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1

Temperature Programmed Desorption Study of Graphene Oxide  

NASA Astrophysics Data System (ADS)

Graphene oxide is an electrical insulator that shows potential for use in nanoscale electronic devices. An understanding of the thermal stability of graphene oxide sheets is important since the electrical, chemical, and mechanical properties of graphene oxide will change as it is reduced at elevated temperatures. In this study, graphene oxide films were grown by deposition of an aqueous solution of graphene oxide onto oxygen plasma cleaned silicon nitride on silicon substrates. The thermal stability of these films was studied by temperature programmed desorption under ultra-high vacuum conditions up to 350 ^oC. The primary decomposition components of the films are H2O, CO2 and CO. Desorption of these components starts at ˜70 ^oC and is completed by ˜150^oC. Coverage dependent measurements indicate that the desorption kinetics are second order. An activation energy of 162 meV for CO2 desorption has been determined.

Clark, Nicholas; Field, Daniel; Rieman, Simona; Ventrice, Carl; Jung, Inhwa; Yang, Dongxing; Piner, Richard; Ruoff, Rodney

2009-03-01

2

A dynamic calibration technique for temperature programmed desorption spectroscopy  

NASA Astrophysics Data System (ADS)

A novel, rapid and accurate calibration procedure as a means for quantitative gas desorption measurement by temperature programmed desorption (TPD) spectroscopy is presented. Quantitative measurement beyond the linear regime of the instrument is achieved by associating an instantaneous calibrated molar flow rate of gas to the detector response. This technique is based on fundamental methods, and is independently verified by comparison to the hydrogen desorption capacity of a known standard metal hydride with known stoichiometry. The TPD calibration procedure described here may be used for any pure gas, and the accuracy is demonstrated for the specific case of hydrogen.

Hurst, K. E.; Heben, M. J.; Blackburn, J. L.; Gennett, T.; Dillon, A. C.; Parilla, P. A.

2013-02-01

3

Temperature Programmed Desorption Study of Graphene Oxide  

Microsoft Academic Search

Graphene oxide is an electrical insulator that shows potential for use in nanoscale electronic devices. An understanding of the thermal stability of graphene oxide sheets is important since the electrical, chemical, and mechanical properties of graphene oxide will change as it is reduced at elevated temperatures. In this study, graphene oxide films were grown by deposition of an aqueous solution

Nicholas Clark; Daniel Field; Simona Rieman; Carl Ventrice; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

4

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

Microsoft Academic Search

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,

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

2006-01-01

5

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

NASA Astrophysics Data System (ADS)

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide. In order to determine the thermal stability and reduction kinetics of graphene oxide, temperature program desorption (TPD) measurements have been performed on multilayer films of graphene oxide deposited on SiO2/Si(100) substrates. The graphene oxide was exfoliated from the graphite oxide source material by slow-stirring in aqueous solution, which produces single-layer platelets with an average lateral size of ˜10 ?m. From the TPD measurements, it was determined that the decomposition process begins at ˜80 ^oC. The primary desorption products of the graphene oxide films for temperatures up to 300 ^oC are H2O, CO2, and CO, with only trace amounts of O2 being detected. An activation energy of 1.4 eV/molecule was determined by assuming an Arrhenius dependence for the decomposition process.

Ventrice, Carl; Clark, Nicholas; Field, Daniel; Geisler, Heike; Jung, Inhwa; Yang, Dongxing; Piner, Richard; Ruoff, Rodney

2009-10-01

6

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

SciTech Connect

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

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

1991-03-15

7

Design and construction of a semiautomatic temperature programmed desorption apparatus for ultrahigh vacuum  

Microsoft Academic Search

A computer-controlled system that allows acquisition of large volumes of temperature programmed desorption data under ultrahigh vacuum conditions has been designed and tested. The vacuum part of the system consists of a sample mounted on a rotation-translation manipulator, a shielded quadrupole mass spectrometer for the desorption flux measurement, and a collimated molecular beam doser for adsorbate delivery. The experiment involves

Petro Kondratyuk; John T. Yates

2005-01-01

8

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

NASA Astrophysics Data System (ADS)

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.

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

2006-11-01

9

Temperature-Programmed Desorption of Oxalate from the Goethite Surface  

SciTech Connect

The TPD-FTIR technique was used to investigate the relative thermal stabilities and decomposition reactions of different oxalate complexes adsorbed on the dry goethite surface. The measurements showed that important differences in coordination have a considerable impact on the thermal stability of the surface complexes. Three important stages of desorption were identified from both TPD (Figure 1) and FTIR data in the 300-900 K range. Stage I (300-440 K) corresponds to the desorption of weakly-bound oxalate molecules with decomposition pathways characteristic of oxalic acid. Stage II (440-520 K) corresponds to the dehydration of key surface OH2 groups responsible in stabilizing hydrogen-bonded surface complexes. These species can either decompose via typical oxalic acid decomposition pathways or convert to metal-bonded surface complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of all metal-bonded oxalate complexes, proceeding through a two-electron reduction pathway that converts oxalate to CO2. Experiments in the absence of oxalate were used to assess the contributions from dehydration, dehydroxylation and decarbonation reactions from the goethite bulk.

Boily, Jean F.

2007-08-31

10

Interactions of phenylglycine with amorphous solid water studied by temperature-programmed desorption and photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the interactions of phenylglycine (PheGly) with amorphous solid water (ASW) nanolayers (10–50 ML). First, the adsorption and growth of PheGly layers on an AlOx/NiAl(110) surface have been examined. After that, mixed PheGly–ASW layers have been grown on the alumina surface at 110 K. Alternatively, PheGly molecules (from submonolayer to multilayer coverages) have been deposited on top of the ASW surfaces. In mixed PheGly–ASW nanolayers the PheGly phase displays hydrophobic behavior and accumulates near the surfaces of the films, while top-deposited PheGly wets the ASW films forming closed overlayers at low coverages. H2O desorption from the PheGly–ASW films is strongly influenced by the PheGly molecules, i.e., the crystallization of ASW is partially inhibited in the vicinity of the amino acid and a lower desorption temperature of H2O molecules than from pure ASW layers was detected. Thicker PheGly overlayers on ASW provide a kinetic restriction to H2O desorption from the underlying ASW layers until the PheGly molecules become mobile and develop pathways for water desorption at higher temperatures. The results are discussed with respect to the previously obtained data for glycine–ASW layered systems. It has been demonstrated that the substitution of the hydrogen atom in glycine with a phenyl group does not lead to detectable changes in the pathways of ASW desorption. However, desorption of PheGly differs from the desorption of glycine from the similarly structured glycine–ASW nanolayers. The differences are interpreted in terms of adsorbate–adsorbate and adsorbate–substrate interactions.

Tzvetkov, George; Netzer, Falko P.

2013-07-01

11

Analyte separation utilizing temperature programmed desorption of a preconcentrator mesh  

DOEpatents

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.

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

2007-11-27

12

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

SciTech Connect

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.

Lombardo, S.J. (California Inst. of Tech., Pasadena, CA (USA). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (USA))

1990-08-01

13

TEMPERATURE-PROGRAMMED DESORPTION: PRINCIPLES, INSTRUMENT DESIGN, AND DEMONSTRATION WITH NAALH4  

SciTech Connect

This article is a brief introduction to temperature-programmed desorption (TPD), an analytical technique devised to analyze, in this case, materials for their potential as hydrogen storage materials. The principles and requirements of TPD are explained and the different components of a generic TPD apparatus are described. The construction of a modified TPD instrument from commercially available components is reported together with the control and acquisition technique used to create a TPD spectrum. The chemical and instrumental parameters to be considered in a typical TPD experiment and the analytical utility of the technique are demonstrated by the dehydrogenation of titanium-doped NaAlH{sub 4} by means of thermally programmed desorption.

Stowe, A; Ragaiy Zidan, R

2006-11-07

14

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

SciTech Connect

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.

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

2007-11-15

15

Temperature programmed desorption characterization of oxidized uranium surfaces: Relation to some gas-uranium reactions  

SciTech Connect

The chemisorption characteristics and surface composition of oxidation overlayers developing on metals when exposed to oxidizing atmospheres are important in determining the protective ability of these layers against certain gas-phase reactions (e.g., corrosion and hydriding). In the present study, a special setup of supersonic molecular beam-temperature-programmed desorption was utilized to determine the different chemisorbed species present on oxidized uranium surfaces. The main identified species included water (in different binding forms) and hydrogen. The latter hydrogen originates from the water-uranium oxidation reaction, which produces uranium dioxide and two types of hydrogen: a near surface hydride and a surface-chemisorbed form that desorbs at a lower temperature than that of the hydride. Assignments of the different water desorption peaks to different binding sites were proposed. In general, four water desorption features were identified (labeled W{sub 0}, W{sub 1}, W{sub 2}, and W{sub 3}, respectively, in the order of increasing desorption temperatures). These features correspond to a reversibly chemisorbed molecular form (W{sub 0}), a more tightly bound water (chemisorbed on different type of oxide sites) or hydroxyl clusters (W{sub 1}), and strongly bounded (possibly isolated) hydroxyl groups (W{sub 2}). The highest temperature peak (W{sub 3}) is related to the formation of complex water-carbo-oxy compounds and is present only on oxidation overlayers, which contain proper chemisorbed carbo-oxy species. The relation of the water and hydrogen thermal release behavior to some problems addressed to certain effects observed in hydrogen-uranium and water-uranium reactions is discussed. For the latter, a microscopic mechanism is proposed.

Danon, A.; Koresh, J.E.; Mintz, M.H.

1999-08-31

16

Determination of Acid/Base Properties by Temperature Programmed Desorption (TPD) and Adsorption Calorimetry  

NASA Astrophysics Data System (ADS)

The characterization of the acidity of zeolites and related materials is of great importance for applications of these materials, particularly in the petrochemical industry and environmental sciences. This chapter provides a comparison of the two most widely used techniques for the study of acid/base properties of zeolites, namely temperature-programmed desorption and adsorption calorimetry. The information needed to perform and interpret these experiments as well as advantages and limitations of these methods are summarized. The curves and data obtained for the two most studied zeolites Y and ZSM-5 are discussed, which can be particularly useful for young researchers in this field.

Damjanovi?, Ljiljana; Auroux, Aline

17

Interaction of acetone with single wall carbon nanotubes at cryogenic temperatures: a combined temperature programmed desorption and theoretical study.  

PubMed

The interaction of acetone with single wall carbon nanotubes (SWCNTs) at low temperatures was studied by a combination of temperature programmed desorption (TPD) and dispersion-augmented density-functional-based tight binding (DFTB-D) theoretical simulations. On the basis of the results of the TPD study and theoretical simulations, the desorption peaks of acetone can be assigned to the following adsorption sites: (i) sites with energy of approximately 75 kJ mol (-1) ( T des approximately 300 K)endohedral sites of small diameter nanotubes ( approximately 7.7 A); (ii) sites with energy 40-68 kJ mol (-1) ( T des approximately 240 K)acetone adsorption on accessible interstitial, groove sites, and endohedral sites of larger nanotubes ( approximately 14 A); (iii) sites with energy 25-42 kJ mol (-1) ( T des approximately 140 K)acetone adsorption on external walls of SWCNTs and multilayer adsorption. Oxidatively purified SWCNTs have limited access to endohedral sites due to the presence of oxygen functionalities. Oxygen functionalities can be removed by annealing to elevated temperature (900 K) opening access to endohedral sites of nanotubes. Nonpurified, as-received SWCNTs are characterized by limited access for acetone to endohedral sites even after annealing to elevated temperatures (900 K). Annealing of both purified and as-produced SWCNTs to high temperatures (1400 K) leads to reduction of access for acetone molecules to endohedral sites of small nanotubes, probably due to defect self-healing and cap formation at the ends of SWCNTs. No chemical interaction between acetone and SWCNTs was detected for low temperature adsorption experiments. Theoretical simulations of acetone adsorption on finite pristine SWCNTs of different diameters suggest a clear relationship of the adsorption energy with tube sidewall curvature. Adsorption of acetone is due to dispersion forces, with its C-O bond either parallel to the surface or O pointing away from it. No significant charge transfer or polarization was found. Carbon black was used to model amorphous carbonaceous impurities present in as-produced SWCNTs. Desorption of acetone from carbon black revealed two peaks at approximately 140 and approximately 180-230 K, similar to two acetone desorption peaks from SWCNTs. The characteristic feature of acetone desorption from SWCNTs was peak at approximately 300 K that was not observed for carbon black. Care should be taken when assigning TPD peaks for molecules desorbing from carbon nanotubes as amorphous carbon can interfere. PMID:18613702

Kazachkin, Dmitry; Nishimura, Yoshifumi; Irle, Stephan; Morokuma, Keiji; Vidic, Radisav D; Borguet, Eric

2008-07-10

18

Characterization of early-stage coal oxidation by temperature-programmed desorption  

SciTech Connect

To obtain representative temperature-programmed desorption (TPD) profiles of young oxidized chars up to 1650{degree}C with minimal reactor wall interferences, the chemistry and physics of four ceramic materials has been critically reviewed. A two-staged experimental apparatus is then uniquely designed to produce chars in an Al{sub 2}O{sub 3} flow reactor with 1-21% O{sub 2} followed by in situ TPD with a SiC tube. Comparison of TPD profiles of oxidized chars with those from pyrolyzed chars and ashes suggests early-stage char oxidation is profoundly influenced by oxygen from three sources: organic oxygen, mineral matters, and gas phase O{sub 2}. Young chars oxidized at 1000{degree}C with less than 0.3 s residence time shows CO desorption peaks during TPD at three distinct temperatures: 730, 1280, and 1560{degree}C. The peaks at 730{degree}C are mainly caused by incomplete devolatilization. The peaks at 1280{degree}C mainly represent desorption of stable surface oxides and incomplete devolatilization. Increasing the gas phase oxidants notably increases the amount of stable surface oxides. The broad peaks between 1400 and 1650{degree}C are attributed to the reactions of oxidants decomposed from minerals and carbon in the char or SiC tube. Gas-phase oxygen shifts these reactions to lower temperatures. Detailed oxygen balance based on the CO and CO{sub 2} yields and elemental compositions of both pyrolysis and oxidized chars reveals that oxygen uptakes are very high, +0.056 mg O per mg of carbon, in chars derived from bituminous coal, whereas lignite chars show negative oxygen uptake, -0.020 mg O per mg of carbon, in char. Indeed, lignite char seems to possess little amount of stable surface oxides other than those contributed by the minerals. The extensive emissions of CO from lignite chars during TPD seem to suggest that either O{sub 2} or minerals promotes the oxygen transfer on char surface and subsequent carbon oxidation. 85 refs., 5 figs., 4 tabs.

Wei-Yin Chen; Guang Shi; Shaolong Wan [University of Mississippi, University, MI (United States). Department of Chemical Engineering

2008-11-15

19

Desorption of H sub 2 O and H sub 2 from steel and LiAlO sub 2 by temperature programmed desorption  

SciTech Connect

Temperature programmed desorption (TPD) measurements with a steel sample tube and helium sweep gas in progress to provide data describing the kinetics of desorption of H{sub 2}O(g) and H{sub 2}(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H{sub 2}O being consumed and H{sub 2} being evolved. There is also evidence of some dissolution of H{sub 2} in the steel. However, it is possible to stabilize the steel in the absence of added H{sub 2} so that useful desorption measurements with H{sub 2}O(g) can be made. Initial work was on the LiA1O{sub 2} {minus} H{sub 2}O(g) system. Fresh samples of LiA1O{sub 2} bear large amounts of absorbed H{sub 2}O. TPD spectra were measured for LiA1O{sub 2} that had been equilibrated in a helium stream with 200 ppm H{sub 2}O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied. Questions of possible peak overlap still remain to be resolved. An activation energy for desorption of H{sub 2}O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. This result agrees with the values reported in the literature for decomposition of LiOH, and suggests that some sites on LiA1O{sub 2} might resemble sites on Li{sub 2}O on their adsorptive properties. For a 773 K equilibration, the activation energy of desorption appears considerably higher. 6 refs., 4 figs.

Fischer, A.K.; Johnson, C.E.

1989-01-01

20

Sum-frequency generation and temperature-programed desorption studies of formic acid on MgO(001) surfaces  

Microsoft Academic Search

Adsorption and decomposition of formic acid on MgO(001) surfaces were studied by means of Sum-Frequency Generation (SFG), Temperature-Programed Desorption (TPD) and Atomic Force Microscopy (AFM). Formic acid was dissociatively adsorbed on MgO(001) surfaces at room temperature. From SFG and TPD measurements, the existence of several different types of formate species was deduced and all species mainly decomposed into CO and

K. Domen; H. Yamamoto; N. Watanabe; A. Wada; C. Hirose

1995-01-01

21

Acidity of dealuminated ?-zeolites via coupled nh 3stepwise temperature programmed desorption (STPD) and FT-IR spectroscopy  

Microsoft Academic Search

Ammonia stepwise temperature programmed desorption (STPD) and FT-IR spectroscopy have been used to study the acidity of dealuminated ?-zeolites with Si\\/Al ratios in the range of 14.5 to 132. A carefully optimized temperature profile starting at 150 °C (in order to exclude physisorbed NH3) revealed five peaks at about 180 °C, 250 °C, 350 °C, 440 °C, and 540 °C.

Gary M. Robb; Wenmin Zhang; Panagiotis G. Smirniotis

1998-01-01

22

Comparing deuterium retention in tungsten films measured by temperature programmed desorption and nuclear reaction analysis  

NASA Astrophysics Data System (ADS)

Tungsten (W) films with thicknesses ranging between 1 and 12 ?m deposited by magnetron sputtering on silicon substrates were used as a model system for comparing the deuterium (D) retention measured by both temperature programmed desorption (TPD) and nuclear reaction analysis (NRA). Samples were loaded with deuterium ex-situ with an ECR plasma at 370 and 600 K with an energy of 38 eV per deuteron. To avoid diffusion of D into the silicon substrate and to increase adhesion a copper interlayer was applied. The results show that all implanted D atoms were retained exclusively in the W films. The distribution of D is homogenous throughout the W layer with an atomic fraction of 3 ± 0.4 × 10-3. With increasing W thickness the D profile extends to correspondingly larger depths with practically identical D concentration. For W films with a thickness lower than the NRA information depth of about 8 ?m the total retained D amount measured by TPD and NRA is in excellent agreement. As expected, for films thicker than the NRA information depth, TPD deviates from NRA.

Wang, P.; Jacob, W.; Gao, L.; Dürbeck, T.; Schwarz-Selinger, T.

2013-04-01

23

Tube effects and the kinetics of desorption of H sub 2 O/H sub 2 from LiAlO sub 2 by temperature programmed desorption measurements  

SciTech Connect

Temperature programmed desorption (TPD) measurements are in progress to provide data describing the kinetics of desorption of H{sub 2}O(g) and H{sub 2}(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H{sub 2}O being consumed and H{sub 2} being evolved. There is also evidence of some dissolution of H{sub 2} in the steel. However, it is possible to stabilize the tube in the absence of added H{sub 2} so that useful measurements with H{sub 2}O(g) can be made. Initial work is on the LiAlO{sub 2}-H{sub 2}O(g) system. Fresh samples of LiAlO{sub 2} bear large amounts of adsorbed H{sub 2}O. TPD spectra were measured for LiAlO{sub 2} that had been equilibrated with 200 ppM H{sub 2}O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied. There still remain questions of possible peak overlap to resolve for all cases. An activation energy of desorption of H{sub 2}O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. When compared with the same value reported in the literature for decomposition of LiOH, this result suggests that some sites on LiAlO{sub 2} might resemble sites on Li{sub 2}O in their adsorptive properties. For the 773 K equilibration, the activation energy of desorption appears considerably higher. 6 refs., 4 figs.

Fischer, A.K.; Johnson, C.E.

1989-01-01

24

Processes for desorption from LiAlO sub 2 treated with H sub 2 as studied by temperature programmed desorption  

SciTech Connect

The energetics and kinetics of the evolution of H{sub 2}O and H{sub 2} from LiAlO{sub 2} are being studied by the temperature programmed desorption technique. The concentrations of H{sub 2}, H{sub 2}O, N{sub 2}, and O{sub 2} in a helium stream during a temperature ramp are measured simultaneously with a mass spectrometer. Blank experiments with an empty sample tube showed that square wave spikes of H{sub 2} introduced into the helium gas stream were severely distorted by reaction with the tube walls. The tube could be stabilized, however, by sufficiently prolonged heat treatment with H{sub 2} so that H{sub 2} peaks would not be distorted up to approximately 923 K(650{degree}C). The amount of H{sub 2}adsorption/desorption is small compared to the amount of H{sub 2}O adsorption/desorption. After prolonged treatment with helium containing 990 ppm H{sub 2} at 400{degree}C, H{sub 2}O evolution into the He-H{sub 2} stream was observed during 473 to 1023 K (200 to 750{degree}C) ramps at rates of 2 or 5.6 K/min. The different peak shapes reflecting this process were deconvoluted to show that they are composites of only 2 or 3 reproducible processes. The activation energies and pre-exponential terms was evaluated. The different behavior originates in the differences among different surface sites for adsorption. The interpretation of higher temperature peaks (above 873 K (650{degree}C)) must still consider the possibility of contributions from interactions with steel walls. It was found that H{sub 2} enhances evolution of N{sub 2} from the steel. 1 tab., 6 figs., 11 refs.

Fischer, A.K.

1990-01-01

25

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

PubMed

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

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

2008-01-01

26

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

SciTech Connect

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

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

2007-05-23

27

Thermal stability of water and hydroxyl on the surface of the Moon from temperature-programmed desorption measurements of lunar analog materials  

NASA Astrophysics Data System (ADS)

The adsorption of molecular water onto lunar analog materials was investigated under ultra-high vacuum with the goal to better understand the thermal stability and evolution of water on the lunar surface. Temperature-programmed desorption (TPD) experiments show that lunar-analog basaltic-composition glass is hydrophobic, with water-water interactions dominating over surface chemisorption. This suggests that lunar agglutinates will tend not to adsorb water at temperatures above where water clusters and multilayer ice forms. The basalt JSC-1A lunar mare analog, which is a complex mixture of minerals and glass, adsorbs water above 180 K with an adsorption profile that extends to 400 K, showing evidence for a continuum of water adsorption sites. Bancroft albite adsorbs more water, more strongly, than JSC-1A, with a well-defined desorption peak near 225 K. This suggests that mineral surfaces will adsorb more water than mare or mature (glassy, agglutinate rich) surfaces and may explain the association of water with fresh feldspathic craters at high latitudes. The activation energies for the thermal desorption of water from these materials were determined, and along with values from the literature, used to model the grain-to-grain migration of water within the lunar regolith. These models suggest that a combination of recombinative desorption of hydroxyl along with molecular desorption of water and its subsequent migration within and out of the regolith may explain observed diurnal variations in the distribution of water and hydroxyl on the illuminated Moon.

Hibbitts, C. A.; Grieves, G. A.; Poston, M. J.; Dyar, M. D.; Alexandrov, A. B.; Johnson, M. A.; Orlando, T. M.

2011-05-01

28

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

SciTech Connect

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

Tewell, Craig R.

2002-08-19

29

Characterization of the acidity of ultrastable Y, mordenite, and ZSM-12 via NH 3stepwise temperature programmed desorption and Fourier transform infrared spectroscopy  

Microsoft Academic Search

The acidity of ultrastable Y (USY), mordenite, and ZSM-12 of variable Si\\/Al ratios has been characterized by coupling NH3-stepwise temperature programmed desorption (STPD) and FT-IR. The former technique allows us to quantify accurately the ammonia chemisorbed on acid sites of different strengths. In contrast to other acidic oxide catalysts, it was found that protonated zeolites possess distinct limits of acid

Wenmin Zhang; Eric C. Burckle; Panagiotis G. Smirniotis

1999-01-01

30

Evaluation of solid lubricants: temperature programmed desorption of MOS/sub 2/ on molybdenum and of ion-implanted MOS/sub 2/ on molybdenum. Final report  

SciTech Connect

Thermal programmed desorption (TPD) is utilized in order to assess the lubricating properties of metal dichalcogenide films applied to a number of metal substrates. TPD spectra documenting desorption and decomposition products were analyzed for MoS/sub 2/ burnished on molybdenum metal with and without subsequent 86-kV nitrogen ion implantation. Desorption order, rate, energy, and the pre-exponential of evolved lubricant and nitrogen species from the molybdenum substrates were determined. The surface chemistry of heated lubricant-substrate system was investigated by means of x-ray photoelectron spectroscopy (XPS).

Burns, R.P.; Piece, D.E.; Dauplaise, H.M.; Gabriel, K.A.; Mizerka, L.J.

1988-11-01

31

Measurement of the Reversible Hydrogen Storage Capacity of Milligram Ti-6A1-4V Alloy Samples with Temperature Programmed Desorption and Volumetric Techniques  

SciTech Connect

We report the results of a study using temperature programmed desorption (TPD) and a volumetric sorption technique to measure the hydrogen storage capacity of the Ti-6Al-4V alloy. Samples of various sizes and surface treatments were studied to obtain a statistically meaningful value for the maximum hydrogen storage capacity, as well as to understand the effect of sample size, sample oxidation, and hydrogen charging conditions on the measured capacity. We find a maximum reversible hydrogen storage capacity of {approx} 3.76 wt% with hydrogen exposures near ambient temperature and pressure. This value is higher than any reported in the literature previously, possibly due to the utilization of very small particles and rapid hydrogen exposures, which allow for equilibration times of approximately 1 h. Comparison of a variety of samples indicates that the measured hydrogen capacity is affected by surface oxidation. Samples generated in a strongly oxidizing environment exhibit decreased hydrogen uptake. The implications of these results are discussed with regards to previously reported capacity values in the literature.

Blackburn, J. L.; Parilla, P. A.; Gennett, T.; Hurst, K. E.; Dillon, A. C.; Heben, M. J.

2007-01-01

32

Application of Temperature Dependent Computerized Control of Desorption for Catalyst Surface Characterization.  

National Technical Information Service (NTIS)

The dissertation discusses the applications of temperature-programmed desorption and its limits in the characterisation of catalyst surfaces and in heterogeneous catalysis. Further, the quantitative information of the TPD spectra is critically reviewed. (...

E. Morales de Leguizamon

1984-01-01

33

Temperature-programmed decomposition desorption of mercury species over activated carbon sorbents for mercury removal from coal-derived fuel gas  

SciTech Connect

The mercury (Hg{sup 0}) removal process for coal-derived fuel gas in the integrated gasification combined cycle (IGCC) process will be one of the important issues for the development of a clean and highly efficient coal power generation system. Recently, iron-based sorbents, such as iron oxide (Fe{sub 2}O{sub 3}), supported iron oxides on TiO{sub 2}, and iron sulfides, were proposed as active mercury sorbents. The H{sub 2}S is one of the main impurity compounds in coal-derived fuel gas; therefore, H{sub 2}S injection is not necessary in this system. HCl is also another impurity in coal-derived fuel gas. In this study, the contribution of HCl to the mercury removal from coal-derived fuel gas by a commercial activated carbon (AC) was studied using a temperature-programmed decomposition desorption (TPDD) technique. The TPDD technique was applied to understand the decomposition characteristics of the mercury species on the sorbents. The Hg{sup 0}-removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80-300{sup o}C using simulated fuel gas and a commercial AC, and the TPDD experiments were carried out in a U-tube reactor in an inert carrier gas (He or N{sub 2}) after mercury removal. The following results were obtained from this study: (1) HCl contributed to the mercury removal from the coal-derived fuel gas by the AC. (2) The mercury species captured on the AC in the HCl{sup -} and H{sub 2}S-presence system was more stable than that of the H{sub 2}S-presence system. (3) The stability of the mercury surface species formed on the AC in the H{sub 2}S-absence and HCl-presence system was similar to that of mercury chloride (HgClx) species. 25 refs., 12 figs., 1 tab.

M. Azhar Uddin; Masaki Ozaki; Eiji Sasaoka; Shengji Wu [Okayama University, Okayama (Japan). Faculty of Environmental Science and Technology

2009-09-15

34

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

NASA Astrophysics Data System (ADS)

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

Li, Huijuan; Jiang, Xiaoyuan; Zheng, Xiaoming

2013-09-01

35

Anomalous low-temperature ``post-desorption'' from solid nitrogen  

NASA Astrophysics Data System (ADS)

Anomalous low-temperature post-desorption (ALTpD) from the surface of nominally pure solid nitrogen preliminary irradiated by an electron beam was detected for the first time. The study was performed using a combination of activation spectroscopy methods--thermally stimulated exoelectron emission (TSEE) and spectrally resolved thermally stimulated luminescence (TSL)--with detection of the ALTpD yield. Charge recombination reactions are considered to be the stimulating factor for the desorption from pre-irradiated ?-phase solid nitrogen.

Savchenko, E. V.; Khyzhniy, I. V.; Uyutnov, S. A.; Ponomaryov, A. N.; Gumenchuk, G. B.; Bondybey, V. E.

2013-05-01

36

Water adsorption and desorption on microporous solids at elevated temperature  

Microsoft Academic Search

Summary An accurate gravimetric method was used to explore water adsorption\\/desorption isotherms between 105 and to 250°C for a number of synthetic and natural porous solids including controlled pore glass, activated carbon fiber monoliths, natural zeolites, pillared clay, and geothermal reservoir rocks.  The main goal of this work was to evaluate water adsorption results, in particular temperature dependence of hysteresis,

M. S. Gruszkiewicz; J. M. Simonson; T. D. Burchell; D. R. Cole

2005-01-01

37

A study of the reactions of ethanol on CeO{sub 2} and Pd/CeO{sub 2} by steady state reactions, temperature programmed desorption, and in situ FT-IR  

SciTech Connect

The reaction of ethanol on unreduced and H{sub 2}-reduced CeO{sub 2} and 1 wt% Pd/CeO{sub 2} has been investigated by steady state reactions, temperature programmed desorption (TPD), and in situ Fourier transform infrared (FT-IR) spectroscopy. Steady state reactions have shown a zero reaction order dependency for diatomic oxygen at and above 20%, while the addition of Pd to CeO{sub 2} decreases the apparent activation energy of the reaction from 75 kJ/mol on CeO{sub 2} alone to 40 kJ/mol (Pd/CeO{sub 2}). TPD experiments following ethanol adsorption on both CeO{sub 2} and Pd/CeO{sub 2} have shown desorption profiles corresponding to unreacted ethanol and various reaction and decomposition products (acetaldehyde, acetone, CO, CO{sub 2}, and methane). Ethanol conversion to reaction products was increased by the addition of Pd, from 15 to 30% on CeO{sub 2} and H{sub 2}-reduced CeO{sub 2}, to 71 and 63% on Pd/CeO{sub 2} and H{sub 2}-reduced Pd/CeO{sub 2}, respectively.

Yee, A.; Morrison, S.J.; Idriss, H. [Univ. of Auckland (New Zealand)

1999-09-10

38

Electronic Desorption from Internal Surfaces of Porous Low Temperature Ice  

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

39

CO interaction with ultrathin MgO films on a Mo(100) surface studied by infrared reflection--absorption spectroscopy, temperature programmed desorption, and x-ray photoelectron spectroscopy  

SciTech Connect

The interaction of CO with MgO ultrathin films grown on a Mo(100) surface is studied using infrared reflection--absorption spectroscopy, temperature programmed thermal desorption (TPD), and x-ray photoelectron spectroscopy. CO adsorbed on 7 ML of MgO shows an infrared band at 2178 cm{sup {minus}1}. This blue-shift of the CO stretching frequency relative to that of CO in the gas phase (2143 cm{sup {minus}1}) is attributed to electron charge transfer from the CO 5{sigma} orbital to the MgO surface. It is further shown that CO adsorption induces a 0.4 eV shift in the Mg(2{ital p}) and O(1{ital s}) core levels of the MgO thin films to lower binding energy, consistent with the charge transfer from CO molecules to the MgO thin films. The TPD spectra indicate that CO molecules on the MgO thin films desorb in the 100--180 K sample temperature range. The CO adsorption heat on 7 ML of MgO is deduced to be 9.9 kcal/mol using an isothermal adsorption method.

