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1

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

2

Conductance-Based Temperature Programmed Desorption with Single Defect Resolution  

NASA Astrophysics Data System (ADS)

The controlled functionalization of nanotubes and graphene requires methods of chemically attacking these inert surfaces and of removing unwanted oxidation damage. The appeal of reversible chemistries is rarely achieved: the degraded electrical properties of reduced graphene oxide compared to pristine graphene indicates residual damage that remains poorly understood. Using a high temperature, UHV apparatus to perform electrical measurements in situ, we investigate the thermal desorption of adducts that can restore conductivity in oxidized nanographites. The majority of our measurements are accomplished using SWCNTs, due to their enhanced sensitivity to even single point defects. Discrete conductance jumps accompanying the removal of different types of adducts provide a characterization method that directly distinguishes the relative electronic effects of phenolic, epoxide, and carboxylic defects. The electronic measurements complement more traditional, temperature programmed desorption from bulk material, which is insensitive to electronic disorder.

Pan, Deng; Sims, Patrick C.; Corso, Brad L.; Collins, Philip G.

2011-03-01

3

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

4

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

5

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

6

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

E-print Network

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

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

2007-01-01

7

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

E-print Network

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

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

2008-11-21

8

Statistical analysis of blister bursts during temperature-programmed desorption of deuterium-implanted polycrystalline tungsten  

NASA Astrophysics Data System (ADS)

During temperature-programmed desorption (TPD) of stress-relieved polycrystalline tungsten samples exposed to a deuterium plasma, short, intense bursts of D2 were observed on the low-temperature flank of the main desorption peak. These bursts are attributed to the rupturing of blisters filled with high-pressure D2 gas. A statistical analysis of the size distribution and temporal correlation of the bursts is presented. The influence of different measurement intervals and TPD heating rates on the observed bursts is simulated based on these statistics and compared to the experimental results. The contribution of bursts to the total D inventory in the sample is also estimated.

Manhard, A.; Toussaint, U. v.; Dürbeck, T.; Schmid, K.; Jacob, W.

2011-12-01

9

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

10

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

11

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

12

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

PubMed

Temperature-programmed desorption was performed at temperatures up to 850 K on as-received fumed and precipitated silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 38-61 kJ/mol. However, the activation energies of desorption for chemisorbed water varied from approximately 80 to >247 kJ/mol for fumed silica, Cab-O-Sil-M-7D, and approximately 96 to 155 kJ/mol for precipitated silica, Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>126 kJ/mol) will not escape silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (80-109 kJ/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies <126 kJ/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1-0.4 wt% of water in silica-reinforced polysiloxane formulations containing approximately 21% Cab-O-Sil-M-7D and approximately 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that the adsorbed H(2)O and the Si-OH bonds on the silica surfaces are the major contributors to water outgassing from these types of silica-filled polymers. Copyright 2000 Academic Press. PMID:11017751

Dinh; Balooch; LeMay

2000-10-15

13

Surface Chemistry of Activated Carbons: Combining the Results of Temperature-Programmed Desorption, Boehm, and Potentiometric Titrations  

Microsoft Academic Search

Three samples of activated carbon were used for this study: two of wood and one of coal origin. The samples were further oxidized to study the effect of oxidation on the surface chemistry. The surface chemistry was characterized by using Boehm and potentiometric titrations, temperature-programmed desorption (TPD), and DRFTS. The results showed that oxidation introduces a variety of functional groups

Issa I. Salame; Teresa J. Bandosz

2001-01-01

14

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

NASA Astrophysics Data System (ADS)

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

Vogt, Andrew Dale

1999-12-01

15

Adsorption and desorption of dibenzothiophene on Ag-titania studied by the complementary temperature-programmed XPS and ESR  

NASA Astrophysics Data System (ADS)

Adsorption, desorption and structure of the surface chemical compounds formed upon interaction of dibenzothiophene (DBT) in solution of n-octane with the sulfur-selective Ag/Titania sorbent for the ultradeep desulfurization of liquid fuels was characterized by the temperature-programmed X-ray photoemission spectroscopy (XPS) and Electron Spin Resonance. Adsorption of DBT proceeds via chemisorption via the oxygen-containing surface groups. Desorption of DBT and thermal regeneration of the “spent” Ag/Titania were studied by the complementary temperature-programmed XPS and ESR from 25 °C to 525 °C, in the high vacuum vs. air. The XPS spectrum of the pure DBT is reported for the first time.

Samokhvalov, Alexander; Duin, Evert C.; Nair, Sachin; Tatarchuk, Bruce J.

2011-02-01

16

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

17

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

PubMed

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

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

2014-01-01

18

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

19

Decomposition of NH3 on Ir(100): A Temperature Programmed Desorption Study A. K. Santra, B. K. Min, C. W. Yi, Kai Luo, T. V. Choudhary, and D. W. Goodman*  

E-print Network

Decomposition of NH3 on Ir(100): A Temperature Programmed Desorption Study A. K. Santra, B. K. Min 27, 2001 Ammonia adsorption has been studied on an Ir(100) surface in the temperature range 100-410 K. In contrast to previous studies on Ir(111), approximately 12% of the chemisorbed ammonia undergoes stepwise

Goodman, Wayne

20

Characterization of polymers by multi-step thermal desorption\\/programmed pyrolysis gas chromatography using a high temperature PTV injector  

Microsoft Academic Search

Summary Thermal treatment hyphenated with gas chromatography is a ver- satile and powerful tool in the study of polymer characterization. An inexpensive system where thermal treatment at different tem- peratures occurs inside a Programmable Temperature Vaporization injector (PTV) is described. The samples investigated, commercial plastics, are complex mixtures that contain several polymers and additives. These plastics as well as their

Lieshout van HPM; JGM Janssen; Carel A. Cramers; Martin J. J. Hetem; Huub J. P. Schalk

1996-01-01

21

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

22

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

23

Desorption isotherms and glass transition temperature for chicken meat  

Microsoft Academic Search

Desorption isotherms of chicken meat were obtained at different temperatures in the range 4–30 °C and at eight levels of salt solutions using the Novasina AWC203 multi-channel system. Several models were tested to describe the experimental sorption data; the Ferro Fontan model followed by the GAB equation gave the best fit for the whole range of water activity and temperatures,

Adriana E Delgado; Da-Wen Sun

2002-01-01

24

Characterization of olive oil volatiles by multi-step direct thermal desorption-comprehensive gas chromatography-time-of-flight mass spectrometry using a programmed temperature vaporizing injector.  

PubMed

The feasibility of a versatile system for multi-step direct thermal desorption (DTD) coupled to comprehensive gas chromatography (GC x GC) with time-of-flight mass spectrometric (TOF-MS) detection is studied. As an application the system is used for the characterization of fresh versus aged olive oil after treatment at 70, 175, 250 and 600 degrees C. PMID:17628576

de Koning, Sjaak; Kaal, Erwin; Janssen, Hans-Gerd; van Platerink, Chris; Brinkman, Udo A Th

2008-04-01

25

Optical detection of CO and CO2 temperature dependent desorption from carbon nanotube clusters.  

PubMed

The development of new materials relies on high precision methods to quantify adsorption/desorption of gases from surfaces. One commonly used approach is temperature programmed desorption spectroscopy. While this approach is very accurate, it requires complex instrumentation, and it is limited to performing experiments under high vacuum, thus restricting experimental scope. An alternative approach is to integrate the surface of interest directly onto a detector face, creating an active substrate. One surface that has applications in numerous areas is the carbon nanotube (CNT). As such, an active substrate that integrates a CNT surface on a sensor and is able to perform measurements in ambient environments will have significant impact. In the present work, we have developed an active substrate that combines an optical sensor with a CNT cluster substrate. The optical sensor is able to accurately probe the temperature dependent desorption of carbon monoxide and carbon dioxide gases from the CNT cluster surface. This active substrate will enable a wide range of temperature dependent desorption measurements to be performed from a scientifically interesting material system. PMID:25189292

Chistiakova, M V; Armani, A M

2014-10-01

26

Acidity and basicity of hydrotalcite derived mixed Mg-Al oxides studied by test reaction of MBOH conversion and temperature programmed desorption of NH{sub 3} and CO{sub 2}  

SciTech Connect

Mg-Al hydrotalcites intercalated with five different interlayer anions--CO{sub 3}{sup 2-}, SO{sub 4}{sup 2-}, Cl{sup -}, HPO{sub 4}{sup 2-} or terephthalate--were synthesized by either the coprecipitation or ion-exchange method. The structure of the as-synthesized samples and the presence of intended anions in the interlayer gallery of hydrotalcites were determined by X-ray diffraction and FTIR spectroscopy. On calcination at 600 deg. C the materials were transformed into mixed metal oxides. The kind of the counterbalancing anions present in the parent hydrotalcite influences strongly textural parameters of the obtained Mg-Al oxides. Both temperature-programmed desorption of NH{sub 3} and CO{sub 2}, and test reaction of 2-methyl-3-butyn-2-ol (MBOH) conversion were used to determine the acidity and basicity of the samples. The hydrotalcite derived mixed Mg-Al oxides showed the presence of Broensted and Lewis acid and base sites. However, the strong basic character of the solids caused that acetone and acetylene were observed as the major products of MBOH conversion.

Kustrowski, Piotr; Chmielarz, Lucjan; Bozek, Ewa; Sawalha, Murad; Roessner, Frank

2004-02-02

27

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

PubMed Central

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

2014-01-01

28

Low-temperature plasma probe for ambient desorption ionization.  

PubMed

A low-temperature plasma (LTP) probe has been developed for ambient desorption ionization. An ac electric field is used to induce a dielectric barrier discharge through use of a specially designed electrode configuration. The low-temperature plasma is extracted from the probe where it interacts directly with the sample being analyzed, desorbing and ionizing surface molecules in the ambient environment. This allows experiments to be performed without damage to the sample or underlying substrate and, in the case of biological analysis on skin surfaces, without electrical shock or perceptible heating. Positive or negative ions are produced from a wide range of chemical compounds in the pure stateand as mixtures in the gaseous, solution, or condensed phases, using He, Ar, N2, or ambient air as the discharge gas. Limited fragmentation occurs, although it is greater in the cases of the molecular than the atomic discharge gases. The effectiveness of the LTP probe has been demonstrated by recording characteristic mass spectra and tandem mass spectra of samples containing hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT) from poly(tetrafluoroethylene) (PTFE) surfaces where limits of detection are as low as 5 pg. Other performance characteristics, when using a commercial ion trap mass spectrometer, include 3-4 orders of magnitude linear dynamic range in favorable cases. Demonstration applications include direct analysis of cocaine from human skin, determination of active ingredients directly in drug tablets, and analysis of toxic and therapeutic compounds in complex biological samples. Ionization of chemicals directly from bulk aqueous solution has been demonstrated, where limits of detection are as low as 1 ppb. Large surface area sampling and control of fragmentation by a simple adjustment of the electrode configuration during operation are other demonstrated characteristics of the method. PMID:19551980

Harper, Jason D; Charipar, Nicholas A; Mulligan, Christopher C; Zhang, Xinrong; Cooks, R Graham; Ouyang, Zheng

2008-12-01

29

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...

30

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

SciTech Connect

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

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

2002-12-01

31

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

EPA Science Inventory

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

32

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

EPA Science Inventory

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

33

Medium temperature thermal desorption soil remediation case study - Selfridge Air National Guard Base, Mt. Clemens, Michigan  

SciTech Connect

Carlo Environmental Technologies, Inc., (CET) was contracted by the Selfridge Air National Guard base (SANG) to remove an abandoned underground storage tank (UST) farm and remediate the contaminated soil using thermal desorption technology. The first phase of this project was to remove fourteen 25,000 gal underground storage tanks that had been installed during the 1930's, including all ancillary equipment at the facility. The USTs had been used to store aviation fuels, including both av-gas and jet fuels. The tank-removal project disclosed over 5000 yd[sup 3] of contaminated soil in the tank excavation pit, and excavation continued until analytical sampling demonstrated that the perimeter was within the Michigan Department of Natural Resources (MDNR) Act 307 Type B cleanup criteria (state superfund act). The contaminated soil was trucked to a remote location on the base property for the thermal remediation. CET employed its Cedarapids 64MT thermal desorption plant to treat the contaminated soils from the tank removal site. These soils were predominantly clays, and the contamination included BTEX compounds up to 5 parts per million (ppm), and PNA compounds per 100 ppm. The medium temperature thermal desorption process, which heats the contaminated soil to approximately 850[degrees]F was successful in removing BTEX and PNA contamination from the soil (to levels below MDNR Type B cleanup criteria). The vapor stream from the desorption process was then filtered to minimize particulate emissions, and the contaminant compounds were then destroyed in the thermal oxidizer section of the process, at temperatures up to 1800[degrees]F. The remediated soil was returned to the original excavation as clean compacted fill material. With the use of the thermal desorption technology, CET remediated the site to MDNR cleanup standards, recycled the soils from the site, and eliminated off-site disposal liability for SANG.

Flemingloss, K. (Carlo Environmental Technologies, Inc., Clinton Township, MI (United States))

1994-08-01

34

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

35

Analysis and theory of multilayer desorption: Ag on Re  

NASA Astrophysics Data System (ADS)

A multilayer lattice gas model is set up to calculate the temperature programmed desorption spectra and other data for silver on rhenium. A careful comparison of experimental and theoretical desorption spectra implies that the surface is partially stepped with the step density likely increasing as one approaches the desorption range. Experimental temperature inhomogeneities of a few percent across the surface are suggested by careful isosteric and threshold Arrhenius analyses and theoretical modeling. A rate subtraction procedure commonly used to analyze multilayer desorption data is shown to be unnecessary. Layer plots are presented and some general features for overlapping desorption peaks are discussed.

Payne, S. H.; LeDue, J. M.; Michael, J. C.; Kreuzer, H. J.; Wagner, R.; Christmann, K.

2002-06-01

36

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

37

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

SciTech Connect

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

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

1999-12-07

38

Nestedness Temperature Calculator Program  

NSDL National Science Digital Library

A nestedness "temperature" (signal-to-noise) calculator was developed some time ago to assess nestedness in natural ecological situations and the extinction risk of individual populations within an archipelago of islands on which the species assemblages live. The Nestedness Calculator "measures the extent of the order present in nested presence-absence matrices, as well as provides a risk assessment of the extinction probability of the various species' populations isolated on islands of fragmented habitat". This program (Windows only) can be downloaded from this site at this time. Nearly three hundred presence-absence matrices taken from the primary ecological literature accompany the calculator. Rob Vosper of Chicago's Field Museum, along with AICS Research, Inc., have made this tool accessible to ecologists doing work in island biogeography, reserve design, and theoretical ecology.

39

Desorption Kinetics of Methanol, Ethanol, and Water from Graphene  

SciTech Connect

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

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

2014-09-18

40

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...

41

Adsorption and thermal desorption on stepped surfaces  

NASA Astrophysics Data System (ADS)

A lattice gas model for the adsorption and thermal desorption on stepped surfaces is formulated with different adsorption sites on the terraces, the lower base and the upper edge of the steps and including various lateral interactions. We employ transfer matrix techniques to get the equilibrium properties, correlation functions and temperature-programmed desorption spectra. A systematic study is presented on the effect of varying terrace widths for atomic, molecular and dissociative adsorption with attractive and/or repulsive lateral interactions. We also present preliminary fits to experimental data on Xe, CO and hydrogen desorption from stepped Pt(111) surfaces.

Payne, S. H.; Kreuzer, H. J.

1998-03-01

42

Adsorption and Desorption of HCI on Pt(111)  

SciTech Connect

The adsorption and desorption of HCl on Pt(111) is investigated by temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and low energy electron diffraction (LEED). Five peaks are identified in the TPD spectra prior to the onset of multilayer desorption. For (theta > 0.38 ML, theta = 1.5x1015 cm-2) HCl adsorbs molecularly at 20 K as an amorphous solid with two desorption peaks at 70 and 77 K. A third peak at 84 K is tentatively assigned to molecularly adsorbed HCl. Peaks at ~135 and 200 K are assigned to recombinative desorption of dissociated HCl, in agreement with earlier studies. Kinetic analysis is conducted and the results demonstrate a strong coverage dependent desorption energy for theta < 0.25 ML. The LEED data indicates that at low temperature the adsorbed HCl clusters into ordered islands with a (3 x 3) structure and a local coverage of 4/9 with respect to the Pt(111) substrate.

Daschbach, John L.; Kim, Jooho; Ayotte, Patrick; Smith, R. Scott; Kay, Bruce D.

2005-07-26

43

Effect of desorption temperature on CO 2 adsorption equilibria of the honeycomb zeolite beds  

Microsoft Academic Search

The behaviours of MS-13X and MS-4A were examined. The fitness of the Dubinin–Astakhov equation to the adsorption equilibria of the fully-desorbed honeycomb beds was examined. The validity of the Langmuir approximation to the obtained adsorption equilibria for relatively low CO2 partial pressures was also discussed. The CO2 adsorption equilibria of the honeycomb zeolite beds are not affected by it's desorption

K Kamiuto; S Abe; Ermalina

2002-01-01

44

Effect of desorption temperature on CO2 adsorption equilibria of the honeycomb zeolite beds  

Microsoft Academic Search

The behaviours of MS-13X and MS-4A were examined. The fitness of the Dubinin-Astakhov equation to the adsorption equilibria of the fully-desorbed honeycomb beds was examined. The validity of the Langmuir approximation to the obtained adsorption equilibria for relatively low CO2 partial pressures was also discussed. The CO2 adsorption equilibria of the honeycomb zeolite beds are not affected by it's desorption

K. Kamiuto; S. Abe; Ermalina

2002-01-01

45

High resolution, wide range, thermal desorption spectrometry of rare gas layers: sticking, desorption kinetics, layer growth, phase transitions, and exchange processes  

NASA Astrophysics Data System (ADS)

Dynamical range, resolution, and accuracy of thermal desorption spectroscopies (programmed and isothermal) have been considerably improved, and coupled with sample temperatures down to 5 K, to study adsorption and desorption kinetics of Ne, Ar, Kr, and Xe on Ru(001). Layerwise growth is observed in all cases. Sticking increases markedly with coverage to saturate only at 2 monolayers and exhibits a quantum effect at zero coverage at least for Ne and Ar. Desorption rates show influences of layer structure, island growth, intralayer phase transitions, and non-equilibrium effects, of minority species, and of exchange processes in adsorption and desorption.

Schlichting, Hartmut; Menzel, Dietrich

46

Adsorption and desorption of hydrogen on Rh(311) and comparison with other Rh surfaces  

NASA Astrophysics Data System (ADS)

We present LEED and thermal desorption data for hydrogen adsorption on Rh(311). An anisotropic lattice gas model with first, second and third nearest neighbor and trio interactions is set up and solved using transfer matrix techniques to explain equilibrium structural data and temperature-programmed desorption consistently. A comparison with results for hydrogen on Rh(110) and Rh(111) is made.

Payne, S. H.; Kreuzer, H. J.; Frie, W.; Hammer, L.; Heinz, K.

1999-02-01

47

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

SciTech Connect

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

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

2014-05-08

48

Sorption-desorption of Th(IV) on attapulgite: effects of pH, ionic strength and temperature.  

PubMed

The sorption of Th(IV) on attapulgite was studied as a function of pH, ionic strength, temperature, attapulgite contents and Th(IV) concentrations under ambient conditions using a batch technique. The results indicated that sorption of Th(IV) on attapulgite was strongly affected by pH values, and weakly dependent on ionic strength. Sorption of Th(IV) was dominated by surface complexation, although ion exchange also contributed to this sorption. Sorption of Th(IV) increased with increasing temperature of the system. Enthalpy (DeltaH(0)), entropy (DeltaS(0)) and Gibbs free energy (DeltaG(0)) were calculated from the temperature-dependent sorption data; the results indicated that the sorption of Th(IV) on attapulgite was a spontaneous process. Sorption-desorption hysteresis indicated that the sorption of Th(IV) was irreversible, and that the Th(VI) adsorbed on attapulgite was difficult to be desorbed from solid to liquid phases. PMID:17604176

Wu, Wangsuo; Fan, Qiaohui; Xu, Junzheng; Niu, Zhiwei; Lu, Songsheng

2007-10-01

49

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

PubMed

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

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

2014-09-01

50

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

SciTech Connect

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

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

1982-04-01

51

Adsorption and desorption of CO on Ru(0 0 0 1): A comprehensive analysis  

NASA Astrophysics Data System (ADS)

A comprehensive theory of the adsorption of CO on Ru(0 0 0 1) is developed to describe equilibrium properties and the adsorption and desorption kinetics. The basis is a multi-site lattice gas model with site exclusion and lateral interactions between CO molecules out to second neighbour unit cells. The theory reproduces the coverage and temperature dependence of coverage isobars, heat of adsorption, structural data, sticking coefficients, and isothermal and temperature-programmed desorption rates in a consistent manner.

Payne, S. H.; McEwen, J.-S.; Kreuzer, H. J.; Menzel, D.

2005-12-01

52

Water desorption from nanostructured graphite surfaces.  

PubMed

Water interaction with nanostructured graphite surfaces is strongly dependent on the surface morphology. In this work, temperature programmed desorption (TPD) in combination with quadrupole mass spectrometry (QMS) has been used to study water ice desorption from a nanostructured graphite surface. This model surface was fabricated by hole-mask colloidal lithography (HCL) along with oxygen plasma etching and consists of a rough carbon surface covered by well defined structures of highly oriented pyrolytic graphite (HOPG). The results are compared with those from pristine HOPG and a rough (oxygen plasma etched) carbon surface without graphite nanostructures. The samples were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TPD experiments were conducted for H2O coverages obtained after exposures between 0.2 and 55 langmuir (L) and reveal a complex desorption behaviour. The spectra from the nanostructured surface show additional, coverage dependent desorption peaks. They are assigned to water bound in two-dimensional (2D) and three-dimensional (3D) hydrogen-bonded networks, defect-bound water, and to water intercalated into the graphite structures. The intercalation is more pronounced for the nanostructured graphite surface in comparison to HOPG surfaces because of a higher concentration of intersheet openings. From the TPD spectra, the desorption energies for water bound in 2D and 3D (multilayer) networks were determined to be 0.32 ± 0.06 and 0.41 ± 0.03 eV per molecule, respectively. An upper limit for the desorption energy for defect-bound water was estimated to be 1 eV per molecule. PMID:24018989

Clemens, Anna; Hellberg, Lars; Grönbeck, Henrik; Chakarov, Dinko

2013-12-21

53

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

SciTech Connect

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

Not Available

1980-06-01

54

Thermal desorption of 3He from T@C 60  

NASA Astrophysics Data System (ADS)

The interaction of recoil tritium (T), with an initial kinetic energy of 2.7 MeV with C 60 molecules, is studied in a 6Li( n, ?) T activated homogenized compound matrix of Li 2CO 3 and C 60. Liquid scintillation spectrometry coupled with high pressure liquid chromatography (HPLC) revealed endohedral T insertion into the fullerene cage upon extraction of the fullerene species into the organic phase. Solid state temperature programmed desorption profiles of the activated compound target showed the desorption of 3He gas (as a ?- decay product from T) from the endohedral T@C 60 at 882 °C. The deconvoluted evolved gas analysis-mass spectral (EGA-MS) data provided a 25% probability of T@C 60 formation upon nuclear activation of the compound target. The non-isothermal kinetics of the tritium desorption, studied as a function of temperature, revealed the process to be diffusion controlled.

Sahoo, Rashmi R.; Patnaik, Archita

2001-11-01

55

Low-temperature resource assessment program update  

Microsoft Academic Search

The US Department of Energy-Geothermal Division (DOE\\/GD) started a new two-year program in 1992 to encourage wider use of low-temperature geothermal resources. Two main objectives of the program are: (1) to update and compile databases for wells and springs in 10 western states with temperature ranges of 20[degrees] to 150[degrees]C, and (2) to collect and interpret information on utility geothermal

P. J. Lienau; H. Ross

1993-01-01

56

Thermal desorption of circumstellar and cometary ice analogs  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

57

Characterization of Biochar using Temperature Programmed Oxidation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biochar from the fast pyrolysis of biomass was characterized by Temperature Programmed Oxidation. This technique can be used to assess the oxidative reactivity of carbonaceous solids where higher temperature reactivity indicates greater structural order. The samples examined include soy and barley...

58

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

59

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

60

Theory of dissociative and nondissociative adsorption and desorption  

NASA Astrophysics Data System (ADS)

Based on nonequilibrium thermodynamics we formulate a general theory of the kinetics of adsorption, desorption, and dissociation of gases at surfaces. We begin with a concise formulation of dissociation equilibrium at surfaces and then derive the kinetic equations for adsorption, desorption, and dissociation. For the explicit calculations we employ a lattice gas model for homonuclear molecules with both atoms and molecules present on the surface. Lateral interactions between all species are accounted for. In a series of model calculations we discuss equilibrium properties, such as heats of adsorption, and examine the role of dissociation dis-equilibrium on the time evolution of an adsorbate during temperature programmed desorption. The further effect of (attractive or repulsive) lateral interactions on the kinetics is elucidated in further model calculations. As a realistic example we apply the theory to oxygen on Pt(111).

Kreuzer, H. J.; Payne, S. H.; Drozdowski, A.; Menzel, D.

