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

    PubMed

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

    2006-11-21

    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.

  3. 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.

  4. 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.

  5. 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.

  6. Investigation of potential alternative hydrogen carrier, Mg supported zeolite with temperature programmed desorption of NH3.

    PubMed

    Cho, Sung June; Kim, Tak Hee; Jang, Young Bae; Lee, Jun

    2007-11-01

    Magnesium ion exchanged zeolite A was subject to the measurement of the temperature programmed desorption of NH3 to explore the possibility of the potential hydrogen carrier. The result suggested that the Mg supported NaA zeolite released a significant amount of ammonia corresponding to 1.4 Hwt% hydrogen at around 373 K. Under the same condition after the NH3 adsorption at ambient temperature, the MgCl2 sample released 1.0 Hwt% hydrogen at around 340 K. The present work suggests that the Mg supported zeolite can also be utilized as hydrogen carrier.

  7. 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.

  8. Analysis of the adsorption state and desorption kinetics of NO(2) over Fe-zeolite catalyst by FT-IR and temperature-programmed desorption.

    PubMed

    Iwasaki, Masaoki; Shinjoh, Hirofumi

    2010-03-14

    States of NO(2) adsorption and kinetics of NO(2) desorption over a Fe-loaded ZSM-5 type zeolite were investigated using Fourier transform infrared (FT-IR) spectroscopy and temperature-programmed desorption (TPD). The FT-IR spectra in NO(2)/N(2) flows showed that several adsorption species (NO(2), nitrite, nitrate, and NO(+)) existed; except for NO(2), these were considered to be formed via NO(2) dimerization and disproportionation reactions. The TPD spectra showed two distinct peaks, a low-temperature (LT) peak that can be assigned to weakly adsorbed NO(x) in the zeolite channel and a high-temperature (HT) peak that can be assigned to chemisorbed NO(x) bonded to ion-exchanged Fe sites. By varying flow rates and heating rates in TPD measurements, the peak maximum temperatures in the both peaks were found to be constant with the former, but shifted to higher temperatures with the latter; this suggests that desorption is not controlled by an adsorption/desorption equilibrium, i.e., in the no-readsorption limit. Furthermore, it was found that desorption at both LT and HT peaks proceeds at second order; this implies that the reverse reaction of NO(2) dimerization and disproportionation and/or some sort of lateral interaction between NO(2) molecules might be occurring. The desorption energies and the pre-exponential factors were estimated to be 67 +/- 1 kJ mol(-1) and 10(5.5+/-0.2) s(-1) for the LT peak and 138 +/- 4 kJ mol(-1) and 10(9.8+/-0.3) s(-1) for the HT peak. These values show that interaction strengths between adsorbed NO(x) and Fe sites are relatively large.

  9. Stabilization of mercury over Mn-based oxides: Speciation and reactivity by temperature programmed desorption analysis.

    PubMed

    Xu, Haomiao; Ma, Yongpeng; Huang, Wenjun; Mei, Jian; Zhao, Songjian; Qu, Zan; Yan, Naiqiang

    2017-01-05

    Mercury temperature-programmed desorption (Hg-TPD) method was employed to clarify mercury species over Mn-based oxides. The elemental mercury (Hg(0)) removal mechanism over MnOx was ascribed to chemical-adsorption. HgO was the primary mercury chemical compound adsorbed on the surface of MnOx. Rare earth element (Ce), main group element (Sn) and transition metal elements (Zr and Fe) were chosen for the modification of MnOx. Hg-TPD results indicated that the binding strength of mercury on these binary oxides followed the order of Sn-MnOxdesorption were calculated and they were 64.34, 101.85, 46.32, 117.14, and 106.92eV corresponding to MnOx, Ce-MnOx, Sn-MnOx, Zr-MnOx and Fe-MnOx, respectively. Sn-MnOx had a weak bond of mercury (Hg-O), while Zr-MnOx had a strong bond (HgO). Ce-MnOx and Fe-MnOx had similar bonds compared with pure MnOx. Moreover, the effects of SO2 and NO were investigated based on Hg-TPD analysis. SO2 had a poison effect on Hg(0) removal, and the weak bond of mercury can be easily destroyed by SO2. NO was favorable for Hg(0) removal, and the bond strength of mercury was enhanced.

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

    NASA Astrophysics Data System (ADS)

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

    1994-12-01

    Temperature programmed static secondary ion mass spectrometry (TPSSIMS) and temperature programmed desorption (TPD) have been used to study the kinetics of adsorption, dissociation, and desorption of NO on Rh(111). At 100 K, NO adsorption is molecular and proceeds via mobile precursor state kinetics with a high initial sticking probability. SSIMS indicates the presence of two distinct NO adsorption states, indicative of threefold adsorption at low coverage, and occupation of bridge sites at higher coverages. Three characteristic coverage regimes appear with respect to NO dissociation. At low coverages θNO<0.25 ML, NO dissociates completely at temperatures between 275 and 340 K. If we neglect lateral interactions and assume pure first order dissociation kinetics, we find effective values for the activation barrier and preexponential factor of 40±6 kJ/mol and 106±1 s-1 for the dissociation of 0.15-0.20 ML NO. However, if we assume that a NO molecule needs an ensemble of three to four vacant sites in order to dissociate, the preexponential factor and activation energy are ˜1011 s-1 and 65 kJ/mol, in better agreement with transition state theory expectations. The Nads and Oads dissociation products desorb as N2 and O2, respectively, with desorption parameters Edes=118±10 kJ/mol and νdes=1010.1±1.0 s-1 for N2 in the zero coverage limit. At higher coverages, the desorption kinetics of N2 is strongly influenced by the presence of coadsorbed oxygen. In the medium coverage range 0.25<θNO<0.50 ML, part of the NO desorbs molecularly, with an estimated desorption barrier of 113±10 kJ/mol and a preexponential of 1013.5±1.0 s-1. Dissociation of NO becomes progressively inhibited due to site blocking, the onset shifting from 275 K at 0.25 ML to 400 K, coinciding with the NO desorption temperature, at a coverage of 0.50 ML. The accumulation of nitrogen and oxygen atoms on the highly covered surface causes a destabilization of the nitrogen atoms, which results in an

  11. Catalytic reduction of CO with hydrogen sulfide. 4. Temperature-programmed desorption of methanethiol on anatase, rutile, and sulfided rutile

    SciTech Connect

    Beck, D.D.; White, J.M.; Ratcliffe, C.T.

    1986-07-03

    The interaction of methanethiol with anatase, rutile, and sulfided rutile was studied by temperature-programmed desorption. Dissociative adsorption occurs on rutile but is insignificant on anatase. Decomposition products are dominated by H/sub 2/ on rutile and by CH/sub 4/ on sulfided rutile. In both cases desorption occurs between 500 and 775 K. The 5- and 4-coordinate sites on the (110) face of rutile are proposed as the active sites for decomposition. The dominance of methane on a sulfided surface is attributed to the relatively large supply of highly mobile surface hydrogen atoms.

  12. Assessing sequestration of selected polycyclic aromatic hydrocarbons by use of adsorption modeling and temperature-programmed desorption.

    PubMed

    Abu, Abdul; Smith, Steve

    2005-10-01

    Sequestration of phenanthrene and pyrene was investigated in two soils--a sandy soil designated SBS and a silt-loam designated LHS--by combining long-term batch sorption studies with thermal desorption and pyrolysis of amended soil samples. The Polanyi-based adsorption volume and the adsorbed solute mass increased with aging for both soils, thus demonstrating the mechanism for observed sequestration. Despite rigorous thermal analysis, 30-62% (SBS sand) and 8-30% (LHS silt-loam) of phenanthrene could not be recovered after 30-270 days of sorption, with the increase in desorption resistance showing greater significance in SBS sand. For both soils, these values were 20-65% of adsorbed phenanthrene mass. Activation energies estimated from the temperature-programmed desorption (TPD) of sorbed phenanthrene at < or = 375 degrees C were 51-53 kJ/mol, consistent with values derived for desorption of organic compounds from humic materials. The activated first-order model fitting of observed TPD data supports the conclusion that the desorption-resistant fraction of phenanthrene has become sequestered onto condensed organic domains and requires temperatures exceeding 600 degrees C to be released. The work demonstrates the use of thermal analysis in complementing the Polanyi-based adsorption modeling approach for assessing the mechanistic basis for sequestration of organic contaminants in soils.

  13. 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.

  14. 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.

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

    SciTech Connect

    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 byproduct 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.

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

    DOE PAGES

    Kim, Boseong; Dohnalek, Zdenek; Szanyi, Janos; ...

    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

  17. 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.

  18. Dissociation energy for O2 release from gas-phase iron oxide clusters measured by temperature-programmed desorption experiments

    NASA Astrophysics Data System (ADS)

    Koyama, Kohei; Kudoh, Satoshi; Miyajima, Ken; Mafuné, Fumitaka

    2015-04-01

    Thermal dissociation of gas phase iron oxide cluster ions, FenOm+ (n = 2-6), was observed by mass spectrometry. The dissociation processes were investigated by temperature-programmed desorption (TPD) measurements for different sized clusters. Oxygen molecules were found to be released from the cluster ions. The threshold energy required for dissociation, determined by analyzing TPD, was compared with the energies obtained by experiments of collision-induced dissociation and by calculations of density functional theory. The agreement of the energies indicates that the oxygen atoms bonded to the terminal site of clusters are more readily released into the gas phase than those in the bridge site.

  19. 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.

  20. 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.

  1. 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

  2. CO adsorption on W(100) during temperature-programmed desorption: A combined density functional theory and kinetic Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Albao, Marvin A.; Padama, Allan Abraham B.

    2017-02-01

    Using a combined density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations, we study the adsorption at 800 K and subsequent desorption of CO on W(100) at higher temperatures. The resulting TPD profiles are known experimentally to exhibit three desorption peaks β1, β2, and β3 at 930 K, 1070 K, and 1375 K, respectively. Unlike more recent theoretical studies that propose that all three aforementioned peaks are molecularly rather than associatively desorbed, our KMC analyses are in support of the latter, since at 800 K dissociation is facile and that CO exists as dissociation fragments C and O. We show that these peaks arise from desorption from the same adsorption site but whose binding energy varies depending on local environment, that is, the presence of CO as well as dissociation fragments C and O nearby. Furthermore we show that several key parameters, such as desorption, dissociation and recombination barriers all play a key role in the TPD spectra-these parameter effectively controls not only the location of the TPD peaks but the shape and width of the desorption peaks as well. Moreover, our KMC simulations reveal that varying the heating rate shifts the peaks but leaves their shape intact.

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

    SciTech Connect

    Tewell, Craig Richmond

    2002-01-01

    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 TiCl4 and a Al(Et)3 co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl2 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 TiCl4 in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl2 by TiCl4 resulting in a thin film of MgCl2/TiClx, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl2/TiClx on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to ~1 Torr of Al(Et)3.

  4. 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.

  5. H 2O chemisorption and H 2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

    NASA Astrophysics Data System (ADS)

    Gorski, Alexandr; Yurkiv, Vitaliy; Starukhin, Dzmitry; Volpp, Hans-Robert

    The mechanism of H 2O dissociation as well as the adsorption and oxidation reaction of H 2 on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H 2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H 2 with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H 2 oxidation. Our experiments showed that in both the H 2O/YSZ and the H 2/YSZ + O heterogeneous reaction systems noticeable amounts of H 2O are "dissolved" in the bulk as interstitial hydrogen and hydroxyl species. The experimental H 2O desorption data is used to access the accuracy of the H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H 2 oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented.

  6. Study of the adsorption reactions of thiophene on Cu(I)/HY-Al2O3 by Fourier transform infrared and temperature-programmed desorption: adsorption, desorption, and sorbent regeneration mechanisms.

    PubMed

    Tang, Xiao-Lin; Shi, Li

    2011-10-04

    This work mainly involved the investigation of the adsorption of thiophene on Cu(I)-supported HY-Al(2)O(3). It demonstrated a high sulfur capacity of 10 mg sulfur/g sorbent when the HY/Al(2)O(3) mass ratio was 3, loaded with 12% copper, calcined at 550 °C, and tested at ambient temperature. In situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD) results indicated that the adsorption mechanisms on Cu(I)/HY-Al(2)O(3) primarily were π-complexation and sulfur-adsorbent (S-M; σ) bonds. Pyridine-FTIR showed the total weak Lewis acid contribution to the Cu(I)/HY-Al(2)O(3) adsorption desulfurization performance.

  7. The application of diffuse reflectance infrared spectroscopy and temperature-programmed desorption to investigate the interaction of methanol on eta-alumina.

    PubMed

    McInroy, Alastair R; Lundie, David T; Winfield, John M; Dudman, Chris C; Jones, Peter; Lennon, David

    2005-11-22

    The adsorption of methanol and its subsequent transformation to form dimethyl ether (DME) on a commercial grade eta-alumina catalyst has been investigated using a combination of mass selective temperature-programmed desorption (TPD) and diffuse reflectance infrared spectroscopy (DRIFTS). The infrared spectrum of a saturated overlayer of methanol on eta-alumina shows the surface to be comprised of associatively adsorbed methanol and chemisorbed methoxy species. TPD shows methanol and DME to desorb with respective maxima at 380 and 480 K, with desorption detectable for both molecules up to ca. 700 K. At 673 K, infrared spectroscopy reveals the formation of a formate species; the spectral line width of the antisymmetric C-O stretch indicates the adoption of a high symmetry adsorbed state. Conventional TPD using a tubular reactor, combined with mass spectrometric analysis of the gas stream exiting the IR cell, indicate hydrogen and methane evolution to be associated with formation of the surface formate group and CO evolution with its decomposition. A reaction scheme is proposed for the generation and decomposition of this important reaction intermediate. The overall processes involved in (i) the adsorption/desorption of methanol, (ii) the transformation of methanol to DME, and (iii) the formation and decomposition of formate species are discussed within the context of a recently developed four-site model for the Lewis acidity of eta-alumina.

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

    SciTech Connect

    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 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.

  9. 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.

  10. Laser desorption from a room temperature ionic liquid

    NASA Astrophysics Data System (ADS)

    Harris, Peter Ronald

    We report laser desorption from a Room Temperature Ionic Liquid (RTIL) as a novel source for time of flight mass spectrometry. We use the 2nd harmonic of an Nd:YAG laser to deposit intensities of 1-50 MW/cm2 via backside illumination onto our RTIL desorption sample. A microstructured metal grid situated on top of a glass microscope slide coated with RTIL serves as our desorption sample. The RTIL we use, 1-Butyl, 3-Methylimidazolium Hexafluorophosphate, remains liquid at pressures below 10-8 torr. The use of liquid desorption sample allows for improved surface conditions, homogeneity and sample life as compared to Matrix Assisted Laser Desorption Ionization (MALDI) techniques. Our desorption technique is also unique as it allows the study of both multiphoton and acoustic desorption processes within the same time of flight spectra. Our technique yields intrinsically high resolution, low noise data. We observe differences between ion species in their preference for desorption by a particular desorption method. Specifically, we observe desorption solely by acoustic means of an entire RTIL molecule adducted with an RTIL cation. Finally, we report the applicability of this technique for the desorption of biomolecules.

  11. 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

  12. Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 1. Characterization by temperature-programmed reaction and desorption

    SciTech Connect

    Curry-Hyde, H.E.; Musch, H.; Baiker, A. ); Schraml-Marth, M.; Wokaun, A. )

    1992-02-01

    Amorphous and crystalline chromia catalysts used for the selective catalytic reduction (SCR) of NO by NH{sub 3} have been characterized using temperature-programmed reaction and desorption of preadsorbed NO and NH{sub 3}. The acidity of the Lewis acid sites and the associated labile oxygen species are investigated using NH{sub 3} as a probe molecule. The degree of coordinative unsaturation of these sites is inferred from the reactions of NO. The effects of reduction, oxidation, and SCR treatment on the state of the Lewis acid sites and the labile oxygen are discussed. Lewis acid sites on crystalline chromia are more acidic than those on amorphous chromia. Different labile oxygen species are discernible based on their oxidizing strengths and the products formed. All labile oxygen is readily removed by reduction; SCR treatment leads to the partial removal of labile oxygen from both morphologies of chromia. The degree of lability of the different oxygen species is related to the morphology of the chromia. The proportions of one- and twofold coordinatively unsaturated sites (1 and 2 c.u.s.) depends strongly on the morphology of the chromia and its pretreatment. Both types of sites show distinct differences in the acidity dependent on the morphology of the chromia. The most significant difference between the two morphologies is seen after SCR treatment. Crystalline chromia shows a very high density of 1 c.u.s. compared to amorphous chromia. These sites are generated from 2 c.u.s. by abstraction of oxygen from NO. Implications of these results on the SCR reaction are discussed.

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

    PubMed

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

    2016-05-18

    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[double bond, length as m-dash]C vs. C[double bond, length as m-dash]O 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 multilayer coverages, reflecting the molecular structure of unperturbed molecules, with the spectra acquired for sub-monolayer coverages, at which the chemical bonds of the molecules are strongly distorted. Coverage-dependent IR spectra of acrolein on Pd(111) point to the strong changes in the adsorption geometry with increasing acrolein coverage. Acrolein adsorbs with the C[double bond, length as m-dash]C and C[double bond, length as m-dash]O bonds lying parallel to the surface in the low coverage regime and changes its geometry to a more upright orientation with increasing coverage. TPD studies indicate decomposition of the species adsorbed in the sub-monolayer regime upon heating. Similar strong coverage dependence of the IR spectra were found for propanal and allyl alcohol. For all investigated molecules a detailed assignment of vibrational bands is reported.

  14. Characteristics of mercury desorption from sorbents at elevated temperatures

    SciTech Connect

    Ho, T.C.; Yang, P.; Kuo, T.H.; Hopper, J.R.

    1998-12-31

    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. Elemental mercury and mercuric chloride were tested with activated carbon and bauxite. The experimental results indicated that mercury desorption from sorbents was strongly affected by the desorption temperature and the mercury-sorbent pair. Elemental mercury was observed to desorb faster than mercuric chloride and activated carbon appeared to have higher desorption limits than bauxite at low temperatures. A kinetic model considering the mechanisms of surface equilibrium, pore diffusion and external mass transfer was proposed to simulate the observed desorption profiles. The model was found to describe reasonably well the experimental results.

  15. 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.

  16. Development of ultralow energy (1-10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids.

    PubMed

    Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J; Pradeep, T; Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian

    2014-01-01

    Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1-10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH2(+).

  17. Development of ultralow energy (1–10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids

    SciTech Connect

    Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J.; Pradeep, T.; Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian

    2014-01-15

    Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1–10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH{sub 2}{sup +}.

  18. 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.

  19. The influence of the potassium promoter on the kinetics and thermodynamics of CO adsorption on a bulk iron catalyst applied in Fischer-Tropsch synthesis: a quantitative adsorption calorimetry, temperature-programmed desorption, and surface hydrogenation study.

    PubMed

    Graf, Barbara; Muhler, Martin

    2011-03-07

    The adsorption of carbon monoxide on an either unpromoted or potassium-promoted bulk iron catalyst was investigated at 303 K and 613 K by means of pulse chemisorption, adsorption calorimetry, temperature-programmed desorption and temperature-programmed surface reaction in hydrogen. CO was found to adsorb mainly molecularly in the absence of H(2) at 303 K, whereas the presence of H(2) induced CO dissociation at higher temperatures leading to the formation of CH(4) and H(2)O. The hydrogenation of atomic oxygen chemisorbed on metallic iron was found to occur faster than the hydrogenation of atomically adsorbed carbon. At 613 K CO adsorption occurred only dissociatively followed by recombinative CO(2) formation according to C(ads) + 2O(ads)→ CO(2(g)). The presence of the potassium promoter on the catalyst surface led to an increasing strength of the Fe-C bond both at 303 K and 613 K: the initial differential heat of molecular CO adsorption on the pure iron catalyst at 303 K amounted to 102 kJ mol(-1), whereas it increased to 110 kJ mol(-1) on the potassium-promoted sample, and the initial differential heat of dissociative CO adsorption on the unpromoted iron catalyst at 613 K amounted to 165 kJ mol(-1), which increased to 225 kJ mol(-1) in the presence of potassium. The calorimetric CO adsorption experiments also reveal a change of the energetic distribution of the CO adsorption sites present on the catalyst surface induced by the potassium promoter, which was found to block a fraction of the CO adsorption sites.

  20. Apparatus for low temperature thermal desorption spectroscopy of portable samples.

    PubMed

    Stuckenholz, S; Büchner, C; Ronneburg, H; Thielsch, G; Heyde, M; Freund, H-J

    2016-04-01

    An experimental setup for low temperature thermal desorption spectroscopy (TDS) integrated in an ultrahigh vacuum-chamber housing a high-end scanning probe microscope for comprehensive multi-tool surface science analysis is described. This setup enables the characterization with TDS at low temperatures (T > 22 K) of portable sample designs, as is the case for scanning probe optimized setups or high-throughput experiments. This combination of techniques allows a direct correlation between surface morphology, local spectroscopy, and reactivity of model catalysts. The performance of the multi-tool setup is illustrated by measurements of a model catalyst. TDS of CO from Mo(001) and from Mo(001) supported MgO thin films were carried out and combined with scanning tunneling microscopy measurements.

  1. Apparatus for low temperature thermal desorption spectroscopy of portable samples

    NASA Astrophysics Data System (ADS)

    Stuckenholz, S.; Büchner, C.; Ronneburg, H.; Thielsch, G.; Heyde, M.; Freund, H.-J.

    2016-04-01

    An experimental setup for low temperature thermal desorption spectroscopy (TDS) integrated in an ultrahigh vacuum-chamber housing a high-end scanning probe microscope for comprehensive multi-tool surface science analysis is described. This setup enables the characterization with TDS at low temperatures (T > 22 K) of portable sample designs, as is the case for scanning probe optimized setups or high-throughput experiments. This combination of techniques allows a direct correlation between surface morphology, local spectroscopy, and reactivity of model catalysts. The performance of the multi-tool setup is illustrated by measurements of a model catalyst. TDS of CO from Mo(001) and from Mo(001) supported MgO thin films were carried out and combined with scanning tunneling microscopy measurements.

  2. An infared spectroscopy and temperature-programmed desorption study of CO on MoO[sub 3]/Al[sub 2]O[sub 3] catalysts: Quantitation of the molybdena overlayer

    SciTech Connect

    Diaz, A.L.; Bussell, M.E. )

    1993-01-14

    The adsorption of CO on pure [gamma]-Al[sub 2]O[sub 3] and a series of MoO[sub 3]/Al[sub 2]O[sub 3] catalysts with different Mo loadings has been investigated using infrared (IR) spectroscopy and temperature-programmed desorption (TPD). Carbon monoxide adsorbs selectively on Al[sup 3+] sites on the uncovered, free alumina portion of the surface; these sites are created by dehydroxylation of the alumina. As the Mo loading is increased, the CO adsorption capacity of the catalysts decreases in a linear fashion as the MoO[sub 3] overlayer covers an increasing fraction of the alumina support. Overlayer growth saturates at a loading of (42[+-]3) [times] 10[sup 13] Mo atoms/cm[sup 2] and corresponds to less than a complete monolayer as 14 [+-] 5% of the alumina support remains uncovered. Extrapolation of the overlayer growth curve to monolayer coverage allows calculation of a MoO[sub 3] cross-sectional area of [approx]22[Angstrom][sup 2], in good agreement with values predicted by theoretical models. 37 refs., 11 figs.

  3. Growth of an Ultrathin Zirconia Film on Pt3Zr Examined by High-Resolution X-ray Photoelectron Spectroscopy, Temperature-Programmed Desorption, Scanning Tunneling Microscopy, and Density Functional Theory

    PubMed Central

    2014-01-01

    Ultrathin (∼3 Å) zirconium oxide films were grown on a single-crystalline Pt3Zr(0001) substrate by oxidation in 1 × 10–7 mbar of O2 at 673 K, followed by annealing at temperatures up to 1023 K. The ZrO2 films are intended to serve as model supports for reforming catalysts and fuel cell anodes. The atomic and electronic structure and composition of the ZrO2 films were determined by synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Oxidation mainly leads to ultrathin trilayer (O–Zr–O) films on the alloy; only a small area fraction (10–15%) is covered by ZrO2 clusters (thickness ∼0.5–10 nm). The amount of clusters decreases with increasing annealing temperature. Temperature-programmed desorption (TPD) of CO was utilized to confirm complete coverage of the Pt3Zr substrate by ZrO2, that is, formation of a closed oxide overlayer. Experiments and DFT calculations show that the core level shifts of Zr in the trilayer ZrO2 films are between those of metallic Zr and thick (bulklike) ZrO2. Therefore, the assignment of such XPS core level shifts to substoichiometric ZrOx is not necessarily correct, because these XPS signals may equally well arise from ultrathin ZrO2 films or metal/ZrO2 interfaces. Furthermore, our results indicate that the common approach of calculating core level shifts by DFT including final-state effects should be taken with care for thicker insulating films, clusters, and bulk insulators. PMID:25688293

  4. Growth of an Ultrathin Zirconia Film on Pt3Zr Examined by High-Resolution X-ray Photoelectron Spectroscopy, Temperature-Programmed Desorption, Scanning Tunneling Microscopy, and Density Functional Theory.

    PubMed

    Li, Hao; Choi, Joong-Il Jake; Mayr-Schmölzer, Wernfried; Weilach, Christian; Rameshan, Christoph; Mittendorfer, Florian; Redinger, Josef; Schmid, Michael; Rupprechter, Günther

    2015-02-05

    Ultrathin (∼3 Å) zirconium oxide films were grown on a single-crystalline Pt3Zr(0001) substrate by oxidation in 1 × 10(-7) mbar of O2 at 673 K, followed by annealing at temperatures up to 1023 K. The ZrO2 films are intended to serve as model supports for reforming catalysts and fuel cell anodes. The atomic and electronic structure and composition of the ZrO2 films were determined by synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Oxidation mainly leads to ultrathin trilayer (O-Zr-O) films on the alloy; only a small area fraction (10-15%) is covered by ZrO2 clusters (thickness ∼0.5-10 nm). The amount of clusters decreases with increasing annealing temperature. Temperature-programmed desorption (TPD) of CO was utilized to confirm complete coverage of the Pt3Zr substrate by ZrO2, that is, formation of a closed oxide overlayer. Experiments and DFT calculations show that the core level shifts of Zr in the trilayer ZrO2 films are between those of metallic Zr and thick (bulklike) ZrO2. Therefore, the assignment of such XPS core level shifts to substoichiometric ZrO x is not necessarily correct, because these XPS signals may equally well arise from ultrathin ZrO2 films or metal/ZrO2 interfaces. Furthermore, our results indicate that the common approach of calculating core level shifts by DFT including final-state effects should be taken with care for thicker insulating films, clusters, and bulk insulators.

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

    SciTech Connect

    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 surface 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.

  6. 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

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

    SciTech Connect

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

    2008-09-01

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

  8. Effect of sodium chloride, sodium nitrite and temperature on desorption isotherms of previously frozen beef.

    PubMed

    Kabil, Emre; Aktaş, Nesimi; Balcı, Ercan

    2012-04-01

    Moisture desorption isotherms of beef were determined in the relative humidity range of 23 to 90% at 5, 15 and 25°C and at 2.5% NaCl and 2.5% NaCl+150 ppm NaNO(2) content. Desorption isotherms were found to be typical type II sigmoid. The water content at equilibrium was higher in beef with NaCl and NaCl+NaNO(2) than control samples. Experimental data were fitted to various mathematical models and it was found that the Peleg model was best in describing the equilibrium moisture content relationship for beef samples over the entire range of temperatures. The net isosteric heat of sorption was estimated from equilibrium desorption data, using the Clausius-Clapeyron equation. Isosteric heats of desorption were found to increase with decreasing moisture content.

  9. Effect of temperature and particle size on the thermal desorption of PCBs from contaminated soil.

    PubMed

    Qi, Zhifu; Chen, Tong; Bai, Sihong; Yan, Mi; Lu, Shengyong; Buekens, Alfons; Yan, Jianhua; Bulmău, Cora; Li, Xiaodong

    2014-03-01

    Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 °C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420-841 μm and fine soil with particles <250 μm. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 °C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 °C; at 600 °C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 °C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer.

  10. 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. ...

  11. 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. ...

  12. 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...

  13. 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.

  14. ON-SITE ENGINEERING REPORT FOR THE LOW-TEMPERATURE THERMAL DESORPTION PILOT-SCALE TEST ON CONTAMINATED SOIL

    EPA Science Inventory

    Performance of the thermal desorption process for removal of organic contaminants, mostly polynuclear aromatic hydrocarbons (PAHs), from soils was evaluated. The Superfund Site soil tested was a fine sandy soil contaminated with creosote. An optimum operating temperature of 550 C...

  15. Finite-Temperature Hydrogen Adsorption/Desorption Thermodynamics Driven by Soft Vibration Modes

    SciTech Connect

    Woo, Sung-Jae; Lee, Eui-Sup; Yoon, Mina; Yong-Hyun, Kim

    2013-01-01

    It is widely accepted that room-temperature hydrogen storage on nanostructured or porous materials requires enhanced dihydrogen adsorption. In this work we reveal that room-temperature hydrogen storage is possible not only by the enhanced adsorption, but also by making use of the vibrational free energy from soft vibration modes. These modes exist for example in the case of metallo-porphyrin-incorporated graphenes (M-PIGs) with out-of-plane ( buckled ) metal centers. There, the in-plane potential surfaces are flat because of multiple-orbital-coupling between hydrogen molecules and the buckled-metal centers. This study investigates the finite-temperature adsorption/desorption thermodynamics of hydrogen molecules adsorbed on M-PIGs by employing first-principles total energy and vibrational spectrum calculations. Our results suggest that the current design strategy for room-temperature hydrogen storage materials should be modified by explicitly taking finite-temperature vibration thermodynamics into account.

  16. 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.

  17. Laser temperature jump relaxation measurements of adsorption/desorption kinetics at liquid/solid interfaces

    SciTech Connect

    Waite, S.W.; Harris, J.M.; Holzwarth, J.F.

    1995-04-15

    The iodine laser temperature jump method is used to study adsorption/desorption kinetics at a methylated silica/solution interface. A suspension of C1-derivatized fumed silica is used for the kinetic measurements. The colloidal silica does not significantly change the attenuation of near-IR radiation from the iodine laser and allows the surface site concentration to be varied so that adsorption and desorption rates can be determined. The temperature jump relaxation method was used to investigate the effect of electrolyte on adsorption of a charged solute (ANS) on a C1 silica surface. Adsorption equilibrium conditions were optimized to observe a maximum relaxation signal. Without electrolyte, the relaxation signal is biexponential, which is also reflected in a broad chromatographic peak shape and a two-site sorption isotherm. When electrolyte is added, the relaxation signal is primarily single exponential, which agrees with the linear adsorption isotherm. The adsorption rate and equilibrium constant were found to increase significantly with added electrolyte, which showed that adsorption kinetics can influence both band broadening and retention. 28 refs., 7 figs., 4 tab.

