry to determine molecular weights and structures of proteins and polymers. Outlines theory, instrumentation, and sample preparation commonly used. Gives several examples of resulting spectra. (ML)

  11. Desorption of oxygen from alloyed Ag/Pt(111)

    SciTech Connect

    Jankowski, Maciej; Wormeester, Herbert Zandvliet, Harold J. W.; Poelsema, Bene

    2014-06-21

    We have investigated the interaction of oxygen with the Ag/Pt(111) surface alloy by thermal desorption spectroscopy (TDS). The surface alloy was formed during the deposition of sub-monolayer amounts of silver on Pt(111) at 800 K and subsequent cooling to 300 K. The low-temperature phase of the surface alloy is composed of nanometer-sized silver rich stripes, embedded within platinum-rich domains, which were characterized with spot profile analysis low energy electron diffraction. The TDS measurements show that oxygen adsorption is blocked on Ag sites: the saturation coverage of oxygen decreases with increasing Ag coverage. Also, the activation energy for desorption (E{sub des}) decreases with Ag coverage. The analysis of the desorption spectra from clean Pt(111) shows a linear decay of E{sub des} with oxygen coverage, which indicates repulsive interactions between the adsorbed oxygen atoms. In contrast, adsorption on alloyed Ag/Pt(111) leads to an attractive interaction between adsorbed oxygen atoms.

  12. Supercritical CO2 desorption of activated carbon loaded with 2,2,3,3-tetrafluoro-1-propanol in a rotating packed bed.

    PubMed

    Tan, Chung-Sung; Lee, Pei-Lun

    2008-03-15

    Desorption of activated carbon loaded with 2,2,3,3-tetrafluoro-1-propanol (TFP) by supercritical carbon dioxide in a rotating packed bed was investigated in this study. The experimental data show that the time required to achieve complete desorption of TFP from activated carbon in a rotating packed bed was much lower than that in a static packed bed. The reduction of desorption time is attributed to the presence of centrifugal force. The supercritical CO2 desorption efficiency in a rotating packed bed was observed to increase with increasing rotation speed, pressure, and C02 flow rate. To enhance desorption efficiency, a smaller activated carbon particle size was suggested. At low operating pressures such as 8.96 and 11.72 MPa, a better desorption efficiency was found to occur at lower temperatures in a temperature range of 305-335 K. However, at high operating pressures such as 15.86 MPa, a temperature of 315 K was found to be more appropriate for desorption, as compared to other temperatures. Due to a reduction of packed bed volume and an increase in desorption efficiency, supercritical CO2 desorption in a rotating packed bed is suggested for recovering TFP from the exhaust gases. PMID:18409651

  13. Further development of the dynamic gas temperature measurement system. Volume 2: Computer program user's manual

    NASA Technical Reports Server (NTRS)

    Stocks, Dana R.

    1986-01-01

    The Dynamic Gas Temperature Measurement System compensation software accepts digitized data from two different diameter thermocouples and computes a compensated frequency response spectrum for one of the thermocouples. Detailed discussions of the physical system, analytical model, and computer software are presented in this volume and in Volume 1 of this report under Task 3. Computer program software restrictions and test cases are also presented. Compensated and uncompensated data may be presented in either the time or frequency domain. Time domain data are presented as instantaneous temperature vs time. Frequency domain data may be presented in several forms such as power spectral density vs frequency.

  14. Prenatal acoustic communication programs offspring for high posthatching temperatures in a songbird.

    PubMed

    Mariette, Mylene M; Buchanan, Katherine L

    2016-08-19

    In many species, embryos can perceive and learn external sounds. Yet, the possibility that parents may use these embryonic capacities to alter their offspring's developmental trajectories has not been considered. Here, we demonstrate that zebra finch parents acoustically signal high ambient temperatures (above 26°C) to their embryos. We show that exposure of embryos to these acoustic cues alone adaptively alters subsequent nestling begging and growth in response to nest temperature and influences individuals' reproductive success and thermal preferences as adults. These findings have implications for our understanding of maternal effects, phenotypic plasticity, developmental programming, and the adaptation of endothermic species to a warming world. PMID:27540172

  15. Dynamic gas temperature measurement system. Volume 2: Operation and program manual

    NASA Technical Reports Server (NTRS)

    Purpura, P. T.

    1983-01-01

    The hot section technology (HOST) dynamic gas temperature measurement system computer program acquires data from two type B thermocouples of different diameters. The analysis method determines the in situ value of an aerodynamic parameter T, containing the heat transfer coefficient from the transfer function of the two thermocouples. This aerodynamic parameter is used to compute a fequency response spectrum and compensate the dynamic portion of the signal of the smaller thermocouple. The calculations for the aerodynamic parameter and the data compensation technique are discussed. Compensated data are presented in either the time or frequency domain, time domain data as dynamic temperature vs time, or frequency domain data.

  16. Final report of comprehensive testing program for concrete at elevated temperatures

    SciTech Connect

    Oland, C.B.; Naus, D.J.; Robinson, G.C.

    1980-10-01

    The objective of this program was to define the variations in physical (thermal) and mechanical (strength) properties of limestone aggregate concrete and lightweight insulating concrete exposed to elevated temperatures that could occur as a result of a postulated large sodium spill in a lined LMFBR equipment cell. To meet this objective, five test series were conducted: (1) unconfined compression, (2) shear, (3) rebar bond, (4) sustained loading (creep), and (5) thermal properties. Mechanical property results are presented for concretes subjected to temperature up to 621{sup 0}C (1150{sup 0}F).

  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. 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.

  19. Film growth, adsorption and desorption kinetics of indigo on SiO{sub 2}

    SciTech Connect

    Scherwitzl, Boris Resel, Roland; Winkler, Adolf

    2014-05-14

    Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer desorption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption.

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

    SciTech Connect

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

    1980-11-30

    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 a novel programmed temperature, elevated pressure, hot stage video microscope for observation of coal particle changes during heating. This system was used to develop a minimum-time heating schedule capable of carbonizing the coal at elevated pressures in the presence of hydrogen without severe agglomeration. Isothermal fixed heating rate data for a series of coals were subsequently used to calibrate and verify the mathematical model for the PTG process. These results showed good correlation between experimental data and mathematical predictions. Commercial application of the PTG concept to batch, moving bed and fluid bed processing schemes was then evaluated. Based on the calibrated model programmed temperature gasification of the coal without severe agglomeration could be carried out on a commercial batch reaction in 4 to 12 minutes. The next step in development of the PTG concept for commercial application would require testing on a bench scale (3-inch diameter) gasifier coupled with a full commercial assessment to determine size and cost of various gasification units.

  1. 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 μGC 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 100μm×100μm has been developed using silicon microfabrication techniques. The microfabricated column was benchmarked against a 2m 100μm 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 μGC column in temperature programmed mode. The demonstrated μGC column along with the high temperature fixture offers one more solution toward potentially realizing a portable μGC device for the detection of semi-volatile environmental pollutants and explosives without the thermal limitations reported to date with μGC columns using epoxy based interconnect technology. PMID:24866564

  2. 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 μGC 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 100μm×100μm has been developed using silicon microfabrication techniques. The microfabricated column was benchmarked against a 2m 100μm 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 μGC column in temperature programmed mode. The demonstrated μGC column along with the high temperature fixture offers one more solution toward potentially realizing a portable μGC device for the detection of semi-volatile environmental pollutants and explosives without the thermal limitations reported to date with μGC columns using epoxy based interconnect technology.

  3. Program accomplishments and future prospects for low-temperature geothermal resource assessment in New Mexico

    SciTech Connect

    Icerman, L.; Ruscetta, C.A.

    1982-07-01

    An important component of the State-coupled program has been basic studies in specific regions of New Mexico, including areas adjacent to the cities of Albuquerque, Las Cruces, Socorro, and Truth or Consequences. Considerable geological, hydrological, electrical resistivity, gravity, magnetic, seismic, water analysis, and subsurface temperature data have been compiled and analyzed for these locations. During the four-year research program, a total of 25 tasks have been undertaken. Eleven of these tasks were focused toward collecting and compiling statewide data, six were regional studies covering more than one county, and eight were research projects directed primarily toward data collection near specific cities or known resource areas. Two of these latter studies contributed significantly to the confirmation of the Las Alturas geothermal anomaly east of Las Cruces. A brief summary of the program accomplishments by task is presented. The resource assessment programs in New Mexico have been very successful in (1) delineating low-temperature geothermal resources throughout New Mexico on statewide, regional, and area-specific scales; (2) developing a strong community of in-state geothermal energy research and development professionals and practitioners; and (3) elevating the level of awareness of geothermal energy potential among commerce, industry, and the general public. Future prospects for the state are presented.

  4. The Adsorption and Desorption of Pb(2+) and Cd(2+) in Freeze-Thaw Treated Soils.

    PubMed

    Li, Linhui; Ma, Jincai; Xu, Meng; Li, Xu; Tao, Jiahui; Wang, Guanzhu; Yu, Jitong; Guo, Ping

    2016-01-01

    Adsorption and desorption are important processes that influence the potential toxicity and bioavailability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35°C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb(2+) and Cd(2+) in freeze-thaw treated soils was studied. The adsorption amounts of Pb(2+) and Cd(2+) in freeze-thaw treated soils were smaller than those in unfrozen soils (p < 0.05), due to the fact that pH, cation exchange capacity, organic matter content, free iron oxide content, and CaCO3 content in freeze-thaw treated soils were smaller than those in unfrozen soils. The adsorption amounts of Pb(2+) and Cd(2+) in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb(2+) and Cd(2+) in unfrozen soils were smaller than those in freeze-thaw treated soils (p < 0.05). The desorption percentages of Pb(2+) and Cd(2+) were smaller in soils treated with lower freezing temperatures than those in soils treated with higher freezing temperatures. The results obtained highlight the change of the adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China.

  5. Status of the INL high-temperature electrolysis research program –experimental and modeling

    SciTech Connect

    J. E. O'Brien; C. M. Stoots; M. G. McKellar; E. A. Harvego; K. G. Condie; G. K. Housley; J. S. Herring; J. J. Hartvigsen

    2009-04-01

    This paper provides a status update on the high-temperature electrolysis (HTE) research and development program at the Idaho National Laboratory (INL), with an overview of recent large-scale system modeling results and the status of the experimental program. System analysis results have been obtained using the commercial code UniSim, augmented with a custom high-temperature electrolyzer module. The process flow diagrams for the system simulations include an advanced nuclear reactor as a source of high-temperature process heat, a power cycle and a coupled steam electrolysis loop. Several reactor types and power cycles have been considered, over a range of reactor coolant outlet temperatures. In terms of experimental research, the INL has recently completed an Integrated Laboratory Scale (ILS) HTE test at the 15 kW level. The initial hydrogen production rate for the ILS test was in excess of 5000 liters per hour. Details of the ILS design and operation will be presented. Current small-scale experimental research is focused on improving the degradation characteristics of the electrolysis cells and stacks. Small-scale testing ranges from single cells to multiple-cell stacks. The INL is currently in the process of testing several state-of-the-art anode-supported cells and is working to broaden its relationship with industry in order to improve the long-term performance of the cells.

  6. Thermal desorption of PCBs from contaminated soil with copper dichloride.

    PubMed

    Liu, Jie; Qi, Zhifu; Li, Xiaodong; Chen, Tong; Buekens, Alfons; Yan, Jianhua; Ni, Mingjiang

    2015-12-01

    Copper dichloride is an important catalyst both in the dechlorination of chlorinated aromatic compounds and the formation of PCDD/Fs. The effect of copper dichloride on polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) was studied in treated soil and off gas after thermal desorption of PCB-contaminated soil at 300, 400, 500, 600 °C. The presence of copper dichloride clearly enhances thermal desorption by promoting PCBs removal, destruction, and dechlorination. After thermal treatment at 600 °C for 1 h, the removal efficiency and destruction efficiency for PCBs reached 98.1 and 93.9%, respectively. Compared with the positive influence on PCBs, copper dichloride catalyzed large amount of PCDFs formation at 300 °C, with the concentration ratio of 2.35. The effect of CuCl2 on PCDFs formation weakened with the rising temperature since PCDFs destruction became dominant under higher temperature. Different from PCDFs, PCDDs concentration in treated soil and off gas decreased continuously with the increasing temperature. PMID:26233752

  7. Thermal desorption of PCBs from contaminated soil with copper dichloride.

    PubMed

    Liu, Jie; Qi, Zhifu; Li, Xiaodong; Chen, Tong; Buekens, Alfons; Yan, Jianhua; Ni, Mingjiang

    2015-12-01

    Copper dichloride is an important catalyst both in the dechlorination of chlorinated aromatic compounds and the formation of PCDD/Fs. The effect of copper dichloride on polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) was studied in treated soil and off gas after thermal desorption of PCB-contaminated soil at 300, 400, 500, 600 °C. The presence of copper dichloride clearly enhances thermal desorption by promoting PCBs removal, destruction, and dechlorination. After thermal treatment at 600 °C for 1 h, the removal efficiency and destruction efficiency for PCBs reached 98.1 and 93.9%, respectively. Compared with the positive influence on PCBs, copper dichloride catalyzed large amount of PCDFs formation at 300 °C, with the concentration ratio of 2.35. The effect of CuCl2 on PCDFs formation weakened with the rising temperature since PCDFs destruction became dominant under higher temperature. Different from PCDFs, PCDDs concentration in treated soil and off gas decreased continuously with the increasing temperature.

  8. A photoelectron spectroscopy and thermal desorption study of CO on FeAl(110) and polycrystalline TiAl and NiAl

    NASA Astrophysics Data System (ADS)

    Gleason, N. R.; Strongin, D. R.

    1993-10-01

    Research presented in this paper investigates the electronic properties and surface reactivity of FeAl(110) and polycrystalline TiAl and NiAl toward carbon monoxide. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) have been used to characterize the electronic structure of the clean and CO-exposed surfaces. Temperature programmed desorption (TPD) shows CO desorption states below 470 K on all the aluminide surfaces. UPS shows that CO adsorption is molecular on FeAl(110) and NiAl at 130 and 200 K, respectively. The majority of CO is found to be dissociated on TiAl at 200 K. Adsorption of CO on FeAl(110) at 315 K results in both molecular and dissociated species, as determined by XPS. Heating this CO/FeAl(110) system results in further dissociation and CO desorption near 430 K. XPS data suggests that surface oxygen, resulting from CO dissociation, preferentially binds to the aluminum component.

  9. Quantitative analysis of desorption and decomposition kinetics of formic acid on Cu(111): The importance of hydrogen bonding between adsorbed species

    SciTech Connect

    Shiozawa, Yuichiro; Koitaya, Takanori; Mukai, Kozo; Yoshimoto, Shinya; Yoshinobu, Jun

    2015-12-21

    Quantitative analysis of desorption and decomposition kinetics of formic acid (HCOOH) on Cu(111) was performed by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and time-resolved infrared reflection absorption spectroscopy. The activation energy for desorption is estimated to be 53–75 kJ/mol by the threshold TPD method as a function of coverage. Vibrational spectra of the first layer HCOOH at 155.3 K show that adsorbed molecules form a polymeric structure via the hydrogen bonding network. Adsorbed HCOOH molecules are dissociated gradually into monodentate formate species. The activation energy for the dissociation into monodentate formate species is estimated to be 65.0 kJ/mol at a submonolayer coverage (0.26 molecules/surface Cu atom). The hydrogen bonding between adsorbed HCOOH species plays an important role in the stabilization of HCOOH on Cu(111). The monodentate formate species are stabilized at higher coverages, because of the lack of vacant sites for the bidentate formation.

  10. Quantitative analysis of desorption and decomposition kinetics of formic acid on Cu(111): The importance of hydrogen bonding between adsorbed species

    NASA Astrophysics Data System (ADS)

    Shiozawa, Yuichiro; Koitaya, Takanori; Mukai, Kozo; Yoshimoto, Shinya; Yoshinobu, Jun

    2015-12-01

    Quantitative analysis of desorption and decomposition kinetics of formic acid (HCOOH) on Cu(111) was performed by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and time-resolved infrared reflection absorption spectroscopy. The activation energy for desorption is estimated to be 53-75 kJ/mol by the threshold TPD method as a function of coverage. Vibrational spectra of the first layer HCOOH at 155.3 K show that adsorbed molecules form a polymeric structure via the hydrogen bonding network. Adsorbed HCOOH molecules are dissociated gradually into monodentate formate species. The activation energy for the dissociation into monodentate formate species is estimated to be 65.0 kJ/mol at a submonolayer coverage (0.26 molecules/surface Cu atom). The hydrogen bonding between adsorbed HCOOH species plays an important role in the stabilization of HCOOH on Cu(111). The monodentate formate species are stabilized at higher coverages, because of the lack of vacant sites for the bidentate formation.

  11. Investigation of water and hydroxyl groups associated with coal fly ash by thermal desorption and fourier transform infrared photoacoustic spectroscopies

    SciTech Connect

    Seaverson, L.M.; McClelland, J.F.; Burnet, G.; Anderegg, J.W.; Iles, M.K.

    1985-01-01

    Thermal desorption spectrometry (TDS) and Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) have been used in combination to analyze the water and hydroxyl groups associated with four coal fly ashes. Measurements using the former technique on these ashes resulted in identification of three water desorption regions in the temperature range from 25/sup 0/ to 1100/sup 0/C. The regions consisted of a small desorption peak at 50/sup 0/, a broad band from 180/sup 0/ to 400/sup 0/, and an intense peak from 400/sup 0/ to 590/sup 0/. No additional water desorption was observed up to 1100/sup 0/. A fourth ash gave a similar spectrum except that it lacked the intense last peak. The TDS spectra together with FT-IR/PAS spectra taken on samples exposed to pre- and post-desorption peak temperatures allowed the first TDS peak to be assigned to the desorption of physically adsorbed water, the broad band to desorption of hydrogenbonded surface hydroxyls, and the intense last peak to the decomposition of Ca(OH)/sub 2/.

  12. 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

  13. A thermal desorption spectroscopy study of hydrogen trapping in polycrystalline α-uranium

    SciTech Connect

    Lillard, R. S.; Forsyth, R. T.

    2015-03-14

    The kinetics of hydrogen desorption from polycrystalline α-uranium (α-U) was examined using thermal desorption spectroscopy (TDS). The goal was to identify the major trap sites for hydrogen and their associated trap energies. In polycrystalline α-U six TDS adsorption peaks were observed at temperatures of 521 K, 556 K, 607 K, 681 K, 793 K and 905 K. In addition, the desorption was determined to be second order based on peak shape. The position of the first three peaks was consistent with desorption from UH3. To identify the trap site corresponding to the high temperature peaks the data were compared to a plastically deformed sample and a high purity single crystal sample. The plastically deformed sample allowed the identification of trapping at dislocations while the single crystal sample allow for the identification of high angle boundaries and impurities. Thus, with respect to the desorption energy associated with each peak, values between 12.9 and 26.5 kJ/mole were measured.

  14. Ion desorption from frozen H 2O irradiated by MeV heavy ions

    NASA Astrophysics Data System (ADS)

    Collado, V. M.; Farenzena, L. S.; Ponciano, C. R.; Silveira, E. F. da; Wien, K.

    2004-10-01

    Nitrogen (0.13-0.85 MeV) and 252Cf fission fragments (˜65 MeV) beams are employed to sputter positive and negative secondary ions from frozen water. Desorption yields are measured for different ice temperatures and projectile energies. Target surface is continuously refreshed by condensed water while the target temperature varies and ice thickness changes. In both projectile energy ranges, the preferentially ejected ions are H +, H2+ and (H 2O) nH +-cluster ions. The yields of the corresponding negative ions H - and (H 2O) nO - or (H 2O) nOH - are 1-2 orders of magnitude lower. The (H 2O) nH + desorption yields decrease exponentially as the cluster size, n, increases. In the low energy range, the desorption of positive ion clusters may occur in a two-step process: first, desorption of preformed H 2O clusters and, then, ionization by H + or H 3O + capture. For 0.81 MeV N + projectile ions, the cluster ion emission contributes with 0.05% to the total H 2O desorbed yield. There are indications that emission of the (H 2O) nH + disappears for an electronic energy loss lower than 20 eV/Å. For the high energy range, desorption of small ion clusters is particularly enhanced, revealing that a fragmentation process also exists.

  15. A thermal desorption spectroscopy study of hydrogen trapping in polycrystalline α-uranium

    DOE PAGES

    Lillard, R. S.; Forsyth, R. T.

    2015-03-14

    The kinetics of hydrogen desorption from polycrystalline α-uranium (α-U) was examined using thermal desorption spectroscopy (TDS). The goal was to identify the major trap sites for hydrogen and their associated trap energies. In polycrystalline α-U six TDS adsorption peaks were observed at temperatures of 521 K, 556 K, 607 K, 681 K, 793 K and 905 K. In addition, the desorption was determined to be second order based on peak shape. The position of the first three peaks was consistent with desorption from UH3. To identify the trap site corresponding to the high temperature peaks the data were compared tomore » a plastically deformed sample and a high purity single crystal sample. The plastically deformed sample allowed the identification of trapping at dislocations while the single crystal sample allow for the identification of high angle boundaries and impurities. Thus, with respect to the desorption energy associated with each peak, values between 12.9 and 26.5 kJ/mole were measured.« less

  16. 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 σ1=7.0×10-17 cm2 and σ2=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^2Σ^+ to{X}^2 Pi γ-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 τ≈160 μs is estimated.

  17. Easy and accurate calculation of programmed temperature gas chromatographic retention times by back-calculation of temperature and hold-up time profiles.

    PubMed

    Boswell, Paul G; Carr, Peter W; Cohen, Jerry D; Hegeman, Adrian D

    2012-11-01

    Linear retention indices are commonly used to identify compounds in programmed-temperature gas chromatography (GC), but they are unreliable unless the original experimental conditions used to measure them are stringently reproduced. However, differences in many experimental conditions may be properly taken into account by calculating programmed-temperature retention times of compounds from their measured isothermal retention vs. temperature relationships. We call this approach "retention projection". Until now, retention projection has been impractical because it required very precise, meticulous measurement of the temperature vs. time and hold-up time vs. temperature profiles actually produced by a specific GC instrument to be accurate. Here we present a new, easy-to-use methodology to precisely measure those profiles: we spike a sample with 25 n-alkanes and use their measured, programmed-temperature retention times to precisely back-calculate what the instrument profiles must have been. Then, when we use those back-calculated profiles to project retention times of 63 chemically diverse compounds, we found that the projections are extremely accurate (e.g. to ±0.9 s in a 40 min ramp). They remained accurate with different temperature programs, GC instruments, inlet pressures, flow rates, and with columns taken from different batches of stationary phase while the accuracy of retention indices became worse the more the experimental conditions were changed from the original ones used to measure them. We also developed new, open-source software (http://www.retentionprediction.org/gc) to demonstrate the system.

  18. Electronic Desorption of gas from metals

    SciTech Connect

    Molvik, A W; Kollmus, H; Mahner, E; Covo, M K; Bender, M; Bieniosek, F M; Kramer, A; Kwan, J; Prost, L; Seidl, P A; Westenskow, G

    2006-11-02

    During heavy ion operation in several particle accelerators world-wide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion induced gas desorption scales with the electronic energy loss (dE{sub e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

  19. Laser-induced desorption from sapphire surfaces

    SciTech Connect

    Hamza, A.V.; Schildbach, M.A.

    1992-03-01

    Laser-induced desorption of energetic ({approximately}7eV) aluminum ions was observed from clean and water-covered sapphire (1102) surfaces using time-of-flight mass spectrometry with laser wavelengths of 1064, 355, and 266 nm. In sharp contrast, O{sup +} (H{sup +} and OH{sup +}) ions were observed in electron-induced desorption measurements with 300 eV electrons from the bare (water- covered) (1102) surface. Sapphire surfaces were characterized with low energy electron diffraction, reflection electron energy loss spectroscopy, and Auger electron spectroscopy. 8 refs.

  20. 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

  1. Kinetic Interpretation of Water Vapor Adsorption-Desorption Behavior of a Desiccant Rotor Showing S-shaped Adsorption Isotherm

    NASA Astrophysics Data System (ADS)

    Okamoto, Kumiko; Oshima, Kazunori; Takewaki, Takahiko; Kodama, Akio

    Adsorption / desorption behavior of water vapor in a desiccant rotor containing an iron aluminophosphate type zeolite FAM-Z01 (Functional Adsorbent Material Zeolite 01) was experimentally investigated for humidity swing. This rotor exhibited an S-shaped adsorption isotherm with its temperature dependence. Humidity swing, using a small piece of the rotor, could be usefully applied to interpret adsorption / desorption mechanisms by observing their rates. The most significant finding was that the adsorption / desorption rates in humidity swing could be described by the amount of adsorption, temperature and amplitude of the humidity swing, not by cycle time. Also, using the liner driving force (LDF) model, the overall mass transfer coefficient changed with the elapse of time or with the amount of adsorbed water. This implied that the LDF model, considering constant value of the overall mass transfer coefficient, was probably unable to explain the water adsorption / desorption behavior of FAM-Z01 desiccant rotor.

  2. Adsorption and desorption of SO2, NO and chlorobenzene on activated carbon.

    PubMed

    Li, Yuran; Guo, Yangyang; Zhu, Tingyu; Ding, Song

    2016-05-01

    Activated carbon (AC) is very effective for multi-pollutant removal; however, the complicated components in flue gas can influence each other's adsorption. A series of adsorption experiments for multicomponents, including SO2, NO, chlorobenzene and H2O, on AC were performed in a fixed-bed reactor. For single-component adsorption, the adsorption amount for chlorobenzene was larger than for SO2 and NO on the AC. In the multi-component atmosphere, the adsorption amount decreased by 27.6% for chlorobenzene and decreased by 95.6% for NO, whereas it increased by a factor of two for SO2, demonstrating that a complex atmosphere is unfavorable for chlorobenzene adsorption and inhibits NO adsorption. In contrast, it is very beneficial for SO2 adsorption. The temperature-programmed desorption (TPD) results indicated that the binding strength between the gas adsorbates and the AC follows the order of SO2>chlorobenzene > NO. The adsorption amount is independent of the binding strength. The presence of H2O enhanced the component effects, while it weakened the binding force between the gas adsorbates and the AC. AC oxygen functional groups were analyzed using TPD and X-ray photoelectron spectroscopy (XPS) measurements. The results reveal the reason why the chlorobenzene adsorption is less affected by the presence of other components. Lactone groups partly transform into carbonyl and quinone groups after chlorobenzene desorption. The chlorobenzene adsorption increases the number of C=O groups, which explains the positive effect of chlorobenzene on SO2 adsorption and the strong NO adsorption.

  3. Direct aqueous injection with backflush thermal desorption for wastewater monitoring by online GC-MS.

    PubMed

    Ziemer, W; Wortberg, M; Eichberger, C; Gerstel, J; Kerl, W

    2010-06-01

    A gas chromatography-mass spectrometry system with a novel injector type, which is designed for direct aqueous injection of wastewater, is presented. The system is used for online monitoring of the influent of the wastewater treatment plant at BASF's main chemical production site in Ludwigshafen, Germany. The purpose of monitoring is to protect the biological treatment process and the receiving water body, the Rhine. The modular system is primarily based on commercial equipment, but utilizes a special injection system, which is connected to a Deans switch. The two-stage injector consists of a programmable temperature vaporizer (PTV) injector with a small volume insert for vaporization and a dual sorbent packed second PTV for analyte adsorption/desorption. The Deans switch allows a backflush/thermal desorption operation which enables the direct injection of filtered, crude wastewater. About 170 volatile and semivolatile compounds are calibrated with approximate detection limits of 1 mg/L, which are sufficient for the analysis of untreated wastewater. The quantitative results are transferred to a database which is connected to a process control system. If the wastewater does not meet the required specification, an alarm is generated and the wastewater is diverted into a storage basin. Special software programs and routines allow for reliable, unattended operation and remote instrument control. Data quality is automatically controlled in each run and through the daily analysis of quality control samples. The current design allows for analysis of volatile compounds, such as methanol, whereas an earlier injector setup restricted the range of analytes to less volatile compounds (of size C(4) or greater).