He, J.; Corneille, J.S.; Estrada, C.A.; Wu, M.; Goodman, D.W. (Department of Chemistry, Texas A M University, College Station, Texas 77843-3255 (United States))

1992-07-01

40

The decomposition and chemistry of Ru3(CO)12 on TiO2(1 1 0) studied with X-ray photoelectron spectroscopy and temperature programmed desorption  

NASA Astrophysics Data System (ADS)

The decomposition process of triruthenium dodecacarbonyl (Ru3(CO)12) on single crystal TiO2(1 1 0) has been investigated using synchrotron-based high resolution photoemission spectroscopy and temperature programmed desorption (TPD). Ruthenium carbonyl adsorbs molecularly on TiO2(1 1 0) at 100 K. When dosing at room temperature, the molecule dissociatively adsorbs forming a Ru3(CO)m (m ? 10) species on the surface. TPD spectra for ruthenium carbonyl dosed at 100 K and 300 K are quite different in peak numbers and shape, indicating that the ruthenium carbonyl decomposition is sensitive to the preparation procedure. Both TPD and photoemission demonstrate that around 700 K, the decarbonylation process is completed yielding almost pure Ru particles. A small amount of CO adsorbs on the obtained Ru particles after large CO exposures (60 100 L) at 300 K. The Ru particles can be oxidized to form RuO2 at 600 K with an O2 pressure of ˜1 × 10-6 Torr (>400 L exposure). In addition, the chemical activity of the Ru metal particles dispersed on TiO2(1 1 0) has also been examined with SO2 and compared to that of a Ru(0 0 1) single crystal. SO2 is easily decomposed by the Ru particles at room temperature, producing S and O adatoms. SO4 is the main product of the reaction of SO2 with the titania support, and the presence of the Ru particles favors a SO4,ads ? Sads + nOads + mO2,gas transformation at elevated temperature.

Zhao, Xueying; Hrbek, Jan; Rodriguez, José A.

2005-01-01

41

Temperature and pressure dependence of molecular adsorption on single wall carbon nanotubes and the existence of an “adsorption\\/desorption pressure gap”  

Microsoft Academic Search

The interaction of acetone with single wall carbon nanotubes (SWCNTs) was studied by temperature programmed desorption with mass spectrometry (TPD-MS), after reflux, sonication, or exposure to 7.6Torr of acetone vapors at room temperature. Acetone molecules adsorb strongly on SWCNTs desorbing at ?400–900K, corresponding to desorption energies of ?100–225kJ\\/mol, as intact molecules. Exchange of intact adsorbed molecules with gas phase species

Dmitry V. Kazachkin; Yoshifumi Nishimura; Stephan Irle; Xue Feng; Radisav Vidic; Eric Borguet

2010-01-01

42

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

EPA Science Inventory

Isothermal desorption rates were measured at 15, 30, and 60 C for trichloroethylene (TCE) on a silica gel, an aquifer sediment, a soil, a sand fraction, and a clay and silt fraction, all at 100% relative humidity. Temperature-st...

43

Reversibility, dopant desorption, and tunneling in the temperature-dependent conductivity of type-separated, conductive carbon nanotube networks.  

PubMed

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(s)) exhibits an irreversible increase with temperature above approximately 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. PMID:19206438

Barnes, Teresa M; Blackburn, Jeffrey L; van de Lagemaat, Jao; Coutts, Timothy J; Heben, Michael J

2008-09-23

44

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

SciTech Connect

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.

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

2008-09-01

45

Temperature-dependent CO desorption kinetics on supported gold nanoparticles: Relevance to clean hydrogen production and fuel cell systems  

Microsoft Academic Search

The influence of the temperature on the CO desorption process was studied on supported gold nanoparticles using isotopic exchange experiments and mass spectrometric detection. CO desorption kinetics data were measured for a range of temperature from 25 to 150 °C and for a fixed CO concentration of 1000 ppm. The measured temperature-dependent kinetics data were discussed with relation to the CO tolerance

A. Pitois; A. Pilenga; A. Pfrang; G. Tsotridis

2011-01-01

46

Experimental investigation of the effect of temperature on the first desorption isotherm of concrete  

SciTech Connect

In the framework of the radioactive waste management in France, interim storage concrete structures should be submitted to temperatures up to 80 deg. C and subsequent desiccation. The impact of temperature on the sorption properties of concretes has been poorly studied and results are scarce. An experimental campaign was thus carried out to characterize the first desorption isotherms of a modern concrete at 30 deg. C and 80 deg. C. The results show a significant influence of the temperature increase that will have to be accounted for the durability assessment of the long-term interim storage concrete structures. Investigating the causes of these modifications, it appeared that desorption induced by temperature might be the principal mechanism rather than microstructure alteration and water properties evolution.

Poyet, Stephane, E-mail: stephane.poyet@cea.f [CEA, DEN, DPC, SCCME, Laboratoire d'Etude du Comportement des Betons et des Argiles, F-91191 Gif-sur-Yvette Cedex (France)

2009-11-15

47

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...

48

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. he Superfund Site soil tested was a fine sandy soil contaminated with creosote. n optimum operating temperature of 550 deg...

49

Desorption of InSb(001) native oxide and surface smoothing induced by low temperature annealing under molecular hydrogen flow  

Microsoft Academic Search

The preparation of InSb (001) oxygen-free surfaces by thermal annealing at relatively low temperatures under molecular hydrogen flow is reported. This process is compared with thermal oxide desorption (TOD) at 400 °C under ultrahigh vacuum conditions. Molecular hydrogen cleaning (MHC) at substrate temperature of 250 °C and at hydrogen pressure of 5×10-6 Torr resulted in complete desorption of the native

R. Tessler; C. Saguy; O. Klin; S. Greenberg; E. Weiss; R. Akhvlediani; R. Edrei; A. Hoffman

2007-01-01

50

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

SciTech Connect

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.

Woo, Sung-Jae [KAIST, Daejeon, Republic of Korea; Lee, Eui-Sup [KAIST, Daejeon, Republic of Korea; Yoon, Mina [ORNL; Yong-Hyun, Kim [KAIST, Daejeon, Republic of Korea

2013-01-01

51

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

PubMed

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

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

2003-06-15

52

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

Microsoft Academic Search

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide.

Carl Ventrice; Nicholas Clark; Daniel Field; Heike Geisler; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

53

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

54

Deactivation of titanium during temperature-induced hydrogen absorption–desorption cycling  

Microsoft Academic Search

The cyclic stability of metallic titanium during absorption–desorption runs in continuous flow system has been studied in the presence of variable level of impurities such as H2O, O2 and N2 in argon and helium flows. Hydrogen absorption–desorption cycles performed in vacuo were reproducible with respect to the absorption rates and uptakes, while absorption–desorption cycles carried out in the flows of

I. N. Filimonov; V. V. Yuschenko; A. V. Smirnov; S. N. Nesterenko; I. V. Dobryakova; I. I. Ivanova; E. N. Lubnin; L. Galperin; R. H. Jensen

2005-01-01

55

Electronic desorption from low temperature ices and analogs of outer solar system surfaces  

NASA Astrophysics Data System (ADS)

Low energy electron induced radiolysis of ices and surrogates of outer solar system bodies such as icy moons and comets have been investigated. Low energy electrons are effective simulants of high energy charged particle irradiation. Molecular hydrogen emission from comets is used to gain information about the formation temperature and isotopic branching in these primordial solar system objects. Long term storage of comets in the Kuiper belt and Oort cloud can subject these objects to space weathering due to galactic cosmic rays and other radiation. Stimulated desorption of atomic and molecular hydrogen and oxygen occur from these ices as well as water group ions. Yields and internal energy distributions of H2 and D2 from laboratory ices have been measured. Ortho-para hydrogen spin isomers have been observed and their equilibration temperatures determined. These spin isomers carry information about the formation temperature of the ice as well as the mechanisms of space weathering that can influence interpretation of the origin and evolution of ice covered bodies.

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

2009-12-01

56

Electron-Stimulated Desorption of Iodine Atoms from KI(100): An Energy and Temperature Dependent Study  

SciTech Connect

We have studied the electron-stimulated desorption (ESD) of neutral atomic iodine from single crystals of KI(100) using time-of-flight laser resonance enhanced multiphoton ionization spectroscopy and quadrupole mass spectrometry. The measured iodine velocty distributions have thermal and non-thermal components. The yield of the thermal component increases with increasing substrate temperature, whereas the yield of the non-thermal component decreases slightly with temperature. The ESD rate for the thermal component decreases with increasing pulse-width, unlike the rate for the non-thermal component, which is independent of pulse-width. Measurements of ESD yields vs. incident electron energy indicate a threshold of ~5.5 eV. The data collectively indicated that non-thermal ESD of KI involves exciton decay at the surface. The temperature and pulse-width dependence of the thermal component is consistent with thermally assisted decay of bulk self-trapped excitons, H-center diffusion and trapping at metastable defects.

Alexandrov, Alexandr B.; Piacentini, Mario; Tonkyn, Russell G.; Sieger, Matthew T.; Zema, N.; Orlando, Thomas M.

2000-04-20

57

Dynamic Observation of Ag Desorption Process on Si(111) Surface by High-Temperature Scanning Tunneling Microscopy  

NASA Astrophysics Data System (ADS)

The dynamical isothermal desorption process of Ag adsorbed on a Si(111) surface kept at about 600°C was observed by means of high-temperature scanning tunneling microscopy (HT-STM). The desorption of Ag caused a transition from the \\sqrt{3}×\\sqrt{3}-Ag phase to the 3× 1-Ag phase having a lower Ag coverage, followed by another transition to the 7× 7 phase. In the respective phase transitions, the produced phases extended from steps and domain boundaries. The number of Si atoms moved is discussed for the case of the phase transition from the 3× 1-Ag structure to the 7× 7 structure.

Sato, Tomoshige; Sueyoshi, Takashi; Kitamura, Shin-ichi; Iwatsuki, Masashi

1993-06-01

58

Adsorption and desorption of hydrogen on graphene with dimer conversion  

NASA Astrophysics Data System (ADS)

We apply non-equilibrium thermodynamics to describe the adsorption and desorption of molecular hydrogen on graphene. Lateral interactions, precursor states in both adsorption and desorption, and limited dimer conversion are important to explain semi-quantitatively the main features of temperature-programmed desorption spectra. All energy and vibrational parameters are taken from density functional calculations. Deficiencies in previous attempts are discussed. We also point out the need for a multi-dimensional dynamic theory.

Xia, Yu; Wang, Weiliang; Li, Zhibing; Kreuzer, H. Juergen

2013-11-01

59

Field desorption of lithium fluoride  

SciTech Connect

Layers of lithium fluoride (LiF), [similar to]10 nm thick, were field desorbed from iridium substrates at temperatures between 25 and 600 [degree]C. The electric field was increased until desorption of the salt layer occurred. Combined mass spectroscopy and field desorption microscopy characterized the desorption process. During desorption, ions of the form (LiF)[sub [ital n

Stintz, A.; Panitz, J.A. (Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States))

1995-03-01

60

Morphology and hydrogen desorption characteristic of Ni-TiN nanocomposite particle prepared by RF plasma  

Microsoft Academic Search

Ni-TiN nanocomposite particles are prepared by RF plasma. Dumbbell-like and dice-like morphologies are seen. Hydrogen sorption-desorption characteristics of the nanocomposite particles were examined by temperature-programmed desorption measurements. Hydrogen desorption at 500–700 K is observed, which implies that a new adsorption state of hydrogen exists. Hydrogen desorption characteristics are not so influenced by coadsorption of CO. The results are compared with

Y. Sakka; H. Okuyama; T. Uchikoshi; S. Ohno

1997-01-01

61

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

EPA Science Inventory

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

62

Deactivation of titanium during temperature-induced hydrogen absorption–desorption cycling  

Microsoft Academic Search

Thermoprogrammed hydrogen absorption and desorption on titanium has been studied in the presence of propane and propene. Consecutive absorption–desorption cycles performed in steady flows of H2\\/C3H8 and H2\\/C3H6 showed fast deactivation of titanium, as manifested by a 10-fold drop in hydrogen uptakes in the second cycle. Reaction of titanium with hydrocarbons or traces of oxygen and water leading to the

I. N. Filimonov; A. V. Smirnov; S. N. Nesterenko; I. I. Ivanova; L. B. Galperin; R. H. Jensen

2006-01-01

63

Synchrotron radiation induced gas desorption from a Prototype Large Hadron Collider beam screen at cryogenic temperatures  

Microsoft Academic Search

The performance of the vacuum system of the Large Hadron Collider will depend critically on the synchrotron radiation induced gas desorption and on the readsorption of molecules on the cold surfaces. The present design of the system is based on a so-called beam screen inserted in the 1.9 K cold bore of the magnets. Gas molecules desorbed will therefore readsorb

R. Calder; O. Gröbner; A. G. Mathewson; V. V. Anashin; A. Dranichnikov; O. B. Malyshev

1996-01-01

64

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

PubMed

Under international treaty, the United States and Russia are disposing of their aging stockpile of chemical weapons. Incineration and chemical neutralization are options for sites in the United States, although Russia prefers the latter. The storage and disposal of bulk and chemical agents and weapons involve unique hazards of handling extremely toxic materials. There are three major areas of concern--the storage stockpile, the disposal area, and the discovery and destruction of "found" material not considered part of the stockpile. Methods have been developed to detect the presence of chemical agents in the air, and these are used to help assure worker protection and the safety of the local population. Exposure limits for all chemical agents are low, sometimes nanograms per cubic meter for worker control limits and picograms per cubic meter for general population limits. There are three types of monitoring used in the USA: alarm, confirmation, and historical. Alarm monitors are required to give relatively immediate real-time responses to agent leaks. They are simple to operate and rugged, and provide an alarm in near real-time (generally a few minutes). Alarm monitors for the demilitarization program are based on sorbent pre-concentration followed by thermal desorption and simple gas chromatography. Alarms may need to be confirmed by another method, such as sample tubes collocated with the alarm monitor and analyzed in a laboratory by more sophisticated chromatography. Sample tubes are also used for historical perimeter monitoring, with sample periods typically of 12 h. The most common detector is the flame photometric detector, in sulfur or phosphorous mode, although others, such as mass-selective detectors, also have been used. All agents have specific problems with collection, chromatography and detection. Monitoring is not made easier by interferences from pesticide spraying, busy roadways or military firing ranges. Exposure limits drive the requirements for analytical sensitivity. Lowering limits adds additional difficulties to the monitoring efforts. The various monitoring methods and the role they play in ensuring worker and general population safety are discussed. PMID:12400916

Harper, Martin

2002-10-01

65

Two-directional N2 desorption in thermal dissociation of N2O on Rh(110), Ir(110), and Pd(110) at low temperatures  

NASA Astrophysics Data System (ADS)

Two-directional N2 desorption was found in N2O dissociation on Rh(110), Ir(110), and Pd(110) below 160 K by angle-resolved thermal desorption. N2)O(a is mostly dissociated during heating procedures, emitting N2)(g and leaving O(a). N2 showed four desorption peaks in the temperature range of 110-200 K. One of them commonly showed a cosine distribution, whereas the others sharply collimated off the surface normal in the plane along the 001 direction. The collimation angle was about 70deg on Rh(110), 65deg on Ir(110), and 43deg]-50[deg on Pd(110). A high-energy-atom assisted desorption model was proposed for N2 inclined emission. copyright 2002 American Vacuum Society.

Horino, H.; Rzeznicka, I.; Kokalj, A.; Kobal, I.; Ohno, Y.; Hiratsuka, A.; Matsushima, T.

2002-09-01

66

Temperature-jump investigation of alkyl chain length effects on sorption/desorption kinetics at reversed-phase chromatographic interfaces  

SciTech Connect

The influence of the alkyl chain length on the kinetics of solute retention at reversed-phase chromatographic surfaces is examined. A Joule-discharge temperature-jump relaxation experiment was used to monitor reversible sorption/desorption kinetics at C4- and C8-modified silica/solution interfaces. Biexponential sorption/desorption relaxation kinetics were observed for a charged fluorescent probe, 1-anilino-8-naphthalenesulfonate (ANS), on both C4- and C8-silica surfaces. Both relaxation rates on C4 surfaces were sufficiently slow to be measured and increased linearly with solute concentration. One of the relaxations on a C8 surface is too fast to be resolved from the heating rate, similar to behavior of the solute on a longer chain C18-silica. These observations suggest that sorption kinetics on the intermediate chain length surface, C4-silica, are different from kinetics on longer chain length surfaces, C8- and C18-silica. From a fit of the data to a two-step kinetic model, the rates of both adsorption and partition of the ionic probe on the C4 chain are estimated; both rates exhibit significant influence over the equilibrium constant. The relaxation rate of a neutral probe, N-phenyl-1-napthylamine, is also measured; the results indicate a fast (diffusion-controlled) adsorption step, followed by a detectable barrier to partition that is similar to the partition barrier for ANS on the C4-silica surface. 33 refs., 6 figs., 7 tabs.

Ren, F.Y.; Harris, J.M. [Univ. of Utah, Salt Lake City, UT (United States)

1996-05-01

67

Effects of preadsorbed oxygen on the bonding and desorption kinetics of CO on Ni(110)  

SciTech Connect

The effects of oxygen preadsorption on CO adsorption and CO desorption kinetics have been studied by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). It is found that preadsorbed oxygen decreased total CO uptake at 120 K by no more than 20% even though the adsorption and desorption energies are strongly affected. The presence of oxygen causes several new desorption states to appear in the TPD whose populations depend sensitively upon oxygen predose. Using published results for the structure of oxygen covered Ni(110) and the present HREELS measurements, the desorption states have been assigned to structurally distinct bonding sites. Using the variation in heating rates method, the first order desorption energies and preexponential factors are obtained as a function of CO coverage for various oxygen predoses. The relationship between the desorption energies and the bonding sites, especially with regard to the distance of CO from neighboring oxygen atoms, is discussed.

Feigerle, C.S. (Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600 (USA)); Overbury, S.H.; Huntley, D.R. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201 (USA))

1991-05-01

68

Decrease of water vapor desorption by Si film coating on stainless steel  

Microsoft Academic Search

Surface modification of stainless steel by Si coating was attempted to reduce water desorption in an evacuation process. Outgassing properties of stainless steel plates with and without Si coating including dependence on deposition condition were compared by temperature programmed desorption and throughput method. The outgassing rate of a Si coated sample at optimized condition was reduced to about 1\\/10 of

S. S. Inayoshi; S. Tsukahara; A. Kinbara

1999-01-01

69

Manipulation of polyatomic molecules with the scanning tunnelling microscope at room temperature: chlorobenzene adsorption and desorption from Si(111)-(7 × 7)  

Microsoft Academic Search

We report the imaging of chlorobenzene molecules chemisorbed on the Si(111)-(7 × 7) surface at room temperature with the scanning tunnelling microscope, and the desorption of the molecules by the tunnelling current. Detailed voltage-dependent imaging (at positive bias) allows the elucidation of the number and orientation of all the adsorbate configurations in the 7 × 7 unit cell. At negative

P A Sloan; R E Palmer

2006-01-01

70

Electronic desorption from low temperature ices and analogs of outer solar system surfaces  

Microsoft Academic Search

Low energy electron induced radiolysis of ices and surrogates of outer solar system bodies such as icy moons and comets have been investigated. Low energy electrons are effective simulants of high energy charged particle irradiation. Molecular hydrogen emission from comets is used to gain information about the formation temperature and isotopic branching in these primordial solar system objects. Long term

G. A. Grieves; T. M. Orlando

2009-01-01

71

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

Microsoft Academic Search

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

S Lahsasni; M Kouhila; M Mahrouz; M Fliyou

2003-01-01

72

Energetics of high temperature dimer desorption and reconstruction at the end of small zigzag carbon nanotubes  

Microsoft Academic Search

The energetics of small zigzag carbon nanotubes at high temperature regime (T=2500 K) is investigated via k-space tight-binding molecular dynamics (TBMD) simulations. It is found that the n dangling atoms at the end of a zigzag tube with 5

R. Che; L.-M Peng; S Zhang; Z Sun

2003-01-01

73

Downscaling daily extreme temperatures with genetic programming  

Microsoft Academic Search

A context-free genetic programming (GP) method is presented that simulated local scale daily extreme (maximum and minimum) temperatures based on large scale atmospheric variables. The method evolves simple and optimal models for downscaling daily temperature at a station. The advantage of the context-free GP method is that both the variables and constants of the candidate models are optimized and consequently

Paulin Coulibaly

2004-01-01

74

Temperature programmed decomposition of uranyl nitrate hexahydrate  

Microsoft Academic Search

Temperature programmed decomposition (TPD) of uranyl nitrate hexahydrate has been studied using evolved gas analysis mass spectrometry (EGA-MS) in the temperature range 300–1400 K. Thermogravimetric (TGA) investigations were performed in the temperature range 300–1100 K. An attempt has been made to resolve the complexity of decomposition behaviour through suitable comparison of TGA and EGA-MS data. Kinetic control regimes for various

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

1999-01-01

75

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

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. PMID:18973943

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

2008-10-29

76

Low-Cost Programmed Oven Temperature Controller.  

ERIC Educational Resources Information Center

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)

Clubine, Gerald D.

1982-01-01

77

Sorption/desorption behavior of iodine on graphite. [HTGR  

SciTech Connect

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

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

1982-11-01

78

Atomic alkali-metal gas cells at liquid-helium temperatures: Loading by light-induced atom desorption  

Microsoft Academic Search

We have studied the loading of gaseous alkali-metal atoms into glass cells held at about 2 K by light-induced atom desorption (LIAD). In LIAD loading, the cell containing dense helium gas and a small amount of alkali metal is irradiated with cw laser light. This technique has two unique features to be investigated: alkali-metal atoms are desorbed, even by weak

A. Hatakeyama; K. Enomoto; N. Sugimoto; T. Yabuzaki

2002-01-01

79

Temperature dependence of adsorption coefficients of 222Rn on activated charcoal determined by adsorption-desorption method.  

PubMed

Adsorption coefficients of 222Rn on five activated charcoal were determined (at -21, +7 and +26 degrees C) by an adsorption-desorption technique using a radon source and an Erlenmeyer flask. They varied from 1.1 to 41.2 L x g(-1). From this variation the mean heat of adsorption of radon on our charcoal was calculated as equal to 4,630(50) cal/mole. PMID:11197467

Zikovsky, L

2001-02-01

80

Desorption of chlorine organic solvents  

SciTech Connect

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

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

1982-03-01

81

Thermal desorption of C6H6 from surfaces of astrophysical relevance.  

PubMed

The thermal desorption of C(6)H(6) from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO(2) substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C(6)H(6) on grains surrounded by H(2)O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C(6)H(6) from the amorphous SiO(2) substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C(6)H(6) on the H(2)O surface. The astrophysical implications of these observations are briefly outlined. PMID:20059103

Thrower, J D; Collings, M P; Rutten, F J M; McCoustra, M R S

2009-12-28

82

Thermal desorption of C6H6 from surfaces of astrophysical relevance  

NASA Astrophysics Data System (ADS)

The thermal desorption of C6H6 from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO2 substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C6H6 on grains surrounded by H2O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C6H6 from the amorphous SiO2 substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C6H6 on the H2O surface. The astrophysical implications of these observations are briefly outlined.

Thrower, J. D.; Collings, M. P.; Rutten, F. J. M.; McCoustra, M. R. S.

2009-12-01

83

Geometric Structure and Desorption Kinetics of CO on Cr2O3(0001)/Cr(110)  

NASA Astrophysics Data System (ADS)

The Cr(110) surface is unique in that its native oxide grows epitaxially. Since understanding the adsorption and desorption kinetics of simple molecules on transition metal oxides is important for understanding catalytic phenomena, we have studied the adsorption geometry and desorption kinetics of CO on the epitaxial Cr2O3(0001) surface. The adsorption of CO was performed at 120 K and produced a weak (3 x 3) R 30^o reconstruction, as monitored by low energy electron diffraction (LEED). To determine the activation energy and desorption kinetics, temperature programmed desorption (TPD) measurements have been performed at heating rates of 5, 10, 25, and 50 ^oC/min. The results of the TPD measurements indicate that the desorption is approximately 1^st order and has an activation energy of 0.52 eV/molecule (50 kJ/mol).

Arellano, Gabriel; Redding, Sy; Walters, Jennifer; Clark, Nicholas; Rieman, Simona; Geisler, Heike; Ventrice, Carl

2009-10-01

84

A New Cold-Bore Experiment for Heavy-Ion Induced Molecular Desorption Studies at Low Temperatures: First Results obtained at 300 K, 77 K, and 15 K  

SciTech Connect

A dedicated cold-bore ion desorption experiment was performed in August 2004 at CERN's Heavy Ion Accelerator LINAC 3. The dynamic outgassing of 4.2 MeV/u Pb53+ ions, impacting under 89.2 deg. grazing incidence onto a copper tube, was studied as a function of the target temperature. Partial pressure rises of H2, CH4, CO, CO2, H2O, and O2 were measured at 300 K, 77 K, and 15 K using continuous lead ion bombardment. The new experimental setup is described and first pressure rise measurements are presented.

Mahner, E. [CERN, Geneva (Switzerland); Bender, M.; Kollmus, H. [GSI, Darmstadt (Germany)

2005-06-08

85

Concurrent separation of CO2 and H2O from air by a temperature-vacuum swing adsorption/desorption cycle.  

PubMed

A temperature-vacuum swing (TVS) cyclic process is applied to an amine-functionalized nanofibrilated cellulose sorbent to concurrently extract CO(2) and water vapor from ambient air. The promoting effect of the relative humidity on the CO(2) capture capacity and on the amount of coadsorbed water is quantified. The measured specific CO(2) capacities range from 0.32 to 0.65 mmol/g, and the corresponding specific H(2)O capacities range from 0.87 to 4.76 mmol/g for adsorption temperatures varying between 10 and 30 °C and relative humidities varying between 20 and 80%. Desorption of CO(2) is achieved at 95 °C and 50 mbar(abs) without dilution by a purge gas, yielding a purity exceeding 94.4%. Sorbent stability and a closed mass balance for both H(2)O and CO(2) are demonstrated for ten consecutive adsorption-desorption cycles. The specific energy requirements of the TVS process based on the measured H(2)O and CO(2) capacities are estimated to be 12.5 kJ/mol(CO2) of mechanical (pumping) work and between 493 and 640 kJ/mol(CO2) of heat at below 100 °C, depending on the air relative humidity. For a targeted CO(2) capacity of 2 mmol/g, the heat requirement would be reduced to between 272 and 530 kJ/mol(CO2), depending strongly on the amount of coadsorbed water. PMID:22823525

Wurzbacher, Jan Andre; Gebald, Christoph; Piatkowski, Nicolas; Steinfeld, Aldo

2012-08-06

86

Chemical Thermal Desorption System.  

National Technical Information Service (NTIS)

A field portable chemical thermal desorption system. The system comprises a desorption tube, an injection needle operatively connected to the desorption tube, a needle valve operatively connected to the injection needle, a heater operatively connected to ...

A. Alcaraz C. Koester J. D. Eckels

2004-01-01

87

Kinetics of hydrogen adsorption and desorption on Si(100) surfaces  

NASA Astrophysics Data System (ADS)

The kinetics of molecular hydrogen reactions at the Si (100) surface has been studied by simulation to extract the physics underlying two unexpected experimental observations: apparently first-order desorption kinetics and an increase in sticking probability with hydrogen coverage. At a partially H-terminated Si(100) surface, each Si dimer assumes an unoccupied dimer (UOD), singly occupied dimer (SOD), or doubly occupied dimer (DOD) structure. In our hydrogen reaction model based on an inter-dimer mechanism, a site consisting of an adjacent pair of a DOD and a UOD (DOD/UOD) is a key component for the desorption and adsorption kinetics of hydrogen at the Si(100) surface. To simulate reaction kinetics of both reactions, DU (D: DOD, U: UOD) and SS (S: SOD) pathways are proposed: DU pathway claims that the adsorption as well as desorption of hydrogen takes place at common sites having a cis-configured SOD/SOD pair that is transformed transiently from a DOD/UOD pair by H(D) diffusion. Thus the adsorption obeys the so-called 4H mechanism, but the desorption obeys the 2H mechanism. SS pathway claims that the adsorption occurs at sites having a UOD/UOD pair, and the desorption occurs at sites having a cis-configured SOD/SOD pair that is generated by diffusion of isolated SODs. To simulate temperature-programmed-desorption spectra and sticking probability vs coverage curves, thermo-statistics for a lattice-gas system characterized with parameters for hydrogen pairing and dimer clustering is used to evaluate equilibrium populations of DOD/UOD pairs and isolated SODs. The model simulation based on the above reaction model successfully reproduces all of the complicated, coverage dependent adsorption and desorption reactions of hydrogen at Si(100) surfaces. Specifically, at high coverage above 0.1 ML majority of the adsorption and desorption proceed along the DU pathway. Hence, it is suggested that the adsorption and desorption in the high coverage regime are not microscopically reversible. On the other hand, at low coverages below 0.1 ML, the simulation shows up that the majority of adsorption proceeds along the SS pathway, and the desorption by the DU pathway. Since both reactions obey the 2H mechanism, it is suggested that the desorption and adsorption in the low coverage regime are microscopically reversible.

Narita, Yuzuru; Inanaga, Shoji; Namiki, Akira

2013-06-01

88

Enhancement of the electron-stimulated desorption from amorphous aluminum oxide films on silicon during an increase in the substrate temperature  

NASA Astrophysics Data System (ADS)

The effect of high-temperature electron-stimulated desorption (ESD) from 20-nm-thick Al2O3 films deposited onto silicon wafers is studied. The ESD effect is found to be significantly enhanced upon heating. The films are found to decompose during ion beam irradiation of a heated substrate resulting in pure Al appearance. This process is accompanied by the formation of islands and almost pure silicon surface regions at a certain critical irradiation dose. Outside the irradiation zone, a 20-nm-thick Al2O3 film remains continuous even upon heating to 700°C and holding for 90 min. The effect of the primary electron beam energy on ESD from a 20-nm-thick Al2O3 film on silicon is investigated, and the parameters at which ESD takes place or absent are determined.

Ivanchenko, M. V.; Gritsenko, V. A.; Nepomnyashchii, A. V.; Saranin, A. A.

2012-05-01

89

The release of trapped gases from amorphous solid water films. II. ``Bottom-up'' induced desorption pathways  

NASA Astrophysics Data System (ADS)

In this (Paper II) and the preceding companion paper (Paper I; R. May, R. Smith, and B. Kay, J. Chem. Phys. 138, 104501 (2013)), we investigate the mechanisms for the release of trapped gases from underneath amorphous solid water (ASW) films. In Paper I, we focused on the low coverage regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime, the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that these abrupt desorption bursts are due to pressure induced structural failure of the ASW overlayer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores formed during ASW deposition. The extent of desorption and the line shape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of ASW is used to vary the porosity of the overlayer and strongly supports the hypothesis that the low temperature desorption pathway is due to porosity that is templated into the ASW overlayer by the underlayer during deposition.

Alan May, R.; Scott Smith, R.; Kay, Bruce D.

2013-03-01

90

Effects of loading different metal ions on an activated carbon on the desorption activation energy of dichloromethane\\/trichloromethane  

Microsoft Academic Search

The effects of loading Fe3+, Mg2+, Cu2+ or Ag+ on activated carbons (ACs) on interaction of the carbon surfaces with dichloromethane (DCM) and trichloromethane (TCM) were investigated. Temperature-programmed desorption (TPD) experiments were conducted to measure the desorption activation energy of DCM\\/TCM on the ACs separately doped with ions Fe3+, Mg2+, Cu2+ and Ag+. The absolute hardness and electronegativity of DCM

Qibin Xia; Zhong Li; Limin Xiao; Zhijuan Zhang; Hongxia Xi

2010-01-01

91

The NASA high temperature superconductivity program  

NASA Astrophysics Data System (ADS)

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.

Sokoloski, Martin M.; Romanofsky, Robert R.

1990-04-01

92

ENGINEERING BULLETIN: THERMAL DESORPTION TREATMENT  

EPA Science Inventory

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

93

ENGINEERING BULLETIN: THERMAL DESORPTION TREATMENT.  