  18. Kinetics of desorption of KCL from polyvinyl alcohol-borate hydrogel in aqueous-alcoholic solvents at different temperatures

    NASA Astrophysics Data System (ADS)

    Saeed, Rehana; Abdeen, Zain Ul

    2015-11-01

    Desorption kinetics of adsorbed KCl from Polyvinyl alcohol borate hydrogel was studied by conductivity method in aqueous system and aqueous binary solvent system using 50% aqueous-methanol, aqueous- ethanol and aqueous-propanol at different temperature ranging from 293 to 313 K. Desorption process follows pseudo first order and intra particle diffusion kinetics was analyzed on the basis of linear regression coefficient R 2 and chi square test χ2 values. The process of desorption of KCl from hydrogel was favorable in aqueous system, the study reveals the fact that the polarity of solvent influenced the kinetics of desorption, on decrement of polarity of solvent rate, rate constant and intra particle rate constant decreases. Based on intra particle kinetic equation fitting it was concluded that desorption was initiated by removal of ions from surface of hydrogel later on ions interacted inside the cross linked unit was also become free. Temperature enhances the rate, rate constant and intra particle rate constant. Thermodynamic parameters attributed towards the fact that the process of desorption of KCl from hydrogel is non-spontaneous in nature.

  19. 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.

  20. 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.

  1. Matrix-assisted laser desorption/ionization mass spectrometry of covalently cationized polyethylene as a function of sample temperature

    NASA Astrophysics Data System (ADS)

    Wallace, W. E.; Blair, W. R.

    2007-05-01

    A pre-charged, low molecular mass, low polydispersity linear polyethylene was analyzed with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry as a function of sample temperature between 25 °C and 150 °C. This temperature range crosses the polyethylene melting temperature. Buckminsterfullerene (C60) was used as MALDI matrix due to the high volatility of typical MALDI matrices making them unsuitable for heating in vacuum. Starting at 90 °C there is an increase in polyethylene ion intensity at fixed laser energy. By 150 °C the integrated total ion intensity had grown by six-fold indicating that melting did indeed increase ion yield. At 150 °C the threshold laser intensity to produce intact polyethylene ions decreased by about 25%. Nevertheless, significant fragmentation accompanied the intact polyethylene ions even at the highest temperatures and the lowest laser energies.

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

    SciTech Connect

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

    2016-03-03

    The desorption kinetics for Ar, Kr, Xe, N2, O2, CO, methane, ethane, and propane from grapheme covered Pt(111) and amorphous solid water (ASW) surfaces are investigated using temperature programmed desorption (TPD). The TPD spectra for all of the adsorbates from graphene have well-resolved first, second, third, and multi- layer desorption peaks. The alignment of the leading edges is consistent the zero-order desorption for all of the adsorbates. An Arrhenius analysis is used to obtain desorption energies and prefactors for desorption from graphene for all of the adsorbates. In contrast, the leading desorption edges for the adsorbates from ASW do not align (for coverages < 2 ML). The non-alignment of TPD leading edges suggests that there are multiple desorption binding sites on the ASW surface. Inversion analysis is used to obtain the coverage dependent desorption energies and prefactors for desorption from ASW for all of the adsorbates.

  3. 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.

  4. Waste/Rock Interactions Technology Program: the status of radionuclide sorption-desorption studies performed by the WRIT program

    SciTech Connect

    Serne, R.J.; Relyea, J.F.

    1982-04-01

    The most credible means for radionuclides disposed as solid wastes in deep-geologic repositories to reach the biosphere is through dissolution of the solid waste and subsequent radionuclide transport by circulating ground water. Thus safety assessment activities must consider the physicochemical interactions between radionculides present in ground water with package components, rocks and sediments since these processes can significantly delay or constrain the mass transport of radionuclides in comparison to ground-water movement. This paper focuses on interactions between dissolved radiouclides in ground water and rocks and sediments away from the near-field repository. The primary mechanism discussed is adsorption-desorption, which has been studied using two approaches. Empirical studies of adsorption-desorption rely on distribution coefficient measurements while mechanism studies strive to identify, differentiate and quantify the processes that control nuclide retardation.

  5. 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.

  6. 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

    2014-09-09

    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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Examining the role of temperature and sediment-chemical contact time on desorption and bioavailability of sediment-associated tetrabromo diphenyl ether and benzo(a)pyrene.

    PubMed

    Sormunen, Arto J; Leppänen, M T; Kukkonen, J V K

    2009-05-01

    The effects of temperature and sediment-chemical contact time on desorption and bioaccumulation of sediment-spiked (14)C-labelled 2,2',4,4'-tetrabromo diphenyl ether (BDE-47) and benzo(a)pyrene (BaP) were examined. Experiments were performed after 2 or 6 weeks and 23 or 24 months sediment-chemical contact time at 10 and 20 degrees C. Desorption was measured in a sediment-water suspension using Tenax extraction, and bioaccumulation was measured by exposing Lumbriculus variegatus (Oligochaeta) to BDE-47 and BaP-spiked sediments in a 10d kinetic study. Biota-sediment accumulation factors (BSAFs) ranged between 2.9 and 4.3 for BDE-47 and between 0.5 and 0.9 for BaP. Thus, temperature and aging had a minor effect on bioavailability estimates. On the other hand, the difference between the chemicals was clear and could not be interpreted solely by reference to the size of the desorbing fractions, although the rapidly desorbing fraction-revised estimate clearly reduced the difference. The remaining discrepancy may be related to methodological (Tenax extraction vs. worm exposure) and/or biological (digestive extraction) causes. However, the data support the role of diffusional forces in the bioavailability of sediment-associated organic contaminants. Therefore, desorption-revised bioavailability estimates would lead to more precise bioavailability estimates than the traditional sediment organic carbon-organisms' lipids-based equilibrium partitioning approach.

  13. 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)

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

    PubMed

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

    2015-05-01

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

  15. 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.

  16. 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)

  17. Hydrogen absorption and desorption kinetics in fullerite C60 single crystals. Low-temperature micromechanical and structural characteristics of the interstitial solid solution C60(H2)x

    NASA Astrophysics Data System (ADS)

    Fomenko, L. S.; Lubenets, S. V.; Natsik, V. D.; Stetsenko, Yu. E.; Yagotintsev, K. A.; Strzhemechny, M. A.; Prokhvatilov, A. I.; Osipyan, Yu. A.; Izotov, A. N.; Sidorov, N. S.

    2008-01-01

    The microhardness HV and lattice parameter a of C60 single crystals are measured at room temperature as functions of the hydrogen saturation time t for several values of the saturation temperature (250, 300, and 350°C) at a fixed hydrogen pressure p =30atm. According to the measurements of HV and a, the kinetics of hydrogen absorption is described by a simple exponential law with a single, temperature-dependent characteristic time. In highly saturated samples the microhardness is 4 times greater than for the initial C60 crystal, while the lattice parameter is 0.2% larger. The temperature dependence of the microhardness HV and lattice parameter a of C60(H2)x crystals is investigated in the temperature interval 77-300K. The introduction of hydrogen lowers the temperature of the fcc-sc phase transition, and the transition becomes strongly broadened in temperature. The dependence of the microhardness of the saturated sample on the hold time in air at room temperature is described by the sum of two exponentials with different characteristic times. Kinetics of this kind is presumably due to two processes: desorption of hydrogen from the sample, which causes a decrease of the microhardness, and a simultaneous penetration of gaseous impurities into the sample from the surrounding air, which is accompanied by hardening. The influence of the H2 molecules on the characteristic of the intermolecular interaction in fullerite C60 is discussed and the intercalation-induced processes of dislocation slip and microfracture.

  18. 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.

  19. Temperature measurements during the CAMP program. [Cold Arctic Mesopause Program

    NASA Technical Reports Server (NTRS)

    Philbrick, C. R.; Barnett, J.; Gerndt, R.; Offermann, D.; Pendleton, W. R., Jr.; Schlyter, P.; Witt, G.; Schmidlin, J. F.

    1984-01-01

    The Cold Arctic Mesopause Program (CAMP) was conducted at ESRANGE, Sweden, in July/August 1982. During the time period of several weeks, the temperature was monitored by ground-based OH emission spectrometers and by satellite radiance measurements. Rocket launchings occurred on the nights of 3/4 and 11/12 August. On 3/4 August, seven rocket payloads were launched during a period of noctilucent cloud sighting over ESRANGE. The presence of the NLC was confirmed by several rocket-borne photometer profiles. The temperature measurements showed that the temperature profiles in the stratosphere and lower mesosphere were near the expected values of high latitude summer models. A large amplitude wave structure with three temperature minima of 139K, 114K and 111K were observed at altitudes between 83 and 94 km. The temperature minimum at 83 km was the location of the observed NLC. The temperature minima caused by the growth of the gravity wave amplitude in the highly stable mesosphere provide the regions for the growth of particles by nucleation to optical scattering size, as well as regions where the nuclei for condensation can be formed through ion chemistry paths.

  20. 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

  1. 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.

  2. 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.

  3. Atomic Force Microscopy Thermally-Assisted Microsampling with Atmospheric Pressure Temperature Ramped Thermal Desorption/Ionization-Mass Spectrometry Analysis

    DOE PAGES

    Hoffmann, William D.; Kertesz, Vilmos; Srijanto, Bernadeta R.; ...

    2017-02-20

    The use of atomic force microscopy controlled nano-thermal analysis probes for reproducible spatially resolved thermally-assisted sampling of micrometer-sized areas (ca. 11 m 17 m wide 2.4 m deep) from relatively low number average molecular weight (Mn < 3000) polydisperse thin films of poly(2-vinylpyridine) (P2VP) is presented. Following sampling, the nano-thermal analysis probes were moved up from the surface and the probe temperature ramped to liberate the sampled materials into the gas phase for atmospheric pressure chemical ionization and mass spectrometric analysis. Furthermore, the procedure and mechanism for material pickup, the sampling reproducibility and sampling size are discussed and the oligomermore » distribution information available from slow temperature ramps versus ballistic temperature jumps is presented. For the Mn = 970 P2VP, the Mn and polydispersity index determined from the mass spectrometric data were in line with both the label values from the sample supplier and the value calculated from the simple infusion of a solution of polymer into the commercial atmospheric pressure chemical ionization source on this mass spectrometer. With a P2VP sample of higher Mn (Mn = 2070 and 2970), intact oligomers were still observed (as high as m/z 2793 corresponding to the 26-mer), but a significant abundance of thermolysis products were also observed. In addition, the capability for confident identification of the individual oligomers by slowly ramping the probe temperature and collecting data dependent tandem mass spectra was also demonstrated. We also discuss the material type limits to the current sampling and analysis approach as well as possible improvements in nano-thermal analysis probe design to enable smaller area sampling and to enable controlled temperature ramps beyond the present upper limit of about 415°C.« less

  4. Atomic Force Microscopy Thermally-Assisted Microsampling with Atmospheric Pressure Temperature Ramped Thermal Desorption/Ionization-Mass Spectrometry Analysis

    SciTech Connect

    Hoffmann, William D; Kertesz, Vilmos; Srijanto, Bernadeta R; Van Berkel, Gary J

    2017-01-01

    The use of atomic force microscopy controlled nano-thermal analysis probes for reproducible spatially resolved thermally-assisted sampling of micrometer-sized areas (ca. 11 m 17 m wide 2.4 m deep) from relatively low number average molecular weight (Mn < 3000) polydisperse thin films of poly(2-vinylpyridine) (P2VP) is presented. Following sampling, the nano-thermal analysis probes were moved up from the surface and the probe temperature ramped to liberate the sampled materials into the gas phase for atmospheric pressure chemical ionization and mass spectrometric analysis. The procedure and mechanism for material pickup, the sampling reproducibility and sampling size are discussed and the oligomer distribution information available from slow temperature ramps versus ballistic temperature jumps is presented. For the Mn = 970 P2VP, the Mn and polydispersity index determined from the mass spectrometric data were in line with both the label values from the sample supplier and the value calculated from the simple infusion of a solution of polymer into the commercial atmospheric pressure chemical ionization source on this mass spectrometer. With a P2VP sample of higher Mn (Mn = 2070 and 2970), intact oligomers were still observed (as high as m/z 2793 corresponding to the 26-mer), but a significant abundance of thermolysis products were also observed. In addition, the capability for confident identification of the individual oligomers by slowly ramping the probe temperature and collecting data dependent tandem mass spectra was also demonstrated. The material type limits to the current sampling and analysis approach as well as possible improvements in nano-thermal analysis probe design to enable smaller area sampling and to enable controlled temperature ramps beyond the present upper limit of about 415 oC are also discussed.

  5. Low Temperature Thermal Desorption Processes for the Remediation of Soils Contaminated with Solvents, Hydrocarbons, and Petroleum Products

    DTIC Science & Technology

    1993-02-01

    FUNDING NUMBERS ATTN: ENAEC-TS-D PROGRAM PROJECT TASK WORK UNIT Aberdeen Proving Ground, MD 21010-5401 ELEMENT NO. NO. NO. ACCESSION NO. 11. TITLE (Include...If these soils are used as aggregate for concrete, fine organic particles may weaken cement bonds and other chemicals, notably any soluble metal...projects may be considered elements of system operating parameters, contaminant characteristics, and soil characteristics. The following will expand on each

  6. 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.

  7. The NASA high temperature superconductivity program

    NASA Astrophysics Data System (ADS)

    Sokoloski, Martin M.; Romanofsky, Robert R.

    1990-04-01

    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.

  8. 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-).

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  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. 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.

  12. 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

  13. Size effect on thermal desorption of CO from Pt nanostructures on graphite

    NASA Astrophysics Data System (ADS)

    Julukian, A.; Fadnes, T.; Raaen, S.; Balci, M.

    2011-06-01

    Self-assembled Pt nanostructures, which are formed by evaporation and subsequent diffusion limited aggregation of Pt on graphite, have been studied by photoemission and scanning electron microscopy. Adsorption of CO has been studied by temperature programmed desorption. Charge induced Pt 4f core level shifts in the order of 1 eV that depend on the effective dimensions of the nanostructures have been observed, and effective dimensions of the Pt structures have been defined based on the Pt 4f core level shifts. The effective dimensions of the Pt structures have been correlated with changes in the thermal desorption of adsorbed CO. It is observed that smaller effective dimensions in the few nanometer range result in lower desorption temperatures of up to 50 K. The possible role of hot electrons in the adsorption process has been discussed.

  14. Thermal dissociation and desorption of PH3 on Si(001): A reinterpretation of spectroscopic data

    NASA Astrophysics Data System (ADS)

    Wilson, H. F.; Warschkow, O.; Marks, N. A.; Curson, N. J.; Schofield, S. R.; Reusch, T. C. G.; Radny, M. W.; Smith, P. V.; McKenzie, D. R.; Simmons, M. Y.

    2006-11-01

    It was recently shown that low-coverage PH3 dosing of the Si(001) surface is fully dissociative at room temperature with PH2+H , PH+2H , and P+3H as intermediate species. Here, we consider high-coverage PH3 dosing and show that the increased density of adsorbates leads to qualitatively different behavior due to competition between thermal dissociation and desorption. Using a combination of existing temperature-programmed desorption data and density functional theory simulations, we present a detailed mechanistic understanding of phosphine adsorption, dissociation, and desorption on the surface. This understanding provides a consistent interpretation of existing infrared and x-ray spectroscopic data, as well as an explanation of the dependence of the phosphorus saturation coverage on dosing conditions.

  15. Desorption in Mass Spectrometry.

    PubMed

    Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi

    2017-01-01

    In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e., ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed.

  16. Desorption in Mass Spectrometry

    PubMed Central

    Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi

    2017-01-01

    In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e., ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed. PMID:28337398

  17. 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.

  18. Theoretical and experimental studies of hydrogen adsorption and desorption on Ir surfaces

    DOE PAGES

    Kaghazchi, Payam; Jacob, Timo; Chen, Wenhua; ...

    2013-06-03

    Here, we report adsorption and desorption of hydrogen on planar Ir(210) and faceted Ir(210), consisting of nanoscale {311} and (110) facets, by means of temperature programmed desorption (TPD) and density functional theory (DFT) in combination with the ab initio atomistic thermodynamics approach. TPD spectra show that only one H2 peak is seen from planar Ir(210) at all coverages whereas a single H2 peak is observed at around 440 K (F1) at fractional monolayer (ML) coverage and an additional H2 peak appears at around 360 K (F2) at 1 ML coverage on faceted Ir(210), implying structure sensitivity in recombination and desorptionmore » of hydrogen on faceted Ir(210) versus planar Ir(210), but no evidence is found for size effects in recombination and desorption of hydrogen on faceted Ir(210) for average facet sizes of 5-14 nm. Calculations indicate that H prefers to bind at the two-fold short-bridge sites of the Ir surfaces. In addition, we studied the stability of the Ir surfaces in the presence of hydrogen at different H coverages through surface free energy plots as a function of the chemical potential, which is also converted to a temperature scale. Moreover, the calculations revealed the origin of the two TPD peaks of H2 from faceted Ir(210): F1 from desorption of H2 on {311} facets while F2 from desorption of H2 on (110) facets.« less

  19. Temperature lowering program for homogeneous doping in flux growth

    NASA Astrophysics Data System (ADS)

    Qiwei, Wang; Shouquan, Jia

    1989-10-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1991-03-01

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

  3. Current-Driven Hydrogen Desorption from Graphene: Experiment and Theory

    SciTech Connect

    Gao, L.; Pal, Partha P.; Seideman, Tamar; Guisinger, Nathan P.; Guest, Jeffrey R.

    2016-02-04

    Electron-stimulated desorption of hydrogen from the graphene/SiC(0001) surface at room temperature was investigated with ultrahigh vacuum scanning tunneling microscopy and ab initio calculations in order to elucidate the desorption mechanisms and pathways. Two different desorption processes were observed. In the high electron energy regime (4-8 eV), the desorption yield is independent of both voltage and current, which is attributed to the direct electronic excitation of the C-H bond. In the low electron energy regime (2-4 eV), however, the desorption yield exhibits a threshold dependence on voltage, which is explained by the vibrational excitation of the C-H bond via transient ionization induced by inelastic tunneling electrons. The observed current-independence of the desorption yield suggests that the vibrational excitation is a singleelectron process. We also observed that the curvature of graphene dramatically affects hydrogen desorption. Desorption from concave regions was measured to be much more probable than desorption from convex regions in the low electron energy regime (~ 2 eV), as would be expected from the identified desorption mechanism

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

    PubMed

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

    2013-12-15

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

  5. Overview of NASA's advanced high temperature engine materials technology program

    NASA Technical Reports Server (NTRS)

    Ginty, Carol A.; Gray, Hugh R.

    1992-01-01

    NASA's 'HITEMP' program has been charged with development of propulsion systems technologies for next-generation civil and military aircraft, stressing high-temperature/low-density composites. These encompass polymer-matrix composites for fans, ducts, and compressor cases, and intermetallic and metallic alloy matrix composites for applications in turbine disks, blades, and vanes, and ceramic matrix composites for combustors and turbines. An overview is presented of program concerns and achievements to date.

  6. 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

  7. Theoretical and experimental studies of hydrogen adsorption and desorption on Ir surfaces

    SciTech Connect

    Kaghazchi, Payam; Jacob, Timo; Chen, Wenhua; Bartynski, Robert A.

    2013-06-03

    Here, we report adsorption and desorption of hydrogen on planar Ir(210) and faceted Ir(210), consisting of nanoscale {311} and (110) facets, by means of temperature programmed desorption (TPD) and density functional theory (DFT) in combination with the ab initio atomistic thermodynamics approach. TPD spectra show that only one H2 peak is seen from planar Ir(210) at all coverages whereas a single H2 peak is observed at around 440 K (F1) at fractional monolayer (ML) coverage and an additional H2 peak appears at around 360 K (F2) at 1 ML coverage on faceted Ir(210), implying structure sensitivity in recombination and desorption of hydrogen on faceted Ir(210) versus planar Ir(210), but no evidence is found for size effects in recombination and desorption of hydrogen on faceted Ir(210) for average facet sizes of 5-14 nm. Calculations indicate that H prefers to bind at the two-fold short-bridge sites of the Ir surfaces. In addition, we studied the stability of the Ir surfaces in the presence of hydrogen at different H coverages through surface free energy plots as a function of the chemical potential, which is also converted to a temperature scale. Moreover, the calculations revealed the origin of the two TPD peaks of H2 from faceted Ir(210): F1 from desorption of H2 on {311} facets while F2 from desorption of H2 on (110) facets.

  8. 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.

  9. Thermal Desorption/Ultraviolet Photolysis Process Research, Test and Evaluation Performed at Johnston Island for the USAF Installation Restoration Program. Volume 1. Technical Report

    DTIC Science & Technology

    1987-12-01

    bmission from a stack. The photochemical decomposition of organics in the solvent is related to UV light wattage and exposure time. iii Your desorption test...minutes of exposure . Tests in the stirred reactor using Soltroi0170 spiked with the free acids and butyl esters of 2,4-D and 2,4,5-T verified that...reaction assembly is enclosed in a lightproof stainless steel chamber with a locked door to prevent accidental exposure to the UV radiation, which can be

  10. 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

  11. 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.

  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. Desorption Kinetics of H2O, H2, CO, and CO2 from Silica Reinforced Polysiloxane

    SciTech Connect

    Dinh, L.; Balooch, M.

    1999-08-11

    We performed temperature programmed desorption up to 500K on silica-reinforced polysiloxane in both solid and foamed forms (M9787 and M9750 respectively). Our data show that H{sub 2}O was the dominant desorbing species in both forms of silicone (on the order of 100 {micro}g of physisorbed water and 900 {micro}g of chemisorbed water per gram of polymer), which are expected to be very hydrophilic when dehydrated. Detailed studies of the TPD spectra of H{sub 2}O from the silicones and from the fumed silica fillers suggest that H{sub 2}O molecules preferentially adsorbed on the surface of silica particles contained in the silicones with activation energies of desorption of 15 {+-} 3 kcal/mol and 50 {+-} 10 kcal/mol. There was strong evidence of H{sub 2} desorption below 400K from the silicones. The equivalent concentration of H{sub 2} in the silicones was 0.44 {micro}g of H{sub 2} per gram of silicone. Other species desorbing from the silicones were CO, and CO{sub 2} with concentrations on the order of 2.5 {micro}g, and 1.6 {micro}g per gram of silicone and activation energies of desorption of 10 {+-} 2 kcal/mol and 9.5 {+-} 1.5 kcal/mol, respectively.

  14. High temperature aspects of the European Hermes programs

    NASA Astrophysics Data System (ADS)

    Isakeit, D.

    The European Space Agency's (ESA) program for the development of the Hermes spaceplane is the first program in Europe dealing with hypersonics on a complex shape. Aerodynamics and aerothermodynamics, particularly with respect to the hot hypersonic flight regime, as well as structures and thermal protection techniques, are among the most important technologies for Hermes. Since the beginning of the Hermes development program, a highly intensive effort in these areas has been undertaken. The effort in the aerodynamical field covered the modelization of the chemical and physical phenomena, computational fluid dynamics (CFD) calculations of increasing complexity, and experimental simulations in various types of wind tunnels and other test facilities. In the field of hot structures and thermal protection, new concepts have been developed. They led to the build-up of new high temperature test facilities in Europe. The present paper presents the main results obtained in high temperature related technologies during the Hermes development phase 1 and points out further efforts which remain to be done in this field.

  15. Laser desorption of NO from a thick C 60 film

    NASA Astrophysics Data System (ADS)

    Hoger, T.; Marzok, C.; Jongma, R. T.; Zacharias, H.

    2006-09-01

    The desorption of NO molecules from a thick C 60 film is reported. A thermal desorption spectrum indicates two adsorption sites with binding energies of Eb = 0.30 eV and 0.55 eV. For laser desorption the fullerene surface is exposed to NO and excited by 7 ns UV laser pulses. Desorbing NO molecules are recorded state selectively as well as time resolved. The time-of-flight measurement indicates three different desorption pathways. A fast channel shows rovibronic temperatures of Trot( v″ = 0) = 370 K, Trot( v″ = 1) = 390 K and Tvib = 610 K as well as strong rotational-translational coupling. The desorption yield for the fast channel increases linearly with pulse energy with a desorption cross section of σ = (5.1 ± 0.9) × 10 -17 cm 2. Dominating the signal for small J″ values is a slow channel with low rotational and translational temperatures of about 110 K. We assign this peak to a laser-induced thermal desorption. For large pump-probe delays the data deviate from the Maxwellian flux distribution and a third channel appears with extremely late arrival times.

  16. 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.

  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. Cooled High-Temperature Radial Turbine Program. Phase 2

    DTIC Science & Technology

    1992-05-01

    proposed for advanced engines with high power-to-weight and inproved SFC requirements. The addition of cooling to the blades of a metal radial turbine ...4 secl/2 ) 62.2 Blade - jet Speed Ratio 0.66 Adiabatic Efficiency (T-to-T, %) 87.0 Cooling flows for the gasifier turbine section are set at 5.7%. The...Way Cincinnati, OH 45215-6301 85 COOLED HIGH-TEMPERATURE RADIAL TURBINE PROGRAM DISTRIBUTION LIST Number Qf Copies General Electric Aircraft Engines

  19. 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.

  20. Desorption of Hot Molecules from Photon Irradiated Interstellar Ices

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  1. Thermal helium desorption behavior in advanced ferritic steels

    NASA Astrophysics Data System (ADS)

    Kimura, Akihiko; Sugano, R.; Matsushita, Y.; Ukai, S.

    2005-02-01

    Thermal helium desorption measurements were performed to investigate the difference in the helium trapping and accumulation behavior among a reduced activation ferritic (RAF) steel and oxide dispersion strengthening (ODS) steels after implantation of He+ ions at room temperature. Thermal helium desorption spectra (THDS) were obtained during annealing to 1200 °C at a heating rate of 1 °C/s. The THDS of the ODS steels are very similar to that of the RAF steel, except for the presence of the peak in the temperature range from 800 to 1000 °C, where the α γ transformation related helium desorption from the γ-phase is considered to occur in the 9Cr-ODS martensitic steels. The fraction of helium desorption becomes larger at higher temperatures, and this trend is increased with the amount of implanted helium. In the 9Cr-ODS steels, the fraction of helium desorption by bubble migration mechanism was smaller than that in the RAF steel. This suggests that the bubble formation was suppressed in the ODS steels. In the 12Cr-ODS steel, the fraction of helium desorption by bubble migration reached more than 90%, suggesting that the trapping capacity of martensite phase in the 9Cr-ODS steel is rather large.

  2. 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.

  3. Desorption dynamics, internal energies, and imaging of organic molecules from surfaces with laser desorption and vacuum ultraviolet (VUV) photoionization.

    PubMed

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

    2011-11-04

    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 by using laser-desorption VUV postionization shows 5 μm feature details while using a 30 μm laser spot size and 7 ns pulse duration. Applications of laser-desorption postionization to the analysis of cellulose, lignin, and humic acids are briefly discussed.

  4. 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.

  5. 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.

  6. A new theoretical approach to adsorption desorption behavior of Ga on GaAs surfaces

    NASA Astrophysics Data System (ADS)

    Kangawa, Y.; Ito, T.; Taguchi, A.; Shiraishi, K.; Ohachi, T.

    2001-11-01

    We propose a new theoretical approach for studying adsorption-desorption behavior of atoms on semiconductor surfaces. The new theoretical approach based on the ab initio calculations incorporates the free energy of gas phase; therefore we can calculate how adsorption and desorption depends on growth temperature and beam equivalent pressure (BEP). The versatility of the new theoretical approach was confirmed by the calculation of Ga adsorption-desorption transition temperatures and transition BEPs on the GaAs (0 0 1) -(4×2) β2 Ga-rich surface. This new approach is feasible to predict how adsorption and desorption depend on the growth conditions.

  7. Modelling of field desorption of monocrystal nanotip

    NASA Astrophysics Data System (ADS)

    Nikiforov, K. A.; Krasnova, A. A.

    2015-11-01

    Mathematical and computer model of field desorption process from metal nanocrystal tip is proposed. The radius of curvature on the top of the emitter is about 50 lattice parameters. The model includes initial calculation of intersection between the crystal lattice and emitter shape for bcc and fcc crystal structures. Arbitrary axisymmetric shapes (figures of rotation) can be used for the emitter model. The algorithm for allocation of atoms being desorbed at given time step is based on an analysis of geometric environment with specified local electric field. Polyhedron nanostructured shape of emitter is obtained as result of evaporation. Computer program realization (Matlab stand alone application) is presented.

  8. Plume expansion dynamics of matrix-assisted laser desorption ionization.

    PubMed

    Liang, Chi-Wei; Lee, Chih-Hao; Lee, Yuan-Tseh; Ni, Chi-Kung

    2011-11-04

    High-resolution angular and velocity distributions for neutral analytes (tryptophan and poly-tryptophan) and matrix (2,4,6-trihydroxyacetophenon, THAP) are measured by using 355 nm laser desorption. The information suggests that two separate mechanisms dominate the angular and velocity distributions at the beginning and before the end of desorption. A molecular jet-like isentropic expansion dominates the plume expansion at the beginning of desorption. This only occurs at high surface temperature, thus resulting in a large velocity normal to the surface and a very narrow angular distribution. Most of the analytes are produced under these conditions. Before the end of desorption, the surface temperature decreases and the mechanism of thermal desorption at low vapor pressure takes over. The velocities become small and the angular distribution is close to cosθ. Only a very small amount of analytes are generated under these conditions. Compared to tryptophan, poly-tryptophan has a much narrower angular distribution, thereby suggesting that it is only produced at the higher surface temperatures.

  9. Structure of BaO on hierarchical macro-meso-microporous alumina and its effect of interaction with Pt nanoparticle on NO2 desorption.

    PubMed

    Jang, Ik Jun; Shin, Hye Sun; Shin, Na Ra; Kim, Su Hyun; Cho, Sung June

    2011-08-01

    Recently, the lean NOx trap technology using supported Pt catalyst on alumina was devised to store NOx under lean condition and to reduce into N2 and water under rich condition in lean burn engine. In this work, the effect of the Pt nanoparticle supported on hierarchical macro-meso-microporous BaO-Al2O3 on NO2 desorption has been investigated with NO2 temperature programmed desorption, TEM, SEM, TGA and hydrogen chemisorption. Crystalline BaO phase of 20-30 nm thickness were obtained on the hierarchical macro-meso-microporous Al2O3 with a simple impregnation of Ba(NO3)2 and Ba(ClO4)2. The interaction of Pt and BaO was resulted in the formation of atomically dispersed Pt nanoparticles and also decreased the desorption temperature of NO2 adsorbed on BaO at much lower temperature than that from the BaO-Al2O3 support only. This synergistic lowering of NO2 desorption temperature may be originated from the interaction between Pt and BaO.