  4. Deuterium thermal desorption from vacancy clusters in tungsten

    NASA Astrophysics Data System (ADS)

    Ryabtsev, S.; Gasparyan, Yu.; Zibrov, M.; Shubina, A.; Pisarev, A.

    2016-09-01

    Deuterium interaction with vacancy clusters in tungsten was studied by means of thermal desorption spectroscopy (TDS). A recrystallized W foil was used as a sample, and the vacancy clusters were formed in the bulk by irradiation with 10 keV/D ions to the fluence of 3 × 1019 D/m2 and subsequent annealing at the temperature of 800 K. Then the sample was loaded with deuterium (0.67 keV/D ions with a fluence of 1 × 1019 D/m2), and TDS measurements with varying heating rates β in the range of 0.25-4 K/s were performed. The high temperature peak with the maximum at around 700 K was attributed to deuterium desorption from vacancy clusters and the detrapping energy for this type of defects was determined from the slope of the Arrhenius-like plot ln (β / Tm2) versus 1 /Tm , where Tm is the peak position. The detrapping energy calculated this way is 2.10 ± 0.02 eV.

  5. Purex canyon exhaust fan bearing temperature monitoring system doric 245 datalogger programming

    SciTech Connect

    Blackaby, W.B.

    1994-09-06

    A micro-processor based datalogger is used to monitor, display, and log seventeen RTD temperature channels. Five bearings are monitored for each of the three electric motor-fan assemblies and two bearings are monitored on the steam turbine unit. Several alarms per data channel (a High alarm at 236 degrees and a High High alarm at 246 degrees F) will alert the operation`s staff to increasing abnormal bearing temperatures. This procedure is cross-referenced to the manufacturers manual. All programming steps will have the following footnote: Mpg x-xx. The Mpg refers to the Manual page, with x as the section number and xx as the page number in that section. When more information is needed, such as pictures or details, then the manual section and page number is provided.

  6. Desorption of Ag from Grain Boundaries in Ag Film on Br and H-Passivated Si(111) Surfaces

    SciTech Connect

    Roy, Anupam; Batabyal, R.; Mahato, J. C.; Dev, B. N.; Sundaravel, B.

    2011-07-15

    Growth of Ag film on Br- and H-passivated Si(111) surfaces was examined by Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and photoemission electron microscopy (PEEM) techniques. The phenomenon of thermal grooving was observed after annealing at higher temperatures. Hierarchical desorption of Ag from the grain boundaries produce a fractal structure of Ag-depleted regions. Hierarchical desorption may be used for nanopatterning of the layer.

  7. Reaction kinetics for the oxygen hydrogenation process on Pt(111) derived from temperature-programmed XPS

    NASA Astrophysics Data System (ADS)

    Näslund, Lars-Åke

    2013-12-01

    Oxygen hydrogenation under ultra high vacuum conditions at the platinum surface was explored using temperature-programmed X-ray photoelectron spectroscopy. Through modeling of the oxygen consumption, information on the reaction kinetics was obtained indicating that the reaction rate of the oxygen hydrogenation process depends on the hydrogen diffusion and on the lifetime of hydroxyl intermediates. The reaction rate is, however, enhanced when an autocatalytic process stabilizes the hydroxyl intermediates through hydrogen bonding to neighboring water molecules. The overall activation energy for the hydrogenation of atomic oxygen to form water was determined to be 0.20 eV with a frequency factor of only 103 s- 1.

  8. 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.

  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. 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

  11. Effects of breeder feeding restriction programs and incubation temperatures on progeny footpad development.

    PubMed

    Da Costa, M J; Oviedo-Rondón, E O; Wineland, M J; Wilson, J; Montiel, E

    2014-08-01

    Footpad dermatitis begins early in life, and there is evidence of individual susceptibility. An experiment was conducted to evaluate the carryover effects of breeder feed restriction programs and incubation temperatures (TEM) on progeny footpad development at hatch, and 7 and 22 d. Cobb 500 fast feathering breeders were subjected to 2 dietary feed restriction programs during rearing: skip-a-day (SAD) and every-day feeding (EDF). At 60 wk of age, eggs from each group were collected and incubated according to 2 TEM, standard (S) eggshell temperature (38.1°C) and early-low late-high (LH). This second profile had low (36.9°C) eggshell temperature for the first 3 d, and standard temperature until the last 3 d when eggs were subjected to elevated (38.9°C) eggshell temperature. At hatch, 15 chicks from each treatment combination were sampled to obtain footpads for histological analysis. Seventy-two chicks per treatment were placed in 48 cages (6/cage), and raised to 22 d. At 7 and 22 d, 1 and 2 chickens, respectively, were sampled for footpads. The BW and group feed intake were recorded to obtain BW gain and feed conversion ratio at 7 and 21 d. Histological analysis assessed thickness and total area of stratus corneum (SC), epidermis, and dermis, and total papillae height. Data were analyzed as randomized complete block design in a 2 × 2 factorial arrangement of treatments. There was a negative effect of LH TEM on performance at both ages. An interaction effect on SC area and papillae height was observed at hatch. Additionally, SAD treatment increased thickness and area of footpad dermis. At 7 d, the SC parameters of the SAD progeny were increased. Epidermis thickness was affected by treatment interaction. Furthermore, LH TEM decreased epidermis thickness and dermis area. At 22 d, interaction effects were observed in thickness and area of SC and epidermis. Incubation S TEM increased thickness and area of dermis. It was concluded that breeder feed restriction programs

  12. Quantum theory of laser-stimulated desorption

    NASA Technical Reports Server (NTRS)

    Slutsky, M. S.; George, T. F.

    1978-01-01

    A quantum theory of laser-stimulated desorption (LSDE) is presented and critically analyzed. It is shown how LSDE depends on laser-pulse characteristics and surface-lattice dynamics. Predictions of the theory for a Debye model of the lattice dynamics are compared to recent experimental results.

  13. A microsystems enabled field desorption source.

    SciTech Connect

    Hertz, Kristin L.; Resnick, Paul James; Schwoebel, Paul R.; Holland, Christopher E.; Chichester, David L.

    2010-07-01

    Technologies that have been developed for microelectromechanical systems (MEMS) have been applied to the fabrication of field desorption arrays. These techniques include the use of thick films for enhanced dielectric stand-off, as well as an integrated gate electrode. The increased complexity of MEMS fabrication provides enhanced design flexibility over traditional methods.

  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. Film growth, adsorption and desorption kinetics of indigo on SiO2

    PubMed Central

    Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

    2015-01-01

    Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer des orption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption. PMID:24832297

  16. APPLICATION OF THERMAL DESORPTION TECHNOLOGIES TO HAZARDOUS WASTE SITES

    EPA Science Inventory

    Thermal desorption is a separation process frequently used to remediate many Superfund sites. Thermal desorption technologies are recommended and used because of (1) the wide range of organic contaminants effectively treated, (2) availability and mobility of commercial systems, ...

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

    SciTech Connect

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

    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.

  18. A computer program for engineering assessment of alloy corrosion in complex, high temperature gases

    SciTech Connect

    John, R.C.; Young, A.L.; Thompson, W.T.

    1997-08-01

    A user-friendly Windows program has been developed with the capability to assess corrosion of commercial alloys in complex gases at high temperatures. Thermochemical predictions of the stable alloy corrosion products are used to infer the likely corrosion mechanism. Regression analysis is used to produce correlations of alloy corrosion with exposure conditions. A large data collection has been compiled and represents nearly 4.7 million hours of exposure time for 71 alloys. The data represent total metal penetration (sound metal loss by surface scale plus internal corrosion) and have been collected from public plus private sources representing a time period of nearly 40 years. The data originate from well-defined exposures with known concentrations of H{sub 2}, H{sub 2}S, H{sub 2}O, CO, CO{sub 2}, COS, O{sub 2}, N{sub 2} and CH{sub 4}, temperature, exposure time, and alloy. A large amount of information is now available to predict corrosion for the conditions of interest. The capabilities of the program are reviewed in this presentation for corrosion by oxidation, sulfidation, oxidation/sulfidation, and carburization.

  19. 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

  20. 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.

  1. Comprehensive two-dimensional gas chromatographic separations with a temperature programmed microfabricated thermal modulator.

    PubMed

    Collin, William R; Nuñovero, Nicolas; Paul, Dibyadeep; Kurabayashi, Katsuo; Zellers, Edward T

    2016-04-29

    Comprehensive two-dimensional gas chromatography (GC×GC) with a temperature-programmed microfabricated thermal modulator (μTM) is demonstrated. The 0.78 cm(2), 2-stage μTM chip with integrated heaters and a PDMS coated microchannel was placed in thermal contact with a solid-state thermoelectric cooler and mounted on top of a bench scale GC. It was fluidically coupled through heated interconnects to an upstream first-dimension ((1)D) PDMS-coated capillary column and a downstream uncoated capillary or second-dimension ((2)D) PEG-coated capillary. A mixture of n-alkanes C6-C10 was separated isothermally and the full-width-at-half-maximum (fwhm) values of the modulated peaks were assessed as a function of the computer-controlled minimum and maximum stage temperatures of μTM, Tmin and Tmax, respectively. With Tmin and Tmax fixed at -25 and 100°C, respectively, modulated peaks of C6 and C7 had fwhm values<53 ms while the modulated peaks of C10 had a fwhm value of 1.3s, due to inefficient re-mobilization. With Tmin and Tmax fixed at 0 and 210°C, respectively, the fwhm value for the modulated C10 peaks decreased to 67 ms, but C6 and C7 exhibited massive breakthrough. By programming Tmin from -25 to 0°C and Tmax from 100 to 220°C, the C6 and C7 peaks had fwhm values≤50 ms, and the fwhm for C10 peaks remained<95 ms. Using the latter conditions for the GC×GC separation of a sample of unleaded gasoline yielded resolution similar to that reported with a commercial thermal modulator. Replacing the PDMS phase in the μTM with a trigonal-tricationic room temperature ionic liquid eliminated the bleed observed with the PDMS, but also reduced the capacity for several test compounds. Regardless, the demonstrated capability to independently temperature program this low resource μTM enhances its versatility and its promise for use in bench-scale GC×GC systems.

  2. Adsorption and desorption studies of lysozyme by Fe3O4-polymer nanocomposite via fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Koc, Kenan; Alveroglu, Esra

    2015-06-01

    The work have been undertaken in this study is to synthesis and characterize Fe3O4-polymer nanocomposites which are having different morphological properties. Also, investigation of the adsorption and desorption behaviour of lysozyme onto Fe3O4-polymer nanocomposites have been studied. Fe3O4 nanoparticles, synthesized by in situ in polyacrylamide hydrogels, show super-paramagnetic behaviour and saturation magnetization of composite material have been tuned by changing the hydrogel conformation. Adsorption and desorption studies of lysozyme were followed by using pure water at room temperature via fluorescence measurements. Fluorescence measurements showed that, the composite materials adsorbed lysozyme molecules less than 20 s and higher monomer concentration of composite materials cause faster adsorption. Besides, structure of lysozyme molecules were not changed during the adsorption and desorption. As a result Fe3O4-polymer nanocomposites could be used for drug delivery, protein separation and PAAm gels could be used for synthesis of magnetic composites with varying magnetic properties.

  3. 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.

  4. Method of enhancing selective isotope desorption from metals

    DOEpatents

    Knize, R.J.; Cecchi, J.L.

    1983-07-26

    This invention relates generally to the field of gas desorption from metals; and, more particularly, to a method of enhancing the selective desorption of a particular isotope of a gas from metals. Enhanced selective desorption is especially useful in the operation of fusion devices.

  5. Evaluation of GeO desorption behavior in the metalGeO(2)Ge structure and its improvement of the electrical characteristics.

    PubMed

    Oniki, Yusuke; Koumo, Hideo; Iwazaki, Yoshitaka; Ueno, Tomo

    2010-06-15

    The relation between germanium monoxide (GeO) desorption and either improvement or deterioration in electrical characteristics of metalGeO(2)Ge capacitors fabricated by thermal oxidation has been investigated. In the metalGeO(2)Ge stack, two processes of GeO desorption at different sites and at different temperatures were observed by thermal desorption spectroscopy measurements. The electrical characteristics of as-oxidized metalGeO(2)Ge capacitors shows a large flat-band voltage shift and minority carrier generation due to the GeO desorption from the GeO(2)Ge interface during oxidation of Ge substrates. On the other hand, the electrical properties were drastically improved by a postmetallization annealing at low temperature resulting in a metal catalyzed GeO desorption from the top interface.

  6. Desorption Kinetics of H2O from Cab-O-Sil-M-7D and Hi-Sil-233 Silica Particles

    SciTech Connect

    Dinh, L.; Balooch, M.; LeMay, J.D.

    2000-01-26

    Temperature programmed desorption (TPD) was performed at temperatures up to 850K on Cab-O-Sil-M-7D and Hi-Sil-233 silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 9-14.5 kcal/mol. However, the activation energies of desorption for chemisorbed water varied from {approx} 19 kcal/mol to > 59 kcal/mol for Cab-O-Sil-M-7D, and {approx} 23-37 kcal/mol for Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>30 kcal/mol) will not escape the silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (19-26 kcal/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies < 30 kcal/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1-0.4 wt. % of water in M9787 polysiloxane formulations containing {approx} 21% Cab-O-Sil-M-7D and {approx} 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that absorbed H{sub 2}O and Si-OH bonds on the silica surfaces are the major contributors to water outgassing from M97 series silicones.

  7. 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.

  8. Reduction of acrylamide level in french fries by employing a temperature program during frying.

    PubMed

    Palazoglu, T Koray; Gökmen, Vural

    2008-08-13

    In this study, the effect of employing an oil temperature program during frying on the acrylamide content of French fries was investigated. The frying conditions that could lead to lower acrylamide levels in French fries were first simulated by means of an experimentally validated frying model. Then, experiments were conducted to test the simulated conditions in real frying process. Different time/temperature combinations (4 min at 170 degrees C, 2 min at 170 degrees C + 2 min at 150 degrees C, 1 min at 170 degrees C + 3 min at 150 degrees C, 1 min at 190 degrees C + 3 min at 150 degrees C) were employed for frying potato strips (8.5 x 8.5 x 70 mm), and the resultant acrylamide levels were determined with a gas chromatography-mass spectrometry (GC-MS) method. The results indicated that acrylamide levels in French fries can be reduced by half if the final stage of the frying process employs a lower oil temperature. Therefore, the method appears to be an effective way of controlling the acrylamide level in the final product.

  9. Hydrogen adsorption and coadsorption with CO on well-defined bimetallic PtRu surfaces a model study on the CO tolerance of bimetallic PtRu anode catalysts in low temperature polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Diemant, T.; Hager, T.; Hoster, H. E.; Rauscher, H.; Behm, R. J.

    2003-09-01

    The influence of PtRu surface alloy formation and of coadsorbed CO on the adsorption/desorption characteristics of hydrogen on bimetallic PtRu surfaces was investigated by temperature programmed desorption, using a 40% Pt containing PtRu surface alloy pseudomorphic on a Ru(0 0 0 1) surface with an almost statistical distribution of Pt surface atoms as substrate. Alloy formation leads to a significant broadening of the desorption peak compared to pure Ru, together with a considerable down-shift in the onset of desorption. This trend is even more pronounced in the presence of coadsorbed CO. The weakening of the hydrogen adsorption bond is attributed mainly to strain effects, imposed by the considerable compression of the pseudomorphic Pt as compared to bulk Pt(1 1 1). Finally we discuss the implications of these results for the mechanistic understanding of the improved performance of PtRu anode catalysts in reformate operated polymer electrolyte fuel cells.

  10. A general strategy for performing temperature-programming in high performance liquid chromatography--further improvements in the accuracy of retention time predictions of segmented temperature gradients.

    PubMed

    Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

    2012-01-27

    In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention times based on temperature-gradient as well as isothermal input data was investigated. For a small temperature interval of ΔT=40°C, both approaches result in very similar predictions. Average relative errors of predicted retention times of 2.7% and 1.9% were observed for simulations based on isothermal and temperature-gradient measurements, respectively. Concurrently, it was investigated whether the accuracy of retention time predictions of segmented temperature gradients can be further improved by temperature dependent calculation of the parameter S(T) of the LES relationship. It was found that the accuracy of retention time predictions of multi-step temperature gradients can be improved to around 1.5%, if S(T) was also calculated temperature dependent. The adjusted experimental design making use of four temperature-gradient measurements was applied for systematic method development of selected food additives by high-temperature liquid chromatography. Method development was performed within a temperature interval from 40°C to 180°C using water as mobile phase. Two separation methods were established where selected food additives were baseline separated. In addition, a good agreement between simulation and experiment was observed, because an average relative error of predicted retention times of complex segmented temperature gradients less than 5% was observed. Finally, a schedule of recommendations to assist the practitioner during systematic method development in high-temperature liquid chromatography was established.

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

    SciTech Connect

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

    2008-08-01

    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 with high efficiency (the Supercritical Water Reactor-SCWR and the Very High Temperature Reactor-VHTR). Three employ a fast neutron spectrum to enable more effective management of actinides through recycling of most components in the discharged fuel (the Gas-cooled Fast Reactor-GFR, the Lead-cooled Fast Reactor-LFR, and the Sodium-cooled Fast Reactor-SFR). The Molten Salt Reactor (MSR) employs a circulating liquid fuel mixture that offers considerable flexibility for recycling actinides and may provide an alternative to accelerator-driven systems. At the inception of DOE's Gen IV program, it was decided to significantly pursue five of the six concepts identified in the Gen IV roadmap to determine which of them was most appropriate to meet the needs of future U.S. nuclear power generation. In particular, evaluation of the highly efficient thermal SCWR and VHTR reactors was initiated primarily for energy production, and evaluation of the three fast reactor concepts, SFR, LFR, and GFR, was begun to assess viability for both energy production and their potential contribution to closing the fuel cycle. Within the Gen IV Program itself, only the VHTR class of reactors was selected for continued development. Hence, this document will address the multiple activities under the Gen IV program that contribute to the development of the VHTR. A few major technologies have been recognized by DOE as necessary to enable the deployment of the next generation of advanced nuclear reactors, including the development and qualification of the structural

  12. Measurement of desorption energies of H 2 and CO from SS-304 LN and inconel 625 surfaces by laser induced thermal desorption

    NASA Astrophysics Data System (ADS)

    Tagle, J. A.; Pospieszczyk, A.

    Stainless steel (AISI 304 LN) and Inconel 625 surfaces have been exposed to different pressures of H 2 and CO in the temperature range of 300-473 K. A laser heating technique for studying fast surface processes was applied to determine the desorption energies of these gasses from SS 304 LN and Inconel 625 surfaces. The Clausius-Clapeyron plots give a desorption energy value of 97 kJ mol -1 for H 2/SS 304 LN and 77.4 kJ mol -1 for H 2/Inconel 625. The adsorption of CO on these surfaces is drastically affected by the fast growing of a chromium oxide layer at the surface during the laser shots. In this case the desorption energy was determined by fitting both the experimental recoverage times and the equilibrium coverage curves. The oxide passivation layer produces a decrease of the desorption energy from 92.8 to 72.8 kJ mol -1 for CO/SS 304 LN and from 91.8 to 77.9 kJ mol -1 for CO/Inconel 625 when the oxygen surface concentration increases to 14%.

  13. Temperature-programmed sulfiding of vanadium oxides and alumina-supported vanadium oxide catalysts

    SciTech Connect

    Bonne, R.L.C.; Langeveld, A.D. van; Moulijn, J.A.

    1995-06-01

    Sulfiding of bulk and alumina-supported vanadium oxides has been studied using temperature-programmed sulfiding and reduction techniques. Bulk compounds (V{sub 2}O{sub 5}, V{sub 2}O{sub 3}) and V/Al{sub 2}O{sub 3} catalysts are sulfided via a similar mechanism. For bulk V{sub 2}O{sub 5}, two major sulfiding steps have been identified. At temperatures up to 673K, V{sub 2}O{sub 5} is reduced to V{sub 2}O{sub 3} by O-S exchange and subsequent rupture of V-S bonds where H{sub 2}S acts as reducing agent. Sulfiding to V{sub 2}S{sub 3} takes place above 673K. The catalysts are sulfided more easily than the bulk oxides due to the higher dispersion of the vanadium species. In catalysts sulfided at 673K which are still partially oxidic, four types of sulfur have been observed, viz. adsorbed H{sub 2}S, stoichiometric sulfur, S-H groups, and nonstoichiometric (excess) sulfur (S{sub x}). There are indications that (isothermal) room temperature H{sub 2}S adsorption can be used to determine the dispersion of the supported microcrystallites at higher vanadium loadings. From the present results it is inferred that alumina-supported vanadium-based catalysts, when sulfided at temperatures commonly applied in hydrotreating operations, essentially consist of an oxide, the outer surface of which is sulfided. 22 refs., 6 figs., 4 tabs.

  14. Reaction of LiD with moisture by temperature programmed reaction (TPR)

    SciTech Connect

    Dinh, L N; Balooch, M; Cecala, C M; Leckey, J H

    2000-09-14

    The temperature programmed reaction technique was performed on LiOH powders and LiD single crystals previously exposed to different moisture levels. Our results show that the LiOH decomposition process has an activation energy barrier of 30 to 33.1 kcal/mol. The LiOH structure is stable at 320 K for 100 years. However, LiOH structures formed on the surface of LiD during moisture exposure at low dosages may have multiple activation energy barriers, some of which may be much lower than 30 kcal/mol. We attribute the lowering of the activation energy barrier for the LiOH decomposition to the existence of dangling bonds, cracks, and other long range disorders in the LiOH structures formed at low levels of moisture exposure. These defective LiOH structures may decompose significantly over the next 100 years of storage even at room temperature. At high moisture exposure levels, LiOH.H{sub 2}O formation is observed. The release of H{sub 2}O molecules from LiOH.H{sub 2}O structure has small activation energy barriers in the range of 13.8 kcal/mol to 16.0 kcal/mol. The loosely bonded H{sub 2}O molecules in the LiOH.H{sub 2}O structure can be easily pumped away at room temperature in a reasonable amount of time. Our experiments also suggest that handling LiD single crystals at an elevated temperature of 340 K or more reduces the growth of LiOH and LiOH.H{sub 2}O significantly.

  15. Effect of delivery condition on desorption rate of ZrCo metal hydride bed for fusion fuel cycle

    SciTech Connect

    Kang, H.G.; Yun, S.H.; Chung, D.; Oh, Y.H.; Chang, M.H.; Cho, S.; Chung, H.; Song, K.M.

    2015-03-15

    For the safety of fusion fuel cycle, hydrogen isotope gases including tritium are stored as metal hydride form. To satisfy fueling requirement of fusion machine, rapid delivery from metal hydride bed is one of major factors for the development of tritium storage and delivery system. Desorption from metal hydride depends on the operation scenario by pressure and temperature control of the bed. The effect of operation scenario and pump performance on desorption rate of metal hydride bed was experimentally investigated using ZrCo bed. The results showed that the condition of pre-heating scenario before actual delivery of gas affected the delivery performance. Different pumps were connected to desorption line from bed and the effect of pump capacity on desorption rate were also found to be significant. (authors)

  16. Sample Desorption/Onization From Mesoporous Silica

    DOEpatents

    Iyer, Srinivas; Dattelbaum, Andrew M.

    2005-10-25

    Mesoporous silica is shown to be a sample holder for laser desorption/ionization of mass spectrometry. Supported mesoporous silica was prepared by coating an ethanolic silicate solution having a removable surfactant onto a substrate to produce a self-assembled, ordered, nanocomposite silica thin film. The surfactant was chosen to provide a desired pore size between about 1 nanometer diameter and 50 nanometers diameter. Removal of the surfactant resulted in a mesoporous silica thin film on the substrate. Samples having a molecular weight below 1000, such as C.sub.60 and tryptophan, were adsorbed onto and into the mesoporous silica thin film sample holder and analyzed using laser desorption/ionization mass spectrometry.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Lead sorption-desorption from organic residues.

    PubMed

    Duarte Zaragoza, Victor M; Carrillo, Rogelio; Gutierrez Castorena, Carmen M

    2011-01-01

    Sorption and desorption are mechanisms involved in the reduction of metal mobility and bioavailability in organic materials. Metal release from substrates is controlled by desorption. The capacity of coffee husk and pulp residues, vermicompost and cow manure to adsorb Pb2+ was evaluated. The mechanisms involved in the sorption process were also studied. Organic materials retained high concentrations of lead (up to 36,000 mg L(-1)); however, the mechanisms of sorption varied according to the characteristics of each material: degree of decomposition, pH, cation exchange capacity and percentage of organic matter. Vermicompost and manure removed 98% of the Pb from solution. Lead precipitated in manure and vermicompost, forming lead oxide (PbO) and lead ferrite (PbFe4O7). Adsorption isotherms did not fit to the typical Freundlich and Langmuir equations. Not only specific and non-specific adsorption was observed, but also precipitation and coprecipitation. Lead desorption from vermicompost and cow manure was less than 2%. For remediation of Pb-polluted sites, the application of vermicompost and manure is recommended in places with alkaline soils because Pb precipitation can be induced, whereas coffee pulp residue is recommended for acidic soils where Pb is adsorbed.

  2. 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.

  3. Light-induced atomic desorption: recent developments

    NASA Astrophysics Data System (ADS)

    Mariotti, E.; Atutov, S. N.; Biancalana, Valerio; Bocci, S.; Burchianti, A.; Marinelli, C.; Nasyrov, K. A.; Pieragnoli, B.; Moi, L.

    2001-04-01

    Light induced atomic desorption (LIAD) is an impressive manifestation of a new class of phenomena involving alkali atoms, dielectric films and light. LIAD consists of a huge emission of alkali atoms (experimentally proved for sodium, potassium, rubidium and cesium) from siloxane films when illuminated by laser or ordinary light. Most of the experiments have been performed in glass cells suitably coated by a thin film (of the order of 10 micrometer) either of poly - (dimethylsiloxane) (PDMS), a polymer, or of octamethylcyclotetrasiloxane (OCT), a crown molecule. LIAD is a combination of two processes: direct photo-desorption from the surface and diffusion within the siloxane layer. The photo-desorbed atoms are replaced by fresh atoms diffusing to the surface. Moreover, from the experimental data it comes out that the desorbing light increases atomic diffusion and hence the diffusion coefficient. To our knowledge this is the first time that such an effect is clearly observed, measured and discussed: LIAD represents a new class of photo-effects characterized by two simultaneous phenomena due to the light: surface desorption and fastened bulk diffusion.

  4. 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.

  5. Sustainable remediation of mercury contaminated soils by thermal desorption.

    PubMed

    Sierra, María J; Millán, Rocio; López, Félix A; Alguacil, Francisco J; Cañadas, Inmaculada

    2016-03-01

    Mercury soil contamination is an important environmental problem that needs the development of sustainable and efficient decontamination strategies. This work is focused on the application of a remediation technique that maintains soil ecological and environmental services to the extent possible as well as search for alternative sustainable land uses. Controlled thermal desorption using a solar furnace at pilot scale was applied to different types of soils, stablishing the temperature necessary to assure the functionality of these soils and avoid the Hg exchange to the other environmental compartments. Soil mercury content evolution (total, soluble, and exchangeable) as temperature increases and induced changes in selected soil quality indicators are studied and assessed. On total Hg, the temperature at which it is reduced until acceptable levels depends on the intended soil use and on how restrictive are the regulations. For commercial, residential, or industrial uses, soil samples should be heated to temperatures higher than 280 °C, at which more than 80 % of the total Hg is released, reaching the established legal total Hg level and avoiding eventual risks derived from high available Hg concentrations. For agricultural use or soil natural preservation, conversely, maintenance of acceptable levels of soil quality limit heating temperatures, and additional treatments must be considered to reduce available Hg. Besides total Hg concentration in soils, available Hg should be considered to make final decisions on remediation treatments and potential future uses. Graphical Abstract Solar energy use for remediation of soils affected by mercury.

  6. The Effects of Moisture on LiD Single Crystals Studied by Temperature Programmed Reaction

    SciTech Connect

    Dinh, L.; Balooch, M.; Cecala, C.M.; Leckey, J.H.