EPA Science Inventory

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

94

Analytical mass spectrometry of artists’ acrylic emulsion paints by direct temperature resolved mass spectrometry and laser desorption ionisation mass spectrometry  

Microsoft Academic Search

Direct temperature resolved mass spectrometry (MS) is a microanalytical technique to analyse modern paints by thermal separation and ionisation of organic pigments and polymeric fractions from a platinum\\/rhodium filament inside the ionisation chamber of the mass spectrometer. Most organic pigments in modern paints are desorbed at lower temperatures. Ethyl acrylate\\/methylmethacrylate or butyl acrylate\\/methylmethacrylate copolymers used in acrylic emulsion paints produce

Jaap J Boon; Tom Learner

2002-01-01

95

A comparative study of high-temperature water formation and OH desorption on polycrystalline palladium and platinum catalysts  

Microsoft Academic Search

The water formation reaction has been studied on a hot polycrystalline palladium catalyst and a theoretical model has been derived with Chemkin in order to fit the experimental data. The results were compared with similar studies for platinum. The H2\\/O2 reaction was measured with LIF and microcalorimetry on palladium at a temperature of 1300 K, pressures of 13 and 26

Å Johansson; M Försth; A Rosén

2003-01-01

96

Delay Cartridge with Temperature Programmed Flash Chamber.  

National Technical Information Service (NTIS)

An improved pyrotechnic delay system is given wherein temperature compensation means are utilized to minimize or eliminate ambient temperature affects upon the burning rate and variability of the delay. Apparatus and method are provided to increase the ac...

M. L. Greene F. J. Valenta

1981-01-01

97

Accelerated Molecular Dynamics Simulation of Thermal Desorption  

NASA Astrophysics Data System (ADS)

Thermal desorption has been the focus of much surface science research recently. Alkane desorption experiments on graphite [1] show a prefactor that is constant with chain length, while experiments on magnesium oxide [2] show a prefactor that increases with chain length. We utilize an all-atom model to study alkane desorption from graphite. Transition state theory is used to obtain rate constants from the simulation. Accelerated molecular dynamics techniques are used to extend the simulations to experimentally relevant temperatures. Our results provide an explanation [3] for this seemingly contradictory functionality of the prefactor. We also examine the effect that film structure has on the rate of desorption and the shape of the desorption profile through varying coverage. [1] K.R. Paserba and A.J. Gellman, J. Chem. Phys. 115, 6737 (2001). [2] S.L. Tait et al., J. Chem. Phys. 122, 164707 (2005). [3] K.E. Becker and K.A. Fichthorn, J. Chem. Phys. 125, 184706 (2006).

Becker, Kelly; Fichthorn, Kristen

2007-03-01

98

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

SciTech Connect

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.

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

2011-12-31

99

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

SciTech Connect

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.

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

2010-12-21

100

Thermal Desorption of Galliumchloride Adsorbed on GaAs (100)  

NASA Astrophysics Data System (ADS)

Adsorption and desorption of galliumchloride (GaCl) on GaAs surfaces are investigated to understand the self-limiting process in the chloride atomic layer epitaxy (ALE). Adsorption energy of GaCl on GaAs (100) surfaces is determined by temperature programmed desorption (TPD). As stabilized 2× 4 surfaces and Ga stabilized 4× 6 reconstructed surfaces are exposed to a GaCl molecular beam which is produced by a newly designed GaCl cell. GaCl desorption is observed on both 2× 4 and 4× 6 surfaces, while the desorption of GaClx (x=2, 3), AsClx (x=1˜ 3) and Cl2 are not detected. The adsorption energy of GaCl, Ead, is calculated to be 38 kcal/mol for the 2× 4 surface and 32 kcal/mol for the 4× 6 surface. The adsorbed species in chloride ALE process is also discussed with reference to the surface residence time of GaCl.

Sasaoka, Chiaki; Kato, Yoshitake; Usui, Akira

1991-10-01

101

Finite-Temperature Dihydrogen Adsorption/Desorption Thermodynamics on Metallo-Porphyrin Incorporated Graphene: Enthalpy versus Vibration  

NASA Astrophysics Data System (ADS)

Gas adsorption is closely related to a variety of important physicochemical processes and technologies. Especially, hydrogen storage has been attracting much interest due to high energy density and the environmetally-friendly nature. Although a lot of theoretical studies have been carried out, the thermal vibration effect on hydrogen-sorbent interaction is relatively laking. Here we report the thermodynamics of H2 molecules adsorbed onto metallo-porphyrin-incoporated graphenes based on first-principles density-functional theory calculations. We found that the slow vibrations induced by weak binding tend to make the system more stable under finite temperature while the fast vibrations induced by strong binding disturb the adsorption. This tendency is expected to be universally found in various gas-sorbent systems.

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

2013-03-01

102

Hydrogen adsorption and desorption at the Pt(110)-(1×2) surface: experimental and theoretical study.  

PubMed

The interaction of hydrogen with the Pt(110)-(1×2) surface is studied using temperature programmed desorption (TPD) measurements and density functional theory (DFT) calculations. The ridges in this surface resemble edges between micro-facets of Pt nano-particle catalysts used for hydrogen evolution (HER) and hydrogen oxidation reactions (HOR). The binding energy and activation energy for desorption are found to depend strongly on hydrogen coverage. At low coverage, the strongest binding sites are found to be the low coordination bridge sites at the edge and this is shown to agree well with the He-atom interaction and work function change which have been reported previously. At higher hydrogen coverage, the higher coordination sites on the micro-facet and in the trough get populated. The simulated TPD spectra based on the DFT results are in close agreement with our experimental spectra and provide microscopic interpretation of the three measured peaks. The lowest temperature peak obtained from the surface with highest hydrogen coverage does not correspond to desorption directly from the weakest binding sites, the trough sites, but is due to desorption from the ridge sites, followed by subsequent, thermally activated rearrangement of the H-adatoms. The reason is low catalytic activity of the Pt-atoms at the trough sites and large reduction in the binding energy at the ridge sites at high coverage. The intermediate temperature peak corresponds to desorption from the micro-facet. The highest temperature peak again corresponds to desorption from the ridge sites, giving rise to a re-entrant mechanism for the thermal desorption. PMID:23518690

Gudmundsdóttir, Sigrídur; Skúlason, Egill; Weststrate, Kees-Jan; Juurlink, Ludo; Jónsson, Hannes

2013-05-01

103

n-alkanes on Pt(111) and on C(0001)/Pt(111): Chain Length Dependence of Kinetic Desorption Parameters  

SciTech Connect

We have measured the desorption of seven small n-alkanes (CNH2N+2, N = 1-4, 6, 8, 10) from the Pt(111) and C(0001) surfaces by temperature programmed desorption. We compare these results to our recent study of the desorption kinetics of these molecules on MgO(100) [J. Chem. Phys. 122, 164708 (2005)]. There we showed an increase in the desorption pre-exponential factor by several orders of magnitude with increasing n-alkane chain length and a linear desorption energy scaling with a small y-intercept value. We suggest that the significant increase in desorption prefactor with chain length is not particular to the MgO(100) surface, but is a general effect for desorption of the small n-alkanes. This argument is supported by statistical mechanical arguments for the increase in the entropy gain of the molecules upon desorption. In this work, we demonstrate that this hypothesis holds true on both a metal surface and a graphite surface. We observe an increase in prefactor by five orders of magnitude over the range of n-alkane chain lengths studied here. On each surface, the desorption energies of the n-alkanes are found to increase linearly with the molecule chain length and have a small y-intercept value. Prior results of other groups have yielded a linear desorption energy scaling with chain length that has unphysically large y-intercept values. We demonstrate that by allowing the prefactor to increase according to our model, a reanalysis of their data resolves this y-intercept problem to some degree.

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

2006-12-21

104

Diurnal Soil Temperature Effects within the GLOBE® Program Dataset  

Microsoft Academic Search

Long-term collection of soil temperature with depth is important when studying climate change. The international program GLOBE® 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, along with other physical data, were used to collect soil temperature to a depth of

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

2007-01-01

105

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

SciTech Connect

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.

Bartram, Michael E.; Creighton, J. Randall

1999-05-26

106

Monte Carlo evaluation of thermal desorption rates  

SciTech Connect

The recently reported method for computing thermal desorption rates via a Monte Carlo evaluation of the appropriate transition state theory expression (J. E. Adams and J. D. Doll, J. Chem. Phys. 74, 1467 (1980)) is extended, by the use of importance sampling, so as to generate the complete temperature dependence in a single calculation. We also describe a straightforward means of calculating the activation energy for the desorption process within the same Monte Carlo framework. The result obtained in this way represents, for the case of a simple desorptive event, an upper bound to the true value.

Adams, J.E.; Doll, J.D.

1981-05-01

107

NASA High Temperature Superconductivity Program. (Abstract Only).  

National Technical Information Service (NTIS)

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 cryogen...

M. M. Sokoloski R. R. Romanofsky

1990-01-01

108

Summary of Jimsonde Temperature Profiles. Part 2: Programs, Data Comments.  

National Technical Information Service (NTIS)

Natural environment criteria are established and interpreted for aeronautical vehicle design and engineering operations. Data summaries, computer formats, frequency distributions, and composite listings of the temperature profiles acquisition program are ...

J. A. Willett

1981-01-01

109

THERMAL DESORPTION TREATMENT  

EPA Science Inventory

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

110

Distinction between nonthermal plasma and thermal desorptions for NOx and CO2  

NASA Astrophysics Data System (ADS)

Nonthermal plasma (NTP) desorption is used in NOx aftertreatment systems for diesel engine exhaust gas. The authors conducted desorption experiments for both NTP and thermal desorptions under similar conditions and electric power levels. The results confirm that NO, NO2, and CO2 are desorbed by the NTP at lower gas temperatures, while the total amount of desorbed gas is nearly the same for both the processes. Moreover, the amount of NO2 for the NTP desorption is greater than that for the thermal desorption. The desorption of CO2 by the NTP is more significant and rapid than that by the thermal desorption.

Yoshida, Keiichiro; Okubo, Masaaki; Yamamoto, Toshiaki

2007-03-01

111

A high temperature test program for VRLA batteries  

Microsoft Academic Search

In early 1995, Johnson Controls Battery Group, Inc. (JCBGI) initiated a test program to evaluate the effects of several key design factors on valve regulated lead-acid (VRLA) battery performance in uncontrolled, unregulated, high temperature environments. The program included two separate components, accelerated laboratory and real time field testing. Phoenix, Arizona (USA) was selected as the field test location based on

S. D. Gerner; W. J. Ross; M. L. Sirard

1996-01-01

112

Mediterranean Sea-Surface Temperature Analysis Program MEDSST.  

National Technical Information Service (NTIS)

The MEDSST program performs a synoptic sea-surface temperature analysis for the Mediterranean and was developed specifically for operational use by the U.S. Navy Fleet Weather Central (FWC) in Rota, Spain. The sea-surface temperature (SST) observations (s...

S. E. Larson A. E. Anderson L. I'Anson

1973-01-01

113

Computer program to analyze multipass pressure-temperature-spinner surveys  

SciTech Connect

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

Spielman, Paul

1994-01-20

114

High-performance temperature-programmed microfabricated gas chromatography columns  

Microsoft Academic Search

This paper reports the first development of high-performance, silicon-glass micro-gas chromatography (?GC) columns having integrated heaters and temperature sensors for temperature programming, and integrated pressure sensors for flow control. These 3-m long, 150-?m wide and 250-?m deep columns, integrated on a 3.3 cm square die, were fabricated using a silicon-on-glass dissolved wafer process. Demonstrating the contributions to heat dissipation from

Masoud Agah; Joseph A. Potkay; Gordon Lambertus; Richard Sacks; Kensall D. Wise

2005-01-01

115

Molecular desorption of methyl halides from GaAs(110): The role of lateral dipole--dipole interaction between adsorbates  

SciTech Connect

Temperature programmed desorption (TPD) spectra of CH[sub 3]X (X=Cl, Br, I) from GaAs(110) were recorded with a heating rate of 5 K/s for coverages from less than 0.1 to 2 ML, where methyl halides desorb molecularly, i.e., without dissociation. The shapes of the TPD spectra are strongly coverage dependent with the peak temperature of desorption decreasing with increasing coverage, especially for the submonolayer region. A model incorporating dipole--dipole repulsive interactions between the adsorbed molecules and which was previously proposed for the desorption of adsorbed molecules from metal surfaces has been employed to fit our TPD spectra. The fit gives the activation energy, effective dipole moment, and effective polarizability for the adsorbate. The resulting dipole moment and polarizability are less than the gas-phase molecular values, suggesting the importance of an ordered adsorption orientation. [copyright] [ital 1994][ital American] [ital Institute] [ital of] [ital Physics].

Lu, P.; Lasky, P.J.; Yang, Q.; Wang, Y.; Osgood, R.M. Jr. (Columbia Radiation Laboratory, Columbia University, New York, New York 10027 (United States))

1994-12-01

116

Nitrogen adsorption and desorption at iron pyrite FeS2{100} surfaces.  

PubMed

We have investigated the interaction of nitrogen with single-crystal iron pyrite FeS(2){100} surfaces in ultra-high vacuum. N(2) adsorbs molecularly at low temperatures, desorbing at 130 K, but does not adsorb dissociatively even at pressures up to 1 bar. Atomic surface N can, however, be obtained with nitrogen ions and/or excited neutral species, generated by passing N(2) through an ion gun. Substantial nitrogen-induced disorder is seen with both ions and neutrals, and no ordered N overlayers form; a decrease in the S/Fe ratio is seen when exposing to nitrogen ions. Recombinative desorption leads to temperature-programmed desorption peaks at 410 and 520-560 K which we associate with interstitial atomic N and substitutional ionic N, respectively, in the surface regions. Thermal repair of sputter damage necessitates segregation of bulk S to the surface, which, over repeated experiments, leads to gross cumulative damage to the bulk crystal. The desorption temperatures associated with recombinative desorption of atomic N from FeS(2){100} are significantly lower than those measured for Fe surfaces. This is linked to the inability of FeS(2){100} to dissociate N(2), but suggests that N(ads) will be significantly more able to react with other species than it is on Fe surfaces. PMID:22801863

Liu, Tao; Temprano, Israel; Jenkins, Stephen J; King, David A; Driver, Stephen M

2012-07-17

117

THERMAL DESORPTION...NOW YOU'RE COOKIN'  

EPA Science Inventory

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

118

Desorption of Oxygen from Virgin CDS Single Crystals.  

National Technical Information Service (NTIS)

Typical desorption data of amu 16 from virgin CdS single crystals is presented for two classes of crystals as determined by their electrical properties. Thermal desorption energies are found in the energy range of 0.87 eV to > with temperatures of maximum...

K. W. Boer R. Schubert C. Wright

1968-01-01

119

COMPF: A Program for Calculating Post-Flashover Fire Temperatures.  

National Technical Information Service (NTIS)

COMPF is a computer program for calculating gas temperatures in a compartment during the post-flashover period of a fire. It is intended both for performing design calculations and for facilitating further research in endurance requirements for fire-resis...

V. Babrauskas

1975-01-01

120

Retention in multistep programmed-temperature gas chromatography and flow control Linear head pressure programs  

Microsoft Academic Search

A comparative study of retention in different systems of flow control that provide linear dependence with the temperature of the column's head pressure is performed by numerical simulation considering multistep (or multiramp) PTGC (programmed-temperature gas chromatography) as the most general situation. Calculation algorithms for each flow control mode are developed on the basis of a general retention equation and the

F. R. Gonzalez; A. M. Nardillo

1997-01-01

121

THERMAL DESORPTION OF PETROLEUM CONTAMINATED SOILS  

EPA Science Inventory

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

122

Modified adsorbate desorption energetics from platinum with sulfur pre-coverage  

NASA Astrophysics Data System (ADS)

At the forefront of heterogeneous catalysis and gas sensor research is the goal to tailor the chemisorptive properties of transition metal surfaces. Sulfur modifies platinum catalytic reaction product distributions which suggests that sulfur modifies the chemisorptive properties of platinum. The basic research reported in this dissertation improves the mechanistic understanding of sulfur modified chemisorption on platinum. Temperature programmed desorption has been used to study CO, H2, and O2 on clean polycrystalline platinum (Pt(Poly) and with sulfur pre-coverage (S/Pt(Poly)). Desorption from clean Pt(Poly) indicates that defects (500--600 K CO; 350--450 K H2; 200--275 K O2) and (111) sites (300--500 K CO; 200--350 K H2; 100--200 K, 600--1050 K O 2) generally comprise the surface. Both short range site blocking and long range electronic sulfur mechanisms are responsible for decreased chemisorption on S/Pt(Poly) surfaces. The 'saturation' sulfur coverage (via H2S decomposition) decreases the adsorption capacity of Pt(Poly) to 9.1% and 3.45% of maximum for CO and H2 respectively. Site blocking preferentially decreases desorption from defects. With increasing sulfur coverage, site blocking is the primary cause of decreased H2 desorption temperatures from (111) sites. However, both mechanisms significantly decrease CO desorption temperatures from (111) sites. In contrast, O2 desorption temperatures from (111) sites are not decreased. For adsorbate coverages from dilute to saturation, desorption peak maxima for CO shift continuously and gradually to lower temperature by 165 K and for H2 discretely by 120 K. The strongly decreased H2 and O2 adsorption on S/Pt(Poly) surfaces have been attributed to long sulfur effects that reduce the capability of Pt(Poly) to cause bond dissociation. Sulfur blocks about 4.5 times more O2 and 2.5 times more hydrogen adsorption sites than CO adsorption sites. Oxygen reacts with sulfur with SO2 (390, 480, 590 K) as the only oxidation product. Sulfur modified chemisorptive properties of platinum/alumina thin films depend on the availability of adsorption sites on platinum crystallites and the degree of alumina hydroxylation. Results are contrasted using the mode of adsorption for each of the adsorbates on bare platinum. Findings are briefly discussed in terms of hard-soft Lewis acid-base concepts.

Thomas, Valarie Denise

123

Temperature-Programmed Reduction Studies of V-Ag Catalysts  

Microsoft Academic Search

In H2\\/N2atmosphere, the reduction behavior of V-Ag catalysts with V\\/Ag atomic ratios 1\\/0, 9\\/1, 3\\/1, 2.16\\/1, 1.5\\/1, 1\\/1, and 0\\/1 were studied by temperature-programmed reduction (TPR), X-ray diffraction (XRD), and ultraviolet diffuse reflectance spectra (UVDRS). The results showed that the reduction processes of Ag2V4O11, Ag2V4O10.84, and Ag1.2V3O8are all the same while the reduction temperature was raised; they were first reduced

Xin Ge; Hui-liang Zhang

1998-01-01

124

Collector Material Desorption Tests.  

National Technical Information Service (NTIS)

To obtain long cathode lifetimes, the surface of the spent beam collector for the photocathode rf power source (called the Lasertron) must have a low coefficient of desorption of gas molecules by electrons. We assembled a low voltage (less than or equal t...

J. J. Welch C. K. Sinclair

1986-01-01

125

The effect of surface chemical functional groups on the adsorption and desorption of a polar molecule, acetone, from a model carbonaceous surface, graphite  

Microsoft Academic Search

The role of surface chemical heterogeneity in adsorption on a model carbonaceous surface (highly oriented pyrolitic graphite, HOPG) was investigated by temperature programmed desorption of acetone, a representative polar volatile organic compound. It was observed that oxygen-containing functional groups exist on air cleaved HOPG. The presence of surface functional groups reduces the binding energy, while increasing the uptake kinetics at

S. Kwon; R. Vidic; E. Borguet

2003-01-01

126

Trace level determination of enantiomeric monoterpenes in terrestrial plant emission and in the atmosphere using a ?-cyclodextrin capillary column coupled with thermal desorption and mass spectrometry  

Microsoft Academic Search

For the first time, enrichment on solid sorbents followed by thermal desorption has been used for the determination of the enantiomeric signature of monoterpenes in the gaseous emission of terrestrial plants. A ?-cyclodextrin capillary column has been used for the separation of critical pairs. The temperature program and column loading were optimized for making the accurate quantification of individual enantiomers

Noureddine Yassaa; Enzo Brancaleoni; Massimiliano Frattoni; Paolo Ciccioli

2001-01-01

127

Trace level determination of enantiomeric monoterpenes in terrestrial plant emission and in the atmosphere using a b-cyclodextrin capillary column coupled with thermal desorption  

Microsoft Academic Search

For the first time, enrichment on solid sorbents followed by thermal desorption has been used for the determination of the enantiomeric signature of monoterpenes in the gaseous emission of terrestrial plants. A b-cyclodextrin capillary column has been used for the separation of critical pairs. The temperature program and column loading were optimized for making the accurate quantification of individual enantiomers

Noureddine Yassaa; Enzo Brancaleoni; Massimiliano Frattoni; Paolo Ciccioli

128

Characteristics of oxygen consumption of coal at programmed temperatures  

Microsoft Academic Search

Oxygen consumption is an important index of coal oxidation. In order to explore the coal-oxygen reaction, we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently ranked coals at programmed temperatures. The size of coal samples ranged from 0.18?0.42 mm and the system heat-rate was 0.8°C\\/min. The results show that, for high ranked coals, oxygen

Xuyao QI; Deming WANG; Xiaoxing ZHONG; Junjie GU; Tao XU

2010-01-01

129

Desorption of chlorine organic solvents  

Microsoft Academic Search

Adsorption methods are being used more and more widely to treat gaseous discharges containing chlorohydrocarbons. However, recovery of the chlorohydrocarbons has not been studied sufficiently, and the desorption of the solvents with steam is particularly understudied. We investigated desorption of a number of solvents from industrial active carbon AR-3. Desorption was done with live steam in the 105 to 150°C.

N. I. Petrova; K. M. Nikolaev

1982-01-01

130

Accelerated molecular dynamics simulation of the thermal desorption of n-alkanes from the basal plane of graphite  

NASA Astrophysics Data System (ADS)

We utilize accelerated molecular dynamics to simulate alkane desorption from the basal plane of graphite. Eight different molecules, ranging from n-pentane to n-hexadecane, are studied in the low coverage limit. Acceleration of the molecular dynamics simulations is achieved using two different methods: temperature acceleration and a compensating potential scheme. We find that the activation energy for desorption increases with increasing chain length. The desorption prefactor increases with chain length for molecules ranging from pentane to decane. This increase subsides and the value of the preexponential factor fluctuates about an apparently constant value for decane, dodecane, tetradecane, and hexadecane. These trends are consistent with data obtained in experimental temperature-programed desorption (TPD) studies. We explain the dependence of the preexponential factor on alkane chain length by examining conformational changes within the alkane molecules. For the shorter molecules, torsional motion is not activated over experimental temperature ranges. These molecules can be treated as rigid rods and their partial loss in translational and rotational entropies upon adsorption increases as chain length increases, leading to an increasing preexponential factor. At their typical TPD peak temperatures, torsions are activated in the longer adsorbed chain molecules to a significant extent which increases with increasing chain length, increasing the entropy of the adsorbed molecule. This increase counteracts the decrease in entropy due to a loss of translation and rotation, leading to a virtually constant prefactor.

Becker, Kelly E.; Fichthorn, Kristen A.

2006-11-01

131

The first layer of water on Rh(111): Microscopic structure and desorption kinetics  

SciTech Connect

The adsorption states and growth process of the first water (D{sub 2}O) layer on Rh(111) were investigated using infrared reflection absorption spectroscopy, temperature programed desorption, and spot-profile-analysis low energy electron diffraction. Water molecules wet the Rh(111) surface intact. At the early stage of first layer growth, a ({radical}3x{radical}3)R30 deg. commensurate water layer grows where 'up' and 'down' species coexist; the up and down species represent water molecules which have free OD, pointing to a vacuum and the substrate, respectively. The up domain was a flatter structure than an icelike bilayer. Water desorption from Rh(111) was a half-order process. The activation energy and the preexponential factor of desorption are estimated to be 60 kJ/mol and 4.8x10{sup 16} ML{sup 1/}2/s at submonolayer coverage, respectively. With an increase in water coverage, the flat up domain becomes a zigzag layer, like an ice bilayer. At the saturation coverage, the amount of down species is 1.3 times larger than that of the up species. In addition, the activation energy and the preexponential factor of desorption decrease to 51 kJ/mol and 1.3x10{sup 14} ML{sup 1/2}/s, respectively.

Beniya, Atsushi; Yamamoto, Susumu; Mukai, Kozo; Yamashita, Yoshiyuki; Yoshinobu, Jun [The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

2006-08-07

132

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

SciTech Connect

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.

Dinh, L.; Balooch, M.

1999-08-11

133

Solid-phase thermodynamic interpretation of ion desorption in matrix-assisted laser desorption/ionization.  

PubMed

This work demonstrates a quantitative interpretation of ion desorption in matrix-assisted laser desorption/ionization (MALDI). The theoretical modeling incorporates transition state theory for the desorption of surface ions, assuming chemical and thermal equilibrium in the solid state prior to desorption. It is distinct from conventional models that assume chemical equilibrium in the gas phase. This solid-state thermodynamic interpretation was used to examine the desorption of pure 2,4,6-trihydroxyacetophenone (THAP) and of angiotensin I mixed with THAP. It successfully described the changes in ion yield with the effective temperature under various laser fluence and initial temperature conditions. The analysis also revealed the key role played by ion concentration in the modeling to provide the best fit of the model to observations. On the other hand, divergence of the ion beam with laser fluence was examined using an imaging detection method, and the signal saturation normally seen at high fluence was appropriately reduced by ion focusing. Simplified but deceptive theoretical interpretations were obtained when the analysis was conducted without adequate calibration of the instrument bias. PMID:20936806

Lai, Yin-Hung; Wang, Chia-Chen; Lin, Sheng-Hsian; Lee, Yuan Tseh; Wang, Yi-Sheng

2010-11-01

134

Multiyear Program Plan for the High Temperature Materials Laboratory  

SciTech Connect

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.

Arvid E. Pasto

2000-03-17

135

Accelerated Molecular Dynamics Simulation of Alkane Desorption  

NASA Astrophysics Data System (ADS)

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

McLaughlin, Kelly; Fichthorn, Kristen

2006-03-01

136

Pathways for thermal phosphorus desorption from the silicon (001) surface  

NASA Astrophysics Data System (ADS)

We use density-functional theory and transition-state search methods to characterize the thermal desorption of P2 molecules from the phosphorus-doped silicon (001) surface. We compare two desorption pathways, one proceeding via an in-surface P-P homodimer, the other via an on-surface P-P addimer. While intuitive, the homodimer pathway has an overly large reaction barrier which is not consistent with experimental measurements in the literature. Instead, P2 desorption proceeds by the alternative addimer pathway which requires the presence of silicon adatoms. We present a simple chemical-potential model which explains the appearance of these adatoms at high temperatures.

Bennett, Jennifer M.; Warschkow, Oliver; Marks, Nigel A.; McKenzie, David R.

2010-12-01

137

Progress in BNL High-Temperature Hydrogen Combustion Research Program  

SciTech Connect

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

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

1992-12-31

138

Progress in BNL High-Temperature Hydrogen Combustion Research Program  

SciTech Connect

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

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

1992-01-01

139

Calcium lignosulfonate adsorption and desorption on Berea sandstone.  

PubMed

This paper describes adsorption and desorption studies carried out with calcium lignosulfonate (CLS) on Berea sandstone. Circulation experiments were performed to determine CLS adsorption isotherms and the effects of CLS concentration, temperature, salinity, brine hardness, and injection rate on adsorption density. Flow-through experiments were performed to assess the reversibility of CLS adsorption and the influence of postflush rate, brine concentration, brine hardness, brine pH, and temperature on the desorption process. Results indicate that CLS adsorption isotherms on Berea sandstone follow the Freundlich isotherm law. The results presented in this paper on the effects of CLS adsorption and desorption on Berea sandstone show that: (1) increasing CLS concentration and salinity increases CLS adsorption density; (2) increasing temperature will decrease adsorption density; (3) increasing injection rate of CLS solution will slightly decrease CLS adsorption density; (4) postflush rate and salinity of brine have a large impact on the CLS desorption process; (5) the adsorption and desorption process are not completely reversible; and (5) temperature and pH of the postflush brine have little effect on desorption. PMID:15380409

Grigg, Reid B; Bai, Baojun

2004-11-01

140

OTEC gas desorption studies  

NASA Astrophysics Data System (ADS)

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

Chen, F. C.; Golshani, A.

1982-02-01

141

Aspects of the elution order inversion by pressure changes in programmed-temperature gas chromatography  

Microsoft Academic Search

The phenomenon of elution order inversion in programmed-temperature gas chromatography, as a result of only changing the head pressure of the column while retaining the same temperature program, is known to be experimentally detectable. In this paper we analyze some theoretical aspects of this phenomenon. These aspects concern the dependence of the separation on the pressure program for a couple

F. R. Gonzalez; A. M. Nardillo

1997-01-01

142

Deconstructing Desorption Electrospray Ionization: Independent Optimization of Desorption and Ionization by Spray Desorption Collection  

NASA Astrophysics Data System (ADS)

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented.

Douglass, Kevin A.; Jain, Shashank; Brandt, William R.; Venter, Andre R.

2012-11-01

143

Deconstructing desorption electrospray ionization: independent optimization of desorption and ionization by spray desorption collection.  

PubMed

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented. PMID:22907171

Douglass, Kevin A; Jain, Shashank; Brandt, William R; Venter, Andre R

2012-08-21

144

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

SciTech Connect

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.

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

2011-04-05

145

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

USGS Publications Warehouse

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.

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

2002-01-01

146

Effect of surface nanostructure on temperature programmed reaction spectroscopy  

NASA Astrophysics Data System (ADS)

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

Rieger, Michael; Rogal, Jutta; Reuter, Karsten

2008-03-01

147

Treatment of Y-12 storm sewer sediments and DARA soils by thermal desorption  

SciTech Connect

The 1992 Oak Ridge Reservation Federal Facilities Compliance Agreement (FFCA) listed a number of mixed wastes, subject to land disposal restrictions (LDR), for which no treatment method had been identified, and required DOE to develop strategies for treatment and ultimate disposal of those wastes. This paper presents the results of a program to demonstrate that thermal desorption can remove both organics and mercury from two mixed wastes from the DOE Y-12 facility in Oak Ridge, Tennessee. The first waste, the Y-12 Storm Sewer Sediments (SSSs) was a sediment generated from upgrades to the plant storm sewer system. This material contained over 4 percent mercury, 2 percent uranium and 350 mg/kg polychlorinated biphenyls (PCBs). Leachable mercury exceeded toxicity characteristic leaching procedure (TCLP) and LDR criteria. The second waste, the Disposal Area Remedial Action (DARA) Soils, are contaminated with uranium, mercury and PCBs. This treatability study included bench-scale testing of a thermal desorption process. Results of the testing showed that, for the SSSs, total mercury could be reduced to 120 mg/kg by treatment at 600{degrees}C, which is at the high end of the temperature range for typical thermal desorption systems. Leachable TCLP mercury was less than 50 {mu}g/L and PCBs were below 2 mg/kg. Treatment of the DARA Soils at 450{degrees}C for 10 minutes resulted in residual PCBs of 0.6 to 3.0 mg/kg. This is too high (goal < 2mg/kg) and higher treatment temperatures are needed. The testing also provided information on the characteristics and quantities of residuals from the thermal desorption process.

Morris, M.I. [Oak Ridge National Lab., TN (United States); Shealy, S.E. [IT Corporation, Knoxville, TN (United States)

1995-12-31

148

Thermal Desorption from Si(111) Surfaces with Native Oxides Formed During Chemical Treatments  

Microsoft Academic Search

The thermal desorption process during thermal cleaning of Si(111) surfaces with native oxides formed by various chemical treatments is studied using TDS (thermal desorption spectroscopy) under UHV. The reaction product of the process is identified to be SiO. The surface cleanliness after the cleaning is virtually independent of the oxide formation method. However, the desorption temperature of SiO strongly depends

Yoshihiro Kobayashi; Yukinobu Shinoda; Kiyomasa Sugii

1990-01-01

149

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

SciTech Connect

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.