1999-04-01

61

Water and Methanol Adsorption on MgO(100)/Mo(100) Studied by Electron Spectroscopies and Thermal Programmed Desorption  

E-print Network

Water and Methanol Adsorption on MgO(100)/Mo(100) Studied by Electron Spectroscopies and Thermal, 2000 The adsorption of methanol (CH3OH) and water (D2O) on the MgO(100)/Mo(100) surface at 100 K has covered MgO(100)/Mo(100) surface. On the other hand, the formation of a methanol multilayer desorption

Goodman, Wayne

62

Adsorption and desorption dynamics of H2 and D2 on Cu(111): The role of surface temperature and evidence for corrugation of the dissociation barrier  

NASA Astrophysics Data System (ADS)

We report the effect of surface temperature on the state resolved translational energy distributions for H2 and D2 recombinatively desorbed from Cu(111). Sticking functions S(v,J,E) can be obtained by applying detailed balance arguments and follow the familiar error function form at high energy, consistent with previous permeation measurements [Rettner et al., J. Chem. Phys. 102, 4625 (1995)]. The widths of the sticking functions are identical for both isotopes and are independent of rotational state. S(E) broadens rapidly with increasing surface temperature, with a low energy component which is slightly larger than represented by an error function form. This is similar to the behavior seen on Ag(111) [Murphy et al., Phys. Rev. Lett. 78, 4458 (1997)] but on Cu(111) the low energy component remains a minor desorption channel. The broadening of S(E) can be explained in terms of a change in the distribution of barriers caused by local thermal displacement of the surface atoms, thermal activation of the surface producing sites where molecules can dissociate, or desorb, with a reduced translational activation barrier. At low energy sticking increases rapidly with surface temperature, with an activation energy of 0.54 and 0.60 eV for H2 and D2, respectively. These values are similar to the thermal activation energies calculated for translational excitation of H2/D2 and imply that thermal excitation of the surface is just as efficient as translational energy in promoting dissociation. The influence of surface temperature decreases with increasing translational energy as molecules become able to dissociate even on the static Cu(111) surface. By comparing the energy distributions for desorption with existing angular distributions we determine how the effective energy, Ee=E cosn(E) ? which contributes to adsorption-desorption, scales with translational energy. At translational energies near the threshold for sticking n(E)?2, sticking scales with the normal component of the translational energy and is not influenced by motion parallel to the surface. At lower energy n(E) drops towards zero, indicating that motion parallel to the surface aids dissociation, consistent with dissociation at a corrugated barrier.

Murphy, M. J.; Hodgson, A.

1998-03-01

63

Program predicts reservoir temperature and geothermal gradient  

SciTech Connect

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

Kutasov, I.M.

1992-06-01

64

Low-Temperature Power Electronics Program  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

65

Surface-enhanced Raman spectroscopy and temperature-programmed desorption of benzene, pyridine and C(60)  

Microsoft Academic Search

A surface-enhanced Raman scattering (SERS) -active surface consisting of a silver film over silica nanospheres (AgFON\\/SiOsb2) was developed for use in an ultrahigh vacuum (UHV) environment. The surface is demonstrated to be temporally and thermally stable and able to withstand repeated dosing with adsorbate. It can also be regenerated in vacuum until it eventually loses enhancement due to surface contamination.

Maritoni Litorja

1997-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

67

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...

68

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...

69

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

70

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

SciTech Connect

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

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

2007-11-14

71

Temperature programmed decomposition of uranyl nitrate hexahydrate  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

73

Study of the Thermal Decomposition of Some Components of Biomass by Desorption Mass Spectrometry  

NASA Astrophysics Data System (ADS)

The investigation of thermal transformations of lignin samples have been carried out using temperature programmed desorption mass spectrometry method (TPD-MS). Main stages and products of lignin pyrolysis have been identified. The first stages (Tmax = 230 °C and Tmax = 300 °C) are attributed to thermal transformations of lignin peripheral polysaccharide fragments such as hemicellulose and cellulose respectively. The second stage (Tmax = 335 °C) is associated with desorption of lignin structural elements in the molecular forms as a result of depolymerization processes of polymeric blocks of lignin. The third stage (Tmax = 370 °C) correspond to a deeper decomposition of lignin and characterized by desorption of smaller structural fragments in molecular forms (m/z = 110, pyrocatechol). Pressure-temperature curves of pyrolysis of lignin samples have been analyzed.

Palianytsia, Borys; Kulik, Tetiana; Dudik, Olesia; Cherniavska, Tetiana; Tonkha, Oksana

74

The NASA high temperature superconductivity program  

NASA Technical Reports Server (NTRS)

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.

1990-01-01

75

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

76

Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces  

SciTech Connect

The adsorption and desorption of halogen and other gaseous species from surfaces is a key fundamental process for both wet chemical and dry plasma etch and clean processes utilized in nanoelectronic fabrication processes. Therefore, to increase the fundamental understanding of these processes with regard to aluminum nitride (AlN) surfaces, temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) have been utilized to investigate the desorption kinetics of water (H{sub 2}O), fluorine (F{sub 2}), hydrogen (H{sub 2}), hydrogen fluoride (HF), and other related species from aluminum nitride thin film surfaces treated with an aqueous solution of buffered hydrogen fluoride (BHF) diluted in methanol (CH{sub 3}OH). Pre-TPD XPS measurements of the CH{sub 3}OH:BHF treated AlN surfaces showed the presence of a variety of Al-F, N-F, Al-O, Al-OH, C-H, and C-O surfaces species in addition to Al-N bonding from the AlN thin film. The primary species observed desorbing from these same surfaces during TPD measurements included H{sub 2}, H{sub 2}O, HF, F{sub 2}, and CH{sub 3}OH with some evidence for nitrogen (N{sub 2}) and ammonia (NH{sub 3}) desorption as well. For H{sub 2}O, two desorption peaks with second order kinetics were observed at 195 and 460?°C with activation energies (E{sub d}) of 51?±?3 and 87?±?5?kJ/mol, respectively. Desorption of HF similarly exhibited second order kinetics with a peak temperature of 475?°C and E{sub d} of 110?±?5?kJ/mol. The TPD spectra for F{sub 2} exhibited two peaks at 485 and 585?°C with second order kinetics and E{sub d} of 62?±?3 and 270?±?10?kJ/mol, respectively. These values are in excellent agreement with previous E{sub d} measurements for desorption of H{sub 2}O from SiO{sub 2} and AlF{sub x} from AlN surfaces, respectively. The F{sub 2} desorption is therefore attributed to fragmentation of AlF{sub x} species in the mass spectrometer ionizer. H{sub 2} desorption exhibited an additional high temperature peak at 910?°C with E{sub d}?=?370?±?10?kJ/mol that is consistent with both the dehydrogenation of surface AlOH species and H{sub 2} assisted sublimation of AlN. Similarly, N{sub 2} exhibited a similar higher temperature desorption peak with E{sub d}?=?535?±?40?kJ/mol that is consistent with the activation energy for direct sublimation of AlN.

King, Sean W., E-mail: sean.king@intel.com; Davis, Robert F. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nemanich, Robert J. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2014-09-01

77

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

NASA Astrophysics Data System (ADS)

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

Belton, David N.; Schmieg, Steven J.

1988-08-01

78

Desorption From Interstellar Ices  

E-print Network

The desorption of molecular species from ice mantles back into the gas phase in molecular clouds results from a variety of very poorly understood processes. We have investigated three mechanisms; desorption resulting from H_2 formation on grains, direct cosmic ray heating and cosmic ray induced photodesorption. Whilst qualitative differences exist between these processes (essentially deriving from the assumptions concerning the species-selectivity of the desorption and the assumed threshold adsorption energies, E_t) all three processes are found to be potentially very significant in dark cloud conditions. It is therefore important that all three mechanisms should be considered in studies of molecular clouds in which freeze-out and desorption are believed to be important. Employing a chemical model of a typical static molecular core and using likely estimates for the quantum yields of the three processes we find that desorption by H_2 formation probably dominates over the other two mechanisms. However, the physics of the desorption processes and the nature of the dust grains and ice mantles are very poorly constrained. We therefore conclude that the best approach is to set empirical constraints on the desorption, based on observed molecular depletions - rather than try to establish the desorption efficiencies from purely theoretical considerations. Applying this method to one such object (L1689B) yields upper limits to the desorption efficiencies that are consistent with our understanding of these mechanisms.

J. F. Roberts; J. M. C. Rawlings; S. Viti; D. A. Williams

2007-08-24

79

Thermal Decomposition and Desorption of Diethylamido of Tetrakis (Diethylamido)Zirconium (TDEAZr) on Si(100)  

Microsoft Academic Search

The thermal decomposition pathway and desorption of diethylamido of tetrakis (diethylamido)zirconium [TDEAZr, Zr(N(C2H5)2) 4] on Si(100) were studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). During TPD experiments, ethylethyleneimine (C2H5N=CHCH3), diethylamine [NH(C2H5)2], acetonitrile (CH3CN), ethylene (C2H4) and hydrogen (H2) desorbed as the main decomposition products of diethylamido, which was chemisorbed on Si(100) through the scission of the zirconium-diethylamido

Joonhee Jeong; Sungwon Lim; Kijung Yong

2003-01-01

80

Adsorption-desorption kinetics of the monomer-dimer mixture  

NASA Astrophysics Data System (ADS)

The kinetics of the monomer-dimer mixtures is formulated in the framework of the kinetic lattice gas model. The so-called local evolution rules are used to derive the hierarchy of coupled differential equations for coverage and other correlators, when processes like adsorption, desorption and diffusion are included. The hierarchy of equation is truncated by using mean-field (m,n) closures. Equilibrium properties are analyzed. In particular, adsorption isotherms as a function of the nearest neighbor lateral interaction are presented. The irreversible kinetics are also considered. Temperature-programmed-desorption (TPD) with readsorption is of special interest and this experiment is simulated under different conditions giving different spectra. In these spectra, the influence of adsorbate mobility is analyzed in two dimensions by Monte Carlo simulations.

Boscoboinik, J. A.; Manzi, S. J.; Pereyra, V. D.

2010-04-01

81

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...

82

Additional constraints in adsorption-desorption kinetics  

NASA Astrophysics Data System (ADS)

In this work, the adsorption-desorption kinetic in the framework of the lattice gas model is analyzed. The transition probabilities are written as an expansion of the occupation configurations. Due to that, the detail balance principle determine half of the adsorption Ai and desorption Di coefficients, consequently, different functional relations between them are proposed. Introducing additional constrains, it is demonstrated that when those coefficients are linearly related through a parameter ? , there are values of lateral interaction V , that lead to anomalous behavior in the adsorption isotherms, the sticking coefficient and the thermal programmed desorption spectra. Diagrams for the allowed values of V and ? are also shown. Alternatively, a more reliable formulation for the adsorption desorption kinetic based on the transition state theory is introduced. In such way the equilibrium and non equilibrium observables do not present anomalous or inconsistent behavior.

Manzi, S. J.; Belardinelli, R. E.; Costanza, G.; Pereyra, V. D.

2009-02-01

83

Adsorption and desorption behavior of n-butane and isobutane on Pt(111) and Sn/Pt(111) surface alloys  

SciTech Connect

The adsorption/desorption behavior of n-butane and isobutane on Pt(111) and the p(2[times]2) Sn/Pr(111) and ([radical]3[times] [radical]3)R30[degrees] Sn/Pt(111) surface alloys has been examine using a combination of adsorption kinetics measurements utilizing a collimated molecular beam and temperature programmed desorption (TPD) mass spectroscopy. Initial sticking probabilities for both molecules on Pt(111) and the surface alloys at temperatures below the monolayer desorption threshold are essentially unity (S[sub 0] [>=] 0.95). The monolayer saturation coverages of n-butane and isobutane were also independent of the amount of Sn in the surface layer. The desorption activation energies measured by TPD for the monolayer states of both n-butane and isobutane progressively decrease by 5-8 kJ/mol compared to Pt(111) as the surface concentration of Sn increases from 0.25 to 0.33 atom fraction in the respective surface alloys. The decrease in the desorption activation energy scales linearly with the Sn concentration. No thermal decomposition of either molecule on any surface occurred during TPD measurements. Molecular interactions probed by adsorption and desorption of saturated C[sub 4] hydrocarbons are not influenced as strongly by the presence of Sn in the Pt(111) surface as previously observed for unsaturated molecules, such as ethylene and isobutylene. 30 refs., 9 figs.

Xu, C.; Koel, B.E. (Univ. of Southern California, Los Angeles, CA (United States)); Paffett, M.T. (Los Alamos National Lab., NM (United States))

1994-01-01

84

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

Microsoft Academic Search

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

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

2005-01-01

85

Measurement of Xe desorption rates from Pt(111): Rates for an ideal surface and in the defect-dominated regime  

NASA Astrophysics Data System (ADS)

The rate of thermal desorption of Xe from a Pt(111) surface has been measured over a range of 7 orders of magnitude using a combination of molecular-beam techniques. Rates up to ˜104 s-1, corresponding to residence times as short as 100 ?s, were extracted from the time-of-arrival distributions for atoms leaving the surface after short Xe beam pulses were applied. Rates as low as 10-3 s-1 were measured using a time-delayed flash-desorption technique. For intermediate rates, the transient decay of the desorbing Xe was recorded directly following the closing of a beam shutter. Temperature programmed desorption (TPD) spectra show first-order desorption kinetics and also reveal the presence of ``defect'' sites with substantially higher Xe binding energy which dominate the desorption kinetics at low coverages (below 0.005 Xe monolayers). These defects can be specifically saturated with CO molecules, permitting the measurement of rates characteristic of an ideal Pt(111) surface. An Arrhenius plot of these desorption rates is found to be linear over the entire range covered (80-160 K), giving an adsorption energy, ??, of 245±15 meV and a preexponential, ?, of 14+24-8 ×1011 s-1. In contrast, a similar plot for rates which are controlled by the presence of defect sites gives ??=410±40 meV and ?=9+40-8 ×1015 s-1. A desorption model including the effect of defects is developed which relates the desorption rate to the microscopic behavior of Xe atoms on terraces and at defects. This model leads to an estimate for the preexponential factor for defect-dominated desorption which is quite consistent with the very large measured value, and allows the simulation of TPD spectra and isothermal coverage decay curves, which involve coverages both higher and lower than the defect-site density.

Rettner, C. T.; Bethune, D. S.; Schweizer, E. K.

1990-01-01

86

Thermal reaction and desorption behaviors of 2,5-diiodothiophene on clean and passivated Au surfaces  

NASA Astrophysics Data System (ADS)

Thermal reactions and desorption behaviors of 2,5-diiodothiophene on Au were studied with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Diiodo-substituted hetero-cyclic molecules are an important precursor molecule for photochemical production of conjugated polymers. This paper describes the surface reactions and multilayer structure of 2,5-diiodothiophene in the absence of photon irradiation. 2,5-Diiodothiophene adsorbs molecularly on Au at 100 K. At 200-300 K, the C-I bond of the molecule dissociates producing atomic iodine. The C-I bond cleavage appears to induce further dissociation of the thiophene ring structure. The iodine species desorb at 600-750 K from the surface. The dissociated carbon and sulfur remain on the Au surface even at 800 K. The desorption of thin multilayers occurs at ˜220 K. During the desorption of these layers, a clustering process seems to occur. The desorption of thick multilayer occurs at ˜235 K.

Liu, Guangming; Ryoo, Kunkul; Kim, Seong H.

2007-07-01

87

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

SciTech Connect

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

Taylor-Pashow, K.; Hobbs, D.

2011-06-10

88

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 ...

89

Program for an improved hypersonic temperature-sensing probe  

NASA Technical Reports Server (NTRS)

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

Reilly, Richard J.

1993-01-01

90

Computer Program for Calculating the Temperature Field of Face Seals  

NASA Technical Reports Server (NTRS)

FORTRAN 4 program for use on IBM 7094 computer for calculating temperature field of shaft seals is described. Shaft seals are composed of basically axisymmetric bodies. Cylindrical coordinate system is used as basis for analysis. Program is quite general and can be applied to variety of axisymmetric body problems.

Russell, T. E.; Allen, G. P.; Ludwig, L. P.; Johnson, R. L.

1972-01-01

91

Adsorbate order-disorder effects on recombinative thermal desorption: Equivalence between dynamic Monte Carlo simulations and self-consistent cluster approximations  

NASA Astrophysics Data System (ADS)

The thermally activated desorption of dissociated diatomic species from a metallic surface is described as a lattice-gas problem on a square lattice with nearest- and next-nearest neighbor interactions between the adsorbates and investigated within dynamic Monte Carlo simulations. In the limit of fast diffusion with respect to desorption, it can be shown that the desorption rate depends directly on the local order induced by the interactions within the adsorbate layer. Therefore, by employing an appropriate quasi-equilibrium cluster approximation for the local order (beyond the quasi-chemical approximation), a differential equation can be derived that depends on self-consistently calculated structure forms, reproducing quantitatively the temperature-programmed desorption spectra simulated with the Monte Carlo procedure. In this way it can be shown that the time evolution obtained from the dynamic Monte Carlo algorithm is indeed "correct,'' and on the other hand, that it can be successfully substituted by a "cheaper'' cluster approximation.

Weinketz, Sieghard; Cabrera, G. G.

1997-01-01

92

Progress in BNL High-Temperature Hydrogen Combustion Research Program  

Microsoft Academic Search

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

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

1992-01-01

93

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

94

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

NASA Technical Reports Server (NTRS)

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

Gray, Hugh R.; Ginty, Carol A.

1992-01-01

95

Diffusion Analysis Of Hydrogen-Desorption Measurements  

NASA Technical Reports Server (NTRS)

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

Danford, Merlin D.

1988-01-01

96

Moisture Absorption and Desorption of Composite Materials  

Microsoft Academic Search

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

Chi-Hung Shen; George S. Springer

1976-01-01

97

Hydrogen desorption behavior of vanadium borohydride synthesized by modified mechano-chemical process  

Microsoft Academic Search

The vanadium borohydride was synthesized by a mechano-chemical milling method and its hydrogen desorption performance was evaluated. The effect of cooling during milling process on the hydrogen desorption behavior was also investigated. Nearly pure hydrogen was detected using a mass spectrometer coupled with a simultaneous thermal analyzer. Thermogravimetric method was conducted to determine the initial desorption temperature and the amount

Cheng-Hsien Yang; Wen-Ta Tsai; Jeng-Kuei Chang

2011-01-01

98

Adsorption and desorption of CO on Pt(1 1 1): a comprehensive analysis  

NASA Astrophysics Data System (ADS)

A comprehensive theory of the adsorption of CO on Pt(1 1 1) is developed to describe equilibrium properties as well as the adsorption and desorption kinetics. The basis is a multi-site lattice gas model which allows for adsorption at on-top and bridge sites, and includes site exclusion and lateral interactions out to second neighbour unit cells as well as a mean field to account for long ranged dipolar interactions between CO molecules. The theory reproduces the coverage and temperature dependence of pressure isotherms, partial coverages, heat of adsorption, total sticking coefficients, and isothermal and temperature-programmed desorption rates. The quality of the fits and the internal consistency of the theory are such that a number of minor inconsistencies in available experimental data can be identified and discussed.

McEwen, J.-S.; Payne, S. H.; Kreuzer, H. J.; Kinne, M.; Denecke, R.; Steinrück, H.-P.

2003-11-01

99

COMPOUND IDENTIFICATION IN ORGANIC AEROSOLS USING TEMPERATURE-PROGRAMMED THERMAL DESORPTION PARTICLE BEAM MASS SPECTROMETRY. (R826235)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

100

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

101

n-alkanes on MgO(100). II. Chain length dependence of kinetic desorption parameters for small n-alkanes.  

PubMed

Coverage-dependent desorption-kinetics parameters are obtained from high-quality temperature-programmed desorption data for seven small n-alkane molecules on MgO(100). The molecules, CNH2N+2 (N=1-4,6,8,10), were each studied for a set of 29 initial coverages at a heating ramp rate of 0.6 K/s as well as at a set of nine ramp rates in the range of 0.3-10.0 K/s. The inversion analysis method with its least-squares preexponential factor (prefactor) optimization discussed in the accompanying article is applied to these data. This method allows for accurate determination of prefactors and coverage-dependent desorption energies. The prefactor for desorption increases dramatically with chain length from 10(13.1) to 10(19.1) s(-1) over the range of N=1-10. We show that this increase can be physically justified by considering the increase in rotational entropy available to the molecules in the gaslike transition state for desorption. The desorption energy increases with chain length as Ed(N)=6.5+7.1N, which implies an incremental increase of 7.1+/-0.2 kJ/mol per CH2. PMID:15945700

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

2005-04-22

102

Mercury compounds characterization by thermal desorption.  

PubMed

The ability to accurately determine metal mercury content and identify different mercury species in solid samples is essential for developing remediation and control strategies. The aim of the present study is to characterize mercury compounds based on thermal desorption. For this purpose a series of samples was prepared and the operational parameters-heating velocity, carrier gas-were optimized. Fifteen commercial mercury compounds were analyzed for use as fingerprints. The results of the study show that the identification of mercury species by the method of thermal desorption is possible. The temperature of desorption increased according to the following order HgI2desorption curve shows that recoveries of 79-104% for HgS can be estimated. The proposed method represents a significant step forward in direct mercury analysis in solid samples. PMID:23953477

Rumayor, M; Diaz-Somoano, M; Lopez-Anton, M A; Martinez-Tarazona, M R

2013-09-30

103

Desorption of metal atoms with laser light: Mechanistic studies  

Microsoft Academic Search

Results on laser-induced desorption of metal atoms from small metal particles are presented. Experiments have been performed on sodium, potassium, and silver particles supported on a LiF(100) single-crystal surface under ultrahigh vacuum conditions. Measurements include the determination of the desorption rate as a function of laser wavelength, laser intensity, average particle size, and substrate temperature, the determination of the kinetic

W. Hoheisel; M. Vollmer; F. Träger

1993-01-01

104

Hydrogen on Pd(100)-S: the effect of sulfur on precursor mediated adsorption and desorption  

NASA Astrophysics Data System (ADS)

The influence of adsorbed sulfur on the adsorption and desorption of H 2 on Pd(100) was studied using temperature programmed desorption (TPD) for sulfur coverages (? S) from 0.00 to 0.35 ML. The saturation coverage (? H,sat) drops linearly with sulfur coverage, and above 0.28 ML of sulfur no hydrogen adsorbs. Direct site blocking is implied by the linear fall of ? H,sat with ? S, with each sulfur atom effectively blocking 3.7 ± 0.5 sites for hydrogen adsorption. The adsorption of H 2 on the sulfur free Pd(100) surface is best described by a second-order precursor model. When sulfur is added to the surface, however, the effect of the precursor state is diminished, and for ?S ? 0.15 hydrogen uptake is adequately modeled by secondrder direct adsorption. For low hydrogen coverages values for the activation energy and the preexponential factor for hydrogen adatom recombination drop in compensatory fashion from 85 {kJ}/{mol} and 10 -2.5{cm 2}/{s} on the sulfur free surface to 49 {kJ}/{mol} and 10 -6.8{cm 2}/{s} at ?S = 0.15, respectively. The effect of sulfur on the desorption kinetics of hydrogen suggests that the influence of adsorbed sulfur is more complex than simple site blocking. The compensation effect between the preexponential factor and the activation energy from surfaces with sulfur adlayers may arise from a more constrained transition state for desorption on sulfur covered surfaces or from a distribution of activation energies for desorption.

Burke, M. L.; Madix, R. J.

1990-11-01

105

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

SciTech Connect

Tykhon Zubkov, R. Scott Smith, Todd R. Engstrom, and Bruce D. Kay The adsorption, desorption, and diffusion kinetics of N2 on thick (up to ~9 mm) porous films of amorphous solid water (ASW) films were studied using molecular beam techniques and temperature programmed desorption (TPD). Porous ASW films were grown on Pt(111) at low temperature (<30 K) from a collimated H2O beam at glancing incident angles. In thin films (<1 mm), the desorption kinetics are well described by a model that assumes rapid and uniform N2 distribution throughout the film. In thicker films, (>1 mm), N2 adsorption at 27 K results in a non-uniform distribution where most of N2 is trapped in the outer region of the film. Redistribution of N2 can be induced by thermal annealing. The apparent activation energy for this process is ~7 kJ/mol, which is approximately half of the desorption activation energy at the corresponding coverage. Blocking adsorption sites near the film surface facilitates transport into the film. Despite the onset of limited diffusion, the adsorption kinetics are efficient, precursor-mediated and independent of film thickness. An adsorption mechanism is proposed, in which a high-coverage N2 front propagates into a pore by the rapid transport of physisorbed 2nd layer N2 species on top of the 1st layer chemisorbed layer.

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

2007-11-14

106

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction  

SciTech Connect

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

Song, Chunshan; Schobert, H.H.

1993-02-01

107

Adsorption and thermal desorption of fullerenes on the surface of a crystal  

NASA Astrophysics Data System (ADS)

A statistical theory of adsorption and thermal desorption of fullerenes in a multi-layer fullerite film on a crystal surface is developed. The equilibrium fullerene concentration is calculated as a function of temperature, film thickness, and energy constants of the system. The developing process of desorption with increase in temperature, which was observed experimentally, is validated.

Matysina, Z. A.; Zaginaichenko, S. Yu.; Schur, D. V.

2007-09-01

108

High temperature static strain gage alloy development program  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

109

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

110

Cooled High-temperature Radial Turbine Program 2  

NASA Technical Reports Server (NTRS)

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

Snyder, Philip H.