    2000-09-14

    Temperature programmed reaction (TPR) technique was performed on LiOH powders and LiD single crystals previously exposed to different moisture levels. Our results show that the LiOH decomposition process has an activation energy barrier of 30 to 33.1 kcal/mol. The LiOH structure is stable even if kept at 320 K for 100 years. However, LiOH structures formed on the surface of LiD during moisture exposure at low dosages may have multiple activation energy barriers, some of which may be much lower than 30 kcal/mol. We attribute the lowering of the activation energy barrier for the LiOH decomposition to the existence of dangling bonds, cracks, and other long range disorders in the LiOH structures formed at low levels of moisture exposure. These defective LiOH structures may decompose significantly over the next 100 years of storage even at room temperature. At high moisture exposure levels, LiOH.H{sub 2}O formation is observed. The release of H{sub 2}O molecules from LiOH.H{sub 2}O structure has small activation energy barriers in the range of 13.8 kcal/mol to 16.0 kcal/mol. The loosely bonded H{sub 2}O molecules in the LiOH.H{sub 2}O structure can be easily pumped away at room temperature in a reasonable amount of time. Our experiments also suggest that handling LiD single crystals at an elevated temperature of 340 K or more reduces the growth rate of LiOH and LiOH.H{sub 2}O significantly. Therefore, a proposed way of minimizing hydrogen formation (due to H{sub 2}O reaction with LiD) in a closed system containing LiOH in the presence of LiD may be to handle LiD at a slightly, elevated temperature during the assembly.

  7. A universal, high recovery assay for protein quantitation through temperature programmed liquid chromatography (TPLC).

    PubMed

    Orton, Dennis J; Doucette, Alan A

    2013-03-15

    As an alternative to direct UV absorbance measurements, estimation of total protein concentration is typically conducted through colorimetric reagent assays. However, for protein-limited applications, the proportion of the sample sacrificed to the assay becomes increasingly significant. This work demonstrates a method for quantitation of protein samples with high recovery. Temperature programmed liquid chromatography (TPLC) with absorbance detection at 214nm permits accurate estimation of total protein concentration from samples containing as little as 0.75μg. The method incorporates a temperature gradient from 25 to 80°C to facilitate elution of total protein into a single fraction. Analyte recovery, as measured from 1 and 10μg protein extracts of Escherichia coli, is shown to exceed 93%. Extinction coefficients at 214nm were calculated across the human proteome, providing a relative standard deviation of 21% (versus 42% at 280nm), suggesting absorbance values at 214nm provide a more consistent measure of protein concentration. These results translate to a universal protein detection strategy exhibiting a coefficient of variation below 10%. Together with the sensitivity and tolerance to contaminants, TPLC with UV detection is a favorable alternative to colorimetric assay for total protein quantitation, particularly in sample-limited applications.

  8. A universal, high recovery assay for protein quantitation through temperature programmed liquid chromatography (TPLC).

    PubMed

    Orton, Dennis J; Doucette, Alan A

    2013-03-15

    As an alternative to direct UV absorbance measurements, estimation of total protein concentration is typically conducted through colorimetric reagent assays. However, for protein-limited applications, the proportion of the sample sacrificed to the assay becomes increasingly significant. This work demonstrates a method for quantitation of protein samples with high recovery. Temperature programmed liquid chromatography (TPLC) with absorbance detection at 214nm permits accurate estimation of total protein concentration from samples containing as little as 0.75μg. The method incorporates a temperature gradient from 25 to 80°C to facilitate elution of total protein into a single fraction. Analyte recovery, as measured from 1 and 10μg protein extracts of Escherichia coli, is shown to exceed 93%. Extinction coefficients at 214nm were calculated across the human proteome, providing a relative standard deviation of 21% (versus 42% at 280nm), suggesting absorbance values at 214nm provide a more consistent measure of protein concentration. These results translate to a universal protein detection strategy exhibiting a coefficient of variation below 10%. Together with the sensitivity and tolerance to contaminants, TPLC with UV detection is a favorable alternative to colorimetric assay for total protein quantitation, particularly in sample-limited applications. PMID:23435344

  9. 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.

  10. Temperature-programmed electrospray-differential mobility analysis for characterization of ligated nanoparticles in complex media.

    PubMed

    Tsai, De-Hao; DelRio, Frank W; Pettibone, John M; Lin, Pin-Ann; Tan, Jiaojie; Zachariah, Michael R; Hackley, Vincent A

    2013-09-10

    An electrospray-differential mobility analyzer (ES-DMA) was operated with an aerosol flow-mode, temperature-programmed approach to enhance its ability to characterize the particle size distributions (PSDs) of nanoscale particles (NPs) in the presence of adsorbed and free ligands. Titanium dioxide NPs (TiO2-NPs) stabilized by citric acid (CA) or bovine serum albumin (BSA) were utilized as representative systems. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry were used to provide visual information and elemental-based PSDs, respectively. Results show that the interference resulting from electrospray-dried nonvolatile salt residual nanoscale particles (S-NPs) could be effectively reduced using the thermal treatment process: PSDs were accurately measured at temperatures above 200 °C for CA-stabilized TiO2-NPs and above 400 °C for BSA-stabilized TiO2-NPs. Moreover, TEM confirmed the volumetric shrinkage of S-NPs due to thermal treatment and also showed that the primary structure of TiO2-NPs was relatively stable over the temperature range studied (i.e., below 700 °C). Conversely, the shape factor for TiO2-NPs decreased after treatment above 500 °C, possibly due to a change in the secondary (aggregate) structure. S-NPs from BSA-stabilized TiO2-NPs exhibited higher global activation energies toward induced volumetric shrinkage than those of CA-stabilized TiO2-NPs, suggesting that activation energy is dependent on ligand size. This prototype study demonstrates the efficacy of using ES-DMA coupled with thermal treatment for characterizing the physical state of NPs, even in a complex medium (e.g., containing plasma proteins) and in the presence of particle agglomerates induced by interaction with binding ligands.

  11. MEASUREMENT OF VOCS DESORBED FROM BUILDING MATERIALS--A HIGH TEMPERATURE DYNAMIC CHAMBER METHOD

    EPA Science Inventory

    Mass balance is a commonly used approach for characterizing the source and sink behavior of building materials. Because the traditional sink test methods evaluate the adsorption and desorption of volatile organic compounds (VOC) at ambient temperatures, the desorption process is...

  12. 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.

  13. Role of microstructure and heat treatments on the desorption kinetics of tritium from austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Chêne, J.; Brass, A.-M.; Trabuc, P.; Gastaldi, O.

    2007-02-01

    The liquid scintillation counting of solid samples (LSC-SS technique) was successfully used to study the role of microstructure and heat treatments on the behavior of residual tritium in several austenitic stainless steels (as-cast remelted tritiated waste, 316LN and 321 steels). The role of desorption annealing in the 100-600 °C range on the residual amount of tritium in tritiated waste was investigated. The residual tritium concentration computed from surface activity measurements is in good agreement with experimental values measured by liquid scintillation counting after full dissolution of the samples. The kinetics of tritium desorption recorded with the LSC-SS technique shows a significant desorption of residual tritium at room temperature, a strong barrier effect of thermal oxide films on the tritium desorption and a dependance of the tritium release on the steels microstructure. Annealing in the 300-600 °C range allows to desorb a large fraction of the residual tritium. However a significant trapping of tritium is evidenced. The influence of trapping phenomena on the concentration of residual tritium and on its dependance with the annealing temperature was investigated with different recrystallized and sensitized microstructures. Trapping is evidenced mainly below 150 °C and concerns a small fraction of the total amount of tritium introduced in austenitic steels. It presumably occurs preferentially on precipitates such as Ti(CN) or on intermetallic phases.

  14. Trapping and desorption of complex organic molecules in water at 20 K

    NASA Astrophysics Data System (ADS)

    Burke, Daren J.; Puletti, Fabrizio; Woods, Paul M.; Viti, Serena; Slater, Ben; Brown, Wendy A.

    2015-10-01

    The formation, chemical, and thermal processing of complex organic molecules (COMs) is currently a topic of much interest in interstellar chemistry. The isomers glycolaldehyde, methyl formate, and acetic acid are particularly important because of their role as pre-biotic species. It is becoming increasingly clear that many COMs are formed within interstellar ices which are dominated by water. Hence, the interaction of these species with water ice is crucially important in dictating their behaviour. Here, we present the first detailed comparative study of the adsorption and thermal processing of glycolaldehyde, methyl formate, and acetic acid adsorbed on and in water ices at astrophysically relevant temperatures (20 K). We show that the functional group of the isomer dictates the strength of interaction with water ice, and hence the resulting desorption and trapping behaviour. Furthermore, the strength of this interaction directly affects the crystallization of water, which in turn affects the desorption behaviour. Our detailed coverage and composition dependent data allow us to categorize the desorption behaviour of the three isomers on the basis of the strength of intermolecular and intramolecular interactions, as well as the natural sublimation temperature of the molecule. This categorization is extended to other C, H, and O containing molecules in order to predict and describe the desorption behaviour of COMs from interstellar ices.

  15. Trapping and desorption of complex organic molecules in water at 20 K.

    PubMed

    Burke, Daren J; Puletti, Fabrizio; Woods, Paul M; Viti, Serena; Slater, Ben; Brown, Wendy A

    2015-10-28

    The formation, chemical, and thermal processing of complex organic molecules (COMs) is currently a topic of much interest in interstellar chemistry. The isomers glycolaldehyde, methyl formate, and acetic acid are particularly important because of their role as pre-biotic species. It is becoming increasingly clear that many COMs are formed within interstellar ices which are dominated by water. Hence, the interaction of these species with water ice is crucially important in dictating their behaviour. Here, we present the first detailed comparative study of the adsorption and thermal processing of glycolaldehyde, methyl formate, and acetic acid adsorbed on and in water ices at astrophysically relevant temperatures (20 K). We show that the functional group of the isomer dictates the strength of interaction with water ice, and hence the resulting desorption and trapping behaviour. Furthermore, the strength of this interaction directly affects the crystallization of water, which in turn affects the desorption behaviour. Our detailed coverage and composition dependent data allow us to categorize the desorption behaviour of the three isomers on the basis of the strength of intermolecular and intramolecular interactions, as well as the natural sublimation temperature of the molecule. This categorization is extended to other C, H, and O containing molecules in order to predict and describe the desorption behaviour of COMs from interstellar ices. PMID:26520540

  16. Adsorption and desorption kinetics of n-octane and n-nonane vapors on activated carbon

    SciTech Connect

    Fletcher, A.J.; Thomas, K.M.

    1999-09-28

    This investigation has involved the study of the adsorption and desorption kinetics of two n-alkanes on a wood-based active carbon (BAX950). The adsorption and desorption characteristics of n-octane vapor on the activated carbon were investigated over the relative pressure (p/p{sup o}) range 0--0.97 for temperatures in the range 288--313 K in a static vapor system. The adsorption characteristics of n-nonane were studied over the relative pressure range 0--0.977 and temperature range 303--323 K. The adsorption and desorption kinetics were studied with different amounts of preadsorbed n-octane for set changes in relative vapor pressure (p/p{sup o}). The desorption kinetics were much slower than the corresponding adsorption kinetics for the same pressure step. The rate constants for adsorption increased with increasing relative pressure and surface coverage. The kinetic data for adsorption were used to calculate the activation energies for each increase in relative pressure. The activation energy was highest at low p/p{sup o} and decreased with increasing p/p{sup o} until a maximum was reached at p/p{sup o}{approximately}0.075. n-Nonane adsorption showed similar trends in adsorption kinetics and activation energies to the n-octane adsorption isotherm and mechanism.

  17. Rate equations for collision-induced desorption and abstraction in the reaction system H(g)+D/Si(100)→D2,HD at 573 K

    NASA Astrophysics Data System (ADS)

    Khanom, F.; Shimokawa, S.; Inanaga, S.; Namiki, A.; Gamo, M.-N.; Ando, T.

    2000-09-01

    Collision-induced desorption (CID) and Eley-Rideal (ER) type abstraction have been investigated in the reaction system, H(g)+Dad/Si(100)→D2,HD, at surface temperature of 573 K where dihydride phase is unstable. Rate equations for CID were obtained based on a second-order kinetics with respect to doubly occupied Si dimers DSi-SiD, DSi-SiH, and HSi-SiH, which are considered as parent species of transiently formed dihydrides, DSiD, DSiH, and HSiH, respectively. The coverages of the doubly occupied dimers were determined as a function of H exposure time by means of temperature-programmed-desorption (TPD), and then the rate equations were calculated. As a result, the experimental D2 and HD rate curves were reasonably fit with the rate equations formulated. This fact indicates that CID is induced when two dihydride species encounter during their propagation via dihydride-monohydride isomerization reactions. It was found that HSi-SiH does not play a role in CID of both D2 and HD. Possible origins of this isotope effect were discussed in terms of quantum effects on associative desorption and diffusion processes. The HD rate curve due to direct ER abstraction channel was fit with a first-order kinetics in Dad coverage for a low coverage regime where dangling bonds exist. However, for a high coverage regime where the surface is saturated, the HD rate curve was fit with DSi-SiD coverages, suggesting that Dad that are paired up with Had in the same Si dimers are not abstracted.

  18. Polarization dependent fragmentation of ions produced by laser desorption from nanopost arrays.

    PubMed

    Stolee, Jessica A; Vertes, Akos

    2011-05-28

    Tailored silicon nanopost arrays (NAPA) enable controlled and resonant ion production in laser desorption ionization experiments and have been termed nanophotonic ion sources (Walker et al., J. Phys. Chem. C, 2010, 114, 4835-4840). As the post dimensions are comparable to or smaller than the laser wavelength, near-field effects and localized electromagnetic fields are present in their vicinity. In this contribution, we explore the desorption and ionization mechanism by studying how surface derivatization affects ion yields and fragmentation. We demonstrate that by increasing the laser fluence on derivatized NAPA with less polar surfaces that have decreased interaction energy between the structured silicon substrate and the adsorbate, the spectrum changes from exhibiting primarily molecular ions to showing a growing variety and abundance of fragments. The polarization angle of the laser beam had been shown to dramatically affect the ion yields of adsorbates. For the first time, we report that by rotating the plane of polarization of the desorption laser, the internal energy of the adsorbate can also be modulated resulting in polarization dependent fragmentation. This polarization effect also resulted in selective fragmentation of vitamin B(12). To explore the internal energy of NAPA generated ions, the effect of the post aspect ratios on the laser desorption thresholds and on the internal energy of a preformed ion was studied. Elevated surface temperatures and enhanced near fields in the vicinity of high aspect ratio posts are thought to contribute to desorption and ionization from NAPA. Comparison of the fluence dependence of the internal energies of ions produced from nanoporous silicon and NAPA substrates indicates that surface restructuring or transient melting by the desorption laser is a prerequisite for the former but not for the latter. PMID:21437297

  19. Polarization dependent fragmentation of ions produced by laser desorption from nanopost arrays.

    PubMed

    Stolee, Jessica A; Vertes, Akos

    2011-05-28

    Tailored silicon nanopost arrays (NAPA) enable controlled and resonant ion production in laser desorption ionization experiments and have been termed nanophotonic ion sources (Walker et al., J. Phys. Chem. C, 2010, 114, 4835-4840). As the post dimensions are comparable to or smaller than the laser wavelength, near-field effects and localized electromagnetic fields are present in their vicinity. In this contribution, we explore the desorption and ionization mechanism by studying how surface derivatization affects ion yields and fragmentation. We demonstrate that by increasing the laser fluence on derivatized NAPA with less polar surfaces that have decreased interaction energy between the structured silicon substrate and the adsorbate, the spectrum changes from exhibiting primarily molecular ions to showing a growing variety and abundance of fragments. The polarization angle of the laser beam had been shown to dramatically affect the ion yields of adsorbates. For the first time, we report that by rotating the plane of polarization of the desorption laser, the internal energy of the adsorbate can also be modulated resulting in polarization dependent fragmentation. This polarization effect also resulted in selective fragmentation of vitamin B(12). To explore the internal energy of NAPA generated ions, the effect of the post aspect ratios on the laser desorption thresholds and on the internal energy of a preformed ion was studied. Elevated surface temperatures and enhanced near fields in the vicinity of high aspect ratio posts are thought to contribute to desorption and ionization from NAPA. Comparison of the fluence dependence of the internal energies of ions produced from nanoporous silicon and NAPA substrates indicates that surface restructuring or transient melting by the desorption laser is a prerequisite for the former but not for the latter.

  20. Sorption and desorption of cobalt by Oscillatoria anguistissima.

    PubMed

    Ahuja, P; Gupta, R; Saxena, R K

    1999-07-01

    Oscillatoria anguistissima rapidly adsorbs appreciable amounts of cobalt from the aqueous solutions within 15 min of initial contact with the metal solution. O. anguistissima showed a high sequestration of cobalt at low equilibrium concentrations, and it followed the Freundlich model of adsorption. The adsorption is a strongly pH-dependent and temperature-independent phenomenon. The presence of Mg2+ and Ca2+ (100-200 ppm) resulted in decline in Co2+ adsorption capacity of Oscillatoria biomass. Sulphate and nitrate (0. 75-10 mM) drastically reduced the extent of Co2+ biosorption. The biosorption of cobalt is an ion-exchange process as the Co2+ binding was accompanied by release of a large amounts of Mg2+ ions. Na2CO3 (1.0 mM) resulted in about 76% desorption of Co2+ from the loaded biomass.

  1. In situ thermal desorption of soils impacted with chlorinated solvents

    SciTech Connect

    Vinegar, H.J.; Stegemeier, G.L.; Carl, F.G.; Stevenson, J.D.; Dudley, R.J.

    1999-07-01

    In situ thermal desorption (ISTD) has been demonstrated to remove high concentrations of chlorinated solvents such as PCE and TCE even from tight clay soils. ISTD applies heat and vacuum simultaneously to subsurface soils using thermal blankets for shallow contaminants (less than 2 ft depth) and thermal wells for deeper contamination. The ISTD process possesses a high removal efficiency because the narrow range of soil thermal conductivities provides excellent sweep efficiency and because its high operating temperature increases soil permeabilities and achieves complete displacement efficiency of contaminants in the gas phase. The first full scale commercial application of the ISTD well technology is described in detail for a site in Portland, Indiana, where silty clay soil was impacted with chlorinated solvents.

  2. Sorption and desorption of cobalt by Oscillatoria anguistissima.

    PubMed

    Ahuja, P; Gupta, R; Saxena, R K

    1999-07-01

    Oscillatoria anguistissima rapidly adsorbs appreciable amounts of cobalt from the aqueous solutions within 15 min of initial contact with the metal solution. O. anguistissima showed a high sequestration of cobalt at low equilibrium concentrations, and it followed the Freundlich model of adsorption. The adsorption is a strongly pH-dependent and temperature-independent phenomenon. The presence of Mg2+ and Ca2+ (100-200 ppm) resulted in decline in Co2+ adsorption capacity of Oscillatoria biomass. Sulphate and nitrate (0. 75-10 mM) drastically reduced the extent of Co2+ biosorption. The biosorption of cobalt is an ion-exchange process as the Co2+ binding was accompanied by release of a large amounts of Mg2+ ions. Na2CO3 (1.0 mM) resulted in about 76% desorption of Co2+ from the loaded biomass. PMID:10387117

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

    SciTech Connect

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

    2010-03-12

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

  4. The Effect of Platinum-coatings on Hydrogen- and Water-absorption and Desorption Characteristics of Lithium Zirconate

    NASA Astrophysics Data System (ADS)

    Tsuchiya, B.; Bandow, S.; Nagata, S.; Saito, K.; Tokunaga, K.; Morita, K.

    Hydrogen (H)- and water (H2O)-storage and desorption characteristics of 25 nm thick Pt films onLi2ZrO3composite materials, exposed to normal air at room temperature, have been investigated by means of elastic recoil detection (ERD), Rutherford backscattering spectrometry (RBS), weight gain measurement (WGM), and thermal desorption spectroscopy (TDS) techniques. It was found by the ERD and TDS that H and H2O were absorbed into the Pt-coated Li2ZrO3 in air at room temperature and desorbed from it in vacuum at much low temperatures of approximately 317 and 309 K, respectively. In addition, the WGM and TDS spectra revealed that the absorption and desorption characters ofsome gases such as CH4, CO, and CO2including H as well as H2Ointo the Li2ZrO3 bulk were improved by Pt deposition.

  5. XPS investigation on vacuum thermal desorption of UV/ozone treated GaAs(100) surfaces

    NASA Astrophysics Data System (ADS)

    Cossu, G.; Ingo, G. M.; Mattogno, G.; Padeletti, G.; Proietti, G. M.

    In order to prepare suitable surfaces for molecular beam epitaxy (MBE), sacrificial thin oxide layers on HCl etched GaAs(100) surfaces were grown by both air and UV/ozone exposure. Passive films were subsequently removed by vacuum thermal desorption to achieve surfaces that were smooth and clean on an atomic scale. The evolution of the surface chemical composition, as a function of vacuum desorption temperature, has been studied by means of X-ray photoelectron spectroscopy (XPS). XPS results have evidenced for air and UV/ozone exposed GaAs(100) surfaces a relationship between desorption temperature and surface chemical composition; indeed, the oxide removal is temperature dependent and sequentially selective as follows: As 2O 3. AsO and Ga 2O 3. Furthermore, XPS results have shown that air-grown films have a chemical composition and thermal desorption behaviour different from UV/ozone treated materials. Indeed, these latter have an As 2O 3/Ga 2O 3 and an unoxidized As/Ga ratio close to unity for as grown and thermal treated at 580°C surfaces, respectively. By contrast, air-exposed GaAs(100) materials are Ga 2O 3-enriched and after vacuum thermal desorption treatments have never a stoichiometric composition(As (GaAs)/Ga (GaAs)= 1). Furthermore UV/ozone treated GaAs(100) surfaces subjected to a vacuum thermal treatment at 580°C, have a troublesome organic contamination level below XPS detectability, whereas from air-exposed surfaces, carbon is not completely thermally removable

  6. Adsorption and desorption of chlorpyrifos to soils and sediments.

    PubMed

    Gebremariam, Seyoum Yami; Beutel, Marc W; Yonge, David R; Flury, Markus; Harsh, James B

    2012-01-01

    Chlorpyrifos, one of the most widely used insecticides, has been detected in air, rain, marine sediments, surface waters, drinking water wells, and solid and liquid dietary samples collected from urban and rural areas. Its metabolite, TCP, has also been widely detected in urinary samples collected from people of various age groups. With a goal of elucidating the factors that control the environmental contamination, impact, persistence, and ecotoxicity of chlorpyrifos, we examine, in this review, the peer-reviewed literature relating to chlorpyrifos adsorption and desorption behavior in various solid-phase matrices. Adsorption tends to reduce chlorpyrifos mobility, but adsorption to erodible particulates, dissolved organic matter, or mobile inorganic colloids enhances its mobility. Adsorption to suspended sediments and particulates constitutes a major off-site migration route for chlorpyrifos to surface waters, wherein it poses a potential danger to aquatic organisms. Adsorption increases the persistence of chlorpyrifos in the environment by reducing its avail- ability to a wide range of dissipative and degradative forces, whereas the effect of adsorption on its ecotoxicity is dependent upon the route of exposure. Chlorpyrifos adsorbs to soils, aquatic sediments, organic matter, and clay minerals to differing degrees. Its adsorption strongly correlates with organic carbon con- tent of the soils and sediments. A comprehensive review of studies that relied on the batch equilibrium technique yields mean and median Kd values for chlorpyrifos of 271 and 116 L/kg for soils, and 385 and 403 L/kg for aquatic sediments. Chlorpyrifos adsorption coefficients spanned two orders of magnitude in soils. Normalizing the partition coefficient to organic content failed to substantially reduce variability to commonly acceptable level of variation. Mean and median values for chlorpyrifos partition coefficients normalized to organic carbon, K, were 8,163 and 7,227 L/kg for soils and 13

  7. Sorption/Desorption Interactions of Plutonium with Montmorillonite

    NASA Astrophysics Data System (ADS)

    Begg, J.; Zavarin, M.; Zhao, P.; Kersting, A. B.

    2012-12-01

    first order process. Furthermore, a pH dependence was observed, with less desorbed at pH 4 compared to pH 8. We suggest the pH dependence is likely controlled by reoxidation of Pu(IV) to Pu(V) and aqueous speciation. We will present models used to describe desorption behavior and discuss the implications for Pu transport. References: Kersting, A.B.; Efurd, D.W.; Finnegan, D.L.; Rokop, D.J.; Smith, D.K.; Thompson J.L. (1999) Migration of plutonium in groundwater at the Nevada Test Site, Nature, 397, 56-59. Novikov A.P.; Kalmykov, S.N.; Utsunomiya, S.; Ewing, R.C.; Horreard, F.; Merkulov, A.; Clark, S.B.; Tkachev, V.V.; Myasoedov, B.F. (2006) Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia, Science, 314, 638-641. Santschi, P.H.; Roberts, K.; Guo, L. (2002) The organic nature of colloidal actinides transported in surface water environments. Environ. Sci. Technol., 36, 3711-3719. This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. LLNL-ABS-570161

  8. 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.

  9. FORTRAN program for calculating coolant flow and metal temperatures of a full-coverage-film-cooled vane or blade

    NASA Technical Reports Server (NTRS)

    Meitner, P. L.

    1978-01-01

    A computer program that calculates the coolant flow and the metal temperatures of a full-coverage-film-cooled vane or blade was developed. The analysis was based on compressible, one-dimensional fluid flow and on one-dimensional heat transfer and treats the vane or blade shell as a porous wall. The calculated temperatures are average values for the shell outer-surface area associated with each film-cooling hole row. A thermal-barrier coating may be specified on the shell outer surface, and centrifugal effects can be included for blade calculations. The program is written in FORTRAN 4 and is operational on a UNIVAC 1100/42 computer. The method of analysis, the program input, the program output, and two sample problems are provided.

  10. High-Temperature Gas-Cooled Reactor Technology Development Program: Annual progress report for period ending December 31, 1987

    SciTech Connect

    Jones, J.E.,Jr.; Kasten, P.R.; Rittenhouse, P.L.; Sanders, J.P.

    1989-03-01

    The High-Temperature Gas-Cooled Reactor (HTGR) Program being carried out under the US Department of Energy (DOE) continues to emphasize the development of modular high-temperature gas-cooled reactors (MHTGRs) possessing a high degree of inherent safety. The emphasis at this time is to develop the preliminary design of the reference MHTGR and to develop the associated technology base and licensing infrastructure in support of future reactor deployment. A longer-term objective is to realize the full high-temperature potential of HTGRs in gas turbine and high-temperature, process-heat applications. This document summarizes the activities of the HTGR Technology Development Program for the period ending December 31, 1987.

  11. 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.

  12. Soil temperature modeling at different depths using neuro-fuzzy, neural network, and genetic programming techniques

    NASA Astrophysics Data System (ADS)

    Kisi, Ozgur; Sanikhani, Hadi; Cobaner, Murat

    2016-05-01

    The applicability of artificial neural networks (ANN), adaptive neuro-fuzzy inference system (ANFIS), and genetic programming (GP) techniques in estimating soil temperatures (ST) at different depths is investigated in this study. Weather data from two stations, Mersin and Adana, Turkey, were used as inputs to the applied models in order to model monthly STs. The first part of the study focused on comparison of ANN, ANFIS, and GP models in modeling ST of two stations at the depths of 10, 50, and 100 cm. GP was found to perform better than the ANN and ANFIS-SC in estimating monthly ST. The effect of periodicity (month of the year) on models' accuracy was also investigated. Including periodicity component in models' inputs considerably increased their accuracies. The root mean square error (RMSE) of ANN models was respectively decreased by 34 and 27 % for the depths of 10 and 100 cm adding the periodicity input. In the second part of the study, the accuracies of the ANN, ANFIS, and GP models were compared in estimating ST of Mersin Station using the climatic data of Adana Station. The ANN models generally performed better than the ANFIS-SC and GP in modeling ST of Mersin Station without local climatic inputs.

  13. 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.

  14. Helium Retention and Desorption Behaviour of Reduced Activation Ferritic/Martenstic Steel

    NASA Astrophysics Data System (ADS)

    Wang, Pinghuai; Nobuta, Yuji; Hino, Tomoaki; Yamauchi, Yuji; Chen, Jiming; Xu, Zengyu; Li, Xiongwei; Liu, Shi

    2009-04-01

    The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwestern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites.