  10. 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.

  11. 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.

  12. 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.

  13. Water adsorption, desorption, and clustering on FeO(111).

    PubMed

    Daschbach, John L; Dohnalek, Z; Liu, Shu-Rong; Smith, R Scott; Kay, Bruce D

    2005-05-26

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

  14. Thermal desorption from ordered chemisorbed phases studied by helium scattering: Oxygen on Ag(110)

    NASA Astrophysics Data System (ADS)

    Canepa, M.; Terreni, S.; Narducci, E.; Mattera, L.

    1999-01-01

    We relate the helium specular beam intensity during adsorbate desorption (He desorption curve) to the instantaneous surface coverage. In this way the He desorption curve is shown to provide a picture of the desorption process which can be fruitfully compared to the one coming from thermal desorption mass spectra (TDS), obtained under strictly comparable experimental conditions. We tested the combination of thermal energy atom scattering (TEAS) and TDS in the case of the associative desorption from long range ordered O(2×1)-Ag(110) phase. Using the so-called overlap approach and assuming intense adsorbate-adsorbate (and vacancy-vacancy) attractions along Ag-O-Ag rows we obtain an instantaneous coverage which is in good agreement with TDS results. He desorption curves confirm the extreme sharpness of the desorption transition further indicating that the tails of the TDS peak bear small contributions from oxygen which did not belong to the O(2×1) phase. Opportunities and limitations inherent to the use of the He desorption curve (and its first derivative) as a marker of the temperature position and sharpness of the desorption transition are also addressed.

  15. 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

  16. 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.

  17. 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.

  18. Moisture diffusivity in rice components during absorption and desorption

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Moisture diffusivity values of different rice kernel components namely, endosperm, bran and husks are required to solve mathematical models describing absorption and desorption processes. In addition to the rice variety and temperature, the moisture diffusivity also depends on its instantaneous mois...

  19. 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

  20. 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

    Castanheira, Mariana; 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.

  1. 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.

  2. 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.

  3. Hydrogen retention in tungsten materials studied by Laser Induced Desorption

    NASA Astrophysics Data System (ADS)

    Zlobinski, M.; Philipps, V.; Schweer, B.; Huber, A.; Reinhart, M.; Möller, S.; Sergienko, G.; Samm, U.; 't Hoen, M. H. J.; Manhard, A.; Schmid, K.; Textor Team

    2013-07-01

    Development of methods to characterise the first wall in ITER and future fusion devices without removal of wall tiles is important to support safety assessments for tritium retention and dust production and to understand plasma wall processes in general. Laser based techniques are presently under investigation to provide these requirements, among which Laser Induced Desorption Spectroscopy (LIDS) is proposed to measure the deuterium and tritium load of the plasma facing surfaces by thermal desorption and spectroscopic detection of the desorbed fuel in the edge of the fusion plasma. The method relies on its capability to desorb the hydrogen isotopes in a laser heated spot. The application of LID on bulk tungsten targets exposed to a wide range of deuterium fluxes, fluences and impact energies under different surface temperatures is investigated in this paper. The results are compared with Thermal Desorption Spectrometry (TDS), Nuclear Reaction Analysis (NRA) and a diffusion model.

  4. 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.

  5. 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).

  6. Simple sample transfer technique by internally expanded desorptive flow for needle trap devices.

    PubMed

    Eom, In-Yong; Pawliszyn, Janusz

    2008-07-01

    Needle trap devices (NTDs) are improving in simplicity and usefulness for sampling volatile organic compounds (VOCs) since their first introduction in early 2000s. Three different sample transfer methods have been reported for NTDs to date. All methods use thermal desorption and simultaneously provide desorptive flow to transfer desorbed VOCs into a GC separation column. For NTDs having 'side holes', GC carrier gas enters a 'side hole' and passes through sorbent particles to carry desorbed VOCs, while for NTD not having a 'side hole', clean air as desorptive flow can be provided through a needle head by a air tight syringe to sweep out desorbed VOCs or water vapor has been reported recently to be used as desorptive flow. We report here a new simple sample transfer technique for NTDs, in which no side holes and an external desorptive flow are required. When an NTD enriched by a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX) or n-alkane mixture (C6-C15) is exposed to the hot zone of GC injector, the expanding air above the packed sorbent transfers the desorbed compounds from the sorbent to the GC column. This internal air expansion results in clean and sharp desorption profiles for BTEX and n-alkane mixture with no carryover. The effect of desorption temperature, desorption time, and overhead volumes was studied. Decane having vapor pressure of approximately 1 Torr at 20 degrees C showed approximately 1% carryover at the moderate thermal desorption condition (0.5 min at 250 degrees C).

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

    SciTech Connect

    Guohui Wang; Sybille Kleineidam; Peter Grathwohl

    2007-02-15

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

  8. 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.

  9. Enhanced selective hydrogen desorption from metals

    SciTech Connect

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

    1983-04-01

    The thermal desorption of hydrogen isotopes from a metal is usually a second order process the rate for which becomes asymptotically slow. We present a method for enhancing the desorption rate of one particular isotope by maintaining a constant pressure of another molecular species. This results in an effective first order desorption and concommitant exponential decay of the concentration of the selected isotope. Data is presented for the enhanced desorption of deuterium from a Zr--Al getter. The results agree well with a theoretical model, which is discussed. This enhanced desorption method should be particularly useful for tritium operation in the tokamak fusion test reactor.

  10. Enhanced selective hydrogen desorption from metals

    SciTech Connect

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

    1982-12-01

    The thermal desorption of hydrogen isotopes from a metal is usually a second order process, the rate for which becomes asymptotically slow. We present a method for enhancing the desorption rate of one particular isotope by maintaining a constant pressure of another molecular species. This results in an effective first order desorption and concomitant exponential decay of the concentration of the selected isotope. Data are presented for the enhanced desorption of deuterium from a Zr-Al getter. The results agree well with a theoretical model, which is discussed. This enhanced desorption method should be particularly useful for tritium operation in the Tokamak Fusion Test Reactor.

  11. 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.

  12. [Desorption behaviors of 4-nitrophenol on hyper-cross-linked polymer resin NDA-701].

    PubMed

    Hong, Chang-hong; Huang, Ben-sheng; Qiu, Jing; Zhang, Wei-ming

    2011-05-01

    Desorption behaviors of loaded 4-nitrophenol (4-NP) on hyper-cross-linked polymer resin NDA-701 were studied. The molar ratio of NaOH and 4-NP desorbed (M(NAOH/4-NP)) selection experiments were carried out at two different reaction temperature(303 K and 333 K). Desorption kinetics characteristic of4-NP on NDA-701 in the batch and fixed-bed mode were examined at different reaction temperature and M(NaOH/4-NP) values. The results showed that optimal M(NaOH/4-NP) values were 1.2 and 100% 4-NP could be desorbed from NDA-701 at two different temperature. When the M(NaOH/4-NP) was lower than 1.2, the desorption efficiency increases with the increase of temperature, but the function of temperature decrease with increasing of M(NaH/4-NP) values for desorption ratio. The information indicated that desorption thermodynamic characteristic of NDA-701 was controlled by M(NaOH/4-NP) values. Desorption kinetics in the alkaline system can be well described by pseudo-second-order kinetic model, and desorption rate is increased with the increase of desorption temperatures, the k2 value increase from 0.010 g x (mmol x min)(-1) to 0.035 g x (mmol x min)(-1) when desorption temperature increase from 303 K to 333 K. Nevertheless, higher M(NaOH/4-NP) values could not promote desorption rate if only M(NaOH/4-NP) value was larger than the optimal molar ratio of NaOH and 4-NP. When M(NaOH/4-NP) values increase from 1.2 to 5.0, the k2 value increase from 0.038 g x (mmol x min)(-1) to 0.044 g x (mmol x min)(-1) merely at 333 K. the results indicated that desorption kinetic characteristic of NDA-701 was controlled by temperature. NDA-701 can be completely recovered using 2 times Bed Volume of 2% NaOH solution at the temperature of 333 K, comparing with field application, implying that more energy and cost can be saved in comparison with the actual desorption process in the industry.

  13. 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.

  14. Temperature-programmed microwave-assisted synthesis of SBA-15 ordered mesoporous silica.

    PubMed

    Celer, Ewa B; Jaroniec, Mietek

    2006-11-08

    The currently available microwave technology permits the development and implementation of a temperature-programmed microwave-assisted synthesis (TPMS) of ordered mesoporous silicas (OMSs). Unlike in previously reported syntheses of OMSs, in which only the final hydrothermal treatment was carried out under microwave irradiation, this work takes advantage of the existing capabilities of modern microwave systems to program the temperature and time for the entire synthesis of these materials. To demonstrate the flexibility of the proposed microwave-assisted synthesis, besides programming two consecutive steps involving initial stirring of the gel at a lower temperature and static hydrothermal treatment at a higher temperature, we explored the possibility of temperature programming of the latter step. A major advantage of microwave technology is the feasibility of temperature and time programming, which has been demonstrated by the synthesis of one of the most popular OMSs, SBA-15, over an unprecedented range of temperatures from 40 to 200 degrees C. Since the synthesis of OMSs has not yet been explored and reported at temperatures exceeding 150 degrees C, this work is focused on the SBA-15 samples prepared at higher temperatures (such as 160, 180, and even 200 degrees C). These SBA-15 samples show better thermal stability than those synthesized at commonly used temperatures either under conventional or microwave conditions. Moreover, a partial decomposition of the template during high-temperature microwave-assisted syntheses does not compromise the formation of well-ordered SBA-15 materials. This study shows that the simplicity and capability of temperature and time programming in TPMS allows one not only to tune the adsorption and structural properties of OMSs but also to easily screen a wide range of conditions in order to optimize and scale-up their preparation as well as to significantly reduce the time of synthesis from days to hours.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Desorption and ionization mechanisms in desorption atmospheric pressure photoionization.

    PubMed

    Luosujärvi, Laura; Arvola, Ville; Haapala, Markus; Pól, Jaroslav; Saarela, Ville; Franssila, Sami; Kotiaho, Tapio; Kostiainen, Risto; Kauppila, Tiina J

    2008-10-01

    The factors influencing desorption and ionization in newly developed desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS) were studied. Redirecting the DAPPI spray was observed to further improve the versatility of the technique: for dilute samples, parallel spray with increased analyte signal was found to be the best suited, while for more concentrated samples, the orthogonal spray with less risk for contamination is recommended. The suitability of various spray solvents and sampling surface materials was tested for a variety of analytes with different polarities and molecular weights. As in atmospheric pressure photoionization, the analytes formed [M + H](+), [M - H](-), M(+*), M(-*), [M - H + O](-), or [M - 2H + 2O](-) ions depending on the analyte, spray solvent, and ionization mode. In positive ion mode, anisole and toluene as spray solvents promoted the formation of M(+*) ions and were therefore best suited for the analysis of nonpolar compounds (anthracene, benzo[a]pyrene, and tetracyclone). Acetone and hexane were optimal spray solvents for polar compounds (MDMA, testosterone, and verapamil) since they produced intensive [M + H](+) ion peaks of the analytes. In negative ion mode, the type of spray solvent affected the signal intensity, but not the ion composition. M(-*) ions were formed from 1,4-dinitrobenzene, and [M - H + O](-) and [M - 2H + 2O](-) ions from 1,4-naphthoquinone, whereas acidic compounds (naphthoic acid and paracetamol) formed [M - H](-) ions. The tested sampling surfaces included various materials with different thermal conductivities. The materials with low thermal conductivity, i.e., polymers like poly(methyl methacrylate) and poly(tetrafluoroethylene) (Teflon) were found to be the best, since they enable localized heating of the sampling surface, which was found to be essential for efficient analyte desorption. Nevertheless, the sampling surface material did not affect the ionization mechanisms.

  20. 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.

  1. 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.

  2. 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.

  3. 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)

  4. 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.

  5. DESORPTION OF PYRETHROIDS FROM SUSPENDED SOLIDS

    PubMed Central

    Fojut, Tessa L.; Young, Thomas M.

    2014-01-01

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

  6. 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.

  7. 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.

  8. 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,…

  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. Desorption of isopropyl alcohol from adsorbent with non-thermal plasma.

    PubMed

    Shiau, Chen Han; Pan, Kuan Lun; Yu, Sheng Jen; Yan, Shaw Yi; Chang, Moo Been

    2016-11-24

    Effective desorption of isopropyl alcohol (IPA) from adsorbents with non-thermal plasma is developed. In this system, IPA is effectively adsorbed with activated carbon while dielectric barrier discharge is applied to replace the conventional thermal desorption process to achieve good desorption efficiency, making the treatment equipment smaller in size. Various adsorbents including molecular sieves and activated carbon are evaluated for IPA adsorption capacity. The results indicate that BAC has the highest IPA adsorption capacity (280.31 mg IPA/g) under the operating conditions of room temperature, IPA of 400 ppm, and residence time of 0.283 s among 5 adsorbents tested. For the plasma desorption process, the IPA selectivity of 89% is achieved with BAC as N2 is used as desorbing gas. In addition, as air or O2 is used as desorbing gas, the IPA desorption concentration is reduced, because air and O2 plasmas generate active species to oxidize IPA to form acetone, CO2, and even CO. Furthermore, the results of the durability test indicate that the amount of IPA desorbed increases with increasing desorption times and plasma desorption process has a higher energy efficiency if compared with thermal desorption. Overall, this study indicates that non-thermal plasma is a viable process for removing VOCs to regenerate adsorbent.

  11. 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.

  12. 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.

  13. 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.

  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. [Development of a predictive program for microbial growth under various temperature conditions].

    PubMed

    Fujikawa, Hiroshi; Yano, Kazuyoshi; Morozumi, Satoshi; Kimura, Bon; Fujii, Tateo

    2006-12-01

    A predictive program for microbial growth under various temperature conditions was developed with a mathematical model. The model was a new logistic model recently developed by us. The program predicts Escherichia coli growth in broth, Staphylococcus aureus growth and its enterotoxin production in milk, and Vibrio parahaemolyticus growth in broth at various temperature patterns. The program, which was built with Microsoft Excel (Visual Basic Application), is user-friendly; users can easily input the temperature history of a test food and obtain the prediction instantly on the computer screen. The predicted growth and toxin production can be important indices to determine whether a food is microbiologically safe or not. This program should be a useful tool to confirm the microbial safety of commercial foods.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. The decomposition of methanol on Ru(001) studied using laser induced thermal desorption

    NASA Astrophysics Data System (ADS)

    Deckert, A. A.; Brand, J. L.; Mak, C. H.; Koehler, B. G.; George, S. M.

    1987-08-01

    The decomposition reaction of methanol on Ru(001) was studied using laser induced thermal desorption (LITD). The LITD studies, combined with temperature programmed desorption and Auger electron spectroscopy measurements, allowed absolute product yields for the three competing surface pathways to be determined over the entire range of chemisorbed methanol coverages at a heating rate of β=2.6 K/s. At the lowest methanol coverages of θ≤0.07θs, where θs is the surface coverage of a saturated chemisorbed layer, all the methanol reacted between 220-280 K. This methanol decomposition reaction yielded desorption-limited H2 and CO as reaction products. At higher coverages, molecular desorption and the second methanol decomposition reaction involving C-O bond breakage became increasingly important. At θ=θs, 50% of the initial methanol coverage desorbed, 24% produced H2 and CO and 26% left C on the surface. Isothermal LITD kinetic measurements were carried out at low methanol coverages of θ≤0.07θs at various temperatures from 180 to 220 K. The initial decomposition rates obtained from the isothermal LITD studies displayed first order kinetics. The decomposition kinetics at later times could not be fit by first order kinetics and suggested a self-poisoned reaction. Subsequent LITD studies revealed that CO inhibited the decomposition reaction. The product CO inhibition was modeled by first order kinetics with a CO-coverage dependent activation barrier. The observed first order reaction kinetics at low methanol coverage could be expressed by the pre-exponential ν=106 s-1 and the coverage-dependent activation barrier E=7 kcal/mol+αθCO/θCO,s, where α=20 kcal/mol and θCO/θCO,s is the dimensionless CO coverage normalized to the CO saturation coverage θCO,s. Isotopic LITD studies revealed that the decomposition kinetics of CH3OH, CD3OH, and CH3OD were identical. This equivalence suggested that the hindered rotation of the surface methoxy species is the reaction

  2. Water Vapor Desorption Characteristics of Honeycomb Type Sorption Element Composed of Organic Sorbent

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Kida, Takahisa; Horibe, Akihiko; Kaneda, Makoto; Okamoto, Tamio; Seo, Jeong-Kyun

    This paper describes the water vapor desorption characteristics of honeycomb shape type sorbent element containing new organic sorbent of the bridged complex of sodium polyacrylate. The transient experiments in which the dry air was passed into the honeycomb type sorbent element sorbed water vapor were carried out under various conditions of air velocity, temperature, relative humidity and honeycomb length. The obtained data for desorption process were compared with those for sorption process. Finally, Sherwood number of mass transfer of the organic sorbent for desorption process was derived in terms of Reynolds number, modified Stefan number and non-dimensional honeycomb length.

  3. Phase diagram and adsorption-desorption kinetics of CO on Ru(0001) from first principles.

    PubMed

    McEwen, J-S; Eichler, A

    2007-03-07

    A kinetic lattice gas model is used to study the equilibrium properties and the desorption kinetics of CO on Ru(0001). The authors compute all relevant on-site binding and interaction energies of CO molecules within density functional theory and import them in two different models. The first model allows the CO molecules to adsorb upright on top and hollow sites. The authors calculate the phase diagram, coverage isobars, and temperature programed desorption spectra. Up to a coverage of 1/3 ML, very good agreement is obtained between theory and experiment when considering top sites only. For coverages beyond 1/3 ML, hollow sites are included and disagreement between theory and experiment occurs. The second model allows adsorption on top sites only but allows them to tilt and shift from their upright positions. The authors show that this model resolves many of the deficiencies of their first one. Furthermore, the authors demonstrate that this model is more consistent with experiment since it is the only model that is able to explain the results from IR-spectroscopy experiments.

  4. 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

  5. On gas desorption from the tokamak first wall during edge localized modes

    SciTech Connect

    Marenkov, E. D.; Smirnov, R. D.; Krasheninnikov, S. I.

    2013-11-15

    The effect of gas desorption from the tokamak first wall on the pedestal recovery in the H-mode after an edge-localized-mode burst is considered. Results of FACE code simulations of hydrogen desorption from a beryllium wall are presented. It is found that the wall has a significant effect on plasma processes only at sufficiently low temperatures (of about 400 K), which agrees with qualitative estimates obtained earlier in the zero-dimensional approximation.

  6. 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.

  7. Simultaneous programmed temperature GLC assay of phenol, chloroxylenol, and lidocaine hydrochloride in topical antiseptic cream.

    PubMed

    Palermo, P J; Lundberg, J B

    1978-11-01

    A simultaneous programmed temperature GLC assay for the active ingredients in a topical antiseptic cream is described. The sample is extracted directly using a dimethyl sulfoxide solution of p-cresol, 4-chlorophenol, and 2-amino-4-phenylthiazole as internal standards for phenol, chloroxylenol, and lidocaine hydrochloride, respectively. The resulting solution is chromatographed by temperature programming on an OV-225 column from 90 to 225 degrees. The internal standard calculation is accomplished using peak heights or peak areas. The relative standard deviation of all assays is less than 2%.

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

    PubMed

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

    2014-08-01

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

  9. Thermal decomposition of municipal solid waste fly ash and desorption of polychlorinated dibenzo-p-dioxins and furans from fly ash surfaces.

    PubMed

    Weidemann, Eva; Lundin, Lisa; Boily, Jean-François

    2016-11-01

    Surfaces of fly ashes from three Swedish MSW incinerating plants were extensively characterized to better predict their involvement in the generation of persistent organic pollutants. The ashes were then subjected to thermal treatment at 400 °C in sealed glass ampoules to track the decomposition polychlorinated dibenzo-p-dioxins and furans (PCDD and PCDF). Temperature programmed desorption experiments in the 30-900 °C range also enabled monitoring of thermally decomposing ashes by Fourier Transform Infrared (FTIR) spectroscopy as well as thermally desorbing effluent gases by mass spectrometry. In addition, one ash was doped with (13)C-labelled PCDD and PCDF to evaluate the potential of the experimental setup for elucidating the thermal desorption of the organic molecules. It was found that in ashes with high carbon content PCDD and PCDF decomposition were led pronounced, and that PCDD degraded more readily than PCDF.

  10. Reaction pathways for hydrogen desorption from magnesium hydride/hydroxide composites: bulk and interface effects.

    PubMed

    Leardini, F; Ares, J R; Bodega, J; Fernández, J F; Ferrer, I J; Sánchez, C

    2010-01-21

    This manuscript investigates the thermal desorption behaviour of MgH(2)/Mg(OH)(2) composites by means of thermal desorption spectroscopy. Besides the H(2)O and H(2) desorption events due to Mg(OH)(2) dehydration and MgH(2) decomposition reactions, respectively, two additional H(2) desorption peaks arise at lower temperatures. These peaks are related to solid-state reactions between magnesium hydride and magnesium hydroxide through different channels. The low temperature H(2) peak ( approximately 150 degrees C) is related to reaction between a H atom diffusing from MgH(2) and a surface OH group, whereas the intermediate temperature H(2) peak ( approximately 350 degrees C) is due to an interface reaction between the hydride and the hydroxide. The present work supports the theory that the onset of the H(2) desorption coming from MgH(2) decomposition is controlled by an incubation process, consisting in the formation of catalytically active vacancies at the MgO/Mg(OH)(2) surface by dehydration. Possible ways to improve the H(2) desorption kinetics from MgH(2) are discussed in the light of the results obtained.

  11. 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.

  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. 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.

  14. Adsorption and desorption characteristics of arsenic onto ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Feng, Qinzhong; Zhang, Zhiyong; Ma, Yuhui; He, Xiao; Zhao, Yuliang; Chai, Zhifang

    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 (Δ H 0 , Δ S 0 , and Δ G 0 ) 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.

  15. Hydrogen absorption-desorption properties of U 2Ti

    NASA Astrophysics Data System (ADS)

    Takuya, Yamamoto; Satoru, Tanaka; Michio, Yamawaki

    1990-02-01

    Hydrogen absorption-desorption properties of U 2Ti intermetallic compound was examined over the temperature range of 298 to 973 K and at hydrogen pressures below 10 5 Pa. It absorbs hydrogen up to 7.6 atoms per F.U. (formula unit) by two step reactions and hence each desorption isotherm is separated into two plateau regions. In the first plateau, a newly-found ternary hydride is formed, where the hydrogen concentration, cH, reaches 2.4 H atoms/F.U. In the second plateau, UH 3 is formed and cH reaches 7.6 H atoms/F.U. The specimen is disintegrated into fine powder in the second plateau, while in the first plateau the ternary hydride which was identified to be UTi 2H x, ( x = 4.8 to 6.2) showed high durability against powdering. It is predicted that UTi 2 can be suitable material for tritium storage.

  16. A pyrometric feedback system covering the entire temperature program for electrothermal atomization-atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Herber, R. F. M.; Pieters, H. J.; Roelofsen, A. M.; Van Deijck, W.

    A new pyrometric temperature feedback control system for ETA-AAS is introduced which controls the entire temperature range needed for analysis. The system consists of a single infrared sensitive detector and independent feedback control circuitry for the three separate heating stages of a Varian CRA 63 or CRA 90 power supply to which it was added. The temperature region covered by the system encompassed from 300 to 3300 K. The precision of the temperature control amounts to ±20 K at 330 K., ±5 K at 700 K and ±2 K at 2300 K. In order to test the performance of the system, lead in blood and cadmium in urine were determined. Substantial improvements as compared to the conventional system were obtained with respect to optimization of the temperature program, precision and sensitivity. Patent pending.

  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. Gas desorption during friction of amorphous carbon films

    NASA Astrophysics Data System (ADS)

    Rusanov, A.; Fontaine, J.; Martin, J.-M.; Mogne, T. L.; Nevshupa, R.

    2008-03-01

    Gas desorption induced by friction of solids, i.e. tribodesorption, is one of the numerous physical and chemical phenomena, which arise during friction as result of thermal and structural activation of material in a friction zone. Tribodesorption of carbon oxides, hydrocarbons, and water vapours may lead to significant deterioration of ultra high vacuum conditions in modern technological equipment in electronic, optoelectronic industries. Therefore, knowledge of tribodesorption is crucial for the performance and lifetime of vacuum tribosystems. Diamond-like carbon (DLC) coatings are interesting materials for vacuum tribological systems due to their high wear resistance and low friction. Highly hydrogenated amorphous carbon (a-C:H) films are known to exhibit extremely low friction coefficient under high vacuum or inert environment, known as 'superlubricity' or 'superlow friction'. However, the superlow friction period is not always stable and then tends to spontaneous transition to high friction. It is supposed that hydrogen supply from the bulk to the surface is crucial for establishing and maintaining superlow friction. Thus, tribodesorption can serve also as a new technique to determine the role of gases in superlow friction mechanisms. Desorption of various a-C:H films, deposited by PECVD, ion-beam deposition and deposition using diode system, has been studied by means of ultra-high vacuum tribometer equipped with a mass spectrometer. It was found that in superlow friction period desorption rate was below the detection limit in the 0-85 mass range. However, transition from superlow friction to high friction was accompanied by desorption of various gases, mainly of H2 and CH4. During friction transition, surfaces were heavily damaged. In experiments with DLC films with low hydrogen content tribodesorption was significant during the whole experiment, while low friction was not observed. From estimation of maximum surface temperature during sliding contact it was

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  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. 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.

  7. 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.

  8. 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.

  9. Desorption isotherms for fresh beef: an experimental and modeling approach.

    PubMed

    Ahmat, Tom; Bruneau, Denis; Kuitche, Alexis; Waste Aregba, Aworou

    2014-04-01

    Desorption isotherms for fresh beef were determined at 30, 40 and 50°C by the static gravimetric method. The resulting isotherms exhibited a type II sigmoid shape. The BET, GAB and Halsey models were used to fit these experimental data. The GAB model was most accurate for all temperatures and all levels of water activity, followed by the BET and Halsey models. The temperature dependence of GAB constants was estimated. The isosteric heat of desorption and its evolution in relation to moisture content were calculated using Clausius-Clapeyron equations. The monolayer moisture content was determined using the GAB model: it decreased as the temperature increased. The density of bound water, the number of adsorption sites, the sorption surface area and the percentage of bound water were calculated using the Caurie equation: all these quantities decreased as the temperature increased. The Kelvin and Halsey equations were used for calculation of pore size, which increases with an increase in moisture levels and sorption temperature.

  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. 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.

  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. Techniques for wide range, high resolution and precision, thermal desorption measurements. I. Principles of apparatus and operation

    NASA Astrophysics Data System (ADS)

    Schlichting, H.; Menzel, D.

    1993-04-01

    We describe techniques and an apparatus with which thermal desorption measurements, both temperature-programmed and isothermal, can be considerably improved compared to the best measurements done to date. These constitute further development of a previously used scheme (detection of desorbing species in a separate small volume which is pumped by a geometrically defined conductance to the main chamber) by procedures for very accurate resetability of the sample before the cap aperture, and by an accurate correction procedure for readsorption. Direct application of these techniques leads to a range of 4 powers of 10 in rate which can be extended by another power of 10 by a simple background correction. The dynamic range of coverages that can be studied is even larger. The very good reproducibility makes calibration of rates and coverages in absolute terms possible. The high accuracy allows studies of majority species by direct logarithmic plots, of minority species encompassing only promilles of a monolayer, and of sticking coefficients at coverages down to 10 -3 and up to more than 10 monolayers, with high accuracy. While these techniques have been developed for the study of weakly adsorbed species desorbing at very low temperatures (6-100 K), they can be easily adapted to more strongly bound species, as long as the desorption products do not react with the system walls.

  15. 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.

  16. Selective determination of methyl mercury in biological samples by means of programmed temperature gas chromatography.

    PubMed

    Lorenzo, R A; Carro, A; Rubí, E; Casais, C; Cela, R

    1993-01-01

    A programmed temperature gas chromatographic method is presented by which it is possible to carry out routine analysis of methyl mercury in biological samples prepared according to the AOAC official first action recommendations without the need for preliminary treatment of the columns. This method greatly extends the life of the columns as well as the useful time for analysis; it has good linearity and repeatability. With the proposed method a total of 36 samples can be analyzed daily.

  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.

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

    PubMed

    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.

  19. Adsorption and desorption properties of trans-resveratrol on cellulose cotton.

    PubMed

    Takagai, Yoshitaka; Kubota, Toshio; Kobayashi, Hidetoshi; Tashiro, Tomoyasu; Takahashi, Atsushi; Igarashi, Shukuro

    2005-02-01

    The adsorption and desorption properties of trans-Resveratrol (Res) on the cellulose cotton were investigated under various conditions, such as the pH, alcohol percentage, temperature and equilibrium times. Moreover, the acidic-dissociation constants were determined to be pKa1 = 8.01, pKa2 = 9.86 and pKa3 = 10.5 by a curve-fitting method. Also, it was found that the adsorption depended on the temperature and salting effect. On the other hand, the desorptions from cellulose were examined using several kinds of water-miscible organic solvents (methanol, ethanol, acetone and THF).

  20. Temperature-programmed elimination of tritium in coal labeled by tritiated gaseous hydrogen

    SciTech Connect

    Eika W. Qian; T. Horio; I. Putu Sutrisna

    2009-03-15

    The hydrogen exchange of an Argonne Pocahontas No. 3 (POC) coal with tritiated gaseous hydrogen in the presence of a Pt/Al{sub 2}O{sub 3} catalyst was carried out using a fixed-bed reactor at a temperature range of 200-250{sup o}C. Then, the tritiated coal sample was re-exchanged with hydrogen in a gaseous hydrogen atmosphere at different raising temperature rates. The changes in radioactivity of tritium releasing from the tritium-labeled coal sample in the temperature-programmed elimination (TPE) of tritium was monitored by a radioanalyzer in situ. The release profile of tritium was fit using three Gaussian distribution functions in TPE. On the basis of the waveform analysis, the amounts and activation energies of the hydrogen exchange for every type of exchangeable hydrogen were estimated. The values of exchange activation energies are 8.8 {+-} 0.5, 10.7 {+-} 0.5, and 16.3 {+-} 0.5 kcal/mol for three types of exchangeable hydrogen, respectively. The amount of type-I hydrogen was independent of the exchange reaction temperature. In contrast to this, the amount of types II and III of exchangeable hydrogen increased with an increasing exchange temperature, suggesting that the amount of types II and III of hydrogen in the coal is dependent upon the exchange temperature. 35 refs., 8 figs., 5 tabs.