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

2011-01-01

150

HYDROGEN AND ITS DESORPTION IN RHIC.  

SciTech Connect

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.

HSEUH,H.C.

2002-11-11

151

Co – Ni \\/ Al 2 O 3 oxygen carrier for fluidized bed chemical-looping combustion: Desorption kinetics and metal–support interaction  

Microsoft Academic Search

This study was aimed at developing a suitable oxygen carrier for fluidized bed chemical-looping combustion (CLC) processes. To this end a Co promoted Co–Ni\\/Al2O3 carrier material was synthesized and evaluated. The reactivity of the solid carrier material was assessed by investigating the energetics and kinetics of metal–support interaction using temperature programmed H2 desorption technique. The estimated activation of energy of

M. M. Hossain; K. E. Sedor; H. I. de Lasa

2007-01-01

152

A spreadsheet program for steady-state temperature fields  

SciTech Connect

A spreadsheet macro program is developed in EXCEL using Visual Basic for Applications (VBA) to analyze two-dimensional heat transfer. A description of the physical system analyzed is given along with the model equations and numerical methods used. The macro program is described and results of the analysis presented.

Hutchens, G.J.

2000-06-01

153

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

SciTech Connect

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.

Abdul Abu; Steve Smith [King's College London, London (United Kingdom). Department of Biochemistry, School of Biomedical and Health Sciences

2006-09-01

154

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

Microsoft Academic Search

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

J. Villain

1991-01-01

155

High-Temperature Turbine Technology Program rotor water delivery and distribution tests  

Microsoft Academic Search

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 to 3000°F firing temperature) turbine for an Integrated Gasification Combined Cycle (IGCC) power plant using coal-derived fuels. This task of the HTTT Phase II program was to design, fabricate, and test a rotor water delivery and distribution system

1981-01-01

156

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

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.

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

2013-01-01

157

Advanced, Small High-Temperature Rise Combustor Program.  

National Technical Information Service (NTIS)

The report, submitted by the AiResearch Manufacturing Company of Arizona, is a semiannual progress report of an analytical and experimental study addressed to the problems associated with advanced, small, high-temperature-rise combustors. (Author)

S. C. Hunter

1971-01-01

158

High-temperature oxidation and corrosion of materials program  

SciTech Connect

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

Whittle, D.P.

1980-03-01

159

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

SciTech Connect

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).

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

1981-01-01

160

Thermal desorption study of selected austenitic stainless steels  

Microsoft Academic Search

Residual hydrogen in stainless steel results in a steady outgassing from vacuum chamber walls, hindering the achievement of ultrahigh vacuum conditions. The total content, the binding states, and the diffusivity of residual hydrogen in austenitic stainless steels, which together define the room temperature hydrogen outgassing rate, have been investigated by thermal desorption spectroscopy (TDS). Seven different steel types have been

J.-P. Bacher; C. Benvenuti; P. Chiggiato; M.-P. Reinert; S. Sgobba; A.-M. Brass

2003-01-01

161

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...

162

A Spreadsheet Program for Steady-State Temperature Distributions  

SciTech Connect

A desktop program is developed in Microsoft EXCEL using Visual Basic for Applications (VBA) to solve a two-dimensional steady state heat conduction problem with a radiation boundary condition. The resulting partial differential equation and boundary conditions are solved using finite difference techniques and the results are compared with a finite element solution using the commercially available software package MSC/THERMAL. The results from the two methods are found to be within 1 percent. The VBA solution demonstrates how spreadsheet programs, like EXCEL, can be used to solve practical engineering problems with good accuracy.

Hutchens, G.J.

2000-11-01

163

Method of enhancing selective isotope desorption from metals  

DOEpatents

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.

Knize, Randall J. (Plainsboro, NJ); Cecchi, Joseph L. (Lawrenceville, NJ)

1984-01-01

164

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

PubMed

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. PMID:17076515

Celer, Ewa B; Jaroniec, Mietek

2006-11-01

165

Sorption/desorption reversibility of phenanthrene in soils and carbonaceous materials  

SciTech Connect

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.

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

2007-02-15

166

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

PubMed

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 degrees C and was increased by reducing the temperature stepwise to 46, 20, and finally 4 degrees C. For desorption the temperature was increased stepwise again until 77 degrees 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 collapseto 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. PMID:17593717

Wang, Guohui; Kleineidam, Sybille; Grathwohl, Peter

2007-02-15

167

Knudsen layer formation in laser induced thermal desorption  

NASA Astrophysics Data System (ADS)

Laser induced thermal desorption of Xe atoms into vacuum from a metal surface following the nano-second pulsed laser heating was investigated by the time-of-flight (TOF) measurement. The desorption flow was studied at a wide range of desorption flux by varying the initially prepared Xe coverage ? (1 ML = 4.5 × 1018 atoms/m2). At ? = 0.3 ML, the TOF of Xe was well represented by a Maxwell-Boltzmann velocity distribution, which is in good agreement with thermal desorption followed by collision-free flow. At ? > 0.3 ML, the peak positions of the TOF spectra were shifted towards the smaller values and became constant at large ?, which were well fitted with a shifted Maxwell-Boltzmann velocity distribution with a temperature TD and a stream velocity u. With TD fixed at 165 K, u was found to increase from 80 to 125 m/s with increasing ? from 1.2 to 4 ML. At ? > 4 ML, the value of u becomes constant at 125 m/s. The converging feature of u was found to be consistent with analytical predictions and simulated results based on the Knudsen layer formation theory. We found that the Knudsen layer formation in laser desorption is completed at Knudsen number Kn <0.39.

Ikeda, Akihiko; Matsumoto, Masuaki; Ogura, Shohei; Okano, Tatsuo; Fukutani, Katsuyuki

2013-03-01

168

Desorption of hydrogen trapped in carbon and graphite  

NASA Astrophysics Data System (ADS)

Thermal desorption behavior of deuterium (D2) from isotropic graphites and a carbon fiber carbon composite (CFC) charged with D2 gas has been investigated to obtain information concerning hydrogen recycling and tritium inventory in fusion experimental devices as well as a futuristic fusion reactor. After thermal desorption experiments were conducted at temperatures up to 1740 K, a desorption peak at approximately 1600 K (peak 4) was discovered. This is in addition to the previously known peak at approximately 1300 K (peak 3). Peak 3 can be attributed to the release of deuterium controlled by the diffusion process in a graphite filler grain and peak 4 can be attributed to the detrapping of deuterium released from an interstitial cluster loop edge site. Activation energies of peaks 3 and 4 are estimated to be 3.48 and 6.93 eV, respectively.

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

2013-11-01

169

Helium/deuterium coimplanted silicon: A thermal desorption spectrometry investigation  

NASA Astrophysics Data System (ADS)

Thermal desorption spectrometry has been applied to investigate the blistering and exfoliation phenomena which occur at the surface of a p-type (100) silicon wafer coimplanted with helium and deuterium. During the heat treatments in linear temperature ramp, an explosive emission of both gases occurs. The phenomenon is kinetically controlled with an effective activation energy of 1.3+/-0.2 eV. In addition, the desorption spectra present a second contribution, attributed to deuterium emission from buried cavities. Also in this case, the process is kinetically controlled with an effective activation energy of 1.9+/-0.3 eV. Thermal desorption spectrometry is a suitable technique to have information about various phenomena which occur during blistering and exfoliation.

Corni, F.; Nobili, C.; Tonini, R.; Ottaviani, G.; Tonelli, M.

2001-05-01

170

Hydrogen retention in tungsten materials studied by Laser Induced Desorption  

NASA Astrophysics Data System (ADS)

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.

TEXTOR Team 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.

2013-07-01

171

Overview of Thermal Desorption Technology.  

National Technical Information Service (NTIS)

This report is a summary and extension of the presentation on thermal desorption that formed a part of the 'Remediation Innovative Technology Seminar' presented by NFESC earlier this year. The presentation was intended primarily to benefit U.S. Naval fiel...

R. J. Feeney P. J. Nicotri D. S. Janke

1998-01-01

172

Low-temperature resource assessment program. Final report  

SciTech Connect

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.

Lienau, P.J. [Oregon Inst. of Tech., Klamath Falls, OR (United States). Geo-Heat Center] [Oregon Inst. of Tech., Klamath Falls, OR (United States). Geo-Heat Center; Ross, H. [Utah Univ., Salt Lake City, UT (United States). Earth Sciences and Resources Inst.] [Utah Univ., Salt Lake City, UT (United States). Earth Sciences and Resources Inst.

1996-02-01

173

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

SciTech Connect

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.

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

1995-01-01

174

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

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.

Ferrizz, Robert Matthew

2007-08-01

175

Developments in ultra-fast temperature programming with silicon micromachined gas chromatography: performance and limitations.  

PubMed

Various commercially available ultra-fast temperature programming approaches were integrated to silicon micromachined GC (micro-GC) for performance improvement assessment. The combined technique of micro-GC and ultra-fast temperature programming up to a rate of 6°C/second yielded an extended analysis range to undecane (nC(11)), improved signal detectability by at least a factor of three for the solutes studied with respectable one day reproducibility of less than 1% relative standard deviation in retention time (n = 20). Through careful control of various variables affecting retention time, performance improvements can be extended further. The various effects temperature programming has on the stability of thermal conductivity detector as well as criteria that need to be met for the successful implementation of ultra-fast temperature programming in micro-GC are presented. PMID:22337801

Luong, Jim; Cai, Huamin; Gras, Ronda; Curvers, Jos

2012-03-01

176

Dynamic Gas Temperature Measurement System. Volume 2. Operation and Program Manual.  

National Technical Information Service (NTIS)

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 th...

P. T. Purpura

1983-01-01

177

High-Temperature-Turbine-Technology Program. Phase II. Technology Test and Support Studies. Final Report.  

National Technical Information Service (NTIS)

The Phase II program summarized in this report involved the development of the key high temperature turbine subsystem components toward a goal of technology readiness. Transpiration air-cooling (TAC) for the turbine blades and vanes was selected for this ...

1983-01-01

178

Grimethorpe high temperature\\/high-pressure gas filter experimental program  

Microsoft Academic Search

A reliable high-temperature, high-pressure, gas-cleanup system is a vital component of pressurized fluidized-bed combustion (PFBC) power generation. This report reviews and summarizes the development, construction, and testing of such a system, a filter module containing an array of 130 porous ceramic elements. The filter, designed to protect the gas turbine from erosion and to meet particulate emission standards, operates with

G. P. Reed; J. E. Oakey; N. J. Simms

1992-01-01

179

Reducing tile complexity for self-assembly through temperature programming  

Microsoft Academic Search

We consider the tile self-assembly model and how tile complexity can be eliminated by permitting the tem- perature of the self-assembly system to be adjusted throughout the assembly process. To do this, we pro- pose novel techniques for designing tile sets that permit an arbitrary length m binary number to be encoded into a sequence of O(m) temperature changes such

Ming-Yang Kao; Robert T. Schweller

2006-01-01

180

Studies of the Adsorption/Desorption Behavior of Explosive-Like Molecules.  

National Technical Information Service (NTIS)

This paper describes a general study of the adsorption/desorption behavior of explosive-like molecules as a function of temperature. Capillary column gas chromatography was used in conjunction with bare fused silica and borosilicate glass columns. Adsorpt...

B. T. Kenna F. J. Conrad

1989-01-01

181

Programming Enhancements for Low Temperature Thermal Decomposition Workstation  

SciTech Connect

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

Igou, R.E.

1998-10-01

182

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

ERIC Educational Resources Information Center

|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,…

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

2007-01-01

183

Desorption of Salicylic Acid from Modified Bentonite by Using Supercritical Fluids in Packed Bed Column  

Microsoft Academic Search

Desorption of salicylic acid from organically modified bentonite by using supercritical fluids (SCFs) was studied. The parameters, such as pressure, temperature, SCF flow rate, and cosolvent (entrainer) concentration, were investigated. A desorption yield of 40 wt% salicylic acid was obtained by using supercritical CO2 by operating at low pressure (300 bar), low temperature (40°C), and 2 mL CO2\\/min, it reached up to 77 wt%

Nuray Y?ld?z; Ayla Çal?ml?

2004-01-01

184

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

USGS Publications Warehouse

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

Czarnecki, J. B.

1983-01-01

185

Moisture desorption isotherms of medium-grain rough rice.  

PubMed

Moisture desorption isotherms (EMC/ERH) of medium-grain rough rice (Japonica variety) were determined using a constant environment chamber for various combinations of air temperature (11.8-51.0 degrees C) and relative humidity (37.1-89.7%). The initial moisture contents were in the range of 24.7-41.6% dry basis. A thin-layer technique was used to achieve uniform drying. Each test was continued until the moisture content change in 24h was less than 0.1% dry basis. The final moisture content was considered as the dynamic equilibrium moisture content. Four three-parameter EMC/ERH equations, the modified Henderson, modified Chung-Pfost, modified Oswin and modified Halsey equations, were compared for their ability to fit the experimental EMC/ERH data. The residual sum of squares (RSS) and standard error of estimate (SEE) were adopted as the criteria to evaluate the fitting performance of the models. The modified Chung-Pfost equation was identified as the most appropriate equation for representing the EMC/ERH desorption isotherms of rough rice. Coefficients for equilibrium moisture content as a function of equilibrium relative humidity and temperature are given. The EMC/ERH data obtained in this study agreed well with previously published data. However the average isotherm, combining desorption and adsorption data, of ASAE does not predict the desorption EMC of rough rice accurately. PMID:11172858

Basunia, M A.; Abe, T

2001-07-01

186

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

PubMed

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

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

2009-12-01

187

Desorption of pyrethroids from suspended solids.  

PubMed

Pyrethroid insecticides have been widely detected in sediments at concentrations that can cause toxicity to aquatic organisms. Desorption rates play an important role in determining the bioavailability of hydrophobic organic compounds, such as pyrethroids, because these compounds are more likely to be sorbed to solids in the environment, and times to reach sorptive equilibrium can be long. In the present study, sequential Tenax desorption experiments were performed with three sorbents, three aging times, and four pyrethroids. A biphasic rate model was fit to the desorption data with r(2) ?>?0.99, and the rapid and slow compartment desorption rate constants and compartment fractions are reported. Suspended solids from irrigation runoff water collected from a field that had been sprayed with permethrin 1 d before were used in the experiments to compare desorption rates for field-applied pyrethroids with those for laboratory-spiked materials. Suspended solids were used in desorption experiments because suspended solids can be a key source of hydrophobic compounds in surface waters. The rapid desorption rate parameters of field-applied permethrin were not statistically different from those of laboratory spiked permethrin, indicating that desorption of the spiked pyrethroids is comparable to desorption of the pyrethroids added and aged in the field. Sorbent characteristics had the greatest effect on desorption rate parameters; as organic carbon content of the solids increased, the rapid desorption fractions and rapid desorption rate constants both decreased. The desorption rate constant of the slow compartment for sediment containing permethrin aged for 28 d was significantly different compared to aging for 1 d and 7 d, whereas desorption in the rapid and slow compartments did not differ between these treatments. PMID:21538493

Fojut, Tessa L; Young, Thomas M

2011-05-23

188

Temperature-programmed methanation on Pd/La[sub 2]O[sub 3] and Pd/SiO[sub 2] catalysts  

SciTech Connect

Temperature-programmed reaction and desorption (TPR,TPD) spectra are compared for Pd/La[sub 2]O[sub 3] and Pd/SiO[sub 2] catalysts for CO methanation and CO and H[sub 2] coadsorption. A methoxy (CH[sub 3]O) species readily forms on the La[sub 2]O[sub 3] surface of Pd/La[sub 2]O[sub 3] by spillover, and this CH[sub 3]O hydrogenates to CH[sub 4] at a higher rate than CO adsorbed on Pd. Carbon also deposits on the catalyst surface during TPR, and then hydrogenates at a slower rate than CH[sub 3]O. In contrast, CH[sub 3]O does not form on Pd/SiO[sub 2] from CO and H[sub 2], and correspondingly Pd/SiO[sub 2] has a lower methanation activity than Pd/La[sub 2]O[sub 3]. Isotope labeling, interrupted reaction, activated adsorption, high-temperature TPD/TPR, and CH[sub 3]OH adsorption are used to study the surface processes on Pd/La[sub 2]O[sub 3]. The high methanation activity of Pd/La[sub 2]O[sub 3] catalysts during steady-state methanation may be related to the formation and hydrogenation of CH[sub 3]O. 28 refs., 12 figs., 1 tab.

Kester, K.B.; Chen, B.; Falconer, J.L. (Univ. of Colorado, Boulder, CO (United States))

1992-11-01

189

Synthesis of alcohols from carbon oxides and hydrogen. VIII. A temperature-programmed reaction study of n-butanal on a Zn-Cr-O catalyst  

SciTech Connect

The interaction of n-butanal with a Zn-Cr-O catalyst has been studied by temperature-programmed reaction. Using combined GC, GC-FTIR, and GC-MS techniques, a large number of desorption products have been identified, including 1-butanol, C/sub 8/ and C/sub 12/ aldehydes, C/sub 7/ and C/sub 8/ ketones, and C/sub 3/, C/sub 4/, and C/sub 7/ olefins, as well as CO/sub 2/, dienes, trienes, aromatics, and light hydrocarbons. The formation of most products is explained by assuming surface reactions of two classes of intermediate species originating from the adsorption of n-butanal and from the surface aldol-like condensation of two molecules of n-butanal. Results indicate that the Zn-Cr oxide catalyst is active in performing aldehyde condensation, hydrogenation, hydrolysis, dehydrogenation, decarboxylation, and dehydration, along with isomerization and cracking reactions. Different functionalities are associated with different temperature ranges. The detected chemical functionalities are discussed with respect to their relevance to the direct synthesis of methanol and higher alcohols from CO and H/sub 2/.

Lietti, L.; Botta, D.; Forzatti, P.; Mantica, E.; Tronconi, E.; Pasquon, I.

1988-06-01

190

The influence of step geometry on the desorption characteristics of O2, D2, and H2O from stepped Pt surfaces  

NASA Astrophysics Data System (ADS)

We have compared the desorption characteristics of O2, D2, and H2O from the Pt(533) surface to the Pt(553) surface using temperature programmed desorption. Both surfaces consist of four atom wide (111) terraces interrupted by monoatomic steps of the different step geometries: (100) versus (110), respectively. We find that desorption is influenced significantly by the presence of step sites and the geometry of those sites. In general, molecules and atoms are thought to be bound more strongly to step sites than to terrace sites. Our D2 desorption data from Pt(553) provide an anomalous counterexample to this common belief since D atoms on this surface appear to be bound stronger by terrace sites. We also show that it is not possible to say a priori which step geometry will bind atoms or molecules stronger: recombinatively desorbing O atoms are bound stronger to (100) sites, whereas H2O molecules are bound stronger to (110) sites. Furthermore, the amount of adatoms or molecules that are affected by the presence of steps varies for the different species, as is evident from the various step: terrace ratios of ~1:1.3 for O2 (O), ~1:3 for D2 (D), and ~1:1 for H2O. This indicates that, in contrast to deuterium, more oxygen atoms and water molecules are affected by the presence of steps than would be expected on geometrical arguments alone.

van der Niet, Maria J. T. C.; den Dunnen, Angela; Juurlink, Ludo B. F.; Koper, Marc T. M.

2010-05-01

191

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

SciTech Connect

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.

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

2010-01-01

192

Observation of Cd Adsorption on the Surface of Clay Minerals by Thermal Desorption Method  

NASA Astrophysics Data System (ADS)

Desorption of Cd adsorbed on Montmorillonite (Mt), Pyrophyllite (Py), Hydroalminum montmorillonite (HyA-Mt) is observed by means of QMS. The desorption peak temperatures of Cd are 730°C from Mt, 820°C from Py and beyond 900°C from HyA Mt, respectively. Cadmium absorbs on the side surface of the octahedral sheet for Mt and Py. However the desorption peak temperature of Cd from Py is higher than Mt because of the structure of Py, which is more thermaly stable than the structure of Mt. For HyA-Mt, Cd adsorbs mainly on the Al(OH)3 layer. Desorption peak temperature of Cd from Al(OH)3 layer is higher than that from the side surface of the crystal.

Oono, Kentarou; Takamatsu, Rieko; Takagi, Shoji; Gotoh, Tetsuji

193

Kinetic analysis of California oil shale by programmed temperature micropyrolysis  

SciTech Connect

Three oil shales from California were examined by micropyrolysis for evolution behavior and pyrolysis kinetic parameters to understand hydrocarbon evolution. The samples consisted of one from the Los Angeles basin, and two from the Monterey formation. The two Monterey shales were distinguished by low and high S contents of the kerogen. The measurements were performed by a Pyromat II micropyrolyzer operating at nominal constant heating rates of 1, 7, and 50 {degrees}C/min, between 250 and 700{degrees}C. The evolution profiles at 50{degrees}C/min heating rate of Los Angeles and the low S Monterey sample were similar, having the same temperature of maximum evolution (T{sub max}) (460{degrees}C) and similar peak widths ({delta}W{sub {1/2}} approximately 70{degrees}C). The high S Monterey shale was much different having a much lower T{sub max} (441{degrees}C) and a much broader profile ({delta}W{sub {1/2}} 119{degrees}C). The derived kinetic parameters of all three shales were different. The principal energy of activation from the discrete method (principal E{sub discrete}) and the energy of activation by the approximate method (E{sub approx}) were (in kcal/mol): 57 and 57 and 54; 52 and 50.6; 57 and 65.2; for Los Angeles, low S Monterey, and high S Monterey, respectively. These values agree with literature values for type II kerogens except for the high S Monterey sample, which appears to be anomalously high. 8 refs., 3 figs., 3 tabs.

Reynolds, J.G.; Burnham, A.K.

1991-12-09

194

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

Microsoft Academic Search

The influence of PtRu surface alloy formation and of coadsorbed CO on the adsorption\\/desorption characteristics of hydrogen on bimetallic PtRu surfaces was investigated by temperature programmed desorption, using a 40% Pt containing PtRu surface alloy pseudomorphic on a Ru(0001) surface with an almost statistical distribution of Pt surface atoms as substrate. Alloy formation leads to a significant broadening of the

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

2003-01-01

195

Internal Technical Report, Low-To-Moderate Temperature Reservoir Engineering Research Program - Fiscal Year 1982  

SciTech Connect

Numerous low (<90 C) to moderate (90 C-150 C) geothermal resources occur in many areas of the United States. The reservoir research conducted at the Idaho National Engineering Laboratory (INEL) is designed to develop innovative techniques that can be used to evaluate reservoir characteristics and improve reservoir management for low-to-moderate temperature resources. The purpose of this report is to review the program accomplishments for FY 1982 and present the initial data and results obtained from the ongoing research program. The project tasks reported in this document are: (1) Low-To-Moderate Temperature Hydrothermal Reservoir Engineering Handbook; and (2) Reservoir Assessment Technique Development--data analysis and reaction kinetics.

Russell, B.F.; Dolenc, M.R.; Downs, W.F.; Hull, L.C.

1982-09-01

196

APPLICATION OF PELEG'S EQUATION IN DESORPTION STUDIES OF FOOD SYSTEMS: A CASE STUDY WITH SAGO METROXYLON SAGU ROTTB STARCH  

Microsoft Academic Search

Moisture desorption is pertinent to the modelling of dehydration of food systems. The variation of moisture content with time during desorption of sago starch from six towns in Papua New Guinea was analysed using Peleg's equation. Three temperatures (30° 407deg; and 45° C) and four aw ranging from 0.103 - 0.923 were studied. The equation gave a highly significant fit

P. A. SOPADE; K. KAIMUR

1999-01-01

197

Desorption of ciprofloxacin from clay mineral surfaces.  

PubMed

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

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

2012-10-13

198

Dissociative and molecular adsorption and recombinative desorption of methylchlorosilanes at the Cu (001) surface  

NASA Astrophysics Data System (ADS)

The Direct Synthesis of dichlorodimethylsilane above Cu/Si containing surfaces, is central to the commercial manufacture of many silicone materials. The atomic scale mechanisms responsible for the high selectivity for dichlorodimethylsilane, vs. other chloromethylsilanes, is poorly understood. As part of a more extensive program we report here on the interactions of chloromethylsilanes with copper. Adsorption of dichlorodimethylsilane on Cu(001) is, at least in part, dissociative. Yet AES indicates non-stoichiometric surface concentrations of Cl and C. This observation, which is apparent in both low (140K) and room temperature exposures, is indicative of a facile recombinative desorption process. Subsequent TPD spectra also indicate the desorption of not only the parent adsorbate, but other species also. Indeed the combined cracking patterns, of simultaneously desorbing species, are inconsistent with solely (CH3)xSiCly species. We report on the TPD, AES, and high-resolution helium atom scattering studies of (i) adsorption of methylchlorosilanes, and (ii) their coadsorption with added SiH4, CH3 and Cl species, on Cu(001). Evidence for methyl cracking, and disilane production will discussed.

Lallo, J.; Goncharova, L. V.; Ermakov, A. V.; Hinch, B. J.; Strongin, D.

2007-03-01

199

Evolution of hydrogen chloride during temperature-programmed pyrolysis of Illinois coals  

Microsoft Academic Search

Evolution of volatile chlorine species during coal pyrolysis has been studied using a new temperature-programmed heating and gas-combustion technique. The pyrolysis apparatus consists of a pyrolysis chamber and an adjoining combustion chamber. Samples of coal are heated from ambient temperature to 800 C at a rate of 20 C\\/min in the pyrolysis chamber under a nitrogen atmosphere. The volatile products

C. L. Chou; K. C. Hackley; G. L. Donnals; J. Cao; R. R. Ruch

1992-01-01

200

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

Microsoft Academic Search

This topical report of the US Department of Energy High-Temperature Turbine Technology (DOE-HTTT) Phase II program presents the results of testing full-scale water-cooled first-stage and second-stage turbine nozzles at design temperature and pressure to verify that the designs are adequate for operation in a full-scale turbine environment. Low-cycle fatigue life of the nozzles was demonstrated by subjecting cascade assemblies to

1982-01-01

201

Low energy electron stimulated desorption from DNA films dosed with oxygen  

SciTech Connect

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

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

2012-06-21

202

Moisture sorption and desorption in epoxy resin matrix composites  

Microsoft Academic Search

An experimental study of moisture diffusion in three high temperature epoxy resin matrix advanced composite materials - Narmco's T300\\/5208, Hercules' AS\\/3501-5, and AVCO's Boron (4 mil fibers)\\/5505 - was undertaken to aid in determining the amount of moisture that might be absorbed by an epoxy composite structural component during its service life. The moisture sorption and desorption behavior was measured

Shirrell

1978-01-01

203

Modeling Moisture Desorption Isotherms and Thermodynamic Properties of Fermented Tea Dhool (Camellia sinensis var. assamica)  

Microsoft Academic Search

The desorption isotherms of fermented tea dhool were determined at 50, 55, 60, and 70°C by using static gravimetric method of saturated salt solutions within the water activity range of 0.05–0.81. Results indicated that the equilibrium moisture contents were decreased with the increase in temperature. A modified Oswin model was well fitted with the experimental data. Desorption isotherm curves obtained

W. S. Botheju; K. S. P. Amarathunge; M. T. Ziyad Mohamed

2008-01-01

204

Adsorption and desorption kinetics for hydrophilic and hydrophobic vapors on activated carbon  

Microsoft Academic Search

Adsorption dynamics are of fundamental importance in applications of adsorbents in real situations. The adsorption\\/desorption characteristics of a series of adsorbates, with varying hydrophilic\\/hydrophobic and structural characteristics, for activated carbon BAX950, were investigated for temperatures in the range 288–323K. These data provide a comprehensive kinetic study of adsorption\\/desorption for an activated carbon. The results are discussed in relation to the

Ashleigh J. Fletcher; Yaprak Yüzak; K. Mark Thomas

2006-01-01

205

Note: Heated sample platform for in situ temperature-programmed XPS  

NASA Astrophysics Data System (ADS)

We present the design, fabrication, and performance of the multi-specimen heated platform for linear in situ heating during the Temperature-Programmed XPS (TPXPS). The platform is versatile, compatible with high vacuum (HV) and bakeout. The heater platform is tested under in situ linear heating of typical high surface area sorbent/catalyst support - nanoporous TiO2. The platform allows the TPXPS of multiple samples located on specimen disk that can be transferred in and out of the TPXPS chamber. Electric characteristics, temperature and pressure curves are provided. Heating power supply, PID temperature controller, data-logging hardware and software are described.

Samokhvalov, Alexander; Tatarchuk, Bruce J.

2011-07-01

206

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

SciTech Connect

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

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

1999-06-30

207

Temperature Logging in Difficult Environments: Examples from the Ocean Drilling Program  

Microsoft Academic Search

In the past 10 years, the Ocean Drilling Program (ODP) has drilled several medium to high temperature environments (T = 150-312 deg C). These environments include the Costa Rica Rift (Legs 140 and 148), the Middle Valley of the northern Juan de Fuca Ridge (Legs 139 and 169), the Trans-Atlantic Geotraverse (TAG) area (Leg 158), and the Manus Basin (Leg

G. J. Iturrino; D. Goldberg; G. Guerin; W. Masterson; A. Meltser; G. Myers; E. Scholz

2001-01-01

208

Testing program for concrete at temperatures to 894/sup 0/K. [LMFBR  

SciTech Connect

A test program was conducted to define the variations in mechanical properties of a limestone aggregate concrete and a lightweight insulating concrete exposed to elevated temperatures. Four test series were conducted: (1) unconfined compression; (2) shear; (3) rebar bond; and (4) sustained loading (creep). Tests results are presented.

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

1981-01-01

209

CRC Low- and Intermediate- Temperature Driveability Program Using Gasoline-Alcohol Blends.  

National Technical Information Service (NTIS)

A cooperative test program was conducted in 1986 and 1987 to characterize the relationship between cold-start and warmup driveability and gasoline volatility parameters of T10, T50, and T90 distillation temperatures. Hydrocarbon-only and gasoline-alcohol ...

1990-01-01

210

Apparatus for dynamic measurement of gases released from materials heated under programmed temperature-time control  

Microsoft Academic Search

This apparatus, a prototype of one being constructed for hotcell examination of irradiated nuclear materials, measures dynamic release rates and integrated volumes of individual gases from materials heated under controlled temperature-time programs. It consists of an inductively heated vacuum furnace connected to a quadrupole mass spectrometer. A computerized control system with data acquisition provides scanning rates down to 1s and

J. W. Early; R. M. Abernathey

1982-01-01

211

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

ERIC Educational Resources Information Center

|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)|

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

1984-01-01

212

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

SciTech Connect

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.

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

2009-06-01

213

Investigation of high-speed gas chromatography using synchronized dual-valve injection and resistively heated temperature programming.  

PubMed

High-speed temperature programming is implemented via the direct resistive heating of the separation column (2.3m MXT-5 Silicosteel column with a 180 microm I.D. and a 0.4 microm 5% phenyl/95% dimethyl polysiloxane film). Resistive temperature programming was coupled with synchronized dual-valve injection (with an injection pulse width of 2 ms), producing a complete high-speed gas chromatography (GC) system. A comparison of isothermal and temperature programmed separations of seven n-alkanes (C(6) and C(8)-C(13)) shows a substantial improvement of peak width and peak capacity with temperature programming. The system was further implemented in separations of a mixture of analytes from various chemical classes. Separations of the n-alkane mixture using three different temperature programming rates are reported. A temperature programming rate as high as 240 degrees C/s is demonstrated. The method for determination of temperature programming rate, based on isothermal data, is discussed. The high-speed resistive column heating temperature programming resulted in highly reproducible separations. The highest rate of temperature programming (240 degrees C/s) resulted in retention time and peak width RSD, on average, of 0.5 and 1.4%, respectively, for the n-alkane mixture. This high level of precision was achieved with peak widths-at-half-height ranging from 13 to 36 ms, and retention times ranging from 147 to 444 ms (for n-hexane to n-tridecane). PMID:17386929

Reid, Vanessa R; McBrady, Adam D; Synovec, Robert E

2007-03-16

214

D2 sticking coefficient and desorption rate on various forms of water ice films under interstellar conditions  

NASA Astrophysics Data System (ADS)

Gas-grain interactions play a key role in the formation of molecular hydrogen in the ISM. An experimental facility named FORMOLISM (Molecular Formation in the Interstellar Medium) has recently been developed in our laboratory in order to investigate the catalytic role played by the grain in the chemical reaction producing H2 in conditions similar to the interstellar medium. A differentially pumped atomic beam of H or D is directed to surface sample which can be cooled down to 8K, in the centre of an ultra high vacuum chamber (<10-10 mBar). Temperature-Programmed Desorption experiments (TPD) can be performed and the desorbing molecules can be selectively probed in their individual (v, J) levels, thanks to the (2+1) Resonance Enhanced Multi-photon Ionisation (REMPI) method. Ions are detected by using a Time-Of-Flight mass spectrometer. Our experiment gives access to fast reactions mechanisms that can not be probed in conventional TPD experiments. REMPI coupling with TOF detection and atomic dosing can be performed simultaneously. In order to determine H and H2 interaction on water ice surfaces, we are conducting a detailed study of D2 adsorbed on different forms of water ice films using both TPD and REMPI techniques. The ice morphology is controlled by changing vapour deposition temperature and subsequent annealing. Variations of D2 sticking coefficients and desorption rate with surface temperature are compared in high density amorphous water ice, and low density amorphous water ice of different porosity.