  15. 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, CaCl₂ and NaNO₃) 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 (ω ≈ 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

  16. Double DCO+ Rings Reveal CO Ice Desorption in the Outer Disk Around IM Lup

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.; Furuya, Kenji; Loomis, Ryan; Aikawa, Yuri; Andrews, Sean M.; Qi, Chunhua; van Dishoeck, Ewine F.; Wilner, David J.

    2015-09-01

    In a protoplanetary disk, a combination of thermal and non-thermal desorption processes regulate where volatiles are liberated from icy grain mantles into the gas phase. Non-thermal desorption should result in volatile-enriched gas in disk-regions where complete freeze-out is otherwise expected. We present Atacama Large Millimeter/Submillimeter Array observations of the disk around the young star IM Lup in 1.4 mm continuum, C18O 2-1, H13CO+ 3-2 and DCO+ 3-2 emission at ˜0.″5 resolution. The images of these dust and gas tracers are clearly resolved. The DCO+ line exhibits a striking pair of concentric rings of emission that peak at radii of ˜0.″6 and 2″ (˜90 and 300 AU, respectively). Based on disk chemistry model comparison, the inner DCO+ ring is associated with the balance of CO freeze-out and thermal desorption due to a radial decrease in disk temperature. The outer DCO+ ring is explained by non-thermal desorption of CO ice in the low-column-density outer disk, repopulating the disk midplane with cold CO gas. The CO gas then reacts with abundant H2D+ to form the observed DCO+ outer ring. These observations demonstrate that spatially resolved DCO+ emission can be used to trace otherwise hidden cold gas reservoirs in the outmost disk regions, opening a new window onto their chemistry and kinematics.

  17. Model for the catalytic oxidation of CO, including gas-phase impurities and CO desorption

    NASA Astrophysics Data System (ADS)

    Buendía, G. M.; Rikvold, P. A.

    2013-07-01

    We present results of kinetic Monte Carlo simulations of a modified Ziff-Gulari-Barshad model for the reaction CO+O → CO2 on a catalytic surface. Our model includes impurities in the gas phase, CO desorption, and a modification known to eliminate the unphysical O poisoned phase. The impurities can adsorb and desorb on the surface, but otherwise remain inert. In a previous work that did not include CO desorption [Buendía and Rikvold, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031143 85, 031143 (2012)], we found that the impurities have very distinctive effects on the phase diagram and greatly diminish the reactivity of the system. If the impurities do not desorb, once the system reaches a stationary state, the CO2 production disappears. When the impurities are allowed to desorb, there are regions where the CO2 reaction window reappears, although greatly reduced. Following experimental evidence that indicates that temperature effects are crucial in many catalytic processes, here we further analyze these effects by including a CO desorption rate. We find that the CO desorption has the effect to smooth the transition between the reactive and the CO rich phase, and most importantly it can counteract the negative effects of the presence of impurities by widening the reactive window such that now the system remains catalytically active in the whole range of CO pressures.

  18. Laser Infrared Desorption Spectroscopy to Detect Complex Organic Molecules on Icy Planetary Surfaces

    NASA Technical Reports Server (NTRS)

    Sollit, Luke S.; Beegle, Luther W.

    2008-01-01

    Laser Desorption-Infrared Spectroscopy (LD-IR) uses an IR laser pulse to desorb surface materials while a spectrometer measures the emission spectrum of the desorbed materials (Figure 1). In this example, laser desorption operates by having the incident laser energy absorbed by near surface material (10 microns in depth). This desorption produces a plume that exists in an excited state at elevated temperatures. A natural analog for this phenomenon can be observed when comets approach the sun and become active and individual molecular emission spectra can be observed in the IR [1,2,3,4,5]. When this occurs in comets, the same species that initially emit radiation down to the ground state are free to absorb it, reducing the amount of detectable emission features. The nature of our technique results in absorption not occurring, because the laser pulse could easily be moved away form the initial desorption plume, and still have better spatial resolution then reflectance spectroscopy. In reflectance spectroscopy, trace components have a relatively weak signal when compared to the entire active nature of the surface. With LDIR, the emission spectrum is used to identify and analyze surface materials.

  19. 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, CaCl₂ and NaNO₃) 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 (ω ≈ 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.

  20. 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.

  1. Limiting Behavior in Desorption Induced by Multiple Electronic Transitions (DIMET).

    NASA Astrophysics Data System (ADS)

    Misewich, J. A.; Heinz, T. F.

    1996-03-01

    In recent experiments femtosecond laser light has been used to activate chemical processes at metal surfaces. Such excitation leads to a new regime in which the high electronic tempeature of the substrate drive reactions. Two classes of models have been proposed to explain the coupling of adsorbate motion to the substrate electronic excitations: one based on an electronic friction picture footnote C. Springer, M. Head-Gordon, and J. C. Tully, Surf. Sci. 320, L57 (1994); M. Brandbyge et al., Phys. Rev. B 52, 6042 (1995) and the other on multiple excitation picture (Desorption Induced by Multiple Electronic Transitions - DIMET).footnote J. A. Misewich et al., Phys. Rev. Lett. 68, 3737 (1992) Here we discuss the limiting behavior of the DIMET model at low and high electronic temperatures. At low electronic temperatures, the model approaches the behavior of the familiar single-excitation DIET process. At high electronic temperatures, the DIMET model yields results similar to that expected in an electronic friction picture. In particular, we show that the DIMET model yields an energy distribution in the adsorbate reaction coordinate that is approximately thermal and approaches equilibrium with the substrate electronic excitations.

  2. Oil spills debris clean up by thermal desorption.

    PubMed

    Araruna, J T; Portes, V L O; Soares, A P L; Silva, M G; Sthel, M S; Schramm, D U; Tibana, S; Vargas, H

    2004-07-01

    Oil spills represent a significant environmental issue in Brazil. This paper presents the latest results of a comprehensive experimental programme aimed at understanding how the presence of spilled oil affects the properties of sands and at studying alternatives to remediate the affected shores. Results indicate that oil causes a slight increase in grain size and uniformity, and oiled debris presents a smaller void ratio but a larger unit weight. It was also observed that effective strength parameters for both the natural and oiled debris were the same although the undrained strength of a natural sand is much higher than that of the contaminated sand. At ambient temperature, oiled debris emits methane and ammonia, and these emissions tend to increase with rising temperatures. On the other hand, the oil and grease content from oiled debris decreases with rising temperature and prolonged exposure. Finally, in situ thermal desorption seems to be a promising method for cleaning debris from oil spills. It is simple, fast and avoids all the difficulties associated with digging up the soil for disposal or cleanup.

  3. Recycling cellulases by pH-triggered adsorption-desorption during the enzymatic hydrolysis of lignocellulosic biomass.

    PubMed

    Shang, Yaping; Su, Rongxin; Huang, Renliang; Yang, Yang; Qi, Wei; Li, Qiujin; He, Zhimin

    2014-06-01

    Recycling of cellulases is an effective way to reduce the cost of enzymatic hydrolysis for the production of cellulosic ethanol. In this study, we examined the adsorption and desorption behaviors of cellulase at different pH values and temperatures. Furthermore, we developed a promising way to recover both free and bound cellulases by pH-triggered adsorption-desorption. The results show that acidic pH (e.g., pH 4.8) was found to favor adsorption, whereas alkaline pH (e.g., pH 10) and low temperature (4-37 °C) favored desorption. The adsorption of cellulases reached an equilibrium within 60 min at pH 4.8 and 25 °C, leading to approximately 50 % of the added cellulases bound to the substrate. By controlling the pH of eluent (citrate buffer, 25 °C), we were able to increase the desorption efficiency of bound cellulases from 15 % at pH 4.8 to 85 % at pH 10. To recover cellulases after enzymatic hydrolysis, we employed adsorption by fresh substrate and desorption at pH 10 to recover the free cellulases in supernatant and the bound cellulases in residue, respectively. The recycling performance (based on the glucose yield) of this simple strategy could reach near 80 %. Our results provided a simple, low-cost, and effective approach for cellulase recycling during the enzymatic hydrolysis of lignocellulosic biomass.

  4. Kinetics of low-temperature CO oxidation on Au(111)

    NASA Astrophysics Data System (ADS)

    Thuening, Theodore; Walker, Joshua; Adams, Heather; Furlong, Octavio; Tysoe, Wilfred T.

    2016-06-01

    The oxidation of carbon monoxide on oxygen-modified Au(111) surfaces is studied using a combination of reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). TPD reveals that CO desorbs in two states with the low-temperature state have a peak temperature between ~ 130 and 150 K, and the higher-temperature state having a peak temperature that varies from ~ 175 to ~ 220 K depending on the initial oxygen and CO coverages. Infrared spectroscopy indicates that the low-temperature CO desorption state is predominantly associated with CO adsorbed on Auδ + sites, while the higher-temperature states are due to CO on Au0 sites. No additional vibrational features are detected indicating that CO reacts directly with adsorbed atomic oxygen on gold to form CO2. Estimates of the activation energy for CO2 formation suggest that they are in the same range and found for supported gold catalysts at reaction temperature below ~ 300 K.

  5. Computer program for afterheat temperature distribution for mobile nuclear power plant

    NASA Technical Reports Server (NTRS)

    Parker, W. G.; Vanbibber, L. E.

    1972-01-01

    ESATA computer program was developed to analyze thermal safety aspects of post-impacted mobile nuclear power plants. Program is written in FORTRAN 4 and designed for IBM 7094/7044 direct coupled system.

  6. Coalbed methane adsorption and desorption characteristics related to coal particle size

    NASA Astrophysics Data System (ADS)

    Yan-Yan, Feng; Wen, Yang; Wei, Chu

    2016-06-01

    Effects of particle size on CH4 and CO2 adsorption and desorption characteristics of coals are investigated at 308 K and pressures up to 5.0 MPa. The gas adsorption and desorption isotherms of coals with particle sizes ranging from 250 μm to 840 μm are measured via the volumetric method, and the Langmuir model is used to analyse the experimental results. Coal particle size is found to have an obvious effect on the coal pore structure. With the decrease of coal particle size in the process of grinding, the pore accessibility of the coal, including the specific surface area and pore volume, increases. Hence, coal with smaller particle size has higher specific surface area and higher pore volume. The ability of adsorption was highly related to the pore structure of coal, and coal particle size has a significant influence on coal adsorption/desorption characteristics, including adsorption capacity and desorption hysteresis for CH4 and CO2, i.e., coal with a smaller particle size achieves higher adsorption capacity, while the sample with a larger particle size has lower adsorption capacity. Further, coal with larger particle size is also found to have relatively large desorption hysteresis. In addition, dynamic adsorption performances of the samples are carried out at 298 K and at pressures of 0.1 MPa and 0.5 MPa, respectively, and the results indicate that with the increase of particle size, the difference between CO2 and CH4 adsorption capacities of the samples decreases. Project supported by the National Basic Research Program of China (Grant No. 2011CB201202).

  7. Sorption and desorption of indaziflam degradates in several agricultural soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Processes regulating pesticide fate in the environment are influenced by the physicochemical properties of pesticides and soils. Sorption-desorption are important processes as they regulate movement of pesticides in soil. Although sorption-desorption is widely studied for herbicides, studies involvi...

  8. HTCAP-1: a program for calcuating operating temperatures in HFIR target irradiation experiments

    SciTech Connect

    Kania, M.J.; Howard A.M.

    1980-06-01

    The thermal modeling code, HTCAP-1, calculates in-reactor operating temperatures of fueled specimens contained in the High Flux Isotope Reactor (HFIR) target irradiation experiments (HT-series). Temperature calculations are made for loose particle and bonded fuel rod specimens. Maximum particle surface temperatures are calculated for the loose particles and centerline and surface temperatures for the fuel rods. Three computational models are employed to determine fission heat generation rates, capsule heat transfer analysis, and specimen temperatures. This report is also intended to be a users' manual, and the application of HTCAP-1 to the HT-34 irradiation capsule is presented.

  9. Integrated field emission array for ion desorption

    DOEpatents

    Resnick, Paul J; Hertz, Kristin L; Holland, Christopher; Chichester, David; Schwoebel, Paul

    2013-09-17

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  10. Integrated field emission array for ion desorption

    DOEpatents

    Resnick, Paul J; Hertz, Kristin L.; Holland, Christopher; Chichester, David

    2016-08-23

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  11. Modeling Organic Contaminant Desorption from Municipal Solid Waste Components

    NASA Astrophysics Data System (ADS)

    Knappe, D. R.; Wu, B.; Barlaz, M. A.

    2002-12-01

    Approximately 25% of the sites on the National Priority List (NPL) of Superfund are municipal landfills that accepted hazardous waste. Unlined landfills typically result in groundwater contamination, and priority pollutants such as alkylbenzenes are often present. To select cost-effective risk management alternatives, better information on factors controlling the fate of hydrophobic organic contaminants (HOCs) in landfills is required. The objectives of this study were (1) to investigate the effects of HOC aging time, anaerobic sorbent decomposition, and leachate composition on HOC desorption rates, and (2) to simulate HOC desorption rates from polymers and biopolymer composites with suitable diffusion models. Experiments were conducted with individual components of municipal solid waste (MSW) including polyvinyl chloride (PVC), high-density polyethylene (HDPE), newsprint, office paper, and model food and yard waste (rabbit food). Each of the biopolymer composites (office paper, newsprint, rabbit food) was tested in both fresh and anaerobically decomposed form. To determine the effects of aging on alkylbenzene desorption rates, batch desorption tests were performed after sorbents were exposed to toluene for 30 and 250 days in flame-sealed ampules. Desorption tests showed that alkylbenzene desorption rates varied greatly among MSW components (PVC slowest, fresh rabbit food and newsprint fastest). Furthermore, desorption rates decreased as aging time increased. A single-parameter polymer diffusion model successfully described PVC and HDPE desorption data, but it failed to simulate desorption rate data for biopolymer composites. For biopolymer composites, a three-parameter biphasic polymer diffusion model was employed, which successfully simulated both the initial rapid and the subsequent slow desorption of toluene. Toluene desorption rates from MSW mixtures were predicted for typical MSW compositions in the years 1960 and 1997. For the older MSW mixture, which had a

  12. 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

  13. 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.

  14. 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.

  15. Thermal desorption of petroleum contaminants from soils and sand using a continuous feed lab scale rotary kiln

    SciTech Connect

    Chern, Hsien-Tsung S.; Bozzelli, J.W.

    1996-10-01

    A continuous feed rotary kiln was designed and constructed to study thermal desorption of petroleum hydrocarbon contaminants from soil and/or sand matrices. Desorption studies on sand were run on 1-dodecene, 1-hexadecene, naphthalene, and anthracene. Results show that desorption rates are effected most by temperature. Residence time is second in importance. Temperatures required for complete removal (98%) of the specific organics including multi ring aromatics range from 100-250{degrees}C. A matrix for optimized parameterization with a reasonable number of experiments was set up for studies on petroleum hydrocarbon contaminated soils from sites. Parameters included temperature, residence time, purge flow, kiln angle, rotation and soil feed. Parameters were varied to try and quantitate effects and determine optimum conditions. Temperature, residence time and purge gas velocity in this order were found to be the most important parameters in the desorption process. The effluent from the kiln was sampled and analyzed to determine the mass balance for carbon. Most of the carbon recovery ranged from 45-115%.

  16. 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.

  17. Slow desorption of volatile organic compounds from soil: evidence of desorption step limitations.

    PubMed

    Raihala, T S; Wang, Y; Jackman, A P

    1999-03-19

    Transient adsorption and desorption of 1,2 dichloroethane and toluene on dry Yolo silt loam soil were studied by continuously measuring the composition of the effluent from a soil-packed chromatography column with a mass spectrometer. After obtaining complete breakthrough at approximately 30% relative saturation of one chemical in nitrogen, pure nitrogen feed was initiated and maintained for several hours. Of the material adsorbed at breakthrough, 9.7% of the 1,2 dichloroethane and 14.2% of the toluene were highly resistant to desorption and remained sorbed on the soil even after 5 h of nitrogen flow. When a second chemical with a higher adsorption affinity was introduced into the soil column (water following toluene or toluene following 1,2 dichloroethane), the majority of the first chemical was quickly desorbed and began leaving the soil column before breakthrough of the second chemical. Conversely, when a second chemical with a smaller adsorption affinity was introduced into the soil column, only a small amount of the first chemical was displaced and began leaving the soil column after breakthrough of the second chemical. The results of this study indicate that the desorption step itself may be the rate-limiting step for sorbate which remains after prolonged exposure to sorbate-free gas. PMID:10337401

  18. Conceptual design for a full-scale VAC*TRAX vacuum thermal desorption unit. Final report, September 1992--December 1995

    SciTech Connect

    Palmer, C.R.

    1996-04-01

    Rust Federal Services is pleased to present this topical report on the results of our Phase II conceptual design work of the PRDA VAC*TRAX{sup SM} mobile vacuum thermal desorption technology demonstration program. Through the present Phase II conceptual design activities, Rust has developed an equipment design and permitting strategy that retains the flexibility of a mobile treatment system with the long term value and ease of access of a central facility. The process is designed to remove volatile matter from solid matrices by thermal desorption. The system is also designed with superior emission controls, making it an ideal system for the treatment of radioactive wastes.

  19. Thermal desorption-gas chromatography for the determination of benzene, aniline, nitrobenzene and chlorobenzene in workplace air.

    PubMed

    Patil, S F; Lonkar, S T

    1992-05-29

    Sampling on Tenax TA of different mesh sizes followed by thermal desorption and gas chromatography was evaluated as a simple method for the determination of benzene, aniline, nitrobenzene and chlorobenzene in the workplace air. An alternative sampling technique in place of pump sampling was developed. Quantitative recoveries were obtained in the mass range 0.04-10 micrograms. It was found that air humidity had no effect on recovery. The charged tubes can be stored at room temperature for 5 days with no change in recovery. The particle size of Tenax TA has no significant effect on adsorption and desorption.

  20. 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

  1. 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.

  2. Technical Note: In-situ derivatization thermal desorption GC-TOFMS for direct analysis of particle-bound non-polar and polar organic species

    NASA Astrophysics Data System (ADS)

    Orasche, J.; Schnelle-Kreis, J.; Abbaszade, G.; Zimmermann, R.

    2011-05-01

    An in-situ derivatization thermal desorption method followed by gas chromatography and time-of-flight mass spectrometry (IDTD-GC-TOFMS) was developed for determination of polar organic compounds. Hydroxyl and carboxyl groups of compounds such as anhydrous sugars, alcohols and phenols, fatty acids and resin acids are targets of the derivatization procedure. Derivatization is based on silylation with N-Methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA) during the step of thermal desorption. The high temperature of 300 °C during desorption is utilized for the in-situ derivatization on the collection substrate (quartz fibre filters) accelerating the reaction rate. Thereby, the analysis time is as short as without derivatization. At first the filter surface is dampened with derivatization reagent before insertion of the sample into the thermal desorption unit. To ensure ongoing derivatization during thermal desorption the carrier gas is saturated with MSTFA until the desorption procedure is finished. The method introduced here was compared with direct thermal desorption gas chromatography time-of-flight-mass spectrometry (DTD-GC-TOFMS) and with solvent extraction (SE) procedures followed by gas chromatography and mass spectrometry. Comparisons were carried out with field samples originating from ambient aerosol collected on quartz fibre filters. Moreover, the methods have been applied on NIST Standard Reference Material Urban Dust (SRM 1649a).

  3. 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.

  4. 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

  5. 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

  6. 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.

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

    PubMed

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

    2014-10-13

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  9. High-speed thermo-microscope for imaging thermal desorption phenomena.

    PubMed

    Staymates, Matthew; Gillen, Greg

    2012-07-01

    In this work, we describe a thermo-microscope imaging system that can be used to visualize atmospheric pressure thermal desorption phenomena at high heating rates and frame rates. This versatile and portable instrument is useful for studying events during rapid heating of organic particles on the microscopic scale. The system consists of a zoom lens coupled to a high-speed video camera that is focused on the surface of an aluminum nitride heating element. We leverage high-speed videography with oblique incidence microscopy along with forward and back-scattered illumination to capture vivid images of thermal desorption events during rapid heating of chemical compounds. In a typical experiment, particles of the material of interest are rapidly heated beyond their boiling point while the camera captures images at several thousand frames/s. A data acquisition system, along with an embedded thermocouple and infrared pyrometer are used to measure the temperature of the heater surface. We demonstrate that, while a typical thermocouple lacks the response time to accurately measure temperature ramps that approach 150 °C/s, it is possible to calibrate the system by using a combination of infrared pyrometry, melting point standards, and a thermocouple. Several examples of high explosives undergoing rapid thermal desorption are also presented. PMID:22852730

  10. Modeling of adsorption and ultrasonic desorption of cadmium(II) and zinc(II) on local bentonite.

    PubMed

    Lacin, Oral; Bayrak, Bahar; Korkut, Ozlem; Sayan, Enes

    2005-12-15

    The adsorption and ultrasonic desorption of toxic heavy metal cations (i.e., Cd(II) and Zn(II)) on natural bentonite have been modeled with the aid of a factorial design approach. The ability of untreated bentonite to remove Cd(II) and Zn(II) from aqueous and acidic solutions at different pH values has been studied for different metal concentrations by varying the amount of adsorbent, temperature, stirring speed, and contact time. The same factors, except stirring speed and metal concentration, were applied in desorption study. Ultrasound power was used for desorption instead of stirring speed. A flame atomic absorption spectrometer was used to measure the cadmium and zinc concentration before and after both experimental study. The highest adsorption for Zn and Cd was 99.85 and 96.84%, respectively, and the highest desorption for Zn and Cd obtained was 66.57 and 51.37%, respectively. It is believed that the models obtained for adsorption and desorption may provide a background for detailed mechanism searches and pilot and industrial scale applications. PMID:16051257

  11. Some examples of applications of a microthermal desorption device in the forensic laboratory.

    PubMed

    Andrasko, Jan

    2009-09-01

    Several applications of a microthermal desorption device for analysis of small forensic samples are presented. The method uses a solid phase microextraction holder with the fiber removed. In addition to samples of inks on paper, this device was successfully used for analysis of toners, various stains on bank notes, and lipstick stains on paper. Other small items encountered in a forensic science laboratory were also analyzed: particles of smokeless powder, particles of coffee, and automotive clear topcoat layer. The desorbed compounds were analyzed by gas chromatography with a flame ionization detector or by gas chromatography-mass spectrometry. This device can be used in connection with any kind of gas chromatograph. By selection of different injector temperatures, fractionated thermal desorption of samples is achieved. The procedure was demonstrated on samples of ballpoint pen ink of various age. PMID:19686398

  12. Adsorption and desorption of NO and CO on a Pt(111)Ge surface alloy

    NASA Astrophysics Data System (ADS)

    Fukutani, K.; Magkoev, T. T.; Murata, Y.; Terakura, K.

    1996-08-01

    Adsorption of NO and CO on Pt(111) alloyed with a few per cent of Ge is investigated by reflection—absorption infrared spectroscopy and thermal desorption spectroscopy. Both molecules exclusively occupy the on-top site in contrast to bridge and on-top adsorption on clean Pt(111). The adsorption energy of NO is dramatically reduced compared with that on clean Pt(111). Photodesorption of CO observed on the clean Pt(111) is noticeably suppressed on the Pt(111)Ge surface alloy, while NO desorption is induced by photon irradiation. The rotational and translational temperatures of photodesorbed No are similar to those on clean Pt(111). The change in chemical properties of Pt(111) for molecular adsorption is discussed in terms of d-band filling of the substrate.

  13. 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.

  14. [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

  15. [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.

  16. Laboratory experiments on interstellar ice analogs: The sticking and desorption of small physisorbed molecules

    NASA Technical Reports Server (NTRS)

    Fuchs, G. W.; Acharyya, K.; Bisschop, S. E.; Oberg, K. I.; vanBroekhuizen, F. A.; Fraser, H. J.; Schlemmer, S.; vanDishoeck, E. F.; Linnartz, H.

    2006-01-01

    Molecular oxygen and nitrogen are difficult to observe since they are infrared inactive and radio quiet. The low O2 abundances found so far combined with general considerations of dense cloud conditions suggest molecular oxygen is frozen out at low temperatures (< 20 K) in the shielded inner regions of cloud cores. In solid form O2 and N2 can only be observed as adjuncts within other ice constituents, like CO. In this work we focus on fundamental properties of N2 and O2 in CO ice-gas systems, e.g. desorption characteristics and sticking probabilities at low temperatures for different ice morphologies.

  17. 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.

  18. 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. Howell, M.; Kang, W. P.; Davidson, J. L.; Brooks, M. M.; Tolk, N.

    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.

  19. The effect of selective desorption mechanisms during interstellar ice formation

    NASA Astrophysics Data System (ADS)

    Kalvāns, 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.

  20. 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.

  1. Innovative site remediation technology: Thermal desorption. Volume 6

    SciTech Connect

    Anderson, W.C.

    1993-11-01

    The monograph on thermal desorption is one of a series of eight on innovative site and waste remediation technologies that are the culmination of a multiorganization effort involving more than 100 experts over a two-year period. The thermal desorption processes addressed in this monograph use heat, either direct or indirect, ex situ, as the principal means to physically separate and transfer contaminants from soils, sediments, sludges, filter cakes, or other media. Thermal desorption is part of a treatment train; some pre- and postprocessing is necessary.

  2. Gravimetric analysis of the adsorption and desorption of CO2 on amine-functionalized mesoporous silica mounted on a microcantilever array.

    PubMed

    Lee, Dongkyu; Jin, Yusung; Jung, Namchul; Lee, Jaehyuk; Lee, Jinwoo; Jeong, Yong Shik; Jeon, Sangmin

    2011-07-01

    The kinetics of CO(2) adsorption and desorption over amine-functionalized mesoporous silica were investigated using silicon microcantilever arrays. Three types of mesoporous silica with different pore sizes were synthesized and functionalized with a variety of amine molecules. After depositing the silica sorbents onto the free end of each cantilever in an array, mass changes due to the adsorption and desorption of CO(2) were determined in situ with picogram sensitivity by measuring variations in the cantilever frequencies. The adsorption and desorption kinetics were found to be diffusion-controlled, and the kinetics were accelerated by increasing the temperature and pore size. The activation energies for adsorption and desorption of CO(2) were determined from Arrhenius plots.

  3. Trace level detection of explosives in solution using leidenfrost phenomenon assisted thermal desorption ambient mass spectrometry.

    PubMed

    Saha, Subhrakanti; Mandal, Mridul Kanti; Chen, Lee Chuin; Ninomiya, Satoshi; Shida, Yasuo; Hiraoka, Kenzo

    2013-01-01

    The present paper demonstrates the detection of explosives in solution using thermal desorption technique at a temperature higher than Leidenfrost temperature of the solvent in combination with low temperature plasma (LTP) ionization. Leidenfrost temperature of a solvent is the temperature above which the solvent droplet starts levitation instead of splashing when placed on a hot metallic surface. During this desorption process, slow and gentle solvent evaporation takes place, which leads to the pre-concentration of less-volatile explosive molecules in the droplet and the explosive molecules are released at the last moment of droplet evaporation. The limits of detection for explosives studied by using this thermal desorption LTP ionization method varied in a range of 1 to 10 parts per billion (ppb) using a droplet volume of 20 μL (absolute sample amount 90-630 fmol). As LTP ionization method was applied and ion-molecule reactions took place in ambient atmosphere, various ion-molecule adduct species like [M+NO2](-), [M+NO3](-), [M+HCO3](-), [M+HCO4](-) were generated together with [M-H](-) peak. Each peak was unambiguously identified using 'Exactive Orbitrap' mass spectrometer in negative ionization mode within 3 ppm deviation compared to its exact mass. This newly developed technique was successfully applied to detect four explosives contained in the pond water and soil sample with minor sample pre-treatment and the explosives were detected with ppb levels. The present method is simple, rapid and can detect trace levels of explosives with high specificity from solutions. PMID:24349927

  4. Trace Level Detection of Explosives in Solution Using Leidenfrost Phenomenon Assisted Thermal Desorption Ambient Mass Spectrometry

    PubMed Central

    Saha, Subhrakanti; Mandal, Mridul Kanti; Chen, Lee Chuin; Ninomiya, Satoshi; Shida, Yasuo; Hiraoka, Kenzo

    2013-01-01

    The present paper demonstrates the detection of explosives in solution using thermal desorption technique at a temperature higher than Leidenfrost temperature of the solvent in combination with low temperature plasma (LTP) ionization. Leidenfrost temperature of a solvent is the temperature above which the solvent droplet starts levitation instead of splashing when placed on a hot metallic surface. During this desorption process, slow and gentle solvent evaporation takes place, which leads to the pre-concentration of less-volatile explosive molecules in the droplet and the explosive molecules are released at the last moment of droplet evaporation. The limits of detection for explosives studied by using this thermal desorption LTP ionization method varied in a range of 1 to 10 parts per billion (ppb) using a droplet volume of 20 μL (absolute sample amount 90–630 fmol). As LTP ionization method was applied and ion–molecule reactions took place in ambient atmosphere, various ion–molecule adduct species like [M+NO2]−, [M+NO3]−, [M+HCO3]−, [M+HCO4]− were generated together with [M−H]− peak. Each peak was unambiguously identified using ‘Exactive Orbitrap’ mass spectrometer in negative ionization mode within 3 ppm deviation compared to its exact mass. This newly developed technique was successfully applied to detect four explosives contained in the pond water and soil sample with minor sample pre-treatment and the explosives were detected with ppb levels. The present method is simple, rapid and can detect trace levels of explosives with high specificity from solutions. PMID:24349927

  5. Salt Tolerance of Desorption Electrospray Ionization (DESI)

    SciTech Connect

    Jackson, Ayanna U.; Talaty, Nari; Cooks, R G; Van Berkel, Gary J

    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.