  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

    2014-07-04

    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.

  2. 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.

  3. 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.

  4. 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.

  5. Ionic Adsorption and Desorption of CNT Nanoropes

    PubMed Central

    Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

    2016-01-01

    A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment. PMID:28335306

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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).

  11. 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.

  12. Cesium Sorption/Desorption Experiments with IONSIV(R) IE-911 in Radioactive Waste

    SciTech Connect

    Walker, D.D.

    2001-02-13

    This report describes cesium desorption from IONSIV IE-911 during ambient temperature storage and following temperature increases to 35 and 55 degrees C. This report also describes cesium sorption following return to ambient temperature. The IONSIV IE-911 used in these tests was loaded with cesium from Tank 44F radioactive waste in an ion exchange column test in 1999. Cesium desorbed and resorbed in the presence of Tank 44F waste and simulated waste solutions.

  13. 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.

  14. 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.

  15. 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.

  16. An assessment of the environmental fate of mercury species in highly polluted brownfields by means of thermal desorption.

    PubMed

    Rumayor, M; Gallego, J R; Rodríguez-Valdés, E; Díaz-Somoano, M

    2017-03-05

    High contents of mercury (Hg) have been found in old mining-metallurgy sites occurring a widespread contamination and degradation of the land. The ability to identify the Hg species present in these areas is essential to clarify fate of Hg and its bioavailability and additionally, to be able to parameterize remediation techniques based on thermal desorption in order to carry out a full-scale decontamination of the land. This study has proven the usefulness of a thermal programmed desorption procedure (Hg-TPD) for identifying Hg species in contaminated samples related to mining-metallurgy activities. Hg bound to organic matter (Hg-OM) and to pyrite (Hg-FeS2), HgS red, HgCl2, Hg(0) and HgO were identified in most of waste samples. The absence of mobile Hg species in soils and sediments showed both its re-emission to the atmosphere (Hg(0)) or of its oxidation and lixiviation (HgO and HgCl2) over the years. The results have demonstrated that most of these polluted solids can be remediated by thermal treatment at temperatures ranging between 150 and 600°C. The study evidence that Hg-TPD is useful either for parameterizing a thermal remediation or for identifying the evolution pathways of Hg species in different environmental compartments and in general, for any environmental remediation treatment.

  17. 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.

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

    NASA Technical Reports Server (NTRS)

    McDonald, Gene D.

    2001-01-01

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

  19. A Computer Program to Predict Energy Cost, Rectal Temperature, and Heart Rate Response to Work, Clothing, and Environment

    DTIC Science & Technology

    1975-11-01

    temperature and heart rate response to work , environment , and clothing. The report defines the mathematical basis of the program and presents a brief guide for its use with the HP9810A programmable calculator.

  20. Asphaltene adsorption and desorption from mineral surfaces

    SciTech Connect

    Dubey, S.T. ); Waxman, M.H.

    1991-02-01

    This paper reports results of asphaltene adsorption/desorption on clay minerals, silica, and carbonates. It also describes the effect of adsorbed asphaltenes on rock wettability and a screening pyrolysis-flame-ionization-detection (P-FID) test to evaluate the ability of solvents to remove asphaltene from kaolin and formation core material.

  1. 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.

  2. Laser desorption mass spectrometry for molecular diagnosis

    NASA Astrophysics Data System (ADS)

    Chen, C. H. Winston; Taranenko, N. I.; Zhu, Y. F.; Allman, S. L.; Tang, K.; Matteson, K. J.; Chang, L. Y.; Chung, C. N.; Martin, Steve; Haff, Lawrence

    1996-04-01

    Laser desorption mass spectrometry has been used for molecular diagnosis of cystic fibrosis. Both 3-base deletion and single-base point mutation have been successfully detected by clinical samples. This new detection method can possibly speed up the diagnosis by one order of magnitude in the future. It may become a new biotechnology technique for population screening of genetic disease.

  3. Particle reflection and ion-induced desorption from tungsten surfaces with chemisorbed nitrogen

    NASA Astrophysics Data System (ADS)

    Yamamura, Y.; Kimura, H.

    1987-06-01

    Using the Monte Carlo simulation program ACAT, ion-induced desorption yields of nitrogen chemisorbed on tungsten surfaces and the associated particle reflection coefficients have been calculated for low-energy helium-ions. It is found that both the particle reflection coefficients and the energy distributions of the reflected particles depend strongly on the thickness of the adsorbate layer on the surface if the ion energy is in the threshold regime and that the collision sequence of the near-threshold mechanism includes at least two adsorbate atoms. The ACAT desorption yields are found to be in good agreement with experimental yields.

  4. Particle reflection and ion-induced desorption from tungsten surfaces with chemisorbed nitrogen

    NASA Astrophysics Data System (ADS)

    Yamamura, Y.; Kimura, H.

    Using the Monte Carlo simulation program ACAT, ion-induced desorption yields of nitrogen chemisorbed on tungsten surfaces and the associated particle reflection coefficients have been calculated for low-energy helium-ions. It is found that both the particle reflection coefficients and the energy distributions of the reflected particles depend strongly on the thickness of the adsorbate layer on the surface if the ion energy is in the threshold regime and that the collision sequence of the near-threshold mechanism includes at least two adsorbate atoms. The ACAT desorption yields are found to be in good agreement with experimental yields.

  5. Glyphosate sorption/desorption on biochars – Interactions of physical and chemical processes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    BACKGROUND: Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350°C t...

  6. Infrared laser-induced desorption of NO and CO from alumina substrates

    NASA Astrophysics Data System (ADS)

    Weber, W. H.; Poindexter, B. D.

    1987-09-01

    We present results of laser-induced desorption (LID) experiments using a CO laser on layers of CO and NO physisorbed at low temperature (6-40K) on fire-polished alumina substrates. Resonant LID is observed for NO but not CO. The time-of-flight (TOF) spectra of both molecules agree with Maxwell-Boltzmann distributions and show no additional structure.

  7. 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

  8. 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, ...

  9. 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

    2014-09-08

    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.

  10. 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.

  11. Dynamic Moisture Sorption and Desorption in Fumed Silica-filled Silicone Foam

    SciTech Connect

    Trautschold, Olivia Carol

    2016-09-02

    Characterizing dynamic moisture sorption and desorption in fumed silica-filled silicone foam is necessary for determining material compatibilities and life predictions, particularly in sealed environments that may be exposed to a range of environmental conditions. Thermogravimetric analysis (TGA) and near infrared spectroscopy (NIR) were performed on S5470 fumed silica-filled silicone foam to determine the weight percent of moisture at saturation. Additionally, TGA was used to determine the time, temperature, and relative humidity levels required for sorption and desorption of physisorbed moisture in S5470.

  12. 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.

  13. Experimental verification of a real-time program for the determination of temperature and sag of overhead lines

    SciTech Connect

    Bush, R.A.; Black, W.Z.; Byrd, W.R.; Champion, T.C. III

    1983-07-01

    An outdoor test facility was used to experimentally verify real-time overhead conductor ampacity and sag programs. The facility consists of a 213m span of 26/7 336 kcmil ACSR conductor completely instrumented with 13 thermocouples as well as a sag and tension device. A weather station mounted near mid-span monitors all pertinent weather conditions. The measured conductor temperatures fluctuated significantly along the length of the test span. Spanwise variations in the measured instantaneous temperatures were frequently in excess of 10/sup 0/C for a wide variety of conductor currents and weather conditions. The conductor temperatures predicted by the real-time ampacity program were within 10/sup 0/C of the average measured conductor temperatures for all tests. Measured conductor sags were within 5 percent of values predicted by a real-time sag program. The results of the experimental project show that accurate predictions of real-time conductor temperatures and sags can be achieved by knowing the conductor current, wind speed, wind direction and the ambient air temperature. Therefore, computer programs are capable of predicting conductor temperatures and sags with a minimum amount of weather data provided by a simple and inexpensive weather station. Instrumentation placed on the conductor is not necessary for execution of the ampacity and sag programs.

  14. Estimation of the gelatinization temperature of noodles from water sorption curves under temperature-programmed heating conditions.

    PubMed

    Hasegawa, Ayako; Ogawa, Takenobu; Adachi, Shuji

    2012-01-01

    A novel method in which the water sorption curve is observed under linearly temperature-raising conditions was proposed to estimate the gelatinization temperature of starch-containing foods, it was applied in an estimation of the gelatinization temperatures of dried noodles. The gelatinization temperatures of two kinds of spaghetti, dried at high and low temperature, were 52.3 and 53.1 °C, and those of udon, kishimen, juwari-soba, hachiwari-soba, so-called common soba, Malony(®), and kuzukiri were 57.0, 57.8, 61.1, 59.6, 57.4, 48.4, and 49.1 °C. The gelatinization temperatures estimated by the method were between the onset and peak temperatures obtained by differential scanning calorimetric measurement.

  15. 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.

  16. 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.

  17. 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.

  18. Activation energy of thermal desorption of silicon oxide layers on silicon substrates

    NASA Astrophysics Data System (ADS)

    Enta, Yoshiharu; Osanai, Shodai; Ogasawara, Takahito

    2017-02-01

    Thermal desorption rates of silicon oxide layers, from 20 to 120 nm in thickness, on silicon substrates in vacuum have been accurately obtained from intervals between ring structures formed inside voids on the oxide layers. From the temperature dependence of the desorption rate, the activation energy and frequency factor of the desorption reaction have been derived as a function of the oxide thickness. The obtained values are compared with the previous studies, and as a result, the activation energy is found to be almost constant ( 4 eV) in a wide range of the oxide thickness. The frequency factor decreases as the inverse square of the oxide thickness. The decomposition kinetics of the oxide layer is also discussed from the obtained results.

  19. 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.

  20. Pd Particle Size Effects on Methane Dissociation on MgO-supported Pd Nanoparticles and Desorption Kinetics of Small Alkane Molecules on MgO(100)

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

    Oxide-supported Pd nanoparticle catalysts are active in a variety of reactions involving small alkanes, including low-temperature methane combustion. Temperature programmed desorption (TPD) was used to study the adsorption of small alkane molecules, C_nH_2n+2 (n=1-10), on the MgO(100) surface at low temperatures (24 K). Hydrocarbon molecules are deposited on the surface by a highly collimated molecular beam with a well-defined kinetic energy. The sample is heated at a controlled rate and desorption products are observed by QMS. Adsorption energy increases linearly with alkane chain length with a small y-intercept. Dissociative adsorption probability of methane on MgO-supported Pd particles (<5 nm dia.) is measured by titration of C fragments with molecular oxygen beam. Dissociation probability is observed to increase with decreasing Pd particle size. PNNL is a multiprogram National Laboratory operated for the U.S. Department of Energy by Battelle Memorial Institute under contract DE-AC06-76RLO 1830. SLT supported by a UW/PNNL Joint Institute for Nanotechnology fellowship.

  1. 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

  2. Silver impregnated carbon for adsorption and desorption of elemental mercury vapors.

    PubMed

    Karatza, Despina; Prisciandaro, Marina; Lancia, Amedeo; Musmarra, Dino

    2011-01-01

    The Hg(0) vapor adsorption experimental results on a novel sorbent obtained by impregnating a commercially available activated carbon (Darco G60 from BDH) with silver nitrate were reported. The study was performed by using a fundamental approach, in an apparatus at laboratory scale in which a synthetic flue gas, formed by Hg(0) vapors in a nitrogen gas stream, at a given temperature and mercury concentration, was flowed through a fixed bed of adsorbent material. Breakthrough curves and adsorption isotherms were obtained for bed temperatures of 90, 120 and 150 degrees C and for Hg(0) concentrations in the gas varying in the range of 0.8-5.0 mg/m3. The experimental gas-solid equilibrium data were used to evaluate the Langmuir parameters and the heat of adsorption. The experimental results showed that silver impregnated carbon was very effective to capture elemental mercury and the amount of mercury adsorbed by the carbon decreased as the bed temperature increased. In addition, to evaluate the possibility of adsorbent recovery, desorption was also studied. Desorption runs showed that both the adsorbing material and the mercury could be easily recovered, since at the end of desorption the residue on solid was almost negligible. The material balance on mercury and the constitutive equations of the adsorption phenomenon were integrated, leading to the evaluation of only one kinetic parameter which fits well both the experimentally determined breakthrough and desorption curves.

  3. Enhanced desorption of cesium from collapsed interlayer regions in vermiculite by hydrothermal treatment with divalent cations.

    PubMed

    Yin, Xiangbiao; Wang, Xinpeng; Wu, Hao; Ohnuki, Toshihiko; Takeshita, Kenji

    2017-03-15

    Adsorption of cesium (Cs) on phyllosilicates has been intensively investigated because natural soils have strong ability of immobilizing Cs within clay minerals resulting in difficulty of decontamination. The objectives of present study are to clarify how Cs fixation on vermiculite is influenced by structure change caused by Cs sorption at different loading levels and how Cs desorption is affected by various replacing cations induced at different treating temperature. As a result, more than 80% of Cs was readily desorbed from vermiculite with loading amount of 2% saturated Cs (5.49×10(-3)mmolg(-1)) after four cycles of treatment of 0.01M Mg(2+)/Ca(2+) at room temperature, but less than 20% of Cs was desorbed from saturated vermiculite. These distinct desorption patterns were attributed to inhibition of Cs desorption by interlayer collapse of vermiculite, especially at high Cs loadings. In contrast, elevated temperature significantly facilitated divalent cations to efficiently desorb Cs from collapsed regions. After five cycles of treatment at 250°C with 0.01M Mg(2+), ∼100% removal of saturated Cs was achieved. X-ray diffraction analysis results suggested that Cs desorption was completed through enhanced diffusion of Mg(2+) cations into collapsed interlayer space under hydrothermal condition resulting in subsequent interlayer decollapse and readily release of Cs(+).

  4. 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.

  5. 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)

  6. 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.

  7. High-Throughput Gas Chromatography for Volatile Compounds Analysis by Fast Temperature Programming and Adsorption Chromatography.

    PubMed

    Gras, Ronda; Hua, Yujuan; Luong, Jim

    2017-03-20

    The synergy of combining fast temperature programming capability and adsorption chromatography using fused silica based porous layer open tubular columns to achieve high throughput chromatography for the separation of volatile compounds is presented.A gas chromatograph with built-in fast temperature programming capability and having a fast cool down rate was used as a platform. When these performance features were combined with the high degree of selectivity and strong retention characteristic of porous layer open tubular column technology, volatile compounds such as light hydrocarbons of up to C7 , primary alcohols, and mercaptans can be well separated and analyzed in a matter of minutes. This analytical approach substantially improves sample throughput by at least a factor of ten times when compared to published methodologies. In addition, the use of porous layer open tubular columns advantageously eliminates the need for costly and time-consuming cryogenic gas chromatography required for the separation of highly volatile compounds by partition chromatography with wall coated open tubular column technology.Relative standard deviations of retention time for model compounds such as alkanes from methane to hexane were found to be less than 0.3% (n = 10) and less than 0.5% for area counts for the compounds tested at two levels of concentration by manual injection, namely, 10 and 1000 ppm v/v (n = 10). Difficult separations were accomplished in one single analysis in less than 2 min such as the characterization of seventeen components in cracked gas containing alkanes, alkenes, dienes, branched hydrocarbons, and cyclic hydrocarbons. This article is protected by copyright. All rights reserved.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  10. 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.

  11. 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.

  12. Sonolytic desorption of mercury from aluminum oxide.

    PubMed

    He, Ziqi; Traina, Samuel J; Bigham, Jerry M; Weavers, Linda K

    2005-02-15

    As discrete particles and/or as coatings on other mineral surfaces in natural systems, aluminum (hydr)oxides are efficient sinks for Hg(II). Ultrasound at 20 kHz was applied to enhance the desorption of Hg(II) from aluminum oxide particles (5.0 micromol of Hg g(-1)). Results showed that at short times ultrasound enhanced Hg(II) release at pH 4.0 compared to both that from hydrodynamic mixing and that expected on the basis of the Hg(II) sorption isotherm. The higher the input power of sonication, the higher the desorption of Hg(II). However, with longer times, much less desorption occurred by ultrasound than by hydrodynamic mixing, with mass balance measurements demonstrating that the desorbed Hg(II) was resorbed back to the particles. The particles were characterized to explore the mechanism for resorption of Hg(II) by prolonged sonication. No surface area change was observed even though ultrasound dramatically reduced the particle size and changed the surface morphology. Although a decrease in the point of zero charge (PZC) due to sonication was observed, it was excluded as the primary mechanism for Hg(II) resorption. Hg(II) occlusion by aluminum hydroxide precipitation was supported by X-ray photoelectron spectroscopy results and the formation of solutions supersaturated with AI. Experiments on presonicated particles verified the occlusion theory by ruling out the effects of the surface area and PZC.

  13. Telecommunication system specific to high temperature environment for JAXA Mercury exploration program

    NASA Astrophysics Data System (ADS)

    Toda, Tomoaki; Kamata, Yukio; Kawahara, Kousuke; Maejima, Hironori; Hayakawa, Hajime

    2014-02-01

    BepiColombo is the joint Mercury exploration program between JAXA (Japan Aerospace Exploration Agency) and ESA (European Space Agency). MMO (Mercury Magnetospheric Orbiter) is JAXA's satellite in this program. She requires a telecommunication system that survives a harsh heat environment surrounding Mercury. She will stay in a polar orbit circulating Mercury for a year for continuous observations of Mercury magnetosphere. MMO has an X-band telecommunication system. We newly developed a high gain antenna for the use of her daily operations and wider field of view antennas for critical events. They are ones directly exposed to a high temperature environment of Mercury. The remains of the telecommunication system such as a transponder and a power amplifier were selected from the heritage of our past deep space missions. These instruments are placed inside MMO where a milder environment is expected than the outside. The total telecommunication system has been designed so that it should work through the MMO mission lifetime from the launch in 2016 to the end of the mission in 2025 including an extra year of extension. The system has experienced thermal environmental tests and proved its excellent resistivity to predicted environments. We will discuss these technologies incorporated in MMO and her telecommunication system design.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Gas absorption/desorption temperature-differential engine

    NASA Technical Reports Server (NTRS)

    Miller, C. G.

    1981-01-01

    Continuously operating compressor system converts 90 percent of gas-turbine plant energy to electricity. Conventional plants work in batch mode, operating at 40 percent efficiency. Compressor uses metal hydride matrix on outside of rotating drum to generate working gas, hydrogen. Rolling valve seals allow continuous work. During operation, gas is absorbed, releasing heat, and desorbed with heat gain. System conserves nuclear and fossil fuels, reducing powerplant capital and operating costs.

  19. Role of nano in catalysis: Pd catalyzed H desorption from MgH2

    NASA Astrophysics Data System (ADS)

    Xie, Weiyu; West, Damien; Sun, Yiyang; Zhang, Shengbai

    2012-02-01

    Magnesium hydride (MgH2) is promising for on-board hydrogen (H) storage with the major hurdle being the slow desorption kinetics. H desorption from ball-milled MgH2 peaks at two slightly different temperatures, which further split in the presence of palladium catalyst. It has been experimentally demonstrated that nanostructuring can eliminate the high temperature peak. However, the effect of nanostructuring cannot be explained by thermodynamic destabilization due to quantum size effect. Our first-principles calculation reveals that there exist two reaction pathways for H desorption from MgH2. One involves H vacancy (SV) diffusion at surface, while the other one involves H atom diffusion in bulk. The SV pathway self-terminates as dehydrogenation eventually eliminates the exposed MgH2 region. Therefore, it is size-sensitive and fully functions only when the surface-to-bulk ratio is large, which is available only in nanostructures. Our calculation further shows that the SV pathway significantly lowers the desorption barrier, because it decouples the H transport process with the surface liftoff process and benefits from a fact that diffusion of vacancies at surface can have significantly lower barrier than that in bulk.

  20. 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...

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. CRC Volatility Program on the Effect of Oxygenated Fuels and Altitude on Cold-Start Drivability at Low Ambient Temperatures

    DTIC Science & Technology

    1990-01-01

    t CRC eport No. 569 CRC VOLATILITY PROGRAM ON THE EFFECT OF OXYGENATED FUELS AND ALTITUDE ON COLD-START DRIVEABILITY AT LOW AMBIENT TEMPERATURES...Research Committee of the Coordinating Research Council, Inc. ABSTRACT The 1988 CRC driveability program investigated the effects of altitude and fuel...and gasoline-MTBE blends. The altitude change between the two sites was found to have no statistically significant effect on driveability for the

  10. Measurements and analysis of water adsorption and desorption

    SciTech Connect

    Monazam, E.R.; Shadle, L.J.; Schroeder, K.

    1996-02-01

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

  11. Effect of programmed diurnal temperature cycles on plasma thyroxine level, body temperature, and feed intake of holstein dairy cows

    NASA Astrophysics Data System (ADS)

    Scott, I. M.; Johnson, H. D.; Hahn, G. L.

    1983-03-01

    Holstein cows exposed to simulated summer diurnal ambient temperature cycles of Phoenix, Arizona and Atlanta, Georgia and diurnal modifications of these climates displayed daily cycles fluctuations in plasma thyroxine (T4) and rectal temperatures (Tre). There were daily diurnal changes in T4 and Tre under all simulated climate conditions. Maximal values generally occurred in the evening hours and minimum values in the morning. Although the diurnal rhythm was influenced by the various simulated climates (diurnal modifications) a diurnal rhythm was very evident even under constant conditions at thermoneutral (Tnc) and at cyclic thermoneutral conditions (TN). The major significance of the study is that the initiation of night cooling of the animals at a time when their Tre was highest was most beneficial to maintenance of a TN plasma T4 level. There was a highly significant negative relationship of average T4 and average Tre. There was also a significant negative relationship of feed consumption and average temperature-humidity index (THI). These data suggest that night cooling may be a most effective method to alleviate thermoregulatory limitations of a hot climate on optimal animal performance. Decreasing the night time air temperature (Ta) or THI or increasing the diurnal range allows the cows to more easily dissipate excess body heat accumulated during the day and minimize the thermal inhibition on feed intake, and alterations in plasma T4 and Tre.

  12. Synchrotron radiation stimulated gas desorption from metals

    NASA Astrophysics Data System (ADS)

    Marin, P. C.

    1994-05-01

    The main trends of photon stimulated desorption, from vacuum chamber walls in synchrotron radiation sources and e + e - circular colliders are shortly reminded as well as its relevance to the machine performances. The results of a detailed study performed with a beam of critical energy 3.75 keV on an OFHC test chamber, at the X-ray radiation source, DCI, at Orsay are then presented. Other experiments carried out elsewhere are shortly discussed. In conclusion, a few remarks are made on what could be the future trends in such investigations.

  13. Thermal desorption mass spectrometer for mass metrology.

    PubMed

    Silvestri, Z; Azouigui, S; Bouhtiyya, S; Macé, S; Plimmer, M D; Pinot, P; Tayeb-Chandoul, F; Hannachi, R

    2014-04-01

    This article presents a device for the study of physisorbed elements on polished surfaces (diameter ⩽56 mm) of the kind used in mass metrology. The technique is based on mass spectrometry of molecules desorbed after heating under vacuum of the analyzed surface. We describe a first application of the device to study current and future mass standards in order to understand how their surface reactivity depends on storage conditions, cleaning processes, and polishing methods. Surface contamination analysis by thermal desorption mass spectrometry to examine the effect of cleaning on pure iridium is given as an example.

  14. 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.

  15. 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.

  16. Characterization by temperature-programmed reduction and by temperature-programmed oxidation (TPR-TPO) of chromium (III) oxide-based catalysts: Correlation with the catalytic activity for hydrofluoroalkane synthesis

    SciTech Connect

    Brunet, S.; Requieme, B.; Matouba, E.; Barrault, J.; Blanchard, M.

    1995-03-01

    The catalytic activity of chromium (III) oxide for the fluorination of CF{sub 3}CH{sub 2}Cl (HCFC 133a) is proportional to the number of reversibly oxidized sites. The proportionality coefficient depends on the atmosphere employed during the pretreatment of the catalyst. The temperature-programmed reduction and temperature-programmed oxidation experiments constitute a simple technique that allows the number of reversibly oxidized chromium atoms to be measured. The method of preparation of the chromium hydroxide has little effect on the catalytic properties of chromium (III) oxide. The activation atmosphere and the temperature are essential parameters in the formation of chromium (III) oxide from hydroxide. Indeed, the most active chromium (III) oxide for the fluorination of CF{sub 3}CH{sub 2}Cl is obtained by thermal treatment of hydroxide at 380{degrees}C under nitrogen. 20 refs., 5 figs., 4 tabs.

  17. Molecular mechanism of adsorption/desorption hysteresis: dynamics of shale gas in nanopores

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Wang, FengChao; Liu, He; Wu, HengAn

    2017-01-01

    Understanding the adsorption and desorption behavior of methane has received considerable attention since it is one of the crucial aspects of the exploitation of shale gas. Unexpectedly, obvious hysteresis is observed from the ideally reversible physical sorption of methane in some experiments. However, the underlying mechanism still remains an open problem. In this study, Monte Carlo (MC) and molecular dynamics (MD) simulations are carried out to explore the molecular mechanisms of adsorption/desorption hysteresis. First, a detailed analysis about the capillary condensation of methane in micropores is presented. The influence of pore width, surface strength, and temperature on the hysteresis loop is further investigated. It is found that a disappearance of hysteresis occurs above a temperature threshold. Combined with the phase diagram of methane, we explicitly point out that capillary condensation is inapplicable for the hysteresis of shale gas under normal temperature conditions. Second, a new mechanism, variation of pore throat size, is proposed and studied. For methane to pass through the throat, a certain energy is required due to the repulsive interaction. The required energy increases with shrinkage of the throat, such that the originally adsorbed methane cannot escape through the narrowed throat. These trapped methane molecules account for the hysteresis. Furthermore, the hysteresis loop is found to increase with the increasing pressure and decreasing temperature. We suggest that the variation of pore throat size can explain the adsorption/desorption hysteresis of shale gas. Our conclusions and findings are of great significance for guiding the efficient exploitation of shale gas.

  18. Field desorption of Na and Cs from graphene on iridium

    NASA Astrophysics Data System (ADS)

    Bernatskii, D. P.; Pavlov, V. G.

    2015-08-01

    Field electron and desorption microscopy has been used to study specific features of the field desorption of sodium and cesium ions adsorbed on the surface of iridium with graphene. It was found that adsorbed sodium atoms most strongly reduce the work function on graphene islands situated over densely packed faces of iridium. A strong electric field qualitatively similarly affects the sodium and cesium desorption processes from a field emitter to give two desorption phases and has no noticeable effect on the disintegration of the graphene layer.

  19. Absorption-Desorption Compressor for Spaceborne/Airborne Cryogenic Refrigerators.

    DTIC Science & Technology

    Refrigerant compressors, *Refrigeration systems), Spaceborne, Airborne, Cryogenics, Gases, Absorption, Desorption, Hydrogen, Hydrides, Lanthanum compounds, Nickel alloys, Joule Thomson effect , Heat transfer

  20. 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.

  1. 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.

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

    PubMed

    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 → CO(2) 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. E 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 CO(2) production disappears. When the impurities are allowed to desorb, there are regions where the CO(2) 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.

  3. Desorption of polycyclic aromatic hydrocarbons from a soot surface: three- to five-ring PAHs.

    PubMed

    Guilloteau, Angélique; Bedjanian, Yuri; Nguyen, Mai Lan; Tomas, Alexandre

    2010-01-21

    The kinetics of the thermal desorption of a set of three- to five-ring polycyclic aromatic hydrocarbons (PAHs) from a laboratory-generated kerosene soot surface was studied over the temperature range 250-355 K in a low-pressure flow reactor combined with an electron-impact mass spectrometer. Two methods were used to measure the desorption rate constants: monitoring of the surface-bound PAH decays due to desorption using off-line HPLC measurements of their concentrations in soot samples and monitoring of the desorbed molecules (anthracene and phenanthtrene) in the gas phase using in situ mass spectrometric detection. The Arrhenius parameters (A factors and activation energies) for the desorption rate constants of 10 soot-bound PAHs were determined. The PAH-soot binding energies were found to be similar for PAHs with the same number of carbon atoms and to increase with increasing number of PAH carbon atoms. The experimental data are discussed in the frame of the existing theoretical gas to particle partitioning model.

  4. 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.

  5. Sorption and desorption studies on chitin gels.

    PubMed

    Vachoud, L; Zydowicz, N; Domard, A

    2001-01-10

    The aim of this work was to study various transport phenomena in chitin gels obtained by N-acetylation of chitosan in a water-alcohol mixture. Three kinds of transport were investigated: the sorption of solutes interacting with chitin, the desorption of solutes without significant interaction with the polymer, and osmosis phenomena. In the case of interactive sorption, dyes having different chemical structures such as C.I. Acid Blue 74, C.I. Reactive Violet 5 or C.I. Direct Red 28 were tested. Sorptions of C.I. Acid Blue 74 and C.I. Reactive Violet 5 depend on the charge density of the polymer network and, as a consequence, on DA, pH and the dielectric constant of the media. This result reveals the importance of electrostatic interactions. On the other hand, the sorption of C.I. Direct Red 28 is mainly due to hydrophobic interactions and H-bonding, it is limited to the extreme surface of the gel. Concerning the non-interactive desorption, solutes of different steric hindrance such as PP vitamin, B1 vitamin and caffeine exhibit similar diffusion coefficients located within 3.7-5.6x10(-6) cm(2) s(-1). Finally, the osmotic behaviour of the gel immersed in a concentrated solution of gelatin allows us to multiply by 25 the concentration of chitin in the gel without any penetration of gelatin.

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

    PubMed

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

    2009-02-11

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

  7. Desorption of the NEG-coated Aluminum Chamber

    NASA Astrophysics Data System (ADS)

    Hsiung, G. Y.; Cheng, C. M.; Yang, C. Y.; Chan, C. K.; Chen, J. R.