1991-01-01

111

Sestak–Berggren function in temperature-programmed reduction  

Microsoft Academic Search

From the peculiarities of Temperature-programmed reduction (TPR) method and using the Sestak–Berggren conversion function,\\u000a we describe first the TPR curve simulation procedure. The influence of the Sestak–Berggren exponents on the TPR peak maximum\\u000a and shape is demonstrated, by analyzing several synthetic TPR profiles. Finally, the kinetic parameters of Au\\/CeO2 promoted with yttrium as well as those of Au\\/CeO2–Al2O3 promoted with

G. Munteanu; E. Segal

2010-01-01

112

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

113

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

PubMed

There is enormous interest in visualizing the chemical composition of organic material that comprises our world. A convenient method to obtain molecular information with high spatial resolution is imaging mass spectrometry. However, the internal energy deposited within molecules upon transfer to the gas phase from a surface can lead to increased fragmentation and to complications in analysis of mass spectra. Here it is shown that in laser desorption with postionization by tunable vacuum ultraviolet (VUV) radiation, the internal energy gained during laser desorption leads to minimal fragmentation of DNA bases. The internal temperature of laser-desorbed triacontane molecules approaches 670 K, whereas the internal temperature of thymine is 800 K. A synchrotron-based VUV postionization technique for determining translational temperatures reveals that biomolecules have translational temperatures in the range of 216-346 K. The observed low translational temperatures as well as their decrease with increased desorption laser power is explained by collisional cooling. An example of imaging mass spectrometry on an organic polymer by using laser-desorption VUV postionization shows 5 ?m feature details while using a 30 ?m laser spot size and 7 ns pulse duration. Applications of laser-desorption postionization to the analysis of cellulose, lignin, and humic acids are briefly discussed. PMID:21976383

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

2011-11-01

114

The effect of varying oven temperatures and residence times on thermal desorption of n-hexane and 1-hexene from diffusive organic vapor dosimeters  

E-print Network

. Lawrence Vanell of Foxboro Analytical, Inc. for his technical advice concerning several aspects of the research. A special thanks goes to the 3M Company for their ex- treme generosity in donating the monitors used for this s tudv ~ Finally, I would... Temperatures Averaged Over Three Days and Three Residence Times 54 LIST OF FIGURES 1. Breakdown of 3M Organic Vapor Monitor 2. Removing Draft Shield and Retaining Ring from 3M Organic Vapor Monitor 3. Elutriation Cap in place on 3M Monitor 4. Inserting 3...

Steele, Kenneth Garnett

1981-01-01

115

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

116

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. TDS spectra of D2 from graphite and CFCs had previously not been thoroughly investigated. A desorption peak at approximately 1600 K was discovered in the TDS spectra for all samples heated with a linear ramp rate of 0.1 K/s. For an isotropic graphite, ISO-880U, four desorption peaks were recognized in the TDS spectra at approximately 660 K, 900 K, 1300 K, and 1600 K. These peaks were named as peaks 1, 2, 3, and 4 in order of increasing temperature. Major desorption peaks (i.e., peaks 3 and 4) were analyzed and discussed in detail. The temperature of peak 3 was dependent on the size of a graphite filler grain. The desorption process is suggested to be controlled by deuterium diffusion within the filler grain with a strong influence of trapping sites, where the migration takes place as a sequence of detrapping and retrapping. The desorption for peak 4 can be ascribed to the detrapping reaction from an interstitial cluster loop edge site. Activation energies were estimated from the peak shift by varying the heating rate of TDS to be 3.48 and 6.93 eV for peaks 3 and 4, respectively. Theoretical desorption curves for peaks 3 and 4 with the above mentioned activation energies were narrower than those for the experimental desorption curve. The observed peak broadening can be attributed to the effects of grain size and activation energy distributions.

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

2013-11-01

117

The desorption of molecular hydrogen from Si(100)-2×1 and Si(111)-7×7 surfaces at low coverages  

NASA Astrophysics Data System (ADS)

The mechanisms leading to desorption of molecular hydrogen from Si(100)-2×1 and Si(111)-7×7 surfaces have been elucidated and refined by detailed examination of the thermal desorption kinetics with particular emphasis on low and very low coverages. In the case of hydrogen desorption from Si(100)-2×1, a lattice-gas model incorporating the interactions that are responsible for pairing and clustering of adsorbed hydrogen atoms has been employed to fit temperature programmed desorption (TPD) peaks resulting from initial coverages between 0.01 and 1.0 monolayer (ML). From analysis of our low coverage data, we find that the pairing and clustering energies are (3.2±0.3) kcal mol-1 and (3.4±0.5) kcal mol-1, respectively. A subtle shift of the TPD peak maximum position as the initial coverage increases from 0.2 to 1.0 ML indicates that the pre-exponential factor and activation energy are weakly coverage dependent. We discuss how this is consistent with coupling of a dihydridelike transition state to its neighbors. The rate of molecular hydrogen desorption from Si(111)-7×7 is found to be very nearly second order in total hydrogen coverage when the initial coverage is low. This result is consistent with a two site model involving preferential adsorption of hydrogen atoms at rest atom sites rather than adatom sites.

Flowers, Michael C.; Jonathan, Neville B. H.; Morris, Alan; Wright, Steven

1998-02-01

118

Thermal desorption for passive dosimeter  

E-print Network

for Occupa- tional Safety and Health (NIQSH). ~ This method involves adsorption of the conteminants in a collection tube con- taining two separate portions of activated charcoal and subsequent desorption with carbon disulfide, followed by gas... popular for area and personal monitoring. However, as with the sorbent tube, a desorbing agent must be used to desorb the sorbate for analysis in its original form. Carbon disulfide, which is most frequently recommended by NIOSH for solvent desorption...

Liu, Wen-Chen

1981-01-01

119

Ion Desorption Stability in Superconducting High Energy Physics Proton Colliders  

SciTech Connect

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

Turner, W.C.

1995-05-29

120

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

SciTech Connect

Accurately estimating tritium retention in plasma facing components (PFCs) and minimizing its uncertainty are key safety issues for licensing future fusion power reactors. D-T fusion reactions produce 14.1 MeV neutrons that activate PFCs and create radiation defects throughout the bulk of the material of these components. Recent studies show that tritium migrates and is trapped in bulk (>> 10 µm) tungsten beyond the detection range of nuclear reaction analysis technique [1-2], and thermal desorption spectroscopy (TDS) technique becomes the only established diagnostic that can reveal hydrogen isotope behavior in in bulk (>> 10 µm) tungsten. Radiation damage and its recovery mechanisms in neutron-irradiated tungsten are still poorly understood, and neutron-irradiation data of tungsten is very limited. In this paper, systematic investigations with repeated plasma exposures and thermal desorption are performed to study defect annealing and thermal desorption of deuterium in low dose neutron-irradiated tungsten. Three tungsten samples (99.99 at. % purity from A.L.M.T. Co., Japan) irradiated at High Flux Isotope Reactor at Oak Ridge National Laboratory were exposed to high flux (ion flux of (0.5-1.0)x1022 m-2s-1 and ion fluence of 1x1026 m-2) deuterium plasma at three different temperatures (100, 200, and 500 °C) in Tritium Plasma Experiment at Idaho National Laboratory. Subsequently, thermal desorption spectroscopy (TDS) was performed with a ramp rate of 10 °C/min up to 900 °C, and the samples were annealed at 900 °C for 0.5 hour. These procedures were repeated three (for 100 and 200 °C samples) and four (for 500 °C sample) times to uncover damage recovery mechanisms and its effects on deuterium behavior. The results show that deuterium retention decreases approximately 90, 75, and 66 % for 100, 200, and 500 °C, respectively after each annealing. When subjected to the same TDS recipe, the desorption temperature shifts from 800 °C to 600 °C after 1st annealing for the sample exposed to TPE at 500 °C. Tritium Migration Analysis Program (TMAP) analysis reveals that the detrapping energy decreases from 1.8 eV to 1.4 eV, indicating the changes in trapping mechanisms. This paper also summarizes deuterium behavior studies in HFIR neutron-irradiated tungsten under US-Japan TITAN program.

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

2014-05-01

121

Adsorption and desorption of HCl on ice  

SciTech Connect

It is now generally accepted that chemical reactions occurring on the surface of ice particles in polar stratospheric clouds (PSC`s) play a crucial role in the catalytic cycle of chlorine responsible for the ozone destruction. Pulsed molecular beam and mass spectrometric techniques are used to study the adsorption of hydrogen chloride on thin ice films at temperatures from 100 to 170 K. The adsorption and desorption of HCl from an ice surface is relevant to the polar stratosphere where it is thought that chlorine atoms are liberated from reservoir species such as HCl by heterogeneous reactions occurring on the surface of polar stratospheric clouds. The authors have measured the sticking coefficient for HCl at an incident translational energy of 0.09 eV on thin film ice surfaces using a modified version of the reflectivity technique of King and Wells. By modeling the HCl partial pressure versus time waveforms for surface temperatures of 100--125 K, they obtain a sticking coefficient of 0.91 {+-} 0.06. The model incorporates first-order HCl desorption and a loss term also first order in HCl. Fitted kinetic parameters are E{sub des} = 28 kJ/mol, {nu}{sub des} = 2 {times} 10{sup 14} s{sup {minus}1} for desorption and E{sub loss} = 21 kJ/mol, {nu}{sub loss} = 4 {times} 10{sup 11} s{sup {minus}1} for the loss. The loss may be associated with the onset of water diffusion on the ice surface and subsequent ionization or hydration of the HCl. The measured waveforms are inconsistent with diffusion of HCl into the bulk. The apparent reflectivity decreases substantially in the temperature range of 126 to 140 K. This decrease cannot be attributed to an increase in sticking coefficient, a phase change in the ice, or the formation of the hexahydrate state of HCl.

Isakson, M.J.; Sitz, G.O. [Univ. of Texas, Austin, TX (United States). Dept. of Physics] [Univ. of Texas, Austin, TX (United States). Dept. of Physics

1999-04-01

122

Dynamics of NF 3 in a condensed film on Au(1 1 1) as studied by electron-stimulated desorption  

NASA Astrophysics Data System (ADS)

We report a low-temperature dynamics study of condensed layers of NF 3 on Au(1 1 1) by time-of-flight electron-stimulated desorption ion angular distribution (TOF-ESDIAD), temperature-programmed desorption (TPD) and low-temperature scanning tunneling microscopy (LT-STM). Upon adsorption at 30 K, molecular NF 3 adsorption occurs first at the step edges and at minor terrace defect sites with the formation of 2D islands. Within the islands, NF 3 is adsorbed in an upright conformation via the nitrogen lone pair electrons projecting fluorine atoms away from the surface as judged by the presence of only a sharp F + central beam in the ESDIAD pattern. At higher coverages, 3D islands start to populate the surface. Electron bombardment of a thick NF 3 (˜6 ML) layer adsorbed on the Au(1 1 1) surface leads to emission of F +, N +, NF +, NF2+ and NF3+ ions as observed in the TOF-ESD distribution. Upon heating to ˜37 K, a sudden decrease of the NF2+ and NF3+ ion yield, which is not related to thermal desorption, is observed which reflects the surface migration of NF 3 molecules, leading to local thinning of the film. The thinning process occurs at the temperature of onset of molecular rotations and self-diffusion in the bulk NF 3 crystal. In this process, some NF 3 molecules move closer to the surface which results in higher efficiency for ion neutralization by the underlying metal surface. In the TPD spectra, the monolayer desorption is observed to begin at ˜65 K, exhibiting zero-order kinetics with an activation energy of 21 kJ/mol.

Rze?nicka, Izabela I.; Lee, Junseok; Yates, John T.

2006-10-01

123

Atomic Oxygen Desorption from an Amorphous Silicate Surface  

NASA Astrophysics Data System (ADS)

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

He, Jiao; Vidali, Gianfranco

2014-06-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

125

SUPERCONDUCTIVITY PROGRAM RESEARCH AND DEVELOPMENT High Temperature Superconductivity (HTS) is a technology with the potential  

E-print Network

#12;SUPERCONDUCTIVITY PROGRAM RESEARCH AND DEVELOPMENT High Temperature Superconductivity (HTS-of-way. The Department of Energy's efforts to advance High Temperature Superconductivity combine major national strengths: the Superconductivity Partnership Initiative (SPI), the 2nd Generation Wire Initiative

126

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

SciTech Connect

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

Not Available

2010-05-01

127

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

128

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

SciTech Connect

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

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

2014-07-17

129

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.

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

2013-07-01

130

Fatigue strength of model active gas turbine blades subjected to programmed temperature changes close to operating temperatures  

Microsoft Academic Search

Conclusions 1.The static tensile load leads to a sharp reduction of the amplitudes of the failure stress for the ZhS6K alloy at higher temperatures.2.Under steady temperature conditions and sign-constant tensile cyclic loading the difference in fatigue strength and life between testpieces and model blades is insignificant.3.With programmed temperature changes similar to those in operating gas turbine engines the fatigue strength

B. N. Sinaiskii

1971-01-01

131

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

SciTech Connect

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

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

2014-04-28

132

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

133

Coadsorption of oxygen, gold and carbon monoxide on Ru(0 0 0 1) and CO 2 formation: A thermal desorption study  

NASA Astrophysics Data System (ADS)

The coadsorption of O, Au and CO and CO a + O a reaction is studied on Ru(0 0 0 1) using temperature programmed desorption, Auger electron spectroscopy, and low energy electron diffraction. CO/CO 2 desorption is measured on surfaces with different oxygen coverages and varying concentrations of Au using isotopically labeled 13C 18O. There is no CO 2 formation from CO adsorbed on clean Ru(0 0 0 1) and O(2 × 1), but CO 2 forms on CO covered RuO x surfaces. We have observed CO 2 formation below room temperature on O(2 × 1) and RuO x surfaces covered by Au nanoparticles. The conversion from CO to CO 2 is found to be the highest over submonolayer Au films supported on RuO x suggesting a synergistic effect between catalytic Au nanoparticles and RuO 2 domains.

Wu, Qifei; Hrbek, Jan

2005-08-01

134

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

SciTech Connect

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

Shanahan, K; Jeffrey Holder, J

2006-07-10

135

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

SciTech Connect

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

Shanahan, K; Jeffrey Holder, J

2006-08-17

136

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

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

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

2013-01-01

137

Adsorption and thermal desorption of hollow and endohedral fullerenes on a free crystal surface  

NASA Astrophysics Data System (ADS)

A statistical theory of processes of adsorption and desorption of fullerenes on a crystal surface has been elaborated. The equilibrium concentration of a fullerene monolayer on a crystal and its temperature dependence have been estimated. Some regularities of adsorption and desorption processes have been studied. It has been found that they are determined by the temperature and the character of interaction between the fullerene molecules and between the fullerene molecules and metal atoms. The results of calculations have been compared with experimental data.

Matysina, Z. A.; Zaginaichenko, S. Yu.; Shchur, D. V.; Mil'to, O. V.

2008-03-01

138

A comparative study of in- and post-source decays of peptide and preformed ions in matrix-assisted laser desorption ionization time-of-flight mass spectrometry: Effective temperature and matrix effect  

Microsoft Academic Search

In-source decay (ISD) and post-source decay (PSD) of a peptide ion ([Y6 + H]+) and a preformed ion (benzyltriphenylphosphonium, BTPP) generated by matrix-assisted laser desorption ionization (MALDI)\\u000a were investigated with time-of-flight mass spectrometry. ?-Cyano-4-hydroxycinammic acid (CHCA) and 2,5-dihydroxybenzoic acid\\u000a (DHB) were used as matrices. For both ions, ISD yield was unaffected by delay time, indicating rapid termination of ISD. This

So Hee Yoon; Jeong Hee Moon; Myung Soo Kim

2010-01-01

139

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

NASA Astrophysics Data System (ADS)

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

Adnadjevic, Borivoj; Lazarevic, Natasa; Jovanovic, Jelena

2010-12-01

140

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

141

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

142

Air separation with temperature and pressure swing  

DOEpatents

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

Cassano, Anthony A. (Allentown, PA)

1986-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

144

DESORPTION OF PYRETHROIDS FROM SUSPENDED SOLIDS  

PubMed Central

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

Fojut, Tessa L.; Young, Thomas M.

2014-01-01

145

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

146

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

147

Structure and desorption energetics of ultrathin D2O ice overlayers on serine- and serinephosphate-terminated self-assembled monolayers.  

PubMed

This paper reports on the structure and desorption dynamics of thin D2O ice overlayers (0.2-10 monolayers) deposited on serine- and serinephosphate- (with H+, Na+, Ca2+ counterions) terminated self-assembled monolayers (SAMs). The D2O ice overlayers are deposited on the SAMs at approximately 85 K in ultrahigh vacuum and characterized with infrared reflection absorption spectroscopy (IRAS). Reflection absorption (RA) spectra obtained at sub-monolayer D2O coverage reveal that surface modes, e.g. free dangling OD stretch, dominate on the serine SAM surface, whereas vibrational modes characteristic for bulk ice are more prominent on the serinephosphate SAMs. Temperature programmed desorption mass spectrometry (TPD-MS) and TPD-IRAS are subsequently used to investigate the energetics and the structural transitions occurring in the ice overlayer during temperature ramping. D2O ice (approximately 2.5 monolayers) on the serine SAMs undergoes a gradual change from an amorphous- to a crystalline-like phase upon increasing the substrate temperature. This transition is not as pronounced on the serine phosphate SAM most likely because of reduced mobility due to strong pinning to the surface. We show also that the energy of desorption for a sub-monolayer of D2O ice on serinephosphate SAM surfaces with a Na+ and Ca2+ counterions is equally high or even exceeds previously reported values for analogous high-energy SAMs. PMID:16471735

Ostblom, Mattias; Ekeroth, Johan; Konradsson, Peter; Liedberg, Bo

2006-02-01

148

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

149

Multiyear Program Plan for the High Temperature Materials Laboratory  

Microsoft Academic Search

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

Arvid E. Pasto

2000-01-01

150

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

SciTech Connect

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

Pasto, Arvid [ORNL

2007-08-01

151

Tritium release and trapping in austenitic stainless steels: Role of microstructure and desorption anneal  

SciTech Connect

The behavior of hydrogen and its isotopes in materials is a major concern in future nuclear systems both for the predictive analysis of the role of H, D, T in the environmental degradation of structural materials, for the confinement and inventory of tritium, and for the management of tritiated wastes. This study is focused on the characterization of the effect of the alloy microstructure, of desorption anneal and of oxide films on the tritium behavior (desorption kinetics, trapping, residual concentration) in various austenitic stainless steels. Different techniques (high temperature extraction of hydrogen, beta counting of tritium in massive samples) were used to study: the tritium absorption and desorption in several stainless steels, the role of the annealing conditions (temperature/time) on the tritium residual concentration and desorption flow, and the role of microstructural defects and of oxide films on the diffusion and trapping of tritium. (authors)

Chene, J. [CNRS/CEA, UMR 8587, CEA Saclay, Gif sur Yvette, F91191 (France); Trabuc, P.; Gastaldi, O. [Association Euratom-CEA Cadarache, DTN/STPA/LPC, Saint Paul Lez Durance, F13108 (France)

2008-07-15

152

Low energy electron stimulated desorption from DNA films dosed with oxygen  

PubMed Central

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 O2. The OH? desorption yields increase markedly with exposure to O2 at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O?, attributable to dissociative electron attachment to trapped O2 molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O2 shows that this surprising increase in OH? desorption, at elevated temperatures, arises from the reaction of O2 with damaged DNA sites. These results thus appear to be a manifestation of the so-called “oxygen fixation” effect, well known in radiobiology. PMID:22779623

Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Cloutier, Pierre; Massey, Sylvain; Sanche, Léon

2013-01-01

153

Organic solvent desorption from two tegafur polymorphs.  

PubMed

Desorption behavior of 8 different solvents from ? and ? tegafur (5-fluoro-1-(tetrahydro-2-furyl)uracil) has been studied in this work. Solvent desorption from samples stored at 95% and 50% relative solvent vapor pressure was studied in isothermal conditions at 30 °C. The results of this study demonstrated that: solvent desorption rate did not differ significantly for both phases; solvent desorption in all cases occurred faster from samples with the largest particle size; and solvent desorption in most cases occurred in two steps. Structure differences and their surface properties were not of great importance on the solvent desorption rates because the main factor affecting desorption rate was sample particle size and sample morphology. Inspection of the structure packing showed that solvent desorption rate and amount of solvent adsorbed were mainly affected by surface molecule arrangement and ability to form short contacts between solvent molecule electron donor groups and freely accessible tegafur tetrahydrofuran group hydrogens, as well as between solvents molecule proton donor groups and fluorouracil ring carbonyl and fluoro groups. Solvent desorption rates of acetone, acetonitrile, ethyl acetate and tetrahydrofuran multilayers from ? and ? tegafur were approximately 30 times higher than those of solvent monolayers. Scanning electron micrographs showed that sample storage in solvent vapor atmosphere promotes small tegafur particles recrystallization to larger particles. PMID:24060368

Bobrovs, Raitis; Acti?š, Andris

2013-11-30

154

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

155

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

156

Molecular bean studies of adsorption, desorption, and diffusion kinetics in nanoscale ice films  

SciTech Connect

Heterogeneous gas/solid chemistry involving terrestrial ice particles and polar stratospheric clouds (PSCs) plays a critical role in determining the composition of the atmosphere. Unfortunately, a detailed predictive understanding of the elementary dynamical and kinetic process occurring on the surface of atmospheric particulates is presently unavailable. Molecular beam scattering and programmed desorption (both TPD, and isothermal) are used to study the adsorption, desorption, phase transition, and diffusion kinetics in nanoscale multilayer ice films. Sticking coefficients of H{sub 2}O, HCl, and NH{sub 3} are determined as a function of incident kinetic energy, angle and surface temperature. The branching between molecular and dissociative ({open_quotes}salvation{close_quotes}) chemisorption is probed by detecting isotopic exchange between the adsorbate and substrate. In related experiments, molecular beams of various reagents are used to create multicomponent thin films of varying composition and morphology with layer-by-layer atomic resolution. The experimental methods, results, and their relevance to heterogeneous environmental chemistry will be presented.

Smith, S.; Huang, C.; Stirniman, M.J. [Pacific Northwest National Lab., Richland, WA (United States)

1996-10-01

157

Temperature  

NSDL National Science Digital Library

This topic in depth begins with the About Temperature (1) Web site, written by Beverly T. Lynds of Unidata, which is a program that works to enable university researchers and educators to acquire and use atmospheric and related data. The one-page site explains what temperature is, the development of thermometers, heat and thermodynamics, and other related topics. The second site is maintained by the University of Execter's Centre for Innovation in Mathematics Teaching. Actually an online tool called Conversion Calculator for Units of Temperature (2), the site allows users to type in any value, choose a significant figure, press "convert it," and get that value in Kelvin, Celsius, Fahrenheit, r'aumur, and rankine units. The next site is a lesson plan from AskEric.com entitled Temperature: Is it Hot or Cold? (3). Written for 2nd graders, the lesson demonstrates to how to read thermometers, determine their rise or fall, record temperatures, and take temperatures of various items. The fourth site, Surface Temperature Analysis (4), is presented by NASA's Goddard Institute for Space Studies. Here, visitors can view graphs, maps, animations, and station data of global surface temperatures. For example, the animation covers 12-month means from 1971 to 1999. The History Behind the Thermometer (5) Web site, from About.com, explores what a thermometer is, how it works, and how it came into being. The sixth site, entitled Science Shack (6) and offered by the BBC, answers the question, Why do we have two different temperature scales, Celsius and Fahrenheit? The site explains how to create your own thermometer like Galileo's, tells how it works, and why we use other types today. The next site is provided by National Oceanic and Atmospheric Administration (NOAA) and presents US State temperature extremes and drought information (7). Visitors can see all-time temperature maximums and minimums by state, monthly temperatures by state, and more. The last site is an all-inclusive temperature site called Temperature World (8). Everything from news, science, organizations, general interest, games, and more -- all related to temperature -- can be found here.

Brieske, Joel A.

158

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

NASA Astrophysics Data System (ADS)

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

Yougoubare, Y. Quentin; Pang, Su-Seng

2014-02-01

159

Adsorption/desorption hysteresis in the adsorption isotherms for Kr and Xe on exfoliated graphite  

NASA Astrophysics Data System (ADS)

The adsorption/desorption hysteresis which appears in the adsorption isotherm for Kr physisorbed on exfoliated graphite has a very characteristic feature. A sharp transition at the termination of the hysteresis in the desorption branch of the isotherm suggests a first-order phase transition. The temperature dependence of the hysteresis for Kr and Xe on exfoliated graphite was investigated. The origin of the hysteresis of Kr is thought to be capillary condensation accompanied by a liquid-solid phase transition.

Kosugi, T.; Usui, Y.; Arakawa, I.

1993-05-01

160

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

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

161

Laboratory simulations of pre-cometary ice processes: thermal desorption, UV and X-ray irradiation.  

NASA Astrophysics Data System (ADS)

The formation of ice mantles on pre-cometary dust grains was simulated experimentally under ultrahigh vacuum conditions. An ice mixture containing H2O, CO, CO2, CH3OH, and NH3 was deposited at 8 K. The ice layer was either irradiated by UV or X-rays, or warmed up in a controlled way. The ice was monitored by infrared spectroscopy in transmittance and the species in the gas phase were detected by quadrupole mass spectroscopy (QMS). The temperature programmed desorption (TPD) of a complex ice mixture with up to five molecular components can aid to interpret the data collected by mass spectrometers on board cometary missions like Rosetta during the flyby. The irradiation experiments led to the formation of many photo-products. We will focus on those made by irradiation of ices containing H2S to study the formation of the detected sulfurbearing species in comets, such as S2.

Muñoz Caro, G. M.; Bueno-López, J.; Jiménez-Escobar, A.; Cruz-Diaz, G. A.; Chen, Y.-J.; Ciaravella, A.; Cecchi-Pestellini, C.; Goesmann, F.

2012-09-01

162

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

163

Sulphur group analysis in solid matrices by atmospheric pressure-temperature programmed reduction  

Microsoft Academic Search

The atmospheric pressure-temperature programmed reduction (AP-TPR) has become an established and reliable method amongst the different sulphur characterisation techniques for solid materials, like coal and coal derived products, rubber and clay. The analytical method is based upon the fact that specific sulphur functional groups are hydrogenated at specific temperatures. During the last few years, several adjustments have been made to

Jan Yperman; Inge I. Maes; Heidi Van den Rul; Steven Mullens; Joke Van Aelst; Dirk V. Franco; Jules Mullens; Lucien C. Van Poucke

1999-01-01

164

A BASIC program to calculate the temperature variation of mineral-growth rates  

NASA Astrophysics Data System (ADS)

A BASIC program is presented for the calculation of the complete temperature variation of mineral-growth rates based on partial data. The algorithm is derived from a corresponding states equation for crystal growth, together with a compensation relationship in the standard Arrhenius equation of growth rate vs temperature.