  6. Microchannel membrane separation applied to confined thin film desorption

    SciTech Connect

    Thorud, Jonathan D.; Liburdy, James A.; Pence, Deborah V.

    2006-08-15

    The concept of a confined thin film to enhance the desorption process is based on a reduced mass diffusion resistance. A wide thin film is formed into a microchannel by using a porous membrane as one wall of the channel enabling vapor extraction along the flow. Heat added to the channel results in vapor generation and subsequent extraction through the membrane. This experimental study investigates the performance of vapor extraction as a function of confined thin film thickness, pressure difference across the membrane and inlet concentration to the microchannel. In addition, heat added to the system was varied and results are presented in terms of the wall superheat temperature relative to the inlet saturated conditions of the binary fluid. The test section was equipped with a transparent window to observe bubble formation and vapor extraction. Results show that the performance, measured by the vapor release rate, increases for reduced channel thickness, for increased pressure difference across the membrane, and for lower inlet concentration. Results show that lower wall superheat correspond to higher heat transfer coefficients. Trends of Nusselt number and Sherwood number versus both channel Reynolds number and the product of the Reynolds number and Schmidt number are presented. Bubble formation in the channel does not degrade overall performance provided a critical heat flux condition does not occur. (author)

  7. 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.

  8. Mercury speciation during in situ thermal desorption in soil.

    PubMed

    Park, Chang Min; Katz, Lynn E; Liljestrand, Howard M

    2015-12-30

    Metallic mercury (Hg(0)) and its compounds are highly mobile and toxic environmental pollutants at trace level. In situ thermal desorption (ISTD) is one of the soil remediation processes applying heat and vacuum simultaneously. Knowledge of thermodynamic mercury speciation is imperative to understand the fate and transport of mercury during thermal remediation and operate the treatment processes in a cost-effective manner. Hence, speciation model for inorganic mercury was developed over a range of environmental conditions to identify distribution of dissolved mercury species and potential transformations of mercury at near source environment. Simulation of phase transitions for metallic mercury, mercury(II) chloride and mercury sulfide with temperature increase showed that complete vaporization of metallic mercury and mercury(II) chloride were achieved below the boiling point of water. The effect of soil compositions on mercury removal was also evaluated to better understand thermal remediation process. Higher vapor pressures expected both from soil pore water and inorganic carbonate minerals in soil as well as creation of permeability were significant for complete vaporization and removal of mercury. PMID:26275352

  9. Peak capacity, peak-capacity production rate, and boiling point resolution for temperature-programmed GC with very high programming rates

    PubMed

    Grall; Leonard; Sacks

    2000-02-01

    Recent advances in column heating technology have made possible very fast linear temperature programming for high-speed gas chromatography. A fused-silica capillary column is contained in a tubular metal jacket, which is resistively heated by a precision power supply. With very rapid column heating, the rate of peak-capacity production is significantly enhanced, but the total peak capacity and the boiling-point resolution (minimum boiling-point difference required for the separation of two nonpolar compounds on a nonpolar column) are reduced relative to more conventional heating rates used with convection-oven instruments. As temperature-programming rates increase, elution temperatures also increase with the result that retention may become insignificant prior to elution. This results in inefficient utilization of the down-stream end of the column and causes a loss in the rate of peak-capacity production. The rate of peak-capacity production is increased by the use of shorter columns and higher carrier gas velocities. With high programming rates (100-600 degrees C/min), column lengths of 6-12 m and average linear carrier gas velocities in the 100-150 cm/s range are satisfactory. In this study, the rate of peak-capacity production, the total peak capacity, and the boiling point resolution are determined for C10-C28 n-alkanes using 6-18 m long columns, 50-200 cm/s average carrier gas velocities, and 60-600 degrees C/min programming rates. It was found that with a 6-meter-long, 0.25-mm i.d. column programmed at a rate of 600 degrees C/min, a maximum peak-capacity production rate of 6.1 peaks/s was obtained. A total peak capacity of about 75 peaks was produced in a 37-s long separation spanning a boiling-point range from n-C10 (174 degrees C) to n-C28 (432 degrees C).

  10. Desorption kinetics of benzene in a sandy soil in the presence of powdered activated carbon.

    PubMed

    Choi, J-W; Kim, S-B; Kim, D-J

    2007-02-01

    Desorption kinetics of benzene was investigated with a modified biphasic desorption model in a sandy soil with five different powdered activated carbon (PAC) contents (0, 1, 2, 5, 10% w/w) as sorbents. Sorption experiments followed by series dilution desorption were conducted for each sorbent. Desorption of benzene was successively performed at two stages using deionized water and hexane. Modeling was performed on both desorption isotherm and desorption rate for water-induced desorption to elucidate the presence of sorption-desorption hysteresis and biphasic desorption and if present to quantify the desorption-resistant fraction (q (irr)) and labile fraction (F) of desorption site responsible for rapid process. Desorption isotherms revealed that sorption-desorption exhibited a severe hysteresis with a significant fraction of benzene being irreversibly adsorbed onto both pure sand and PAC, and that desorption-resistant fraction (q (irr)) increased with PAC content. Desorption kinetic modeling showed that desorption of benzene was biphasic with much higher (4-40 times) rate constant for rapid process (k (1)) than that for slow process (k (2)), and that the difference in the rate constant increased with PAC content. The labile fraction (F) of desorption site showed a decreasing tendency with PAC. The experimental results would provide valuable information on remediation methods for soils and groundwater contaminated with BTEX.

  11. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1992

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that 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 the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. 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 that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  12. 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).

  13. Comparative sorption, desorption and leaching potential of aminocyclopyrachlor and picloram

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aminocyclopyrachlor and picloram sorption, desorption and leaching potential were investigated in three soils from Minnesota and Hawaii. Aminocyclopyrachlor and picloram sorption fit the Freundlich equation and was independent of concentration for aminocyclopyrachlor (1/n = 1), but not for picloram ...

  14. Laser desorption mass spectrometry for biomolecule detection and its applications

    NASA Astrophysics Data System (ADS)

    Winston Chen, C. H.; Sammartano, L. J.; Isola, N. R.; Allman, S. L.

    2001-08-01

    During the past few years, we developed and used laser desorption mass spectrometry for biomolecule detections. Matrix-assisted laser desorption/ionization (MALDI) was successfully used to detect DNA fragments with the size larger than 3000 base pairs. It was also successfully used to sequence DNA with both enzymatic and chemical degradation methods to produce DNA ladders. We also developed MALDI with fragmentation for direct DNA sequencing for short DNA probes. Since laser desorption mass spectrometry for DNA detection has the advantages of fast speed and no need of labeling, it has a great potential for molecular diagnosis for disease and person identification by DNA fingerprinting. We applied laser desorption mass spectrometry to succeed in the diagnosis of cystic fibrosis and several other nerve degenerative diseases such as Huntington's disease. We also succeeded in demonstrating DNA typing for forensic applications.

  15. Molecular beam-thermal hydrogen desorption from palladium

    SciTech Connect

    Lobo, R. F. M.; Berardo, F. M. V.; Ribeiro, J. H. F.

    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.

  16. 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.

  17. 13th TOPICAL CONFERENCE ON HIGH TEMPERATURE PLASMA DIAGNOSTICS SCIENTIFIC PROGRAM

    SciTech Connect

    C. BARNES

    2000-07-01

    Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. {omega}{sub pe} >> {Omega}{sub ce} in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition ({tau} > 2). Electron Bernstein waves (EBWs) are electrostatic waves which can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as a result of their large K{sub i}. This talk reports on measurements of EBW emission on the CDX-U spherical torus, where B{sub 0} {approx} 2 kG, {approx} 10{sup 13} cm{sup -3} and T{sub e} {approx} 10 - 200 eV. Results will be presented for both direct detection of EBWs and for mode-converted EBW emission. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be {le} T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe was employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Changes in the mode conversion efficiency may explain the observation of mode-converted EBW radiation temperatures below T{sub e}. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where {omega}{sub pe} >> {Omega}{sub ce}.

  18. Modeling arsenic desorption from herbicide-contaminated soils.

    PubMed

    Qi, Yongqiang; Donahoe, Rona J

    2009-06-01

    The application of arsenical herbicides has created legacy environmental problems by contaminating soil in some agricultural areas and at various industrial sites. Numerous previous studies have suggested that the adsorption of arsenic by common soil components is largely controlled by kinetic factors. Four arsenic-contaminated soil samples collected from industrial sites were characterized and subjected to sequential leaching using a synthetic acid rain solution in order to study the release of arsenic. A dual-site numerical sorption-desorption model was constructed that describes arsenic desorption from these soils in terms of two different release mechanisms: Release from type I (equilibrium) and type II (kinetic) sorption sites. Arsenic held on both type I and II sorption sites is accessible through extensive acid rain leaching. Arsenic desorption from these sites follows a linear Kd model; the manner of approaching the Kd model, however, differs. Arsenic desorption from type I sites reached equilibrium with the aqueous phase under the physical environment provided by the experiment (shaking for 24 h at 25 degrees C), while desorption from type II sites followed a first-order kinetic pattern when approaching equilibrium. During synthetic acid rain sequential leaching of the soils, type I sites released their sorbed arsenic rapidly and subsequent desorption was dominated by the kinetic release of arsenic from type II sites. This shift in desorption mechanism dominance generated data corresponding to two intersecting straight lines in the n-logC dimension for all four soils. The dual-site desorption model was solved analytically and proven to be successful in simulating sorption processes where two different mechanisms are simultaneously controlling the aqueous concentration of a trace element.

  19. Adsorption and desorption of nickel(II) ions from aqueous solution by a lignocellulose/montmorillonite nanocomposite.

    PubMed

    Zhang, Xiaotao; Wang, Ximing

    2015-01-01

    A new and inexpensive lignocellulose/montmorillonite (LNC/MMT) nanocomposite was prepared by a chemical intercalation of LNC into MMT and was subsequently investigated as an adsorbent in batch systems for the adsorption-desorption of Ni(II) ions in an aqueous solution. The optimum conditions for the Ni(II) ion adsorption capacity of the LNC/MMT nanocomposite were studied in detail by varying parameters such as the initial Ni(II) concentration, the solution pH value, the adsorption temperature and time. The results indicated that the maximum adsorption capacity of Ni(II) reached 94.86 mg/g at an initial Ni(II) concentration of 0.0032 mol/L, a solution pH of 6.8, an adsorption temperature of 70°C, and adsorption time of 40 min. The represented adsorption kinetics model exhibited good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir isotherm equation best fit the experimental data. The structure of the LNC/MMT nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas the adsorption mechanism was discussed in combination with the results obtained from scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy analyses (FTIR). The desorption capacity of the LNC/MMT nanocomposite depended on parameters such as HNO3 concentration, desorption temperature, and desorption time. The satisfactory desorption capacity of 81.34 mg/g was obtained at a HNO3 concentration, desorption temperature, and desorption time of 0.2 mol/L, 60 ºC, and 30 min, respectively. The regeneration studies showed that the adsorption capacity of the LNC/MMT nanocomposite was consistent for five cycles without any appreciable loss in the batch process and confirmed that the LNC/MMT nanocomposite was reusable. The overall study revealed that the LNC/MMT nanocomposite functioned as an effective adsorbent in the detoxification of Ni

  20. Adsorption and Desorption of Nickel(II) Ions from Aqueous Solution by a Lignocellulose/Montmorillonite Nanocomposite

    PubMed Central

    Zhang, Xiaotao; Wang, Ximing

    2015-01-01

    A new and inexpensive lignocellulose/montmorillonite (LNC/MMT) nanocomposite was prepared by a chemical intercalation of LNC into MMT and was subsequently investigated as an adsorbent in batch systems for the adsorption-desorption of Ni(II) ions in an aqueous solution. The optimum conditions for the Ni(II) ion adsorption capacity of the LNC/MMT nanocomposite were studied in detail by varying parameters such as the initial Ni(II) concentration, the solution pH value, the adsorption temperature and time. The results indicated that the maximum adsorption capacity of Ni(II) reached 94.86 mg/g at an initial Ni(II) concentration of 0.0032 mol/L, a solution pH of 6.8, an adsorption temperature of 70°C, and adsorption time of 40 min. The represented adsorption kinetics model exhibited good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir isotherm equation best fit the experimental data. The structure of the LNC/MMT nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas the adsorption mechanism was discussed in combination with the results obtained from scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy analyses (FTIR). The desorption capacity of the LNC/MMT nanocomposite depended on parameters such as HNO3 concentration, desorption temperature, and desorption time. The satisfactory desorption capacity of 81.34 mg/g was obtained at a HNO3 concentration, desorption temperature, and desorption time of 0.2 mol/L, 60 ºC, and 30 min, respectively. The regeneration studies showed that the adsorption capacity of the LNC/MMT nanocomposite was consistent for five cycles without any appreciable loss in the batch process and confirmed that the LNC/MMT nanocomposite was reusable. The overall study revealed that the LNC/MMT nanocomposite functioned as an effective adsorbent in the detoxification of Ni

  1. Trapping and desorption of energetic Cu atoms on Cu(111) and (001) surfaces at grazing incidence

    SciTech Connect

    Hanson, D.E.; Kress, J.D.; Voter, A.F.; Liu, X.

    1999-10-01

    Molecular-dynamics (MD) simulations of Cu atoms impacting both Cu(111) and (001) surfaces at grazing incidence have been performed to study trapping (or surface skipping), desorption, and energy dissipation. An energetic Cu atom (10{le}E{le}100thinspeV) can become trapped by the mean attractive potential above the surface, oscillating normal to the surface. While in this trapped state, it can traverse hundreds of {Angstrom} as it dissipates energy to the surface. Until the atom either desorbs or comes to rest, it experiences an energy loss, that is piecewise linear in time, typically comprised of two or more linear regions. In each region, the energy loss rate, dE/dt, is approximately constant. The process can be characterized by two parameters: the desorption probability at each oscillation and an average energy loss rate (per oscillation) that is independent of energy. These parameter values are the same for both the (111) and (001) surfaces. A phenomenological model based on these parameters is presented, and the predictions of sticking probability, average energy transfer to the surface, and total distance traveled, agree with full MD simulations. The dependence of the desorption probability on the surface temperature was also studied. {copyright} {ital 1999} {ital The American Physical Society}

  2. Adsorption and desorption of dissolved organic matter by carbon nanotubes: Effects of solution chemistry.

    PubMed

    Engel, Maya; Chefetz, Benny

    2016-06-01

    Increasing use of carbon nanotubes (CNTs) has led to their introduction into the environment where they can interact with dissolved organic matter (DOM). This study focuses on solution chemistry effects on DOM adsorption/desorption processes by single-walled CNTs (SWCNTs). Our data show that DOM adsorption is controlled by the attachment of DOM molecules to the SWCNTs, and that the initial adsorption rate is dependent on solution parameters. Adsorbed amount of DOM at high ionic strength was limited, possibly due to alterations in SWCNT bundling. Desorption of DOM performed at low pH resulted in additional DOM adsorption, whereas at high pH, adsorbed DOM amount decreased. The extent of desorption conducted at increased ionic strength was dependent on pre-adsorbed DOM concentration: low DOM loading stimulated additional adsorption of DOM, whereas high DOM loading facilitated release of adsorbed DOM. Elevated ionic strength and increased adsorbed amount of DOM reduced the oxidation temperature of the SWCNTs, suggesting that changes in the assembly of the SWCNTs had occurred. Moreover, DOM-coated SWCNTs at increased ionic strength provided fewer sites for atrazine adsorption. This study enhances our understanding of DOM-SWCNT interactions in aqueous systems influenced by rapid changes in salinity, and facilitates potential use of SWCNTs in water-purification technologies.

  3. 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.

  4. Energy audit of three energy-conserving devices in a steel industry demonstration program. Task III. GTE high temperature recuperation

    SciTech Connect

    Holden, F.C.; Hoffman, A.O.; Lownie, H.W.

    1983-06-01

    The Office of Industrial Programs of the Department of Energy has undertaken a program to demonstrate to industry the benefits of installing various energy-conserving devices and equipment. This report presents results on one of those systems, a high-temperature ceramic recuperator designed and manufactured by Sylvania Chemical and Metallurgical Division, GTE Products Corporation of Towanda, Pennsylvania. The ceramic cross-flow recuperator unit recovers waste heat from the hot combustion gases and delivers preheated air to high-temperature burners of various manufacture. Of the 38 host site installations included in the program, sufficient operating data were obtained from 28 sites to evaluate the benefits in terms of energy and economic savings that can be achieved. Performance and cost data are analyzed and presented for those 28 installations, which covered a variety of applications, sizes, and industry types. Except for 5 sites where unusual operating or data-collection problems were encountered, the improvements in performance of the recuperated furnaces equalled or exceeded estimates; the average of the total fuel savings for these 23 sites was 44.0 percent, some portion of which resulted from furnace improvements other than recuperation. Payback times were calculated for both total costs and for recuperator-related costs, using a cumulative annual after-tax cash flow method which includes tax investment credits, estimates of general and fuel-price inflation, and maintenance costs.

  5. Uranium and Neptunium Desorption from Yucca Mountain Alluvium

    SciTech Connect

    C.D. Scism; P.W. Reimus; M. Ding; S.J. Chipera

    2006-03-16

    Uranium and neptunium were used as reactive tracers in long-term laboratory desorption studies using saturated alluvium collected from south of Yucca Mountain, Nevada. The objective of these long-term experiments is to make detailed observations of the desorption behavior of uranium and neptunium to provide Yucca Mountain with technical bases for a more realistic and potentially less conservative approach to predicting the transport of adsorbing radionuclides in the saturated alluvium. This paper describes several long-term desorption experiments using a flow-through experimental method and groundwater and alluvium obtained from boreholes along a potential groundwater flow path from the proposed repository site. In the long term desorption experiments, the percentages of uranium and neptunium sorbed as a function of time after different durations of sorption was determined. In addition, the desorbed activity as a function of time was fit using a multi-site, multi-rate model to demonstrate that different desorption rate constants ranging over several orders of magnitude exist for the desorption of uranium from Yucca Mountain saturated alluvium. This information will be used to support the development of a conceptual model that ultimately results in effective K{sub d} values much larger than those currently in use for predicting radionuclide transport at Yucca Mountain.

  6. 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 μg 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.

  7. Measurement of volatile plant compounds in field ambient air by thermal desorption-gas chromatography-mass spectrometry.

    PubMed

    Cai, Xiao-Ming; Xu, Xiu-Xiu; Bian, Lei; Luo, Zong-Xiu; Chen, Zong-Mao

    2015-12-01

    Determination of volatile plant compounds in field ambient air is important to understand chemical communication between plants and insects and will aid the development of semiochemicals from plants for pest control. In this study, a thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method was developed to measure ultra-trace levels of volatile plant compounds in field ambient air. The desorption parameters of TD, including sorbent tube material, tube desorption temperature, desorption time, and cold trap temperature, were selected and optimized. In GC-MS analysis, the selected ion monitoring mode was used for enhanced sensitivity and selectivity. This method was sufficiently sensitive to detect part-per-trillion levels of volatile plant compounds in field ambient air. Laboratory and field evaluation revealed that the method presented high precision and accuracy. Field studies indicated that the background odor of tea plantations contained some common volatile plant compounds, such as (Z)-3-hexenol, methyl salicylate, and (E)-ocimene, at concentrations ranging from 1 to 3400 ng m(-3). In addition, the background odor in summer was more abundant in quality and quantity than in autumn. Relative to previous methods, the TD-GC-MS method is more sensitive, permitting accurate qualitative and quantitative measurements of volatile plant compounds in field ambient air. PMID:26493981

  8. Measurement of volatile plant compounds in field ambient air by thermal desorption-gas chromatography-mass spectrometry.

    PubMed

    Cai, Xiao-Ming; Xu, Xiu-Xiu; Bian, Lei; Luo, Zong-Xiu; Chen, Zong-Mao

    2015-12-01

    Determination of volatile plant compounds in field ambient air is important to understand chemical communication between plants and insects and will aid the development of semiochemicals from plants for pest control. In this study, a thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method was developed to measure ultra-trace levels of volatile plant compounds in field ambient air. The desorption parameters of TD, including sorbent tube material, tube desorption temperature, desorption time, and cold trap temperature, were selected and optimized. In GC-MS analysis, the selected ion monitoring mode was used for enhanced sensitivity and selectivity. This method was sufficiently sensitive to detect part-per-trillion levels of volatile plant compounds in field ambient air. Laboratory and field evaluation revealed that the method presented high precision and accuracy. Field studies indicated that the background odor of tea plantations contained some common volatile plant compounds, such as (Z)-3-hexenol, methyl salicylate, and (E)-ocimene, at concentrations ranging from 1 to 3400 ng m(-3). In addition, the background odor in summer was more abundant in quality and quantity than in autumn. Relative to previous methods, the TD-GC-MS method is more sensitive, permitting accurate qualitative and quantitative measurements of volatile plant compounds in field ambient air.

  9. Controlling particulates, temperature, and tritium in an inert glovebox for a weapons program

    SciTech Connect

    Purson, J.D.; Powers, D.; Walthers, C.; Navarro, C.; Newman, E.; Romero, J.; Jenkins, R.

    1996-07-01

    A glovebox is described in which several environmental parameters are controlled and monitored. Included in these are particulate, tritium, water vapor, oxygen and temperature. The paper details the design rationale and process and describes the glovebox, presently in use for neutron generator production.

  10. Temperature Control with Two Parallel Small Loop Heat Pipes for GLM Program

    NASA Technical Reports Server (NTRS)

    Khrustalev, Dmitry; Stouffer, Chuck; Ku, Jentung; Hamilton, Jon; Anderson, Mark

    2014-01-01

    The concept of temperature control of an electronic component using a single Loop Heat Pipe (LHP) is well established for Aerospace applications. Using two LHPs is often desirable for redundancy/reliability reasons or for increasing the overall heat source-sink thermal conductance. This effort elaborates on temperature controlling operation of a thermal system that includes two small ammonia LHPs thermally coupled together at the evaporator end as well as at the condenser end and operating "in parallel". A transient model of the LHP system was developed on the Thermal Desktop (TradeMark) platform to understand some fundamental details of such parallel operation of the two LHPs. Extensive thermal-vacuum testing was conducted with two thermally coupled LHPs operating simultaneously as well as with only one LHP operating at a time. This paper outlines the temperature control procedures for two LHPs operating simultaneously with widely varying sink temperatures. The test data obtained during the thermal-vacuum testing, with both LHPs running simultaneously in comparison with only one LHP operating at a time, are presented with detailed explanations.

  11. Sorption, desorption, and speciation of Cd, Ni, and Fe by four calcareous soils as affected by pH.

    PubMed

    Tahervand, Samaneh; Jalali, Mohsen

    2016-06-01

    The sorption, desorption, and speciation of cadmium (Cd), nickel (Ni), and iron (Fe) in four calcareous soils were investigated at the pH range of 2-9. The results indicated that sorption of Fe by four soils was higher than 80 % at pH 2, while in the case of Cd and Ni was less than 30 %. The most common sequence of metal sorption at pH 2-9 for four soils was in the order of Fe ≫ Ni > Cd. Cadmium and Ni sorption as a function of pH showed the predictable trend of increasing metal sorption with increase in equilibrium pH, while the Fe sorption trend was different and characterized by three phases. With regard to the order of Cd, Ni, and Fe sorption on soils, Cd and Ni showed high affinity for organic matter (OM), whereas Fe had high tendency for calcium carbonate (CaCO3). Results of metal desorption using 0.01 M NaCl demonstrated that metal sorption on soils containing high amounts of CaCO3 was less reversible in comparison to soils containing high OM. In general, Cd and Ni desorption curves were characterized by three phases; (1) the greatest desorption at pH 2, (2) the low desorption at pH 3-7, and (3) the least desorption at pH > 7. The MINTEQ speciation solubility program showed that the percentage of free metals declined markedly with increase of pH, while the percentage of carbonate and hydroxyl species increased. Furthermore, MINTEQ predicted that saturation index (SI) of metals increased with increasing pH.

  12. Sorption, desorption, and speciation of Cd, Ni, and Fe by four calcareous soils as affected by pH.

    PubMed

    Tahervand, Samaneh; Jalali, Mohsen

    2016-06-01

    The sorption, desorption, and speciation of cadmium (Cd), nickel (Ni), and iron (Fe) in four calcareous soils were investigated at the pH range of 2-9. The results indicated that sorption of Fe by four soils was higher than 80 % at pH 2, while in the case of Cd and Ni was less than 30 %. The most common sequence of metal sorption at pH 2-9 for four soils was in the order of Fe ≫ Ni > Cd. Cadmium and Ni sorption as a function of pH showed the predictable trend of increasing metal sorption with increase in equilibrium pH, while the Fe sorption trend was different and characterized by three phases. With regard to the order of Cd, Ni, and Fe sorption on soils, Cd and Ni showed high affinity for organic matter (OM), whereas Fe had high tendency for calcium carbonate (CaCO3). Results of metal desorption using 0.01 M NaCl demonstrated that metal sorption on soils containing high amounts of CaCO3 was less reversible in comparison to soils containing high OM. In general, Cd and Ni desorption curves were characterized by three phases; (1) the greatest desorption at pH 2, (2) the low desorption at pH 3-7, and (3) the least desorption at pH > 7. The MINTEQ speciation solubility program showed that the percentage of free metals declined markedly with increase of pH, while the percentage of carbonate and hydroxyl species increased. Furthermore, MINTEQ predicted that saturation index (SI) of metals increased with increasing pH. PMID:27147235

  13. Hydrogen adsorption and desorption with 3D silicon nanotube-network and film-network structures: Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Li, Ming; Huang, Xiaobo; Kang, Zhan

    2015-08-01

    Hydrogen is clean, sustainable, and renewable, thus is viewed as promising energy carrier. However, its industrial utilization is greatly hampered by the lack of effective hydrogen storage and release method. Carbon nanotubes (CNTs) were viewed as one of the potential hydrogen containers, but it has been proved that pure CNTs cannot attain the desired target capacity of hydrogen storage. In this paper, we present a numerical study on the material-driven and structure-driven hydrogen adsorption of 3D silicon networks and propose a deformation-driven hydrogen desorption approach based on molecular simulations. Two types of 3D nanostructures, silicon nanotube-network (Si-NN) and silicon film-network (Si-FN), are first investigated in terms of hydrogen adsorption and desorption capacity with grand canonical Monte Carlo simulations. It is revealed that the hydrogen storage capacity is determined by the lithium doping ratio and geometrical parameters, and the maximum hydrogen uptake can be achieved by a 3D nanostructure with optimal configuration and doping ratio obtained through design optimization technique. For hydrogen desorption, a mechanical-deformation-driven-hydrogen-release approach is proposed. Compared with temperature/pressure change-induced hydrogen desorption method, the proposed approach is so effective that nearly complete hydrogen desorption can be achieved by Si-FN nanostructures under sufficient compression but without structural failure observed. The approach is also reversible since the mechanical deformation in Si-FN nanostructures can be elastically recovered, which suggests a good reusability. This study may shed light on the mechanism of hydrogen adsorption and desorption and thus provide useful guidance toward engineering design of microstructural hydrogen (or other gas) adsorption materials.