    2009-03-01

    The NEG-coating, composed of ZrTiV with a lower temperature of activation, has been developed as a large surface getter pump for the aluminum (Al) chamber of small aperture and long length with a very poor conductance. However, the outgas of discharged gases, Ar or Kr, as well as the hydrocarbon molecules inside the NEG-coated Al chamber has been observed. The desorption of the so-called inert gases with heavier atomic mass residing inside the chamber results in the potential problem of higher cross section of scattering with the traveling beam hence reduces the life time seriously. To verify the outgas source of CH4, the NEG-coated Al-chamber exposed with heavy water (D2O) has been investigated. It shows the D2O and methane are the only outgases from the non-coated Al chamber exposed with D2O. However, more outgas of CDxHy, CD4, and the C2DxHy complexes have been measured in the case of NEG-coated Al chamber. Desorption of C2DxHy molecules can be reduced by exposing the NEG-coated surface with synchrotron radiation photons. The fact of beam cleaning effect verifies the source of C2DxHy molecules are produced and desorbed from the NEG film. The NEG-coated stainless steel (SS) chambers exposed with either D2O or H2O illustrate the similar results in the case of Al-chambers. The dissociation of D2O exposed on the NEG surface for both Al- and SS-chambers are confirmed. The chemical compounds of CmDx and CmDxHy are found produced and desorbed from the NEG-coated after baking and activation.

  8. Use of thermal desorption GC-MS to characterize packaging materials for potential extractables.

    PubMed

    Zweiben, Cindy; Shaw, Arthur J

    2009-01-01

    This article presents case studies involving the use of thermal desorption gas chromatography-mass spectrometry to compositionally characterize pharmaceutical packaging materials for potential extractables. Knowledge of potential extractables and leachables early in the product development program allows the project team to make informed decisions, potentially minimizing redevelopment efforts and reducing cost. Case studies include selection of a label for use on a polyethylene bottle, selection of a drug contact surface of a blister packaging system, and selection of a stopper.

  9. Water adsorption-desorption isotherms of two-dimensional hexagonal mesoporous silica around freezing point.

    PubMed

    Endo, Akira; Yamaura, Toshio; Yamashita, Kyohei; Matsuoka, Fumio; Hihara, Eiji; Daiguji, Hirofumi

    2012-02-01

    Zr-doped mesoporous silica with a diameter of approximately 3.8 nm was synthesized via an evaporation-induced self-assembly process, and the adsorption-desorption isotherms of water vapor were measured in the temperature range of 263-298 K. The measured adsorption-desorption isotherms below 273 K indicated that water confined in the mesopores did not freeze at any relative pressure. All isotherms had a steep curve, resulting from capillary condensation/evaporation, and a pronounced hysteresis. The hysteresis loop, which is associated with a delayed adsorption process, increased with a decrease in temperature. Furthermore, the curvature radius where capillary evaporation/condensation occurs was evaluated by the combined Kelvin and Gibbs-Tolman-Koening-Buff (GTKB) equations for the modification of the interfacial tension due to the interfacial curvature. The thickness of the water adsorption layer for capillary condensation was slightly larger, whereas that for capillary evaporation was slightly smaller than 0.7 nm.

  10. 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.

  11. 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.

  12. Critical Temperature Programs for Surface Carbonization of Si(111) and Their Effects on 3C-SiC Film Growth

    NASA Astrophysics Data System (ADS)

    Giang Nguyen, Nam; Liu, Chie-Sheng; Hu, Ming-Shien; Hong, Lu-Sheng

    2013-08-01

    We have studies of the changes in the surface states of carbonized Si(111) substrates treated under various temperature programs prior to high-temperature 3C-SiC film growth in a low pressure chemical vapor deposition system using SiH4, C2H2, and H2 as reactant gases. The carbonized Si surface underwent a change in bonding from SiC to disordered graphite, together with the formation of etch pits, when heated directly from the carbonization temperature of 1343 K to the growth temperature of 1523 K under a H2 flow over a period of 5 min; this transformation deteriorated the quality of the subsequent 3C-SiC growth. In contrast, a void-free stoichiometric SiC surface was preserved when we inserted a rapid cooling step, to near room temperature, under a H2 flow of 352 sccm within a period of 15 min after shutting off the C2H2 gas flow at the end of the surface carbonization process. The sharp temperature decrease in this program sealed off the carbonized substrate surface and, thus, led to a high film quality for subsequent 3C-SiC(111) growth.

  13. Desorption of hydrogen from Ni—Cu—Cr catalyst on (θ + α-Al2O3 sorbent modified with cerium

    NASA Astrophysics Data System (ADS)

    Dossumov, K.; Popova, N. M.; Salakhova, R. Kh.; Tungatarova, S. A.; Shapovalov, A. A.; Umbetkaliev, A. K.

    2010-03-01

    We present the results of thermal desorption studies of H2 interactions with 8.9% Ni—Cu—Cr (1:3:0.1)/(θ+α)-Al2O3+2% Ce. It was demonstrated that three forms of hydrogen with different desorption temperatures and Tmax peak values are formed in the catalyst at 673 K: H2(ads), H(ads), and dissolved hydrogen. It was found that upon an increase in the adsorption temperature from 673 to 1173 K, H2(ads) and H(ads) remain on the surface (Edes = 14.4 kcal/mol, first order desorption reaction, H: Ni = 1.6—1.88) while hydrogen dissolution in the Ni lattice and its copper alloy increases (Edes= 32.9 kcal/mol, second order desorption reaction, H: Ni = 2.0).

  14. 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.

  15. New instrumentation for temperature measurement. Phase 1: Program solicitation, small business innovation research

    NASA Astrophysics Data System (ADS)

    Fergason, J. L.

    1980-08-01

    Temperature sensitive liquid crystals designed to meet the need for a measuring device to accurately measure temperature and temperature distribution in the presence of electric, magnetic, and sonic fields, especially with high space and thermal resolution are discussed. A technique was developed to make highly reproducible, stable configurations of liquid crystal encapsulates. Temperature stable sensors have been produced which can be calibrated to the National Bureau of Standards. The thermal properties of the liquid crystal can be matched to the properties of the surrounding medium. Since a two dimensional representation of the temperature distribution is possible, the use of this instrumentation has significant implications for bioengineering.

  16. Desorption kinetics of ciprofloxacin in municipal biosolids determined by diffusion gradient in thin films.

    PubMed

    D'Angelo, E; Starnes, D

    2016-12-01

    Ciprofloxacin (CIP) is a commonly-prescribed antibiotic that is largely excreted by the body, and is often found at elevated concentrations in treated sewage sludge (biosolids) at municipal wastewater treatment plants. When biosolids are applied to soils, they could release CIP to surface runoff, which could adversely affect growth of aquatic organisms that inhabit receiving water bodies. The hazard risk largely depends on the amount of antibiotic in the solid phase that can be released to solution (labile CIP), its diffusion coefficient, and sorption/desorption exchange rates in biosolids particles. In this study, these processes were evaluated in a Class A Exceptional Quality Biosolids using a diffusion gradient in thin films (DGT) sampler that continuously removed CIP from solution, which induced desorption and diffusion in biosolids. Mass accumulation of antibiotic in the sampler over time was fit by a diffusion transport and exchange model available in the software tool 2D-DIFS to derive the distribution coefficient of labile CIP (Kdl) and sorption/desorption rate constants in the biosolids. The Kdl was 13 mL g(-1), which equated to 16% of total CIP in the labile pool. Although the proportion of labile CIP was considerable, release rates to solution were constrained by slow desorption kinetics (desorption rate constant = 4 × 10(-6) s(-1)) and diffusion rate (effective diffusion coefficient = 6 × 10(-9) cm(2) s(-1). Studies are needed to investigate how changes in temperature, water content, pH and other physical and chemical characteristics can influence antibiotic release kinetics and availability and mobility in biosolid-amended soils.

  17. 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.

  18. Desorption of pentachlorophenol from soils using mixed solvents

    SciTech Connect

    Khodadoust, A.P.; Suidan, M.T.; Sorial, G.A.; Dionysiou, D.D.; Brenner, R.C.

    1999-12-15

    Desorption of pentachlorophenol (PCP) from contaminated soils in mixed solvents of water and ethanol was investigated using desorption isotherm experiments. The following cosolvent volume fractions of ethanol in the mixed solvent were considered: 0.03, 0.56, 0.79. 0.95, and 1.0. Three fractions of a synthetic soil (Edison soil) with approximately 1% organic matter were the main soils used in this study in addition to K-10 montmorillonite clay and Ottawa sand. The effect of soil organic matter and soil surface area on desorption in mixed solvents was evaluated. Analysis of desorption data revealed that PCP desorption increased with PCP solubility in mixed solvent up to 0.79, 0.95, and 0.56 fraction ethanol for Edison soil, K-10 montmorillonite, and Ottawa sand, respectively. Lower desorption of PCP from Edison soil in solvents with more than 0.79 fraction ethanol resulted from interactions between solvent and soil organic matter. For Edison soil, highest PCP desorption in all mixed solvents was obtained for the soil fraction with the smallest surface area. Desorption of PCP in mixed solvents containing more than 0.79 fraction ethanol was lower for soils with organic matter than for other soils.

  19. Kinetics of alkanethiol monolayer desorption from gold in air.

    PubMed

    Shadnam, Mohammad Reza; Amirfazli, A

    2005-10-14

    Thermal desorption of an alkanethiol monolayer from a gold substrate into a gaseous medium under ambient pressure was investigated using XPS and it was found that there exist 2 consecutive 1st order kinetics mechanisms with activation energies of 29.9 and 32.7 kcal mol(-1), respectively, i.e. on average approximately 15% higher than reports for liquid media desorption.

  20. 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...

  1. Desorption/ionization on silicon nanowires.

    PubMed

    Go, E P; Apon, J V; Luo, G; Saghatelian, A; Daniels, R H; Sahi, V; Dubrow, R; Cravatt, B F; Vertes, A; Siuzdak, G

    2005-03-15

    Dense arrays of single-crystal silicon nanowires (SiNWs) have been used as a platform for laser desorption/ionization mass spectrometry of small molecules, peptides, protein digests, and endogenous and xenobiotic metabolites in biofluids. Sensitivity down to the attomole level has been achieved on the nanowire surfaces by optimizing laser energy, surface chemistry, nanowire diameter, length, and growth orientation. An interesting feature of the nanowire surface is that it requires lower laser energy as compared to porous silicon and MALDI to desorb/ionize small molecules, therefore reducing background ion interference. Taking advantage of their high surface area and fluid wicking capabilities, SiNWs were used to perform chromatographic separation followed by mass analysis of the separated molecules providing a unique platform that can integrate separation and mass spectrometric detection on a single surface.

  2. 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.

  3. 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.

  4. Copper desorption from Gelidium algal biomass.

    PubMed

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

    2007-04-01

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

  5. 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

  6. Automated calculation of vertical pore-water flux from field temperature time series using the VFLUX method and computer program

    NASA Astrophysics Data System (ADS)

    Gordon, Ryan P.; Lautz, Laura K.; Briggs, Martin A.; McKenzie, Jeffrey M.

    2012-02-01

    SummaryHeat is a useful tracer for quantifying groundwater-surface water interaction, but analyzing large amounts of raw thermal data has many challenges. We present a computer program named VFLUX, written in the MATLAB computing language, for processing raw temperature time series and calculating vertical water flux in shallow sub-surface-water systems. The step-by-step workflow synthesizes several recent advancements in signal processing, and adds new techniques for calculating flux rates with large numbers of temperature records from high-resolution sensor profiles. The program includes functions for quantitatively evaluating the ideal spacing between sensor pairs, and for performing error and sensitivity analyses for the heat transport model due to thermal parameter uncertainty. The program synchronizes and resamples temperature data from multiple sensors in a vertical profile, isolates the diurnal signal from each time series and extracts its amplitude and phase angle information using Dynamic Harmonic Regression (DHR), and calculates vertical water flux rates between multiple sensor pairs using heat transport models. Flux rates are calculated every 1-to-2 h using four similar analytical methods. One or more "sliding analysis windows" can be used to automatically identify any number of variably spaced sensor pairs for flux calculations, which is necessary when a single vertical profile contains many sensors, such as in a high-resolution fiber-optic distributed temperature sensing (DTS) profile. We demonstrate the new method by processing two field temperature time series datasets collected using discrete temperature sensors and a high-resolution DTS profile. The analyses of field data show vertical flux rates significantly decreasing with depth at high-spatial resolution as the sensor profiles penetrate shallow, curved hyporheic flow paths, patterns which may have been obscured without the unique analytical abilities of VFLUX.

  7. 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.

  8. Sorption-desorption behavior of phenanthrene elucidated by pyrolysis-gas chromatography-mass spectrometry studies of soil organic matter

    SciTech Connect

    Schultz, L.F.; Young, T.M.; Higashi, R.M.

    1999-08-01

    Commonly used partitioning models of hydrophobic organic contaminant sorption in soil, which treat all soil organic matter (SOM) as having identical structure, are unable to explain differences in organic carbon-normalized sorption coefficients (K{sub OC}) among sorbents, isotherm nonlinearity, and sorption-desorption hysteresis. This study relates one index of SOM composition, structural fragments quantified by pyrolysis-gas chromatography-mass spectrometry, to aqueous and supercritical carbon dioxide (SC CO{sub 2}) sorption-desorption parameters. Results show positive correlations between aqueous K{sub OC}s and hydrocarbon fragment peak areas and negative correlation to N- and O-containing peaks, which is consistent with hypotheses attributing sorption of phenanthrene to hydrophobic sorbent domains. Positive correlation between Freundlich n values in SC CO{sub 2} and hydrocarbon fragments with negative correlation to N- and O-containing fragments suggests that energetic heterogeneity of polar environments controls nonlinearity in this solvent of limited polarity. Aqueous sorption-desorption hysteresis appears to be suppressed by N- and O-containing moieties and correlates with decreased thermal desorption of phenanthrene at 800 C. The SC CO{sub 2} extraction efficiency and, to a lesser degree, the desorption response when methanol is added as a cosolvent indicate that polar functional groups play a role in retarding phenanthrene desorption during SC CO{sub 2} extraction. Organic matter pyrolysis under varying time and temperature conditions indicates that pyrolysis fragments that do not significantly correlated with functional trends likely evolve by a different pyrolytic mechanism and are generally poorly correlated with sorption-desorption properties. The level of structural detail utilized in structure-function correlations in this work exceeds previous efforts to relate sorption behavior to sorbent structure. However, the work reveals that certain sorption

  9. 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.

  10. 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.

  11. Quantitation of berberine chloride in human urine by use of selected ion monitoring in the field desorption mode.

    PubMed

    Miyazaki, H; Shirai, E; Ishibashi, M; Hosoi, K; Shibata, S; Iwanaga, M

    1978-10-01

    A method is described for the microdetermination of berberine chloride in human urine by a field desorption mass spectrometry selected ion monitoring system using a deuterium labelled analogue of berberine chloride as an internal standard. Prior to the quantitation of berberine in human urine, the fundamental problems related to field desorption selected ion monitoring, such as quality of emitters, amounts of sample loading, and the programming rate of the emitter current, were statistically investigated in detail. Berberine chloride can be determined in a concentration of 10 ng ml-1 in human urine by the method described. The analytical results were compared with those from gas chromatography mass spectrometry selected ion monitoring in the chemical ionization mode suggesting that the reliability of field desorption selected ion monitoring may be almost equivalent to that of gas chromatography chemical ionization selected ion monitoring.

  12. Low coverage spontaneous etching and hyperthermal desorption of aluminum chlorides from Cl2/Al(111).

    PubMed

    Grassman, Tyler J; Poon, Gary C; Kummel, Andrew C

    2004-11-08

    Nonresonant multiphoton ionization with time-of-flight mass spectrometry has been used to monitor the desorption of aluminum chloride (Al(x)Cl(y)) etch products from the Al(111) surface at 100 and 500 K during low-coverage (<5% monolayer) monoenergetic Cl(2) (0.11-0.65 eV) dosing. The desorption products in this low-coverage range show predominantly hyperthermal exit velocities under all dosing conditions. For example, with 0.27 eV incident Cl(2), the etch product was found to have a most-probable velocity of 517+/-22 m/s at an Al(111) surface temperature of 100 K. This corresponds to 22 times the expected thermal desorption translational energy for AlCl(3). Cl(2) sticking probability measurements and Al(x)Cl(y) etch rate measurements show etching even at Cl(2) coverages of less than 5% monolayer at surface temperatures between 100 and 500 K. These experimental results are consistent with a combination of fast-time-scale surface diffusion and agglomeration of the adsorbed chlorine to form aluminum chlorides and the presence of activated AlCl(3) chemisorption states having potential energies above the vacuum level. Density functional theory calculations yield results that are consistent with both our experimental findings and mechanistic descriptions.

  13. 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.

  14. Precursor ion scan profiles of acylcarnitines by atmospheric pressure thermal desorption chemical ionization tandem mass spectrometry.

    PubMed

    Paglia, Giuseppe; D'Apolito, Oceania; Corso, Gaetano

    2008-12-01

    The fatty acyl esters of L-carnitine (acylcarnitines) are useful biomarkers for the diagnosis of some inborn errors of metabolism analyzed by liquid chromatography/tandem mass spectrometry. In this study the acylcarnitines were analyzed by atmospheric pressure thermal desorption chemical ionization using a commercial tandem mass spectrometer (APTDCI-MS/MS). The method is based on the precursor ion scan mode determination of underivatized acylcarnitines desorbed from samples by a hot desolvation gas flow and ionized by a corona pin discharge. During desorption/ionization step the temperature induces the degradation of acylcarnitines; nevertheless, the common fragment to all acylcarnitines [MH-59](+) is useful for analyzing their profile. APTDCI parameters, including angle of collection and incidence, gas flows and temperatures, were optimized for acylcarnitines. The experiments were performed drying 2 microL of an equimolar mixture of acylcarnitine standards on a glass slide. The specificity was evaluated by comparing product ion spectra and the precursor ion spectra of 85 m/z of acylcarnitines obtained by the APTDCI method and by electrospray ionization flow injection analysis (ESI-FIA). The method was also employed to analyze acylcarnitines extracted from a pathological dried blood spot and a control. The method enables analysis of biological samples and recognition of some acylcarnitines that are diagnostic markers of inherited metabolic diseases. The intrinsic high-throughput analysis of the ambient desorption ionization methods offers a new opportunity either for its potential application in clinical chemistry and for the expanded screening of some inborn errors of metabolism.

  15. 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.

  16. Techniques for improving the accuracy of cyrogenic temperature measurement in ground test programs

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Fabik, Richard H.

    1993-01-01

    The performance of a sensor is often evaluated by determining to what degree of accuracy a measurement can be made using this sensor. The absolute accuracy of a sensor is an important parameter considered when choosing the type of sensor to use in research experiments. Tests were performed to improve the accuracy of cryogenic temperature measurements by calibration of the temperature sensors when installed in their experimental operating environment. The calibration information was then used to correct for temperature sensor measurement errors by adjusting the data acquisition system software. This paper describes a method to improve the accuracy of cryogenic temperature measurements using corrections in the data acquisition system software such that the uncertainty of an individual temperature sensor is improved from plus or minus 0.90 deg R to plus or minus 0.20 deg R over a specified range.

  17. Laser-induced desorption of overlayer films off a heated metal substrate

    NASA Astrophysics Data System (ADS)

    Gu, Xiang; Urbassek, Herbert M.

    2007-02-01

    The temperature-induced desorption of adsorbed overlayer films with thicknesses between 4 and 200 ML off a suddenly heated metal substrate is studied using molecular-dynamics simulation. We observe that the rapid heating vaporizes the surface-near part of the overlayer film. The initial heating-induced thermoelastic pressure and the vapor pressure in the vapor film drive the remaining film as a large relatively cold cluster away from the surface. In our simulations, the material present in the developing vapor film amounts to roughly 2 ML and is quite independent of the overlayer film thickness. For cluster thicknesses beyond 40 ML, the desorption time increases only little with film thickness, while the resulting cluster velocity decreases only slightly.

  18. Effect of Titanium Doping of Al(111) Surfaces on Alane Formation Mobility, and Desorption

    SciTech Connect

    Chopra I. S.; Graetz J.; Chaudhuri, S.; Veyan, J.-F.; Chabal, Y. J.

    2011-07-05

    Alanes are critical intermediates in hydrogen storage reactions for mass transport during the formation of complex metal hydrides. Titanium has been shown to promote hydrogen desorption and hydrogenation, but its role as a catalyst is not clear. Combining surface infrared (IR) spectroscopy and density functional theory (DFT), the role of Ti is explored during the interaction of atomic hydrogen with Ti-doped Al(111) surfaces. Titanium is found to reduce the formation of large alanes, due to a decrease of hydrogen mobility and to trapping of small alanes on Ti sites, thus hindering oligomerization. For high doping levels ({approx}0.27 ML Ti) on Al(111), only chemisorbed AlH{sub 3} is observed on Ti sites, with no evidence for large alanes. Titanium also dramatically lowers the desorption temperature of large alanes from 290 to 190 K, due to a more restricted translational motion of these alanes.

  19. Power and Thermal Technologies for Air and Space-Scientific Research Program. Delivery Order 0012: High-Temperature Superconductor Performance Enhancement

    DTIC Science & Technology

    2010-06-01

    AFRL-RZ-WP-TR-2010-2167 POWER AND THERMAL TECHNOLOGIES FOR AIR AND SPACE‒SCIENTIFIC RESEARCH PROGRAM Delivery Order 0012: High -Temperature...AND SUBTITLE POWER AND THERMAL TECHNOLOGIES FOR AIR AND SPACE‒SCIENTIFIC RESEARCH PROGRAM Delivery Order 0012: High -Temperature Superconductor...electrically connect them to the substrate. 4) Develop improved measurement techniques and standards of measurement for properties of high temperature

  20. 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.

  1. The relationship between water vapor absorption and desorption by phospholipids and bilayer phase transitions.

    PubMed

    Mansour, Heidi M; Zografi, George

    2007-02-01

    Water vapor absorption and desorption at 25 degrees C and phase transition temperatures of phospholipid bilayers were measured as a function of relative humidity (RH) to better understand how the patterns of water vapor absorption and desorption are linked to corresponding phase changes induced by the level of hydration. Comparisons were made of the dipalmitoyl and palmitoyloleyol esters of glycerol derivatized with phosphatidyl-choline, -glycerol, -ethanolamine and with phosphatidic acid. The results suggest that the extent of water vapor absorption and desorption at a given RH reflects the combined effects of water-polar group interaction and access of water to the polar region as controlled by intra- and interbilayer molecular packing and intermolecular attractive and repulsive interactions. The results further suggest that the extent of water vapor absorption and desorption over a range of relative humidities reflects the combined effects of the polar group's ability to interact with water, the access that water has to the polar groups as determined by molecular size and various intermolecular and intrabilayer forces of attraction and repulsion, and interbilayer interactions which influence the degree of order/disorder present in the overall solid-state structure. This behavior is also reflected in the changes observed in the various bilayer phase transition temperatures as a function of RH. Analyses of absorption isotherms suggests that after exceeding a critical RH, water initially interacting with these phospholipids most likely forms either stoichiometric or nonstoichiometric crystal hydrates, as with the disaturated derivatives, or hydrated mesophases, as with the gel states of the monounsaturated derivatives.

  2. [Desorption of polycyclic aromatic hydrocarbons in soils assisted by SPMD].

    PubMed

    Sun, Hong-Wen; Huo, Chong; Wang, Cui-Ping

    2007-08-01

    In order to develop a new method to study the desorption and bioavailability of hydrophobic organic chemicals (HOCs) in soils, a method using semi-permeable membrane device (SPMD) to study desorption of HOCs in soils has been set up, and assisted desorption of polycyclic aromatic hydrocarbons (PAHs), phenanthrene(PHE), pyrene(PYE), and benzo[a] pyrene (B[a]PYE) in three different kinds of soils was studied using SPMD. The results show that SPMD is a good measurement to study the desorption and bioavailability of HOCs in soils. SPMD assisted desorption of PAHs is highly dependent on the properties of the soils and the chemicals. PHE and PYE desorption percentages increase with the reduction of the content of soil organic matter (SOM), so that the desorption of the two chemicals increases from 56.45% and 48.28% to almost 100% when SOM content was reduced from 18.68% to 0.3%. However, clay has a significant holding effect on B[a]PYE, and PYE desorption is only 66.97% in Soil 3 with SOM of 0.3% and clay content of 39.05%. There is a great variety in the desorption among the different PAHs. With the reduction of SOM content and the elevation of contamination concentration, the difference between PHE and PYE decreases gradually, while B[a]PYE exhibits a significant difference from them. This could be attributed to the high lipophilicity and large molecular size of B[a]PYE, which make the molecule of B[a]PYE to be more easier to be held in the nanopores of clay and the dense region of SOM.

  3. 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.

  4. 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).

  5. Behavior of Materials at Cold Regions Temperatures. Part 1. Program Rationale and Test Plan

    DTIC Science & Technology

    1988-07-01

    10 15 i" 0% I 0 0 0 2 3 4 5a 0 1 2 3 4 5 6 7 lf CSTRAIN (IN/INbST AI OW N V, Figure B47. Static stress vs strain curves for resilient expanded ... polystyrene foam (Resilo-Pak) , at temperature extremes (0.5, 0. 75 and 1.3 lb Ifft3 densities) (Titus 1967). so ,eSF 50 -- 8 * TEMPERATURE. K 0 so 100 is

  6. 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.

  7. Programmed water-induced shape-memory of bioabsorbable poly(D,L-lactide): activation and properties in physiological temperature.

    PubMed

    Paakinaho, K; Heino, H; Pelto, M; Hannula, M; Törmälä, P; Kellomäki, M

    2012-03-01

    This study reports of the novel water-induced shape-memory of bioabsorbable poly(D,L-lactide). We have developed an orientation-based programming process that generates an ability for poly(D,L-lactide) to transform its shape at 37°C in an aqueous environment without external energy and to adapt to a predefined stress level by stress generation or relaxation. In this orientation-programming process, polymer material is deformed and oriented at an elevated temperature and subsequently cooled down while retaining its deformed shape, tension, and polymer chain entanglements. At body temperature and in an aqueous environment, the shape-memory is activated by the plasticizing effect of water molecules diffused into the polymer matrix causing an entropy-driven directed relaxation of oriented and preloaded polymer chains. This plasticizing effect is clearly seen as a decrease of the onset glass transition temperature by 10-13°C. We found that γ-irradiation used for sterilizing the orientation-programmed materials strongly affected the shape-recovery rate, but not the recovery ratio. Both non-γ-irradiated and γ-irradiated sample materials showed excellent shape-recovery ratios during a ten-week test period: 94 and 97%, respectively. The orientation-programmed materials generated a predefined load in a 37°C aqueous environment when their shape-recovery was restricted, but when external tension was applied to them, they adapted to the predefined level by stress relaxation. Our results show that functionality in terms of shape-memory can be generated in bioabsorbable polymers without tailoring the polymer chain structure thus shortening the time from development of technology to its utilization in medical devices.

  8. 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.

  9. 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)

  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. Optimisation of temperature-programmed gas chromatographic separation of organochloride pesticides by response surface methodology.

    PubMed

    D'Archivio, Angelo Antonio; Maggi, Maria Anna; Marinelli, Cristina; Ruggieri, Fabrizio; Stecca, Fabrizio

    2015-12-04

    A response surface methodology (RSM) approach is applied to optimise the temperature-programme gas-chromatographic separation of 16 organochloride pesticides, including 12 compounds identified as highly toxic chemicals by the Stockholm Convention on Persistent Organic Pollutants. A three-parameter relationship describing both linear and curve temperature programmes is derived adapting a model previously used in literature to describe concentration gradients in liquid chromatography with binary eluents. To investigate the influence of the three temperature profile descriptors (the starting temperature, the gradient duration and a shape parameter), a three-level full-factorial design of experiments is used to identify suitable combinations of the above variables spanning over a useful domain. Resolutions of adjacent peaks are the responses modelled by RSM using two alternative methods: a multi-layer artificial network (ANN) and usual polynomial regression. The proposed ANN-based approach permits to model simultaneously the resolutions of all the consecutive analyte pairs as a function of the temperature profile descriptors. Four critical pairs giving partially overlapped peaks are identified and multiresponse optimisation is carried out by analysing the surface plot of a global resolution defined as the average of the resolutions of the critical pairs. Descriptive/predictive performance and applicability of the ANN and polynomial RSM methods are compared and discussed.

  12. Lithium Ambient-Temperature Battery Reliability Program, May 1983-April 1985

    NASA Astrophysics Data System (ADS)

    Jaeger, C. D.; Hall, N. H.; Thomas, E. V.

    1986-06-01

    From May 1983 through April 1985 Sandia National Laboratories continued to develop and evaluate nondestructive methodology for predicting the reliability of primary lithium batteries. During this period, considerable time was spent improving the microcalorimetry data acquisition and processing software and completing the curve-fitting algorithm for the impedance data. All initial measurements were conducted, and all cells either completed the storage portion of the text matrix or remained in storage. Some statistical analyses were completed. Several nondestructive measurement variables that correlate well with remaining capacity were identified. Finally, the status of the program was evaluated and the program was tentatively extended to October 1986.

  13. 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).

  14. Irreversible adsorption/desorption of PAHs in sediment/water

    SciTech Connect

    Fu, G.; Kan, A.T.; Tomson, M.B.

    1996-10-01

    Successive adsorption isotherm of phenanthrene on soil corresponds to a constant partition of phenanthrene between the bulk solution and solid phase. This shows that the hydrophobic reaction is a dominant mechanism in adsorption process. However, desorption of PAHs appears irreversibility. Cyclic and multiple adsorption and desorption experiments indicated that there is an irreversibly adsorbed intrinsic capacity in the interaction of PAHs (naphthalene and phenanthrene) and soil in aqueous solution. This irreversible fraction for PAHs (naphthalene and phenanthrene) is about 1000-5000 {mu}g/g normalized on the basis of soil organic carbon. The desorption of PAHs from soil appears biphasic when the total adsorbed capacity is greater than the intrinsic irreversibly adsorbed value. In phase, the partitioning coefficient of desorption of PAHs is similar to that of adsorption. However, the other mechanism may be responsible to control the release of PAHs in phase 2.

  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. 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.

  18. 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}.

  19. The effects of surfactants on the desorption of organic contaminants from aquifer materials

    SciTech Connect

    Brickell, J.L.

    1989-01-01

    The efficiency of removing organic contaminants from groundwater aquifers by the pump and treat process is adversely affected by the retardation of the contaminant's mobility due to adsorption onto aquifer material. The use of surfactants in conjunction with the pump and treat process has the potential for improving contaminant mobility by solubilizing the adsorbed contaminant. An experimental program was conducted to screen various types of commercially available nonionic and anionic surfactants for solubilizing adsorbed naphthalene from one type of aquifer material. Two additional types of aquifer materials were obtained, and the surfactant mixture, Tween 20 and Aerosol AY-65, selected during the screening process was used at various concentrations for equilibrium desorption studies to quantify surfactant effects on naphthalene desorption. Column studies subsequently were conducted to determine surfactant effects in a flow through system. Equilibrium desorption studies showed that a 0.125% surfactant solution decreased the partition coefficient 65% compared with water alone for one soil type, while greater surfactant concentrations resulted in less effective mobilization. However, the same surfactant mixture markedly increased the partition coefficient when used with another soil type, and had negligible effects for the third soil type. It was shown that the clay mineralogy significantly influenced the effect of the surfactant solution. Column studies showed that mass removal efficiencies were increased by approximately 40 to 60% using the surfactant solution as compared with water alone. Varying flow rates did not influence the effectiveness of either the surfactant or water solutions.