Amiaud, L.; Baouche, S.; Dulieu, F.; Fillion, J.-H.; Momeni, A.; Lemaire, J.-L.

2004-12-01

215

Gas desorption and electron emission from 1 MeV potassium ion bombardment of stainless steel  

NASA Astrophysics Data System (ADS)

Gas desorption and electron emission coefficients were measured for 1MeV 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 ?e scale as 1/cos((?) up to angles of 86°, where ?e=90. Nearer grazing incidence, ?e is reduced below the 1/cos((?) scaling by nuclear scattering of ions through large angles, reaching ?e=135 at 88°. Electrons were emitted with a measured temperature of ˜30 eV. Gas desorption coefficients ?0 were much larger, of order ?0=104. They also varied with angle, but much more slowly than 1/cos((?). 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 of10 and gas desorption by a factor of2; a mild bake to ˜220° 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.

Molvik, Arthur W.; Covo, Michel Kireeff; Bieniosek, Frank M.; Prost, Lionel; Seidl, Peter A.; Baca, David; Coorey, Adam; Sakumi, Akira

2004-09-01

216

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

PubMed

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

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

2012-12-11

217

Modelling metal desorption kinetics in estuaries  

Microsoft Academic Search

The kinetics of desorption of Cd, Cu, Ni and Zn from riverine and estuarine sediments have been determined in deionised water and seawater (salinity=30). The time-dependent release of Cd, Cu and Ni from riverine sediments in both media showed an increase in dissolved metal concentrations within a few minutes, followed by a plateau after several hours of incubation. Desorption of

G. E. Millward; Y. P. Liu

2003-01-01

218

Adsorption and desorption characteristics of arsenic onto ceria nanoparticles.  

PubMed

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 (?H0, ?S0, and ?G0) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment. PMID:22269298

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

2012-01-23

219

Adsorption/desorption of amine fluorides to hydroxyapatite.  

PubMed

This study concerned the adsorption and desorption of commercial amine fluoride (AmF) preparations to hydroxyapatite (HA). The influence of pH, ionic strength, temperature, saliva and albumin, the latter as a gingival crevicular fluid analogue, on adsorption/desorption was investigated. AmF levels were determined using a surfactant electrode. AmFs 297 and 335 were found to bind immediately and irreversibly to HA in water over a range of pH values, ionic strengths and temperatures, the amounts increasing with concentration. More monovalent AmF 335 was absorbed than divalent AmF 297. Any AmF desorbed by water from HA was at the lowest end of the minimum inhibitory concentration for oral bacteria. AmF 297 was desorbed by CaCl2, and to a lesser extent by H+, OH-, NH4+, La3+, EDTA, Triton X100 and ethanol, whereas AmF 335 was only slightly desorbed by ethanol. Preadsorption of proteins on HA had little effect on subsequent adsorption or desorption of either AmF. It is postulated that both AmF 297 and AmF 335 are inactivated by an excess of proteins in the surrounding medium, supra- or subgingivally, and not by such proteins preventing or altering the mode or rate of adsorption, or interfering with antibacterial activity, when the AmFs contact a protein-coated tooth surface. PMID:8962946

Sefton, J; Lambert, M; Wilson, M; Newman, H N

1996-01-01

220

Adsorption and desorption characteristics of arsenic onto ceria nanoparticles  

PubMed Central

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 (?H0, ?S0, and ?G0) 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.

2012-01-01

221

Laser desorption jet cooling spectroscopy  

NASA Astrophysics Data System (ADS)

Laser desorption followed by jet-cooling allows wavelength-selective as well as mass-selective detection of organic molecules desorbed from a surface without fragmentation. The absolute detection sensitivity is demonstrated with the perylene molecule. A two-color REMPI spectrum (400 wavelength points) of perylene is recorded using only 30 picogram of material. Rotational cooling to 5 - 10 K is demonstrated with laser-desorbed anthracene; vibrational cooling below 15 K is demonstrated with laser-desorbed diphenylamine. The ability to take a 'snapshot' of molecules on a surface is illustrated with the spectrum of benzoic acid monomers. Other applications are discussed, i.e. PABA dimer spectroscopy and detection of C60.

de Vries, Mattanjah S.; Hunziker, Heinrich E.; Meijer, Gerard; Wendt, H. R.

1991-04-01

222

VAC*TRAX - Thermal desorption for mixed wastes  

SciTech Connect

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.

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

1995-12-01

223

Dynamics of desorption with lateral diffusion  

NASA Astrophysics Data System (ADS)

The dynamics of desorption from a submonolayer of adsorbed atoms or ions are significantly influenced by the absence or presence of lateral diffusion of the adsorbed particles. When diffusion is present, the adsorbate configuration is simultaneously changed by two distinct processes, proceeding in parallel: adsorption/desorption, which changes the total adsorbate coverage, and lateral diffusion, which is coverage conserving. Inspired by experimental results, we here study the effects of these competing processes by kinetic Monte Carlo simulations of a simple lattice-gas model. In order to untangle the various effects, we perform large-scale simulations, in which we monitor coverage, correlation length, and cluster-size distributions, as well as the behavior of representative individual clusters, during desorption. For each initial adsorbate configuration, we perform multiple, independent simulations, without and with diffusion, respectively. We find that, compared to desorption without diffusion, the coverage-conserving diffusion process produces two competing effects: a retardation of the desorption rate, which is associated with a coarsening of the adsorbate configuration, and an acceleration due to desorption of monomers ``evaporated'' from the cluster perimeters. The balance between these two effects is governed by the structure of the adsorbate layer at the beginning of the desorption process. Deceleration and coarsening are predominant for configurations dominated by monomers and small clusters, while acceleration is predominant for configurations dominated by large clusters.

Juwono, Tjipto; Rikvold, Per Arne

2013-09-01

224

Final report of comprehensive testing program for concrete at elevated temperatures  

SciTech Connect

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

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

1980-10-01

225

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

NASA Astrophysics Data System (ADS)

Complex analytical problems, such as detecting trace quantities of hazardous chemicals in challenging environments, require solutions that most effectively extract relevant information about a sample's composition. This review presents a chemiresistive microarray-based approach to identifying targets that combines temperature-programmed elements capable of rapidly generating analytically rich data sets with statistical pattern recognition algorithms for extracting multivariate chemical fingerprints. We describe the chemical-microsensor platform and discuss its ability to generate orthogonal data through materials selection and temperature programming. Visual inspection of data sets reveals device selectivity, but statistical analyses are required to perform more complex identification tasks. Finally, we discuss recent advances in both devices and algorithms necessary to deal with practical issues involved in long-term deployment. These issues include identification and correction of signal drift, challenges surrounding real-time unsupervised operation, repeatable device manufacturability, and hierarchical classification schemes designed to deduce the chemical composition of untrained analyte species.

Meier, Douglas C.; Raman, Baranidharan; Semancik, Steve

2009-07-01

226

Mercury speciation in gypsums produced from flue gas desulfurization by temperature programmed decomposition  

Microsoft Academic Search

Temperature programmed decomposition was used to identify mercury (Hg) species in gypsum samples produced from flue gas desulfurization in two Spanish power stations (A and B). As stricter emission control\\/reduction policies, particularly those focusing on Hg, are being implemented, wet flue gas desulfurization (FGD) technologies used for the removal of SO2 can result in the co-removal of highly-soluble oxidized Hg.

Manuela Rallo; M. Antonia Lopez-Anton; Ron Perry; M. Mercedes Maroto-Valer

2010-01-01

227

A 70-kyr sea surface temperature record off southern Chile (Ocean Drilling Program Site 1233)  

Microsoft Academic Search

We present the first high-resolution alkenone-derived sea surface temperature (SST) reconstruction in the southeast Pacific (Ocean Drilling Program Site 1233) covering the major part of the last glacial period and the Holocene. The record shows a clear millennial-scale pattern that is very similar to climate fluctuations observed in Antarctic ice cores, suggesting that the Southern Hemisphere high-latitude climate changes extended

J. Kaiser; F. Lamy; D. Hebbeln

2005-01-01

228

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

Microsoft Academic Search

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

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

2007-01-01

229

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

Microsoft Academic Search

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

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

2008-01-01

230

Theoretical study of In desorption and segregation kinetics in MBE growth of InGaAs and InGaN  

Microsoft Academic Search

A rate equation model is employed to investigate the surface dynamic processes such as In desorption, incorporation and segregation in the MBE growth of InGaAs and InGaN. In both cases, the agreement between our results and that of the experiment is good. In InGaAs growth, In desorption increases with increasing substrate temperature or group III–V over pressure ratio. The desorption

Irena Stanley; Golshan Coleiny; Rama Venkat

2003-01-01

231

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

SciTech Connect

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.

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

232

Laser desorption jet-cooling of organic molecules  

NASA Astrophysics Data System (ADS)

Laser desorption followed by jet-cooling allows wavelength-selective as well as mass-selective detection of molecules desorbed from a surface without fragmentation. The cooling characteristics and detection sensitivity of laser desorption jet-cooling of organic molecules are investigated. From the rotational contour of the electronic origin of the S 1 ? S 0 transition of laser-desorbed anthracene, rotational cooling to 5 10 K is demonstrated. Vibrational cooling is studied for laser-desorbed diphenylamine, a molecule with low-energy vibrations, and a vibrational temperature below 15 K is found. The absolute detection sensitivity is determined for the perylene molecule. Using two-color (1+1) resonance enhanced multi-photon ionization (with a measured ionization efficiency of 0.25) for detection, it is found that one ion is produced in the detection region for every 2×105 perylene molecules evaporated from the desorption laser spot. A two-color (1+1) REMPI spectrum (400 points) of perylene is recorded using only 30 picogram of material.

Meijer, G.; de Vries, M. S.; Hunziker, H. E.; Wendt, H. R.

1990-12-01

233

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

SciTech Connect

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.

Eika W. Qian; T. Horio; I. Putu Sutrisna [Tokyo University of Agriculture and Technology, Tokyo (Japan). Department of Chemical Engineering

2009-03-15

234

Desorption corona beam ionization source for mass spectrometry.  

PubMed

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

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

2010-04-01

235

Plasma Desorption Mass Spectrometry: Coming of Age.  

ERIC Educational Resources Information Center

|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)|

Cotter, Robert J.

1988-01-01

236

Matrix effects in plasma desorption mass spectrometry  

Microsoft Academic Search

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

Stephane Bouchonnet; Yannik Hoppilliard; Christine Mauriac

1993-01-01

237

Study of desorption kinetics of polycyclic aromatic hydrocarbons (PAHs) from solid matrices using internally cooled coated fiber.  

PubMed

The kinetics of desorption of hydrophobic organic compounds (HOCs) from soil and sediment particles is important both from environmental and analytical chemistry points of view. Reliable techniques are required for prediction of desorption behaviour of HOCs from contaminated soils and sediments. In this study internally cooled coated fiber device, in which a PDMS hollow fiber extraction phase is cooled with liquid CO(2), was used as an exhaustive extraction sorbent phase for extraction of desorbed organic compounds (e.g. polycyclic aromatic hydrocarbons, PAHs) from both laboratory-spiked and naturally contaminated solid sample into the gaseous headspace in a batch system. The extraction time profiles were obtained at two different elevated temperatures (above 100 degrees C) for spiked sand and silica gel matrices. The slow desorption rate constants at each temperature were determined from desorption plots and the apparent activation energies of desorption were obtained from Arrhenius equations. The apparent activation energies of desorption of naphthalene, acenaphthylene and acenaphthene, from spiked silica gel, were approximately 60kJmol(-1), and were higher, 70 and 100kJmol(-1) for fluoranthene and anthracene, respectively. The fast and slow desorption rates and apparent activation energies of desorption for PAHs were obtained by spiking a naturally contaminated sediment sample with deuterated PAHs (PAHs-d(10)). The activation energies of native PAHs were higher than those of spiked deuterated PAHs, suggesting that the native compounds were more affected by retarded pore diffusion or slow mass transfer through glassy sorbent organic matter (SOM). The proposed technique in the present study is fully automated, and can extract the contaminants from the solid matrix fast and exhaustively, which makes it more time efficient and versatile compared to the commonly used technique for desorption studies, i.e. vial desorption. PMID:19786184

Haddadi, Shokouh H; Niri, Vadoud H; Pawliszyn, Janusz

2009-05-27

238

Electron induced reactions in molecular nanofilms of chlorodifluoroacetic acid (CClF2COOH): Desorption of fragment anions and formation of CO2  

NASA Astrophysics Data System (ADS)

Electron induced reactions in molecular nanofilms of chlorodifluoroacetic acid (CClF2COOH) are studied by electron stimulated desorption (ESD) of fragment anions and temperature programed thermal desorption spectroscopy (TDS). The fragment anions O-, F-, OH-, and Cl- are formed from broad resonance features in the energy range of 4-14 eV and assigned to dissociative electron attachment (DEA) of molecules or dimers at or near the surface of the film, followed by desorption. The strong low energy DEA resonances (0-2 eV) observed in a previous gas phase study [J. Kopyra et al., Int. J. Mass. Spectrom. 285, 131 (2009)] are completely suppressed in ESD. Electron irradiation at energies above 10 eV results in the formation of CO2, as revealed by TDS. The extended irradiation of a 3 ML film (25 nA, 240 min) results in a nearly completely transformation of the initial compound in favor of CO2 and other by-products.

Orzol, Mario; König-Lehmann, Constanze; Illenberger, Eugen; Kopyra, Janina

2010-11-01

239

Thermal desorption of the PO radical from polycrystalline Pt surfaces  

NASA Astrophysics Data System (ADS)

The PO radical was detected to desorb from polycrystalline Pt surfaces during the catalytic decomposition of dimethyl methyl phosphonate and trimethyl phosphite above 1100 K using the laser-induced fluorescence technique. The activation energy for the desorption of adsorbed PO radicals, PO(a) ? PO(g), was determined to be 59±2 kcal/mol in the temperature range 1100-1350 K at different radical source pressures. The mechanisms for PO production from these two catalytic reactions are briefly discussed.

Dulcey, C. S.; Lin, M. C.; Hsu, C. C.

1985-04-01

240

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

SciTech Connect

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

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

2007-01-01

241

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

PubMed

A novel method for collection and analysis of vapor-phase semivolatile organic compounds (SOCs) in ambient air is presented. The method utilizes thermal desorption of SOCs trapped in diffusion denuders coupled with cryogenic preconcentration on Tenax-TA and analysis by high resolution gas chromatography (GC)-electron-capture detection (ECD). The sampling and analysis methods employ custom-fabricated multicapillary diffusion denuders, a hot gas spike (HGS) apparatus to load known quantities of thermally stable standards into diffusion denuders prior to sample collection, a custom-fabricated oven to thermally desorb SOCs from the diffusion denuder, and a programmable temperature vaporization (PTV) inlet containing a liner packed with Tenax-TA for effective preconcentration of the analytes and water management. High flow rates into the PTV inlet of 750mLmin(-1)during thermal desorption are ca. a factor of ten greater than typically used. To improve resolution and retention time stability, the thermal desorption and PTV inlet programming procedure includes three steps to prevent water from entering the analytic column while effectively transferring the analytes into the GC system. The instrumentation and procedures provide virtually complete and consistent transfer of analytes collected from ambient air into the GC evidenced by recovery of seven replicates of four internal standards of 90.7+/-4.0-120+/-23% (mean+/-95% confidence interval, CI). Retention time based compound identification is facilitated by low retention time variability with an average 95% CI of 0.024min for sixteen replicates of eight standards. Procedure details and performance metrics as well as ambient sampling results are presented. PMID:17150222

Tobias, David E; Perlinger, Judith A; Morrow, Patrick S; Doskey, Paul V; Perram, David L

2006-12-05

242

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

SciTech Connect

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.

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

2012-09-05

243

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

NASA Astrophysics Data System (ADS)

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

Näslund, Lars-Åke

2013-12-01

244

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

SciTech Connect

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.

Blackaby, W.B.

1994-09-06

245

Advanced, Small, High-Temperature-Rise Combustor Program. Volume II. Design and Test of Full-Scale Combustion System.  

National Technical Information Service (NTIS)

The report describes an analytical and experimental study of advanced, small, high-temperature combustors. This volume describes the third and final phase of this program which included the design and performance verification tests of a full-scale combust...

K. M. Johansen M. P. Wood

1974-01-01

246

A temperature programmed evaporation method for exact determination of the amount of stationary phase in chromatographic column packings  

Microsoft Academic Search

A new temperature programmed evaporation method for determination of amount of stationary phase in chromatographic column packings has been developed. The results obtained by testing the method and its applicability have been discussed.

R. N. Nikolov; N. D. Petsev; A. D. Stefanova

1976-01-01

247

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

PubMed Central

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

2013-01-01

248

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

PubMed

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

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

2013-07-31

249

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

250

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

SciTech Connect

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.

Walker, D.D.

2001-02-13

251

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

SciTech Connect

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 materials needed to ensure their safe and reliable operation. The focus of this document will be the overall range of DOE's structural materials research activities being conducted to support VHTR development. By far, the largest portion of material's R&D supporting VHTR development is that being performed directly as part of the Next-Generation Nuclear Plant (NGNP) Project. Supplementary VHTR materials R&D being performed in the DOE program, including university and international research programs and that being performed under direct contracts with the American Society for Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, will also be described. Specific areas of high-priority materials research that will be needed to deploy the NGNP and provide a basis for subsequent VHTRs are described, including the following: (1) Graphite: (a) Extensive unirradiated materials characterization and assessment of irradiation effects on properties must be performed to qualify new grades of graphite for nuclear service, including thermo-physical and mechanical properties and their changes, statistical variations from billot-to-billot and lot-to-lot, creep, and especially, irradiation creep. (b) Predictive models, as well as codification of the requirements and design methods for graphite core supports, must be developed to provide a basis for licensing. (2) Ceramics: Both fibrous and load-bearing ceramics must be qualified for environmental and radiation service as insulating materials. (3) Ceramic Composites: Carbon-carbon and SiC-SiC composites must be qualified for specialized usage in selected high-temperature components, such as core stabilizers, control rods, and insulating covers and ducting. This will require development of component-specific designs and fabrication processes, materials characterization, assessment of environmental and irradiation effects, and establishment of codes and standards for materials testing and design requirements. (4) Pressure Vessel Steels: (a) Qualification of short-term, high-temperature properties of light water rea

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

2008-08-01

252

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

SciTech Connect

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.

Roy, Anupam; Batabyal, R.; Mahato, J. C.; Dev, B. N. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Sundaravel, B. [Materials Science Division, Indira Gandhi Center for Atomic Research, Kalapakkam 603102 (India)

2011-07-15

253

ADSORPTION AND DESORPTION CHARACTERISTICS OF AIR ON ZEOLITE 5A, 10X, AND 13X FIXED BEDS  

Microsoft Academic Search

Adsorption and desorption experiments for the binary mixture (N2\\/O2; 79:21 vol%) on zeolite 5A, 10X, and 13X beds were performed to study the dynamic characteristics of air separation adsorption processes. Because the breakthrough and desorption curves showed a tail by temperature variance in the beds, a nonisothermal dynamic model incorporating mass and energy balances was applied to the simulation of adsorption

Jeong-Geun Jee; Myung-Kyu Park; Han-Kyu Yoo; Kangtaek Lee; Chang-Ha Lee

2002-01-01

254

Simulations of the femtosecond laser-induced desorption of CO from Cu(100) at 0.5 ML coverage  

Microsoft Academic Search

Simulations of the femtosecond laser-induced desorption of CO from Cu(100) at an initial temperature of 95K are reported, employing molecular dynamics with electronic frictions. Results are obtained for saturation (0.5 ML) CO coverage, which are compared with additional simulations in the zero coverage limit. In both cases, the desorption yield depends nonlinearly on laser fluence, with initial nonadiabatic energy flow

Clayton Springer; Martin Head-Gordon

1996-01-01

255

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

Microsoft Academic Search

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

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

2000-01-01

256

Characterization of titania surface area in titania\\/silica SCR catalysts by temperature-programmed reaction of 2-propanol  

Microsoft Academic Search

This work describes the adaptation of a temperature-programmed reaction (TPRe) analysis to determine the effective titania surface area (ETSA) in mixed titania\\/silica catalysts used for the selective catalytic reduction of nitrogen oxides. Isopropanol is used as the probe molecule. Since dehydration of the alcohol adsorbed on the titanyl and silanol groups occurs at two distinct temperatures, the exposed (or effective)

J. E. Swain; M. V. Juskelis; J. P. Slanga; J. G. Miller; M. Uberoi; N. D. Spencer

1996-01-01

257

Kinetics of petroleum generation by programmed-temperature closed-versus open-system pyrolysis  

NASA Astrophysics Data System (ADS)

Bulk petroleum generation by programmed-temperature pyrolysis of immature ( R r = 0.48%) Posidonia (Toarcian) Shale samples at heating rates of 0.1, 0.7, and 5.0 K/min has been studied comparatively under open- and closed-system conditions, using the microscale sealed vessel (MSSV) technique in the latter case. The comparison of formation rates required a differentiation (vs. temperature) of closed-system cumulative product evolution profiles. The kinetic analysis assuming twenty-five first order parallel reactions with activation energies regularly spaced between 46 and 70 kcal/mol and a single preexponential factory yielded the same value of A = 1.08 · 10 16 min -1 and very similar petroleum potential vs. activation energy distributions centered around 54 kcal/mol in both cases. In particular, both approaches turned out to be in excellent agreement with respect to predicting temperature ranges of oil and gas formation under geological heating conditions. This is in contrast to the case of petroleum yield assessment which appears to be more system-dependent.

Schenk, H. J.; Horsfield, B.

1993-02-01

258

BEAM PIPE DESORPTION RATE IN RHIC.  

SciTech Connect

In the past, an increase of beam intensity in RHIC has caused several decades of pressure rises in the warm sections during operation. This has been a major factor limiting the RHIC luminosity. About 430 meters of NEG coated beam pipes have been installed in the warm sections to ameliorate this problem. Beam ion induced desorption is one possible cause of pressure rises. A series beam studies in RHIC has been dedicated to estimate the desorption rate of various beam pipes (regular and NEG coated) at various warm sections. Correctors were used to generate local beam losses and consequently local pressure rises. The experimental results are presented and analyzed in this paper.

HUANG, H.; FISCHER, W.; HE, P.; HSEUH, H.C.; IRISO, U.; PTITSYN, V.; TRBOJEVIC, D.; WEI, J.; YANG, S.Y.

2006-06-23

259

Relationship between Ultraviolet Photon Stimulated Desorption Mechanisms and Fundamental Materials Properties.  

National Technical Information Service (NTIS)

The statement of work involved free-electron-laser-related activities using synchrotron uv sources and frequency up-converted laser light: (1) to measure the energy dependence of photon-induced processes of desorption; to vary temperatures of the irradiat...

N. H. Tolk R. F. Haglund

1986-01-01

260

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

EPA Science Inventory

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

261

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

SciTech Connect

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

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

2000-01-26

262

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)

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.

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

2004-03-01

263

Structural and surface property changes of macadamia nut-shell char upon activation and high temperature treatment  

Microsoft Academic Search

Structural and surface property changes of macadamia nut-shell (MNS) char upon activation and high temperature treatment (HTT) were studied by high-resolution nitrogen adsorption, diffuse reflectance infra-red Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption. It is found that activation of MNS char can be divided into the low extent activation which may involve the reactions of internal oxygen-containing groups

Zheng-Ming Wang; Hirofumi Kanoh; Katsumi Kaneko; G. Q Lu; Duong Do

2002-01-01

264

[Carbon dioxide SHF-desorption from liquid regenerated sorbent in a physicochemical human life support system].  

PubMed

Desorption of carbon dioxide from monoethanol ethylene diamine solution with the use of SHF was compared to the thermal technology both in static condition and with a fixed absorbent expenditure. In the static condition, CO2 evacuation by SHF was more complete, without precipitation, and within a short interaction time. With absorbent expenditure and CO2 production rate permanent, SHF desorption occurred at a lower temperature and, therefore, lower absorbed power than the conventional thermal process. Testing demonstrated efficiency of the non-inertial volumetric SHF heating in regeneration of the liquid absorbent charged in physicochemical life support systems for different pressurized habitats. PMID:15500172

Klimarev, S I

265

Determination of hydrogen absorption and desorption processes in aluminum melts by continuous hydrogen activity measurements  

NASA Astrophysics Data System (ADS)

Continuous hydrogen activity measurement by pressure evaluation in liquid metals is a useful technique for the direct determination of hydrogen concentration changes in melts of aluminum and aluminum alloys and for the detection of sensitive steps in hydrogen absorption and desorption processes. This is demonstrated by various experiments performed with melts of pure aluminum. They show that undamaged pure Al2O3 oxide skins can prevent H2 absorption of aluminum melts and retard the desorption process to very low rates at temperatures below 800 °C.

Weigel, J.; Fromm, E.

1990-10-01

266

Desorption activation energies for tritium release from ceramic breeders  

SciTech Connect

Desorption has been identified as an important process in determining the kinetics of tritium release from ceramic tritium breeder materials considered for use in fusion reactors. However, details of the desorption of tritium from ceramic materials are mostly unknown. Models of tritium release have treated desorption as a simple process with desorption occurring from one type of site with one activation energy. Recent measurements of the rates of water uptake by LiAlO/sub 2/, and evolution of water from LiAlO/sub 2/ exposed to water, indicate the presence of multiple types of desorption sites. Estimates of desorption activation energies were obtained from these data and from data in the literature suggesting multiple types of desorption sites for desorption from Li/sub 2/O and Li/sub 4/SiO/sub 4/. 15 refs., 4 figs.

Kopasz, J.P.; Fischer, A.K.; Johnson, C.E.

1989-01-01

267

Kinetics of Cd sorption, desorption and fixation by calcite: A long-term radiotracer study  

NASA Astrophysics Data System (ADS)

Time-dependent sorption and desorption of Cd on calcite was studied over 210 days utilizing 109Cd as a tracer to distinguish between 'labile' and 'non-labile' forms of sorbed Cd. Stabilizing the calcite suspensions for 12 months under atmospheric P CO2 and controlled temperature was necessary to reliably follow Cd dynamics following initial sorption. Results revealed time-dependant Cd sorption and marked desorption hysteresis by calcite under environmentally relevant conditions. Data obtained were fitted to a first-order kinetic model and a concentric shell diffusion model. Both models described the progressive transfer of Cd 2+ to a less reactive form within calcite and subsequent desorption of Cd subject to different initial contact times. The kinetic model provided a better fit to the combined sorption and desorption data ( R2 = 0.992). It differentiates between two 'pools' of sorbed Cd 2+ on calcite, 'labile' and 'non-labile', in which labile sorbed Cd is in immediate equilibrium with the free Cd 2+ ion activity in solution whereas non-labile Cd is kinetically restricted. For the diffusion model ( R2 = 0.959), the rate constants describing Cd dynamics in calcite produced a half-life for Cd desorption of ˜175 d, for release to a 'zero-sink' solution. Results from this study allow comment on the likely mechanisms occurring at the calcite surface following long-term Cd sorption.

Ahmed, Imad A. M.; Crout, Neil M. J.; Young, Scott D.

2008-03-01

268

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

SciTech Connect

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.

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

2004-03-31

269

Thermal desorption treatment (February 1994). Engineering bulletin  

SciTech Connect

The bulletin discusses various aspects of the thermal desorption technology including applicability, limitations of its use, residuals produced, performance data, site requirements, status of the technology, and sources of further information. The document is an update of the original bulletin published in May 1991 (PB92-228080).

Rawe, J.; Saylor, E.

1994-02-01

270

Indaziflam sorption-desorption in diverse soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Indaziflam is a new preemergence-herbicide active ingredient, classified as a member of the new chemical class “alkylazine”. There is no published information on its fate and behavior in soil. This study is aimed at characterizing the adsorption and desorption of indaziflam in soils with different p...

271

A microsystems enabled field desorption source.  

SciTech Connect

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

Hertz, Kristin L.; Resnick, Paul James; Schwoebel, Paul R. (University of New Mexico, Albuquerque, NM); Holland, Christopher E. (SRI International, Menlo Park, CA); Chichester, David L. (Idaho National Laboratory, Idaho Falls, ID)

2010-07-01

272

Benzene adsorption and desorption in mordenite  

Microsoft Academic Search

The zeolite-catalyzed synthesis of cumene from benzene and propene is an industrially important reaction. We used small mordenite crystals to study benzene adsorption and desorption behaviour for sodium, proton and nitric acid treated mordenite. Adsorption of benzene was for all samples fast and completed within 25 seconds at a benzene partial pressure of 0.12 bar in nitrogen at 423 K.

A. N. C. van Laak; K. P. de Jong; P. E. de Jongh

2007-01-01

273

Electron Stimulated Desorption and Coherent Electron Scattering.  

National Technical Information Service (NTIS)

We have studied electron-stimulated 0(-) desorption from O2 condensed on thick rare-gas (Ar, Kr, or Xe) films, which were previously deposited on a Pt substrate. For ordered rare-gas layers with a fixed O2 coverage, the 0(-) yield increases almost linearl...

H. Sambe D. E. Ramaker L. Parenteau L. Sanche

1987-01-01

274

Fast heavy ion induced desorption of insulators  

Microsoft Academic Search

During the last three years the research of fast heavy ion induced desorption was focussed again on secondary ion emission from organic material. New experiments on total sputter yields have not been performed. The measurements with ordered surface structures - i.e. Langmuir-Blodgett films - gave further evidence for the formation of craters by the impacting particle. This picture is supported

K. Wien

1992-01-01

275

Asphaltene Adsorption and Desorption From Mineral Surfaces  

Microsoft Academic Search

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.

S. T. Dubey; M. H. Waxman

1991-01-01

276

Asphaltene adsorption and desorption from mineral surfaces  

SciTech Connect

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.

Dubey, S.T. (Shell Development Co. (US)); Waxman, M.H.

1991-02-01

277

IN SITU THERMAL DESORPTION OF COAL TAR  

Microsoft Academic Search

In Situ Thermal Desorption (ISTD) is a soil remediation process in which heat and vacuum are applied simultaneously to subsurface soils. Depending on the depth of treatment, an array of either thermal blankets or vacuum\\/heater wells is used. Produced vapors are treated with an air pollution control (APC) system to remove residual contaminants that have not been destroyed in situ.

Kirk S. Hansen; Denis M. Conley; Harold J. Vinegar; John M. Coles; James L. Menotti; George L. Stegemeier

278

Electrochemical desorption of fibrinogen from gold.  