Dearnley, Ray

1994-12-01

165

Dosimeter-Type NO[subscript x] Sensing Properties of KMnO[subscript 4] and Its Electrical Conductivity during Temperature Programmed Desorption  

E-print Network

An impedimetric NO[subscript x] dosimeter based on the NO[subscript x] sorption material KMnO[subscript 4] is proposed. In addition to its application as a low level NO[subscript x] dosimeter, KMnO[subscript 4] shows ...

Groß, Andrea

166

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

167

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

168

A control system for maintaining a predetermined temperature program  

E-print Network

LIBRARY II Ale COLLEGE OF TEXIIS A CONTROL SYSTEM PQB MAINTAI?INO A PBEDETEBMINED TKNPEBATUBE PBOGBAM Edmund Nelson Boots, Jr. A Thesis SulssIitted. to the Graduate Sshool of The Agricultural end Meehaniesl Coils;". s of Texas Partial... FulfillIIIent of the RequlreqIents for ths Degree of Ma)or Sule)eet: Eleetrisal Engineering May& 1/56 A CONTROL SYSTEM FOR MAINTAININ6 A PREDETERMINED TEMPERATURE PRGSRAM By Edmund Nelson Roots, Jr. P ovsd aa to Style and Content: (E~i's, ;, g...

Roots, Edmund Nelson

1956-01-01

169

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

NASA Technical Reports Server (NTRS)

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

Cassenti, B. N.

1983-01-01

170

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

171

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. PMID:22269298

2012-01-01

172

Energetic particle induced desorption of water vapor cryo-condensate  

SciTech Connect

An in-vessel cryo-condensation pump is being designed for the Advanced Divertor configuration of the DIII-D tokamak. To assess the importance of possible desorption of water vapor from the cryogenic surfaces of the pump due to impingement of energetic particles from the plasma, a 77 K surface on which a thin layer of water vapor was condensed was exposed to a tenuous plasma (density = 2 {times} 10{sup 10} cm{sup {minus}3}, electron temperature = 3 eV). Significant desorption of the condensate occurred, suggesting that impingement of energeticparticles (10 eV) at flux levels of {approximately}10{sup 16} cm{sup 2}s{sup {minus}1} on cryogenic surfaces could potentially induce impurity problems in the tokamak plasma. A pumping configuration is presented in which this problem is minimized without sacrificing the pumping speed.

Menon, M.M.; Owen, L.W.; Simpkins, J.E.; Uckan, T.; Mioduszewski, P.K.

1990-01-01

173

High temperature thermocouple development program, part A and part B  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

174

Column Selectivity Programming and Fast Temperature Programming for High-Speed GC Analysis of Purgeable Organic Compounds.  

PubMed

High-speed gas chromatograms are obtained by the use of relatively short lengths of capillary column operated at relatively large carrier gas flow rates. This approach is difficult for more complex mixtures because of the reduced peak capacity available with shorter columns. A solution to this problem is the use of tunable column ensembles consisting of the series (tandem) combination of a polar and a nonpolar column. By adjusting the pressure at the junction point between the columns, the selectivity of the ensemble can be adjusted within the limits imposed by the individual columns. For mixtures representing a relatively large boiling point range and containing more than ?20 components, high-speed, isothermal separations are less effective. These limitations are significantly reduced by combining fast temperature programming with selectivity programming. Selectivity programming is obtained by changing the pressure at the column junction point one or more times during the course of an analysis. In the work described here, the column ensemble temperature and the junction pressure are initially set to give a high-quality separation of the earliest eluting components. After these components have eluted, a linear temperature ramp of ?35 °C/min is initiated. As the temperature increases, the pressure is adjusted to change the selectivity and thus facilitate the separation of groups of components as they migrate through the column ensemble. Using this approach, a mixture of 30 purgeable organic compounds is separated in less than 2.5 min. PMID:21644677

Smith, H; Sacks, R D

1998-12-01

175

Effect of extraction procedure and gas chromatography temperature program on discrimination of MDMA exhibits.  

PubMed

Analysis of impurities in seized MDMA tablets can be used to determine the synthesis method used and to identify links among exhibits. However, no standardized method exists to generate impurity profiles, limiting comparisons among different laboratories. This research investigated the effect of extraction procedure and gas chromatography temperature program on the resulting impurity profiles. Five exhibits were extracted using liquid–liquid extraction (LLE) and headspace solid-phase microextraction (HS-SPME), then analyzed using two different temperature programs. Profiles were statistically assessed using principal components analysis. While LLE was more reproducible, more compounds were extracted using HS-SPME, thus providing more informative chemical profiles. The longer temperature program (53 min vs. 36 min) allowed greater discrimination of exhibits, due to improved precision as a result of an extended hold time (12 min). This research further highlights the need for standardized extraction and analysis procedures to allow comparison of chemical profiles generated in different laboratories. PMID:24745074

McManaman, Karlie M; Smith, Ruth Waddell

2014-03-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

177

Desorption induced by multiple electronic transitions  

NASA Astrophysics Data System (ADS)

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

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

1992-06-01

178

Water-cooled end-point boundary temperature control of hot strip via dynamic programming  

SciTech Connect

In this paper, an end-point boundary temperature control approach for runout table cooling used in hot strip mills is presented. The system relies on a linearized model for describing heat radiated to the environment and heat transferred to cooling water. At first, a conventional feedforward control design to control the temperature at the end-point boundary, the only measurable controlled parameter, is presented. Subsequently, a modified control scheme which uses dynamic programming to minimize the temperature error at the end-point boundary is discussed in detail. System performance analysis via simulation is presented for both control schemes. Simulation results show that temperature error minimization by dynamic programming improves system performance.

Samaras, N.S. [Danieli Automation, Pittsburgh, PA (United States)] [Danieli Automation, Pittsburgh, PA (United States); Simaan, M.A. [Univ. of Pittsburgh, PA (United States). Dept. of Electrical Engineering] [Univ. of Pittsburgh, PA (United States). Dept. of Electrical Engineering

1998-11-01

179

Temperature Control in Cement Rotary Kiln with Neural Network-Based Heuristic Dynamic Programming  

Microsoft Academic Search

During the production process of modern cement industry, the rotary kiln is the key equipment .The temperature of cement rotary\\u000a kiln is a large lag, large inertia, complex nonlinear controlled object. There are many external factors influencing the temperature,\\u000a and there exist coupling and uncertainties among various factors. Approximate Dynamic Programming (ADP) is an on line control\\u000a approach that based

Xiaofeng Lin; Tangbo Liu; Deguang Cao; Qingbao Huang

2009-01-01

180

Water accommodation and desorption kinetics on ice.  

PubMed

The interaction of water vapor with ice remains incompletely understood despite its importance in environmental processes. A particular concern is the probability for water accommodation on the ice surface, for which results from earlier studies vary by more than 2 orders of magnitude. Here, we apply an environmental molecular beam method to directly determine water accommodation and desorption kinetics on ice. Short D2O gas pulses collide with H2O ice between 170 and 200 K, and a fraction of the adsorbed molecules desorbs within tens of milliseconds by first order kinetics. The bulk accommodation coefficient decreases nonlinearly with increasing temperature and reaches 0.41 ± 0.18 at 200 K. The kinetics are well described by a model wherein water molecules adsorb in a surface state from which they either desorb or become incorporated into the bulk ice structure. The weakly bound surface state affects water accommodation on the ice surface with important implications for atmospheric cloud processes. PMID:24814567

Kong, Xiangrui; Papagiannakopoulos, Panos; Thomson, Erik S; Markovi?, Nikola; Pettersson, Jan B C

2014-06-01

181

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

2009-10-12

182

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

183

Catalytic oxidation of propylene7. Use of temperature programmed reoxidation to characterize. gamma. -bismuth molybdate  

Microsoft Academic Search

Temperature-programed reoxidation of propylene-reduced ..gamma..-BiâMoOâ revealed a low-temperature peak (LTP) at 158°C and a high-temperature peak (HTP) at 340°C. Auger spectroscopy and X-ray diffraction of reduced and partially or completely reoxidized bismuth molybdate showed that at the LTP, molybdenum(IV) is oxidized to molybdenum(VI) and bismuth, from the metallic state to an oxidation state between zero and three, and that the

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

1980-01-01

184

How quality and quantity of organic matter affect polycyclic aromatic hydrocarbon desorption from Norwegian harbor sediments.  

PubMed

The desorption behavior of phenanthrene, pyrene, and benzo[a]pyrene was investigated for three Norwegian harbor sediments and their respective particle size fractions using the Tenax desorption method. Rate constants for rapidly, slowly, and very slowly desorbing fractions were on the order of 10(-1), 10(-2) to 10(-4), and 10(-4) to 10(-6)/h, respectively. Relatively small amounts were present in the rapidly desorbing fractions (F(rapid): < 6% for phenanthrene, 3-19% for pyrene, and 1-12% for benzo[a]pyrene). With the exception of benzo[a]pyrene, these F(rapid) values were generally lower than median F(rapid) values obtained from more than 100 literature values for native polycyclic aromatic hydrocarbons (PAHs) (22% for phenanthrene, 29% for pyrene, and 8% for benzo[a]pyrene). To understand which parameters influence PAH desorption, relations between desorption behavior and the sediment characteristics were investigated. A significant positive correlation was found between the extent of slow and very slow desorption and the ratios of black carbon to total organic carbon, as well as the temperature at which 50 and 90%, respectively, of the organic matter was oxidized, as obtained from oxidation-only Rock Eval analysis. Thus, black carbon-bound PAHs probably desorb slowly and very slowly. Furthermore, significant positive correlations between desorption behavior and the average particle size were observed, which could be explained by retarded intraparticle diffusion. PMID:16704056

Oen, Amy M P; Breedveld, Gijs D; Kalaitzidis, Stavros; Christanis, Kimon; Cornelissen, Gerard

2006-05-01

185

Evaluation of lead desorption from cement matrices  

Microsoft Academic Search

Desorption of lead immobilized into cement and concrete matrices was evaluated in the pH range between 4 and 8 within a period of 2 h to 15 days. Lead-desorbed content in aqueous milieu was monitored by Graphite Furnace Atomic Absorption Spectroscopy, while matrices were directly analyzed by X-ray photoelectronic spectroscopy or Rutherford Backscattering spectrometry. For low pH, higher Pb desorption

Angélica M. Gollmann; Aline Walesko; Adriano Fisch; Fernanda C. Stedile; Márcia Messias da Silva; João H. Z. dos Santos; Rafael M. Lattuada

2007-01-01

186

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

SciTech Connect

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

Scherwitzl, Boris, E-mail: b.scherwitzl@tugraz.at; Resel, Roland; Winkler, Adolf [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz (Austria)] [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz (Austria)

2014-05-14

187

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

2007-05-01

188

A control methodology for the feed water temperature to optimize SWRO desalination process using genetic programming  

Microsoft Academic Search

This paper presents a novel methodology to determine an optimized control method for feed water temperature in a seawater reverse osmosis (SWRO) desalination process using genetic programming (GP) which is an evolutionary algorithm used to find functional forms through training data. Two functional models were determined by GP with operation data collected over four years from Fujairah SWRO plant. The

Seung Joon Kim; Sanghoun Oh; Young Geun Lee; Moon Gu Jeon; In S. Kim; Joon Ha Kim

2009-01-01

189

Fast temperature programming in routine analysis of multiple pesticide residues in food matrices  

Microsoft Academic Search

Flash gas chromatographic (GC) analysis of 15 organophosphorus pesticides commonly occurring in food crops was performed using the Thermedics Detection EZ Flash upgrade kit installed in the oven of a HP 5890 Series II Plus gas chromatograph. The temperature program and splitless time period were the main parameters to be optimized. In the first set of experiments wheat matrix-matched standards

Kate?ina Maštovská; Jana Hajšlová; Michal Godula; Jitka K?ivánková; Vladim??r Kocourek

2001-01-01

190

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

191

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

NASA Technical Reports Server (NTRS)

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

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

1967-01-01

192

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

NASA Technical Reports Server (NTRS)

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

Hanley, David; Carella, John

1999-01-01

193

Hydrogen storage and desorption properties of Ni-dispersed carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report that the H2 storage method using Ni-mediated CNTs is a viable candidate for fuel cell applications. It is demonstrated that a single Ni coated on the carbon nanotubes' (CNT) surfaces can store up to 5 H2. In this respect, at high Ni-coverage, Ni-dispersed single-walled CNTs are considered to be capable of releasing ˜10wt.% H2 at around room temperature. Moreover, the H2 desorption barrier of 0.26eV/H2, corresponding to the desorption temperature of 328K, is ideal for fuel cell applications.

Lee, Jung Woo; Kim, Hyun Seok; Lee, Jai Young; Kang, Jeung Ku

2006-04-01

194

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

195

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

PubMed

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

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

2013-01-01

196

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

197

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

NASA Technical Reports Server (NTRS)

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

Purpura, P. T.

1983-01-01

198

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

199

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

200

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

SciTech Connect

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

Horner, M.W.

1980-12-01

201

Errors in evaluation of the kinetic parameters in temperature programmed reduction  

Microsoft Academic Search

The possibility to determine the kinetic parameters for temperature programmed reduction of Cu\\/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman’s iso-conversional method and another\\u000a one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti\\u000a and Baiker, the Friedman’s method, although gives values of

G. Munteanu; C. Miclea; E. Segal

2008-01-01

202

Evaluation of lead desorption from cement matrices.  

PubMed

Desorption of lead immobilized into cement and concrete matrices was evaluated in the pH range between 4 and 8 within a period of 2 h to 15 days. Lead-desorbed content in aqueous milieu was monitored by Graphite Furnace Atomic Absorption Spectroscopy, while matrices were directly analyzed by X-ray photoelectronic spectroscopy or Rutherford Backscattering spectrometry. For low pH, higher Pb desorption was observed, about 5-7 times higher than that measured in the case of concrete matrices. The inclusion of polyvinyl alcohol as a matrix modifier was evaluated through a factorial design. Polymer inclusion yielded a reduction in Pb desorption, but its effect cannot be justified in terms of the ability of this polymer to chelate the metal. The resulting modified matrices did not present toxicity to Daphnia magna. PMID:17616892

Gollmann, Angélica M; Walesko, Aline; Fisch, Adriano; Stedile, Fernanda C; da Silva, Márcia Messias; Dos Santos, João H Z; Lattuada, Rafael M

2007-07-01

203

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

SciTech Connect

An experimental, modeling and conceptual engineering analysis study has been performed to assess the feasibility of TRW's Programmed Temperature Gasification (PTG) concept for carbonizing caking coals without severe agglomeration. The concept involves control of carbonizing heating rate to maintain metaplast concentration at a level equal to or slightly below that which causes agglomeration. The experimental studies required the contruction of a novel programmed temperature, elevated pressure, hot stage video microscope for observation of coal particle changes during heating. This system was used to develop a minimum-time heating schedule capable of carbonizing the coal at elevated pressures in the presence of hydrogen without severe agglomeration. Isothermal fixed heating rate data for a series of coals were subsequently used to calibrate and verify the mathematical model for the PTG process. These results showed good correlation between experimental data and mathematical predictions. Commercial application of the PTG concept to batch, moving bed and fluid bed processing schemes was then evaluated. Based on the calibrated model programmed temperature gasification of the coal without severe agglomeration could be carried out on a commercial batch reaction in 4 to 12 minutes. The next step in development of the PTG concept for commercial application would require testing on a bench scale (3-inch diameter) gasifier coupled with a full commercial assessment to determine size and cost of various gasification units.

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

1980-11-30

204

ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS - THE THERMAL DESORPTION UNIT - APPLICATIONS ANALYSIS REPORT  

EPA Science Inventory

This report details the Superfund Innovative Technology Evaluation of the Eco Logic International's gas-phase chemical reduction process, with an emphasis on their thermal desorption unit. he Eco Logic process employs a high temperature reactor filled with hydrogen as a means to ...

205

Theory of direct scattering, trapping, and desorption in atom-surface collisions Guoqing Fan1  

E-print Network

Theory of direct scattering, trapping, and desorption in atom-surface collisions Guoqing Fan1 and J desorbs in a distribution at equilibrium with the surface temperature. In this paper a scattering theory is developed, using an iterative algorithm and classical mechanics for the collision process, which describes

Manson, Joseph R.

206

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

EPA Science Inventory

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

207

Activated and nonactivated desorption from polymer surfaces  

NASA Astrophysics Data System (ADS)

This dissertation addresses the interaction between dipolar molecular adsorbates and crystalline polymer surfaces. The goals were to investigate and compare the interactions of water with the ferroelectric copolymer poly(vinylidene fluoride (PVDF) -- trifluoroethylene (TrFE)) and poly(methylvinylidene-cyanide) (PMVC) a strongly dipole ordered polymer. As a reference, we also studied other dipolar molecular adsorbates such as bromoform and chloromethane, to further elucidate the interactions with P(VDF-TrFE). The study of adsorbate surface interactions on polymers is an emerging discipline, and still in infancy despite the long history of surface science. Our main focus is the water molecule as an adsorbed and absorbed dipolar molecule. The size of the molecule facilitates absorption on and desorption from the bulk of a crystalline polymer. We propose that on the microscopic scale, dipole interactions matter and affect the surface physical chemistry at the polymer surfaces, as does lattice strain caused by water absorption. Surface dipoles can affect the binding site of water species adsorbed at the surface and sterically hinder or enhance desorption of adsorbed or absorbed water. We find that perturbations of local surface dipoles can affect desorption of absorbed water and polymer lattice strain plays an important role. Prior studies have shown that the electronic structure of the ferroelectric P(VDF-TrFE) films is locally altered with incident UV radiation suggesting metastable excited states that may involve dipole reorientation. Light polarization dependent photo-assisted thermal desorption helps demonstrate that water desorption from surface and bulk can be influenced by the formation of electronic metastable states. Changes in local dipole orientation and the formation of long lived metastable states affect the strength of the coupling between the dipoles of water molecules and the dipoles of the copolymer P(VDF-TrFE). These effects were not observed for water absorption and adsorption on PMVC adding the necessary supporting evidence that dipole rotation can alter the desorption kinetics for absorbed water. The water desorption from PMVC is an intrinsically activated process by the strain in the polymer, while the water desorption from P(VDF-TrFE) is not. This suggests that dipole rotation in the polymer substrate may play a key role.

Ilie, Carolina Cristina

208

Temperature-programmed capillary electrophoresis for the analysis of high-melting point mutants in thalassemias.  

PubMed

The behavior of different sieving polymers for unambiguous determination of point mutations in genomic DNA, based on electrophoresis in thin capillaries, is evaluated. High melters from thalassemia patients are separated by exploiting the principle of denaturing gradient gel electrophoresis, in fact, of its variant utilizing temperature gradients (TGGE), along the migration path, encompassing the melting points of both homo- and heteroduplex, polymerase chain reaction (PCR)-amplified DNA fragments. Unlike TGGE, where the temperature gradient exists along the separation space, the denaturing temperature gradient in the fused-silica capillaries is time-programmed, so as to reach the Tm's of all species under analysis prior to electrophoretic transport past the detector window. The DNA fragments are injected in a capillary maintained (by combined chemical and thermal means) just below the expected Tm values. The deltaT applied is rather minute (1-1.5 degrees C) and the temperature gradient quite shallow (e.g., 0.05 degrees C/min). The denaturing thermal gradient is generated internally, via Joule heat produced by voltage ramps. This method is applied to the analysis of the most common point mutations in thalassemias, characterized by being high melters (in the temperature range of 60-62 degrees C) in presence of 6 M urea. Point mutants are fully resolved into a spectrum of four bands only when poly(N-acryloylaminopropanol) and hydroxyethylcellulose are used. However, the former offers the best separation capability at such high temperatures. PMID:9194597

Gelfi, C; Righetti, P G; Travi, M; Fattore, S

1997-05-01

209

The influence of defects and defect clusters on alkali atom desorption stimulated by low energy electron bombardment of alkali halides  

NASA Astrophysics Data System (ADS)

An important challenge in studies of electronically induced desorption on alkali halides is to determine the degree to which the desorption rate of alkali atoms as a function of dose and temperature is influenced by alkali island formation on the surface, alkali colloid formation in the bulk, and individual defect diffusion from the bulk to the surface. To address this problem, we report measurements of transmission optical absorption which gives direct information on defect, cluster and surface island concentrations, and of electron bombardment induced alkali desorption yields performed simultaneously on NaCl, NaF, and LiF at temperatures between 27 and 400°C. These experiments provide insight into the formation of surface and bulk agglomerates which in turn act as sources of desorbing alkali atoms. Our data support a physical picture where bombardment induced F-centers lead to the formation of F-center aggregates in the bulk and alkali metal clusters on the surface at temperatures around room temperature. At higher temperatures alkali metal desorption during electron bombardment is dominated by the emission of weakly bound single alkali atoms, and alkali atoms from alkali metal clusters on the surface of the crystals. After the cessation of the electron beam, the desorption yield is controlled by the thermal stability of metallic colloids which have been formed in the bulk during electron bombardment due to the temperature dependent higher mobility of the F-centers.

Seifert, N.; Ye, H.; Tolk, N.; Husinsky, W.; Betz, G.

1994-01-01

210

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

211

Testing program for determining the mechanical properties of concrete to temperatures of 621/sup 0/C  

SciTech Connect

Concrete temperatures in a Liquid Metal Fast Breeder Reactor (LMFBR) in excess of normal code limits can result from postulated large sodium spills in equipment cells. Elevated temperature concrete property data which may have application for providing a basis for the design and evaluation of such postulated accident conditions is limited. Data thus needed to be developed commensurate with LMFBR plant applications for critical physical and mechanical concrete properties under prototypic thermal accident conditions. A test program was conducted to define the variations in physical and mechanical properties of a limestone aggregate concrete and a lightweight insulating concrete exposed to elevated temperatures. Five test series were conducted: unconfined compression, shear, rebar bond, sustained loading (creep), and thermal properties. Testing procedures for determining the mechanical properties of concrete from ambient to 621/sup 0/C (1150/sup 0/F) are described. Ther thermal properties tests are discussed in a separate paper which is also being presented at this conference.

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

1980-01-01

212

Methane oxidation over SrCeO[sub 3] catalysts: Effect of solid-state reaction temperature  

Microsoft Academic Search

SrCeO[sub 3] catalysts were prepared by solid-state reaction at 750--1400 C. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and temperature-programmed desorption (TPD) of CO[sub 2]. The surface area of the catalysts decreased with increasing solid-state reaction temperature. The rate equation of the methane oxidation was obtained as r[sub CO[sub x

Hidetoshi Nagamoto; Eiji Shinoda; Hakuai Inoue

1993-01-01

213

Thermal Desorption/GCMS Analysis of Astrobiologically Relevant Organic Materials  

NASA Technical Reports Server (NTRS)

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

McDonald, Gene D.

2001-01-01

214

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

PubMed

Linear retention indices are commonly used to identify compounds in programmed-temperature gas chromatography (GC), but they are unreliable unless the original experimental conditions used to measure them are stringently reproduced. However, differences in many experimental conditions may be properly taken into account by calculating programmed-temperature retention times of compounds from their measured isothermal retention vs. temperature relationships. We call this approach "retention projection". Until now, retention projection has been impractical because it required very precise, meticulous measurement of the temperature vs. time and hold-up time vs. temperature profiles actually produced by a specific GC instrument to be accurate. Here we present a new, easy-to-use methodology to precisely measure those profiles: we spike a sample with 25 n-alkanes and use their measured, programmed-temperature retention times to precisely back-calculate what the instrument profiles must have been. Then, when we use those back-calculated profiles to project retention times of 63 chemically diverse compounds, we found that the projections are extremely accurate (e.g. to ±0.9 s in a 40 min ramp). They remained accurate with different temperature programs, GC instruments, inlet pressures, flow rates, and with columns taken from different batches of stationary phase while the accuracy of retention indices became worse the more the experimental conditions were changed from the original ones used to measure them. We also developed new, open-source software (http://www.retentionprediction.org/gc) to demonstrate the system. PMID:23040964

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

2012-11-01

215

Interlayer cohesive energy of graphite from thermal desorption of polyaromatic hydrocarbons  

NASA Astrophysics Data System (ADS)

We have studied the interaction of polyaromatic hydrocarbons (PAHs) with the basal plane of graphite using thermal desorption spectroscopy. Desorption kinetics of benzene, naphthalene, coronene, and ovalene at submonolayer coverages yield activation energies of 0.50 eV, 0.85 eV, 1.40 eV, and 2.1 eV, respectively. Benzene and naphthalene follow simple first order desorption kinetics while coronene and ovalene exhibit fractional order kinetics owing to the stability of two-dimensional adsorbate islands up to the desorption temperature. Preexponential frequency factors are found to be in the range 1014 1021 s-1 as obtained from both Falconer-Madix (isothermal desorption) analysis and Antoine’s fit to vapor pressure data. The resulting binding energy per carbon atom of the PAH is 52±5 meV and can be identified with the interlayer cohesive energy of graphite. The resulting cleavage energy of graphite is 61±5 meV/atom, which is considerably larger than previously reported experimental values.

Zacharia, Renju; Ulbricht, Hendrik; Hertel, Tobias

2004-04-01

216

Enhanced desorption of 2,4,6 Trinitrotoluene  

E-print Network

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

Aturaliye, Upul Anuruddha

1997-01-01

217

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

218

Quantum theory of laser-stimulated desorption  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

219

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

220

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...

221

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...

222

Temperature-programmed capillary electrophoresis for detection of DNA point mutations.  