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

    PubMed

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

    2014-08-15

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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  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. 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.

  8. 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.

  9. 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.

  10. An easy-to-use simulation program demonstrates variations in bacterial cell cycle parameters depending on medium and temperature.

    PubMed

    Stokke, Caroline; Flåtten, Ingvild; Skarstad, Kirsten

    2012-01-01

    Many studies are performed on chromosome replication and segregation in Escherichia coli and other bacteria capable of complex replication with C phases spanning several generations. For such investigations an understanding of the replication patterns, including copy numbers of origins and replication forks, is crucial for correct interpretation of the results.Flow cytometry is an important tool for generation of experimental DNA distributions of cell populations. Here, a Visual Basic based simulation program was written for the computation of theoretical DNA distributions for different choices of cell cycle parameters (C and D phase durations, doubling time etc). These cell cycle parameters can be iterated until the best fit between the experimental and theoretical DNA histograms is obtained. The Excel file containing the simulation software is attached as supporting information.Cultures of Escherichia coli were grown at twelve different media and temperature conditions, with following measurements by flow cytometry and simulation of the DNA distributions. A good fit was found for each growth condition by use of our simulation program. The resulting cell cycle parameters displayed clear inter-media differences in replication patterns, but indicated a high degree of temperature independence for each medium. The exception was the poorest medium (acetate), where the cells grew with overlapping replication cycles at 42 °C, but without at the lower temperatures.We have developed an easy-to-use tool for determination of bacteria's cell cycle parameters, and consequently the cells' chromosome configurations. The procedure only requires DNA distribution measurements by flow cytometry. Use of this simulation program for E. coli cultures shows that even cells growing quite slowly can have overlapping replication cycles. It is therefore always important not only to assume cells' replication patterns, but to actually determine the cell cycle parameters when changing growth

  11. 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.

  12. 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.

  13. 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.

  14. Absorption and desorption of hydrogen, deuterium, and tritium for Zr--V--Fe getter

    SciTech Connect

    Ichimura, K.; Inoue, N.; Watanabe, K.; Takeuchi, T.

    1984-07-01

    Nonevaporable getters have wide applicability for developing the tritium handling techniques for thermonuclear fusion devices. From this viewpoint, mechanisms of the absorption and desorption of hydrogen isotopes and the isotope effects were investigated for a Zr--V--Fe alloy (St-707) by means of the mass analyzed thermal desorption spectroscopy. It was observed that the absorption rate was proportional to the first power of the pressure, indicating that the rate limiting step is the dissociative adsorption of hydrogen isotopes on the surface. The activation energy was very small, in the order of magnitude of a few tens of calories per mole in a temperature range from -196 to 200 /sup 0/C. The desorption rate was proportional to the square of the amount of absorption, indicating that the rate limiting step is the associative desorption reaction of hydrogen atoms or ions diffused to the surface from the bulk. The rate constants for hydrogen and deuterium were determined as k/sub d/(H/sub 2/) = (5.3/sup +2.6//sub -1.7/)exp(-(28.0 +- 0.7) x 10/sup 3//RT) and k/sub d/(D/sub 2/) = (5.0/sup +2.7//sub -1.7/)exp(-(28.6 +- 0.8) x 10/sup 3//RT) in (1/Pa 1 s), respectively, where R is in (cal/mol deg). With regard to tritium, the rate constant was evaluated as k/sub d/(T/sub 2/) = (5.0/sup +20//sub -4.0/)exp(-(29.3 +- 3) x 10/sup 3//RT), however, the frequency factor will have to be corrected by knowing the relative sensitivity factor of the mass spectrometer for tritium (T/sub 2/).

  15. DOUBLE DCO{sup +} RINGS REVEAL CO ICE DESORPTION IN THE OUTER DISK AROUND IM LUP

    SciTech Connect

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

    2015-09-10

    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, C{sup 18}O 2–1, H{sup 13}CO{sup +} 3–2 and DCO{sup +} 3–2 emission at ∼0.″5 resolution. The images of these dust and gas tracers are clearly resolved. The DCO{sup +} 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{sup +} ring is associated with the balance of CO freeze-out and thermal desorption due to a radial decrease in disk temperature. The outer DCO{sup +} 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 H{sub 2}D{sup +} to form the observed DCO{sup +} outer ring. These observations demonstrate that spatially resolved DCO{sup +} 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.

  16. Mathematical method for the prediction of retention times of fatty acid methyl esters in temperature-programmed capillary gas chromatography.

    PubMed

    Torres, Alexandre G; Trugo, Nádia M F; Trugo, Luiz C

    2002-07-17

    An accurate method for identification of fatty acids in complex mixtures analyzed by temperature-programmed capillary gas chromatography is described. The method is based on a mathematical approach using regression curves obtained by plotting the relative retention times of fatty acid methyl esters (FAMEs) analyzed in isothermal and gradient temperature conditions. The method was applied to a complex biological sample (human milk), and it was possible to identify 64 fatty acids, including branched-chain and other fatty acids for which reference standards were not readily available. The identities of the majority of the peaks were confirmed by mass spectrometry. The relative residuals and the relative differences between estimated and measured relative retention times of individual FAMEs varied from 0.03 to 3.15% and from 0.0 to 2.9%, respectively. The method is useful for identification of fatty acids in routine analysis.

  17. 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.

  18. Effect of temperature on lubrication with biobased oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Coverage-dependent adsorption and desorption of oxygen on Pd(100).

    PubMed

    den Dunnen, Angela; Jacobse, Leon; Wiegman, Sandra; Berg, Otto T; Juurlink, Ludo B F

    2016-06-28

    We have studied the adsorption and desorption of O2 on Pd(100) by supersonic molecular beam techniques and thermal desorption spectroscopy. Adsorption measurements on the bare surface confirm that O2 initially dissociates for all kinetic energies between 56 and 380 meV and surface temperatures between 100 and 600 K via a direct mechanism. At and below 150 K, continued adsorption leads to a combined O/O2 overlayer. Dissociation of molecularly bound O2 during a subsequent temperature ramp leads to unexpected high atomic oxygen coverages, which are also obtained at high incident energy and high surface temperature. At intermediate temperatures and energies, these high final coverages are not obtained. Our results show that kinetic energy of the gas phase reactant and reaction energy dissipated during O2 dissociation on the cold surface both enable activated nucleation of high-coverage surface structures. We suggest that excitation of local substrate phonons may play a crucial role in oxygen dissociation at any coverage.

  20. Coverage-dependent adsorption and desorption of oxygen on Pd(100)

    NASA Astrophysics Data System (ADS)

    den Dunnen, Angela; Jacobse, Leon; Wiegman, Sandra; Berg, Otto T.; Juurlink, Ludo B. F.

    2016-06-01

    We have studied the adsorption and desorption of O2 on Pd(100) by supersonic molecular beam techniques and thermal desorption spectroscopy. Adsorption measurements on the bare surface confirm that O2 initially dissociates for all kinetic energies between 56 and 380 meV and surface temperatures between 100 and 600 K via a direct mechanism. At and below 150 K, continued adsorption leads to a combined O/O2 overlayer. Dissociation of molecularly bound O2 during a subsequent temperature ramp leads to unexpected high atomic oxygen coverages, which are also obtained at high incident energy and high surface temperature. At intermediate temperatures and energies, these high final coverages are not obtained. Our results show that kinetic energy of the gas phase reactant and reaction energy dissipated during O2 dissociation on the cold surface both enable activated nucleation of high-coverage surface structures. We suggest that excitation of local substrate phonons may play a crucial role in oxygen dissociation at any coverage.

  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. Low-Temperature Projects of the Department of Energy's Geothermal Technologies Program: Evaluation and Lessons Learned

    SciTech Connect

    Williams, Tom; Snyder, Neil; Gosnold, Will

    2016-10-23

    This paper discusses opportunities and challenges related to the technical and economic feasibility of developing power generation from geothermal resources at temperatures of 150 degrees C and lower. Insights from projects funded by the U.S. Department of Energy (DOE), Geothermal Technologies Office inform these discussions and provide the basis for some lessons learned to help guide decisions by DOE and the industry in further developing this resource. The technical basis for low-temperature geothermal energy is well established and the systems can be economic today in certain situations. However, these applications are far from a 'plug and play' product; successful development today requires a good knowledge of geothermal system design and operation.

  4. Experimental and theoretical comparison of gas desorption energies on metallic and semiconducting single-walled carbon nanotubes.

    PubMed

    Mandeltort, Lynn; Chen, De-Li; Saidi, Wissam A; Johnson, J Karl; Cole, Milton W; Yates, John T

    2013-05-22

    Single-walled carbon nanotubes (SWNTs) exhibit high surface areas and precisely defined pores, making them potentially useful materials for gas adsorption and purification. A thorough understanding of the interactions between adsorbates and SWNTs is therefore critical to predicting adsorption isotherms and selectivities. Metallic (M-) and semiconducting (S-) SWNTs have extremely different polarizabilities that might be expected to significantly affect the adsorption energies of molecules. We experimentally and theoretically show that this expectation is contradicted, for both a long chain molecule (n-heptane) and atoms (Ar, Kr, and Xe). Temperature-programmed desorption experiments are combined with van der Waals corrected density functional theory, examining adsorption on interior and exterior sites of the SWNTs. Our calculations show a clear dependence of the adsorption energy on nanotube diameter but not on whether the tubes are conducting or insulating. We find no significant experimental or theoretical difference in adsorption energies for molecules adsorbed on M- and S-SWNTs having the same diameter. Hence, we conclude that the differences in polarizabilities between M- and S-SWNTs have a negligible influence on gas adsorption for spherical molecules as well as for highly anisotropic molecules such as n-heptane. We expect this conclusion to apply to all types of adsorbed molecules where van der Waals interactions govern the molecular interaction with the SWNT.

  5. 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

  6. Adsorption and Desorption Behavior of NO on H-ZSM-5, Na-ZSM-5, and Na-A as Studied by EPR

    NASA Astrophysics Data System (ADS)

    Rudolf, Thomas; Böhlmann, Winfried; Pöppl, Andreas

    2002-03-01

    Nitric monoxide probe molecules are used to characterize the Lewis acid properties of sodium cations and aluminum defect centers in various zeolite materials. The adsorption-desorption behavior of NO probe molecules is studied at different temperatures for Na-A, Na-ZSM-5, H-ZSM-5, and silicalite. Adsorbed NO molecules form paramagnetic adsorption complexes with Lewis acid sites which can be examined by EPR transitions (ΔmS±1) at g≈2.0. Otherwise the desorption of NO into the gas phase can be monitored by the typical nine-line EPR spectrum (ΔmJ±1) of the 2Π3/2 state at g≈0.7776. This gas-phase signal is used to study the overall adsorption-desorption properties of the zeolites in the temperature range 150 K≲T≲300 K. At lower temperatures the probe molecules are adsorbed at the Lewis acid sites inside the nanoporous materials and produce an intensive spectrum at T≲110 K. But at intermediate temperatures 110 K≲T≲150 K the NO molecules are adsorbed only for a few hundred picoseconds because the lifetime of the adsorption complexes is limited by the beginning desorption processes. The decreasing lifetime of the adsorption complex with rising temperature results in an increasing homogeneous line broadening of their EPR signals. An analysis of the line-broadening effects provides an opportunity for determining the specific desorption energies EA(H-ZSM-5)=(20.2±7.3) kJ/mol, EA(Na-ZSM-5)=(4.1±1.5) kJ/mol, and EA(Na-A)=(7.1±2.1) kJ/mol for NO probe molecules at sodium cations and aluminum defect centers just below the desorption temperature.

  7. High temperature packing test program. First quarterly technical progress report, October 1-December 26, 1981

    SciTech Connect

    Not Available

    1982-02-12

    The program was undertaken to improve the technical understanding of the performance of plunger packings in coal liquefaction pilot plant feed pumps. During the first quarter of FY 1982, visits were made to the H-Coal, EDS and SRC-I pilot plants, where technical discussions were held with maintenance and engineering personnel, and the maintenance records and work orders for the plunger pumps were reviewed. Technical discussions were held with engineering personnel at the manufacturing facilities of three plunger pump manufacturers' companies. Contracts and technical discussions with packing vendors were initiated. Design of the laboratory tests was started.

  8. 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.

  9. 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.

  10. Atrazine sorption-desorption hysteresis by sugarcane mulch residue.

    PubMed

    Selim, H M; Zhu, H

    2005-01-01

    Sorption and desorption kinetics are essential components for modeling the movement and retention of applied agricultural chemicals in soils and the fraction of chemicals susceptible to runoff. In this study, we investigated the retention characteristics of sugarcane (Saccharum spp. hybrid) mulch residue for atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) based on studies of sorption-desorption kinetics. A sorption kinetic batch method was used to quantify retention of the mulch residue for a wide range of atrazine concentrations and reaction times. Desorption was performed following 504 h of sorption using successive dilutions, followed by methanol extraction. Atrazine retention by the mulch residue was well described using a linear model where the partitioning coefficient (K(d)) increased with reaction time from 10.40 to 23.4 cm3 g(-1) after 2 and 504 h, respectively. Values for mulch residue K(d) were an order of magnitude higher than those found for Commerce silt loam (fine-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts) where the sugarcane crop was grown. A kinetic multireaction model was successful in describing sorption behavior with reaction time. The model was equally successful in describing observed hysteretic atrazine behavior during desorption for all input concentrations. The model was concentration independent where one set of model parameters, which was derived from all batch results, was valid for the entire atrazine concentration range. Average atrazine recovery following six successive desorption steps were 63.67 +/- 4.38% of the amount adsorbed. Moreover, a hysteresis coefficient based on the difference in the area between sorption and desorption isotherms was capable of quantifying hysteresis of desorption isotherms.

  11. Retention time prediction in temperature-programmed, comprehensive two-dimensional gas chromatography: modeling and error assessment.

    PubMed

    Barcaru, Andrei; Anroedh-Sampat, Andjoe; Janssen, Hans-Gerd; Vivó-Truyols, Gabriel

    2014-11-14

    In this paper we present a model relating experimental factors (column lengths, diameters and thickness, modulation times, pressures and temperature programs) with retention times. Unfortunately, an analytical solution to calculate the retention in temperature programmed GC × GC is impossible, making thus necessary to perform a numerical integration. In this paper we present a computational physical model of GC × GC, capable of predicting with a high accuracy retention times in both dimensions. Once fitted (e.g., calibrated), the model is used to make predictions, which are always subject to error. In this way, the prediction can result rather in a probability distribution of (predicted) retention times than in a fixed (most likely) value. One of the most common problems that can occur when fitting unknown parameters using experimental data is overfitting. In order to detect overfitting situations and assess the error, the K-fold cross-validation technique was applied. Another technique of error assessment proposed in this article is the use of error propagation using Jacobians. This method is based on estimation of the accuracy of the model by the partial derivatives of the retention time prediction with respect to the fitted parameters (in this case entropy and enthalpy for each component) in a set of given conditions. By treating the predictions of the model in terms of intervals rather than as precise values, it is possible to considerably increase the robustness of any optimization algorithm.

  12. 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

  13. 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.

  14. Nitridation of Al2O3 surfaces: chemical and structural change triggered by oxygen desorption.

    PubMed

    Akiyama, Toru; Saito, Yasutaka; Nakamura, Kohji; Ito, Tomonori

    2013-01-11

    We present theoretical investigations that clarify elemental nitridation processes of corundum Al2O3(0001) and (1102) surfaces. The calculations within the density functional theory framework reveal that the structures with substitutional N atoms beneath the surface are stabilized under nitridation conditions. We also find that the desorption of O atoms at the topmost layer induces outward diffusion of O atoms as well as inward diffusion of N atoms, leading to the transformation into AlN films. The kinetic Monte Carlo simulations in conjunction with density functional theory results indeed observe a dependence of these chemical and structural changes on temperature and pressure.

  15. [Contrastive study of two methods("programmed temperature vaporization with back flushing" and "head space") for light hydrocarbon analysis].

    PubMed

    Xiao, T R; Cai, B; Meng, J H; Wang, P R

    2001-07-01

    Light hydrocarbon analytical method of "PTV with Back Flushing" presented here is characterized as follows: a) with "PTV" inlets temperature programmed; b) with gas line system of "Back Flushing"; c) with direct injection of oil samples. After oil sample injection, "Back Flushing" is on when light hydrocarbon components enter into analytical chromatographic column. At the same time, the temperature of inlet increases. The high temperature and "Back Flushing" blow the heavy components in the oil samples out of the analytical system. Besides, the analytical method of "Head Space" was established. Both "PTV with Back Flushing" and "Head Space" have the advantages of long column life and short analysis time. The resolution for lighter components < C9 meets the criterion of ASTM D5134-98, with the good repeatability. Ten oil samples from 6 oil areas were analysed by using the two methods. The relative deviations between the two analytical results represented by 19 geochemistry parameters were about +/- (1%-25%). The reasons for the deviation are discussed. It is pointed out that in geochemistry study it is not acceptable to combine the data obtained from two analytical methods. The analytical results obtained by injecting crude oil directly into injector are more reliable. The results obtained in "Head Space" analytical method should be calibrated when used in geochemistry study.

  16. 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.

  17. Using temperature-programmed reaction for kinetic analysis of reactions in dilute aqueous solutions at high pressure

    SciTech Connect

    Brown, L.F.; Robinson, B.A.

    1986-01-01

    The technique of temperature-programmed reaction (TPR) is shown to be a practical experimental method for determining reaction-rate expressions and kinetics parameters for reactions in dilute aqueous solutions under high ambient pressure. By sampling and measuring the extent of reaction during a rise in temperature, information normally obtained from a series of isothermal batch kinetics experiments can be found in a single TPR test. The use of nonlinear least-squares regression eliminates the need to achieve a constant rate of temperature rise, simplifies the experimental requirements for TPR results, and gives more accurate answers than does a linear analysis of TPR results. Numerical simulations of TPR tests in the presence of random concentration-measurement error is used to assess the accuracy of the technique and to identify the best values of crucial operating parameters. The results of two TPR experiments measuring the alkaline hydrolysis of ethyl acetate demonstrate the applicability of the technique to reactions in dilute aqueous solutions at high pressure. These preliminary experimental results, along with numerical simulations, allow us to chart a course for future TPR kinetics experiments on a large number of similar reactions. 16 refs., 6 figs., 8 tabs.

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

    SciTech Connect

    Shealy, S.E.; Lin, W.C.; Richards, M.K.; Culp, J.

    1997-12-31

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

  19. Optical laser-induced CO desorption from Ru(0001) monitored with a free-electron X-ray laser: DFT prediction and X-ray confirmation of a precursor state

    NASA Astrophysics Data System (ADS)

    Öberg, H.; Gladh, J.; Dell'Angela, M.; Anniyev, T.; Beye, M.; Coffee, R.; Föhlisch, A.; Katayama, T.; Kaya, S.; LaRue, J.; Møgelhøj, A.; Nordlund, D.; Ogasawara, H.; Schlotter, W. F.; Sellberg, J. A.; Sorgenfrei, F.; Turner, J. J.; Wolf, M.; Wurth, W.; Öström, H.; Nilsson, A.; Nørskov, J. K.; Pettersson, L. G. M.

    2015-10-01

    We present density functional theory modeling of time-resolved optical pump/X-ray spectroscopic probe data of CO desorption from Ru(0001). The BEEF van der Waals functional predicts a weakly bound state as a precursor to desorption. The optical pump leads to a near-instantaneous (< 100 fs) increase of the electronic temperature to nearly 7000 K. The temperature evolution and energy transfer between electrons, substrate phonons and adsorbate is described by the two-temperature model and found to equilibrate on a timescale of a few picoseconds to an elevated local temperature of ~ 2000 K. Estimating the free energy based on the computed potential of mean force along the desorption path, we find an entropic barrier to desorption (and by time-reversal also to adsorption). This entropic barrier separates the chemisorbed and precursor states, and becomes significant at the elevated temperature of the experiment (~ 1.4 eV at 2000 K). Experimental pump-probe X-ray absorption/X-ray emission spectroscopy indicates population of a precursor state to desorption upon laser-excitation of the system (Dell'Angela et al., 2013). Computing spectra along the desorption path confirms the picture of a weakly bound transient state arising from ultrafast heating of the metal substrate.

  20. 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.

  1. The influence of thermal desorption on genotoxicity of multipolluted soil.

    PubMed

    Bonnard, M; Devin, S; Leyval, C; Morel, J-L; Vasseur, P

    2010-07-01

    A multipolluted soil sampled from a former coking plant in Lorraine (France) was evaluated for its genotoxic effects on coelomocytes of the Eisenia fetida earthworm using the comet assay. The biological efficiency of thermal desorption of the contaminated soil was also investigated. The untreated polluted soil was shown to be genotoxic to earthworms. Although thermal desorption reduced the concentration of PAHs by 94% (Sigma(16 PAHs)=1846 and 101 mg/kg before and after thermal desorption, respectively), the treatment did not eliminate the genotoxicity of soil pollutants to earthworms but increased it. The concentration of non-volatile metals did not change after thermal desorption. Among metals found in the treated soil, cadmium, chromium and nickel could explain the genotoxicity of the contaminated soil after thermal desorption. The treatment could increase the bioavailability and genotoxicity of heavy metals, through a modification of the soil's organic matter, the speciation of heavy metals and their binding to organic matter. This study underlines the importance of measuring biological effects, in order to evaluate the risk associated with formerly contaminated soils and the efficiency of remediation.

  2. Photoemission, vibrational and stimulated desorption studies of metal-semiconductor interfaces and of chemisorbed atoms and molecules

    NASA Astrophysics Data System (ADS)

    Margaritondo, G.

    1984-10-01

    This program has produced in recent years a number of fundamental results on the microscopic properties of metal-semiconductor interfaces and on the mechanism of photon stimulated desorption. Both areas of research are of fundamental interest in condensed matter physics. Furthermore they have important applications in technology. The microscopic metal-semiconductor interface properties are directly related to the behavior and performance of the Schottky barrier, one of the building blocks of modern solid-state devices. This program investigates the formation of metal-semiconductor interfaces with some of the most powerful surface-science experimental probes: photoemission spectroscopy with synchrotron radiation, Auger spectroscopy, low-energy electron defraction in high-resolution electron energy loss surface vibrational spectroscopy. The stimulated desorption process is potentially a good probe of the chemical properties of absorbed species, e.g., in catalytic systems.

  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. Lateral hopping and desorption of a single CO molecule on a Cu(110) surface induced by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ueba, H.; Ootsuka, Y.

    2013-05-01

    Lateral hopping and desorption of a single CO molecule on a Cu(110) surface [Bartels , ScienceSCIEAS0036-807510.1126/science.1099770 305, 648 (2004)] induced by femtosecond laser pulses are studied using an indirect heat-transfer model. In addition to a direct heating of the reaction coordinate (RC) mode [frustrated translation (FT) mode for hopping and center-of-mass (CM) mode for desorption] by laser-generated hot electrons in the substrate, we consider an indirect heating of the RC mode through intermode coupling between the frustrated rotation (FR) mode and the RC mode. We calculate the transient behavior of the effective temperature of the FT and the CM modes, and of the normalized reaction yield. The experimental result of a ratio of the hopping yield along and across a row on a Cu(110) surface is nicely calculated. Although no information is available for the attempt frequency in a form of the Arrhenius equation for thermally activated reactions, it is predicted under which condition the desorption rate becomes in the same order of magnitude as the hopping rate, although the barrier height for desorption is much higher than for hopping. The present analysis highlights the role of excitation of the FR mode in reactions of a CO molecule as has been confirmed in the real-time observation [Backus , ScienceSCIEAS0036-807510.1126/science.1120693 310, 1790 (2005)].

  5. Leidenfrost Phenomenon-assisted Thermal Desorption (LPTD) and Its Application to Open Ion Sources at Atmospheric Pressure Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Saha, Subhrakanti; Chen, Lee Chuin; Mandal, Mridul Kanti; Hiraoka, Kenzo

    2013-03-01

    This work describes the development and application of a new thermal desorption technique that makes use of the Leidenfrost phenomenon in open ion sources at atmospheric pressure for direct mass spectrometric detection of ultratrace levels of illicit, therapeutic, and stimulant drugs, toxicants, and peptides (molecular weight above 1 kDa) in their unaltered state from complex real world samples without or with minor sample pretreatment. A low temperature dielectric barrier discharge ion source was used throughout the experiments and the analytical figures of merit of this technique were investigated. Further, this desorption technique coupled with other ionization sources such as electrospray ionization (ESI) and dc corona discharge atmospheric pressure chemical ionization (APCI) in open atmosphere was also investigated. The use of the high-resolution `Exactive Orbitrap' mass spectrometer provided unambiguous identification of trace levels of the targeted compounds from complex mixtures and background noise; the limits of detection for various small organic molecules and peptides treated with this technique were at the level of parts per trillion and 10-9 M, respectively. The high sensitivity of the present technique is attributed to the spontaneous enrichment of analyte molecules during the slow evaporation of the solvent, as well as to the sequential desorption of molecules from complex mixtures based on their volatilities. This newly developed desorption technique is simple and fast, while molecular ions are observed as the major ions.

  6. 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.

  7. 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.

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

    PubMed

    Liu, Yongchun; He, Hong; Ma, Qingxin

    2008-04-03

    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.

  9. Direct Scattering, Trapping, and Desorption in Atom-Surface Collisions

    NASA Astrophysics Data System (ADS)

    Fan, Guoqing; Manson, J. R.

    2008-08-01

    Maxwell is credited as the first to invoke the assumption that an impinging gas beam scatters from a surface with a direct contribution exhibiting little change in state and a trapping-desorption fraction that desorbs in equilibrium [J. C. Maxwell, Phil. Trans. R. Soc. LondonPTRSAV0370-2316 170, 231 (1879)10.1098/rstl.1879.0067]. Here a classical mechanical scattering theory is developed to describe direct scattering, trapping, and subsequent desorption of the incident beam. This theory allows a rigorous test of the Maxwell assumption and determines the conditions under which it is valid. The theory also gives quantitative explanations of important new experimental measurements [K. D. Gibson, N. Isa, and S. J. Sibener, J. Chem. Phys. 119, 13 083 (2003)JCPSA60021-960610.1063/1.1628672] for direct and trapping-desorption scattering of Ar atoms by a self-assembled layer of 1-decanethiol on Au(111).

  10. Direct scattering, trapping, and desorption in atom-surface collisions.

    PubMed

    Fan, Guoqing; Manson, J R

    2008-08-08

    Maxwell is credited as the first to invoke the assumption that an impinging gas beam scatters from a surface with a direct contribution exhibiting little change in state and a trapping-desorption fraction that desorbs in equilibrium [J. C. Maxwell, Phil. Trans. R. Soc. London 170, 231 (1879)]. Here a classical mechanical scattering theory is developed to describe direct scattering, trapping, and subsequent desorption of the incident beam. This theory allows a rigorous test of the Maxwell assumption and determines the conditions under which it is valid. The theory also gives quantitative explanations of important new experimental measurements [K. D. Gibson, N. Isa, and S. J. Sibener, J. Chem. Phys. 119, 13 083 (2003)] for direct and trapping-desorption scattering of Ar atoms by a self-assembled layer of 1-decanethiol on Au(111).

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

    PubMed Central

    2015-01-01

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

  12. The study of 'microsurfaces' using thermal desorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Thomas, M. E.; Poppa, H.; Pound, G. M.

    1979-01-01

    The use of a newly combined ultrahigh vacuum technique for studying continuous and particulate evaporated thin films using thermal desorption spectroscopy (TDS), transmission electron microscopy (TEM), and transmission electron diffraction (TED) is discussed. It is shown that (1) CO thermal desorption energies of epitaxially deposited (111) Ni and (111) Pd surfaces agree perfectly with previously published data on bulk (111) single crystal, (2) contamination and surface structural differences can be detected using TDS as a surface probe and TEM as a complementary technique, and (3) CO desorption signals from deposited metal coverages of one-thousandth of a monolayer should be detectable. These results indicate that the chemisorption properties of supported 'microsurfaces' of metals can now be investigated with very high sensitivity. The combined use of TDS and TEM-TED experimental methods is a very powerful technique for fundamental studies in basic thin film physics and in catalysis.

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

    PubMed

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

    2015-06-02

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

  14. 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

  15. FORTRAN programs for generating fluid inclusion isochores and fugacity coefficients for the system H 2O-CO 2-NaCl at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Bowers, Teresa Suter; Helgeson, Harold C.

    Program DENFIND permits calculation of pressures and temperatures corresponding to isochores for H 2O-CO 2-NaCl fluids which can be used to generate pressure corrections of fluid inclusion homogenization temperatures. Program FUGCO facilitates calculation of fugacity coefficients in the system H 2O-CO 2-NaCl as a function of pressure, temperature and fluid composition. Both programs employ a modified Redlich-Kwong equation of state for the ternary system (Bowers and Helgeson, 1983a), which is applicable to fluids containing up to 35 wt. % NaCl (relative to H 2O + NaCl) at pressures above 500 bars and temperature from 350 to 600°C.

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

    SciTech Connect

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

    2008-01-01

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

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. Soot Structure and Reactivity Analysis by Raman Microspectroscopy, Temperature-Programmed Oxidation, and High-Resolution Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Knauer, Markus; Schuster, Manfred E.; Su, Dangsheng; Schlögl, Robert; Niessner, Reinhard; Ivleva, Natalia P.

    2009-11-01

    Raman microspectroscopy (RM), temperature-programmed oxidation (TPO), high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS) were combined to get comprehensive information on the relationship between structure and reactivity of soot in samples of spark discharge (GfG), heavy duty engine diesel (EURO VI and IV) soot, and graphite powder upon oxidation by oxygen at increasing temperatures. GfG soot and graphite powder represent the higher and lower reactivity limits. Raman microspectroscopic analysis was conducted by determination of spectral parameters using a five band fitting procedure (G, D1-D4) as well as by evaluation of the dispersive character of the D mode. The analysis of spectral parameters shows a higher degree of disorder and a higher amount of molecular carbon for untreated GfG soot samples than for samples of untreated EURO VI and EURO IV soot. The structural analysis based on the dispersive character of the D mode revealed substantial differences in ordering descending from graphite powder, EURO IV, VI to GfG soot. HRTEM images and EELS analysis of EURO IV and VI samples indicated a different morphology and a higher structural order as compared to GfG soot in full agreement with the Raman analysis. These findings are also confirmed by the reactivity of soot during oxidation (TPO), where GfG soot was found to be the most reactive and EURO IV and VI soot samples exhibited a moderate reactivity.