PubMed

The electrochemically induced desorption of Oregon green labeled fibrinogen layers from clean gold surfaces at negative potentials has been probed using capacitance, fluorescence microscopy, and atomic force microscopy. Capacitance measurements on fibrinogen layers indicate that desorption occurs at potentials more negative than -0.8 V and that complete desorption occurs when the electrode is biased at -1.2 V. Significantly, the fluorescence intensity initially increases as the dye labeled protein is electrochemically desorbed due to a decrease in quenching by the gold surface. Following this initial increase, the protein diffuses into solution and the fluorescence intensity decreases over time. More than 90% of the dye labeled fibrinogen is desorbed and diffuses out of the confocal volume in less than 2000 s when the potential is stepped to -1.2 V. AFM before and after application of the desorbing potential confirms removal of the protein. Collection of the desorbed protein in solution reveals a surface coverage of (4.0 +/- 2.3) x 10(-13) mol cm(-2) or an area of occupation of 400 +/- 140 nm(2) per molecule, which indicates that the protein is not extensively spread on the bare gold surface. Significantly, SDS-PAGE analysis indicates that the adsorption-desorption cycle dramatically effects the protein structure, with the electrochemically desorbed fibrinogen showing extensive fragmentation compared to native protein. PMID:20038174

Mallon, Colm T; De Chaumont, Ciaran; Moran, Niamh; Keyes, Tia E; Forster, Robert J

2010-01-01

279

Analytical laser induced liquid beam desorption mass spectrometry of protonated amino acids and their non-covalently bound aggregates  

NASA Astrophysics Data System (ADS)

We have used analytical laser induced liquid beam desorption in combination with high resolution mass spectrometry (m/? mgeq 1 000) for the study of protonated amino acids (ornithine, citrulline, lysine, arginine) and their non-covalently bound complexes in the gas phase desorbed from water solutions. We report studies in which the desorption mechanism has been investigated. The results imply that biomolecule desorption at our conditions is a single step process involving laser heating of the solvent above its supercritical temperature, a rapid expansion, ion recombination and finally isolation and desorption of only a small fraction of preformed ions and charged aggregates. In addition, we report an investigation of the aqueous solution concentration and pH-dependence of the laser induced desorption of protonated species (monomers and dimers). The experimental findings suggest that the desorption process depends critically upon the proton affinity of the molecules, the concentration of other ions, and of the pH value of the solution. Therefore the ion concentrations measured in the gas phase very likely reflect solution properties (equilibrium concentrations). Arginine self-assembles large non-covalent singly protonated multimers (n=1...8) when sampled by IR laser induced water beam desorption mass spectrometry. The structures of these aggregates may resemble those of the solid state and may be preformed in solution prior to desorption. A desorption of mixtures of amino acids in water solution enabled us to study (mixed) protonated dimers, one of the various applications of the present technique. Reasons for preferred dimerization leading to simple cases of molecular recognition as well as less preferred binding is discussed in terms of the number of specific H-bonds that can be established in the clusters.

Charvat, A.; Lugovoj, E.; Faubel, M.; Abel, B.

2002-09-01

280

Low-Temperature Thermal Energy Storage Program. Annual progress report, October 1977--September 1978  

SciTech Connect

The Low-Temperature Thermal Energy Storage (LTTES) Program is part of a national effort to develop means for reducing United States dependence on oil and natural gas as primary energy sources. To this end, LTTES addresses the development of advanced sensible and latent heat storage technologies that permit substitution by solar or off-peak electrical energies or permit conservation by recovery and reuse of waste heat. Emphasis is on applying these technologies to heating and cooling of buildings. As the LTTES program continued to mature, a number of technologies were identified for development emphasis, including (1) seasonal storage of hot and cold water from waste or natural sources in aquifers, (2) short-term or daily storage of heat or coolness from solar or off-peak electrical sources in phase-change materials, and (3) recovery and reuse of rejected industrial heat through thermal storage. These areas have been further divided into three major and four minor activities; significant accomplishments are reported for each.

Brunton, G.D.; Eissenberg, D.M.; Kedl, R.J.

1979-05-01

281

Desorption heat capacity of 3He adsorbed on solid neon  

Microsoft Academic Search

The desorption heat capacity of successive monolayers of 3He adsorbed on solid neon is measured and a rigid band model for the desorption is set up. The agreement between experiment and theory is good. The desorption energy varies between 55 and 25 K for the first layer as a function of coverage and is about 11 K for the second

Per Wennerström; Anders Törne; Torsten Lindqvist

1978-01-01

282

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

PubMed

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. PMID:22432297

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

2011-01-01

283

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...

284

Quantitative analysis of thermally induced desorption during halogen-etching of a silicon (1 1 1) surface  

NASA Astrophysics Data System (ADS)

Thermal desorption at a chlorine-adsorbed Si(1 1 1) surface was measured with high precision. High-sensitivity measurements of the temperature dependence of the isothermal process, and thermal desorption spectra (TDS) with various parameters, heating rates and levels of surface coverage, indicated that the desorption is a second-order reaction with an activation energy of 2.2 eV. The wide dynamic-range data throw light on the ability of various methods of thermal desorption measurement to describe quantitatively the surface reaction. It is important to obtain a precise energy value, which can be done by considering the whole TDS shape, as well as isothermal data, in order to distinguish various reaction processes. Our results are consistent with model calculations.

Shudo, K.; Kirimura, T.; Tanaka, Y.; Ishikawa, T.; Tanaka, M.

2006-08-01

285

Temperature  

NSDL National Science Digital Library

Thermometers record the temperature in a given location. Temperature is a non-living thing because it doesn't physically move or eat, for example. However, temperature is a very important factor that effects where animals live and how long they stay in that particular spot.

Luis Miguel Orta Rial (None;)

2008-03-24

286

Desorption-assisted sun diver missions  

NASA Astrophysics Data System (ADS)

Solar-driven sails which can also accelerate by ``boil off'' of coated materials offer new high-velocity missions. These can take advantage of high temperature characteristics of the sail by using the large solar flux at perihelion. For the near term use of beamed power, beam illumination at ~kW/cm2 in LEO can simulate conditions any solar grazer mission will experience to within 0.01 A.U. Sublimation (or desorption) thrust from LEO into interplanetary orbit can omit the several-year orbits conventional solar sails need to reach ~0.1 AU. A second ``burn'' at perihelion, the highest available orbital velocity in the inner solar system, and thus optimum point for a delta-V, then yields high velocities of ~50 km/s for >40 A.U. missions. The mission begins with deployment in Low Earth Orbit by conventional rocket. Then the launch begins, driven by a microwave beam (and much smaller solar photon thrust) from nearby in orbit. Beam heating makes a ``paint'' (polymer layer #1) desorp from the sail. Under this enhanced thrust, in repeated shots at perihelion in steepening elliptical orbits, the sail attains ~15 km/s velocity, canceling most of its solar orbital velocity, and so can fall edge-on toward the sun immediately. (This is far faster than using solar pressure to spiral down, which takes years.) It approaches the sun edge-on, to minimize radiation pressure on it in the inward fall. At perihelion the spacecraft rotates to face the sun. Under intense sunlight ~20 times Earth insolation, the sail desorps away polymer #2, getting a ~50 km/s boost at its maximum (infall) velocity. It then sails away as a conventional, reflecting solar sail, with the final Aluminum layer revealed. Its final speed is after leaving the solar potential well is ~10 AU/year. Within ~5 years, it sails beyond Pluto, giving high velocity mapping of the outer solar system, the heliopause and interstellar medium. .

Benford, Gregory; Benford, James

2002-01-01

287

Raman spectroscopy and thermal desorption of NH{sub 3} adsorbed on TiO{sub 2} (anatase)-supported V{sub 2}O{sub 5}  

SciTech Connect

The interaction of NH{sub 3} with TiO{sub 2} (anatase) and a series of TiO{sub 2} (anatase)-supported V{sub 2}O{sub 5} catalysts has been investigated using thermal desorption and in situ Raman spectroscopy. NH{sub 3} adsorbs on TiO{sub 2}(a) by coordinating to Ti{sup 4+} Lewis acid sites. Upon heating, most of the adsorbed NH{sub 3} desorbs intact, with only a small amount of N{sub 2} being produced. At V{sub 2}O{sub 5} loadings well below a monolayer, the dispersed vanadia is present on the surface in the form of monomeric vanadyl and polymeric vanadate species. NH{sub 3} adsorbs on vacant Ti{sup 4+} sites not covered by the vanadia and V{sup {minus}+} sites associated with the monomeric vanadyl species. Temperature-programmed desorption of NH{sub 3} adsorbed on the V{sub 2}O{sub 5} loaded samples indicates that NH{sub 3} is more strongly bound to the surface of these materials and displays a higher tendency to dissociate prior to desorbing. Increasing the coverage of the vanadia species to a monolayer results in a weaker NH{sub 3}-surface bond. Desorption studies show that substantial quantities of NO and N{sub 2}O are evolved by oxidation of the NH{sub 3} and reduction of the sample. Raman spectra recorded in the presence of NH{sub 3} at high temperatures indicate that the terminal oxygen atoms of the polyvanadate species and clustered monomeric species are removed preferentially, resulting in the reduction of these species. On the other hand, isolated monomeric vanadyls are not reduced by the adsorbing NH{sub 3}. These results suggest that the dissociation of NH{sub 3} is accelerated by the presence of adjacent V=O groups. 32 refs., 13 figs., 1 tab.

Went, G.T.; Leu, L.J.; Lombardo, S.J.; Bell, A.T. [Lawrence Berkeley Lab., CA (United States)

1992-03-05

288

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

SciTech Connect

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.

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

1989-03-01

289

Quantifying hysteresis of atrazine desorption from a sandy loam soil.  

PubMed

Batch experiments were carried out to investigate the effects of initial atrazine concentrations and consecutive desorption steps on the desorption characteristics of atrazine from a sandy loam soil. As initial atrazine concentration increased, the average percentage of atrazine desorption on the sandy loam soil ranged gradually from 23.1% to 38.5% after five consecutive desorption steps. The values of the Freundlich capacity parameter, k(des), derived from the initial concentration and time-dependent desorption isotherm were consistently higher than those associated with sorption. The opposite trend was observed only for the values of nonlinear parameter, n(des), from the initial concentration-dependent desorption isotherms. Atrazine hydrolysis to hydroxyatrazine and bound residue formation were mainly responsible for the observed hysteresis in its sorption and desorption isotherms. For the initial concentration-dependent desorption isotherms, as initial atrazine concentration increased, the values of hysteretic coefficients omega and lamda decreased, and eta values increased. However, the relationships between initial atrazine concentration and hysteretic coefficients were not pronounced for omega, eta, or lamda. For the time-dependent desorption isotherms, lamda and eta values increased as the atrazine desorption step proceeded. The correlation between hysteretic coefficient and desorption step was highly significant for lamda (P < 0.0001), but not for eta. PMID:21462711

Deng, Jiancai; Jiang, Xin; Hu, Weiping; Hu, Liuming

2010-01-01

290

Dynamics of the defect-mediated desorption of alkali halide surfaces  

NASA Astrophysics Data System (ADS)

Dynamic processes leading to desorption of Rb and I atoms from the RbI (100) surface co-irradiated with 1 keV electrons and visible light (with a wavelength corresponding to the F-center absorption band) have been studied by means of mass-selected time-of-flight (TOF) spectroscopy. Depending on the sample temperature, substantial enhancement of the desorption yield as well as pronounced changes in the TOF spectra of the emitted atoms have been found. The TOF spectra of halogen atoms consist of two components: the thermal (which can be fitted with Maxwellian distribution) and the non-thermal one. The non-thermal peak is temperature-independent. There is no non-thermal component for alkali atoms. The comparison of TOF spectra for I atoms emitted from electron bombarded sample with and without simultaneous light irradiation indicates that the yield increase is caused by thermally desorbed atoms, while the non-thermal peak remains unchanged. Presented results confirm well the predictions of the theoretical model of desorption proposed earlier, known as the defect-mediated (F and H center) desorption of alkali halide.

Szymonski, M.; Droba, A.; Struski, P.; Krok, F.

2012-08-01

291

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

292

Sample Desorption/Onization From Mesoporous Silica  

DOEpatents

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.

Iyer, Srinivas (Los Alamos, NM); Dattelbaum, Andrew M. (Los Alamos, NM)

2005-10-25

293

Dicamba adsorption–desorption on organoclays  

Microsoft Academic Search

The adsorption–desorption of the herbicide dicamba (pKa=1.9, water solubility, 6.5 g kg?1) by organoclays (OCls) was studied at different concentrations and pH levels. Two smectites (SAz and SWy), varying in surface properties, were reacted with amounts of different alkylammonium cations [octadecyl(C18)-, hexadecyl-trimethyl(HDT)- and dioctadecyldimethyl(DOD)ammonium] equal to 50% or 100% of the clays' CEC. Adsorption isotherms of dicamba on diverse OCl

M. J. Carrizosa; W. C. Koskinen; M. C. Hermosin; J. Cornejo

2001-01-01

294

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

SciTech Connect

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.

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

1999-05-01

295

Effects of relative humidity on chloroacetanilide and dinitroaniline herbicide desorption from agricultural PM2.5 on quartz fiber filters.  

PubMed

This study quantified the release of seven relatively polar preemergence herbicides to the gas phase from soil-generated PM2.5-loaded quartz fiber filters (QFFs) and bare QFF as a function of relative humidity (RH). A 48-hour desorption fraction, F48, was defined to evaluate the relative desorption behavior of herbicides from two families, chloroacetanilide (alachlor, butachlor, metolachlor, and propachlor) and dinitroaniline (pendimethalin, prodiamine, and trifluralin) using temperature- (8 degrees C) and humidity- (10-64% RH) controlled air at a flow rate of 4 L/min. With increasing RH, an increase in F48 by a factor of 2-8 was observed for all herbicides, except metolachlor and butachlor, which showed significantly strong sorption to both sorbents. The conjugate carbonyl oxygen and amide nitrogen in the chloroacetanilide structure enables stronger specific interactions with the sorbents, leading to lower desorption compared to the dinitroaniline herbicides. Desorption of chloroacetanilides decreased in the order propachlor > alachlor > metolachlor approximately butachlor, and desorption of dinitroanilines decreased in the order trifluralin > pendimethalin > prodiamine. These orders are consistent with the different substituents in the herbicide molecules for each family and their relative tendencies to coordinate with surface moieties as indicated by electron-donating capacity. Henry's law constant and Abraham's H-acceptor parameter were found to be useful empirical parameters for describing the F48 desorption behavior for all seven herbicides. PMID:17612158

Yang, Wenli; Holmén, Britt A

2007-06-01

296

Kinetics of CO and CO 2Evolution During the Temperature-Programmed Oxidation of Coke Deposited on Cracking Catalysts  

Microsoft Academic Search

The reaction kinetics of evolved carbon monoxide and carbon dioxide during the temperature programmed oxidation (TPO) of an industrially spent fluid cracking catalyst have been investigated. Two pathways to CO and two to CO2evolution, all involving either undissociated or dissociated surface oxide complexes, were assumed. Rate coefficient parameters and O2reaction orders were then optimized to simulate the TPO profiles recorded

Chao'en Li; Cam Le Minh; Trevor C. Brown

1998-01-01

297

Temperature  

NSDL National Science Digital Library

This article discusses the relationship between temperature and heat and kinetic energy and it shows how to convert from degrees Fahrenheit to Centigrade. It also includes links to other resources, data, maps, and classroom activities.

2008-04-08

298

Measurements and analysis of water adsorption and desorption  

SciTech Connect

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.

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

1996-02-01

299

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

PubMed

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. PMID:20088248

Zweiben, Cindy; Shaw, Arthur J

300

Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets.  

PubMed

This study investigated the desorption behavior of polychlorinated biphenyls (PCBs) from marine plastic pellets. Long-term desorption experiments were conducted using field-collected polyethylene (PE) pellets. The results indicate that the desorption kinetics highly depends on the PE-water partition coefficients of PCB congeners. After 128d of the experiment, the smallest congener considered (CB 8) had desorbed nearly completely (98%), whereas major fractions (90-99%) of highly chlorinated congeners remained in the pellets. An intraparticle diffusion model mostly failed to reproduce the desorption kinetics, whereas an aqueous boundary layer (ABL) diffusion model well approximated the data. The desorption half-lives are estimated to 14d to 210years for CB 8 to CB 209 in an actively stirred solution (ABL thickness: 30?m). Addition of methanol to water enhanced the desorption to a large extent. A need for further work to explore roles of organic matter in facilitating solute transfer is suggested. PMID:23906473

Endo, Satoshi; Yuyama, Masaki; Takada, Hideshige

2013-07-29

301

Desorption by phonon cascades for gas-solid systems with many physisorbed surface bound states  

NASA Astrophysics Data System (ADS)

We give the extension of our quantum-statistical theory of desorption for systems with many physisorbed bound states in the surface potential. Rate equations are set up and the desorption time td is properly identified as the smallest eigenvalue of the matrix of transition probabilities. The latter are calculated exactly in second-order perturbation theory for a surface Morse potential. We show that desorption in weakly coupled systems with many bound states proceeds predominantly through one-phonon cascades. Two-phonon contributions are shown to be small. Desorption times are calculated for the He-LiF, He-NaF, He-graphite, H-NaCl, He-Ar, and Xe-W systems. The temperature regime over which a Frenkel-Arrhenius parametrization td=t0dexp(QkBT) can be invoked is given. Our theory which is essentially parameter-free produces prefactors t0d in the whole experimental range of physisorption from 10-7 to 10-14 sec.

Gortel, Z. W.; Kreuzer, H. J.; Teshima, R.

1980-12-01

302

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

303

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

PubMed

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. PMID:23944439

Buendía, G M; Rikvold, P A

2013-07-25

304

Analysis and Computer Program for Temperature Distribution in a Hollow Cylindrical Ceramic Transducer Element.  

National Technical Information Service (NTIS)

The problem of temperature distribution in a hollow cylindrical ceramic element in a sonar transducer under operating conditions is analyzed using the appropriate Green's function. The boundary conditions are taken to be (1) prescribed temperatures over t...

R. W. Dunham

1970-01-01

305

Sequential competitive sorption and desorption of chlorophenols in organoclay  

Microsoft Academic Search

Single- and bi-solute sorption and desorption of 2-chlorophenol (2-CP) and 2,4,5-trichlorophenol (2,4,5-TCP) in montmorillonite\\u000a modified with hexadecyltrimethyl-ammonium (HDTMA) were investigated by sequential sorption and desorption. Effect of pH on\\u000a the sequential sorption and desorption was investigated. As expected by the magnitude of octanol: water partition coefficient\\u000a (Kow), both sorption and desorption affinity of 2,4,5-TCP was higher than that of 2-CP

Ji-Hoon Kim; Won Sik Shin; Dong-Ik Song; Sang June Choi

2006-01-01

306

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

NASA Astrophysics Data System (ADS)

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.

Fergason, J. L.

1980-08-01

307

Adsorption thermodynamic, kinetic and desorption studies of Pb 2+ on carbon nanotubes  

Microsoft Academic Search

Adsorption thermodynamics of Pb2+ on carbon nanotubes has been studied at various temperatures of 280, 298 and 321K and the thermodynamic parameters, such as equilibrium constant (K0), standard free energy changes (?G0), standard enthalpy change (?H0) and standard entropy change (?S0), have been obtained. A pseudo-second-order rate model has been employed to describe the kinetic adsorption processes. Desorption studies reveal

Yan-Hui Li; Zechao Di; Jun Ding; Dehai Wu; Zhaokun Luan; Yanqiu Zhu

2005-01-01

308

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD)  

Microsoft Academic Search

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD) by heating with hydrogen at 3: 200°C converted the acid to gas-phase sulfur dioxide with a significant loss of the acid to hydrogen sulfide and elemental sulfur. These side reactions were suppressed and the temperature required for SOâ recovery was reduced by impregnating the charcoal

S. Yoshizawa; A. Karagiri; K. Watanabe

1979-01-01

309

Measurement and modeling of the transient adsorption, desorption and diffusion processes in microporous materials  

Microsoft Academic Search

Using pulse-response experiments the adsorption and diffusion behavior of a number of gases in microporous materials was measured in the temperature range 300–773K. By modeling these pulse responses it is possible to simultaneously determine the equilibrium constant for adsorption, the absolute rate constants for adsorption and desorption, as well as the diffusivity inside micropores. The pulse-response measurements are very reproducible

T. A. Nijhuis; L. J. P. van den Broeke; M. J. G. Linders; J. M. van de Graaf; F. Kapteijn; M. Makkee; J. A. Moulijn

1999-01-01

310

Thermal desorption and IR spectrometric investigation of polyamorphic and polymorphic transformations in cryovacuum condensates of water  

Microsoft Academic Search

Simultaneous thermal desorption and IR spectrometric studies of thermally stimulated transformations in thin films of cryovacuum condensates of water are carried out. It is shown that the temperature interval 12-36 K is the existence region of a high-density form of amorphous solid water. The transition of amorphous high-density ice to a low-density amorphous state starts at T~39 K and is

A. Drobyshev; A. Aldiyarov; D. Zhumagaliuly; V. Kurnosov; N. Tokmoldin

2007-01-01

311

Enhancement of phosphate desorption by silicate in soils with salt accumulation  

Microsoft Academic Search

To increase phosphate availability in plastic film house soils with salt accumulation, silicate was applied to silt loam (SiL, T-P 3,980 mg kg) and loam (L, T-P 5,560 mg kg) soils, and the effects of silicate on phosphate desorption were investigated under the different conditions; temperature: 10, 20, and 35°C, Si concentration: 0-2 mmol L, and pH 2-12. Silicate efficiency

Yang Bok Lee; Chang Hoon; Joan Young Hwang; In Bok Lee; Pil Joo Kim

2004-01-01

312

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

Microsoft Academic Search

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

S Lahsasni; M Kouhila; M Mahrouz; N Kechaou

2002-01-01

313

Manganese oxide nanoparticle-assisted laser desorption\\/ionization mass spectrometry for medical applications  

Microsoft Academic Search

We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm) and developed nanoparticle-assited laser desorption\\/ionization (nano-PALDI) mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m\\/z. The

Shu Taira; Kenji Kitajima; Hikaru Katayanagi; Eiichiro Ichiishi; Yuko Ichiyanagi

2009-01-01

314

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

SciTech Connect

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

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

2005-03-15

315

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

USGS Publications Warehouse

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.

Delaney, P. T.

1988-01-01

316

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

SciTech Connect

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

Zaczek, M.; /Fermilab

1997-08-11

317

DESORPTION OF ETHYL ACETATE-WATER MIXTURE BY USING CROSS-LINKED POLY(VINYLALCOHOL) MEMBRANE AND COMPARISON OF RESULTS WITH PERVAPORATION  

Microsoft Academic Search

In this study using poly(vinylalcohol) (PVOH) membranes cross-linked with tartaric acid (Tac) desorption experiments were performed for selected concentrations of binary ethyl acetate (EtAc)-water mixture at temperatures of 30°, 40°, and 50°C to determine sorption of components. Sorption values measured were compared with those estimated by the Flory-Huggins approach. Additionally, desorption results were compared with pervaporation results of another study

Sevinc Korkmaz; Yavuz Salt; Ayca Hasanoglu; Semra Ozkan; Salih Dincer

2008-01-01

318

Temperature-programmed reduction and cyclic voltammetry of Pt\\/carbon-fibre paper catalysts for methanol electrooxidation  

Microsoft Academic Search

Temperature-programmed reduction (TPR) and cyclic voltammetry (CV) studies of platinum catalysts supported on pyrographite-coated carbon-fibre paper, and prepared by either ion exchange or impregnation, clearly demonstrate the nature of the interactions between the platinum species and the support. After drying the above catalysts at 120°C, the ion-exchanged preparation exhibits the stronger interaction with the carbon support, as might be expected

P. A. Attwood; B. D. McNicol; R. T. Short

1981-01-01

319

Prediction of retention times in temperature programmed gas chromatography using the retention equation derived from crystallization behavior of polymer.  

PubMed

Based on the enlightenment from the crystallization behavior of polymer, a novel retention equation constructed with only three pairs of isothermal retention data was proposed to predict retention times in temperature programmed gas chromatography (TPGC). The new retention equation worked beautifully in both the single- and the multiple-ramp temperature-programmed modes, yielding the average absolute relative errors of 0.65% for single-ramp TPGC across all the 18 analytes in 3 temperature programmed experiments and 0.30% for multiple-ramp TPGC across all the 8 analytes in 6 temperature programmed experiments tested in this work. Moreover, to compare with the new retention equation systematically and thoroughly, another 13 retention equations determined by two or three parameters were derived from a universal formula lnk=a?+a?/T+a?/T²+a? lnT+a?T+a?T² as a combination of the relationships between lnk and T with reference to four widely used retention equations in publications. Calculated by these 14 retention equations with the same experimental data, the absolute relative errors of prediction retention times for single-ramp TPGC mode were compared by means of statistical analysis. At a very high significance level of 1%, statistical evidences of paired t-test strictly implied that the new retention equation yielded the best prediction results among all of the 14 retention equations. In addition, remarkably, among the 13 retention equations, three seldom used in publications retention equations also worked nicely, yielding satisfactory average absolute relative errors of 0.78%, 0.81% and 0.84% for single-ramp TPGC. PMID:23332784

Li, Xiaowei; Fan, Guoliang; Gong, Cairong; Ao, Min; Li, Hua

2012-12-31

320

Study of the Preparation of Bulk Powder Tungsten Carbides by Temperature Programmed Reaction with CH 4+ H 2Mixtures  

Microsoft Academic Search

The synthesis of bulk tungsten carbides by carburization of W metal or of WO3with mixtures of CH4in hydrogen at various pressures has been studied in temperature programmed experiments. The resulting solids have been characterized by elemental analysis, X-ray diffraction, XPS analysis, and specific surface area measurements. The carburization occurs in two distinct steps: W2C is formed in the first step

G. Leclercq; M. Kamal; J. M. Giraudon; P. Devassine; L. Feigenbaum; L. Leclercq; A. Frennet; J. M. Bastin; A. Löfberg; S. Decker; M. Dufour

1996-01-01

321

Cocoa butter and confectionery fats. Studies using programmed temperature X-ray diffraction and differential scanning calorimetry  

Microsoft Academic Search

The polymorphic behavior and thermal properties of cocoa butter have been investigated by means of programmed temperature\\u000a x-ray diffraction and differential scanning calorimetry. The relationship of this polymorphism to the technical problems of\\u000a “tempering” and “bloom” development is discussed. Cocoa butter containing, respectively, milk fat and a bloom inhibitor, and\\u000a some alternatives to cocoa butter have been studied. These results

G. M. Chapman; E. E. Akehurst; W. B. Wright

1971-01-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

323

Evaluation of the asphalt pavement at low temperature using asphalt thermal stress program  

Microsoft Academic Search

Though most of cracks contribute to the temperature stress of surface course itself, temperature shrinkage action of semi-rigid base course can not be ignored. So this article researches several aspects as followed: Summarize the control method commonly used at home and abroad now. In comparison, the stiffness modulus of asphalt concrete determined is also the key factor to ascertain the

Li Yongju; Huang Yuqi; Li Boyuan; Dai Wenting

2011-01-01

324

Laser Desorption and Ionization Mass Spectrometry Using PlasmonicSubstrates  

NASA Astrophysics Data System (ADS)

This chapter describes the use of plasmonic substrates for the laser desorption/ionization in mass spectrometry. Interesting phenomenon such as polarization and wavelength dependence has been observed for the laserdesorption/ionization of molecules from gold-coated porous silicon, goldnanorod arrays, and nanoparticles, and these results suggest the presence of near-field effects on the desorption/ionization process.

Chen, Lee Chuin; Hori, Hirokazu; Hiraoka, Kenzo

325

Laser desorption mass spectrometry for DNA analysis and sequencing.  

National Technical Information Service (NTIS)

Laser desorption mass spectrometry has been considered as a potential new method for fast DNA sequencing. Our approach is to use matrix-assisted laser desorption to produce parent ions of DNA segments and a time-of-flight mass spectrometer to identify the...

C. H. Chen N. I. Taranenko K. Tang S. L. Allman

1995-01-01

326

Kinetics of hydrogen desorption from the powders of metal hydrides  

Microsoft Academic Search

Desorption of hydrogen from the powders of metal hydrides (MH) is affected by several interplaying processes including hydrogen desorption from and recombination on the metal surface, diffusion within the bulk metal and different hydride phases, and decomposition of the hydride phase. In present work, possible mechanisms of hydrogen release from the MH are proposed and discussed. Analytical models are developed

I. E. Gabis; A. P. Voit; E. A. Evard; Yu. V. Zaika; I. A. Chernov; V. A. Yartys

2005-01-01

327

Modeling Soluble Phosphorus Desorption Kinetics in Tile Drainage  

Microsoft Academic Search

This paper describes a simple model for the desorption and transport of soluble reactive phos- phorus (SRP) to subsurface drains. The model assumes first-order kinetically rate-limited desorption in a soil surface mixing layer over a soil profile layer that rests on an underlying, shallow restricting layer. Input data include precipitation, soil hydraulic properties, drain outflow, free water surface fluctuation, sorbed

Christopher A. Scott; Kirk W. Weiler

2001-01-01

328

Desorption of pentachlorophenol from soils using mixed solvents  

SciTech Connect

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.

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

1999-12-15

329

Hydrogen desorption and adsorption measurements on graphite nanofibers  

Microsoft Academic Search

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. The nanofibers were grown by passing ethylene and H2 gases over the catalysts at 600 °C. Hydrogen desorption and adsorption were measured using a volumetric analysis Sieverts'

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

1998-01-01

330

Effects of SWNT and Metallic Catalyst on Hydrogen Absorption\\/Desorption Performance of MgH 2  

Microsoft Academic Search

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

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

2005-01-01

331

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

National Technical Information Service (NTIS)

Newer materials and products are being constantly added to the Army's inventory. Cold regions climatic conditions should not impair the reliability and durability of these new systems. This report discusses the rationale of the test program being undertak...

P. K. Dutta

1988-01-01

332

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

SciTech Connect

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

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

2000-05-01

333

Charge Assisted Laser Desorption/Ionization Mass Spectrometry of Droplets  

PubMed Central

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

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

2008-01-01

334

[Water sorption and desorption on experimental composite resins].  

PubMed

The water sorption and desorption, and the diffusion coefficients of the water sorption and desorption were studied on the experimental composite resins with various filler contents in both chemically-cured and light-cured type. As the filler content increased, the rate of the water sorption and desorption on the composites decreased. And these properties associated with the prediction obtained from the law of mixture. The filler did not absorb water, so the effect of the filler content on the diffusion coefficients of the water sorption was to be associated with of the law of mixture. However, in the diffusion coefficients of the water desorption the effect of filler content could not be proved to be associated with the law of mixture. The diffusion coefficients of the water desorption were over 2 times larger than the those of the water sorption. PMID:2135552

Hirano, S; Hirasawa, T

1990-11-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

336

Chemisorption and reaction of NO and N{sub 2}O on oxidized and reduced ceria surfaces studied by soft X-ray photoemission spectroscopy and desorption spectroscopy  

SciTech Connect

The authors have examined the chemisorption and reaction of NO and N{sub 2}O on ceria surfaces by soft X-ray photoelectron spectroscopy (SXPS), X-ray absorption spectroscopy, and isothermal and temperature programmed desorption (TPD) spectroscopy. Samples include highly oriented CeO{sub 2}(100) and CeO{sup 2}(111) thin films with surfaces of variable oxidation states. CeO{sub 2}(111) thin films were grown in situ allowing control over the initial oxidation state of the ceria surface, quantitatively determinedly by valence band, Ce 4d, and Ce 3d photoemission. Following NO exposure, various N-containing surface species were observed by N 1s photoemission, and the distribution of these species depended upon surface oxidation state, exposure, and adsorption temperature. These species included N{sub 2}O, nitrite, NO{sup {minus}}, and three states believed to be associated with atomic or anionic forms of N. Nitrite and N{sub 2}O are seen on a fully oxidized surface while NO{sup {minus}}, N{sub 2}O, and dissociation products are observed on a reduced surface. The primary reaction of NO with reduced ceria is reoxidation of the ceria by the NO, both by NO{sup {minus}} formation and by NO dissociation, leading to immediate and thermally induced N{sub 2} desorption. Adsorption of NO at 150 K is predominantly molecular while exposure to NO at 400 K leads to a thermally activated nitride which desorbs at temperatures above 500 K. Dissociative adsorption of NO leads to the displacement of N{sup 3{minus}} at high exposures.