PubMed

A method for unambiguous determination of point mutations in genomic DNA, based on electrophoresis in thin capillaries, is reported here. The method is based on the principle of temperature gradient gel electrophoresis (TGGE), a variant of denaturing gradient gel electrophoresis (DGGE), and exploits the differential melting of mutant and wild-type PCR-amplified DNA fragments during electrophoresis through a temperature gradient. Unlike TGGE, where the temperature gradient exists along the separation space, the denaturing temperature gradient in the fused-silica capillaries is time-programmed, so as to reach the melting points (Tms) of all species under analysis prior to electrophoretic transport past the detector window. The DNA fragments are injected in a capillary maintained (by combined chemical and thermal means) just below the expected Tm values. The temperature increment applied is typically minute (1 degree -1.5 degrees C) and the sweep speed is rather shallow (e.g., 0.05 degree C/min). Additionally, the denaturing thermal gradient is not controlled externally, but generated internally by Joule heat produced by voltage ramps. Point mutants are fully resolved into a spectrum of four bands, with a dynamic range extending from 45 degrees C (low melters) up to 70 degrees C for high melters. The present method can thus be universally applied to any type of point mutation. PMID:8922636

Gelfi, C; Cremonesi, L; Ferrari, M; Righetti, P G

1996-11-01

223

Thermal desorption of CH4 retained in CO2 ice  

E-print Network

CO2 ices are known to exist in different astrophysical environments. In spite of this, its physical properties (structure, density, refractive index) have not been as widely studied as those of water ice. It would be of great value to study the adsorption properties of this ice in conditions related to astrophysical environments. In this paper, we explore the possibility that CO2 traps relevant molecules in astrophysical environments at temperatures higher than expected from their characteristic sublimation point. To fulfil this aim we have carried out desorption experiments under High Vacuum conditions based on a Quartz Crystal Microbalance and additionally monitored with a Quadrupole Mass Spectrometer. From our results, the presence of CH4 in the solid phase above the sublimation temperature in some astrophysical scenarios could be explained by the presence of several retaining mechanisms related to the structure of CO2 ice.

R. Luna; C. Millan; M. Domingo; M. A. Satorre

2008-01-21

224

Method of enhancing selective isotope desorption from metals  

DOEpatents

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

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

1983-07-26

225

A basic program for calculating subsurface water temperatures using chemical geothermometers-implication to geothermal reservoir estimation  

NASA Astrophysics Data System (ADS)

GEOTHERM is a computer program written in BASIC language to estimate geothermal reservoir temperature using the well-known chemical gèothermometers. The empirical equations used in the program were obtained from the literature. Three different chemical geothermometers are included in the program: Na-K, Na-K-Ca, and silica geothermometers; this gives the user the opportunity not only to select the most reliable geothermometer in estimating subsurface temperature, but also to select the type of geothermometer according to available data. A sample input file of geothermal waters obtained from Iceland has been tested, so as to show the applicability and usefulness of the program.

El-Naqa, Ali; Zeid, Nasser Abu

1993-11-01

226

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

227

Temperature-programmed high-performance liquid chromatography coupled to isotope ratio mass spectrometry.  

PubMed

The utility of liquid chromatography coupled to the isotope ratio mass spectrometry technique (LC-IRMS) has already been established through a variety of successful applications. However, the analytical constraint related to the use of aqueous mobile phases limits the LC separation mechanism. We report here a new strategy for high-precision (13)C isotopic analyses based on temperature-programmed LC-IRMS using aqueous mobile phases. Under these conditions, the isotopic precision and accuracy were studied. On one hand, experiments were carried out with phenolic acids using isothermal LC conditions at high temperature (170 degrees C); on the other hand, several experiments were performed by ramping the temperature, as conventionally used in a gas chromatography-based method with hydrosoluble fatty acids and pulses of CO 2 reference gas. In isothermal conditions at 170 degrees C, despite the increase of the CO 2 background, p-coumaric acid and its glucuronide conjugate gave reliable isotopic ratios compared to flow injection analysis-isotopic ratio mass spectrometry (FIA-IRMS) analyses (isotopic precision and accuracy are lower than 0.3 per thousand). On the opposite, for its sulfate conjugate, the isotopic accuracy is affected by its coelution with p-coumaric acid. Not surprisingly, this study also demonstrates that at high temperature (170 degrees C), a compound eluting with long residence time (i.e., ferulic acid) is degraded, affecting thus the delta (13)C (drift of 3 per thousand) and the peak area (compared to FIA-IRMS analysis at room temperature). Quantitation is also reported in isothermal conditions for p-coumaric acid in the range of 10-400 ng/mL and with benzoic acid as an internal standard. For temperature gradient LC-IRMS, in the area of the LC gradient (set up at 20 degrees C/min), the drift of the background observed produces a nonlinearity of SD (delta (13)C) approximately 0.01 per thousand/mV. To circumvent this drift, which impacts severely the precision and accuracy, an alternative approach, i.e., eluting the compound on the plateau of temperature studied was reported here. Other experiments with temperature-programmed LC-IRMS experiments are also reported with the presence of methanol in the injected solution to mimic residual solvent originating from the sample preparation or to slightly increase the solubility of the targeted compound for high-precision measurement. PMID:18690698

Godin, Jean-Philippe; Hopfgartner, Gérard; Fay, Laurent

2008-09-15

228

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

SciTech Connect

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

Horner, M.W.

1982-03-01

229

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

PubMed

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

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

2014-09-16

230

High-temperature gas-cooled reactor safety-reliability program plan  

SciTech Connect

The purpose of this document is to present a safety plan as part of an overall program plan for the design and development of the High Temperature Gas-Cooled Reactor (HTGR). This plan is intended to establish a logical framework for identifying the technology necessary to demonstrate that the requisite degree of public risk safety can be achieved economically. This plan provides a coherent system safety approach together with goals and success criterion as part of a unifying strategy for licensing a lead reactor plant in the near term. It is intended to provide guidance to program participants involved in producing a technology base for the HTGR that is fully responsive to safety consideration in the design, evaluation, licensing, public acceptance, and economic optimization of reactor systems.

Not Available

1981-03-01

231

On factors controlling activity of submonolayer bimetallic catalysts: Nitrogen desorption  

SciTech Connect

We model N{sub 2} desorption on submonolayer bimetallic surfaces consisting of Co clusters on Pt(111) via first-principles density functional theory-based kinetic Monte Carlo simulations. We find that submonolayer structures are essential to rationalize the high activity of these bimetallics in ammonia decomposition. We show that the N{sub 2} desorption temperature on Co/Pt(111) is about 100 K higher than that on Ni/Pt(111), despite Co/Pt(111) binding N weaker at low N coverages. Co/Pt(111) has substantially different lateral interactions than single metals and Ni/Pt. The lateral interactions are rationalized with the d-band center theory. The activity of bimetallic catalysts is the result of heterogeneity of binding energies and reaction barriers among sites, and the most active site can differ on various bimetallics. Our results are in excellent agreement with experimental data and demonstrate for the first time that the zero-coverage descriptor, used until now, for catalyst activity is inadequate due not only to lacking lateral interactions but importantly to presence of multiple sites and a complex interplay of thermodynamics (binding energies, occupation) and kinetics (association barriers) on those sites.

Guo, Wei; Vlachos, Dionisios G., E-mail: vlachos@udel.edu [Center for Catalytic Science and Technology, Catalysis Center for Energy Innovation, Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716 (United States)

2014-01-07

232

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

233

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

SciTech Connect

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

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

1980-03-01

234

Synthesis, characterization and activity pattern of carbon nanofibers based copper/zirconia catalysts for carbon dioxide hydrogenation to methanol: Influence of calcination temperature  

NASA Astrophysics Data System (ADS)

A series of novel carbon nanofibers (CNFs) supported bimetallic copper/zirconia catalysts are synthesized by deposition precipitation method and calcined at different temperatures. Calcined catalysts are characterized by various techniques like X-ray diffraction, N2 adsorption-desorption, N2O chemisorption, high resolution transmission electron microscopy, temperature programmed reduction, X-ray photoelectron spectroscopy and temperature programmed desorption (CO2 & NH3). The structure-activity correlation is discussed in details. The results demonstrate 450 °C as optimum calcination temperature for methanol synthesis rate with CO2/H2 feed volume ratio of 1:3. CO2 conversion is found to be directly proportional to copper metallic surface area (SCu), while a linear relationship is observed between methanol synthesis rate and fraction of dispersed Cu.

Ud Din, Israf; Shaharun, Maizatul S.; Subbarao, Duvvuri; Naeem, A.

2015-01-01

235

Adsorption and desorption of contaminants  

SciTech Connect

The microbial remediation of sites Contaminated with organics is well documented, however, there are some significant problems that remain to be solved in the areas of contaminants sorbed to soils and non-aqueous phase liquid (NAPL) contamination. Methods of in situ bioremediation techniques employ either the stimulation of indigenous populations by nutrient addition, or the addition of prepared bacterial cultures to the subsurface environment. Problems of contaminant sorption and NAPL`s are related in that both encompass reduced contaminant bioavailability. Non-aqueous phase liquids have been identified as a priority area for research in the In situ Program due to their presence at DOE sites and the lack of adequate technology to effectively treat this contamination. Bioremediation technologies developed as a result of this project are easily transferred to industry.

Palumbo, A.V.; Strong-Gunderson, J.M. [Oak Ridge National Lab., TN (United States); DeFlaun, M.; Ensley, B. [Envirogen, Inc., Lawrenceville, NJ (United States)

1994-02-01

236

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

PubMed

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

Stolee, Jessica A; Vertes, Akos

2011-05-28

237

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. PMID:23899050

2013-01-01

238

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

SciTech Connect

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

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

1997-11-01

239

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

240

Electron stimulated desorption from thin organic films  

NASA Astrophysics Data System (ADS)

Electron stimulated desorption (ESD) is examined from a polymerized methylglutamatic acid (PMG) monolayer and from a thin soap film after exposure to a series of adsorbates with varying polarization. ESD spectra from the PMG film are dominated by product ions attributed to the water of hydration (H +, OH +, H 2O +) regardless of subsequent adsorbate exposure. ESD spectra from the soap film also exhibit H 2O related peaks, however, the adsorption of a nonpolar adsorbate (heptane) is detectable through the appearance of H +2 as a desorption product. A linear dependence of ESD product ions with incident electron current is observed. ESD total cross-sections were measured on these surfaces to be in the range of 10 -16-10 -18 cm 2.

Dylla, H. F.; Abrams, J. H.; Phillips, B. F.

1984-09-01

241

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

242

Plutonium sorption and desorption behavior on bentonite.  

PubMed

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

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

2015-03-01

243

Desorption of hexachlorobiphenyl from selected particulate matter  

E-print Network

of mechanisms, and if significant concentration gradients exist, the sorbed material will be redistributed in the environment. PCBs atmosphenc deposition transport PCBs SEDIMENT PCBs "": water home - ~ ~ - Sorption-Desorption-- PCBs sedime... be monitored by direct sampling of the reactor and the gas phase by extracting the XAD-2 columns. Ex erimental A tus and Proced Figure 4 is a schematic of the experimental apparatus. It was designed to deliver scrubbed air through a humidifier...

Rorschach, Reagan Cartwright

1989-01-01

244

Dendritic Aggregation of Oligothiophene During Desorption of 2,5-Diiodothiophene Multilayer and Topography-Induced Alignment of Oligothiophene Nanofibers  

SciTech Connect

The multilayer desorption behavior of 2,5-diidothiophene and the dendritic aggregation of photochemical reaction products during the desorption of 2,5-diiodothiophene multilayers have been studied. Like many other aromatic compounds, 2,5-diiodothiophene shows a multilayer desorption behavior different from the typical zeroth-order kinetics, a metastable desorption peak growth at {approx}220 K followed by a thick multilayer peak growth at {approx}235 K. Traditionally, these desorption behaviors have been attributed to the formation of three-dimensional clusters. This paper provides the direct evidence of this clustering process by producing nondesorbing photoreaction products in the multilayer and by imaging their clusters after the multilayer desorption. Oligothiophene species are produced via photochemical reactions of 2,5-diiodothiophene during the multilayer deposition at {approx}180 K in ultrahigh vacuum (UHV). Upon heating the multilayer to room temperature, the oligothiophene species forms into fibrous aggregates with a fractal dimension varying from 1.37 to 1.81 depending on their surface concentration. Using a topographical alteration of the substrate with a repeating pattern, these oligothiophene fibers can be aligned to a certain direction. This may allow in-situ fabrication of aligned conjugated polymer fibers directly on a target substrate.

Liu,G.; Rider, K.; Nam, W.; Fonash, S.; Kim, S.

2006-01-01

245

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

246

Lead sorption-desorption from organic residues.  

PubMed

Sorption and desorption are mechanisms involved in the reduction of metal mobility and bioavailability in organic materials. Metal release from substrates is controlled by desorption. The capacity of coffee husk and pulp residues, vermicompost and cow manure to adsorb Pb2+ was evaluated. The mechanisms involved in the sorption process were also studied. Organic materials retained high concentrations of lead (up to 36,000 mg L(-1)); however, the mechanisms of sorption varied according to the characteristics of each material: degree of decomposition, pH, cation exchange capacity and percentage of organic matter. Vermicompost and manure removed 98% of the Pb from solution. Lead precipitated in manure and vermicompost, forming lead oxide (PbO) and lead ferrite (PbFe4O7). Adsorption isotherms did not fit to the typical Freundlich and Langmuir equations. Not only specific and non-specific adsorption was observed, but also precipitation and coprecipitation. Lead desorption from vermicompost and cow manure was less than 2%. For remediation of Pb-polluted sites, the application of vermicompost and manure is recommended in places with alkaline soils because Pb precipitation can be induced, whereas coffee pulp residue is recommended for acidic soils where Pb is adsorbed. PMID:21780703

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

2011-01-01

247

History of desorption induced by electronic transitions  

NASA Astrophysics Data System (ADS)

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

Madey, Theodore E.

1994-01-01

248

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

NASA Astrophysics Data System (ADS)

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

Ekwelundu, Emmanuel Chikelue

1988-12-01

249

Adsorption and desorption of chlorpyrifos to soils and sediments.  

PubMed

Chlorpyrifos, one of the most widely used insecticides, has been detected in air, rain, marine sediments, surface waters, drinking water wells, and solid and liquid dietary samples collected from urban and rural areas. Its metabolite, TCP, has also been widely detected in urinary samples collected from people of various age groups. With a goal of elucidating the factors that control the environmental contamination, impact, persistence, and ecotoxicity of chlorpyrifos, we examine, in this review, the peer-reviewed literature relating to chlorpyrifos adsorption and desorption behavior in various solid-phase matrices. Adsorption tends to reduce chlorpyrifos mobility, but adsorption to erodible particulates, dissolved organic matter, or mobile inorganic colloids enhances its mobility. Adsorption to suspended sediments and particulates constitutes a major off-site migration route for chlorpyrifos to surface waters, wherein it poses a potential danger to aquatic organisms. Adsorption increases the persistence of chlorpyrifos in the environment by reducing its avail- ability to a wide range of dissipative and degradative forces, whereas the effect of adsorption on its ecotoxicity is dependent upon the route of exposure. Chlorpyrifos adsorbs to soils, aquatic sediments, organic matter, and clay minerals to differing degrees. Its adsorption strongly correlates with organic carbon con- tent of the soils and sediments. A comprehensive review of studies that relied on the batch equilibrium technique yields mean and median Kd values for chlorpyrifos of 271 and 116 L/kg for soils, and 385 and 403 L/kg for aquatic sediments. Chlorpyrifos adsorption coefficients spanned two orders of magnitude in soils. Normalizing the partition coefficient to organic content failed to substantially reduce variability to commonly acceptable level of variation. Mean and median values for chlorpyrifos partition coefficients normalized to organic carbon, K, were 8,163 and 7,227 L/kg for soils and 13,439 and 15,500 L/kg for sediipents. This variation may result from several factors, including various experimental artifacts, variation in quality of soil organic matter, and inconsistencies in experimental methodologies. Based on this review, there appears to be no definitive quantification of chlorpyrifos adsorption or desorption characteristics. Thus, it is difficult to predict its adsorptive behavior with certainty, without resorting to experimental methods specific to the soil or sediment of interest. This limitation should be recognized in the context of current efforts to predict the risk, fate, and transport of chlorpyrifos based upon published partition coefficients. Based on a comprehensive review of the peer-reviewed literature related to adsorption and desorption of chlorpyrifos, we propose the following key areas for future research. From this review, it becomes increasingly evident that pesticide partitioning cannot be fully accounted for by the fraction of soil or solid-matrix organic matter or carbon content. Therefore, research that probes the variation in the nature and quality of soil organic matter on pesticide adsorption is highly desirable. Pesticide persistence and bioavailability depend on insights into desorption capacity. Therefore, understanding the fate and environmental impact of hydrophobic pesticides is incomplete without new research being performed to improve insights into pesticide desorption from soils and sediments. There is also a need for greater attention and consistency in developing experimental methods aimed at estimating partition coefficients. Moreover, in such testing, choosing initial concentrations and liquid-solid ratios that are more representative of environmental conditions could improve usefulness and interpretation of data that are obtained. Future monitoring efforts should include the sampling and analysis of suspended particulates to account for suspended solid-phase CPF, a commonly underestimated fraction in surface water quality monitoring programs. Finally, management practices related to the reduction o

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

2012-01-01

250

Sorption/Desorption Interactions of Plutonium with Montmorillonite  

NASA Astrophysics Data System (ADS)

Plutonium (Pu) release to the environment through nuclear weapon development and the nuclear fuel cycle is an unfortunate legacy of the nuclear age. In part due to public health concerns over the risk of Pu contamination of drinking water, predicting the behavior of Pu in both surface and sub-surface water is a topic of continued interest. Typically it was assumed that Pu mobility in groundwater would be severely restricted, as laboratory adsorption studies commonly show that naturally occurring minerals can effectively remove plutonium from solution. However, evidence for the transport of Pu over significant distances at field sites highlights a relative lack of understanding of the fundamental processes controlling plutonium behavior in natural systems. At several field locations, enhanced mobility is due to Pu association with colloidal particles that serve to increase the transport of sorbed contaminants (Kersting et al., 1999; Santschi et al., 2002, Novikov et al., 2006). The ability for mineral colloids to transport Pu is in part controlled by its oxidation state and the rate of plutonium adsorption to, and desorption from, the mineral surface. Previously we have investigated the adsorption affinity of Pu for montmorillonite colloids, finding affinities to be similar over a wide range of Pu concentrations. In the present study we examine the stability of adsorbed Pu on the mineral surface. Pu(IV) at an initial concentration of 10-10 M was pre-equilibrated with montmorillonite in a background electrolyte at pH values of 4, 6 and 8. Following equilibration, aliquots of the suspensions were placed in a flow cell and Pu-free background electrolyte at the relevant pH was passed through the system. Flow rates were varied in order to investigate the kinetics of desorption and hence gain a mechanistic understanding of the desorption process. The flow cell experiments demonstrate that desorption of Pu from the montmorillonite surface cannot be modeled as a simple first order process. Furthermore, a pH dependence was observed, with less desorbed at pH 4 compared to pH 8. We suggest the pH dependence is likely controlled by reoxidation of Pu(IV) to Pu(V) and aqueous speciation. We will present models used to describe desorption behavior and discuss the implications for Pu transport. References: Kersting, A.B.; Efurd, D.W.; Finnegan, D.L.; Rokop, D.J.; Smith, D.K.; Thompson J.L. (1999) Migration of plutonium in groundwater at the Nevada Test Site, Nature, 397, 56-59. Novikov A.P.; Kalmykov, S.N.; Utsunomiya, S.; Ewing, R.C.; Horreard, F.; Merkulov, A.; Clark, S.B.; Tkachev, V.V.; Myasoedov, B.F. (2006) Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia, Science, 314, 638-641. Santschi, P.H.; Roberts, K.; Guo, L. (2002) The organic nature of colloidal actinides transported in surface water environments. Environ. Sci. Technol., 36, 3711-3719. This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. LLNL-ABS-570161

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

2012-12-01

251

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

USGS Publications Warehouse

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

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

1988-01-01

252

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

253

Molecular desorption of stainless steel vacuum chambers irradiated with 42 MeV/u lead ions  

E-print Network

In preparation for the heavy ion program of the Large Hadron Collider at CERN, accumulation and cooling tests with lead ion beams have been performed in the Low Energy Antiproton Ring. These tests have revealed that due to the unexpected large outgassing of the vacuum system, the dynamic pressure of the ring could not be maintained low enough to reach the required beam intensities. To determine the actions necessary to lower the dynamic pressure rise, an experimental program has been initiated for measuring the molecular desorption yields of stainless steel vacuum chambers by the impact of 4.2 MeV/u lead ions with the charge states +27 and +53. The test chambers were exposed either at grazing or at perpendicular incidence. Different surface treatments (glow discharges, nonevaporable getter coating) are reported in terms of the molecular desorption yields for H/sub 2 /, CH/sub 4/, CO, Ar, and CO/sub 2/. (16 refs).

Mahner, E; Laurent, Jean Michel; Madsen, N

2003-01-01

254

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

255

Desorption Studies of DDGS under Varying CDS and Temperature Levels  

Technology Transfer Automated Retrieval System (TEKTRAN)

Distillers dried grains with solubles (DDGS) often contains approximately 30-35% (db) protein and 10-12% (db) fat, and has been shown to be an excellent livestock feed. DDGS is produced from the fuel ethanol industry, which is located in the midwest US; there is a growing need to transport DDGS over...

256

Plasma desorption mass spectrometry of organics at low temperatures  

E-print Network

of structural features, i.e., the length of the alkane chains, and the size, saturation and nature of the substitution groups on aliphatic or aromatic rings. Specifically, the following compounds were studied: n-decane, n-octane, n-hexane, n-pentane, cyclooctane...

Shirey, Eldon Lynn

1993-01-01

257

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

NASA Technical Reports Server (NTRS)

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

Sollit, Luke S.; Beegle, Luther W.

2008-01-01

258

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

PubMed

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

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

2006-11-01

259

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

PubMed

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

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

2013-09-15

260

The effect of selective desorption mechanisms during interstellar ice formation  

E-print Network

Major components of ices on interstellar grains in molecular clouds - water and carbon oxides - occur at various optical depths. This implies that selective desorption mechanisms are at work. An astrochemical model of a contracting low-mass molecular cloud core is presented. Ice was treated as consisting of the surface and three subsurface layers (sublayers). Photodesorption, reactive desorption, and indirect reactive desorption were investigated. The latter manifests itself through desorption from H+H reaction on grains. Desorption of shallow subsurface species was included. Modeling results suggest the existence of a "photon-dominated ice" during the early phases of core contraction. Subsurface ice is chemically processed by interstellar photons, which produces complex organic molecules. Desorption from the subsurface layer results in high COM gas-phase abundances at Av = 2.4...10mag. This may contribute towards an explanation for COM observations in dark cores. It was found that photodesorption mostly gove...

Kalvans, Juris

2015-01-01

261

High temperature experiments on a 4 tons UF6 container TENERIFE program  

SciTech Connect

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

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

1991-12-31

262

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

PubMed Central

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

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

2011-01-01

263

Kinetics of phenanthrene desorption from activated carbons to water.  

PubMed

We determined the kinetics of phenanthrene desorption from three activated carbons to water using Tenax beads as an infinite sink for organic compounds in water. Desorption kinetic data very well fitted a biphasic kinetic model based on the presence of two different adsorption sites, viz. low-energy sites and high-energy sites. Rate constants for desorption to water from these two types of sites in the three activated carbons did not reveal a relation with activated carbon grain size. These rate constants were comparable to those for desorption of various organic compounds from hard carbon in various sediments. PMID:18321560

Morelis, Simone; van Noort, Paul C M

2008-05-01

264

Activation energy of water desorption from guanosine.  

NASA Astrophysics Data System (ADS)

The interactions of the nucleic acids with their water of hydration are of fundamental importance and still imperfectly understood. As an initial effort, we have studied a component of RNA: the nucleoside guanosine (rG), composed of the ribose sugar and the guanine base. The interactions of the water of primary hydration with rG have been studied via thermogravimetric measurements and differential thermal analysis. These data yield the activation energy for the desorption of the water of primary hydration from rG.

Smith, Megan; Lee, Scott

2008-10-01

265

Thermal desorption mass spectrometer for mass metrology  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

266

Thermal desorption mass spectrometer for mass metrology.  

PubMed

This article presents a device for the study of physisorbed elements on polished surfaces (diameter ?56 mm) of the kind used in mass metrology. The technique is based on mass spectrometry of molecules desorbed after heating under vacuum of the analyzed surface. We describe a first application of the device to study current and future mass standards in order to understand how their surface reactivity depends on storage conditions, cleaning processes, and polishing methods. Surface contamination analysis by thermal desorption mass spectrometry to examine the effect of cleaning on pure iridium is given as an example. PMID:24784663

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

2014-04-01

267

Adsorption and Desorption of Cr(III) on a Spherical Cellulose Adsorbent  

Microsoft Academic Search

An investigation was conducted on adsorption and desorption of Cr(III) with a new spherical cellulose adsorbent containing the carboxymethyl group by using static and dynamic methods. The static experiments showed that the adsorption of Cr(III) on adsorbent was pH, adsorption temperature, initial concentration and adsorption time dependent. The adsorption process followed both Langmuir and Freundlich adsorption isotherms. The dynamic process

Ruoqi Chen; Yifan Liu; Minghua Liu; Yang Zhao

2011-01-01

268

Temperature  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

269

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

SciTech Connect

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

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

1983-06-01

270

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

SciTech Connect

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

Palmer, C.R.

1996-04-01

271

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

NASA Technical Reports Server (NTRS)

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

Walker, K. P.