  3. Temperature programmed oxidation of coked H-gallosilicate (MFI) propane aromatization catalyst: Influence of catalyst composition and pretreatment parameters

    SciTech Connect

    Choudhary, V.R.; Devadas, P.; Sansare, S.D.; Guisnet, M.

    1997-03-01

    Temperature programmed oxidation (TPO) of H-gallosilicate (MFI) coked in the propane aromatization at 550{degrees}C for a time-on-stream of 7-8 h has been investigated by measuring point to point the consumption of oxygen and also the formation of the both CO and CO{sub 2} (by GC analysis using a 16-loop gas sampling valve) during the TPO run from 50{degrees} to 900{degrees}C at a linear heating rate of 20{degrees}C min{sup -1} in a flow (50 cm{sup 3} min{sup -1}) of a O{sub 2}-He mixture (8.0 mol% O{sub 2}). The SiGa and Na/Ga ratios, calcination temperature, and hydrothermal pretreatments of the zeolite and also the presence of binder (silica or kaolin) in the catalyst have a strong influence on the TPO of coked zeolite. The influence is attributed to changes in the zeolite properties (viz., zeolitic acidity or framework Ga and non-GW Ga-oxide species), which affect the coke oxidation both directly and/or indirectly, by controlling the nature of coke formed during the coking process. 23 refs., 4 figs., 2 tabs.

  4. Temperature programmed CVD: a novel technique to investigate carbon nanotube synthesis on FeMo/MgO catalysts.

    PubMed

    Teixeira, Ana Paula C; Lemos, Bruno R S; Magalhães, Leandro A; Ardisson, José D; Lago, Rochel M; Furtado, Clascídia A; Santos, Adelina P

    2012-03-01

    In this work, it is demonstrated how a novel technique based on temperature-programmed chemical vapor deposition (TPCVD) can be used to investigate the synthesis of carbon nanotubes (CNTs) from methane on a classic catalyst FeMo(x)/MgO (x = 0.07, 0.35 and 1.00). TPCVD monitors carbon deposition by measuring H2 formed during CH4 decomposition and affords information on the different catalytic species, deactivation process, reaction kinetics and carbon yields. The obtained results showed for FeMgO catalyst a simple TPCVD peak related to the production of carbon beginning at 760 degrees C with maximum at 800 degrees C followed by a rapid deactivation resulting in a low carbon yield. The addition of Mo to Fe/MgO catalyst completely changes the TPCVD profile with the formation of a new catalytic species active at temperatures higher than 900 degrees C, which is stable and continuously decomposes CH4 to produce high carbon yields. Raman, TG/DTG, Mössbauer, SEM, TEM, XRD and TPR analyses suggested that this active catalytic phase is likely related to Fe-Mo and Fe-Mo-C phases active to produce single wall and mainly multiwall carbon nanotubes.

  5. Sorption-desorption of carbamazepine by palygorskite-montmorillonite (PM) filter medium.

    PubMed

    Berhane, Tedros M; Levy, Jonathan; Krekeler, Mark P S; Danielson, Neil D; Stalcup, Apryll

    2015-01-23

    Palygorskite-montmorillonite (PM) was studied as a potential sewage treatment effluent filter material for carbamazepine. Batch sorption experiments were conducted as a function of granule size (0.3-0.6, 1.7-2.0 and 2.8mm) and different sewage effluent conditions (pH, ionic strength and temperature). Results showed PM had a mix of fibrous and plate-like morphologies. Sorption and desorption isotherms were fitted to the Freundlich model. Sorption is granule size-dependent and the medium granule size would be an appropriate size for optimizing both flow and carbamazepine retention. Highest and lowest sorption capacities corresponded to the smallest and the largest granule sizes, respectively. The lowest and the highest equilibrium aqueous (Ce) and sorbed (qe) carbamazepine concentrations were 0.4 mg L(-1) and 4.5 mg L(-1), and 0.6 mg kg(-1) and 411.8 mg kg(-1), respectively. Observed higher relative sorption at elevated concentrations with a Freundlich exponent greater than one, indicated cooperative sorption. The sorption-desorption hysteresis (isotherm non-singularity) indicated irreversible sorption. Higher sorption observed at higher rather than at lower ionic strength conditions is likely due to a salting-out effect. Negative free energy and the inverse sorption capacity-temperature relationship indicated the carbamazepine sorption process was favorable or spontaneous. Solution pH had little effect on sorption.

  6. Experimental clarification of the desorption of H 2, D 2 and He mixtures from cryosorption pumps

    NASA Astrophysics Data System (ADS)

    Terashita, Masashi; Fukada, Satoshi

    2011-10-01

    The behavior of dynamic desorption of He, H 2 and D 2 from a cryosorption pump is experimentally investigated for simplified rough separation of D-T fuel exhaust from impurities. As a fundamental study to separate the unburned D-T fuel and impurities dynamically, the discharge rates of H 2 and D 2 (as a representative of T 2), He (as a major impurity) are determined as a function of time and temperature, when the cryosorption pump is regenerated from 10 K to the room temperature of 285-305 K. The release behavior of H 2 and D 2 is compared, and the desorption isotherms of H 2, D 2 and He for activated carbon used in the cryosorption pump are determined from their respective discharge curves. The present result may lead to provide a simplified technique to decrease the throughput of the following fuel purification system and to decrease the tritium inventory by rapid separation of the D-T fuel from impurities.

  7. Helium implanted Eurofer97 characterized by positron beam Doppler broadening and Thermal Desorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Carvalho, I.; Schut, H.; Fedorov, A.; Luzginova, N.; Desgardin, P.; Sietsma, J.

    2013-11-01

    Reduced Activation Ferritic/Martensitic steels are being extensively studied because of their foreseen application in fusion and Generation IV fission reactors. To produce irradiation induced defects, Eurofer97 samples were implanted with helium at energies of 500 keV and 2 MeV and doses of 1 × 1015-1016 He/cm2, creating atomic displacements in the range 0.07-0.08 dpa. The implantation induced defects were characterized by positron beam Doppler Broadening (DB) and Thermal Desorption Spectroscopy (TDS). Results show that up to ˜600 K peaks that can be attributed to He desorption from overpressured HenVm (n > m) clusters and vacancy assisted mechanism in the case of helium in the substitutional position. The temperature range 600-1200 K is related to the formation of larger clusters HenVm (n < m). The dissociation of the HeV and the phase transition attributed to a sharp peak in the TDS spectra at 1200 K. Above this temperature, the release of helium from bubbles is observed.

  8. 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.

  9. 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.

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

    DOE PAGES

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

    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. 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

  12. 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

  13. 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

    2016-12-01

    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.

  14. 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.

  15. 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...

  16. 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...

  17. Adsorption and desorption of doxorubicin on oxidized carbon nanotubes.

    PubMed

    Wang, Yunxia; Yang, Sheng-Tao; Wang, Yanli; Liu, Yuanfang; Wang, Haifang

    2012-09-01

    Carbon nanotubes (CNTs) show promise as nano-drug carriers. To develop the CNT-based drug delivery systems, drug loading and release are two major issues. In this study, we systematically evaluated the adsorption and desorption of doxorubicin (DOX) on oxidized multi-walled CNTs (O-MWCNTs). Our results indicated that O-MWCNTs possessed a huge adsorption capacity for DOX (9.45×10(3) mg/g). Although the adsorption process was quite slow, the adsorption capacity kept high enough for the therapy while shortening the incubation time to 2h (1.03×10(3) mg/g). The desorption of DOX from O-MWCNTs scarcely occurred while incubated in buffer solution at both pH 7.4 and pH 5.5, however, the lower pH did benefit the desorption. The presence of serum proteins facilitated the desorption of DOX significantly, because these proteins bound strongly to O-MWCNTs resulting in the partial surface of O-MWNCTs being occupied. Moreover, the adsorption time also affected the release of DOX from O-MWCNTs. Shortening the incubation time benefited the release of DOX. The implications to the drug loading and therapeutics of the CNT-based drug delivery systems are discussed.

  18. 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...

  19. 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 ...

  20. 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...

  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. 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.

  4. Thermal desorption behavior of helium in aged titanium tritide films

    NASA Astrophysics Data System (ADS)

    Cheng, G. J.; Shi, L. Q.; Zhou, X. S.; Liang, J. H.; Wang, W. D.; Long, X. G.; Yang, B. F.; Peng, S. M.

    2015-11-01

    The desorption behavior of helium in TiT(1.5∼1.8)-x3Hex film samples (x = 0.0022-0.22) was investigated by thermal desorption technique in vacuum condition in this paper. The thermal helium desorption spectrometry (THDS) of aging titanium tritide films prepared by electron beam evaporation revealed that, depending on the decayed 3He concentration in the samples, there are more than four states of helium existing in the films. The divided four zones in THDS based on helium states represent respectively: (1) the mobile single helium atoms with low activation energy in all aging samples resulted from the interstitial sites or dissociated from interstitial clusters, loops and dislocations, (2) helium bubbles inside the grain lattices, (3) helium bubbles in the grain boundaries and interconnected networks of dislocations in the helium concentration of 3Hegen/Ti > 0.0094, and (4) helium bubbles near or linked to the film surface by interconnected channel for later aging stage with 3Hegen/Ti > 0.18. The proportion of helium desorption in each zone was estimated, and dissociated energies of helium for different trapping states were given.

  5. Dust as interstellar catalyst. I. Quantifying the chemical desorption process

    NASA Astrophysics Data System (ADS)

    Minissale, M.; Dulieu, F.; Cazaux, S.; Hocuk, S.

    2016-01-01

    Context. The presence of dust in the interstellar medium has profound consequences on the chemical composition of regions where stars are forming. Recent observations show that many species formed onto dust are populating the gas phase, especially in cold environments where UV- and cosmic-ray-induced photons do not account for such processes. Aims: The aim of this paper is to understand and quantify the process that releases solid species into the gas phase, the so-called chemical desorption process, so that an explicit formula can be derived that can be included in astrochemical models. Methods: We present a collection of experimental results of more than ten reactive systems. For each reaction, different substrates such as oxidized graphite and compact amorphous water ice were used. We derived a formula for reproducing the efficiencies of the chemical desorption process that considers the equipartition of the energy of newly formed products, followed by classical bounce on the surface. In part II of this study we extend these results to astrophysical conditions. Results: The equipartition of energy correctly describes the chemical desorption process on bare surfaces. On icy surfaces, the chemical desorption process is much less efficient, and a better description of the interaction with the surface is still needed. Conclusions: We show that the mechanism that directly transforms solid species into gas phase species is efficient for many reactions.

  6. Desorption and biodegradation behavior of naphthalene sorbed to soil colloids

    SciTech Connect

    Bandyopadhyay, A.; Robinson, K.G.

    1995-12-31

    Groundwater and soil have been widely contaminated by a variety of man-made chemicals. In recent years, special attention has been given not only to minimize or prevent environmental pollution, but to restore contaminated environments. Organic pollutants, especially Polycyclic Aromatic Hydrocarbons (PAH) pose special problems for soil-groundwater remediation. Many PAHs are hydrophobic in nature; once sorbed to the soil and sediment, they are extremely difficult to remove and act as a source of low level, long term contamination. Their fate and transport are tremendously influenced by their sorptive behavior with soils and sediments. As compared to sorption behavior, desorption of PAHs and other similar organic compounds has been less thoroughly investigated. Desorption data are often extrapolated from adsorption data, assuming the sorption process as reversible. Both sorption and desorption rates are reported to follow a two phase pattern: an initial fast rate, followed by a slow rate. This paper details research performed to determine the influence of soil colloids on the desorption and bioavailability of naphthalene (target PAH). The goal of this research was to determine if sorption or mineralization controls naphthalene biodegradation.

  7. INITIAL SCREENING OF THERMAL DESORPTION FOR SOIL REMEDIATION

    EPA Science Inventory

    The purpose of the paper is to present procedures for collecting and evaluating key data that affect the potential application of thermal desorption for a specific site. These data are defined as 'criticalsuccess factors'. The screening prodcedure can be used to peerform an ini...

  8. 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...

  9. Desorption of plutonium from montmorillonite: An experimental and modeling study

    NASA Astrophysics Data System (ADS)

    Begg, James D.; Zavarin, Mavrik; Kersting, Annie B.

    2017-01-01

    Desorption of plutonium (Pu) will likely control the extent to which it is transported by mineral colloids. We evaluated the adsorption/desorption behavior of Pu on SWy-1 montmorillonite colloids at pH 4, pH 6, and pH 8 using batch adsorption and flow cell desorption experiments. After 21 days adsorption, Pu(IV) affinity for montmorillonite displayed a pH dependency, with Kd values highest at pH 4 and lowest at pH 8. The pH 8 experiment was further allowed to equilibrate for 6 months and showed an increase in Kd, indicating that true sorption equilibrium was not achieved within the first 21 days. For the desorption experiments, aliquots of the sorption suspensions were placed in a flow cell, and Pu-free solutions were then pumped through the cell for a period of 12 days. Changes in influent solution flow rate were used to investigate the kinetics of Pu desorption and demonstrated that it was rate-limited over the experimental timescales. At the end of the 12-day flow cell experiments, the extent of desorption was again pH dependent, with pH 8 > pH 6 > pH 4. Further, at pH 8, less Pu was desorbed after an adsorption contact time of 6 months than after a contact time of 21 days, consistent with an aging of Pu on the clay surface. A conceptual model for Pu adsorption/desorption that incorporated known surface-mediated Pu redox reactions was used to fit the experimental data. The resulting rate constants indicated processes occurring on timescales of months and even years which may, in part, explain observations of clay colloid-facilitated Pu transport on decadal timescales. Importantly, however, our results also imply that migration of Pu adsorbed to montmorillonite colloids at long (50-100 year) timescales under oxic conditions may not be possible without considering additional phenomena, such as co-precipitation.

  10. Desorption of plutonium from montmorillonite: An experimental and modeling study

    DOE PAGES

    Begg, James D.; Zavarin, Mavrik; Kersting, Annie B.

    2017-01-15

    Desorption of plutonium (Pu) will likely control the extent to which it is transported by mineral colloids. In this article, we evaluated the adsorption/desorption behavior of Pu on SWy-1 montmorillonite colloids at pH 4, pH 6, and pH 8 using batch adsorption and flow cell desorption experiments. After 21 days adsorption, Pu(IV) affinity for montmorillonite displayed a pH dependency, with Kd values highest at pH 4 and lowest at pH 8. The pH 8 experiment was further allowed to equilibrate for 6 months and showed an increase in Kd, indicating that true sorption equilibrium was not achieved within the firstmore » 21 days. For the desorption experiments, aliquots of the sorption suspensions were placed in a flow cell, and Pu-free solutions were then pumped through the cell for a period of 12 days. Changes in influent solution flow rate were used to investigate the kinetics of Pu desorption and demonstrated that it was rate-limited over the experimental timescales. At the end of the 12-day flow cell experiments, the extent of desorption was again pH dependent, with pH 8 > pH 6 > pH 4. Further, at pH 8, less Pu was desorbed after an adsorption contact time of 6 months than after a contact time of 21 days, consistent with an aging of Pu on the clay surface. In addition, a conceptual model for Pu adsorption/desorption that incorporated known surface-mediated Pu redox reactions was used to fit the experimental data. The resulting rate constants indicated processes occurring on timescales of months and even years which may, in part, explain observations of clay colloid-facilitated Pu transport on decadal timescales. Importantly, however, our results also imply that migration of Pu adsorbed to montmorillonite colloids at long (50–100 year) timescales under oxic conditions may not be possible without considering additional phenomena, such as co-precipitation.« less

  11. 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...

  12. Concentration-dependent kinetics of pollutant desorption from soils.

    PubMed

    Braida, Washington J; White, Jason C; Zhao, Dongye; Ferrandino, Francis J; Pignatello, Joseph J

    2002-12-01

    Sorption-desorption kinetics play a major role in transport and bioavailability of pollutants in soils. Contaminant concentration is a potentially important factor controlling kinetics. A previous paper dealt with the effect of solute concentration on fractional uptake rates of phenanthrene and pyrene from a finite aqueous source. In this study we determined the effect of initial phenanthrene sorbed concentration (q(0)) on the fractional mass desorption rates from each of six soils to a zero-concentration solution, approximated by including a polymer adsorbent (Tenax) as a third-phase sink. The soils were preequilibrated with phenanthrene for 180 d. Consistent with theory, the fractional desorption rates determined by empirical curve fitting increased with q(0) provided the isotherm was nonlinear. After 500 to 600 d of desorption at the steepest possible concentration gradient, all soils retained a highly resistant fraction, which ranged from 4 to 31% of q(0), except for one soil at a high q(0). The highly resistant fraction decreased with increasing q(0), for nonlinear isotherm cases, but increased with q(0) for linear or nearly linear isotherm cases. Application of a nonlinear diffusion model, the dual-mode diffusion model (DMDM), to the nonresistant fraction gave reasonably good fits. The DMDM attributes the increase with concentration of the apparent diffusivity to a decrease in the proportion of sorbate occupying immobile sites (holes) in soil organic matter. The concentration-dependent term in the expression for the apparent diffusivity correlated with either of two indices that reflect the linearity of the sorption isotherm. Bunker C oil present in one soil acted as a partition domain. The findings of this study are consistent with heterogeneous models of soil organic matter, and indicate that concentration effects should be taken into account whenever desorption rate is important.

  13. 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.

  14. Mechanisms of H2O desorption from amorphous solid water by 157-nm irradiation: an experimental and theoretical study.

    PubMed

    DeSimone, Alice J; Crowell, Vernon D; Sherrill, C David; Orlando, Thomas M

    2013-10-28

    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) cm(2) 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.

  15. 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.

  16. Effects of SWNT and metallic catalyst on hydrogen absorption/desorption performance of MgH2.

    PubMed

    Wu, Chengzhang; Wang, Ping; Yao, Xiangdong; Liu, Chang; Chen, Demin; Lu, Gao Qing; Cheng, Huiming

    2005-12-01

    The microstructure and absorption/desorption characteristics of composite MgH2 and 5 wt % as-prepared single-walled carbon nanotubes (MgH2-5ap) obtained by the mechanical grinding method were investigated. Experimental results show that the MgH2-5ap sample exhibits faster absorption kinetics and relatively lower desorption temperature than pure MgH2 or MgH2-purified single-walled carbon nanotube composite. Storage capacities of 6.0 and 4.2 wt % hydrogen for the MgH2-5ap composite were achieved in 60 min at 423 and 373 K, respectively. Furthermore, its desorption temperature was reduced by 70 K due to the introduction of as-prepared single-walled carbon nanotubes (SWNTs). In addition, the different effects of SWNTs and metallic catalysts contained in the as-prepared SWNTs were also investigated and a hydrogenation mechanism was proposed. It is suggested that metallic particles may be mainly responsible for the improvement of the hydrogen absorption kinetics, and SWNTs for the enhancement of hydrogen absorption capacity of MgH2.

  17. Development of a screening method for the analysis of organic pollutants in water using dual stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry.

    PubMed

    Tölgyessy, Peter; Vrana, Branislav; Krascsenits, Zoltán

    2011-12-15

    The development of a method for screening of organic compounds with a wide range of physico-chemical properties in water, based on dual stir bar sorptive extraction coupled with thermal desorption and gas chromatography-mass spectrometry (dual SBSE-TD-GC-MS) is described. The investigated water sample is divided into two aliquots and extracted with stir bar sorptive extraction at two different conditions: using addition of methanol or sodium chloride, respectively. Following extraction, the two stir bars are inserted into the same glass thermal desorption liner and are simultaneously desorbed and analysed by GC-MS. The method optimisation was performed using 45 environmentally harmful substances with different volatilities (boiling point from 193 to 495°C), polarity (logK(ow) from 2.17 to 8.54) and acido-basic properties. The majority of model compounds was selected from the EU list of priority substances in the field of water policy and from the US EPA method 625, respectively. Optimisation was performed for extraction parameters (sample volume, extraction time, stirring rate, addition of modifiers) as well as for the thermal desorption conditions (desorption flow, desorption time, cryofocusing temperature). Performance characteristics (recovery, repeatability, carryover, linearity, limits of detection and quantification) were determined for the optimised method. An example of analysis of a contaminated groundwater sample is presented.

  18. Strontium Adsorption and Desorption Reactions in Model Drinking Water Distribution Systems

    DTIC Science & Technology

    2014-02-04

    RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (Include area code) 11-04-2014 Journal Article Strontium adsorption and desorption reactions in model... strontium (Sr2+) adsorption to and desorption from iron corrosion products were examined in two model drinking water distribution systems (DWDS...used to control Sr2; desorption. calcium carbonate; drinking water distribution system; α-FeOOH; iron; strontium ; XANES Unclassified

  19. 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

  20. Detection of trace ink compounds in erased handwritings using electrospray-assisted laser desorption ionization mass spectrometry.

    PubMed

    Kao, Yi-Ying; Cheng, Sy-Chyi; Cheng, Chu-Nian; Shiea, Jentaie; Ho, Hsiu-O

    2014-06-01

    Writings made with erasable pens on paper surfaces can either be rubbed off with an eraser or rendered invisible by changing the temperature of the ink. However, trace ink compounds still remain in the paper fibers even after rubbing or rendering. The detection of these ink compounds from erased handwritings will be helpful in knowing the written history of the paper. In this study, electrospray-assisted laser desorption ionization/mass spectrometry was used to characterize trace ink compounds remaining in visible and invisible ink lines. The ink compounds were desorbed from the paper surface by irradiating the handwritings with a pulsed laser beam; the desorbed analytes were subsequently ionized in an electrospray plume and detected by a quadrupole time-of-flight mass spectrometry mass analyzer. Because of the high spatial resolution of the laser beam, electrospray-assisted laser desorption ionization/mass spectrometry analysis resulted in minimal damage to the sample documents.

  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. Structure, provenance and residence time of terrestrial organic carbon: insights from Programmed temperature Pyrolysis-Combustion of river sediments

    NASA Astrophysics Data System (ADS)

    Feng, X.; Galy, V.; Rosenheim, B. E.; Roe, K. M.; Williams, E. K.

    2010-12-01

    The terrestrial organic carbon (OC) represents one of the largest reservoirs of C on earth and thus plays a crucial role in the global C cycle, participating to the regulation of atmospheric chemistry. While degradation of sedimentary OC (petrogenic C) is a source of CO2 for the atmosphere, burial of biospheric C (e.g. plant debris and soil OC) is a long-term sequestration of atmospheric CO2. Over short timescales, the atmospheric CO2 level is also sensitive to variations of the residence time of carbon in continental reservoirs. Fluvial transport plays a crucial role in the organic carbon cycle, constituting the connection between the different reservoirs and promoting the transfer of C from one reservoir to the other. Moreover, thanks to the integrating effect of erosion, studying river sediments allows the spatial and temporal integration of organic carbon exchanges occurring in a given basin. OC transported by rivers (riverine OC) is known to be extremely heterogeneous in nature and reactivity, however; ranging from extremely refractory petrogenic C (e.g. graphite) to soil complex OC to labile vegetation debris. Here we use a recently developed method, a programmed-temperature pyrolysis-combustion system (PTP-CS) coupled to multiisotopic analysis, to determine the reactivity, age and nature of OC in river sediments. The method takes advantage of the wide range of reactivity and radiocarbon content of different components of riverine OC. We submitted to PTP-CS a set of river sediments from 1) the Ganges-Brahmputra river system and, 2) the lower Mississippi river. Preliminary results highlight the heterogeneous nature of riverine OC. Different components of the riverine OC pool decompose at different temperature and are characterized by extremely variable isotopic compositions. The decomposition of radiocarbon dead petrogenic C at very high temperature allows estimating the respective contribution of biospheric and petrogenic C. Moreover, biospheric OC appears to

  3. Evaluation of cleaning and disinfection performance of automatic washer disinfectors machines in programs presenting different cycle times and temperatures.

    PubMed

    Bergo, Maria do Carmo Noronha Cominato

    2006-01-01

    Thermal washer-disinfectors represent a technology that brought about great advantages such as, establishment of protocols, standard operating procedures, reduction in occupational risk of a biological and environmental nature. The efficacy of the cleaning and disinfection obtained by automatic washer disinfectors machines in running programs with different times and temperatures determined by the different official agencies was validated according to recommendations from ISO Standards 15883-1/1999 and HTM2030 (NHS Estates, 1997) for the determining of the Minimum Lethality and DAL both theoretically and through the use with thermocouples. In order to determine the cleaning efficacy, the Soil Test, Biotrace Pro-tect and the Protein Test Kit were used. The procedure to verify the CFU count of viable microorganisms was performed before and after the thermal disinfection. This article shows that the results are in compliance with the ISO and HTM Standards. The validation steps confirmed the high efficacy level of the Medical Washer-Disinfectors. This protocol enabled the evaluation of the procedure based on evidence supported by scientific research, aiming at the support of the Supply Center multi-professional personnel with information and the possibility of developing further research.

  4. 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.

  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. 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.

  9. Photon-Induced Thermal Desorption of CO from Small Metal-Carbonyl Clusters

    NASA Astrophysics Data System (ADS)

    Lüttgens, G.; Pontius, N.; Bechthold, P. S.; Neeb, M.; Eberhardt, W.

    2002-02-01

    Thermal CO desorption from photoexcited free metal-carbonyl clusters has been resolved in real time using two-color pump-probe photoelectron spectroscopy. Sequential energy dissipation steps between the initial photoexcitation and the final desorption event, e.g., electron relaxation and thermalization, have been resolved for Au2(CO)- and Pt2(CO)-5. The desorption rates for the two clusters differ considerably due to the different numbers of vibrational degrees of freedom. The unimolecular CO-desorption thresholds of Au2(CO)- and Pt2(CO)-5 have been approximated by means of a statistical Rice-Ramsperger-Kassel calculation using the experimentally derived desorption rate constants.

  10. Photon- and electron-stimulated desorption from laboratory models of interstellar ice grains

    SciTech Connect

    Thrower, J. D.; Abdulgalil, A. G. M.; Collings, M. P.; McCoustra, M. R. S.; Burke, D. J.; Brown, W. A.; Dawes, A.; Holtom, P. J.; Kendall, P.; Mason, N. J.; Jamme, F.; Fraser, H. J.; Rutten, F. J. M.

    2010-07-15

    The nonthermal desorption of water from ice films induced by photon and low energy electron irradiation has been studied under conditions mimicking those found in dense interstellar clouds. Water desorption following photon irradiation at 250 nm relies on the presence of an absorbing species within the H{sub 2}O ice, in this case benzene. Desorption cross sections are obtained and used to derive first order rate coefficients for the desorption processes. Kinetic modeling has been used to compare the efficiencies of these desorption mechanisms with others known to be in operation in dense clouds.

  11. Molecular diffusion between walls with adsorption and desorption

    NASA Astrophysics Data System (ADS)

    Levesque, Maximilien; Bénichou, Olivier; Rotenberg, Benjamin

    2013-01-01

    The time dependency of the diffusion coefficient of particles in porous media is an efficient probe of their geometry. The analysis of this quantity, measured, e.g., by nuclear magnetic resonance, can provide rich information pertaining to porosity, pore size distribution, permeability, and surface-to-volume ratio of porous materials. Nevertheless, in numerous if not all practical situations, transport is confined by walls where adsorption and desorption processes may occur. In this article, we derive explicitly the expression of the time-dependent diffusion coefficient between two confining walls in the presence of adsorption and desorption. We show that they strongly modify the time-dependency of the diffusion coefficient, even in this simple geometry. We finally propose several applications, from sorption rates measurements to the use as a reference for numerical implementations for more complex geometries.

  12. 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.

  13. Improved Imaging Resolution in Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Kertesz, Vilmos; Van Berkel, Gary J

    2008-01-01

    Imaging resolution of desorption electrospray ionization mass spectrometry (DESI-MS) was investigated using printed patterns on paper and thin-layer chromatography (TLC) plate surfaces. Resolution approaching 40 m was achieved with a typical DESI-MS setup, which is approximately 5 times better than the best resolution reported previously. This improvement was accomplished with careful control of operational parameters (particularly spray tip-to-surface distance, solvent flow rate, and spacing of lane scans). Also, an appropriately strong analyte/surface interaction and uniform surface texture on the size scale no larger that the desired imaging resolution were required to achieve this resolution. Overall, conditions providing the smallest possible effective desorption/ionization area in the DESI impact plume region and minimizing the analyte redistribution on the surface during analysis led to the improved DESI-MS imaging resolution.

  14. From Laser Desorption to Laser Ablation of Biopolymers

    NASA Astrophysics Data System (ADS)

    Franz, Hillenkamp

    1998-03-01

    For selected indications laser ablation and cutting of biological tissues is clinical practice. Preferentially lasers with emission wavelengths in the far UV and the mid IR are used, for which tissue absorption is very high. Morphologically the ablation sites look surprisingly similar for the two wavelength ranges, despite of the very different prim y putative interaction mechanisms. Ablation depth as a function of fluence follows a sigmoidal curve. Even factors below the nominal ablation threshold superficial layers of material get removed from the surface. This is the fluence range for Matrix-Assisted Laser Desorption/Ionization (MALDI). Evidence will be presented which suggest that strong similarities exist between the desorption and ablation processes both for UV- as well as for IR-wavelengths.

  15. 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.

  16. Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Laskin, Julia; Heath, Brandi S.; Roach, Patrick J.; Cazares, Lisa H.; Semmes, O. John

    2012-01-03

    We present the first results showing the ambient imaging of biological samples in their native environment using nanospray desorption ionization (nanoDESI) mass spectrometry. NanoDESI is an ambient pressure ionization technique that enables precise control of ionization of molecules from substrates. We demonstrate highly sensitive and robust analysis of tissue samples with high spatial resolution (<12 {mu}m) without sample preparation, which will be essential for applications in clinical diagnostics, drug discovery, molecular biology, and biochemistry.

  17. [Sorption-desorption of phosphate in wastewater by hydrous iron oxide].

    PubMed

    Xiang, Xue-Min; Liu, Ying; Zhou, Ji-Ti; Wang, Ren

    2008-11-01

    FeCl3 was used t o prepare hydrous iron oxide (HIO) as a n absorbent for phosphate (P) sorption and desorption study. The results showed that as pH decreased, the sorption capacity of HIO increased, and the sorption kinetics followed the second-order model, and the sorption isotherm could be fitted by the Langmuir equation. A 50 g/L NaOH solution was used for desorption of P from HIO, and the desorption rate could be reached over 98% . No relation was found between desorption rate and adsorption capacity. Based on above results, HIO was applied to adsorption of P from supernatant of sludge thickener, and after desorption, more than 90% of P was recovered. According to the results obtained, an effective system for P removal and recovery from municipal wastewater was suggested, which includes the following processes: adsorption, desorption, regeneration of HIO, and of recovery of P from P-rich desorption solution.