Overbury, S.H.; Mullins, D.R.; Huntley, D.R.; Kundakovic, L. [Oak Ridge National Lab., TN (United States)

1999-09-10

337

Time-dependent studies of metal retention to and desorption from nanoparticle aggregates  

NASA Astrophysics Data System (ADS)

Nanoparticles play a potentially significant role in the mobility of aqueous metal species in a number of environmental systems through the sorption of metals onto their surfaces. Additionally, the natural and often rapid aggregation of nanosized particles in aqueous systems can lead to changes in their structure, available surface area, porosity, and reactivity that may modify the mechanisms and extents by which metal ions are retained. Such aggregation processes may subsequently facilitate the long-term sequestration of metals by inhibiting desorption from the nanoparticle aggregates, thus enhancing the removal of metals from solution into the solid phase. Real-time macroscopic adsorption/desorption batch experiments were conducted with synthetic iron oxyhydroxide nanoparticles to investigate changes in Cu(II) concentration under environmentally-relevant conditions. Nanoparticles were introduced into Cu(II)-bearing solutions as either monodispersed particles (initial size: ~5 nm) or multi-particle aggregates formed by increasing the pH, ionic strength, or temperature of the initial monodisperse suspensions. Ion-selective, conductivity, temperature and pH probes were used to track real time changes in the solution, specifically the uptake of Cu(II) and associated changes in pH and ionic strength. A desorption step was then performed by lowering the pH back below the macroscopic absorption edge previously determined for Cu(II) to the iron oxyhydroxide nanoparticles. Sufficient time was allowed after both the introduction of the nanoparticles and the desorption step for the system to reattain equilibrium. Results suggest that the various aggregation mechanisms influence the extent and timeframe of Cu(II) uptake and desorption differently depending on the degree of aggregation. Specifically, heating as a method of aggregation was the most effective at retaining metals in the solid phase and pH-based aggregation less so, while ionic strength-based aggregation had little effect relative to the monodisperse particles. These results agree with corresponding EXAFS studies of nanoparticle aggregates which indicate that the desorption step removes the weakly-held (i.e. surface-bound) metal fraction but retains strongly-held metals that appear to be more structurally incorporated within the nanoparticle aggregates. These findings have implications for the removal of hazardous metals from the aqueous phase and the design of remediation strategies targeting contaminated environments such as mine-impacted regions.

Kim, C. S.; Stegemeier, J. P.; Dale, J.; Gilbert, B.

2008-12-01

338

The role of electron-stimulated desorption in focused electron beam induced deposition  

PubMed Central

Summary We present the results of our study about the deposition rate of focused electron beam induced processing (FEBIP) as a function of the substrate temperature with the substrate being an electron-transparent amorphous carbon membrane. When W(CO)6 is used as a precursor it is observed that the growth rate is lower at higher substrate temperatures. From Arrhenius plots we calculated the activation energy for desorption, E des, of W(CO)6. We found an average value for E des of 20.3 kJ or 0.21 eV, which is 2.5–3.0 times lower than literature values. This difference between estimates for E des from FEBIP experiments compared to literature values is consistent with earlier findings by other authors. The discrepancy is attributed to electron-stimulated desorption, which is known to occur during electron irradiation. The data suggest that, of the W(CO)6 molecules that are affected by the electron irradiation, the majority desorbs from the surface rather than dissociates to contribute to the deposit. It is important to take this into account during FEBIP experiments, for instance when determining fundamental process parameters such as the activation energy for desorption.

Hansen, Thomas W; Wagner, Jakob B; De Hosson, Jeff T M

2013-01-01

339

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

PubMed

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

Staymates, Matthew; Gillen, Greg

2012-07-01

340

High-speed thermo-microscope for imaging thermal desorption phenomena  

NASA Astrophysics Data System (ADS)

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

Staymates, Matthew; Gillen, Greg

2012-07-01

341

The role of electron-stimulated desorption in focused electron beam induced deposition.  

PubMed

We present the results of our study about the deposition rate of focused electron beam induced processing (FEBIP) as a function of the substrate temperature with the substrate being an electron-transparent amorphous carbon membrane. When W(CO)6 is used as a precursor it is observed that the growth rate is lower at higher substrate temperatures. From Arrhenius plots we calculated the activation energy for desorption, E des, of W(CO)6. We found an average value for E des of 20.3 kJ or 0.21 eV, which is 2.5-3.0 times lower than literature values. This difference between estimates for E des from FEBIP experiments compared to literature values is consistent with earlier findings by other authors. The discrepancy is attributed to electron-stimulated desorption, which is known to occur during electron irradiation. The data suggest that, of the W(CO)6 molecules that are affected by the electron irradiation, the majority desorbs from the surface rather than dissociates to contribute to the deposit. It is important to take this into account during FEBIP experiments, for instance when determining fundamental process parameters such as the activation energy for desorption. PMID:24062973

van Dorp, Willem F; Hansen, Thomas W; Wagner, Jakob B; De Hosson, Jeff T M

2013-08-14

342

Coincidence experiments in desorption mass spectrometry  

NASA Astrophysics Data System (ADS)

The detection of coincidental signals can enhance the amount of information available in desorption time-of-flight mass spectrometry (TOF-MS) by identifying physical, chemical and/or spatial correlations between secondary ions. Detection of coincidental emissions requires that the target surface be bombarded with individual primary ions (keV or MeV), each resolved in time and space. This paper will discuss the application of coincidence counting to TOF-MS to: extract the secondary ion mass spectrum and secondary ion yields from an organic target produced by a single primary ion type when multiple primary ions simultaneously impact the sample; examine the metastable dissociation pathways and decay fractions of organic secondary ions using an ion-neutral correlation method; and study the chemical microhomogeneity (on the sub-?m scale) of a surface composed of two chemically distinct species.

Diehnelt, C. W.; English, R. D.; van Stipdonk, M. J.; Schweikert, E. A.

2002-06-01

343

Integrated field emission array for ion desorption  

DOEpatents

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.

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

2013-09-17

344

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

EPA Science Inventory

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

345

Present status of high-temperature Engineering Test Reactor (HTTR) program  

Microsoft Academic Search

The 30MWt HTTR is a high-temperature gas-cooled reactor(HTGR), with a maximum helium coolant temperature of 950°C at the reactor outlet. The construction of the HTTR started in March 1991, with first criticality to be followed in 1998 after commissioning testing. At present the HTTR reactor building and its containment vessel have been almost completed and its main components, such as

T. Tanaka; O. Baba; S. Shiozawa

1994-01-01

346

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

SciTech Connect

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.

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

2011-07-05

347

The thermal desorption of CO2 from amine carbamate solutions for the 13C isotope enrichment  

NASA Astrophysics Data System (ADS)

The CO2 desorption from amine carbamate in non-aqueous solvents is of major importance for isotopic enrichment of 13C. A series of experiments were carried out in order to set up the conditions for the CO2 desorption. For this purpose, a laboratory- scale plant for 13C isotope separation by chemical exchange between CO2 and amine carbamate was designed and used. The decomposition of the carbamate solution was mostly produced in the desorber and completed in the boiler. Two different-length desorbers were used, at different temperatures and liquid flow rates of the amine-non-aqueous solvent solutions. The residual CO2 was determined by using volumetric and gaschromatographic methods. These results can be used for enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvents.

Dronca, S.; Varodi, C.; Gligan, M.; Stoia, V.; Baldea, A.; Hodor, I.

2012-02-01

348

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

SciTech Connect

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

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

1983-06-01

349

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

PubMed

The kinetics of CO(2) adsorption and desorption over amine-functionalized mesoporous silica were investigated using silicon microcantilever arrays. Three types of mesoporous silica with different pore sizes were synthesized and functionalized with a variety of amine molecules. After depositing the silica sorbents onto the free end of each cantilever in an array, mass changes due to the adsorption and desorption of CO(2) were determined in situ with picogram sensitivity by measuring variations in the cantilever frequencies. The adsorption and desorption kinetics were found to be diffusion-controlled, and the kinetics were accelerated by increasing the temperature and pore size. The activation energies for adsorption and desorption of CO(2) were determined from Arrhenius plots. PMID:21671677

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

2011-06-15

350

ZrO 2 promoted with sulfate, iron and manganese: a solid superacid catalyst capable of low temperature n -butane isomerization  

Microsoft Academic Search

A sulfated oxide of zirconium, iron and manganese is prepared and shown to isomerizen-butane to isobutane at 35°C with rates approximately 2–3 orders of magnitude greater than sulfated zirconia as claimed by workers at Sun Refining and Marketing Company. Temperature programmed desorption of benzene is used to investigate the acidity of this remarkable catalyst. Adsorbed benzene is oxidized to CO2

Anup Jatia; Clark Chang; Jason D. MacLeod; Tatsuya Okubo; Mark E. Davis

1994-01-01

351

Influence of the rare earth element substitution on oxygen adsorption-desorption properties of YBCO  

Microsoft Academic Search

The oxygen adsorption-desorption properties of RBa2Cu3O7??\\u000a (R = Gd, Er, Eu, Dy, Sm, Ho and Nd) and Y1?x\\u000a LaxBa2Cu3O7??\\u000a (x=0.1, 0.5 and 1.0) were investigated from room temperature to 950 C by thermogravimetry (TG). The results show that all samples\\u000a will release oxygen with the increasing of temperature and the released oxygen can be absorbed back into the sample when

Yu-Shan Fan; Hong-Zhang Song; Zhi-Hui Li; De-Lin Yang; Xing Hu

2006-01-01

352

COMPF2 - A Program for Calculating Post-Flashover Fire Temperatures.  

National Technical Information Service (NTIS)

COMPF2 is a computer program for calculating the characteristics of a post-flashover fire in a single building compartment, based on fire-induced ventilation through a single door or window. It is intended both for performing design calculations and for t...

V. Babrauskas

1979-01-01

353

PATHFINDER ATOMIC POWER PLANT SUPERHEATER TEMPERATURE EVALUATION ROUTINE. AN IBM704 COMPUTER PROGRAM  

Microsoft Academic Search

A computer program was written for analysis of steam flow and heat ; transfer in fuel elements consisting of concentric fuel tubes with several ; annular coolant-flow channels. Performance of both average and hot-channel fuel ; elements may be evaluated since, for any heat generation rate, either total ; coolant flow rate or over-all pressure drop may be specified. The

1961-01-01

354

More realistic soil cleanup standards with dual-equilibrium desorption.  

PubMed

The desorption of contaminants from soils/sediments is one of the most important processes controlling contaminant transport and environmental risks. None of the currently adopted desorption models can accurately quantify desorption at relatively low concentrations; these models often overestimate the desorption and thus the risks of hydrophobic organic chemicals, such as benzene and chlorinated solvents. In reality, desorption is generally found to be biphasic, with two soil-phase compartments. A new dual-equilibrium desorption (DED) model has been developed to account for the biphasic desorption. This model has been tested using a wide range of laboratory and field data and has been used to explain key observations related to underground storage tank plumes. The DED model relates the amount of a chemical sorbed to the aqueous concentration, with simple parameters including octanol-water partition coefficient, solubility, and fractional organic carbon; thus, it is the only biphasic model, to date, that is based on readily available parameters. The DED model can be easily incorporated into standard risk and transport models. According to this model, many regulatory standards of soils and sediments could be increased without increasing the risks. PMID:11916120

Chen, W; Kan, A T; Newell, C J; Moore, E; Tomson, M B

355

Glass transition induced by solvent desorption for statistical MMA\\/nBMA copolymers — Influence of copolymer composition  

Microsoft Academic Search

An experimental study of the glass transition induced by solvent desorption has been performed for a series of Methyl methacrylate (MMA)\\/n-butyl methacrylate (nBMA) statistical copolymer films. The glass transition temperature of the dry homopolymers, PMMA and PnBMA, are, respectively, about 105 and 78C above the temperature of the experiment, so that the glass transition domain can be analyzed in detail

A.-C. Saby-Dubreuila; B. Guerrier; C. Allain; D. Johannsmannb

356

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

Microsoft Academic Search

Insulation systems will be a key element in the future construction and impregnation of the coils for the ITER device. The thermal contraction and thermal conductivity of ten different electrical insulation systems are measured at temperatures from 4 K to 300 K. Several insulation systems incorporate an electrical barrier layer. The insulation systems are all based on identical S2-glass with

A. J. Broadbent; J. Crozier; K. D. Smith

1997-01-01

357

EPA AND ERDA HIGH-TEMPERATURE/HIGH-PRESSURE PARTICULATE CONTROL PROGRAMS  

EPA Science Inventory

The report describes and compares current projects sponsored by EPA and the U.S. Energy Research and Development Administration (ERDA), relating to the control of particulate matter in fuel gas streams at high temperatures (1000 to 2000F) and high pressures (5 atm and greater). T...

358

Assessment of the high temperature fission chamber technology for the French fast reactor program  

SciTech Connect

High temperature fission chambers are key instruments for the control and protection of the sodium-cooled fast reactor. First, the developments of those neutron detectors, which are carried out either in France or abroad are reviewed. Second, the French realizations are assessed with the use of the technology readiness levels in order to identify tracks of improvement. (authors)

Jammes, C.; Filliatre, P.; Geslot, B.; Domenech, T.; Normand, S. [Commissariat a l'Energie Atomique, CEA (France)

2011-07-01

359

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

SciTech Connect

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.

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

1996-07-01

360

Summary Report on FY12 Small-Scale Test Activities High Temperature Electrolysis Program  

SciTech Connect

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.

James O'Brien

2012-09-01

361

NOVEL CERAMIC MEMBRANE FOR HIGH TEMPERATURE CARBON DIOXIDE SEPARATION  

SciTech Connect

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.

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

2001-09-01

362

Microchannel membrane separation applied to confined thin film desorption  

SciTech Connect

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)

Thorud, Jonathan D.; Liburdy, James A.; Pence, Deborah V. [Department of Mechanical Engineering, Oregon State University, 204 Rogers Hall, Corvallis, OR 97331 6001 (United States)

2006-08-15

363

A Time-Domain Sub-Micro Watt Temperature Sensor With Digital Set-Point Programming  

Microsoft Academic Search

To realize the on-chip temperature monitoring of VLSI circuits, an accurate time-domain low-power CMOS thermostat based on delay lines is proposed. Contrary to the voltage-domain predecessors, the proposed circuit can benefit from the performance enhancement due to the scaling down of fabrication processes. By replacing R-string voltage division and voltage comparator with delay line time division and time comparator, only

Poki Chen; Tuo-Kuang Chen; Yu-Shin Wang; Chun-Chi Chen

2009-01-01

364

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

USGS Publications Warehouse

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).

Barker, Charles E.; Dallegge, Todd A.

2005-01-01

365

Development of Designer Diamond Anvils for High Pressure-High-Temperature Experiments in Support of the Stockpile Stewardship Program  

SciTech Connect

The focus of this program at the University of Alabama at Birmingham (UAB) is to develop the next generation of designer diamond anvils that can perform simultaneous joule heating and temperature profile measurements in a diamond anvil cell. A series of tungsten-rhenium thermocouples will be fabricated onto to the anvil and encapsulated by a chemical vapor deposited diamond layer to allow for a complete temperature profile measurement across the anvil. The tip of the diamond anvil will be engineered to reduce the thermal conductivity so that the tungsten-heating coils can be deposited on top of this layer. Several different approaches will be investigated to engineer the tip of the diamond anvil for reduction in thermal conductivity (a) isotopic mixture of 12C and 13C in the diamond layer, (b) doping of diamond with impurities (nitrogen and/or boron), and (c) growing diamond in a higher concentration of methane in hydrogen plasma. Under this academic alliance with Lawrence Livermore National Laboratory (LLNL), PI and his graduate students will use the lithographic and diamond polishing facility at LLNL. This proposed next generation of designer diamond anvils will allow multi-tasking capability with the ability to measure electrical, magnetic, structural and thermal data on actinide materials with unparallel sensitivity in support of the stockpile stewardship program.

Yogesh K. Vohra

2005-05-12

366

Laser Desorption Mass Spectrometry. II. Applications to Structural Analysis.  

National Technical Information Service (NTIS)

Laser desorption mass spectrometry (LDMS) is reviewed with focus on application to structural analysis of nonvolatile organic compounds. Models for the ionization-volatilization step are discussed with reference to solid-state vs. 'gas-phase' reactions. G...

D. M. Hercules R. J. Day K. Balasanmugam T. A. Dang C. P. Li

1982-01-01

367

Molecular beam-thermal hydrogen desorption from palladium.  

PubMed

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 degrees C/min) accounts for the consistency of the technique. PMID:20441321

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

2010-04-01

368

Laser desorption mass spectrometry for biomolecule detection and its applications  

NASA Astrophysics Data System (ADS)

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. .

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

2001-08-01

369

Redox transformations in desorption electrospray ionization  

NASA Astrophysics Data System (ADS)

Redox changes occur in some circumstances when organic compounds are analyzed by desorption electrospray ionization mass spectrometry (DESI-MS). However, these processes are limited in scope and the data presented here suggest that there are only limited analogies between the redox behavior in DESI and the well-known solution-phase electrochemical processes in standard electrospray ionization (ESI). Positive and negative ion modes were both investigated and there is a striking asymmetry between the incidence of oxidation and of reduction. Although in negative ion mode DESI experiments, some aromatic compounds were ionized as odd-electron anion radicals, examples of full reduction were not found. By contrast, oxidation in the form of oxygen atom addition (or multiple oxygen atom additions) was observed for several different analytes. These oxidation reactions point to chemically rather than electrochemically controlled processes. Data is presented which suggests that oxidation is predominantly caused by reaction with discharge-created gas-phase radicals. The fact that common reducing agents and known antioxidants such as ascorbic acid are not modified, while a saturated organic acid like stearic acid is oxidized in DESI, indicates that the usual electrochemical redox reactions are not significant but that redox chemistry can be induced under special experimental conditions.

Benassi, Mario; Wu, Chunping; Nefliu, Marcela; Ifa, Demian R.; Volný, Michael; Cooks, R. Graham

2009-02-01

370

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

PubMed

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. PMID:23627526

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

2013-05-13

371

Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass.  

PubMed

This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 degrees C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO3 and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater. PMID:18053641

Gupta, V K; Rastogi, A

2007-10-13

372

Desorption of polycyclic aromatic hydrocarbons from carbon nanomaterials in water  

Microsoft Academic Search

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

Kun Yang; Baoshan Xing

2007-01-01

373

Desorption of Cadmium(II) from Artificially Contaminated Sediments  

Microsoft Academic Search

The desorption kinetics of cadmium from natural sediments was investigated. Three sediment samples from Maryland water bodies were artificially contaminated with Cd(II) and subsequently exposed to a wide range of chemical conditions in batch reactors. Dissolved Cd(II) was monitored. The highest desorption rates and extents were observed at low pH and high concentrations of CaCl2 and EDTA (a strong Cd

Alessandor Franchi; Allen P. Davis

1997-01-01

374

Sorption and desorption of arsenic from sandy soils: Column studies  

Microsoft Academic Search

Rate?limited sorption\\/desorption can have a profound effect upon the transport of sorbing contaminants. Numerical and analytical models used to predict chemical movement through the subsurface rarely incorporate the effects of nonlinear sorption and desorption kinetics, resulting in potentially large overestimates of mass extractability. Mass transfer characteristics of arsenic?contaminated soils at the site of a former arsenical herbicide manufacturer in Houston,

Paul D. Kuhlmeier

1997-01-01

375

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

SciTech Connect

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

Joseph M. Calo

2000-07-21

376

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

377

State-resolved studies of the laser-induced desorption of NO from Si(111) 7 times 7: Low coverage results  

SciTech Connect

The results of a quantum-state-resolved study of the laser-induced desorption (LID) of NO from Si(111) 7{times}7 at a surface temperature of 100 K are reported. All aspects of the LID are found to be sensitive to the initial coverage. The coverage dependence indicates that there are two desorption mechanisms, one operative at low coverages that is quenched with increasing NO exposure, and one operative at high coverage. This report characterizes the low coverage channel. Most of the energy in the desorbed NO occurs as vibration and translation, with the rotations substantially cooler. The desorption is selective for production of the ground spin--orbit state. The energy partitioning shows strikingly little change as the desorption-laser wavelength was varied from 1907 to 355 nm. This, coupled with a quantitative study of the yield over the same photon energy range and selective coadsorption experiments, establishes that the desorption is specifically due to an interaction involving photogenerated holes in the rest-atom localized, intrinsic surface state of the 7{times}7 reconstructed surface. It is suggested that the surface state hole drives the desorption by neutralization of a NO{sup {minus}{delta}} adsorbate.

Richter, L.J.; Buntin, S.A.; King, D.S.; Cavanagh, R.R. (National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States))

1992-02-01

378

Cryogenic ultra-high vacuum scanning tunneling microscopy of electron-stimulated desorption of hydrogen and deuterium from silicon  

NASA Astrophysics Data System (ADS)

A cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) has been developed. This design utilizes a novel vibration isolation scheme which provides excellent thermal coupling to a cooling source. The cooling scheme departs from other cryogenic UHV STMs where vibration isolation and cooling compete with each other. Variable temperature operation from 11 K to 300 K has been demonstrated. Future improvements will enable operation down to 1.5 K. This system has been used to perform low temperature desorption studies of hydrogen and deuterium from Si(100) surfaces. Comparing these results to previous room temperature studies indicates that there is no temperature dependence to the desorption in the high voltage field emission regime. However, in the low voltage vibrational heating regime a strong temperature dependence is observed, with the desorption yield for hydrogen at 11 K being 300 times greater than at 300 K. In the context of Avouris' vibrational heating model, these data are consistent with an increase in the Si-H vibrational lifetime from 10 ns at 300 K to 19 ns at 11 K. By similar analysis, the Si-D vibrational lifetime increases from 0.25 ns at 300 K to 0.85 ns at 11 K.

Foley, Edward Thomas

1997-12-01

379

Kinetics of desorption of organic compounds from dissolved organic matter.  

PubMed

This study presents a new experimental technique for measuring rates of desorption of organic compounds from dissolved organic matter (DOM) such as humic substances. The method is based on a fast solid-phase extraction of the freely dissolved fraction of a solute when the solution is flushed through a polymer-coated capillary. The extraction interferes with the solute-DOM sorption equilibrium and drives the desorption process. Solutes which remain sorbed to DOM pass through the extraction capillary and can be analyzed afterward. This technique allows a time resolution for the desorption kinetics from subseconds up to minutes. It is applicable to the study of interaction kinetics between a wide variety of hydrophobic solutes and polyelectrolytes. Due to its simplicity it is accessible for many environmental laboratories. The time-resolved in-tube solid-phase microextraction (TR-IT-SPME) was applied to two humic acids and a surfactant as sorbents together with pyrene, phenanthrene and 1,2-dimethylcyclohexane as solutes. The results give evidence for a two-phase desorption kinetics: a fast desorption step with a half-life of less than 1 s and a slow desorption step with a half-life of more than 1 min. For aliphatic solutes, the fast-desorbing fraction largely dominates, whereas for polycyclic aromatic hydrocarbons such as pyrene, the slowly desorbing, stronger-bound fraction is also important. PMID:22035249

Kopinke, Frank-Dieter; Ramus, Ksenia; Poerschmann, Juergen; Georgi, Anett

2011-11-10

380

Uranium and Neptunium Desorption from Yucca Mountain Alluvium  

SciTech Connect

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.

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

2006-03-16

381

Ambient analysis by thermal desorption atmospheric pressure photoionization.  

PubMed

Ambient mass spectrometry has attracted substantial attention in recent years. Among ambient ionization methods, thermal desorption ionization stands out because of two attributes: (1) simplicity, rendering the technique suitable for in-field applications, and (2) ability to couple with a variety of gas-phase ionization methods thereby broadening the range of molecules that can be analyzed with this method. Here, we report on improving the performance of a direct analysis in real time (DART) source by implementing atmospheric pressure photoionization (APPI) downstream of the desorption region. At identical desorption and ion sampling conditions, APPI leads to detection of radical molecular ions from non-polar compounds that are absent from the spectra generated by DART alone. Moreover, a factor of 3-5 improvement in sensitivity is observed using APPI for positive ions commonly detected by DART and DART-APPI. Using helium and nitrogen as desorption gases, APPI shows identical performance regardless of desorption gas type. In contrast, a dramatic decrease in sensitivity is observed for DART operated with nitrogen compared to DART with helium. Comparable performance for DART and DART-APPI are observed in negative ion mode, although both show a drastic improvement in the absence of the Vapur interface. This interface creates a differentially pumped chamber prior to inlet of the mass spectrometer and reduces the mass spectrometer gas load when helium is used as desorption gas. PMID:23180079

Jorabchi, Kaveh; Hanold, Karl; Syage, Jack

2012-11-23

382

Field electron emission and field desorption of cesium from graphene  

NASA Astrophysics Data System (ADS)

Field electron emission and field desorption of cesium ions from a monatomic graphene film on Ir and graphene clusters in amorphous carbon are investigated using field electron microscopy and continuous-mode field desorption microscopy. The deposition of cesium on amorphous carbon with graphite clusters leads to inversion of the emission (i.e., emission from the emission centers disappears against the back-ground of uniform emission from the previously nonemitting surface). In both systems, ion current pulses are observed during field desorption in a stationary electric field. During field desorption from the graphene film, current pulses of Cs+ ions with a duration shorter than 0.1 s appear from the plane faces of the iridium point. During desorption from graphite clusters, ion current pulses form a pattern of "collapsing rings" on the screen. Possible mechanisms of the observed processes are considered using the model of cesium intercalation by graphite and by the graphene layer and the desorption of Cs atoms under the action of the electric field, as well as the "flip" of the dipole moment during the cesium intercalation.

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

2013-06-01

383

Desorption of perylene from combustion, NaCl, and carbon particles  

SciTech Connect

The gas/particle distribution of perylene as a model PAH (polyaromatic hydrocarbon) is measured within a temperature range from 300 to 650 K. Perylene is adsorbed onto the core of combustion particles of different size (30- 80 nm in diameter) and origin (diesel engine and oil burner), carbon particles, and NaCl particles. The adsorbed perylene consists of a fraction x, that is nonremovable at temperatures up to 650 K and a fraction that can be desorbed at temperatures below 500 K. The mean desorption temperature T[sub 50%] (50% of perylene still in the particulate phase) and the fraction x are increasing with increasing diameter of the particles in the case of combustion particles and carbon particles. T[sub 50%] and x of the NaCl particles show no size dependence. The desorption enthalpy E[sub d] is close to the evaporation enthalpy of perylene. However, to model the experimental results by a two-step adsorption model, a distribution of E[sub d] instead of a single value has to be assumed. The results show that carbon particles may be used as a model for combustion particles when studying the adsorption of low volatile PAHs, whereas NaCl particles show considerable differences in their sorption properties. 28 refs., 11 figs., 1 tab.

Steiner, D.; Burtscher, H.K. (Lab. for Solid State Physics, Zuerich (Switzerland))

1994-07-01

384

Preparation and thermal desorption properties of dc sputtered zirconium-hydrogen-helium thin films  

SciTech Connect

We developed a new approach for preparing hydrogen and helium co-containing zirconium films (Zr-H-He) to simulate aging metal tritides. We also studied the effect of hydrogen on helium behavior, in which we applied direct current magnetron sputtering in a mixture of working gases (helium, argon, and hydrogen). The amount and depth profile of helium and hydrogen trapped in the films were determined using the elastic recoil detection analysis. The microstructure and surface morphology of the Zr-H-He films were studied by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. To investigate the effect of hydrogen on the thermal release behavior of helium in the Zr film, thermal desorption spectrometry (TDS) was used, which revealed a similar desorption behavior to aged tritides. TDS experiments showed that the spectra were constituted by low-temperature peaks around 300 deg. C and high temperature peaks above 750 deg. C. Furthermore, the solid-phase {alpha} to {delta} transformation changed the shapes of the high-temperature peaks related to microstates of helium bubbles and caused the peak with a massive helium release shift toward lower temperature obviously.

Wei, Y. C.; Shi, L. Q.; Zhang, L.; He, Z. J.; Zhang, B.; Wang, L. B. [Applied Ion Beam Physics Laboratory, Institute of Modern Physics, Fudan University, Shanghai 20043 (China); Institute of Metal Physics, Chinese Academy of Science, Shenyang 110016 (China)

2008-11-15

385

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

386

Data quality in tissue analysis using desorption electrospray ionization.  

PubMed

There has been a recent surge in applications of mass spectrometry (MS) to tissue analysis, particularly lipid-based tissue imaging using ambient ionization techniques. This recent growth highlights the need to examine the effects of sample handling, storage conditions, and experimental protocols on the quality of the data obtained. Variables such as time before freezing after organ removal, storage time at -80 °C, time stored at room temperature, heating, and freeze/thaw cycles were investigated for their effect on the data quality obtained in desorption electrospray ionization (DESI)-MS using mouse brain. In addition, analytical variables such as tissue thickness, drying times, and instrumental conditions were also examined for their impact on DESI-MS data. While no immediate changes were noted in the DESI-MS lipid profiles of the mouse brain tissue after spending 1 h at room temperature when compared to being frozen immediately following removal, minor changes were noted between the tissue samples after 7 months of storage at -80 °C. In tissue sections stored at room temperature, degradation was noted in 24 h by the appearance of fatty acid dimers, which are indicative of high fatty acid concentrations, while in contrast, those sections stored at -80 °C for 7 months showed no significant degradation. Tissue sections were also subjected to up to six freeze/thaw cycles and showed increasing degradation following each cycle. In addition, tissue pieces were subjected to 50 °C temperatures and analyzed at specific time points. In as little as 2 h, degradation was observed in the form of increased fatty acid dimer formation, indicating that enzymatic processes forming free fatty acids were still active in the tissue. We have associated these dimers with high concentrations of free fatty acids present in the tissue during DESI-MS experiments. Analytical variables such as tissue thickness and time left to dry under nitrogen were also investigated, with no change in the resulting profiles at thickness from 10 to 25 ?m and with optimal signal obtained after just 20 min in the dessicator. Experimental conditions such as source parameters, spray solvents, and sample surfaces are all shown to impact the quality of the data. Inter-section (relative standard deviation (%RSD), 0.44-7.2%) and intra-sample (%RSD, 4.0-8.0%) reproducibility data show the high quality information DESI-MS provides. Overall, the many variables investigated here showed DESI-MS to be a robust technique, with sample storage conditions having the most effect on the data obtained, and with unacceptable sample degradation occurring during room temperature storage. PMID:21789488

Dill, Allison L; Eberlin, Livia S; Costa, Anthony B; Ifa, Demian R; Cooks, R Graham

2011-07-26

387

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

NASA Astrophysics Data System (ADS)

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

Sasaki, Masahiro; Yoshida, Seikoh; Yamada, Chikashi

1993-10-01

388

Temperature-Programmed Reduction and XRD Studies of the Interactions in Supported Rhodium Catalysts and Their Effect on Partial Oxidation of Methane to Synthesis Gas  

Microsoft Academic Search

In the present paper, comprehensive temperature-programmed reduction and X-ray diffraction studies were conducted, with particular emphasis on the effect of calcination temperature on the interactions between rhodium oxide and support. The formation of a compound between rhodium and support oxide is strongly dependent on the nature of the support and the calcination temperature. No such compounds were formed over ?-Al2O3

E. Ruckenstein; H. Y. Wang

2000-01-01

389

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

PubMed

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. PMID:18302353

Liu, Yongchun; He, Hong; Ma, Qingxin

2008-02-27

390

Improving low temperature properties of synthetic diesel fuels derived from oil shale. Alternative fuels utilization program  

SciTech Connect

The ability of additives to improve the cold flow properties of shale oil derived fuels boiling in the diesel fuel range was evaluated. Because a commercial shale oil industry did not exist to provide actual samples of finished fuels, a representative range of hydroprocessed shale oil fractions was prepared for use in the additive testing work. Crude oil shale from Occidental Shale Company was fractionated to give three liquids in the diesel fuel boiling range. The initial boiling point in each case was 325/sup 0/F (163/sup 0/C). The final boiling points were 640/sup 0/F (338/sup 0/C), 670/sup 0/F (354/sup 0/C) and 700/sup 0/F (371/sup 0/F). Each fraction was hydrotreated to three different severities (800, 1200 and 1500 psi total pressure) over a Shell 324 nickel molybdate on alumina catalyst at 710 to 750/sup 0/F to afford 9 different model fuels. A variety of commercial and experimental additives were evaluated as cold flow improvers in the model fuels at treat levels of 0.04 to 0.4 wt %. Both the standard pour point test (ASTM D97) and a more severe low temperature flow test (LTFT) were employed. Reductions in pour points of up to 70/sup 0/F and improvements in LTFT temperatures up to 16/sup 0/F were achieved. It is concluded that flow improver additives can play an important role in improving the cold flow properties of future synthetic fuels of the diesel type derived from oil shale.