  14. Hydrogen adsorption and desorption with 3D silicon nanotube-network and film-network structures: Monte Carlo simulations

    SciTech Connect

    Li, Ming; Kang, Zhan; Huang, Xiaobo

    2015-08-28

    Hydrogen is clean, sustainable, and renewable, thus is viewed as promising energy carrier. However, its industrial utilization is greatly hampered by the lack of effective hydrogen storage and release method. Carbon nanotubes (CNTs) were viewed as one of the potential hydrogen containers, but it has been proved that pure CNTs cannot attain the desired target capacity of hydrogen storage. In this paper, we present a numerical study on the material-driven and structure-driven hydrogen adsorption of 3D silicon networks and propose a deformation-driven hydrogen desorption approach based on molecular simulations. Two types of 3D nanostructures, silicon nanotube-network (Si-NN) and silicon film-network (Si-FN), are first investigated in terms of hydrogen adsorption and desorption capacity with grand canonical Monte Carlo simulations. It is revealed that the hydrogen storage capacity is determined by the lithium doping ratio and geometrical parameters, and the maximum hydrogen uptake can be achieved by a 3D nanostructure with optimal configuration and doping ratio obtained through design optimization technique. For hydrogen desorption, a mechanical-deformation-driven-hydrogen-release approach is proposed. Compared with temperature/pressure change-induced hydrogen desorption method, the proposed approach is so effective that nearly complete hydrogen desorption can be achieved by Si-FN nanostructures under sufficient compression but without structural failure observed. The approach is also reversible since the mechanical deformation in Si-FN nanostructures can be elastically recovered, which suggests a good reusability. This study may shed light on the mechanism of hydrogen adsorption and desorption and thus provide useful guidance toward engineering design of microstructural hydrogen (or other gas) adsorption materials.

  15. Programs.

    ERIC Educational Resources Information Center

    Community College Journal, 1996

    1996-01-01

    Includes a collection of eight short articles describing model community college programs. Discusses a literacy program, a mobile computer classroom, a support program for at-risk students, a timber-harvesting program, a multimedia presentation on successful women graduates, a career center, a collaboration with NASA, and an Israeli engineering…

  16. Salt-assisted thermal desorption of mercury from contaminated dredging sludge.

    PubMed

    Comuzzi, Clara; Lesa, Barbara; Aneggi, Eleonora; Dolcetti, Giuliano; Goi, Daniele

    2011-10-15

    In this study, we tested a new procedure for the decontamination of mercury-polluted dredging sludge (Marano-Grado Lagoon, northeastern Italy) based on cationic exchange associated with thermal desorption at a low temperature. Four mercury-polluted sludge slurries were treated using thermal desorption at 393 K for 2h. Three different salts, NaCl (sodium chloride), (CH(3))(4)NCl (tetramethylammonium chloride) and (C(4)H(9))(4)NCl (tetrabutylammonium chloride) were used as exchangers. The selected salts have a monovalent cationic part that progressively increases in molecular weight. The results show that the association of cationic exchange with thermal treatment leads to a significant improvement in the removal of mercury from the contaminated material at a low temperature compared to samples that were not treated with salt. The highest levels of decontamination were attained were obtained when the slurries, which had mercury pollution ranging from 20 to 200 ppm, were treated with a 15% solution of (C(4)H(9))(4)NCl. The efficiency of the removal at 393 K (from 24% up to 60%) depended on the nature of the sample. When the samples were treated at a similar temperature without the salt, no remediation of mercury was detected. Our results show that the thermal decontamination temperature can be significantly lowered by this remediation approach, which is the first example based on cationic exchange of the pollutant with an appropriate salt. PMID:21813235

  17. Salt-assisted thermal desorption of mercury from contaminated dredging sludge.

    PubMed

    Comuzzi, Clara; Lesa, Barbara; Aneggi, Eleonora; Dolcetti, Giuliano; Goi, Daniele

    2011-10-15

    In this study, we tested a new procedure for the decontamination of mercury-polluted dredging sludge (Marano-Grado Lagoon, northeastern Italy) based on cationic exchange associated with thermal desorption at a low temperature. Four mercury-polluted sludge slurries were treated using thermal desorption at 393 K for 2h. Three different salts, NaCl (sodium chloride), (CH(3))(4)NCl (tetramethylammonium chloride) and (C(4)H(9))(4)NCl (tetrabutylammonium chloride) were used as exchangers. The selected salts have a monovalent cationic part that progressively increases in molecular weight. The results show that the association of cationic exchange with thermal treatment leads to a significant improvement in the removal of mercury from the contaminated material at a low temperature compared to samples that were not treated with salt. The highest levels of decontamination were attained were obtained when the slurries, which had mercury pollution ranging from 20 to 200 ppm, were treated with a 15% solution of (C(4)H(9))(4)NCl. The efficiency of the removal at 393 K (from 24% up to 60%) depended on the nature of the sample. When the samples were treated at a similar temperature without the salt, no remediation of mercury was detected. Our results show that the thermal decontamination temperature can be significantly lowered by this remediation approach, which is the first example based on cationic exchange of the pollutant with an appropriate salt.

  18. 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.

  19. 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.

  20. Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

    NASA Astrophysics Data System (ADS)

    Leuenberger, M. C.; Schibig, M. F.; Nyfeler, P.

    2015-12-01

    It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i) physisorption and (ii) chemisorption. Physisorption is associated with lower binding energies in the order of 1-10 kJ mol-1, compared to chemisorption which ranges from 100 to 1000 kJ mol-1. Furthermore, chemisorption only forms monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws; however, it can be influenced by hysteresis effects. In the present experiment, we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. Our observations from completely decanting one steel and two aluminium cylinders are in agreement with the pressure dependence of physisorption for CO2, CH4, and H2O. The CO2 results for both cylinder types are in excellent agreement with the pressure dependence of a monolayer adsorption model. However, mole fraction changes due to adsorption on aluminium (< 0.05 and 0 ppm for CO2 and H2O) were significantly lower than on steel (< 0.41 ppm and about < 2.5 ppm, respectively). The CO2 amount adsorbed (5.8 × 1019 CO2 molecules) corresponds to about the fivefold monolayer adsorption, indicating that the effective surface exposed for adsorption is significantly larger than the geometric surface area. Adsorption/desorption effects were minimal for CH4 and for CO but require further attention since they were only studied on one aluminium cylinder with a very low mole fraction. In the climate chamber, the cylinders were exposed to temperatures between -10 and +50 °C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO2, ranging from 0.0014 to 0.0184 ppm °C-1 for steel cylinders and -0.0002 to -0

  1. State-coupled low temperature geothermal resource assessment program, fiscal year 1982. Final Technical Report

    SciTech Connect

    Icerman, Larry

    1983-08-01

    This report summarizes the results of low-temperature geothermal energy resource assessment efforts in New Mexico during the period from June 15, 1981 through September 30, 1983, under the sponsorship of the US Department of Energy (Contract DE-AS07-78ID01717). The report is divided into four chapters which correspond to the tasks delineated in the contract. Chapter 5 is a brief summary of the tasks performed under this contract during the period October 1, 1978, through June 30, 1983. This work extends the knowledge of low-temperature geothermal reservoirs with the potential for direct heating applications in New Mexico. The research effort focused on compiling basic geothermal data throughout selected areas in New Mexico in a format suitable for direct transfer to the US Geological Survey for inclusion in the GEOTHERM data file and to the National Oceanic and Atmospheric Administration for use with New Mexico geothermal resources maps.

  2. 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.

  3. CRC (Coordinating Research Council) two-temperature vapor-lock program using gasoline-alcohol blends, 1983

    SciTech Connect

    Not Available

    1986-10-01

    The effect of oxygenated fuels on vapor lock performance was evaluated in a program conducted during the fall of 1983 at the Yuma Proving Grounds in Arizona. Eighteen 1984 model-year cars, representing a reasonable model mix, were tested using two hydrocarbon-base fuels and nine hydrocarbon-base fuels mixed with methanol and methanol/tertiary butyl alcohol mixtures at 1/1 and 4/1 ratios (respectively) at a concentration of 3.5% by weight oxygen. Tests were conducted at nominal ambient temperatures of 95F (35C) and 70F (21C).

  4. Temperature-programmed sulfiding of MoO/sub 3//Al/sub 2/O/sub 3/ catalysts

    SciTech Connect

    Arnoldy, P.; van den Heijkant, J.A.M.; de Bok, G.D.; Moulijn, J.A.

    1985-03-01

    The conversion of oxides into sulfides has been studied by means of temperature-programmed sulfiding (TPS). In TPS the H/sub 2/S, H/sub 2/O, and H/sub 2/ concentrations are measured continuously during sulfiding with a H/sub 2/S/H/sub 2//Ar mixture, as a function of temperature. Application of TPS to MoO/sub 3//Al/sub 2/O/sub 3/ hydrodesulfurization catalysts leads to detailed information on the sulfiding rate and mechanism. Sulfiding of MoO/sub 3//Al/sub 2/O/sub 3/ takes place at low temperature in comparison with bulk compounds (MoO/sub 3/, MoO/sub 2/). The sulfiding mechanism is dominated by O-S exchange reactions. Elemental sulfur is formed by rupture of metal sulfide bonds and is reduced subsequently by H/sub 2/. In fact, H/sub 2/ plays only a minor role in sulfiding at low temperatures. Particularly the ''H/sub 2/O content'' of the catalysts influences the sulfiding rate to a large extent. Wet catalysts, in equilibrium with 3% H/sub 2/O/Ar at room temperature, sulfide at very low temperature (typically 400 to 500 K). Dry catalysts, treated in Ar at 775 K, on the other hand, sulfide at relatively high temperature (600 to 700 K). This H/sub 2/O effect is explained tentatively by catalysis of O-S exchange by Broensted acid sites. Prereduction hinders sulfiding more than predrying. This suggests a minor importance of reduced intermediates in normal sulfiding procedures. An increase in the Mo content (0.5 to 4.5 atoms/nm/sup 2/) leads to sulfiding at lower temperature, but the influence of Mo content is not as pronounced as has been found in TPR reducibility studies. The influence of Mo content on TPR and TPS is explained by detailed consideration of the heterogeneity. Sulfiding of a 4.5 atom/nm/sup 2/ catalyst can be completed at ca. 500 K, up to a S/Mo ratio of 1.9, provided that a sufficiently low heating rate is chosen. The fact that such a low temperature is sufficient suggests the initial formation of monolayer-type sulfide species with a S/Mo ratio near 2

  5. Technical Note: In-situ derivatization thermal desorption GC-TOFMS for direct analysis of particle-bound non-polar and polar organic species

    NASA Astrophysics Data System (ADS)

    Orasche, J.; Schnelle-Kreis, J.; Abbaszade, G.; Zimmermann, R.

    2011-09-01

    An in-situ derivatization thermal desorption method followed by gas chromatography and time-of-flight mass spectrometry (IDTD-GC-TOFMS) was developed for determination of polar organic compounds together with non-polar compounds in one measurement. Hydroxyl and carboxyl groups of compounds such as anhydrous sugars, alcohols and phenols, fatty acids and resin acids are targets of the derivatization procedure. Derivatization is based on silylation with N-Methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA) during the step of thermal desorption. The high temperature of 300 °C during desorption is utilized for the in-situ derivatization on the collection substrate (quartz fibre filters) accelerating the reaction rate. Thereby, the analysis time is as short as without derivatization. At first the filter surface is dampened with derivatization reagent before insertion of the sample into the thermal desorption unit. To ensure ongoing derivatization during thermal desorption the carrier gas is enriched with MSTFA until the desorption procedure is finished. The precisions of all studied analytes were below 17 % within a calibration range from 22 pg (abietic acid) up to 342 ng (levoglucosan). Limits of quantification (LOQ) for polycyclic aromatic hydrocarbons (PAH) were between 1 pg (fluoranthene) and 8 pg (indeno[1,2,3-cd]pyrene), for resin acids 37-102 pg and for studied phenols 4-144 pg. LOQ for levoglucosan was 17 pg.

  6. Thermal desorption of CO and H2 from degassed 304 and 347 stainless steel

    SciTech Connect

    Rezaie-Serej, S.; Outlaw, R.A.

    1994-10-01

    Thermal desorption spectroscopy (TDS), along with Auger electron spectroscopy, was used to study the desorption of H2 and CO from baked 304 and 347 stainless-steel samples exposed only to residual gases. Both 347 and 304 samples gave identical TDS spectra. The spectra for CO contained a sharp leading peak centered in the temperature range 410-440C and an exponentially increasing part for temperatures higher than 500C, with a small peak around 600C appearing as a shoulder. The leading peak followed a second-order desorption behavior with an activation energy of 28+/-2 kcal/mol, suggesting that the rate-limiting step for this peak is most likely a surface reaction that produces the CO molecules in the surface layer. The amount of desorbed CO corresponding to this peak was approximately 0.5X10(exp 14) molecules/cm(exp 2) . The exponentially rising part of the CO spectrum appeared to originate from a bulk diffusion process. The TDS spectrum for H2 consisted of a main peak centered also in the temperature range 410-440C, with two small peaks appearing as shoulders at approximately 500 and 650C. The main peak in this case also displayed a second-order behavior with an activation energy of 14+/-2 kcal/mol. The amount of desorbed H2, approximately 1.9X 10(exp 15) molecules/cm(exp 2) , appeared to be independent of the concentration of hydrogen in the bulk, indicating that the majority of the desorbed H2 originated from the surface layer.

  7. Thermal desorption of CO and H2 from degassed 304 and 347 stainless steel

    NASA Technical Reports Server (NTRS)

    Rezaie-Serej, S.; Outlaw, R. A.

    1994-01-01

    Thermal desorption spectroscopy (TDS), along with Auger electron spectroscopy, was used to study the desorption of H2 and CO from baked 304 and 347 stainless-steel samples exposed only to residual gases. Both 347 and 304 samples gave identical TDS spectra. The spectra for CO contained a sharp leading peak centered in the temperature range 410-440C and an exponentially increasing part for temperatures higher than 500C, with a small peak around 600C appearing as a shoulder. The leading peak followed a second-order desorption behavior with an activation energy of 28+/-2 kcal/mol, suggesting that the rate-limiting step for this peak is most likely a surface reaction that produces the CO molecules in the surface layer. The amount of desorbed CO corresponding to this peak was approximately 0.5X10(exp 14) molecules/cm(exp 2) . The exponentially rising part of the CO spectrum appeared to originate from a bulk diffusion process. The TDS spectrum for H2 consisted of a main peak centered also in the temperature range 410-440C, with two small peaks appearing as shoulders at approximately 500 and 650C. The main peak in this case also displayed a second-order behavior with an activation energy of 14+/-2 kcal/mol. The amount of desorbed H2, approximately 1.9X 10(exp 15) molecules/cm(exp 2) , appeared to be independent of the concentration of hydrogen in the bulk, indicating that the majority of the desorbed H2 originated from the surface layer.

  8. Negligible photodesorption of methanol ice and active photon-induced desorption of its irradiation products

    NASA Astrophysics Data System (ADS)

    Cruz-Diaz, G. A.; Martín-Doménech, R.; Muñoz Caro, G. M.; Chen, Y.-J.

    2016-07-01

    Context. Methanol is a common component of interstellar and circumstellar ice mantles and is often used as an evolution indicator in star-forming regions. The observations of gas-phase methanol in the interiors of dense molecular clouds at temperatures as low as 10 K suggest that non-thermal ice desorption must be active. Ice photodesorption has been proposed to explain the abundances of gas-phase molecules toward the coldest regions. Aims: Laboratory experiments were performed to investigate the potential photodesorption of methanol toward the coldest regions. Methods: Solid methanol was deposited at 8 K and UV-irradiated at various temperatures starting from 8 K. The irradiation of the ice was monitored by means of infrared spectroscopy and the molecules in the gas phase were detected using quadrupole mass spectroscopy. Fully deuterated methanol was used for confirmation of the results. Results: The photodesorption of methanol to the gas phase was not observed in the mass spectra at different irradiation temperatures. We estimate an upper limit of 3 × 10-5 molecules per incident photon. On the other hand, photon-induced desorption of the main photoproducts was clearly observed. Conclusions: The negligible photodesorption of methanol could be explained by the ability of UV-photons in the 114-180 nm (10.87-6.88 eV) range to dissociate this molecule efficiently. Therefore, the presence of gas-phase methanol in the absence of thermal desorption remains unexplained. On the other hand, we find CH4 to desorb from irradiated methanol ice, which was not found to desorb in the pure CH4 ice irradiation experiments.

  9. 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.

  10. DNASynth: A Computer Program for Assembly of Artificial Gene Parts in Decreasing Temperature

    PubMed Central

    Nowak, Robert M.; Wojtowicz-Krawiec, Anna; Plucienniczak, Andrzej

    2015-01-01

    Artificial gene synthesis requires consideration of nucleotide sequence development as well as long DNA molecule assembly protocols. The nucleotide sequence of the molecule must meet many conditions including particular preferences of the host organism for certain codons, avoidance of specific regulatory subsequences, and a lack of secondary structures that inhibit expression. The chemical synthesis of DNA molecule has limitations in terms of strand length; thus, the creation of artificial genes requires the assembly of long DNA molecules from shorter fragments. In the approach presented, the algorithm and the computer program address both tasks: developing the optimal nucleotide sequence to encode a given peptide for a given host organism and determining the long DNA assembly protocol. These tasks are closely connected; a change in codon usage may lead to changes in the optimal assembly protocol, and the lack of a simple assembly protocol may be addressed by changing the nucleotide sequence. The computer program presented in this study was tested with real data from an experiment in a wet biological laboratory to synthesize a peptide. The benefit of the presented algorithm and its application is the shorter time, compared to polymerase cycling assembly, needed to produce a ready synthetic gene. PMID:25629047

  11. Application of ASTM E-1559 Apparatus to Study H2O Desorption

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael; Perry, Radford, III; Meadows, George A.

    2015-01-01

    The NASA James Webb Space Telescope project identified a need to measure water vapor desorption from cryogenic surfaces in order to validate predictions of spacecraft design performance. A review of available scientific literature indicated no such measurements had been reported below 131 K. Contamination control personnel at NASA Goddard Space Flight Center recognized the possibility they readily possessed the means to collect these measurements at lower temperatures using an existing apparatus commonly employed for making outgassing observations. This presentation will relate how the ASTM E-1559 Molekit apparatus was used without physical modification to measure water vapor sublimation down to 120 K and compare this data to existing equilibrium vapor pressure models.

  12. Desorption Induced by Excited Electrons from Semiconductor Surfaces (I)
    Desorption Induced by Electron-/hole-injection into Halogen-adsorbed Silicon Surfaces—

    NASA Astrophysics Data System (ADS)

    Shudo, Kenichi; Tanaka, Masatoshi

    We review excited-electron-induced desorption from halogen-adsorbed semiconductor surfaces, focusing on desorption processes associated with electron-beam irradiation using an electron gun and hole-injection using a scanning tunneling microscope. Recent studies on halogen-adsorbed silicon surfaces, i.e., typical etching systems, are described from the viewpoint of desorption induced by electronic transitions (DIET).

  13. The laser desorption/laser ionization mass spectra of some methylated xanthines and the laser desorption of caffeine and theophylline from thin layer chromatography plates

    NASA Astrophysics Data System (ADS)

    Rogers, Kevin; Milnes, John; Gormally, John

    1993-02-01

    Laser desorption/laser ionization time-of-flight mass spectra of caffeine, theophylline, theobromine and xanthine are reported. These mass spectra are compared with published spectra obtained using electron impact ionization. Mass spectra of caffeine and theophylline obtained by IR laser desorption from thin layer chromatography plates are also described. The laser desorption of materials from thin layer chromatography plates is discussed.

  14. 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.

  15. 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.

  16. Influence of surface coverage on the chemical desorption process.

    PubMed

    Minissale, M; Dulieu, F

    2014-07-01

    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+O2) 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 N2 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.

  17. Influence of surface coverage on the chemical desorption process

    SciTech Connect

    Minissale, M.; Dulieu, F.

    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.

  18. Ultrasonic desorption of petroleum hydrocarbons from crude oil contaminated soils.

    PubMed

    Li, Jianbing; Song, Xinyuan; Hu, Guangji; Thring, Ronald Wallen

    2013-01-01

    Ultrasonic irradiation was applied to improve the desorption of petroleum hydrocarbons (PHC) in crude oil from three types of soil. Soil A was an Ottawa sand, while soil B and soil C were fine soils that contained 27.6% and 55.3% of silt and clay contents, respectively. It was found that the ultrasonic desorption was highly related to soil types, with the highest and the lowest desorption occurring in coarse soil (i.e., soil A) and finer soil (i.e., soil C), respectively. Under the experimental conditions, the maximum ultrasonic desorption enhancement of the total petroleum hydrocarbons (TPH) reached 22% for soil A, 61% for soil B, and 49% for soil C, respectively. The maximum enhancement on the F2 (n-C10 to n-C16), F3 (n-C16 to n-C34), and F4 (n-C34 to n-C50) fractions of PHC reached 91, 44, and 51% for soil B, and 90, 38, and 31% for soil C, respectively. The desorption enhancement also illustrated an increasing trend with initial soil TPH concentration. PMID:23705614

  19. Intramolecular motion in DIET: Desorption and dissociation of chemisorbed ammonia

    NASA Astrophysics Data System (ADS)

    Burns, A. R.; Stechel, E. B.; Jennison, D. R.

    1995-06-01

    We show that quantum-specific detection of DIET processes of polyatomic adsorbates reveals the multidimensional dynamics of intramolecular motion. Specifically, we present an analysis of the 6-350 eV electron-induced desorption and dissociation of chemisorbed NH 3 and ND 3 on Pt(1 1 1). State-selective detection of the neutral DIET products is accomplished by 2 + 1 resonance-enhanced multiphoton ionization (REMPI). Desorption and dissociation occur as a result of distinct electronic excitations that result in different, uncoupled, modes of intramolecular motion. We find that desorption results from 3a 1-1-induced inversion motion. Trajectories on a two-dimensional potential energy surface reveal that the excited molecule fully inverts; upon deexcitation, the inverted molecule is sufficiently high on the hard wall of the substrate interaction to have enough energy to desorb. Given the short excitation lifetime, the time scale in which the (H) D atoms reach the inversion geometry directly affects the desorption yield and results in an appreciable enhancement of NH 3 desorption over that of ND 3. In general, multidimensional molecule-surface potential energy surfaces should be considered in DIET processes involving molecular adsorbates.

  20. Temperature based daily incoming solar radiation modeling based on gene expression programming, neuro-fuzzy and neural network computing techniques.

    NASA Astrophysics Data System (ADS)

    Landeras, G.; López, J. J.; Kisi, O.; Shiri, J.

    2012-04-01

    The correct observation/estimation of surface incoming solar radiation (RS) is very important for many agricultural, meteorological and hydrological related applications. While most weather stations are provided with sensors for air temperature detection, the presence of sensors necessary for the detection of solar radiation is not so habitual and the data quality provided by them is sometimes poor. In these cases it is necessary to estimate this variable. Temperature based modeling procedures are reported in this study for estimating daily incoming solar radiation by using Gene Expression Programming (GEP) for the first time, and other artificial intelligence models such as Artificial Neural Networks (ANNs), and Adaptive Neuro-Fuzzy Inference System (ANFIS). Traditional temperature based solar radiation equations were also included in this study and compared with artificial intelligence based approaches. Root mean square error (RMSE), mean absolute error (MAE) RMSE-based skill score (SSRMSE), MAE-based skill score (SSMAE) and r2 criterion of Nash and Sutcliffe criteria were used to assess the models' performances. An ANN (a four-input multilayer perceptron with ten neurons in the hidden layer) presented the best performance among the studied models (2.93 MJ m-2 d-1 of RMSE). A four-input ANFIS model revealed as an interesting alternative to ANNs (3.14 MJ m-2 d-1 of RMSE). Very limited number of studies has been done on estimation of solar radiation based on ANFIS, and the present one demonstrated the ability of ANFIS to model solar radiation based on temperatures and extraterrestrial radiation. By the way this study demonstrated, for the first time, the ability of GEP models to model solar radiation based on daily atmospheric variables. Despite the accuracy of GEP models was slightly lower than the ANFIS and ANN models the genetic programming models (i.e., GEP) are superior to other artificial intelligence models in giving a simple explicit equation for the

  1. Temperature-Programmed Scattering (TPS) Study on Reactivity Difference of GaAs and GaAs Oxide Surfaces

    NASA Astrophysics Data System (ADS)

    Sasaki, Masahiro; Yoshida, Seikoh; Yamada, Chikashi

    1993-10-01

    The reactivity of GaAs and GaAs oxide surfaces to trimethylgallium (TMG) was studied by temperature-programmed scattering (TPS) through the energy accommodation coefficient (EAC). The substrate temperature was increased at a constant rate while the scattered TMG was being measured under a constant flux of TMG supplied to the substrate by a cryo-shrouded quadrupole mass spectrometer. Since the detection efficiency of the spectrometer is inversely proportional to the translational velocity of scattered TMG, the observed intensity variation represents the change in translational velocity of reflected TMG during the temperature increase. The variation of the signal intensities was least-squares analyzed to yield the EAC, which is a measure of the surface reactivity. The thus-obtained reactivity of photo-oxidized GaAs to TMG is smaller than that of dark-oxidized GaAs, which is even smaller than that of a bare GaAs surface. This difference in the reactivity is discussed in relation to the mechanism of selective area growth of GaAs using GaAs oxide as a mask.

  2. 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.

  3. 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 μg with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. [Figure not available: see fulltext.

  4. Nitrogen Molecule Adsorption on Cationic Tantalum Clusters and Rhodium Clusters and Desorption from Their Nitride Clusters Studied by Thermal Desorption Spectrometry.

    PubMed

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-06-23

    Adsorption and desorption of N2 molecules onto cationic Ta and Rh clusters in the gas phase were investigated in the temperature range of 300-1000 K by using thermal desorption spectrometry in combination with density functional theory (DFT) calculations. For Ta6(+), the first N2 molecule was found to adsorb dissociatively, and it remained adsorbed when Ta6(+)N2 was heated to 1000 K. In contrast, the second and the subsequent N2 molecules adsorbed weakly as a molecular form and were released into the gas phase when heated to 600 K. The difference can be explained in terms of the activation barrier between the molecular and dissociative forms. On the other hand, when Ta clusters were generated in the presence of N2 gas by the laser ablation of a Ta rod, isomeric clusters, TanNm(+), having heat resistivity were formed. For Rh6(+), N2 adsorbed molecularly at 300 K and desorbed totally at 450 K. These results were consistent with the DFT calculations, indicating that the dissociative adsorption of N2 is endothermic. PMID:27276438

  5. 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.

  6. DEVELOPMENT OF HIGH ACTIVITY, COAL-DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

    SciTech Connect

    Joseph M. Calo

    2000-07-21

    This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics. During the reporting period, the following has been accomplished: (1) Steady-state reactivity studies in the packed bed reactor were extended to the NO/CO-carbon reaction system as a function of temperature and NO and CO concentrations. It was found that the NO reaction rate increased in the presence of CO, and the apparent activation energy decreased to about 75 {+-} 8 kJ/mol. In addition, the influence of mass transfer limitations were noted at low NO and CO concentrations. (2) The packed bed reactor/gas flow system has been applied to performing post-reaction temperature programmed desorption (TPD) studies of intermediate surface complexes following steady-state reaction. It was found that the amount of CO-evolving intermediate surface complexes exceeded that of the N{sub 2}-evolving surface complexes, and that both increased with reaction temperature. The TPD spectra indicates that both types of complexes desorb late, suggesting that they have high desorption activation energies. Plans for the next reporting period include extending the temperature programmed desorption studies in the packed bed reactor system to the NO/CO reaction system, including exposure to just CO, as well as NO/CO mixtures.