  18. Residence time dependent desorption of Staphylococcus epidermidis from hydrophobic and hydrophilic substrata.

    PubMed

    Boks, Niels P; Kaper, Hans J; Norde, Willem; Busscher, Henk J; van der Mei, Henny C

    2008-12-01

    Adhesion and desorption are simultaneous events during bacterial adhesion to surfaces, although desorption is far less studied than adhesion. Here, desorption of Staphylococcus epidermidis from substratum surfaces is demonstrated to be residence time dependent. Initial desorption rate coefficients were similar for hydrophilic and hydrophobic dimethyldichlorosilane (DDS)-coated glass, likely because initial desorption is controlled by attractive Lifshitz-Van der Waals interactions, which are comparable on both substratum surfaces. However, significantly slower decay times of the desorption rate coefficients are found for hydrophilic glass than for hydrophobic DDS-coated glass. This difference is suggested to be due to the acid-base interactions between staphylococci and these surfaces, which are repulsive on hydrophilic glass and attractive on hydrophobic DDS-coated glass. Final desorption rate coefficients are higher on hydrophilic glass than on hydrophobic DDS-coated glass, due to the so called hydrophobic effect, facilitating a closer contact on hydrophobic DDS-coated glass.

  19. Desorption of cesium from granite under various aqueous conditions.

    PubMed

    Wang, Tsing-Hai; Li, Ming-Hsu; Wei, Yuan-Yaw; Teng, Shi-Ping

    2010-12-01

    In this work the desorption of cesium ions from crushed granite in synthetic groundwater (GW) and seawater (SW) was investigated. Results were compared with those obtained in deionized water (DW) and in two kinds of extraction solutions, namely: MgCl(2) and NaOAc (sodium acetate). In general, the desorption rate of Cs from crushed granite increased proportionally with initial Cs loadings. Also, amounts of desorbed Cs ions followed the tendency in the order SW>GW>NaOAc approximately equal MgCl(2)>DW solutions. This indicated that the utilization of extraction reagents for ion exchange will underestimate the Cs desorption behavior. Fitting these experimental data by Langmuir model showed that these extraction reagents have reduced Cs uptake by more than 90%, while only less than 1% of adsorbed Cs ions are still observed in GW and SW solutions in comparison to those in DW. Further SEM/EDS mapping studies clearly demonstrate that these remaining adsorbed Cs ions are at the fracture areas of biotite.

  20. Adsorption-desorption kinetics of soft particles onto surfaces

    NASA Astrophysics Data System (ADS)

    Osberg, Brendan; Gerland, Ulrich

    A broad range of physical, chemical, and biological systems feature processes in which particles randomly adsorb on a substrate. Theoretical models usually assume ``hard'' (mutually impenetrable) particles, but in soft matter physics the adsorbing particles can be effectively compressible, implying ``soft'' interaction potentials. We recently studied the kinetics of such soft particles adsorbing onto one-dimensional substrates, identifying three novel phenomena: (i) a gradual density increase, or ''cramming'', replaces the usual jamming behavior of hard particles, (ii) a density overshoot, can occur (only for soft particles) on a time scale set by the desorption rate, and (iii) relaxation rates of soft particles increase with particle size (on a lattice), while hard particles show the opposite trend. The latter occurs since unjamming requires desorption and many-bodied reorganization to equilibrate -a process that is generally very slow. Here we extend this analysis to a two-dimensional substrate, focusing on the question of whether the adsorption-desorption kinetics of particles in two dimensions is similarly enriched by the introduction of soft interactions. Application to experiments, for example the adsorption of fibrinogen on two-dimensional surfaces, will be discussed.

  1. Unexpected Analyte Oxidation during Desorption Electrospray Ionization - Mass Spectrometry

    SciTech Connect

    Pasilis, Sofie P; Kertesz, Vilmos; Van Berkel, Gary J

    2008-01-01

    During the analysis of surface spotted analytes using desorption electrospray ionization mass spectrometry (DESI-MS), abundant ions are sometimes observed that appear to be the result of oxygen addition reactions. In this investigation, the effect of sample aging, the ambient lab environment, spray voltage, analyte surface concentration, and surface type on this oxidative modification of spotted analytes, exemplified by tamoxifen and reserpine, during analysis by desorption electrospray ionization mass spectrometry was studied. Simple exposure of the samples to air and to ambient lighting increased the extent of oxidation. Increased spray voltage lead also to increased analyte oxidation, possibly as a result of oxidative species formed electrochemically at the emitter electrode or in the gas - phase by discharge processes. These oxidative species are carried by the spray and impinge on and react with the sampled analyte during desorption/ionization. The relative abundance of oxidized species was more significant for analysis of deposited analyte having a relatively low surface concentration. Increasing spray solvent flow rate and addition of hydroquinone as a redox buffer to the spray solvent were found to decrease, but not entirely eliminate, analyte oxidation during analysis. The major parameters that both minimize and maximize analyte oxidation were identified and DESI-MS operational recommendations to avoid these unwanted reactions are suggested.

  2. Laser desorption lamp ionization source for ion trap mass spectrometry.

    PubMed

    Wu, Qinghao; Zare, Richard N

    2015-01-01

    A two-step laser desorption lamp ionization source coupled to an ion trap mass spectrometer (LDLI-ITMS) has been constructed and characterized. The pulsed infrared (IR) output of an Nd:YAG laser (1064 nm) is directed to a target inside a chamber evacuated to ~15 Pa causing desorption of molecules from the target's surface. The desorbed molecules are ionized by a vacuum ultraviolet (VUV) lamp (filled with xenon, major wavelength at 148 nm). The resulting ions are stored and detected in a three-dimensional quadrupole ion trap modified from a Finnigan Mat LCQ mass spectrometer operated at a pressure of ≥ 0.004 Pa. The limit of detection for desorbed coronene molecules is 1.5 pmol, which is about two orders of magnitude more sensitive than laser desorption laser ionization mass spectrometry using a fluorine excimer laser (157 nm) as the ionization source. The mass spectrum of four standard aromatic compounds (pyrene, coronene, rubrene and 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (OPC)) shows that parent ions dominate. By increasing the infrared laser power, this instrument is capable of detecting inorganic compounds.

  3. Laboratory constraints on ice formation, restructuring and desorption

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.

    2016-10-01

    Ices form on the surfaces of interstellar and circumstellar dust grains though freeze-out of molecules and atoms from the gas-phase followed by chemical reactions. The composition, chemistry, structure and desorption properties of these ices regulate two important aspects of planet formation: the locations of major condensation fronts in protoplanetary disks (i.e. snow lines) and the formation efficiencies of complex organic molecules in astrophysical environments. The latter regulates the availability of prebiotic material on nascent planets. With ALMA it is possible to directly observe both (CO) snowlines and complex organics in protoplanetary disks. The interpretation of these observations requires a detailed understanding of the fundamental ice processes that regulate the build-up, evolution and desorption of icy grain mantles. This proceeding reviews how experiments on thermal CO and N2 ice desorption, UV photodesorption of CO ice, and CO diffusion in H2O ice have been used to guide and interpret astrochemical observations of snowlines and complex molecules.

  4. Adsorption and Desorption of Nitrogen and Water Vapor by clay

    NASA Astrophysics Data System (ADS)

    Cui, Deshan; Chen, Qiong; Xiang, Wei; Huang, Wei

    2015-04-01

    Adsorption and desorption of nitrogen and water vapor by clay has a significant impact on unsaturated soil physical and mechanical properties. In order to study the adsorption and desorption characteristics of nitrogen and water vapor by montmorillonite, kaolin and sliding zone soils, the Autosorb-iQ specific surface area and pore size analyzer instrument of United State was taken to carry out the analysis test. The adsorption and desorption of nitrogen at 77K and water vapor at 293K on clay sample were conducted. The theories of BET, FHH and hydration energy were taken to calculate the specific surface, surface fractal dimension and adsorption energy. The results show that the calculated specific surface of water vapor by clay is bigger than nitrogen adsorption test because clay can adsorb more water vapor molecule than nitrogen. Smaller and polar water vapor molecule can access the micropore and then adsorb on the mineral surface and mineral intralayer, which make the mineral surface cations hydrate and the mineral surface smoother. Bigger and nonpolar nitrogen molecule can not enter into the micropore as water vapor molecule and has weak interaction with clay surface.

  5. Infrared laser-assisted desorption electrospray ionization mass spectrometry.

    PubMed

    Rezenom, Yohannes H; Dong, Jianan; Murray, Kermit K

    2008-02-01

    We have used an infrared laser for desorption of material and ionization by interaction with electrosprayed solvent. Infrared laser-assisted desorption electrospray ionization (IR LADESI) mass spectrometry was used for the direct analysis of water-containing samples under ambient conditions. An ion trap mass spectrometer was modified to include a pulsed Er:YAG laser at 2.94 microm wavelength coupled into a germanium oxide optical fiber for desorption at atmospheric pressure and a nanoelectrospray source for ionization. Analytes in aqueous solution were placed on a stainless steel target and irradiated with the pulsed IR laser. Material desorbed and ablated from the target was ionized by a continuous stream of charged droplets from the electrosprayed solvent. Peptide and protein samples analyzed using this method yield mass spectra similar to those obtained by conventional electrospray. Blood and urine were analyzed without sample pretreatment to demonstrate the capability of IR LADESI for direct analysis of biological fluids. Pharmaceutical products were also directly analyzed. Finally, the role of water as a matrix in the IR LADESI process is discussed.

  6. LASER DESORPTION IONIZATION MASS SPECTROMETRY ON SILICON NANOWELL ARRAYS

    PubMed Central

    Gulbakan, Basri; Park, Dooho; Kang, Myungchan; Kececi, Kaan; Martin, Charles R.; Powell, David H.; Tan, Weihong

    2010-01-01

    This paper describes a new technique for fabrication of nanostructured porous silicon (pSi) for laser desorption ionization mass spectrometry. Porous silicon nanowell arrays were prepared by argon plasma etching through an alumina mask. Porous silicon prepared in this way proved to be an excellent substrate for desorption/ionization on silicon (DIOS) mass spectrometry (MS) using adenosine, Pro-Leu-Gly tripeptide and [Des-Arg9]-bradykinin as the model compounds. It also allows the analyses of complex biological samples such as a tryptic digest of bovine serum albumin, and a carnitine standard mixture. Nanowell array surfaces were also used for direct quantification of the illicit drug fentanyl in red blood cell extracts. This method also allows full control of the surface features. MS results suggested that the pore depth has significant effect on the ion signals. Significant improvement in the ionization was observed by increasing the pore depth from 10 nm to 50 nm. These substrates are useful for laser desorption ionization in both the atmospheric pressure and vacuum regimes. PMID:20731384

  7. Effect of equilibration time on Pu desorption from goethite

    SciTech Connect

    Wong, Jennifer C.; Zavarin, Mavrik; Begg, James D.; Kersting, Annie B.; Powell, Brian A.

    2015-01-28

    Strongly sorbing ions such as plutonium may become irreversibly bound to mineral surfaces over time implicates near- and far-field transport of Pu. Batch adsorption–desorption data were collected as a function of time and pH to study the surface stability of Pu on goethite. Pu(IV) was adsorbed to goethite over the pH range 4.2 to 6.6 for different periods of time (1, 6, 15, 34 and 116 d). Moreover, following adsorption, Pu was leached from the mineral surface with desferrioxamine B (DFOB), a complexant capable of effectively competing with the goethite surface for Pu. The amount of Pu desorbed from the goethite was found to vary as a function of the adsorption equilibration time, with less Pu removed from the goethite following longer adsorption periods. This effect was most pronounced at low pH. Logarithmic desorption distribution ratios for each adsorption equilibration time were fit to a pH-dependent model. Model slopes decreased between 1 and 116 d adsorption time, indicating that overall Pu(IV) surface stability on goethite surfaces becomes less dependent on pH with greater adsorption equilibration time. The combination of adsorption and desorption kinetic data suggest that non-redox aging processes affect Pu sorption behavior on goethite.

  8. Effect of equilibration time on Pu desorption from goethite

    DOE PAGES

    Wong, Jennifer C.; Zavarin, Mavrik; Begg, James D.; ...

    2015-01-28

    Strongly sorbing ions such as plutonium may become irreversibly bound to mineral surfaces over time implicates near- and far-field transport of Pu. Batch adsorption–desorption data were collected as a function of time and pH to study the surface stability of Pu on goethite. Pu(IV) was adsorbed to goethite over the pH range 4.2 to 6.6 for different periods of time (1, 6, 15, 34 and 116 d). Moreover, following adsorption, Pu was leached from the mineral surface with desferrioxamine B (DFOB), a complexant capable of effectively competing with the goethite surface for Pu. The amount of Pu desorbed from the goethitemore » was found to vary as a function of the adsorption equilibration time, with less Pu removed from the goethite following longer adsorption periods. This effect was most pronounced at low pH. Logarithmic desorption distribution ratios for each adsorption equilibration time were fit to a pH-dependent model. Model slopes decreased between 1 and 116 d adsorption time, indicating that overall Pu(IV) surface stability on goethite surfaces becomes less dependent on pH with greater adsorption equilibration time. The combination of adsorption and desorption kinetic data suggest that non-redox aging processes affect Pu sorption behavior on goethite.« less

  9. The desorptivity model of bulk soil-water evaporation

    NASA Technical Reports Server (NTRS)

    Clapp, R. B.

    1983-01-01

    Available models of bulk evaporation from a bare-surfaced soil are difficult to apply to field conditions where evaporation is complicated by two main factors: rate-limiting climatic conditions and redistribution of soil moisture following infiltration. Both factors are included in the "desorptivity model', wherein the evaporation rate during the second stage (the soil-limiting stage) of evaporation is related to the desorptivity parameter, A. Analytical approximations for A are presented. The approximations are independent of the surface soil moisture. However, calculations using the approximations indicate that both soil texture and soil moisture content at depth significantly affect A. Because the moisture content at depth decreases in time during redistribution, it follows that the A parameter also changes with time. Consequently, a method to calculate a representative value of A was developed. When applied to field data, the desorptivity model estimated cumulative evaporation well. The model is easy to calculate, but its usefulness is limited because it requires an independent estimate of the time of transition between the first and second stages of evaporation. The model shows that bulk evaporation after the transition to the second stage is largely independent of climatic conditions.

  10. Laser desorption ionization mass spectrometry on silicon nanowell arrays.

    PubMed

    Gulbakan, Basri; Park, Dooho; Kang, Myungchan; Kececi, Kaan; Martin, Charles R; Powell, David H; Tan, Weihong

    2010-09-15

    This paper describes a new technique for fabrication of nanostructured porous silicon (pSi) for laser desorption ionization mass spectrometry. Porous silicon nanowell arrays were prepared by argon plasma etching through an alumina mask. Porous silicon prepared in this way proved to be an excellent substrate for desorption/ionization on silicon (DIOS) mass spectrometry (MS) using adenosine, Pro-Leu-Gly tripeptide, and [Des-Arg(9)]-bradykinin as the model compounds. It also allows the analyses of complex biological samples such as a tryptic digest of bovine serum albumin and a carnitine standard mixture. Nanowell array surfaces were also used for direct quantification of the illicit drug fentanyl in red blood cell extracts. This method also allows full control of the surface features. MS results suggested that the pore depth has a significant effect on the ion signals. Significant improvement in the ionization was observed by increasing the pore depth from 10 to 50 nm. These substrates are useful for laser desorption ionization in both the atmospheric pressure and vacuum regimes.

  11. Boron desorption and fractionation in Subduction Zone Fore Arcs: Implications for the sources and transport of deep fluids

    NASA Astrophysics Data System (ADS)

    Saffer, Demian M.; Kopf, Achim J.

    2016-12-01

    At many subduction zones, pore water geochemical anomalies at seafloor seeps and in shallow boreholes indicate fluid flow and chemical transport from depths of several kilometers. Identifying the source regions for these fluids is essential toward quantifying flow pathways and volatile fluxes through fore arcs, and in understanding their connection to the loci of excess pore pressure at depth. Here we develop a model to track the coupled effects of boron desorption, smectite dehydration, and progressive consolidation within sediment at the top of the subducting slab, where such deep fluid signals likely originate. Our analysis demonstrates that the relative timing of heating and consolidation is a dominant control on pore water composition. For cold slabs, pore water freshening is maximized because dehydration releases bound water into low porosity sediment, whereas boron concentrations and isotopic signatures are modest because desorption is strongly sensitive to temperature and is only partially complete. For warmer slabs, freshening is smaller, because dehydration occurs earlier and into larger porosities, but the boron signatures are larger. The former scenario is typical of nonaccretionary margins where insulating sediment on the subducting plate is commonly thin. This result provides a quantitative explanation for the global observation that signatures of deeply sourced fluids are generally strongest at nonaccretionary margins. Application of our multitracer approach to the Costa Rica, N. Japan, N. Barbados, and Mediterranean Ridge subduction zones illustrates that desorption and dehydration are viable explanations for observed geochemical signals, and suggest updip fluid migration from these source regions over tens of km.

  12. Direct analysis of anabolic steroids in urine using Leidenfrost phenomenon assisted thermal desorption-dielectric barrier discharge ionization mass spectrometry.

    PubMed

    Saha, Subhrakanti; Mandal, Mridul Kanti; Nonami, Hiroshi; Hiraoka, Kenzo

    2014-08-11

    Rapid detection of trace level anabolic steroids in urine is highly desirable to monitor the consumption of performance enhancing anabolic steroids by athletes. The present article describes a novel strategy for identifying the trace anabolic steroids in urine using Leidenfrost phenomenon assisted thermal desorption (LPTD) coupled to dielectric barrier discharge (DBD) ionization mass spectrometry. Using this method the steroid molecules are enriched within a liquid droplet during the thermal desorption process and desorbed all-together at the last moment of droplet evaporation in a short time domain. The desorbed molecules were ionized using a dielectric barrier discharge ion-source in front of the mass spectrometer inlet at open atmosphere. This process facilitates the sensitivity enhancement with several orders of magnitude compared to the thermal desorption at a lower temperature. The limits of detection (LODs) of various steroid molecules were found to be in the range of 0.05-0.1 ng mL(-1) for standard solutions and around two orders of magnitude higher for synthetic urine samples. The detection limits of urinary anabolic steroids could be lowered by using a simple and rapid dichloromethane extraction technique. The analytical figures of merit of this technique were evaluated at open atmosphere using suitable internal standards. The technique is simple and rapid for high sensitivity and high throughput screening of anabolic steroids in urine.

  13. A mass spectrometric system for analyzing thermal desorption spectra of ion-implanted argon and cesium in tungsten. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Wood, G. M., Jr.

    1974-01-01

    A mass spectrometric system for determining the characteristics of materials used in instrumental development and aerospace applications was developed. The desorption spectra of cesium that was ion-implanted into polycrystalline tungsten and the effects on the spectra of bombardment of the tungsten by low energy (70 eV) electrons were investigated. Work function changes were measured by the retarding potential diode method. Flash desorption characteristics were observed and gas-reaction mechanisms of the surface of heated metal filaments were studied. Desorption spectra were measured by linearly increasing the sample temperature at a selected rate, the temperature cycling being generated from a ramp-driven dc power supply, with the mass spectrometer tuned to a mass number of interest. Results of the study indicate an anomolous desorption mechanism following an electron bombardment of the sample surface. The enhanced spectra are a function of the post-bombardment time and energy and are suggestive of an increased concentration of cesium atoms, up to 10 or more angstroms below the surface.

  14. Adsorption, desorption, and film formation of quinacridone and its thermal cracking product indigo on clean and carbon-covered silicon dioxide surfaces

    NASA Astrophysics Data System (ADS)

    Scherwitzl, Boris; Lassnig, Roman; Truger, Magdalena; Resel, Roland; Leising, Günther; Winkler, Adolf

    2016-09-01

    The evaporation of quinacridone from a stainless steel Knudsen cell leads to the partial decomposition of this molecule in the cell, due to its comparably high sublimation temperature. At least one additional type of molecules, namely indigo, could be detected in the effusion flux. Thermal desorption spectroscopy and atomic force microscopy have been used to study the co-deposition of these molecules on sputter-cleaned and carbon-covered silicon dioxide surfaces. Desorption of indigo appears at temperatures of about 400 K, while quinacridone desorbs at around 510 K. For quinacridone, a desorption energy of 2.1 eV and a frequency factor for desorption of 1 × 1019 s-1 were calculated, which in this magnitude is typical for large organic molecules. A fraction of the adsorbed quinacridone molecules (˜5%) decomposes during heating, nearly independent of the adsorbed amount, resulting in a surface composed of small carbon islands. The sticking coefficients of indigo and quinacridone were found to be close to unity on a carbon covered SiO2 surface but significantly smaller on a sputter-cleaned substrate. The reason for the latter can be attributed to insufficient energy dissipation for unfavorably oriented impinging molecules. However, due to adsorption via a hot-precursor state, the sticking probability is increased on the surface covered with carbon islands, which act as accommodation centers.

  15. Adsorption, desorption, and film formation of quinacridone and its thermal cracking product indigo on clean and carbon-covered silicon dioxide surfaces.

    PubMed

    Scherwitzl, Boris; Lassnig, Roman; Truger, Magdalena; Resel, Roland; Leising, Günther; Winkler, Adolf

    2016-09-07

    The evaporation of quinacridone from a stainless steel Knudsen cell leads to the partial decomposition of this molecule in the cell, due to its comparably high sublimation temperature. At least one additional type of molecules, namely indigo, could be detected in the effusion flux. Thermal desorption spectroscopy and atomic force microscopy have been used to study the co-deposition of these molecules on sputter-cleaned and carbon-covered silicon dioxide surfaces. Desorption of indigo appears at temperatures of about 400 K, while quinacridone desorbs at around 510 K. For quinacridone, a desorption energy of 2.1 eV and a frequency factor for desorption of 1 × 10(19) s(-1) were calculated, which in this magnitude is typical for large organic molecules. A fraction of the adsorbed quinacridone molecules (∼5%) decomposes during heating, nearly independent of the adsorbed amount, resulting in a surface composed of small carbon islands. The sticking coefficients of indigo and quinacridone were found to be close to unity on a carbon covered SiO2 surface but significantly smaller on a sputter-cleaned substrate. The reason for the latter can be attributed to insufficient energy dissipation for unfavorably oriented impinging molecules. However, due to adsorption via a hot-precursor state, the sticking probability is increased on the surface covered with carbon islands, which act as accommodation centers.

  16. Desorption of polycyclic aromatic hydrocarbons from field-contaminated soil to a two-dimensional hydrophobic surface before and after bioremediation.

    PubMed

    Hu, Jing; Aitken, Michael D

    2012-10-01

    Dermal exposure can represent a significant health risk in settings involving potential contact with soil contaminated with polycyclic aromatic hydrocarbons (PAHs). However, there is limited work on the ability of PAHs in contaminated soil to reach the skin surface via desorption from the soil. We evaluated PAH desorption from a field-contaminated soil to a two-dimensional hydrophobic surface (C18 extraction disk) as a measure of potential dermal exposure as a function of soil loading (5-100 mg dry soil cm(-2)), temperature (20-40°C), and soil moisture content (2-40%) over periods up to 16d. The efficacy of bioremediation in removing the most readily desorbable PAH fractions was also evaluated. Desorption kinetics were described well by an empirical two-compartment kinetic model. PAH mass desorbed to the C18 disk kept increasing at soil loadings well above the estimated monolayer coverage, suggesting mechanisms for PAH transport to the surface other than by direct contact. Such mechanisms were reinforced by observations that desorption occurred even with dry or moist glass microfiber filters placed between the C18 disk and the soil. Desorption of all PAHs was substantially reduced at a soil moisture content corresponding to field capacity, suggesting that transport through pore air contributed to PAH transport to the C18 disk. The lower molecular weight PAHs had greater potential to desorb from soil than higher molecular weight PAHs. Biological treatment of the soil in a slurry-phase bioreactor completely eliminated PAH desorption to the C18 disks.

  17. Desorption of polycyclic aromatic hydrocarbons from field-contaminated soil to a two-dimensional hydrophobic surface before and after bioremediation

    PubMed Central

    Hu, Jing; Aitken, Michael D.

    2012-01-01

    Dermal exposure can represent a significant health risk in settings involving potential contact with soil contaminated with polycyclic aromatic hydrocarbons (PAHs). However, there is limited work on the ability of PAHs in contaminated soil to reach the skin surface via desorption from the soil. We evaluated PAH desorption from a field-contaminated soil to a two-dimensional hydrophobic surface (C18 extraction disk) as a measure of potential dermal exposure as a function of soil loading (5 to 100 mg dry soil/cm2), temperature (20 °C to 40 °C), and soil moisture content (2% to 40%) over periods up to 16 d. The efficacy of bioremediation in removing the most readily desorbable PAH fractions was also evaluated. Desorption kinetics were described well by an empirical two-compartment kinetic model. PAH mass desorbed to the C18 disk kept increasing at soil loadings well above the estimated monolayer coverage, suggesting mechanisms for PAH transport to the surface other than by direct contact. Such mechanisms were reinforced by observations that desorption occurred even with dry or moist glass microfiber filters placed between the C18 disk and the soil. Desorption of all PAHs was substantially reduced at a soil moisture content corresponding to field capacity, suggesting that transport through pore air contributed to PAH transport to the C18 disk. The lower molecular weight PAHs had greater potential to desorb from soil than higher molecular weight PAHs. Biological treatment of the soil in a slurry-phase bioreactor completely eliminated PAH desorption to the C18 disks. PMID:22704210

  18. Evaluation of B. subtilis SPB1 biosurfactants' potency for diesel-contaminated soil washing: optimization of oil desorption using Taguchi design.

    PubMed

    Mnif, Inès; Sahnoun, Rihab; Ellouze-Chaabouni, Semia; Ghribi, Dhouha

    2014-01-01

    Low solubility of certain hydrophobic soil contaminants limits remediation process. Surface-active compounds can improve the solubility and removal of hydrophobic compounds from contaminated soils and, consequently, their biodegradation. Hence, this paper aims to study desorption efficiency of oil from soil of SPB1 lipopeptide biosurfactant. The effect of different physicochemical parameters on desorption potency was assessed. Taguchi experimental design method was applied in order to enhance the desorption capacity and establish the best washing parameters. Mobilization potency was compared to those of chemical surfactants under the newly defined conditions. Better desorption capacity was obtained using 0.1% biosurfacatnt solution and the mobilization potency shows great tolerance to acidic and alkaline pH values and salinity. Results show an optimum value of oil removal from diesel-contaminated soil of about 87%. The optimum washing conditions for surfactant solution volume, biosurfactant concentration, agitation speed, temperature, and time were found to be 12 ml/g of soil, 0.1% biosurfactant, 200 rpm, 30 °C, and 24 h, respectively. The obtained results were compared to those of SDS and Tween 80 at the optimal conditions described above, and the study reveals an effectiveness of SPB1 biosurfactant comparable to the reported chemical emulsifiers. (1) The obtained findings suggest (a) the competence of Bacillus subtilis biosurfactant in promoting diesel desorption from soil towards chemical surfactants and (b) the applicability of this method in decontaminating crude oil-contaminated soil and, therefore, improving bioavailability of hydrophobic compounds. (2) The obtained findings also suggest the adequacy of Taguchi design in promoting process efficiency. Our findings suggest that preoptimized desorption process using microbial-derived emulsifier can contribute significantly to enhancement of hydrophobic pollutants' bioavailability. This study can be

  19. Effects of He, D interaction on thermal desorption of He and D2 and microstructural evolution in pure Fe

    NASA Astrophysics Data System (ADS)

    Xu, Q.; Zhang, J.

    2016-10-01

    He and H atoms are produced in (n, α) and (n, p) nuclear reactions. In fusion reactors, energetic T and D, being isotopes of H, and He particles damage the surface materials. To investigate the He-D interaction, Fe, which is a model metal of choice in ferritic stainless steel that is used in fusion reactors, was irradiated separately by He or D2 ions and by combinations of He + D2 or D2 + He ions with the energy of 5 keV. The dose for single-species irradiation and each step of double-species irradiation was 1.0 × 1020 ions/m2. Thermal desorption analysis indicates that, in the case of single ion species irradiation, thermal desorption of D occurs at temperatures below 700 K, while the main thermal desorption of He occurs at 750 K and above 1200 K. The binding energy of He and defects is higher than that of D and defects. In the case of irradiation with combinations of ions species, however, the obtained thermal desorption spectra are the same, although the peak intensities are different, suggesting that the He-D interaction is weak. The sorption of D is more predominant for irradiations with He + D2. On the microstructure level, the irradiated samples exhibited larger voids following combined irradiations compared with those for irradiation with a single ion species after annealing to 1323 K. During the He + D2 irradiation, D atoms are effectively trapped owing to the defects induced by pre-irradiation with He.

  20. Desorption of polycyclic aromatic hydrocarbons from soot surface: five- and six-ring (C22, C24) PAHs.

    PubMed

    Bedjanian, Yuri; Nguyen, Mai Lan; Guilloteau, Angélique

    2010-03-18

    The kinetics of thermal desorption of five soot-bound nonvolatile (C(22), C(24)) polycyclic aromatic hydrocarbons (benzo(ghi)perylene (BghiP), indeno(1,2,3-cd)pyrene (IdP), anthanthrene (Antha), dibenz(ah)anthracene (DBahA), dibenzo(ae)pyrene (DBaeP)) identified in laboratory-generated kerosene soot were studied over the temperature range 335-370 K in a low pressure flow reactor. The PAH desorption rate constants were measured using off-line HPLC monitoring of their concentrations in soot samples as a function of desorption time. The following Arrhenius expressions were determined for the desorption rate constants of the soot-bound PAHs studied: k(des) = 8.4 x 10(15) exp[-(129.7 +/- 4.4)/RT], 1.0 x 10(16) exp[-(130.6 +/- 6.1)/RT], 1.1 x 10(16) exp[-(131.6 +/- 3.2)/RT], 1.0 x 10(16) exp[-(128.0 +/- 3.9)/RT], and 1.4 x 10(16) exp[-(134.2 +/- 10.7)/RT] (k(des) are in s(-1) and activation energies in kJ mol(-1)) for BghiP, IdP, Antha, DBahA, and DBaeP, respectively. Analysis of the present and previous experimental data showed that PAH-soot binding energies linearly correlate with the number of PAH carbon atoms. The present data and those from previous studies are discussed in the frame of the existing theoretical gas-to-particle partitioning model.