Frankenfeld, J.W.; Taylor, W.F.

1980-11-01

391

Active Oxygen Species and Mechanism for Low-Temperature CO Oxidation Reaction on a TiO 2-Supported Au Catalyst Prepared from Au(PPh 3)(NO 3) and As-Precipitated Titanium Hydroxide  

Microsoft Academic Search

The active oxygen species and mechanism for catalytic CO oxidation with O2 on a highly active TiO2-supported Au catalyst (denoted as Au\\/Ti(OH)*4), which was prepared by supporting a Au–phophine complex on as-precipitated wet titanium hydroxide followed by calcination at 673 K, have been studied by means of oxygen isotope exchange, O2 temperature-programmed desorption (O2 TPD), electron spin resonance (ESR), and

Haichao Liu; Alexander I. Kozlov; Anguelina P. Kozlova; Takafumi Shido; Kiyotaka Asakura; Yasuhiro Iwasawa

1999-01-01

392

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

SciTech Connect

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 reactor.

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

1981-04-01

393

Wavelength-dependent resonant surface heating and desorption with IR lasers: A new spectroscopic tool  

NASA Astrophysics Data System (ADS)

Wavelength-dependent resonant heating of thin films by vibrational excitation of internal modes with a CO2 laser is studied by measuring the time-of-flight distributions of desorbed molecules. The spectroscopic features of previously published results for CCl4and C6H5CHO, and of data reported here for CH2ClCH2Cl, are discussed. The translational temperatures determined from Maxwellian distributions and the desorption yield possess the same spectral behavior as the IR absorption band.

Schafer, B.; Buck, M.; Hess, P.

1985-02-01

394

Development of Designer Diamond Technology for High Pressure High Temperature Experiments in Support of Stockpile Stewardship Program  

SciTech Connect

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.

Vohra, Yogesh, K.

2009-10-28

395

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, July--September 1993  

SciTech Connect

Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts can be 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. The primary objective of this research is to explore novel bimetallic dispersed catalysts from heterometallic molecular precursors, that can be used in low concentrations but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. This quarterly report describes the preparation of two precursors. The first is a heterometallic complex consisting of two transition metals, Mo and Ni, and sulfur in a single molecule synthesized. The second is a thiocubane type cluster consisting of iron and sulfur.

Schmidt, E.; Song, C.; Schobert, H.H.

1994-01-01

396

Flash desorption/mass spectrometry for the analysis of less- and nonvolatile samples using a linearly driven heated metal filament.  

PubMed

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 ~10(4) °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 ?g with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. Figure ? PMID:23982934

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

2013-08-28

397

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

398

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

399

Kinetic analysis of California oil shale by programmed temperature micropyrolysis. Revision 1  

SciTech Connect

Three oil shales from California were examined by micropyrolysis for evolution behavior and pyrolysis kinetic parameters to understand hydrocarbon evolution. The samples consisted of one from the Los Angeles basin, and two from the Monterey formation. The two Monterey shales were distinguished by low and high S contents of the kerogen. The measurements were performed by a Pyromat II micropyrolyzer operating at nominal constant heating rates of 1, 7, and 50 {degrees}C/min, between 250 and 700{degrees}C. The evolution profiles at 50{degrees}C/min heating rate of Los Angeles and the low S Monterey sample were similar, having the same temperature of maximum evolution (T{sub max}) (460{degrees}C) and similar peak widths ({delta}W{sub {1/2}} approximately 70{degrees}C). The high S Monterey shale was much different having a much lower T{sub max} (441{degrees}C) and a much broader profile ({delta}W{sub {1/2}} 119{degrees}C). The derived kinetic parameters of all three shales were different. The principal energy of activation from the discrete method (principal E{sub discrete}) and the energy of activation by the approximate method (E{sub approx}) were (in kcal/mol): 57 and 57 and 54; 52 and 50.6; 57 and 65.2; for Los Angeles, low S Monterey, and high S Monterey, respectively. These values agree with literature values for type II kerogens except for the high S Monterey sample, which appears to be anomalously high. 8 refs., 3 figs., 3 tabs.

Reynolds, J.G.; Burnham, A.K.

1991-12-09

400

Nonmonotonic crossover from adsorption to desorption in supercritical fluid near a weakly attractive surface.  

PubMed

The density profiles of a supercritical Lennard-Jones fluid near a weakly attractive surface are used to study the excess adsorption Gamma of supercritical fluid in a wide density range. We report the observation of two extrema of Gamma along the isotherm as a function of density. The attractive fluid-wall interaction potential tends to make Gamma positive, whereas the missing neighbor effect tends to make Gamma negative. The latter effect enhances with increasing fluid density due to the growth of the fluid-fluid attraction that results in the crossover from adsorption to depletion (Gamma=0) at some particular fluid density. With approaching the critical point, Gamma decreases as the bulk correlation length and passes through a minimum when the average density of confined fluid is close to the bulk critical density. Variation of Gamma with temperature and density is determined by the monotonic trend from adsorption to desorption upon increasing fluid density and by the increase of the absolute value of Gamma when approaching the critical point. Interplay of these trends results in two extrema of Gamma in the temperature-density plane. This effect may be responsible for the crossover from adsorption to desorption with approaching the critical temperature observed experimentally along the isotherms and along the critical isochore. The density profiles of a supercritical fluid are found to be exponential and the power law behavior predicted theoretically was not detected even when the bulk correlation length xi achieves 11 molecular diameters. PMID:19256847

Oleinikova, Alla; Brovchenko, Ivan

2008-12-02

401

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)

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 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. Electronic supplementary information (ESI) available: TEM images, XRD patterns, N2 adsorption-desorption isotherms, TG-DTA curves, in situ time-resolved XRD patterns, stability test and H2O resistance study of the catalysts. See DOI: 10.1039/c3nr02631k

Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

2013-09-01

402

Experimental study and modelling of water sorption/desorption isotherms on two agricultural products: Apple and carrot  

NASA Astrophysics Data System (ADS)

This work is focused on some properties of dried apple (Red Chief) and carrot (Misky). Water sorption isotherms of carrot and apple were investigated at three temperatures: 30, 40 and 60°C, corresponding to drying temperatures, by the static method consisting of the use of different sulphuric acid solutions. Guggenheim-Anderson-de Boer (G.A.B) model is found to describe the experimental curves better than Henderson, Hasley and Oswin models with a correlation coefficient superior to 0.97 for both products. The hysteresis phenomenon was clearly observed in the case of apple isotherms. The experimental data were also used to determine the isosteric enthalpy of desorption of apple and carrot. The isosteric enthalpy of desorption decreased with increase in moisture content and the trend became asymptotic.

Timoumi, S.; Zagrouba, F.; Mihoubi, D.; Tlili, M. M.

2004-12-01

403

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

SciTech Connect

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.

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

2008-01-01

404

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

SciTech Connect

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

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

2008-05-15

405

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

NASA Astrophysics Data System (ADS)

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.

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

2009-11-01

406

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

SciTech Connect

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.

S. Semancik; R. E. Cavicchi; D. L. DeVoe; T. J. McAvoy [National Institute of Standards and Technology (US)]|[University of Maryland (US)

2001-12-21

407

Soot structure and reactivity analysis by Raman microspectroscopy, temperature-programmed oxidation, and high-resolution transmission electron microscopy.  

PubMed

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. PMID:19899796

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

2009-12-17

408

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

SciTech Connect

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.

Choudhary, V.R.; Devadas, P.; Sansare, S.D. [National Chemical Lab., Pune (India); Guisnet, M. [Universite de Poitiers (France)

1997-03-01

409

Carbon dioxide sorption/ desorption characteristics of coals in Taiwan  

NASA Astrophysics Data System (ADS)

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

Chien-Hung, Hsiao; Loung-Yie, Tsai

2013-04-01

410

Photo-stimulated desorption of rare gas atoms induced by UV–NIR photons at a semiconductor surface  

Microsoft Academic Search

We present a study of photo-stimulated desorption of rare gas atoms adsorbed on a Si(100) surface. Rare gas atoms (Xe and Kr) are desorbed by the irradiation of photons in the range from 1.16 to 6.43eV. The translational energy distribution of desorbed species is well represented by the Maxwell–Boltzmann distribution with a temperature higher than that expected in normal laser-induced

Kazuya Watanabe; Hiroyuki Kato; Yoshiyasu Matsumoto

2000-01-01

411

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

412

Characterization of helium ion implanted reduced activation ferritic/martensitic steel with positron annihilation and helium thermal desorption methods  

NASA Astrophysics Data System (ADS)

Low energy 3 keV He implantations were carried out on Eurofer97 steel to reproduce the radiation damage induced by the creation and thermal evolution of the defects and the behavior of the implanted He is studied with the positron annihilation Doppler broadening technique (PADB) and thermal desorption spectroscopy (TDS). PADB results show that annealing at 1200 K for 1 h removes the majority of pre existing defects. The 3 keV He+ implantations were carried out in two sets of samples - 'surface polished' and 'annealed' (1200 K, 1 h), up to doses of 1018-1019 He/cm2. The samples were implanted at temperatures of 375 K and 525 K. The preliminary TDS studies show that when implanting at 375 K, the majority of He is released at desorption temperatures below 1000 K and is likely to be related to trapping at vacancies and small He clusters. At 575 K, the larger part of the desorption takes place at higher (>1000 K) temperatures and is associated with the formation of larger He-vacancy clusters, such as bubbles or voids. The migration of He during implantation towards the bulk is observed as a decrease in Doppler broadening parameter at depths much deeper the He implantation range.

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

2013-11-01

413

Enhanced saturation coverages in adsorption-desorption processes  

NASA Astrophysics Data System (ADS)

Many experimental studies of protein deposition on solid surfaces involve alternating adsorption/desorption steps. In this paper, we investigate the effect of a desorption step (separating two adsorption steps) on the kinetics, the adsorbed-layer structure, and the saturation density. Our theoretical approach involves a density expansion of the pair distribution function and an application of an interpolation formula to estimate the saturation density as a function of the density at which the desorption process commences, ?1, and the density of the depleted configuration, ?2. The theory predicts an enhancement of the saturation density compared with that of a simple, uninterrupted random sequential adsorption (RSA) process and a maximum in the saturation density when ?2=(2/3)?1. The theoretical results are in qualitative and semiquantitative agreement with the results of numerical simulations.

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

2000-01-01

414

Wavelength-selective laser desorption of doped ice surfaces  

NASA Astrophysics Data System (ADS)

We present a visible/infrared comparative photo-desorption study of several metal salt/ice binary mixtures. The cryogenic samples have been successively irradiated by a frequency-doubled (532 nm) Nd:YAG laser and a 3.1 ?m LiNbO3 optical parametric oscillator. The desorbed neutrals have been post-ionized by the focused beam of a frequency-quadrupled Nd:YAG laser at 266 nm (4.7 eV) and the ions produced have been mass-separated by a reflectron time-of-flight mass spectrometer. Wavelength-selective desorption has been evidenced for all the mixtures considered. This behaviour is tentatively explained with respect to the absorption spectra of these systems. The evolution with the desorption laser fluence and the solution concentration has also been investigated. Possible laser cleaning practical implications are discussed and illustrated by the application to a combustion soot particles/ice system.

Mihesan, C.; Ziskind, M.; Chazallon, B.; Therssen, E.; Desgroux, P.; Focsa, C.

2005-11-01

415

N-acetylglucosamine (GlcNAc) Triggers a Rapid, Temperature-Responsive Morphogenetic Program in Thermally Dimorphic Fungi.  

PubMed

The monosaccharide N-acetylglucosamine (GlcNAc) is a major component of microbial cell walls and is ubiquitous in the environment. GlcNAc stimulates developmental pathways in the fungal pathogen Candida albicans, which is a commensal organism that colonizes the mammalian gut and causes disease in the setting of host immunodeficiency. Here we investigate GlcNAc signaling in thermally dimorphic human fungal pathogens, a group of fungi that are highly evolutionarily diverged from C. albicans and cause disease even in healthy individuals. These soil organisms grow as polarized, multicellular hyphal filaments that transition into a unicellular, pathogenic yeast form when inhaled by a human host. Temperature is the primary environmental cue that promotes reversible cellular differentiation into either yeast or filaments; however, a shift to a lower temperature in vitro induces filamentous growth in an inefficient and asynchronous manner. We found GlcNAc to be a potent and specific inducer of the yeast-to-filament transition in two thermally dimorphic fungi, Histoplasma capsulatum and Blastomyces dermatitidis. In addition to increasing the rate of filamentous growth, micromolar concentrations of GlcNAc induced a robust morphological transition of H. capsulatum after temperature shift that was independent of GlcNAc catabolism, indicating that fungal cells sense GlcNAc to promote filamentation. Whole-genome expression profiling to identify candidate genes involved in establishing the filamentous growth program uncovered two genes encoding GlcNAc transporters, NGT1 and NGT2, that were necessary for H. capsulatum cells to robustly filament in response to GlcNAc. Unexpectedly, NGT1 and NGT2 were important for efficient H. capsulatum yeast-to-filament conversion in standard glucose medium, suggesting that Ngt1 and Ngt2 monitor endogenous levels of GlcNAc to control multicellular filamentous growth in response to temperature. Overall, our work indicates that GlcNAc functions as a highly conserved cue of morphogenesis in fungi, which further enhances the significance of this ubiquitous sugar in cellular signaling in eukaryotes. PMID:24068964

Gilmore, Sarah A; Naseem, Shamoon; Konopka, James B; Sil, Anita

2013-09-19

416

N-acetylglucosamine (GlcNAc) Triggers a Rapid, Temperature-Responsive Morphogenetic Program in Thermally Dimorphic Fungi  

PubMed Central

The monosaccharide N-acetylglucosamine (GlcNAc) is a major component of microbial cell walls and is ubiquitous in the environment. GlcNAc stimulates developmental pathways in the fungal pathogen Candida albicans, which is a commensal organism that colonizes the mammalian gut and causes disease in the setting of host immunodeficiency. Here we investigate GlcNAc signaling in thermally dimorphic human fungal pathogens, a group of fungi that are highly evolutionarily diverged from C. albicans and cause disease even in healthy individuals. These soil organisms grow as polarized, multicellular hyphal filaments that transition into a unicellular, pathogenic yeast form when inhaled by a human host. Temperature is the primary environmental cue that promotes reversible cellular differentiation into either yeast or filaments; however, a shift to a lower temperature in vitro induces filamentous growth in an inefficient and asynchronous manner. We found GlcNAc to be a potent and specific inducer of the yeast-to-filament transition in two thermally dimorphic fungi, Histoplasma capsulatum and Blastomyces dermatitidis. In addition to increasing the rate of filamentous growth, micromolar concentrations of GlcNAc induced a robust morphological transition of H. capsulatum after temperature shift that was independent of GlcNAc catabolism, indicating that fungal cells sense GlcNAc to promote filamentation. Whole-genome expression profiling to identify candidate genes involved in establishing the filamentous growth program uncovered two genes encoding GlcNAc transporters, NGT1 and NGT2, that were necessary for H. capsulatum cells to robustly filament in response to GlcNAc. Unexpectedly, NGT1 and NGT2 were important for efficient H. capsulatum yeast-to-filament conversion in standard glucose medium, suggesting that Ngt1 and Ngt2 monitor endogenous levels of GlcNAc to control multicellular filamentous growth in response to temperature. Overall, our work indicates that GlcNAc functions as a highly conserved cue of morphogenesis in fungi, which further enhances the significance of this ubiquitous sugar in cellular signaling in eukaryotes.

Gilmore, Sarah A.; Naseem, Shamoon; Konopka, James B.; Sil, Anita

2013-01-01

417

Determination of the carbon isotopic composition of whole/intact biological specimens using at-line direct thermal desorption to effect thermally assisted hydrolysis/methylation.  

PubMed

In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography-combustion isotope-ratio mass spectrometry (GC/C-IRMS) analysis of whole/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped programmed-temperature vaporizer (PTV) liners to the PTV injector and chemical derivatisation (thermally assisted hydrolysis/methylation; THM) such that a profile of a cellular fatty acids is obtained. Flow-cytometric sorted microalgae and handpicked zooplankton are used as samples with trimethylsulfonium hydroxide (TMSH) as methylating reagent. A major advantage of this novel approach over the Curie-point technique is the automation of the total procedure, which allows unattended analysis of large sample series. The profiles and delta(13)C carbon isotopic signatures of the fatty acid methyl esters (FAMEs) produced are very similar to those obtained using the Curie-point flash pyrolysis method. It is shown that algal samples must be kept no longer than 48 h in the DTD sample tray prior to the THM-analysis in order to maintain the integrity of their FAME profile. PMID:17897655

Akoto, Lawrence; Vreuls, René J J; Irth, Hubertus; Floris, Virgilio; Hoogveld, Hans; Pel, Roel

2007-09-11

418

Stability and fragmentation of organic silicon functionalizations studied by laser desorption mass spectrometry  

NASA Astrophysics Data System (ADS)

A method is introduced to investigate organic functionalizations on silicon by laser-induced thermal desorption (LITD), where well-ordered Si(1 1 1)-(1 × 1):H(D) surfaces are used to determine the desorption temperature as a function of laser fluence. To demonstrate the potential of this technique silicon surfaces with ultrathin oxide layers were functionalized with organic end groups. The species desorbed with focused XeCl laser pulses were monitored at an oblique angle and their time-of-flight (TOF) distributions were measured with a quadrupole mass analyzer after electron impact ionization. By assuming a negligible contribution of the oxide and organic layers to the heating effect, the TOF temperatures measured for Si(1 1 1)-(1 × 1):H(D) could be used to determine the mass of the desorbed species. Detailed results are presented for dimethylsilyl (DMS), bromomethyldimethylsilyl (BMDMS), and chloromethyldimethylsilyl (CMDMS) terminated surfaces which were prepared by silanization with suitable chloro and disilazane compounds. While for the DMS termination dimethylsilanol (76 u) is desorbed as a single species, clearly identifying the terminating group, in the case of BMDMS and CMDMS further fragmentation of the end group occurs at the surface.

Lingenfelser, Dominic; Hess, Peter

2007-05-01

419

Thermal desorption of ultraviolet--ozone oxidized Ge(001) for substrate cleaning  

SciTech Connect

X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), and reflection high-energy electron diffraction (RHEED) have been used to show that 30 min exposures of a degreased and deionized-water-rinsed Ge(001) wafer to ultraviolet (UV)--ozone in laboratory air is sufficient to remove C contamination and form a nonpermeable passive amorphous GeO[sub 2] layer with a thickness of [congruent]1.8 nm. Subsequent annealing in ultrahigh vacuum (UHV) at [ge]390 [degree]C for [ge]30 min resulted in desorption of the oxide layer and the exposure of a clean well-ordered Ge(001)2[times]1 surface. No impurities, including C and O, were detected by either XPS or AES. EELS spectra from the clean surface showed well-defined peaks corresponding to transitions involving dangling bonds, surface states, and surface plasmons. Shorter UV--ozone exposures (i.e., [lt]30 min) often resulted in residual C contamination while incomplete oxide removal was obtained at lower oxide desorption temperatures. Ge overlayers deposited by molecular beam epitaxy at temperatures between 200 and 450 [degree]C on UV--ozone processed substrates were found by a combination of plan-view and cross-sectional transmission electron microscopy to be highly perfect single crystals with abrupt film/substrate interfaces and no detectable dislocations or extended defects.

Zhang, X.; Xue, G.; Agarwal, A.; Tsu, R.; Hasan, M.; Greene, J.E.; Rockett, A. (Department of Materials Science, the Coordinated Science Laboratory, and the Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States))

1993-09-01

420

Microfabricated Glow Discharge Plasma (MFGDP) for Ambient Desorption/Ionization Mass Spectrometry.  

PubMed

A novel ambient ionization technique for mass spectrometry, microfabricated glow discharge plasma (MFGDP), is reported. This device is made of a millimeter-sized ceramic cavity with two platinum electrodes positioned face-to-face. He or Ar plasma can be generated by a direct current voltage of several hundreds of volts requiring a total power below 4 W. The thermal plume temperature of the He plasma was measured and found to be between 25 and 80 °C at a normal discharge current. Gaseous, liquid, creamy, and solid samples with molecular weights up to 1.5 kDa could be examined in both positive and negative mode, giving limits of detection (LOD) at or below the fg/mm(2) level. The relative standard deviation (RSD) of manual sampling ranged from 10% to ?20%, while correlation coefficients of the working curve (R(2)) are all above 0.98 with the addition of internal standards. The ionization mechanisms are examed via both optical and mass spectrometry. Due to the low temperature characteristics of the microplasma, nonthermal momentum desorption is considered to dominate the desorption process. PMID:24000803

Ding, Xuelu; Zhan, Xuefang; Yuan, Xin; Zhao, Zhongjun; Duan, Yixiang

2013-09-19

421

Distinguishibility of Oxygen Desorption From the Surface Region with Mobility Dominant Effects in Nanocrystalline Ceria Films  

SciTech Connect

We present an investigation of oxygen (18O) uptake measurements in 1 ?m thick nanocrystalline ceria films grown on single crystal Al?O? (0001) by nuclear reaction analysis (NRA). Oxygen uptake measurements were carried out in the temperature range of 200 0C-600 0C at a background 18O pressure of 4.0 x 10-6 Torr. Average grain-size in the as-grown films, synthesized by sol-gel process was ~ 3 nm confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) measurements. From the diffusion depth profiles, changes in intensity and slopes in surface and interface regions indicate dominating oxygen mobility effects. Oxygen desorption is clearly distinguishable in the film surface region as a result of shift in the oxygen peak intensity. It is argued that high defect density in nanocrystalline ceria which is associated with nano-grain surface combined with intermediate temperature reducing environment triggers multiple processes like diffusion, desorption and exchange interaction. The promising nature of NRA is realized as an effective tool to acquire the depth-dependent information regarding such complex reactions that exists in nanocrystalline environment.

Saraf, Laxmikant V.; Shutthanandan, V.; Zhang, Yanwen; Thevuthasan, Suntharampillai; Wang, Chong M.; El-Azab, Anter; Baer, Donald R.

2004-11-15

422

The possibility of using the thermal equation of absorption from the theory of volume filling of micropores for calculation of holding capacity of busofit in thermal vacuum desorption  

Microsoft Academic Search

An experimental study was carried out to investigate thermal desorption of organic solvents from activated carbon fiber materials (ACFM) of the busofit type in the temperature range of 29 423 K. Comparison of experimental and calculated holding capacities of ACFM has shown that the thermal equation of absorption from the theory of volume filling of micropores can be used for

A. F. Dolidovich; G. S. Akhremkova; T. V. Tumysheva

1997-01-01

423

Study on the Reduction Behavior of Zirconia Supported Iron Oxide Catalysts by Temperature-Programmed Reduction Combined with in SituMössbauer Spectroscopy  

Microsoft Academic Search

The reduction properties of Fe2O3\\/ZrO2catalysts with various Fe2O3loading and the interactions between iron oxide and zirconia have been studied by using temperature-programmed reduction combined within situMössbauer spectroscopy. This is shown that the intermediates formed during reduction depend strongly not only on the reduction temperature but also on the iron loading. Several iron species such as bulk phase ?-Fe2O3, small ?-Fe2O3particles,

Kaidong Chen; Yining Fan; Zheng Hu; Qijie Yan

1996-01-01

424

Changes in Structure and Reactivity of Soot during Oxidation and Gasification by Oxygen, Studied by Micro-Raman Spectroscopy and Temperature Programmed Oxidation  

Microsoft Academic Search

Micro-Raman spectroscopy (micro-RS) and Temperature Programmed Oxidation (TPO) combined with FTIR gas analysis have been used to determine structural changes and oxidation behavior in samples of spark discharge (GfG) and heavy duty engine (EURO IV) soot upon oxidation by oxygen in a temperature range between 293 K and 873 K. Raman spectra of soot and FTIR spectra of oxidation products

Markus Knauer; Matteo Carrara; Dieter Rothe; Reinhard Niessner; Natalia P. Ivleva

2009-01-01

425

Volatile compound evolution from the programmed temperature pyrolysis of Big Clifty and McKittrick tar sands at a 10 degrees C/min heating rate  

SciTech Connect

Big Clifty (Kentucky) and McKittrick (California) tar sands were pyrolyzed at a 10{degrees}C/min heating rate from room temperature to 900{degrees}C. The volatile compounds were detected on-line and in real time by tandem mass spectrometry using MS and MS/MS detection. This paper reports the programmed temperature pyrolysis behaviors of Big Clifty and McKittrick tar sands and compares their results. 48 refs., 10 figs., 3 tabs.

Reynolds, J.G.

1989-11-01

426

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

SciTech Connect

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 this multivariate analysis will enable superior differentiation capabilities. In addition, noise and system artifacts challenge the analysis of GC-MS data collected on lower cost equipment, ubiquitous in commercial laboratories. This research has the potential to affect many areas of analytical chemistry including materials analysis, medical testing, and environmental surveillance. It could also provide a method to measure adsorption parameters for chemical interactions on various surfaces by measuring desorption as a function of temperature for mixtures. We have presented results of a novel method for examining offgas products of a common PDMS material. Our method involves utilizing a stepped TD/GC-MS data acquisition scheme that may be almost totally automated, coupled with multivariate analysis schemes. This method of data generation and analysis can be applied to a number of materials aging and thermal degradation studies.

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

2010-09-01

427

Temperature-programmed reduction and cyclic voltammetry of Pt/carbon-fibre paper catalysts for methanol electrooxidation  

SciTech Connect

Temperature-programmed reduction (TPR) and cyclic voltammetry (CV) studies of platinum catalysts supported on pyrographite-coated carbon-fibre paper, and prepared by either ion exchange or impregnation, clearly demonstrate the nature of the interactions between the platinum species and the support. After drying the above catalysts at 120/sup 0/C, the ion-exchanged preparation exhibits the stronger interaction with the carbon support, as might be expected since a chemical interaction with carbon surface groups is known to occur in such catalysts. The presence of a fraction of bulk Pt(NH/sub 3/)/sub 4/(OH)/sub 2/ impregnating salt in the impregnated catalyst has been detected using TPR. After air activation at 300/sup 0/C, subambient reduction peaks were observed and the strength of binding of Pt in the ion-exchanged catalyst was reflected by its increased difficulty of reduction in comparison with that of the impregnated catalyst. The stoichiometry of reduction in ion-exchanged catalysts corresponds to Pt/sup 2 +/ ..-->.. Pt/sup 0/ in both dried and activated catalysts, with a small amount of Pt/sup 4 +/ present in the latter. Upon activation the impregnated catalyst showed the presence of some Pt metal, which was thought to arise from the decomposition of the fraction of bulk Pt(NH/sub 3/)/sub 4/(OH)/sub 2/ in the dried catalyst. Activation of ion-exchanged catalysts at temperatures higher than 300/sup 0/C led to a progressive weakening of the Pt-support interaction and consequent smaller Pt surface areas. Activation at 500/sup 0/C in air produced Pt metal exclusively and very low Pt surface areas. The strong interaction between Pt and the carbon support upon activation of the ion-exchanged catalyst at 300/sup 0/C is thought to be the origin of the large metal surface area and the high catalytic activity for methanol electrooxidation found upon reduction.

Attwood, P.A.; McNicol, B.D.; Short, R.T.

1981-02-01

428

Thermogravimetric Study on Oxygen Adsorption\\/Desorption Properties of Double Perovskite Structure Oxides REBaCo 2 O 5+? (RE = Pr, Gd, Y)  

Microsoft Academic Search

The oxygen adsorption\\/desorption properties of double perovskite structure oxides PrBaCo2O5+?, GdBa-Co2O5+? and YBaCo2O5+? were investigated by the thermogravimetry (TG) method in the temperature range of 400 ? 900 °C. The calculated oxygen adsorption\\/desorption surface reaction rate constants ka and kd of these double perovskite structure oxides were larger than the commonly used cubic perovskite oxides, such as Ba0.95Ca0.05Co0.8Fe0.2O3-? and Ba0.5

Hao Haoshan; Zheng Lu; Wang Yingfang; Liu Shijiang; Hu Xing

2007-01-01

429

Field-Emission Investigation of Thermal Desorption and Surface Diffusion of Cesium on Tungsten.  

National Technical Information Service (NTIS)

Thermal desorption and surface diffusion of cesium coatings on a tungsten substrate have been investigated by pulsed-field-emission microscopy. Measured values of the heat of desorption for neutral cesium atoms vary with cesium coverage from 18 kilocalori...

L. W. Swanson R. W. Strayer F. M. Charbonnier E. C. Cooper

1964-01-01

430

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

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. PMID:22099662

Tölgyessy, Peter; Vrana, Branislav; Krascsenits, Zoltán

2011-10-01

431

Reaction of NO2 with a pure, thick BaO film: the effect of temperature on the nature of NOx species formed  

SciTech Connect

The adsorption and reaction of NO2 on a thick (>30 ML), pure BaO film deposited onto an Al2O3/NiAl(110) substrate were investigated in the temperature range of 300 – 660 K using temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and x-ray photoelectron spectroscopy (XPS) techniques. The adsorption of NO2 on BaO at room temperature results in the formation of nitrite-nitrate ion pairs. During thermal desorption the nitrite species decompose first, releasing an NO molecule and leaving an O on the surface, while nitrate species decompose in two steps at higher temperatures: at lower temperature as NO2 only, then, at higher temperature, as NO + O2. In cyclic experiments when the BaO film was exposed to NO2 at 300 K, followed by annealing to 575 K, a large amount of NOx was stored as nitrates, and no saturation was achieved even after the 10th adsorption/anneal cycle. This suggests the gradual conversion of the BaO film into barium nitrate clusters at elevated temperatures. The rate of nitrate formation increases as the sample temperature during NO2 exposure increases up to 610 K, while at even higher temperatures the amount of nitrates formed decreases. NO2 adsorption on the thick BaO film at 610 K results in the formation of strongly bound nitrates as the major NOx species.

Yi, Cheol-Woo W.; Szanyi, Janos

2009-02-12

432

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, January--March 1993  

SciTech Connect

The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular precursors, that can be used in low concentrations (temperature-programmed conditions. In this quarter, we have synthesised several bimetallic complexes that contain Mo, Co, and S in a single molecule. Three of them are bimetallic thiocubanes: Mo{sub 2}Co{sub 2}S{sub 4}(S{sub 2} CNEt{sub 2})2(CH{sub 3} CN){sub 2}(CO){sub 2} [designated as MoCo-TCl], Mo{sub 2}Co{sub 2}S{sub 4}Cp{sub 2}(CO){sub 2} [MoCo-TC2], and Mo{sub 2}Co{sub 2}S{sub 4}(Cp`){sub 2}(CO){sub 2} [MoCo-TC3], in which Et, Cp and Cp` represent ethyl, cyclopentadiene, and pentainethylcyclopentadiene, respectively. These thiocubanes were synthesized in our laboratory based on the procedures reported in literature. For comparative examination, the tdanionic bimetallic complex, (PPh{sub 4}){sub 3}Co(MoS{sub 4}){sub 2}, was also synthesized. This bimetallic sulfide complex contains cobalt bis-tetrathiomolybdate trianion, Co(MoS{sub 4}){sub 2}{sup 3{minus}}, and is designated as MoCo-S.

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

1993-07-01

433

Microchannel membrane separation applied to confined thin film desorption  

Microsoft Academic Search

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

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

2006-01-01