  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. Catalytic membrane program novation: High temperature catalytic membrane reactors. Final report

    SciTech Connect

    Kleiner, R.N.

    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.

  9. Enhanced saturation coverages in adsorption-desorption processes

    NASA Astrophysics Data System (ADS)

    Van Tassel, Paul R.; Viot, Pascal; Tarjus, Gilles; Ramsden, Jeremy J.; Talbot, Julian

    2000-01-01

    Many experimental studies of protein deposition on solid surfaces involve alternating adsorption/desorption steps. In this paper, we investigate the effect of a desorption step (separating two adsorption steps) on the kinetics, the adsorbed-layer structure, and the saturation density. Our theoretical approach involves a density expansion of the pair distribution function and an application of an interpolation formula to estimate the saturation density as a function of the density at which the desorption process commences, ρ1, and the density of the depleted configuration, ρ2. The theory predicts an enhancement of the saturation density compared with that of a simple, uninterrupted random sequential adsorption (RSA) process and a maximum in the saturation density when ρ2=(2/3)ρ1. The theoretical results are in qualitative and semiquantitative agreement with the results of numerical simulations.

  10. Pulsed UV laser induced desorption of ions from aluminum

    NASA Astrophysics Data System (ADS)

    Taylor, David Paul; Helvajian, Henry

    2000-04-01

    A study of pulsed UV laser induced desorption (LID) has been performed on an Al(111) sample. The positive ion desorption was investigated at low laser fluence, in a regime in which the ion yield exhibits a highly non-linear dependence on the laser fluence. The peak of the kinetic energy distribution of the desorbed ions has been measured to be about 15 eV. This result is consistent with the conjecture that the ion departing the metal surface can acquire a kinetic energy kick from a process associated with plasmon annihilation. The Al + ion kinetic energy peak is asymmetric and about 3 eV full-width at half-maximum (FWHM). This experiment indicates that plasmon excitation can play a significant role in laser stimulated desorption induced by electronic transitions (DIET).

  11. Desorption Mass Spectrometry for Nonvolatile Compounds Using an Ultrasonic Cutter

    NASA Astrophysics Data System (ADS)

    Habib, Ahsan; Ninomiya, Satoshi; Chen, Lee Chuin; Usmanov, Dilshadbek T.; Hiraoka, Kenzo

    2014-07-01

    In this work, desorption of nonvolatile analytes induced by friction was studied. The nonvolatile compounds deposited on the perfluoroalkoxy substrate were gently touched by an ultrasonic cutter oscillating with a frequency of 40 kHz. The desorbed molecules were ionized by a dielectric barrier discharge (DBD) ion source. Efficient desorption of samples such as drugs, pharmaceuticals, amino acids, and explosives was observed. The limits of detection for these compounds were about 1 ng. Many compounds were detected in their protonated forms without undergoing significant fragmentation. When the DBD was off, no ions for the neutral samples could be detected, meaning that only desorption along with little ionization took place by the present technique.

  12. Desorption yields of differently treated copper samples characterized with ERDA

    NASA Astrophysics Data System (ADS)

    Bender, M.; Kollmus, H.; Assmann, W.

    2007-03-01

    In heavy ion accelerators the beam line vacuum is affected by lost ions impinging onto the wall of the beam pipe. Due to ion-induced desorption gas is released from the beam pipe into the vacuum. This vacuum degradation affects the ion beam life time and is a serious luminosity limitation for a heavy ion synchrotron like SIS18 at GSI. Here we report on a new approach measuring desorption yields parallel to an in situ target characterization using elastic recoil detection analysis (ERDA). With this experimental setup we are able to show clear correlations between oxide layers and the desorption behavior, even though the sputtered oxide is not the major content of the released gas.

  13. Multiple sample characterization of coals and other substances by controlled-atmosphere programmed temperature oxidation

    DOEpatents

    LaCount, Robert B.

    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.

  14. Temperature dependence of the heterogeneous reaction of carbonyl sulfide on magnesium oxide.

    PubMed

    Liu, Yongchun; He, Hong; Ma, Qingxin

    2008-04-01

    The experimental determination of rate constants for atmospheric reactions and how these rate constants vary with temperature remain a crucially important part of atmosphere science. In this study, the temperature dependence of the heterogeneous reaction of carbonyl sulfide (COS) on magnesium oxide (MgO) has been investigated using a Knudsen cell reactor and a temperature-programmed reaction apparatus. We found that the adsorption and the heterogeneous reaction are sensitive to temperature. The initial uptake coefficients (gammat(Ini)) of COS on MgO decrease from 1.07 +/- 0.71 x 10-6 to 4.84 +/- 0.60 x 10-7 with the increasing of temperature from 228 to 300 K, and the steady state uptake coefficients (gammat(SS)) increase from 5.31 +/- 0.06 x 10-8 to 1.68 +/- 0.41 x 10-7 with the increasing of temperature from 240 to 300 K. The desorption rate constants (kdes) were also found to increase slightly with the enhancement of temperature. The empirical formula between the uptake coefficients, desorption rate constants and temperature described in the form of Arrhenius expression were obtained. The activation energies for the heterogeneous reaction and desorption of COS on MgO were measured to be 11.02 +/- 0.34 kJ.mol-1 and 6.30 +/- 0.81 kJ.mol-1, respectively. The results demonstrate that the initial uptake of COS on MgO is mainly contributed by an adsorption process and the steady state uptake is due to a catalytic reaction. The environmental implication was also discussed.

  15. High-temperature-staged fluidized-bed combustion (HITS), bench scale experimental test program conducted during 1980. Final report

    SciTech Connect

    Anderson, R E; Jassowski, D M; Newton, R A; Rudnicki, M L

    1981-04-01

    An experimental program was conducted to evaluate the process feasibility of the first stage of the HITS two-stage coal combustion system. Tests were run in a small (12-in. ID) fluidized bed facility at the Energy Engineering Laboratory, Aerojet Energy Conversion Company, Sacramento, California. The first stage reactor was run with low (0.70%) and high (4.06%) sulfur coals with ash fusion temperatures of 2450/sup 0/ and 2220/sup 0/F, respectively. Limestone was used to scavenge the sulfur. The produced low-Btu gas was burned in a combustor. Bed temperature and inlet gas percent oxygen were varied in the course of testing. Key results are summarized as follows: the process was stable and readily controllable, and generated a free-flowing char product using coals with low (2220/sup 0/F) and high (2450/sup 0/F) ash fusion temperatures at bed temperatures of at least 1700/sup 0/ and 1800/sup 0/F, respectively; the gaseous product was found to have a total heating value of about 120 Btu/SCF at 1350/sup 0/F, and the practicality of cleaning the hot product gas and delivering it to the combustor was demonstrated; sulfur capture efficiencies above 80% were demonstrated for both low and high sulfur coals with a calcium/sulfur mole ratio of approximately two; gasification rates of about 5,000 SCF/ft/sup 2/-hr were obtained for coal input rates ranging from 40 to 135 lbm/hr, as required to maintain the desired bed temperatures; and the gaseous product yielded combustion temperatures in excess of 3000/sup 0/F when burned with preheated (900/sup 0/F) air. The above test results support the promise of the HITS system to provide a practical means of converting high sulfur coal to a clean gas for industrial applications. Sulfur capture, gas heating value, and gas production rate are all in the range required for an effective system. Planning is underway for additional testing of the system in the 12-in. fluid bed facility, including demonstration of the second stage char burnup

  16. 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.

  17. Heavy-ion-induced electronic desorption of gas from metals.

    PubMed

    Molvik, A W; Kollmus, H; Mahner, E; Covo, M Kireeff; Bellachioma, M C; Bender, M; Bieniosek, F M; Hedlund, E; Krämer, A; Kwan, J; Malyshev, O B; Prost, L; Seidl, P A; Westenskow, G; Westerberg, L

    2007-02-01

    During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE_{e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering. PMID:17358950

  18. Heavy-ion induced electronic desorption of gas from metals

    SciTech Connect

    Molvik, A W; Kollmus, H; Mahner, E; Covo, M K; Bellachioma, M C; Bender, M; Bieniosek, F M; Hedlund, E; Kramer, A; Kwan, J; Malyshev, O B; Prost, L; Seidl, P A; Westenskow, G; Westerberg, L

    2006-12-19

    During heavy ion operation in several particle accelerators world-wide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion induced gas desorption scales with the electronic energy loss (dE{sub e}/d/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

  19. Airborne laser-spark for ambient desorption/ionisation.

    PubMed

    Bierstedt, Andreas; Riedel, Jens

    2016-01-01

    A novel direct sampling ionisation scheme for ambient mass spectrometry is presented. Desorption and ionisation are achieved by a quasi-continuous laser induced plasma in air. Since there are no solid or liquid electrodes involved the ion source does not suffer from chemical interferences or fatigue originating from erosive burning or from electrode consumption. The overall plasma maintains electro-neutrality, minimising charge effects and accompanying long term drift of the charged particles trajectories. In the airborne plasma approach the ambient air not only serves as the plasma medium but at the same time also slows down the nascent ions via collisional cooling. Ionisation of the analyte molecules does not occur in the plasma itself but is induced by interaction with nascent ionic fragments, electrons and/or far ultraviolet photons in the plasma vicinity. At each individual air-spark an audible shockwave is formed, providing new reactive species, which expands concentrically and, thus, prevents direct contact of the analyte with the hot region inside the plasma itself. As a consequence the interaction volume between plasma and analyte does not exceed the threshold temperature for thermal dissociation or fragmentation. Experimentally this indirect ionisation scheme is demonstrated to be widely unspecific to the chemical nature of the analyte and to hardly result in any fragmentation of the studied molecules. A vast ensemble of different test analytes including polar and non-polar hydrocarbons, sugars, low mass active ingredients of pharmaceuticals as well as natural biomolecules in food samples directly out of their complex matrices could be shown to yield easily accessible yet meaningful spectra. Since the plasma medium is humid air, the chemical reaction mechanism of the ionisation is likely to be similar to other ambient ionisation techniques. Wir stellen hier eine neue Ionisationsmethode für die Umgebungsionisation (ambient ionisation) vor. Sowohl die

  20. Airborne laser-spark for ambient desorption/ionisation.

    PubMed

    Bierstedt, Andreas; Riedel, Jens

    2016-01-01

    A novel direct sampling ionisation scheme for ambient mass spectrometry is presented. Desorption and ionisation are achieved by a quasi-continuous laser induced plasma in air. Since there are no solid or liquid electrodes involved the ion source does not suffer from chemical interferences or fatigue originating from erosive burning or from electrode consumption. The overall plasma maintains electro-neutrality, minimising charge effects and accompanying long term drift of the charged particles trajectories. In the airborne plasma approach the ambient air not only serves as the plasma medium but at the same time also slows down the nascent ions via collisional cooling. Ionisation of the analyte molecules does not occur in the plasma itself but is induced by interaction with nascent ionic fragments, electrons and/or far ultraviolet photons in the plasma vicinity. At each individual air-spark an audible shockwave is formed, providing new reactive species, which expands concentrically and, thus, prevents direct contact of the analyte with the hot region inside the plasma itself. As a consequence the interaction volume between plasma and analyte does not exceed the threshold temperature for thermal dissociation or fragmentation. Experimentally this indirect ionisation scheme is demonstrated to be widely unspecific to the chemical nature of the analyte and to hardly result in any fragmentation of the studied molecules. A vast ensemble of different test analytes including polar and non-polar hydrocarbons, sugars, low mass active ingredients of pharmaceuticals as well as natural biomolecules in food samples directly out of their complex matrices could be shown to yield easily accessible yet meaningful spectra. Since the plasma medium is humid air, the chemical reaction mechanism of the ionisation is likely to be similar to other ambient ionisation techniques. Wir stellen hier eine neue Ionisationsmethode für die Umgebungsionisation (ambient ionisation) vor. Sowohl die

  1. 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

  2. Measurement of hydrogen solubility and desorption rate in V-4Cr-4Ti and liquid lithium-calcium alloys

    SciTech Connect

    Park, J.H.; Erck, R.; Park, E.T.

    1997-04-01

    Hydrogen solubility in V-4Cr-4Ti and liquid lithium-calcium was measured at a hydrogen pressure of 9.09 x 10{sup {minus}4} torr at temperatures between 250 and 700{degrees}C. Hydrogen solubility in V-4Cr-4Ti and liquid lithium decreased with temperature. The measured desorption rate of hydrogen in V-4Cr-4Ti is a thermally activated process; the activation energy is 0.067 eV. Oxygen-charged V-4Cr-4Ti specimens were also investigated to determine the effect of oxygen impurity on hydrogen solubility and desorption in the alloy. Oxygen in V-4Cr-4Ti increases hydrogen solubility and desorption kinetics. To determine the effect of a calcium oxide insulator coating on V-4Cr-4Ti, hydrogen solubility in lithium-calcium alloys that contained 0-8.0 percent calcium was also measured. The distribution ratio R of hydrogen between liquid lithium or lithium-calcium and V-4Cr-4Ti increased as temperature decreased (R {approx} 10 and 100 at 700 and 250{degrees}C, respectively). However at <267{degrees}C, solubility data could not be obtained by this method because of the slow kinetics of hydrogen permeation through the vanadium alloy.

  3. 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.

  4. 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-μ-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.

  5. Tuning the hydrogen desorption of Mg(BH4)2 through Zn alloying

    NASA Astrophysics Data System (ADS)

    Harrison, D.; Thonhauser, T.

    2014-09-01

    We study the effect of Zn alloying on the hydrogen desorption properties of Mg(BH4)2 using ab initio simulations. In particular, we investigate formation/reaction enthalpies/entropies for a number of compounds and reactions at a wide range of temperatures and Zn concentrations in Mg1-xZnx(BH4)2. Our results show that the thermodynamic stability of the resulting material can be significantly lowered through Zn alloying. We find, e.g., that the solid solution Mg2/3Zn1/3(BH4)2 has a reaction enthalpy for the complete hydrogen desorption of only 25.3 kJ/mol H2—a lowering of 15 kJ/mol H2 compared to the pure phase and a corresponding lowering in critical temperature of 123 K. In addition, we find that the enthalpy of mixing is rather small and show that the decrease in reaction enthalpy with Zn concentration is approximately linear.

  6. 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. )

    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.

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

    PubMed

    Scarpitta, S C; Harley, N H

    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 H2O 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 H2O 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. PMID:2398008

  8. Correlation of Chemisorption and Electronic Effects for Metal Oxide Interfaces: Transducing Principles for Temperature Programmed Gas Microsensors (Final Report)

    SciTech Connect

    S. Semancik; R. E. Cavicchi; D. L. DeVoe; T. J. McAvoy |

    2001-12-21

    This Final Report describes efforts and results for a 3-year DoE/OST-EMSP project centered at NIST. The multidisciplinary project investigated scientific and technical concepts critical for developing tunable, MEMS-based, gas and vapor microsensors that could be applied for monitoring the types of multiple analytes (and differing backgrounds) encountered at DoE waste sites. Micromachined ''microhotplate'' arrays were used as platforms for fabricating conductometric sensor prototypes, and as microscale research tools. Efficient microarray techniques were developed for locally depositing and then performance evaluating thin oxide films, in order to correlate gas sensing characteristics with properties including composition, microstructure, thickness and surface modification. This approach produced temperature-dependent databases on the sensitivities of sensing materials to varied analytes (in air) which enable application-specific tuning of microsensor arrays. Mechanistic studies on adsorb ate transient phenomena were conducted to better understand the ways in which rapid temperature programming schedules can be used to produce unique response signatures and increase information density in microsensor signals. Chemometric and neural network analyses were also employed in our studies for recognition and quantification of target analytes.

  9. Multivariate analysis of progressive thermal desorption coupled gas chromatography-mass spectrometry.

    SciTech Connect

    Van Benthem, Mark Hilary; Mowry, Curtis Dale; Kotula, Paul Gabriel; Borek, Theodore Thaddeus, III

    2010-09-01

    Thermal decomposition of poly dimethyl siloxane compounds, Sylgard{reg_sign} 184 and 186, were examined using thermal desorption coupled gas chromatography-mass spectrometry (TD/GC-MS) and multivariate analysis. This work describes a method of producing multiway data using a stepped thermal desorption. The technique involves sequentially heating a sample of the material of interest with subsequent analysis in a commercial GC/MS system. The decomposition chromatograms were analyzed using multivariate analysis tools including principal component analysis (PCA), factor rotation employing the varimax criterion, and multivariate curve resolution. The results of the analysis show seven components related to offgassing of various fractions of siloxanes that vary as a function of temperature. Thermal desorption coupled with gas chromatography-mass spectrometry (TD/GC-MS) is a powerful analytical technique for analyzing chemical mixtures. It has great potential in numerous analytic areas including materials analysis, sports medicine, in the detection of designer drugs; and biological research for metabolomics. Data analysis is complicated, far from automated and can result in high false positive or false negative rates. We have demonstrated a step-wise TD/GC-MS technique that removes more volatile compounds from a sample before extracting the less volatile compounds. This creates an additional dimension of separation before the GC column, while simultaneously generating three-way data. Sandia's proven multivariate analysis methods, when applied to these data, have several advantages over current commercial options. It also has demonstrated potential for success in finding and enabling identification of trace compounds. Several challenges remain, however, including understanding the sources of noise in the data, outlier detection, improving the data pretreatment and analysis methods, developing a software tool for ease of use by the chemist, and demonstrating our belief that

  10. Spreading of lithium on a stainless steel surface at room temperature

    DOE PAGES

    Skinner, C. H.; Capece, A. M.; Roszell, J. P.; Koel, B. E.

    2015-11-10

    Lithium conditioned plasma facing surfaces have lowered recycling and enhanced plasma performance on many fusion devices and liquid lithium plasma facing components are under consideration for future machines. A key factor in the performance of liquid lithium components is the wetting by lithium of its container. We have observed the surface spreading of lithium from a mm-scale particle to adjacent stainless steel surfaces using a scanning Auger microprobe that has elemental discrimination. Here, the spreading of lithium occurred at room temperature (when lithium is a solid) from one location at a speed of 0.62 μm/day under ultrahigh vacuum conditions. Separatemore » experiments using temperature programmed desorption (TPD) investigated bonding energetics between monolayer-scale films of lithium and stainless steel. While multilayer lithium desorption from stainless steel begins to occur just above 500 K (Edes = 1.54 eV), sub-monolayer Li desorption occurred in a TPD peak at 942 K (Edes = 2.52 eV) indicating more energetically favorable lithium-stainless steel bonding (in the absence of an oxidation layer) than lithium lithium bonding.« less

  11. Spreading of lithium on a stainless steel surface at room temperature

    SciTech Connect

    Skinner, C. H.; Capece, A. M.; Roszell, J. P.; Koel, B. E.

    2015-11-10

    Lithium conditioned plasma facing surfaces have lowered recycling and enhanced plasma performance on many fusion devices and liquid lithium plasma facing components are under consideration for future machines. A key factor in the performance of liquid lithium components is the wetting by lithium of its container. We have observed the surface spreading of lithium from a mm-scale particle to adjacent stainless steel surfaces using a scanning Auger microprobe that has elemental discrimination. Here, the spreading of lithium occurred at room temperature (when lithium is a solid) from one location at a speed of 0.62 μm/day under ultrahigh vacuum conditions. Separate experiments using temperature programmed desorption (TPD) investigated bonding energetics between monolayer-scale films of lithium and stainless steel. While multilayer lithium desorption from stainless steel begins to occur just above 500 K (Edes = 1.54 eV), sub-monolayer Li desorption occurred in a TPD peak at 942 K (Edes = 2.52 eV) indicating more energetically favorable lithium-stainless steel bonding (in the absence of an oxidation layer) than lithium lithium bonding.

  12. Experimental study of water desorption isotherms and thin-layer convective drying kinetics of bay laurel leaves

    NASA Astrophysics Data System (ADS)

    Ghnimi, Thouraya; Hassini, Lamine; Bagane, Mohamed

    2016-02-01

    The aim of this work is to determine the desorption isotherms and the drying kinetics of bay laurel leaves (Laurus Nobilis L.). The desorption isotherms were performed at three temperature levels: 50, 60 and 70 °C and at water activity ranging from 0.057 to 0.88 using the statistic gravimetric method. Five sorption models were used to fit desorption experimental isotherm data. It was found that Kuhn model offers the best fitting of experimental moisture isotherms in the mentioned investigated ranges of temperature and water activity. The Net isosteric heat of water desorption was evaluated using The Clausius-Clapeyron equation and was then best correlated to equilibrium moisture content by the empirical Tsami's equation. Thin layer convective drying curves of bay laurel leaves were obtained for temperatures of 45, 50, 60 and 70 °C, relative humidity of 5, 15, 30 and 45 % and air velocities of 1, 1.5 and 2 m/s. A non linear regression procedure of Levenberg-Marquardt was used to fit drying curves with five semi empirical mathematical models available in the literature, The R2 and χ2 were used to evaluate the goodness of fit of models to data. Based on the experimental drying curves the drying characteristic curve (DCC) has been established and fitted with a third degree polynomial function. It was found that the Midilli Kucuk model was the best semi-empirical model describing thin layer drying kinetics of bay laurel leaves. The bay laurel leaves effective moisture diffusivity and activation energy were also identified.

  13. LASER DESORPTION IONIZATION OF ULTRAFINE AEROSOL PARTICLES. (R823980)

    EPA Science Inventory

    On-line analysis of ultrafine aerosol particle in the 12 to 150 nm size range is performed by
    laser desorption/ionization. Particles are size selected with a differential mobility analyzer and then
    sent into a linear time-of-flight mass spectrometer where they are ablated w...

  14. Quantitative matrix-assisted laser desorption/ionization mass spectrometry

    PubMed Central

    Roder, Heinrich; Hunsucker, Stephen W.

    2008-01-01

    This review summarizes the essential characteristics of matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF MS), especially as they relate to its applications in quantitative analysis. Approaches to quantification by MALDI-TOF MS are presented and published applications are critically reviewed. PMID:19106161

  15. 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 ...

  16. 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...

  17. Desorption electrospray ionization mass spectrometry of intact bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desorption electrospray ionization (DESI) mass spectrometry (MS) was used to differentiate 7 bacterial species based on their measured DESI-mass spectral profile. Both Gram positive and Gram negative bacteria were tested and included Escherichia coli, Staphyloccocus aureus, Enterococcus sp., Bordete...

  18. Desorption electrospray ionization-mass spectrometry of proteins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the detection of proteins ranging in molecular mass from 12 to 66 kDa. Proteins were uniformly deposited on a solid surface without pretreatment and analyzed with a DESI source coupled to a quadrupole ion trap mass spec...

  19. 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...

  20. LASER DESORPTION IONIZATION OF SIZE RESOLVED LIQUID MICRODROPLETS. (R823980)

    EPA Science Inventory

    Mass spectra of single micrometer-size glycerol droplets containing organic and inorganic analytes were obtained by on-line laser desorption ionization. Aerosol droplets entered the mass spectrometer through an inlet where they were detected by light scattering of a continuous la...

  1. 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.

  2. 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 ...

  3. SITE TECHNOLOGY CAPSULE: CLEAN BERKSHIRES, INC. THERMAL DESORPTION SYSTEM

    EPA Science Inventory

    The thermal desorption process devised by Clean Berkshires, Inc., works by vaporizing the organic contaminants from the soil with heat, isolating the contaminant! in a gas stream, and then destroying them in a high efficiency afterburner. The processed solids are either replaced ...

  4. 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...

  5. Reductive desorption of thiolate from monolayer protected gold clusters.

    PubMed

    Quinn, Bernadette M; Kontturi, Kyösti

    2004-06-16

    The "electrochemical potential window" of monolayer-protected gold cluster (MPC) nanoelectrodes is probed where the electrified liquid-liquid interface is used as the detector. The first observation of the reductive desorption of thiolate at negative MPC core charge is reported.

  6. Adsorption and desorption kinetics of carbofuran in acid soils.

    PubMed

    Bermúdez-Couso, Alipio; Fernández-Calviño, David; Pateiro-Moure, Miriam; Nóvoa-Muñoz, Juan Carlos; Simal-Gándara, Jesús; Arias-Estévez, Manuel

    2011-06-15

    Carbofuran adsorption and desorption were investigated in batch and stirred flow chamber (SFC) tests. The carbofuran adsorption capacity of the soils was found to be low and strongly dependent on their clay and organic carbon contents. Carbofuran sorption was due mainly (>80%) to fast adsorption processes governed by intraparticle diffusion. The adsorption kinetic constant for the pesticide ranged from 0.047 to 0.195 min(-1) and was highly correlated with constant n in the Freundlich equation (r=0.965, P<0.05). Batch tests showed carbofuran desorption to be highly variable and negatively correlated with eCEC and the clay content. The SFC tests showed that soil organic carbon (C) plays a key role in the irreversibility of carbofuran adsorption. Carbofuran desorption increased rapidly at C contents below 4%. The desorption kinetic constant for the compound (0.086-0.195 min(-1)) was generally higher than its adsorption kinetic constant; therefore, carbofuran is more rapidly desorbed than it is adsorbed in soil.

  7. Permeability changes in coal resulting from gas desorption

    SciTech Connect

    Levine, J.R.; Johnson, P.M.

    1992-01-01

    Research continued on the study of coal permeability and gas desorption. This quarter, most of the effort involved identifying problems with the microbalance and then getting it repaired. Measurement of the amount of gas adsorbed with the microbalance involved corrections for the buoyancy change with pressure and several experiments with helium were made to determine this correction.

  8. 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.

  9. Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route

    NASA Astrophysics Data System (ADS)

    Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

    2013-09-01

    Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@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-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance.Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed

  10. 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...

  11. 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.

  12. Analysis and optimization of carbon nanotubes and graphene sensors based on adsorption-desorption kinetics

    NASA Astrophysics Data System (ADS)

    Liang, Sang-Zi; Chen, Gugang; Harutyunyan, Avetik R.; Cole, Milton W.; Sofo, Jorge O.

    2013-12-01

    Single-walled carbon nanotubes mats and graphene have shown great potential as gas sensors. We analyze NO adsorption/sensing experiments with the kinetic Langmuir model adapted to include adsorption sites from which the molecule does not desorb. The model reproduces the available experimental data. Its fitting parameters provide information on the microscopic phenomena governing adsorption, and variation of these parameters allows the optimization of the sensitivity, detection limit, and time response of the sensors. The result reveals an optimal operating temperature before thermal desorption becomes dominant at high temperature, the potential improvement of selectivity by tuning the gate voltage in a field effect transistor configuration, and quantifies the benefits of reducing the density of defects in the sensing materials.

  13. Investigation of Cell Surfaces using Microplasma-Assisted Desorption/Ionization Mass Spectroscopy

    NASA Astrophysics Data System (ADS)

    Symonds, Joshua; Sun, Lan; Fernández, Facundo; Orlando, Thomas

    2008-10-01

    Low-temperature, atmospheric pressure microplasmas have been developed for a wide array of uses. We have investigated one type of these devices, a Microhollow Cathode Discharge (MHCD) for desorbing and ionizing samples to be analyzed with standard mass spectroscopy techniques. Our work includes the development and use of MHCD's to analyze solid and liquid phase samples, with particular attention given to biologically-relevant substances. The goal of this line of research is to investigate, without causing undue fragmentation, the compounds present on and within cell membranes. By varying the properties of the plasma, including electron temperature, plasma density, and the plasma's interactions with the sample, we seek to investigate the role of different plasma components in the desorption/ionization events. Specifically, we seek to determine whether the process is dominated by emitted electrons, high energy (VUV) photons, metastable particles, or a combination thereof.

  14. 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.