1981-01-01

272

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

273

Theoretical study of heat and mass transfer in a zeolite bed during water desorption: validity of local thermal equilibrium assumption  

Microsoft Academic Search

We have studied heat and mass transfer in a zeolite bed during water desorption. For this purpose, a mathematical model based on scale changing has been established. We have tested the local thermal equilibrium assumption in a two-dimensional flow.The problem is numerically resolved using a finite volume method. The numerical simulation gives the time and space evolution of temperature and

A. Mhimid

1998-01-01

274

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

NASA Astrophysics Data System (ADS)

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

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

1983-03-01

275

Particle-Scale Investigation of PAH Desorption Kinetics and  

E-print Network

- density coal- and wood-derived fraction with 62% of total PAHs and a heavier-density sand, silt, and clay model were used to describe the thermal desorption of PAHs for four molecular weight classes. PAH.e., in the range of 37-41 kJ/ mol for molecular weight 202. Among the desorption models tested, a spherical

276

Regeneration of Honeycomb Zeolite by Nonthermal Plasma Desorption of Toluene  

Microsoft Academic Search

In order to develop an economical volatile organic compound (VOC) removal process, a concentration technique using nonthermal plasma combined with an adsorption process is investigated. Toluene-one of the most commonly used VOCs-is used, and the optimization of plasma desorption is investigated. The effects of toluene concentration and adsorbent regeneration are investigated by varying the plasma desorption methods: closing method, in

Tomoyuki Kuroki; Takeshi Fujioka; Ryouhei Kawabata; Masaaki Okubo; Toshiaki Yamamoto

2009-01-01

277

Thermal desorption of atmospheric organic pollutants enriched on charcoal  

Microsoft Academic Search

A technique of thermal vacuum desorption of charcoal, used in passive dosimeters to enrich organic pollutants of toxicological importance, is described. It combines the advantages of the classic procedure of using highly active charcoal followed by solvent desorption and the environmental one-step procedure of analyzing the whole thermally desorbed sample. For pollutants such as trichloroethylene, tetrachloroethylene, ether, benzene and ethanol,

L. Senf; F. Stapf; B. Diisedau; H. Frank

1988-01-01

278

[(252)Cf-plasma desorption mass spectra of bacterial oligosaccharides].  

PubMed

252Cf plasma desorption mass spectrometry on a "reflect" desorption instrument (MSBX) was used to study oligosaccharides from bacterial O-specific antigenic chains. The data obtained for galacturonic acid, neutral and aminouronic oligosaccharides are discussed. This method is suggested for determining the composition of oligosaccharides from the O-specific polysaccharides and for elucidating their structures after modifications. PMID:7527636

El'kin, Iu N; Komandrova, N A; Tomshich, S V; Bondarenko, P V; Zubarev, R A; Knish, A N

1994-07-01

279

ATRAZINE DESORPTION KINETICS FROM A FRESH-WATER SEDIMENT  

EPA Science Inventory

Research has shown that the sorption and desorption of neutral organic compounds to soils and sediments occurs in two stages, with an initial rapid sorption/desorption phase (usually less than an hour) followed by a slower phase that can last for several months to years for very ...

280

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

Microsoft Academic Search

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

Yogesh K. Vohra

2005-01-01

281

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. PMID:18387311

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

2008-01-01

282

Quantum dynamical simulations of the femtosecond-laser-induced ultrafast desorption of H2 and D2 from Ru(0001).  

PubMed

We investigate the recombinative desorption of hydrogen and deuterium from a Ru(0001) surface initiated by femtosecond laser pulses. We adopt a quantum mechanical two-state model including three molecular degrees of freedom to describe the dynamics within the desorption induced by electronic transition (DIET) limit. The energy distributions as well as the state-resolved and ensemble properties of the desorbed molecules are analyzed in detail by using the time-energy method. Our results shed light on the experimentally observed 1) large isotopic effects regarding desorption yields and translational energies and 2) the nonequal energy partitioning into internal and translational modes. In particular, it is shown that a single temperature is sufficient to characterize the energy distributions for all degrees of freedom. Further, we confirm that quantization effects play an important role in the determination of the energy partitioning. PMID:23426934

Füchsel, Gernot; Tremblay, Jean Christophe; Klamroth, Tillmann; Saalfrank, Peter

2013-05-10

283

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

284

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

PubMed

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

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

2014-02-01

285

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

PubMed

Nonresonant multiphoton ionization with time-of-flight mass spectrometry has been used to monitor the desorption of aluminum chloride (Al(x)Cl(y)) etch products from the Al(111) surface at 100 and 500 K during low-coverage (<5% monolayer) monoenergetic Cl(2) (0.11-0.65 eV) dosing. The desorption products in this low-coverage range show predominantly hyperthermal exit velocities under all dosing conditions. For example, with 0.27 eV incident Cl(2), the etch product was found to have a most-probable velocity of 517+/-22 m/s at an Al(111) surface temperature of 100 K. This corresponds to 22 times the expected thermal desorption translational energy for AlCl(3). Cl(2) sticking probability measurements and Al(x)Cl(y) etch rate measurements show etching even at Cl(2) coverages of less than 5% monolayer at surface temperatures between 100 and 500 K. These experimental results are consistent with a combination of fast-time-scale surface diffusion and agglomeration of the adsorbed chlorine to form aluminum chlorides and the presence of activated AlCl(3) chemisorption states having potential energies above the vacuum level. Density functional theory calculations yield results that are consistent with both our experimental findings and mechanistic descriptions. PMID:15527367

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

2004-11-01

286

Dynamic Traffic Management using Temperature Parameter Control in Q value-based Dynamic Programming with Boltzmann Distribution  

NASA Astrophysics Data System (ADS)

In order to improve the efficiency of traffic systems in the global perspective, a traffic control strategy for the dynamic traffic management in the road network has been proposed in this paper. The main idea of the proposed traffic control strategy is based on Q value-based Dynamic Programming with Boltzmann Distribution, and the temperature parameters in Boltzmann Distribution are adjusted by the proposed temperature parameter control strategies, which are Network Method and Intersection Method, depending on the time-varying traffic situations. In the simulation, it is supposed that the route guidance is given to each vehicle and all the vehicles in the traffic system follow the guidance. The simulation results show that temperature parameter control in Q value-based Dynamic Programming with Boltzmann Distribution could improve the performance of the traffic system.

Yu, Shanqing; Mabu, Shingo; Mainali, Manoj Kanta; Hirasawa, Kotaro

287

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

NASA Technical Reports Server (NTRS)

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

Cassenti, B. N.

1983-01-01

288

Hot-carrier transport processes in stimulated desorption of alkali halides  

NASA Astrophysics Data System (ADS)

Electron- and photon-stimulated desorption of epitaxial thin films and bulk single crystals of alkali halides has been investigated. It has been found that the widely accepted model based on self-trapped exiton decay and thermally activated defect diffusion cannot account for a number of experimental observations. In particular, it cannot explain the stability of the very thin alkali-halide films against the electron beam, and it fails to interpret correctly the yield dependence of the halogen atoms emitted with nonthermal energies on the film thickness and sample temperature. It is shown that for satisfactory interpretation of those data one has to take into account early stages of crystal excitation, i.e., hot carrier formation and transport processes occurring prior to self-trapped exciton phase. Consequently, a comprehensive description of the observed desorption features is presented.

Kolodziej, J. J.; Szymonski, M.

1998-11-01

289

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

290

Continuous electron stimulated desorption using a ZrO2/Ag permeation membrane  

NASA Technical Reports Server (NTRS)

During the development of an atomic oxygen beam generator for laboratory simulation of the atmospheric conditions in low earth orbit, a new technique for performing electron stimulated desorption (ESD) in a continuous manner has been developed. In this technique, oxygen permeates through an Ag membrane at elevated temperature thereby providing a continuous supply of oxygen atoms to the 1000-A ZrO2 coating at the vacuum interface. ESD then results in a large peak of neutral O2 molecules which ultimately decay into steady-state desorption. The ESD signal is linear with respect to primary beam flux (0.035 O2 molecules per electron at a primary beam energy of 1 keV) but nonlinear with respect to primary beam energy.

Outlaw, R. A.; Hoflund, Gar B.; Davidson, M. R.

1989-01-01

291

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

292

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

293

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

SciTech Connect

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

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

2014-06-21

294

Computer program for afterheat temperature distribution for mobile nuclear power plant  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

295

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

PubMed

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

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

2013-07-01

296

[Comparison on desorptive behavior of copper in phaeozem and burozem].  

PubMed

Desorptive behavior of Cu2+ from phaeozem and burozem was studied and compared using the batch method. The results indicated that Cu2+ desorbed from phaeozem tested had a longer lag period than that from burozem. When adsorbed Cu2+ for phaeozem was lower than 729.00 mg x kg(-1) (Cu2+ concentration was lower than 40 mg x L(-1)), and on burozem was lower than 393.29 mg x kg(-1) (Cu2+ concentration was lower than 20 mg x L(-1)), adsorbed Cu2+ was hardly desorbed. Meanwhile, the desorption ratio of Cu2+ from the two soils were both low, especially for phaeozem. In the range of Cu2+ concentration used in the experiments, the desorption rate maximums of Cu2+ for phaeozem and burozem were respectively 6.60% and 13.56%. Freundlich equation could best describe desorption isotherm processes of Cu2+ from the two soils. Adsorbed Cu2+ on soils was desorbed so fast from phaeozem and burozem that the desorption equilibrium could be reached only after 40 min desorption. The best model to describe Cu2+ desorption kinetics was two-constant equations, followed by the Elovich equation. PMID:15330438

Yu, Ying; Zhou, Qi-xing

2004-01-01

297

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

298

Effect of temperature on lubrication with biobased oils  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

299

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

300

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

PubMed Central

A new and inexpensive lignocellulose/montmorillonite (LNC/MMT) nanocomposite was prepared by a chemical intercalation of LNC into MMT and was subsequently investigated as an adsorbent in batch systems for the adsorption-desorption of Ni(II) ions in an aqueous solution. The optimum conditions for the Ni(II) ion adsorption capacity of the LNC/MMT nanocomposite were studied in detail by varying parameters such as the initial Ni(II) concentration, the solution pH value, the adsorption temperature and time. The results indicated that the maximum adsorption capacity of Ni(II) reached 94.86 mg/g at an initial Ni(II) concentration of 0.0032 mol/L, a solution pH of 6.8, an adsorption temperature of 70°C, and adsorption time of 40 min. The represented adsorption kinetics model exhibited good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir isotherm equation best fit the experimental data. The structure of the LNC/MMT nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas the adsorption mechanism was discussed in combination with the results obtained from scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy analyses (FTIR). The desorption capacity of the LNC/MMT nanocomposite depended on parameters such as HNO3 concentration, desorption temperature, and desorption time. The satisfactory desorption capacity of 81.34 mg/g was obtained at a HNO3 concentration, desorption temperature, and desorption time of 0.2 mol/L, 60 ºC, and 30 min, respectively. The regeneration studies showed that the adsorption capacity of the LNC/MMT nanocomposite was consistent for five cycles without any appreciable loss in the batch process and confirmed that the LNC/MMT nanocomposite was reusable. The overall study revealed that the LNC/MMT nanocomposite functioned as an effective adsorbent in the detoxification of Ni(II)-contaminated wastewater. PMID:25647398

Zhang, Xiaotao; Wang, Ximing

2015-01-01

301

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

302

Electron stimulated desorption of atomic oxygen from silver  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

303

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

PubMed

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

Zhang, Xiaolong; Hu, Hongjiu; Guo, Manxia

2015-02-01

304

Time-of-flight investigation of infrared laser-induced multilayer desorption of benzene  

NASA Astrophysics Data System (ADS)

Infrared (IR) laser-induced resonant desorption/ablation of benzene layers condensed on liquid-nitrogen-cooled substrates has been investigated using the time-of-flight (TOF) technique. Adsorbates of up to 5 ?m thickness were irradiated with a line-tuned TEA CO2 laser. Time-resolved detection of desorbed particles was performed with a quadrupole mass spectrometer (QMS). Measured TOF spectra can usually be well fitted with a stream-modified Maxwell-Boltzmann distribution. Systematic deviations from these fits were observed depending on film thickness, laser fluence, and angle of detection. Spectroscopic data of the adsorbate-substrate system needed for model calculations were measured in situ. The absorption coefficients were found to be fluence dependent. Measurements of the desorption yield and kinetic energy of the desorbed particles were performed with the P932 and P934-CO2 laser lines as a function of film thickness and laser fluence. The solid-liquid phase transition could clearly be observed in these experiments. Average kinetic energies of up to 0.8 eV were measured in the TOF spectra, where the adsorbate temperature could be estimated to be less than 600 K. IR multilayer laser-induced desorption (LID) exhibits features very similar to those reported for UV multilayer LID. A mechanism based on the sudden rise of the adsorbate vapor pressure due to fast energy deposition by the laser pulse is discussed.

Braun, R.; Hess, P.

1993-11-01

305

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

PubMed

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

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

2002-03-01

306

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

307

Low-temperature phases obtained by linear programming: An application to a lattice system of model chiral molecules  

Microsoft Academic Search

A convenient, Peierls-type approach to obtain low-temperature phases is to use the method of an m-potential. In this paper we show that, for more complex systems where it may be rather difficult to rewrite the Hamiltonian as an m-potential and whose configurations are subject to linear constraints, the verification of the Peierls condition can be reformulated as a linear programming

Igor Medved; Anton Trník; Dale A. Huckaby

2011-01-01

308

Study of the temperature-programmed reaction synthesis of early transition metal carbide and nitride catalyst materials from oxide precursors  

Microsoft Academic Search

The synthesis of high surface area carbide and nitride materials from binary and ternary oxides of vanadium, niobium, tantalum, molybdenum, and tungsten, suitable for use as catalysts for a wide range of reactions, has been investigated via the temperature-programmed reaction (TPRe) method, in various gas mixtures. TPRe of oxides in CHâ\\/Hâ, CâHâ\\/Hâ, or NHâ yield materials with surface areas >

John B. Claridge; Andrew P. E. York; Attila J. Brungs; Malcolm L. H. Green

2000-01-01

309

Development of Designer Diamond Technology for High Pressure High Temperature Experiments in Support of Stockpile Stewardship Program  

Microsoft Academic Search

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

Vohra; Yogesh

2009-01-01

310

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

2013-02-15

311

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

312

Comparative sorption, desorption and leaching potential of aminocyclopyrachlor and picloram  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

313

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

314

Molecular beam-thermal hydrogen desorption from palladium  

SciTech Connect

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

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

2010-04-15

315

Salt Tolerance of Desorption Electrospray Ionization (DESI)  

SciTech Connect

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

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

2007-01-01

316

The influences of various factors on the adsorption-desorption behaviors of hydrophobic organic compounds in sediments of Lake Charles, LA  

SciTech Connect

Both the adsorption and the desorption processes play important roles in the transport and fate of organic contaminants in water-sediments and groundwater systems. The adsorption-desorption processes are shown to be influenced by a number of factors, including sediments organic carbon content, contaminant aqueous solubility, aqueous-phase concentration as well as some natural environmental factors such as pH, pE, ionic strength and temperature. External mechanical forces, such as sediment perturbation, and repeated dredging will also have finite effect on the microscopic interparticle forces that control bonds between large and small grain particles. The objective of this research is to study the influences of various environmental effects on the equilibrium or non-equilibrium desorption behavior of nonpolar organic pollutants in historically contaminated natural sediments of Lake Charles, LA. Differences of desorption behavior between freshly and historically contaminated sediments will be compared in order to evaluated the desorption mechanism. The influences of particle size, mineral composition, organic matter concentration, and aqueous phase matrix composition on desorption behaviour will also be evaluated.

Wei Chen; Kan, A.T.; Tomson, M.B. [Rice Univ., Houston, TX (United States)

1996-10-01

317

Photostimulated desorption in laser-assisted etching of silicon  

NASA Astrophysics Data System (ADS)

Photodesorption of SiF3 groups, which are the principal adsorbates on a silicon surface during etching by XeF2, is found to be responsible for the etch-rate enhancement observed under illumination by low-power, cw band-gap radiation. It is proposed that desorption is stimulated by photogenerated-charge-carrier-mediated chemical reaction, and not the simple charge trapping and recombination mechanism usually invoked for desorption from semiconductor surfaces.

Houle, F. A.

1988-10-01

318

Photostimulated desorption in laser-assisted etching of silicon  

Microsoft Academic Search

Photodesorption of SiF3 groups, which are the principal adsorbates on a silicon surface during etching by XeF2, is found to be responsible for the etch-rate enhancement observed under illumination by low-power, cw band-gap radiation. It is proposed that desorption is stimulated by photogenerated-charge-carrier-mediated chemical reaction, and not the simple charge trapping and recombination mechanism usually invoked for desorption from semiconductor

F. A. Houle

1988-01-01

319

Explosive vaporization of crystal water on temperature-programmed heating of a thin film of hydrated calcium nitrate  

NASA Astrophysics Data System (ADS)

The temperature-programmed vaporization of crystal water in vacuum was studied for a thin film of Ca(NO3)*nH2O prepared on a nichrome ribbon heater. The mass-spectrometric signal intensity of vaporized water measured as a function of the film temperature reveals a spectrum consisting of two sharp peaks, in remarkable contrast to the broad spectra observed for other kinds of hydrated inorganic salts. The low-temperature peak exhibits normal kinetic features which seem to be consistent with direct emission of water molecules from the crystalline lattice of the hydrated salt. However, the high-temperature peak appears in an explosive manner, and its intensity relative to the low-temperature peak increases with increasing film thickness or with increasing heating rate. These features of the high-temperature peak suggest the occurrence of a kinetic phase transition of the hydrated salt from a crystalline state to a non-crystalline state, rather than step-wise dehydration of the crystalline salt.

Asada, Hiromu; Udaka, Masayuki; Kawano, Hiroyuki

1994-11-01

320

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

321

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

322

Water-cooled end-point boundary temperature control of hot strip via dynamic programming  

Microsoft Academic Search

In this paper, an end-point boundary temperature control approach for runout table cooling used in hot strip mills is presented. The system relies on a linearized model for describing heat radiated to the environment and heat transferred to cooling water. At first, a conventional feedforward control design to control the temperature at the end-point boundary, the only measurable controlled parameter,

Nicholas S. Samaras; Marwan A. Simaan

1998-01-01

323

Water cooled end-point boundary temperature control of hot strip via dynamic programming  

Microsoft Academic Search

This paper presents a system for end-point boundary temperature control approach, for run out table (ROT) cooling, used in hot strip mills. The system relies on a linearized model for describing heat radiated to the environment and heat transferred to cooling water. A conventional feedforward control design to control the temperature at the end boundary point, the only measurable controlled

Nicholas S. Samaras; M. A. Simaan

1997-01-01

324

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

SciTech Connect

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

Song, Chunshan; Schobert, H.H.

1993-02-01

325

Small molecules as substrates for adsorption/desorption in (252)CF plasma desorption mass spectrometry.  

PubMed

Department of Chemistry, Texas A & M University, College Station, Texas, USA We present a new approach to substrate selection for californium-252 plasma desorption mass spectrometry ((252)Cf_PDMS) in which small volatile molecules that are water insoluble are used as matrices in place of the polymeric substrates used in previous studies. The desirable features of analyte adsorption are combined with the concept of using a volatile matrix to reduce the level of internal excitation of a desorbed analyte and to assist in ionization during the desorption process. Derivatives of anthracene were found to meet these requirements and to perform satisfactorily as substrates in (252)Cf-PDMS. Spectra were obtained for bovine insulin (m I z 5734) adsorbed onto 9-anthroic acid and 2-aminoanthracene and compared with spectra using a nitrocellulose substrate. Sharper peaks and lower backgrounds are observed when the 9-anthroic acid matrix is used, indicating reduced levels of internal excitation and initial kinetic energy for the desorbed molecular ion of insulin. A comparison of the performance of 9-anthroic acid and 2-aminoanthracene shows the influence of substrate functional groups on desorbed protein yields. Finally, the versatility of the small-molecule matrix concept is discussed with respect to selection of a range of functionality, solubility, and hydrophilicity. PMID:24242086

Wolf, B; Macfarlane, R D

1991-01-01

326

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...

327

Adsorption-desorption Hysteresis of Kr and Xe on the Surface of an Ag Single Crystal  

NASA Astrophysics Data System (ADS)

The isotherms and the isobars of krypton and xenon physisorbed on a silver single crystal surface were investigated by ellipsometric observation of the amount of adsorption. It was found that they showed a hysteresis in an adsorption-desorption loop for both the first and the second layer condensations. Careful examination of the effect of instability of an equilibrium pressure and a substrate temperature during the measurement revealed that they were not responsible for hysteresis. The observed hysteresis is very likely to be intrinsic one though its origin and mechanism are unknown.

Hamada, Nozomu; Moto, Shuichi; Nakazawa, Jun; Miura, Takashi; Arakawa, Ichiro

328

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

NASA Astrophysics Data System (ADS)

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

Rogers, Kevin; Milnes, John; Gormally, John

1993-02-01

329

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

2013-11-01

330

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

NASA Astrophysics Data System (ADS)

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

Ueba, H.; Ootsuka, Y.

2013-05-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

332

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

333

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

334

Low-temperature phases obtained by linear programming: An application to a lattice system of model chiral molecules  

NASA Astrophysics Data System (ADS)

A convenient, Peierls-type approach to obtain low-temperature phases is to use the method of an m-potential. In this paper we show that, for more complex systems where it may be rather difficult to rewrite the Hamiltonian as an m-potential and whose configurations are subject to linear constraints, the verification of the Peierls condition can be reformulated as a linear programming problem. Before introducing this novel strategy for a general lattice system, we compare it with the m-potential method for a specific model molecular system consisting of an equimolar mixture of a chiral molecule and its non-superimposable mirror image that occupy all the sites of a honeycomb lattice. In one range of interactions, we prove that a racemic low-temperature phase occurs (containing equal numbers of each enantiomer). However, in a neighboring range of interactions, we show that a homochiral low-temperature phase (containing a single enantiomer) exists, and thus chiral segregation occurs in the system. Our linear programming technique yields these results in wider ranges of interactions than the m-potential method.

Medved', Igor; Trník, Anton; Huckaby, Dale A.

2011-09-01

335

In situ ?+SR measurements on the hydrogen desorption reaction of magnesium hydride  

NASA Astrophysics Data System (ADS)

In order to clarify the reason why the hydrogen desorption temperature (Td) of MgH2 is lowered by milling, we have studied the change in a local nuclear magnetic field with temperature by means of ?+SR. We have found a very clear oscillation in the ZF-spectrum at 2 K for the "milled" and "milled with Nb2O5" samples, while such oscillation is weaker for the "as prepared" MgH2. It was also found that the oscillation signal is stable up to 250 K and is assigned mainly due to the formation of a H-?-H system. At temperatures above ambient T, we also found that the ZF-?+SR spectrum exhibits a static Kubo-Toyabe behavior due to the nuclear magnetic field of 1H. Furthermore, it was clarified that rapid H diffusion starts well below Td only in the milled samples, leading to the conclusion that the consequent enhanced diffusion rate in MgH2 is essential to accelerate the desorption reaction and to decrease Td.

Umegaki, I.; Nozaki, H.; Harada, M.; Higuchi, Y.; Noritake, T.; Matsumoto, M.; Towata, S.-i.; Ansaldo, E. J.; Brewer, J. H.; Koda, A.; Miyake, Y.; Sugiyama, J.

2014-12-01

336

Absorption and desorption of gaseous toluene by an absorbent microcapsules column.  

PubMed

Heavy solvents absorption appears to be very attractive in recovering of volatile organic compounds (VOCs) from industrial tail gas. Their high viscosities make good dispersion required but difficult to reduce mass transfer resistance. Microencapsulation techniques provide a candidate solution. In this paper, vapor pressures for toluene+poly(dimethylsiloxane) (PDMS) mixtures were measured at temperature ranging from 273.2K to 343.2K. Polyacrylonitrile (PAN) hollow microspheres, prepared by orifice dispersion plus solvent extraction method, was used to immobilize PDMS. The capacity was adjusted from 2.3g to 9.3g PDMS/g PAN by addition of cyclohexane in PDMS during solvent impregnation. The breakthrough curves of column packed with PDMS/PAN microcapsules were determined, indicating shapes close to ideality, high absorption efficiencies and considerable absorption capacities before breakthrough. The influence of operational temperature, concentration of feed and gas feed flow rate on the absorption process were investigated as well. A mathematical model, suitable for dilute gas absorption process, was used to simulate the breakthrough curves. This model has proved to be useful to fit curves and analyze the absorption kinetics of PDMS/PAN microcapsules column. After absorption, the column can be regenerated completely by gas stripping. Enrichment of toluene was founded by increasing desorption temperature. Through absorption and desorption by turns, the stability of PDMS/PAN microcapsules column was verified. PMID:19733968

Xiang, Ziying; Lu, Yangcheng; Gong, Xingchu; Luo, Guangsheng

2010-01-15

337

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

338

Results of an interlaboratory fatigue test program conducted on alloy 800H at room and elevated temperatures  

NASA Technical Reports Server (NTRS)

The experimental approach adopted for low cycle fatigue tests of alloy 800H involved the use of electrohydraulic test systems, hour glass geometry specimens, diametral extensometers, and axial strain computers. Attempts to identify possible problem areas were complicated by the lack of reliable data for the heat of Alloy 800H under investigation. The method adopted was to generate definitive test data in an Interlaboratory Fatigue Test Program. The laboratories participating in the program were Argonne National Laboratory, Battelle Columbus, Mar-Test, and NASA Lewis. Fatigue tests were conducted on both solid and turbular specimens at temperatures of 20, 593, and 760 C and strain ranges of 2.0, 1.0, and 0.5 percent. The subject test method can, under certain circumstances, produce fatigue data which are serious in error. This approach subsequently was abandoned at General Atomic Company in favor of parallel gage length specimens and axial extensiometers.

Ellis, J. R.