  15. Sorption and desorption characteristics of a packed bed of clay-CaCl{sub 2} desiccant particles

    SciTech Connect

    Tretiak, C.S.; Abdallah, N. Ben

    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)

  16. A possible answer to the mysterious non-detection of hydroxylamine in space: the thermal desorption mechanism

    NASA Astrophysics Data System (ADS)

    Jonusas, Mindaugas; Krim, Lahouari

    2016-06-01

    The presence of NH2OH, one of the main precursors in the formation of amino-acids, on dust grain mantles, may be the most obvious elucidation for the creation of large pre-biotic molecules in the interstellar medium. However, while many laboratory experimental studies, to simulate the icy grain chemistry in space, found that NH2OH molecules may be easily formed in solid phase with high abundances and then they should desorb, through a temperature-induced desorption into the gas phase, with the same high abundances; all the spatial observations conclude that NH2OH is not detected in gas phase within any of the explored astronomical sources. Such inconsistencies between laboratory experiment simulations and spatial observations lead our investigations towards this experimental study to see if there is any chemical transformation of NH2OH, occurring in the solid phase before the desorption processes of NH2OH from the mantle of interstellar icy grains. Our experimental results show that the heating of NH2OH-H2O ices lead to a decomposition of NH2OH into HNO, NH3 and O2, even before reaching its desorption temperature. We show through this work that the NH2OH non-detection from previous examined astronomical sources could mainly due to its high reactivity in solid phase on the icy interstellar grains.

  17. Mechanisms of H2O desorption from amorphous solid water by 157-nm irradiation: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    DeSimone, Alice J.; Crowell, Vernon D.; Sherrill, C. David; Orlando, Thomas M.

    2013-10-01

    The photodesorption of water molecules from amorphous solid water (ASW) by 157-nm irradiation has been examined using resonance-enhanced multiphoton ionization. The rotational temperature has been determined, by comparison with simulations, to be 425 ± 75 K. The time-of-flight spectrum of H2O (v = 0) has been fit with a Maxwell-Boltzmann distribution with a translational temperature of 700 ± 200 K (0.12 ± 0.03 eV). H+ and OH+ fragment ions have been detected with non-resonant multiphoton ionization, indicating vibrationally excited parent water molecules with translational energies of 0.24 ± 0.08 eV. The cross section for water removal from ASW by 7.9-eV photons near 100 K is (6.9 ± 1.8) × 10-20 cm2 for >10 L H2O exposure. Electronic structure computations have also probed the excited states of water and the mechanisms of desorption. Calculated electron attachment and detachment densities show that exciton delocalization leads to a dipole reversal state in the first singlet excited state of a model system of hexagonal water ice. Ab Initio Molecular Dynamics simulations show possible desorption of a photo-excited water molecule from this cluster, though the non-hydrogen bonded OH bond is stretched significantly before desorption. Potential energy curves of this OH stretch in the electronic excited state show a barrier to dissociation, lending credence to the dipole reversal mechanism.

  18. Application of acid-activated Bauxsol for wastewater treatment with high phosphate concentration: Characterization, adsorption optimization, and desorption behaviors.

    PubMed

    Ye, Jie; Cong, Xiangna; Zhang, Panyue; Zeng, Guangming; Hoffmann, Erhard; Liu, Yang; Wu, Yan; Zhang, Haibo; Fang, Wei; Hahn, Hermann H

    2016-02-01

    Acid-activated Bauxsol was applied to treat wastewater with high phosphate concentration in a batch adsorption system in this paper. The effect of acid activation on the change of Bauxsol structure was systematically investigated. The mineralogical inhomogeneity and intensity of Bauxsol decreased after acid activation, and FeCl3·2H2O and Al(OH)3 became the dominant phases of acid-activated Bauxsol adsorption. Moreover, the BET surface area and total pore volume of Bauxsol increased after acid activation. Interaction of initial solution pH and adsorption temperature on phosphate adsorption onto acid-activated Bauxsol was investigated by using response surface methodology with central composite design. The maximum phosphate adsorption capacity of 192.94 mg g(-1) was achieved with an initial solution pH of 4.19 and an adsorption temperature of 52.18 °C, which increased by 7.61 times compared with that of Bauxsol (22.40 mg g(-1)), and was higher than other adsorbents. Furthermore, the desorption studies demonstrated that the acid-activated Bauxsol was successfully regenerated with 0.5 mol L(-1) HCl solution. The adsorption capacity and desorption efficiency of acid-activated Bauxsol maintained at 80.48% and 93.02% in the fifth adsorption-desorption cycle, respectively, suggesting that the acid-activated Bauxsol could be repeatedly used in wastewater treatment with high phosphate concentration. PMID:26606195

  19. Application of acid-activated Bauxsol for wastewater treatment with high phosphate concentration: Characterization, adsorption optimization, and desorption behaviors.

    PubMed

    Ye, Jie; Cong, Xiangna; Zhang, Panyue; Zeng, Guangming; Hoffmann, Erhard; Liu, Yang; Wu, Yan; Zhang, Haibo; Fang, Wei; Hahn, Hermann H

    2016-02-01

    Acid-activated Bauxsol was applied to treat wastewater with high phosphate concentration in a batch adsorption system in this paper. The effect of acid activation on the change of Bauxsol structure was systematically investigated. The mineralogical inhomogeneity and intensity of Bauxsol decreased after acid activation, and FeCl3·2H2O and Al(OH)3 became the dominant phases of acid-activated Bauxsol adsorption. Moreover, the BET surface area and total pore volume of Bauxsol increased after acid activation. Interaction of initial solution pH and adsorption temperature on phosphate adsorption onto acid-activated Bauxsol was investigated by using response surface methodology with central composite design. The maximum phosphate adsorption capacity of 192.94 mg g(-1) was achieved with an initial solution pH of 4.19 and an adsorption temperature of 52.18 °C, which increased by 7.61 times compared with that of Bauxsol (22.40 mg g(-1)), and was higher than other adsorbents. Furthermore, the desorption studies demonstrated that the acid-activated Bauxsol was successfully regenerated with 0.5 mol L(-1) HCl solution. The adsorption capacity and desorption efficiency of acid-activated Bauxsol maintained at 80.48% and 93.02% in the fifth adsorption-desorption cycle, respectively, suggesting that the acid-activated Bauxsol could be repeatedly used in wastewater treatment with high phosphate concentration.

  20. Fate of mercury in flue gas desulfurization gypsum determined by Temperature Programmed Decomposition and Sequential Chemical Extraction.

    PubMed

    Zhu, Zhenwu; Zhuo, Yuqun; Fan, Yaming; Wang, Zhipeng

    2016-05-01

    A considerable amount of Hg is retained in flue gas desulfurization (FGD) gypsum from Wet Flue Gas Desulfurization (WFGD) systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition (TPD) and Sequential Chemical Extraction (SCE) were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg2Cl2

  1. Terahertz Desorption Emission Spectroscopy (THz DES) - ‘ALMA in the Lab’

    NASA Astrophysics Data System (ADS)

    Emile Auriacombe, Olivier Bruno Jacques; Fraser, Helen; Ellison, Brian; Ioppolo, Sergio; Rea, Simon

    2016-06-01

    ALMA is revolutionising our scope to identify and locate molecules that have been desorbed from ices, particularly complex organic molecules (COMS), which provide a vital link between interstellar and prebiotic chemistry. Explaining the existence of these molecules in star-forming regions relies on an empirical understanding of the chemistry that underpins their formation:- do COMS form predominantly in the solid-phase and then desorb to the gas phase, or do only “smaller” species, radials or ions desorb and then undergo gas-phase chemical reactions to generate larger COMS?-are the rotational state populations in COMS only attributable to equilibrium chemistry, or could their formation mechanisms and desorption processes affect the rotational state occupancy of these molecules, thereby directly tying certain species to solid-state origins?We have developed a novel laboratory method - THz Desorption Emission Spectroscopy (THz-DES) that combines “traditional” laboratory astrophysics high-vacuum ice experiments with a sensitive high-spectral-resolution terahertz total-power heterodyne radiometer 1,2, partially mirroring the spectral range of ALMA band 7 (275- 373 GHz). Ices are grown in situ on a cold-plate, situated in a vacuum cell, then (thermally) desorbed. The sub-mm emission spectra of the resultant gas-phase molecules are detected as a function of time, temperature, or distance from the surface. Our first THz DES results will be shown for pure and binary ice systems including H2O, N2O and CH3OH. They show good correlation with established methods e.g. TPD, with the advantage of exploiting the molecular spectroscopy to unravel surface dynamics, state-occupancy, and unequivocal molecular identification, as well as concurrently measuring desorption barriers and molecular yields. We will extend our technique to a broader frequency range, enabling us to detect radical and ion desorption, to differentiate between A and E populations of CH3OH or ortho

  2. Terahertz Desorption Emission Spectroscopy (THz DES) – ‘ALMA in the Lab’

    NASA Astrophysics Data System (ADS)

    Emile Auriacombe, Olivier Bruno Jacques; Fraser, Helen; Ellison, Brian; Ioppolo, Sergio; Rea, Simon

    2016-06-01

    ALMA is revolutionising our scope to identify and locate molecules that have been desorbed from ices, particularly complex organic molecules (COMS), which provide a vital link between interstellar and prebiotic chemistry. Explaining the existence of these molecules in star-forming regions relies on an empirical understanding of the chemistry that underpins their formation:- do COMS form predominantly in the solid-phase and then desorb to the gas phase, or do only “smaller” species, radials or ions desorb and then undergo gas-phase chemical reactions to generate larger COMS?-are the rotational state populations in COMS only attributable to equilibrium chemistry, or could their formation mechanisms and desorption processes affect the rotational state occupancy of these molecules, thereby directly tying certain species to solid-state origins?We have developed a novel laboratory method - THz Desorption Emission Spectroscopy (THz-DES) that combines “traditional” laboratory astrophysics high-vacuum ice experiments with a sensitive high-spectral-resolution terahertz total-power heterodyne radiometer 1,2, partially mirroring the spectral range of ALMA band 7 (275– 373 GHz). Ices are grown in situ on a cold-plate, situated in a vacuum cell, then (thermally) desorbed. The sub-mm emission spectra of the resultant gas-phase molecules are detected as a function of time, temperature, or distance from the surface. Our first THz DES results will be shown for pure and binary ice systems including H2O, N2O and CH3OH. They show good correlation with established methods e.g. TPD, with the advantage of exploiting the molecular spectroscopy to unravel surface dynamics, state-occupancy, and unequivocal molecular identification, as well as concurrently measuring desorption barriers and molecular yields. We will extend our technique to a broader frequency range, enabling us to detect radical and ion desorption, to differentiate between A and E populations of CH3OH or ortho

  3. Simultaneous desorption behavior of M borohydrides and Mg2FeH6 reactive hydride composites (M = Mg, then Li, Na, K, Ca)

    NASA Astrophysics Data System (ADS)

    Chaudhary, Anna-Lisa; Li, Guanqiao; Matsuo, Motoaki; Orimo, Shin-ichi; Deledda, Stefano; Sørby, Magnus H.; Hauback, Bjørn C.; Pistidda, Claudio; Klassen, Thomas; Dornheim, Martin

    2015-08-01

    Combinations of complex metal borohydrides ball milled with the transition metal complex hydride, Mg2FeH6, are analysed and compared. Initially, the Reactive Hydride Composite (RHC) of Mg2+ cation mixtures of Mg2FeH6 and γ-Mg(BH4)2 is combined in a range of molar ratios and heated to a maximum of 450 °C. For the molar ratio of 6 Mg2FeH6 + Mg(BH4)2, simultaneous desorption of the two hydrides occurred, which resulted in a single event of hydrogen release. This single step desorption occurred at temperatures between those of Mg2FeH6 and γ-Mg(BH4)2. Keeping this anionic ratio constant, the desorption behavior of four other borohydrides, Li-, Na-, K-, and Ca-borohydrides was studied by using materials ball milled with Mg2FeH6 applying the same milling parameters. The mixtures containing Mg-, Li-, and Ca-borohydrides also released hydrogen in a single event. The Mass Spectrometry (MS) results show a double step reaction within a narrow temperature range for both the Na- and K-borohydride mixtures. This phenomenon, observed for the RHC systems at the same anionic ratio with all five light metal borohydride mixtures, can be described as simultaneous hydrogen desorption within a narrow temperature range centered around 300 °C.

  4. F sorption/desorption on two soils and on different by-products and waste materials.

    PubMed

    Quintáns-Fondo, Ana; Ferreira-Coelho, Gustavo; Paradelo-Núñez, Remigio; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel; Fernández-Sanjurjo, María J; Álvarez-Rodríguez, Esperanza; Núñez-Delgado, Avelino

    2016-07-01

    We used batch-type experiments to study F sorption/desorption on a forest soil, a vineyard soil, pyritic material, granitic material, finely and coarsely ground mussel shell, mussel shell calcination ash, oak wood ash, pine-sawdust, slate processing fines, and three different mixtures that included three components: sewage sludge, mussel shell ash, and calcined mussel shell or pine wood ash. The three waste mixtures, forest soil, pyritic material, and shell ash showed high sorption capacity (73-91 % of added F) and low desorption, even when 100 mg F L(-1) was added. All these materials (and to a lower extent wood ash) could be useful to remove F from polluted media (as certain soils, dumping sites, and contaminated waters). The vineyard soil, the granitic material, mussel shell, slate fines, and pine-sawdust were less effective in F removal. In most cases, sorption data fitted better to the Freundlich than to the Langmuir equation. These results can be useful to program the correct management of the soils, by-products, and waste materials assayed, mostly in situations where F concentrations are excessive and F removal should be promoted. PMID:27250088

  5. Laser desorption time-of-flight mass spectrometry of vacuum UV photo-processed methanol ice

    NASA Astrophysics Data System (ADS)

    Paardekooper, D. M.; Bossa, J.-B.; Linnartz, H.

    2016-07-01

    Context. Methanol in the interstellar medium mainly forms upon sequential hydrogenation of solid CO. With typical abundances of up to 15% (with respect to water) it is an important constituent of interstellar ices where it is considered as a precursor in the formation of large and complex organic molecules (COMs), e.g. upon vacuum UV (VUV) photo-processing or exposure to cosmic rays. Aims: This study aims at detecting novel complex organic molecules formed during the VUV photo-processing of methanol ice in the laboratory using a technique more sensitive than regular surface diagnostic tools. In addition, the formation kinetics of the main photo-products of methanol are unravelled for an astronomically relevant temperature (20 K) and radiation dose. Methods: The VUV photo-processing of CH3OH ice is studied by applying laser desorption post-ionisation time-of-flight mass spectrometry (LDPI TOF-MS), and analysed by combining molecule-specific fragmentation and desorption features. Results: The mass spectra correspond to fragment ions originating from a number of previously recorded molecules and from new COMs, such as the series (CO)xH, with x = 3 and y < 3x-1, to which prebiotic glycerin belongs. The formation of these large COMs has not been reported in earlier photolysis studies and suggests that such complex species may form in the solid state under interstellar conditions.

  6. Diffusion barriers in the kinetics of water vapor adsorption/desorption on activated carbons

    SciTech Connect

    Harding, A.W.; Foley, N.J.; Thomas, K.M.; Norman, P.R.; Francis, D.C.

    1998-07-07

    The adsorption of water vapor on a highly microporous coconut-shell-derived carbon and a mesoporous wood-derived carbon was studied. These carbons were chosen as they had markedly different porous structures. The adsorption and desorption characteristics of water vapor on the activated carbons were investigated over the relative pressure range p/p{degree} = 0--0.9 for temperatures in the range 285--313 K in a static water vapor system. The adsorption isotherms were analyzed using the Dubinin-Serpinski equation, and this provided an assessment of the polarity of the carbons. The kinetics of water vapor adsorption and desorption were studied with different amounts of preadsorbed water for set changes in pressure relative to the saturated vapor pressure (p/p{degree}). The adsorption kinetics for each relative pressure step were compared and used to calculate the activation energies for the vapor pressure increments. The kinetic results are discussed in relation to their relative position on the equilibrium isotherm and the adsorption mechanism of water vapor on activated carbons.

  7. Visualization and Measurement of Adsorption/Desorption Process of Ethanol in Activated Carbon Adsorber

    NASA Astrophysics Data System (ADS)

    Asano, Hitoshi; Murata, Kenta; Takenaka, Nobuyuki; Saito, Yasushi

    Adsorption refrigerator is one of the efficient tools for waste heat recovery, because the system is driven by heat at relative low temperature. However, the coefficient of performance is low due to its batch operation and the heat capacity of the adsorber. In order to improve the performance, it is important to optimize the configuration to minimize the amount of driving heat, and to clarify adsorption/desorption phenomena in transient conditions. Neutron radiography was applied to visualize and measure the adsorption amount distribution in an adsorber. The visualization experiments had been performed at the neutron radiography facility of E-2 port of Kyoto University Research Reactor. Activated carbon and ethanol were used as the adsorbent and refrigerant. From the acquired radiographs, adsorption amount was quantitatively measured by applying the umbra method using a checkered neutron absorber with boron powder. Then, transient adsorption and desorption processes of a rectangular adsorber with 84 mm in width, 50 mm in height and 20 mm in depth were visualized. As the result, the effect of fins in the adsorbent layer on the adsorption amount distribution was clearly visualized.

  8. Laser desorption mass spectrometry and small angle neutron scattering of heavy fossil materials

    SciTech Connect

    Hunt, J.E.; Winans, R.E.; Thiyagarajan, P.

    1997-09-01

    The determination of the structural building blocks and the molecular weight range of heavy hydrocarbon materials is of crucial importance in research on their reactivity and for their processing. The chemically and physically heterogenous nature of heavy hydrocarbon materials, such as coals, heavy petroleum fractions, and residues, dictates that their structure and reactivity patterns be complicated. The problem is further complicated by the fact that the molecular structure and molecular weight distribution of these materials is not dependent on a single molecule, but on a complex mixture of molecules which vary among coals and heavy petroleum samples. Laser Desorption mass spectrometry (LDMS) is emerging as a technique for molecular weight determination having found widespread use in biological polymer research, but is still a relatively new technique in the fossil fuel area. Small angle neutron scattering (SANS) provides information on the size and shape of heavy fossil materials. SANS offers the advantages of high penetration power even in thick cells at high temperatures and high contrast for hydrocarbon systems dispersed in deuterated solvents. LDMS coupled with time of flight has the advantages of high sensitivity and transmission and high mass range. We have used LDMS to examine various heavy fossil-derived materials including: long chain hydrocarbons, asphaltenes from petroleum vacuum resids, and coals. This paper describes the application of laser desorption and small angle neutron scattering techniques to the analysis of components in coals, petroleum resids and unsaturated polymers.

  9. Kinetics of desorption of hexane from the microporous metal organic framework RPM-1

    SciTech Connect

    Smith, M.; Culp, J. T.; Bittner, E.; Parker, B.; Li, J.; Bockrath, B. C.

    2007-03-06

    The kinetics of desorption of hexane from the microporous metal framework RPM-1 has been studied using a pulse mass analyzer. In this method a small sample of organic liquid was injected into a heated carrier gas that passes through a packed bed of adsorbent. The change in mass of the bed with time was observed following the adsorption of the pulse. RPM-1 is a microporous material of the general formula [M3(bpdc)3(bpy)] · 4DMF · H2O, where M is either Co or Zn, bpdc is biphenyl dicarboxylate and bpy is 4,4'-bipyridine. The pores are channels of larger supercages (11 × 11 × 5 Å) connected by smaller windows of approximately 8 Å diameter. The desorption of hexane was well represented by a combination of two first order processes. Activation energies determined for the two processes over a temperature range of 373–473 K were 56 and 63 kJ/mol for RPM-1 (Co). The two activation energies are similar to isosteric heats of adsorption measured independently in earlier work at corresponding coverages. Similar values were found for RPM-1 (Zn). The pulse mass analyzer was found to be an effective way to investigate the dynamics of adsorption processes.

  10. Adsorption / Desorption Behavior of Water Vapor in an Adsorbent Desiccant Rotor

    NASA Astrophysics Data System (ADS)

    Tsujiguchi, Takuya; Kodama, Akio

    Adsorption / desorption behavior of water vapor onto desiccant rotor has been investigated to improve the desiccant cooling system by means of computer simulation. In this paper, we paid attention to the relationship between the equilibrium amount of water adsorbed onto the desiccant material and the relative humidity, that is adsorption isotherm as a principal characteristic feature of adsorbent. Considering actual adsorbents, five types of adsorption isotherms were assumed to clarify the influence of adsorption isotherm on the dehumidifying performance. After the investigation on the influences of some operating conditions on the dehumidifying performance at each selected adsorption isotherm, it was found that higher dehumidifying performance and reduction of length of desiccant rotor could be achieved by selecting appropriate adsorption isotherm. It was also predicted that S-shaped adsorption isotherm which is raised sharply at relative humidity around 15 % could produce the lowest air humidity at regeneration air temperature 80 °C. Moreover influence of the intraparticle diffusion coefficient which significantly influence on the adsorption / desorption rate was discussed choosing two adsorption isotherm from the above five isotherms. It seems that effective range of the intraparticle diffusion coefficient for the significant improvement of the dehumidifying performance was strongly influenced by the shape of adsorption isotherm.

  11. 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.

  12. Desorption characteristics of four polyimide sorbent materials using supercritical carbon dioxide and thermal methods

    SciTech Connect

    Raymer, J.H.; Pellizzari, E.D.; Cooper, S.D.

    1987-09-01

    /sup 14/C-Labeled 1,2,3,4,5,6-hexachlorocyclohexane, hexachlorobiphenyl, anthracene, and parathion were used to study the desorption of four polyimide-based sorbent materials using both supercritical carbon dioxide and thermal methods. Supercritical fluid desorption was found to be superior to thermal desorption. Both types of desorption were more difficult from the polyimides than from Tenax-GC used in previous work. This work helps to define the applicability of supercritical desorption of polyimides. The identities of the compounds desorbed with supercritical CO/sub 2/ were verified by using thin-layer chromatography and mass spectrometry. Results were compared to those from Tenax-GC studies.

  13. 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

    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.

  14. Spatially resolved thermal desorption/ionization coupled with mass spectrometry

    DOEpatents

    Jesse, Stephen; Van Berkel, Gary J; Ovchinnikova, Olga S

    2013-02-26

    A system and method for sub-micron analysis of a chemical composition of a specimen are described. The method includes providing a specimen for evaluation and a thermal desorption probe, thermally desorbing an analyte from a target site of said specimen using the thermally active tip to form a gaseous analyte, ionizing the gaseous analyte to form an ionized analyte, and analyzing a chemical composition of the ionized analyte. The thermally desorbing step can include heating said thermally active tip to above 200.degree. C., and positioning the target site and the thermally active tip such that the heating step forms the gaseous analyte. The thermal desorption probe can include a thermally active tip extending from a cantilever body and an apex of the thermally active tip can have a radius of 250 nm or less.

  15. Collisional desorption of NO by fast O atoms

    NASA Technical Reports Server (NTRS)

    Sonnenfroh, David M.; Caledonia, George E.

    1993-01-01

    Surface-adsorbed NO figures largely in the mechanism that produces visible glow around spacecraft in low Earth orbit (LEO). In view of the potential interference to optical observations such a glow represents, we have investigated the collision-induced desorption of NO from Al, Ni, and Z306 Chemglaze-coated surfaces at 96 K by hyperthermal (8 km/s) oxygen atoms. The removal of surface NO was followed by the monitoring of the visible fluorescence of electronically excited NO2 produced through the surface-mediated reaction O + NO. A variability in collisional desorption rate with material was observed. The limited data suggest a removal efficiency of 4 to 8% of the impinging O atom flux. Implications for the atmospheric scouring of contaminants from external surfaces of LEO spacecraft are discussed.

  16. Laser desorption in an ion trap mass spectrometer

    SciTech Connect

    Eiden, G.C.; Cisper, M.E.; Alexander, M.L.; Hemberger, P.H.; Nogar, N.S.

    1993-02-01

    Laser desorption in a ion-trap mass spectrometer shows significant promise for both qualitative and trace analysis. Several aspects of this methodology are discussed in this work. We previously demonstrated the generation of both negative and positive ions by laser desorption directly within a quadrupole ion trap. In the present work, we explore various combinations of d.c., r.f., and time-varying fields in order to optimize laser generated signals. In addition, we report on the application of this method to analyze samples containing compounds such as amines, metal complexes, carbon clusters, and polynuclear aromatic hydrocarbons. In some cases the ability to rapidly switch between positive and negative ion modes provides sufficient specificity to distinguish different compounds of a mixture with a single stage of mass spectrometry. In other experiments, we combined intensity variation studies with tandem mass spectrometry experiments and positive and negative ion detection to further enhance specificity.

  17. Modeling of a Novel Desorption Cycle by Dielectric Heating

    NASA Astrophysics Data System (ADS)

    Kumja, M.; Ng, K. C.; Yap, C.; Yanagi, H.; Koyama, S.; Saha, B. B.; Chakraborty, A.

    The paper presents an adsorption cycle for cooling using the dielectric heating method for the regeneration process. Conventional adsorption (AD) chillers employs thermally driven processes for desorption and adsorption where the thermal resistances are high, resulting in a relatively low chiller COP. In this paper, dielectric heating is used to irradiate where the microwave power vibrates the dipole structure of the molecules. Owing to the direct method of energy delivery, the heating process is thus efficient, contributing to an increase in the chiller performance and the COPs. We present the modeling and simulations of the adsorption-desorption cycle in an AD chiller, demonstrating a significant improvement in chiller performance by as much as three folds.

  18. 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.

  19. Study on adsorption and desorption of ammonia on graphene

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengwei; Zhang, Xinfang; Luo, Wei; Yang, Hang; He, Yanlan; Liu, Yixing; Zhang, Xueao; Peng, Gang

    2015-09-01

    The gas sensor based on pristine graphene with conductance type was studied theoretically and experimentally. The time response of conductance measurements showed a quickly and largely increased conductivity when the sensor was exposed to ammonia gas produced by a bubble system of ammonia water. However, the desorption process in vacuum took more than 1 h which indicated that there was a larger number of transferred carriers and a strong adsorption force between ammonia and graphene. The desorption time could be greatly shortened down to about 2 min by adding the flow of water-vapor-enriched air at the beginning of the recovery stage which had been confirmed as a rapid and high-efficiency desorption process. Moreover, the optimum geometries, adsorption energies, and the charge transfer number of the composite systems were studied with first-principle calculations. However, the theoretical results showed that the adsorption energy between NH3 and graphene was too small to fit for the experimental phenomenon, and there were few charges transferred between graphene and NH3 molecules, which was completely different from the experiment measurement. The adsorption energy between NH4 and graphene increased stage by stage which showed NH4 was a strong donor. The calculation suggested that H2O molecule could help a quick desorption of NH4 from graphene by converting NH4 to NH3 or (NH3)n(H2O)m groups, which was consistent with the experimental results. This study demonstrates that the ammonia gas produced by a bubble system of ammonia water is mainly ammonium groups of NH3 and NH4, and the NH4 moleculars are ideal candidates for the molecular doping of graphene while the interaction between graphene and the NH3 moleculars is weak.

  20. Study on adsorption and desorption of ammonia on graphene.

    PubMed

    Zhang, Zhengwei; Zhang, Xinfang; Luo, Wei; Yang, Hang; He, Yanlan; Liu, Yixing; Zhang, Xueao; Peng, Gang

    2015-12-01

    The gas sensor based on pristine graphene with conductance type was studied theoretically and experimentally. The time response of conductance measurements showed a quickly and largely increased conductivity when the sensor was exposed to ammonia gas produced by a bubble system of ammonia water. However, the desorption process in vacuum took more than 1 h which indicated that there was a larger number of transferred carriers and a strong adsorption force between ammonia and graphene. The desorption time could be greatly shortened down to about 2 min by adding the flow of water-vapor-enriched air at the beginning of the recovery stage which had been confirmed as a rapid and high-efficiency desorption process. Moreover, the optimum geometries, adsorption energies, and the charge transfer number of the composite systems were studied with first-principle calculations. However, the theoretical results showed that the adsorption energy between NH3 and graphene was too small to fit for the experimental phenomenon, and there were few charges transferred between graphene and NH3 molecules, which was completely different from the experiment measurement. The adsorption energy between NH4 and graphene increased stage by stage which showed NH4 was a strong donor. The calculation suggested that H2O molecule could help a quick desorption of NH4 from graphene by converting NH4 to NH3 or (NH3)n(H2O)m groups, which was consistent with the experimental results. This study demonstrates that the ammonia gas produced by a bubble system of ammonia water is mainly ammonium groups of NH3 and NH4, and the NH4 moleculars are ideal candidates for the molecular doping of graphene while the interaction between graphene and the NH3 moleculars is weak.