1985-01-01

339

13th TOPICAL CONFERENCE ON HIGH TEMPERATURE PLASMA DIAGNOSTICS SCIENTIFIC PROGRAM  

SciTech Connect

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

C. BARNES

2000-07-01

340

Influence of surface coverage on the chemical desorption process  

NASA Astrophysics Data System (ADS)

In cold astrophysical environments, some molecules are observed in the gas phase whereas they should have been depleted, frozen on dust grains. In order to solve this problem, astrochemists have proposed that a fraction of molecules synthesized on the surface of dust grains could desorb just after their formation. Recently the chemical desorption process has been demonstrated experimentally, but the key parameters at play have not yet been fully understood. In this article, we propose a new procedure to analyze the ratio of di-oxygen and ozone synthesized after O atoms adsorption on oxidized graphite. We demonstrate that the chemical desorption efficiency of the two reaction paths (O+O and O+O2) is different by one order of magnitude. We show the importance of the surface coverage: for the O+O reaction, the chemical desorption efficiency is close to 80% at zero coverage and tends to zero at one monolayer coverage. The coverage dependence of O+O chemical desorption is proved by varying the amount of pre-adsorbed N2 on the substrate from 0 to 1.5 ML. Finally, we discuss the relevance of the different physical parameters that could play a role in the chemical desorption process: binding energy, enthalpy of formation, and energy transfer from the new molecule to the surface or to other adsorbates.

Minissale, M.; Dulieu, F.

2014-07-01

341

Ultrasonic desorption of petroleum hydrocarbons from crude oil contaminated soils.  

PubMed

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

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

2013-01-01

342

Influence of surface coverage on the chemical desorption process  

SciTech Connect

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

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

2014-07-07

343

Peptide desorption kinetics from single molecule force spectroscopy studies.  

PubMed

We use a combined experimental/theoretical approach to determine the intrinsic monomeric desorption rate k0 of polytyrosine and polylysine homopeptides from flat surfaces. To this end, single polypeptide molecules are covalently attached to an AFM cantilever tip and desorbed from hydrophobic self-assembled monolayers in two complementary experimental protocols. In the constant-pulling-velocity protocol, the cantilever is moved at finite velocity away from the surface and the distance at which the constant plateau force regime ends and the polymer detaches is recorded. In the waiting-time protocol, the cantilever is held at a fixed distance above the surface and the time until the polymer detaches is recorded. The desorption plateau force is varied between 10 and 90 pN, by systematically changing the aqueous solvent quality via the addition of ethanol or salt. A simultaneous fit of the experimental data from both protocols with simple two-state kinetic polymer theory allows to unambiguously disentangle and determine the model parameters corresponding to polymer contour length L, Kuhn length a, adsorption free energy ?, and intrinsic monomeric desorption rate k0. Crucial to our analysis is that a statistically significant number of single-polymer desorption experiments are done with one and the same single polymer molecule for different solvent qualities. The surprisingly low value of about k0 ? 10(5) Hz points to significant cooperativity in the desorption process of single polymers. PMID:24328353

Krysiak, Stefanie; Liese, Susanne; Netz, Roland R; Hugel, Thorsten

2014-01-15

344

Kinetics of arsenate adsorption-desorption in soils.  

PubMed

Adsorption-desorption of arsenic is the primary factor that impacts the bioavailability and mobility of arsenic in soils. To examine the characteristics of arsenate [As(V)] adsorption-desorption, kinetic batch experiments were carried out on three soils having different properties, followed by arsenic release using successive dilutions. Adsorption of As(V) was highly nonlinear, with a Freundlich reaction order N much less than 1 for Olivier loam, Sharkey clay, and Windsor sand. Adsorption of arsenate by all soils was strongly kinetic, where the rate of As(V) retention was rapid initially and was followed by gradual or somewhat slow retention behavior with increasing reaction time. Freundlich distribution coefficients and Langmuir adsorption maxima exhibited continued increase with reaction time for all soils. Desorption of As(V) was hysteretic in nature and is an indication of lack of equilibrium retention and/or irreversible or slowly reversible processes. A sequential extraction procedure provided evidence that a significant amount of As(V) was irreversibly adsorbed on all soils. A multireaction model (MRM) with nonlinear equilibrium and kinetic sorption successfully described the adsorption kinetics of As(V) for Olivier loam and Windsor sand. The model was also capable of predicting As(V) desorption kinetics for both soils. However, for Sharkey clay, which exhibited strongest affinity for arsenic, an additional irreversible reaction phase was required to predict As(V) desorption or release with time. PMID:16173569

Zhang, Hua; Selim, H M

2005-08-15

345

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

346

Scanning electron microscopic imaging of surface effects in desorption and nano-desorption electrospray ionization.  

PubMed

Scanning electron microscopy was used to investigate rivulets that are formed on the analyzed surface during desorption electrospray ionization (DESI) experiment. Ferromagnetic nanoparticles added to the spray solvent in a form of colloid solution functioned as an additional surface probe. The existence of the rivulets was confirmed on glass and newly demonstrated on two different types of porous polytetrafluoroethylene (PTFE). The results show that in standard DESI set-up the rivulets are arranged into very regular shapes. Same rivulets were obtained in DESI experiments without high voltage on the sprayer. However, no such rivulets or any other regular patterns were found on a surface in nano-DESI (nanospray DESI without the carrier nebulizing gas) experiments. This indicates that symmetrical rivulets are created by the hydrodynamical rather than electrostatic forces. It was also demonstrated that blocking the rivulets by a simple physical barrier did not influence known surface charging effects. PMID:21394841

Kaftan, Filip; Kofro?ová, Olga; Benada, Old?ich; Lemr, Karel; Havlí?ek, Vladimír; Cva?ka, Josef; Volný, Michael

2011-03-01

347

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

348

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

349

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

350

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

351

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

SciTech Connect

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

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

1990-10-01

352

Desorption mass spectrometry for nonvolatile compounds using an ultrasonic cutter.  

PubMed

In this work, desorption of nonvolatile analytes induced by friction was studied. The nonvolatile compounds deposited on the perfluoroalkoxy substrate were gently touched by an ultrasonic cutter oscillating with a frequency of 40 kHz. The desorbed molecules were ionized by a dielectric barrier discharge (DBD) ion source. Efficient desorption of samples such as drugs, pharmaceuticals, amino acids, and explosives was observed. The limits of detection for these compounds were about 1 ng. Many compounds were detected in their protonated forms without undergoing significant fragmentation. When the DBD was off, no ions for the neutral samples could be detected, meaning that only desorption along with little ionization took place by the present technique. PMID:24833356

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

2014-07-01

353

The study of 'microsurfaces' using thermal desorption spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

354

A Computer Program for the Computation of Running Gear Temperatures Using Green's Function  

NASA Technical Reports Server (NTRS)

A new technique has been developed to study two dimensional heat transfer problems in gears. This technique consists of transforming the heat equation into a line integral equation with the use of Green's theorem. The equation is then expressed in terms of eigenfunctions that satisfy the Helmholtz equation, and their corresponding eigenvalues for an arbitrarily shaped region of interest. The eigenfunction are obtalned by solving an intergral equation. Once the eigenfunctions are found, the temperature is expanded in terms of the eigenfunctions with unknown time dependent coefficients that can be solved by using Runge Kutta methods. The time integration is extremely efficient. Therefore, any changes in the time dependent coefficients or source terms in the boundary conditions do not impose a great computational burden on the user. The method is demonstrated by applying it to a sample gear tooth. Temperature histories at representative surface locatons are given.

Koshigoe, S.; Murdock, J. W.; Akin, L. S.; Townsend, D. P.

1996-01-01

355

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

SciTech Connect

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

Icerman, Larry

1983-08-01

356

Development program of a 60 kA current lead using high temperature superconductors  

Microsoft Academic Search

The use of high temperature superconductors in current leads to reduce the refrigerator power consumption has been investigated in the last few years by many groups. Potential candidates are Y-123 and Bi-2212 bulk material as well as Bi-2223 tapes sheathed with an Ag\\/Au alloy. In the frame of the European Fusion Technology Programme, FZK Karlsruhe and CRPP Villigen have started

R. Heller; G. Friesinger; W. Goldacker; H. Kathol; B. Ullmann; A. M. Fuchs; B. Jakob; G. Pasztor; G. Vecsey; R. Wesche

1997-01-01

357

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

Microsoft Academic Search

This report summarizes the results of low-temperature geothermal energy resource assessment efforts in New Mexico during the period from June 15, 1981 through September 30, 1983, under the sponsorship of the US Department of Energy (Contract DE-AS07-78ID01717). The report is divided into four chapters which correspond to the tasks delineated in the contract. Chapter 5 is a brief summary of

Icerman

1983-01-01

358

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

359

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

PubMed

In this paper we present a model relating experimental factors (column lengths, diameters and thickness, modulation times, pressures and temperature programs) with retention times. Unfortunately, an analytical solution to calculate the retention in temperature programmed GC × GC is impossible, making thus necessary to perform a numerical integration. In this paper we present a computational physical model of GC × GC, capable of predicting with a high accuracy retention times in both dimensions. Once fitted (e.g., calibrated), the model is used to make predictions, which are always subject to error. In this way, the prediction can result rather in a probability distribution of (predicted) retention times than in a fixed (most likely) value. One of the most common problems that can occur when fitting unknown parameters using experimental data is overfitting. In order to detect overfitting situations and assess the error, the K-fold cross-validation technique was applied. Another technique of error assessment proposed in this article is the use of error propagation using Jacobians. This method is based on estimation of the accuracy of the model by the partial derivatives of the retention time prediction with respect to the fitted parameters (in this case entropy and enthalpy for each component) in a set of given conditions. By treating the predictions of the model in terms of intervals rather than as precise values, it is possible to considerably increase the robustness of any optimization algorithm. PMID:25441353

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

2014-11-14

360

Distinguishibility of oxygen desorption from the surface region with mobility dominant effects in nanocrystalline ceria films  

NASA Astrophysics Data System (ADS)

We present an investigation of oxygen (O18) uptake measurements in 1?m thick nanocrystalline ceria films grown on single crystal Al2O3(0001) by nuclear reaction analysis (NRA). Oxygen uptake measurements were carried out in the temperature range of 200-600°C at a background O18 pressure of 4.0×10-6Torr. Average grain size in the as-grown films, synthesized by sol-gel process was ˜3nm confirmed by high-resolution transmission electron microscopy and x-ray diffraction measurements. From the diffusion depth profiles, changes in intensity and slopes in surface and interface regions indicate complex oxygen mobility effects. Oxygen desorption is clearly distinguishable in the film surface region as a result of shift in the oxygen concentration maxima. It is argued that high defect density in nanocrystalline ceria which is associated with nanograin surface combined with intermediate temperature reducing environment triggers multiple processes such as molecular and ionic diffusion, adsorption, desorption, and isotope exchange interactions. The promising nature of NRA is realized as an effective tool to acquire the depth-dependent information from complex reactions existing in nanocrystalline environment.

Saraf, Laxmikant; Shutthanandan, V.; Zhang, Y.; Thevuthasan, S.; Wang, C. M.; El-Azab, Anter; Baer, Donald R.

2004-11-01

361

Computer program MCAP-TOSS calculates steady-state fluid dynamics of coolant in parallel channels and temperature distribution in surrounding heat-generating solid  

NASA Technical Reports Server (NTRS)

Computer program calculates the steady state fluid distribution, temperature rise, and pressure drop of a coolant, the material temperature distribution of a heat generating solid, and the heat flux distributions at the fluid-solid interfaces. It performs the necessary iterations automatically within the computer, in one machine run.

Lee, A. Y.

1967-01-01

362

Phosphorus adsorption and desorption behavior on sediments of different origins  

Microsoft Academic Search

Purpose  The aim of this study was to assess phosphorus-retention (Pret) capacities via P adsorption (Pads) and desorption (Pdes) by sediments collected from six different sources associated with various origins, physical, and chemical characteristics.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  Sediment samples were collected in the State of Florida, the USA, from estuary, marine, wetland, canal, river, and lake, respectively.\\u000a Phosphorus adsorption and desorption for

Qingren Wang; Yuncong Li

2010-01-01

363

The dynamics of adsorption and desorption at surfaces  

SciTech Connect

Molecular dynamics simulations, in concert with experiments, have greatly enhanced our understanding of the elementary dynamical processes of adsorption and desorption. The observations of anomalously large desorption prefactors, of deviations from integer-order kinetics, of non-thermal energies of desorbing molecules, of deviations from {open_quotes}normal energy scaling{close_quotes}, and of the contributions of internal energy to adsorption all are consequences of the multidimensional nature of gas-surface interactions, and are revealed clearly through the multidimensional picture afforded by molecular dynamics simulations. This talk will highlight some of the central issues and controversies in this field over the last decade or so, and their subsequent resolution.

Tully, J.C. [AT & T Bell Labs., Murray Hill, NJ (United States)

1995-12-01

364

High-temperature gas-cooled reactor (HTGR): long term program plan  

SciTech Connect

The FY 1980 effort was to investigate four technology options identified by program participants as potentially viable candidates for near-term demonstration: the Gas Turbine system (HTGR-GT), reflecting its perceived compatibility with the dry-cooling market, two systems addressing the process heat market, the Reforming (HTGR-R) and Steam Cycle (HTGR-SC) systems, and a more developmental reactor system, The Nuclear Heat Source Demonstration Reactor (NHSDR), which was to serve as a basis for both the HTGR-GT and HTGR-R systems as well as the further potential for developing advanced applications such as steam-coal gasification and water splitting.

Not Available

1980-10-09

365

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

366

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

PubMed Central

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

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

2015-01-01

367

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

368

Aging Effects on the Kinetics of Cesium Desorption from Vermiculite And Contaminated Soil  

E-print Network

Aging Effects on the Kinetics of Cesium Desorption from Vermiculite And Contaminated Soil A. M), it is important to determine how aging affects 137 Cs desorption. This study uses a batch technique to measure 0

Sparks, Donald L.

369

Desorption or `Surface Melting' of Lubricant Films  

Microsoft Academic Search

A RECENT communication1 has described the effect of temperature on the lubricating properties of mineral oils. The apparatus used for the experiments was that devised by Bowden and Leben for analysing the frictional force between sliding surfaces. In this apparatus the bottom surface is driven steadily forward, but the upper surface is mounted on a bifilar suspension so that it

D. Tabor

1941-01-01

370

The adsorption and reaction of methanol on Pd(100). II. Thermal desorption and decomposition  

NASA Astrophysics Data System (ADS)

The reaction of methanol with a clean Pd(100) surface has been studied between 77 and 300 K using a variety of techniques. High-resolution electron energy loss spectroscopy, thermal desorption spectroscopy, UV photoemission work function measurements, and low energy electron diffraction reveal a complex reaction pattern. At 77 K, photoemission, vibrational loss spectra, thermal desorption data, as well as the ?? behavior indicate the initial formation of a methoxide species which has a maximum population around 1×1014/cm2. 80% of this methoxide species desorbs as methanol between 180 and 210 K via second-order kinetics with Edes˜11.5-12 kcal/mol. Above ˜200 K, we find that 20% of all the initially adsorbed species have not desorbed but have converted to two other more stable species. These species have CH3O stochiometries as determined from thermal desorption product ratios, but cannot be further identified. The first of these is more stable and predominantly forms (95% of total remaining species). It decomposes at ˜300 K to produce CO+H on the surface and has UPS level intensities significantly different than those observed from the methoxide. The other species occur in very small concentrations and only for higher coverages of the adsorbate. It appears in small amounts, ˜5% of these remaining species as inferred from its decomposition to gaseous CO+H2 at ˜530 K. A simple bond site model is proposed to account for the ability of the low temperature methoxide species to hydrogenate in the presence of chemisorbed hydrogen. These results are compared to those on Ni(100). The observation of this hydrogenatable form of methoxide on Pd as well as its large branching ratio into methanol provides a possible explanation for the selectivity of Pd in catalytically forming methanol from synthesis gas.

Christmann, K.; Demuth, J. E.

1982-06-01

371

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

PubMed

The photodesorption of water molecules from amorphous solid water (ASW) by 157-nm irradiation has been examined using resonance-enhanced multiphoton ionization. The rotational temperature has been determined, by comparison with simulations, to be 425 ± 75 K. The time-of-flight spectrum of H2O (v = 0) has been fit with a Maxwell-Boltzmann distribution with a translational temperature of 700 ± 200 K (0.12 ± 0.03 eV). H(+) and OH(+) fragment ions have been detected with non-resonant multiphoton ionization, indicating vibrationally excited parent water molecules with translational energies of 0.24 ± 0.08 eV. The cross section for water removal from ASW by 7.9-eV photons near 100 K is (6.9 ± 1.8) × 10(-20) cm(2) for >10 L H2O exposure. Electronic structure computations have also probed the excited states of water and the mechanisms of desorption. Calculated electron attachment and detachment densities show that exciton delocalization leads to a dipole reversal state in the first singlet excited state of a model system of hexagonal water ice. Ab Initio Molecular Dynamics simulations show possible desorption of a photo-excited water molecule from this cluster, though the non-hydrogen bonded OH bond is stretched significantly before desorption. Potential energy curves of this OH stretch in the electronic excited state show a barrier to dissociation, lending credence to the dipole reversal mechanism. PMID:24182059

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

2013-10-28

372

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

NASA Astrophysics Data System (ADS)

The photodesorption of water molecules from amorphous solid water (ASW) by 157-nm irradiation has been examined using resonance-enhanced multiphoton ionization. The rotational temperature has been determined, by comparison with simulations, to be 425 ± 75 K. The time-of-flight spectrum of H2O (v = 0) has been fit with a Maxwell-Boltzmann distribution with a translational temperature of 700 ± 200 K (0.12 ± 0.03 eV). H+ and OH+ fragment ions have been detected with non-resonant multiphoton ionization, indicating vibrationally excited parent water molecules with translational energies of 0.24 ± 0.08 eV. The cross section for water removal from ASW by 7.9-eV photons near 100 K is (6.9 ± 1.8) × 10-20 cm2 for >10 L H2O exposure. Electronic structure computations have also probed the excited states of water and the mechanisms of desorption. Calculated electron attachment and detachment densities show that exciton delocalization leads to a dipole reversal state in the first singlet excited state of a model system of hexagonal water ice. Ab Initio Molecular Dynamics simulations show possible desorption of a photo-excited water molecule from this cluster, though the non-hydrogen bonded OH bond is stretched significantly before desorption. Potential energy curves of this OH stretch in the electronic excited state show a barrier to dissociation, lending credence to the dipole reversal mechanism.

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

2013-10-01

373

Role of titanium in hydrogen desorption in crystalline sodium alanate  

Microsoft Academic Search

The role of Ti in improving the thermodynamics of hydrogen desorption in crystalline sodium alanate (NaAlH4) has been investigated by using the density functional theory. The total energy calculations reveal that Ti prefers to occupy the Na site over that of the Al site when the atomic energies are used as the reference. However, the use of the cohesive energies

C. Moysés Araújo; Rajeev Ahuja; J. M. Osorio Guillén; Puru Jena

2005-01-01

374

Water vapor desorption and adsorbent regeneration using nonthermal plasma  

Microsoft Academic Search

The dehumidification from a dehumidifier or an air conditioner was employed to achieve a comfortable and desirable indoor environment. Water vapor adsorbed on adsorbent needs to be regenerated when the water vapor exceeds the adsorption capacity. The conventional process for adsorbent regeneration or moisture desorption uses the heat by means of the heater. In the present study, the water vapor

Toshiaki YAMAMOTO; Goichi TANIOKA; Masaaki OKUBO; Tomoyuki KUROKI

2004-01-01

375

SITE TECHNOLOGY CAPSULE: CLEAN BERKSHIRES, INC. - THERMAL DESORPTION SYSTEM  

EPA Science Inventory

The thermal desorption process devised by Clean Berkshires, Inc., works by vaporizing the organic contaminants from the soil with heat, isolating the contaminant! in a gas stream, and then destroying them in a high efficiency afterburner. he processed solids are either replaced f...

376

SITE TECHNOLOGY CAPSULE: CLEAN BERKSHIRES, INC. THERMAL DESORPTION SYSTEM  

EPA Science Inventory

The thermal desorption process devised by Clean Berkshires, Inc., works by vaporizing the organic contaminants from the soil with heat, isolating the contaminant! in a gas stream, and then destroying them in a high efficiency afterburner. The processed solids are either replaced ...

377

Desorption of Arsenic from Drinking Water Distribution System Solids  

EPA Science Inventory

Given the limited knowledge regarding the soluble release of arsenic from DWDS solids, the objectives of this research were to: 1) investigate the effect of pH on the dissolution/desorption of arsenic from DWDS solids, and 2) examine the effect of orthophosphate on the soluble re...

378

DEMONSTRATION BULLETIN: THERMAL DESORPTION SYSTEM - CLEAN BERKSHIRES, INC.  

EPA Science Inventory

A thermal desorption system (TDS) has been developed by Clean Berkshires, Inc. (CBI), Lanesboro, Massachusetts for ex-situ treatment of soils and other media contaminated with organic pollutants. The TDS uses heat as both a physical separation mechanism and as a means to destro...

379

Desorption electrospray ionization mass spectrometry of intact bacteria  

Technology Transfer Automated Retrieval System (TEKTRAN)

Desorption electrospray ionization (DESI) mass spectrometry (MS) was used to differentiate 7 bacterial species based on their measured DESI-mass spectral profile. Both Gram positive and Gram negative bacteria were tested and included Escherichia coli, Staphyloccocus aureus, Enterococcus sp., Bordete...

380

Permeability changes in coal resulting from gas desorption  

SciTech Connect

Research continued on the study of coal permeability and gas desorption. This quarter, most of the effort involved identifying problems with the microbalance and then getting it repaired. Measurement of the amount of gas adsorbed with the microbalance involved corrections for the buoyancy change with pressure and several experiments with helium were made to determine this correction.

Levine, J.R.; Johnson, P.M.

1992-01-01

381

Physisorption, Diffusion, Adsorption/Desorption of Molecular Hydrogen on Graphene  

NASA Astrophysics Data System (ADS)

The interaction of a H2 molecule with a graphene surface is studied using AIREBO bond -order potential. Adsorption potential, desorption potential, and diffusion barriers of H2 on graphene are obtained and compared with the corresponding results from the first-principles. The massively parallel molecular dynamics codes (lammps) and nudged elastic band (NEB) method are employed to do these calculations.

Karimi, Majid; Petucci, Justin; Vidali, Gianfranco

2013-03-01

382

LASER DESORPTION IONIZATION OF SIZE RESOLVED LIQUID MICRODROPLETS. (R823980)  

EPA Science Inventory

Mass spectra of single micrometer-size glycerol droplets containing organic and inorganic analytes were obtained by on-line laser desorption ionization. Aerosol droplets entered the mass spectrometer through an inlet where they were detected by light scattering of a continuous la...

383

Sorption-desorption of indaziflam in selected agricultural soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sorption and desorption of indaziflam in 6 soils from Brazil and 3 soils from the USA, with different physical chemical properties, were investigated using the batch equilibration method. Sorption kinetics demonstrated that soil-solution equilibrium was attained in a 24-h period. The Freundlich equa...

384

Desorption electrospray ionization-mass spectrometry of proteins  

Technology Transfer Automated Retrieval System (TEKTRAN)

Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the detection of proteins ranging in molecular mass from 12 to 66 kDa. Proteins were uniformly deposited on a solid surface without pretreatment and analyzed with a DESI source coupled to a quadrupole ion trap mass spec...

385

Matrix-assisted Laser Desorption of *Peptidesin Transmission Geometry  

E-print Network

~~~_ Matrix-assisted Laser Desorption of *Peptidesin Transmission Geometry Akos Vertes* Laszlo, Francc The possibility of performing matrix-assisted laser &sorption experiments in trknsmission geometry in the high mass region. The question addressed in this Communication con- cerns the geometry of laser

Vertes, Akos

386

Nitrate sorption and desorption in biochars from fast pyrolysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

Increasing the nitrate (NO3-) sorption capacity of Midwestern US soils has the potential to reduce nitrate leaching to ground water and reduce the extent of the hypoxia zone in the Gulf of Mexico. The objective of this study was to determine the sorption and desorption capacity of non-activated and ...

387

Adsorption kinetics and desorption of Cu(II) and Zn(II) from aqueous solution onto humic acid.  

PubMed

The adsorption kinetics of Cu(II) and Zn(II) from aqueous solution onto humic acid (HA) were investigated under different conditions. The results showed that HA was particularly effective for adsorbing heavy metals and that the effective pH range was above 6. The adsorption force was not single and dependent on solution pH. The experimental data were found to comply with the pseudo-second-order kinetic model with adsorption capacity, q(e cal) more close to the measured results. Increment of initial adsorbate concentration (1-4 mg/L) and temperature (283-303 K) are both favorable to adsorption process. Based on the desorption experiments, it is further indicated that the main adsorption force was complexation effect between organic ligands of HA surface and metal ions and the percentage of desorption is 50% for Cu and 30% for Zn, respectively. PMID:20149528

Li, Ying; Yue, Qinyan; Gao, Baoyu

2010-06-15

388

A laser-induced fluorescence study of OH desorption from Pt(111) during oxidation of hydrogen in O2 and decomposition of water  

NASA Astrophysics Data System (ADS)

The desorption of OH radicals from Pt(111) at high temperature, ?1000 K, during the water formation (H2+1/2 O2?H2O) and water decomposition reactions, respectively, was investigated using the laser-induced fluorescence technique. The results are compared with corresponding data from our laboratory for polycrystalline Pt. The OH desorption rate in H2+O2 at 1-100 mTorr total pressure has its maximum at 8%-9% relative H2 concentration for surface temperatures between 1100 and 1400 K. With H2 replaced by D2, the OD desorption rate maximizes at somewhat higher relative hydrogen content. The apparent activation energy for OH desorption increases from about 1.4 eV at low relative hydrogen concentration to about 2.0 eV at hydrogen contents of 25% or more. For the water decomposition reaction, the apparent activation energy for OH desorption was found to be 1.7±0.2 eV at 0.5 Torr and 1.9±0.2 eV at 1 Torr. These differences in apparent activation energies are primarily due to kinetic effects. The results are analyzed within a kinetic model previously developed by Hellsing et al. [J. Catal. 132, 210 (1991)], and are also compared with previous data for polycrystalline Pt. The kinetic model calculations give good overall agreement with the measured OH desorption rates as functions of temperature, H2/O2 mixture and H2O pressure, respectively. A nonuniqueness problem, with respect to the choice of kinetic parameters, is encountered in the simulation of the measured data; quite different sets of two of the kinetic constants, namely the activation energy for water formation (via OH+H?H2O) and the activation energy for OH desorption can reproduce the data as long as their difference is constant. This nonuniqueness problem, which is a consequence of the steady-state nature of the measurements, is analyzed and discussed in some detail, as are some apparent contradictions in the absolute values of reported kinetic constants in the literature. From this analysis two important conclusions are drawn. (i) The apparent contradictions in the literature about absolute values of activation energies for the water formation reaction and for OH-desorption may be less severe than believed or nonexistent. (ii) Coverage dependent activation energies must be considered and experimental exploration of such coverage dependencies are needed to create a firmer base for the kinetic modeling of the H2/O2 reaction on Pt.

Fridell, Erik; Elg, Alf-Peter; Rosén, Arne; Kasemo, Bengt

1995-04-01

389

Detection Via Laser Desorption and Mass Spectrometry of Multiplex Electrophore-labeled  

E-print Network

Detection Via Laser Desorption and Mass Spectrometry of Multiplex Electrophore-labeled Albumin was detected as a dried spot deposited on a polyimide membrane by laser desorption/capillary collection (of sequence of steps: (1) thermal release of the electrophores by CO2 laser desorption, (2) collection

Church, George M.

390

Adsorption and desorption of phenol on anion-exchange resin and activated carbon  

Microsoft Academic Search

Adsorption and desorption of phenol on activated carbon and strong base anion-exchange resin were investigated in a fixed-bed column. Phenol was effectively adsorbed on both adsorbents. Experimental breakthrough curves were compared with values calculated on the assumption of surface diffusion controlling. Two methods of regeneration of adsorbents were carried out, that is, caustic desorption and acid desorption. Regeneration by sodium

Motonobu. Goto; Norio. Hayashi; Shigeo. Goto

1986-01-01

391

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

392

Investigations into ultraviolet matrix-assisted laser desorption  

SciTech Connect

Matrix-assisted laser desorption (MALD) is a technique for converting large biomolecules into gas phase ions. Some characteristics of the commonly used uv matrices are determined. Solubilities in methanol range from 0.1 to 0.5 M. Solid phase absorption spectra are found to be similar to solution, but slightly red-shifted. Acoustic and quartz crystal microbalance signals are investigated as possible means of uv-MALD quantitation. Evidence for the existence of desorption thresholds is presented. Threshold values are determined to be in the range of 2 to 3 MW/cm{sup 2}. A transient imaging technique based on laser-excited fluorescence for monitoring MALD plumes is described. Sensitivity is well within the levels required for studying matrix-assisted laser desorption, where analyte concentrations are significantly lower than those in conventional laser desorption. Results showing the effect of film morphology, particularly film thickness, on plume dynamics are presented. In particular, MALD plumes from thicker films tend to exhibit higher axial velocities. Fluorescent labeling of protein and of DNA is used to allow imaging of their uv-MALD generated plumes. Integrated concentrations are available with respect to time, making it possible to assess the rate of fragmentation. The spatial and temporal distributions are important for the design of secondary ionization schemes to enhance ion yields and for the optimization of ion collection in time-of-flight MS instruments to maximize resolution. Such information could also provide insight into whether ionization is closely associated with the desorption step or whether it is a result of subsequent collisions with the matrix gas (e.g., proton transfer). Although the present study involves plumes in a normal atmosphere, adaptation to measurements in vacuum (e.g., inside a mass spectrometer) should be straightforward.

Heise, T.W.

1993-07-01

393

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

SciTech Connect

The original objective was to develop an energy-efficient hydrocarbon dehydrogenation process based on catalytic membrane reactors. Golden Technologies determined that the goals of this contract would be best served by novating the contract to an end user or other interested party which is better informed on the economic justification aspects of petrochemical refining processes to carry out the remaining work. In light of the Chevron results, the program objective was broadened to include development of inorganic membranes for applications in the chemical industry. The proposed membrane technologies shall offer the potential to improve chemical production processes via conversion increase and energy savings. The objective of this subcontract is to seek a party that would serve as a prime contractor to carry out the remaining tasks on the agreement and bring the agreement to a successful conclusion. Four tasks were defined to select the prime contractor. They were (1) prepare a request for proposal, (2) solicit companies as potential prime contractors as well as team members, (3) discuss modifications requested by the potential prime contractors, and (4) obtain, review and rank the proposals. The accomplishments on the tasks is described in detail in the following sections.

Kleiner, R.N. [Kleiner (Richard N.), Englewood, CO (United States)] [Kleiner (Richard N.), Englewood, CO (United States)

1998-08-28

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

Adsorption / Desorption Behavior of Water Vapor in an Adsorbent Desiccant Rotor  

NASA Astrophysics Data System (ADS)

Adsorption / desorption behavior of water vapor onto desiccant rotor has been investigated to improve the desiccant cooling system by means of computer simulation. In this paper, we paid attention to the relationship between the equilibrium amount of water adsorbed onto the desiccant material and the relative humidity, that is adsorption isotherm as a principal characteristic feature of adsorbent. Considering actual adsorbents, five types of adsorption isotherms were assumed to clarify the influence of adsorption isotherm on the dehumidifying performance. After the investigation on the influences of some operating conditions on the dehumidifying performance at each selected adsorption isotherm, it was found that higher dehumidifying performance and reduction of length of desiccant rotor could be achieved by selecting appropriate adsorption isotherm. It was also predicted that S-shaped adsorption isotherm which is raised sharply at relative humidity around 15 % could produce the lowest air humidity at regeneration air temperature 80 °C. Moreover influence of the intraparticle diffusion coefficient which significantly influence on the adsorption / desorption rate was discussed choosing two adsorption isotherm from the above five isotherms. It seems that effective range of the intraparticle diffusion coefficient for the significant improvement of the dehumidifying performance was strongly influenced by the shape of adsorption isotherm.

Tsujiguchi, Takuya; Kodama, Akio

396

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

397

Low-temperature selective catalytic reduction of NO with NH? over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route.  

PubMed

Nanoflaky MnO(x) on carbon nanotubes (nf-MnO(x)@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH?. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N? adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H? temperature-programmed reduction (H?-TPR) and NH? temperature-programmed desorption (NH?-TPD). The SEM, TEM, XRD results and N? adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnO(x) and the obtained catalyst exhibited a large surface area as well. Compared with the MnO(x)/CNT and MnO(x)/TiO? catalysts prepared by an impregnation method, the nf-MnO(x)@CNTs presented better NH?-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn(4+) and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnO(x)@CNTs. The H?-TPR and NH?-TPD results demonstrated that the nf-MnO(x)@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnO(x)@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N? with NH?. In addition, the nf-MnO(x)@CNT catalyst also presented favourable stability and H?O resistance. PMID:23928911

Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

2013-10-01

398

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

NASA Technical Reports Server (NTRS)

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

Wood, G. M., Jr.

1974-01-01

399

Programs  

Cancer.gov

The Biorepositories and Biospecimen Research Branch is responsible for the direction and management of several programs. These include the Biospecimen Research Network, the NCI Best Practices for Biospecimen Resources, the Cancer Human Biobank (caHUB) and the Biospecimen Pre-Analytical Variables Program. Each program has specific goals and targeted outcomes which lend themselves to supporting the mission and vision of the Branch as well as the other NCI and NIH initiatives. More information about each program can be found on their respective pages.

400

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

PubMed Central

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

Hu, Jing; Aitken, Michael D.

2012-01-01

401

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

PubMed

Low solubility of certain hydrophobic soil contaminants limits remediation process. Surface-active compounds can improve the solubility and removal of hydrophobic compounds from contaminated soils and, consequently, their biodegradation. Hence, this paper aims to study desorption efficiency of oil from soil of SPB1 lipopeptide biosurfactant. The effect of different physicochemical parameters on desorption potency was assessed. Taguchi experimental design method was applied in order to enhance the desorption capacity and establish the best washing parameters. Mobilization potency was compared to those of chemical surfactants under the newly defined conditions. Better desorption capacity was obtained using 0.1% biosurfacatnt solution and the mobilization potency shows great tolerance to acidic and alkaline pH values and salinity. Results show an optimum value of oil removal from diesel-contaminated soil of about 87%. The optimum washing conditions for surfactant solution volume, biosurfactant concentration, agitation speed, temperature, and time were found to be 12 ml/g of soil, 0.1% biosurfactant, 200 rpm, 30 °C, and 24 h, respectively. The obtained results were compared to those of SDS and Tween 80 at the optimal conditions described above, and the study reveals an effectiveness of SPB1 biosurfactant comparable to the reported chemical emulsifiers. (1) The obtained findings suggest (a) the competence of Bacillus subtilis biosurfactant in promoting diesel desorption from soil towards chemical surfactants and (b) the applicability of this method in decontaminating crude oil-contaminated soil and, therefore, improving bioavailability of hydrophobic compounds. (2) The obtained findings also suggest the adequacy of Taguchi design in promoting process efficiency. Our findings suggest that preoptimized desorption process using microbial-derived emulsifier can contribute significantly to enhancement of hydrophobic pollutants' bioavailability. This study can be complemented with the investigation of potential role in improving the biodegradation of the diesel adsorbed to the soil. PMID:23818070

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

2014-01-01

402

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. PMID:24068964

Gilmore, Sarah A.; Naseem, Shamoon; Konopka, James B.; Sil, Anita

2013-01-01

403

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

PubMed

Rapid detection of trace level anabolic steroids in urine is highly desirable to monitor the consumption of performance enhancing anabolic steroids by athletes. The present article describes a novel strategy for identifying the trace anabolic steroids in urine using Leidenfrost phenomenon assisted thermal desorption (LPTD) coupled to dielectric barrier discharge (DBD) ionization mass spectrometry. Using this method the steroid molecules are enriched within a liquid droplet during the thermal desorption process and desorbed all-together at the last moment of droplet evaporation in a short time domain. The desorbed molecules were ionized using a dielectric barrier discharge ion-source in front of the mass spectrometer inlet at open atmosphere. This process facilitates the sensitivity enhancement with several orders of magnitude compared to the thermal desorption at a lower temperature. The limits of detection (LODs) of various steroid molecules were found to be in the range of 0.05-0.1 ng mL(-1) for standard solutions and around two orders of magnitude higher for synthetic urine samples. The detection limits of urinary anabolic steroids could be lowered by using a simple and rapid dichloromethane extraction technique. The analytical figures of merit of this technique were evaluated at open atmosphere using suitable internal standards. The technique is simple and rapid for high sensitivity and high throughput screening of anabolic steroids in urine. PMID:25066712

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

2014-08-11

404

Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran formation and emission in the thermal desorption waste treatment process  

SciTech Connect

It is extremely unlikely that significant amounts of polychlorinated dibenzo-p-dioxins (PCDDs) or polychlorinated dibenzofurans (PCDFs) will be emitted in the off-gas stream from the thermal desorption process, or the treated waste, particularly if the baseline design and anticipated operating conditions of the enhanced bench-scale (EBS) system are used. However, because of the acute toxicity of these compounds and because most of the data on their formation have been extrapolated from studies more related to incineration and fire conditions than thermal desorption, specific laboratory tests and specific EBS runs should be performed to monitor the rate of emission of PCDDs and PCDFs under thermal desorption conditions. In general, the following four conditions need to exist for significant amounts of PCDD or PCDF to be formed: (1) the presence of fly ash; (2) the presence of an oxidizing source; (3) a suitable temperature, and (4) the presence of a suitable precursor. Although the EBS system provides some of these conditions, it is unlikely that enough fly ash will be produced in the system to allow a significant amount of PCDD or PCDF formation. Additionally, particulate matter controls will be used to remove airborne particulates from the gas phase. If PCDD/Fs are presented in a waste stream being evaluated in the EBS, they will likely volatilize in the kiln and subsequently condense in the venturi scrubber system.

Leckey, J.H.

1995-03-01

405

Characterization of Surface Vanadia Forms on V\\/Ti–Oxide Catalyst via Temperature-Programmed Reduction in Hydrogen and Spectroscopic Methods  

Microsoft Academic Search

Surface vanadia species formed on vanadia\\/titania catalysts consisting of 0.2–2.6 monolayers (ML) of VOx have been characterized by FT–Raman spectroscopy under controlled atmosphere, temperature-programmed reduction in hydrogen (TPR), and solubility in diluted HNO3. Three types of species were observed with the maximum peak temperatures as follows: isolated monomeric species (?770–780 K), polymeric species (810 K), and bulk amorphous V2O5 (852

Dmitri A. Bulushev; Lioubov Kiwi-Minsker; Fabio Rainone; Albert Renken

2002-01-01

406

Improved Imaging Resolution in Desorption Electrospray Ionization Mass Spectrometry  

SciTech Connect

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

Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

2008-01-01

407

Spatially resolved thermal desorption/ionization coupled with mass spectrometry  

DOEpatents

A system and method for sub-micron analysis of a chemical composition of a specimen are described. The method includes providing a specimen for evaluation and a thermal desorption probe, thermally desorbing an analyte from a target site of said specimen using the thermally active tip to form a gaseous analyte, ionizing the gaseous analyte to form an ionized analyte, and analyzing a chemical composition of the ionized analyte. The thermally desorbing step can include heating said thermally active tip to above 200.degree. C., and positioning the target site and the thermally active tip such that the heating step forms the gaseous analyte. The thermal desorption probe can include a thermally active tip extending from a cantilever body and an apex of the thermally active tip can have a radius of 250 nm or less.

Jesse, Stephen; Van Berkel, Gary J; Ovchinnikova, Olga S

2013-02-26

408

Laser desorption in an ion trap mass spectrometer  

SciTech Connect

Laser desorption in a ion-trap mass spectrometer shows significant promise for both qualitative and trace analysis. Several aspects of this methodology are discussed in this work. We previously demonstrated the generation of both negative and positive ions by laser desorption directly within a quadrupole ion trap. In the present work, we explore various combinations of d.c., r.f., and time-varying fields in order to optimize laser generated signals. In addition, we report on the application of this method to analyze samples containing compounds such as amines, metal complexes, carbon clusters, and polynuclear aromatic hydrocarbons. In some cases the ability to rapidly switch between positive and negative ion modes provides sufficient specificity to distinguish different compounds of a mixture with a single stage of mass spectrometry. In other experiments, we combined intensity variation studies with tandem mass spectrometry experiments and positive and negative ion detection to further enhance specificity.

Eiden, G.C.; Cisper, M.E.; Alexander, M.L.; Hemberger, P.H.; Nogar, N.S.

1993-01-01

409

Laser desorption in an ion trap mass spectrometer  

SciTech Connect

Laser desorption in a ion-trap mass spectrometer shows significant promise for both qualitative and trace analysis. Several aspects of this methodology are discussed in this work. We previously demonstrated the generation of both negative and positive ions by laser desorption directly within a quadrupole ion trap. In the present work, we explore various combinations of d.c., r.f., and time-varying fields in order to optimize laser generated signals. In addition, we report on the application of this method to analyze samples containing compounds such as amines, metal complexes, carbon clusters, and polynuclear aromatic hydrocarbons. In some cases the ability to rapidly switch between positive and negative ion modes provides sufficient specificity to distinguish different compounds of a mixture with a single stage of mass spectrometry. In other experiments, we combined intensity variation studies with tandem mass spectrometry experiments and positive and negative ion detection to further enhance specificity.

Eiden, G.C.; Cisper, M.E.; Alexander, M.L.; Hemberger, P.H.; Nogar, N.S.

1993-02-01

410

Thermal diffusion desorption for the comprehensive analysis of organic compounds.  

PubMed

Comprehensive analysis of organic compounds is crucial yet challenging considering that information on elements, fragments, and molecules is unavailable simultaneously by current analytical techniques. Additionally, many compounds are insoluble or only dissolve in toxic solvents. A solvent- and matrix-free strategy has been developed which allows the organic compound analyzed in its original form. It utilizes thermal diffusion desorption with the solid analyte irradiated with high energy laser. It is capable of providing explicit elemental, fragmental, and molecular information simultaneously for a variety of organic compounds. Thermal diffusion desorption has many advantages compared to the electrospray and MALDI techniques. The protons that form the protonated molecular ions originate from the analyte itself. All the elements and fragments are also derived from the analyte itself, which provides abundant information and expedites the identification of organic compounds. PMID:24914465

Yin, Zhibin; Wang, Xiaohua; Li, Weifeng; He, Miaohong; Hang, Wei; Huang, Benli

2014-07-01

411

Single molecule desorption studies on immobilized nanoclay particle surfaces.  

PubMed

AFM-based single molecule force spectroscopy was performed on sheetlike inorganic particles of Na-montmorillonite to study the pH-dependent adsorption and desorption behavior of polyelectrolytes in aqueous solutions. Polyallylamine macromolecules were covalently attached on gold-coated AFM cantilevers. Heterogeneous surfaces were formed by immobilizing the nanoclay sheets on mica-stripped ultraflat Au(111) surfaces using aminothiol chemistry. Because of the constant surface charge of the particles over a wide pH range, polymer line charge density was the only parameter that affected the adsorption and desorption behavior when the ionic concentration was kept constant. Polarization modulation infrared-reflection absorption spectroscopy (PM-IRRAS) was performed on cast polyallylamine films to study the pH-dependent charge density of polyallylamine molecules. A good correlation was found between the line charge density and the adsorption characteristics of polyallylamine. PMID:20230055

Ozkaya, Berkem; Ozcan, Ozlem; Thissen, Peter; Grundmeier, Guido

2010-06-01

412

Analysis of airborne pesticides from different chemical classes adsorbed on Radiello® Tenax® passive tubes by thermal-desorption-GC/MS.  

PubMed

An analytical methodology using automatic thermal desorption (ATD) and GC/MS was developed for the determination of 28 pesticides of different chemical classes (dichlobenil, carbofuran, trifluralin, clopyralid, carbaryl, flazasulfuron, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, cyprodinil, bromoxynil, fluroxypyr, oxadiazon, myclobutanil, buprofezin, picloram, trinexapac-p-ethyl, ioxynil, diflufenican, tebuconazole, bifenthrin, isoxaben, alphacypermethrin, fenoxaprop and tau-fluvalinate) commonly used in nonagricultural areas in atmospheric samples. This methodology was developed to evaluate the indoor and outdoor atmospheric contamination by nonagricultural pesticides. Pesticides were sampled passive sampling tubes containing Tenax® adsorbent. Since most of these pesticides are polar (clopyralid, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, bromoxynil, fluroxypyr, picloram, trinexapac-p-ethyl and ioxynil), a derivatisation step is required. For this purpose, a silylation step using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MtBSTFA) was added before thermal desorption. This agent was chosen since it delivers very specific ions on electronic impact (m/z?=?M-57). This method was established with special consideration for optimal thermal desorption conditions (desorption temperature, desorb flow and duration; trap heating duration and flow; outlet split), linear ranges, limits of quantification and detection which varied from 0.005 to 10 ng and from 0.001 to 2.5 ng, respectively, for an uncertainty varied from 8 to 30 %. The method was applied in situ to the analysis of passive tubes exposed during herbicide application to an industrial site in east of France. PMID:25205153

Raeppel, Caroline; Fabritius, Marie; Nief, Marie; Appenzeller, Brice M R; Briand, Olivier; Tuduri, Ludovic; Millet, Maurice

2015-02-01

413

Laser-Desorption Supersonic Jet Spectroscopy of Phthalocyanines  

Microsoft Academic Search

The laser-induced fluorescence excitation spectra of zinc phthalocyanine, chloroaluminum phthalocyanine, magnesium phthalocyanine, and free-base phthalocyanine have been investigated under jet-cooled conditions, by using pulsed infrared laser desorption as the means of vaporization. Assignment of the observed vibronic transitions reveals that many of them gain intensity from coupling of theS1(Q) state with theS2(B) andQ' states. Low-frequency out-of-plane modes of the macrocycle

Fiona L. Plows; Anita C. Jones

1999-01-01

414

Laser-Desorption Supersonic Jet Spectroscopy of Phthalocyanines  

Microsoft Academic Search

The laser-induced fluorescence excitation spectra of zinc phthalocyanine, chloroaluminum phthalocyanine, magnesium phthalocyanine, and free-base phthalocyanine have been investigated under jet-cooled conditions, by using pulsed infrared laser desorption as the means of vaporization. Assignment of the observed vibronic transitions reveals that many of them gain intensity from coupling of theS1(Q) state with theS2(B) andQ? states. Low-frequency out-of-plane modes of the macrocycle

Fiona L. Plows; Anita C. Jones

1999-01-01

415

Increasing ion sorption and desorption rates of conductive electrodes  

SciTech Connect

An electrolyte system includes a reactor having a pair of electrodes that may sorb ions from an electrolyte. The electrolyte system also includes at least one power supply in electrical communication with the reactor. The at least one power supply may supply a DC signal and an AC signal to the pair of electrodes during sorption of the ions. In addition, the power supply may supply only the AC signal to the pair of electrodes during desorption of the ions.

DePaoli, David William; Kiggans, Jr., James O; Tsouris, Costas; Bourcier, William; Campbell, Robert; Mayes, Richard T

2014-12-30

416

Dehalogenation reactions in californium-252 plasma desorption mass spectrometry  

Microsoft Academic Search

Californium-252 plasma desorption mass spectrometry (PDMS) (2) is a particle-induced ionization method with the distinction that 100-MeV fission fragments are employed rather than the 6-keV xenon atoms used in fast atom bombardment (FAB) mass spectroscopy. More important to this discussion is that, because a time-of-flight spectrometer allows the use of very weak primary ion currents (1000 fission fragments\\/s), the glycerol

Yi Ming. Yang; Henry M. Fales; Lewis. Pannell

1985-01-01

417

Ultrasonic Enhanced Desorption of DDT from Contaminated Soils  

Microsoft Academic Search

In this study, using high-power low-frequency ultrasound, heated slurries with anionic surfactant sodium dodecyl sulfate (SDS)\\u000a were treated to enhance desorption of DDT from soils with high clay, silt, and organic matter content and different pH (5.6–8.4).\\u000a The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20 wt.%\\u000a were studied. For

Kandasamy Thangavadivel; Mallavarapu Megharaj; Roger St. C. Smart; Peter J. Lesniewski; Darren Bates; Ravi Naidu

2011-01-01

418

Adsorption, Desorption, and Dissociation of Benzene on TiO2(110) and Pd/TiO2(110)  

SciTech Connect

Adsorption and reaction of benzene molecules on clean TiO{sub 2}(110) and on TiO{sub 2}(110) with deposited Pd nanoparticles are investigated using a combination of scanning tunneling microscopy (STM), temperature-programmed desorption, and first-principles calculations. Above {approx}50 K, the one-dimensional motion of benzene between bridging oxygen rows is shown to be too fast for STM imaging. At 40 K benzene molecules form chains on top of titanium rows, with calculations indicating every other benzene is rotated 30{sup o}. Both experimental and theoretical studies find no dissociative reactivity of benzene on the clean TiO{sub 2}(110) surface, due to little hybridization between TiO{sub 2} and benzene electronic states. After deposition of Pd nanoparticles, molecular benzene is observed with STM both on the substrate and adjacent to metallic particles. Upon heating to 800 K, benzene fully breaks down into its atomic constituents in a multistep decomposition process.

Zhou, Jing [ORNL; Dag, Sefa [ORNL; Senanayake, Sanjaya D [ORNL; Hathorn, Bryan C [ORNL; Kalinin, Sergei V [ORNL; Meunier, Vincent [ORNL; Mullins, David R [ORNL; Overbury, Steven {Steve} H [ORNL; Baddorf, Arthur P [ORNL

2006-01-01

419

Simulated Desorption of Aluminum and Oxide Covered Aluminum  

NASA Astrophysics Data System (ADS)

There is evidence that laser or electron stimulated nonthermal desorption from aluminum can proceed through plasmon excitation processes. Arakawa et al. observed this phenomenon with Al films and Kim et al. observed it with direct laser irradiation. (E.T. Arakawa, I. Lee and T.A. Callcott in Laser Ablation, J.C. Miller and R.F. Haglund Eds., Springer-Verlag, NY, 82 (1991).; H. S. Kim and H. Helvjian, J. Phys. Chem. 95, 6623 (1991).) Dreyfus et al. found nonthermal Al neutral species from laser irradiation of Al_2O_3, Schildbach et al. measured nonthermal Al ions from a well characterized sapphire (1120) sample, and Pedraza et al. showed that for laser irradiation of both alumina and sapphire there is a change in the degree of oxidation of the surface Al.(R.W. Dreyfus, R. Kelly and R.E. Walkup, Appl. Phys. Lett. 49, 1478 (1986);M.A. Schildbach and A.V. Hamza, Phys. Rev. B. 45, 6197 (1992); Pedraza et al., AIP Proc., Vol. 288 (1993) pg. 329.) These experiments show that oxygen on Al does not quench the nonthermal desorption. We will present measurements of the Al yield and K. E. w.r.t. oxygen coverage and laser fluence. This stimulated desorption work has environmental relevance to the storage of oxidized Al clad nuclear fuel rods.

Helvajian, Henry

1998-03-01

420

Laser desorption lamp ionization source for ion trap mass spectrometry.  

PubMed

A two-step laser desorption lamp ionization source coupled to an ion trap mass spectrometer (LDLI-ITMS) has been constructed and characterized. The pulsed infrared (IR) output of an Nd:YAG laser (1064?nm) is directed to a target inside a chamber evacuated to ~15?Pa causing desorption of molecules from the target's surface. The desorbed molecules are ionized by a vacuum ultraviolet (VUV) lamp (filled with xenon, major wavelength at 148?nm). The resulting ions are stored and detected in a three-dimensional quadrupole ion trap modified from a Finnigan Mat LCQ mass spectrometer operated at a pressure of ? 0.004?Pa. The limit of detection for desorbed coronene molecules is 1.5?pmol, which is about two orders of magnitude more sensitive than laser desorption laser ionization mass spectrometry using a fluorine excimer laser (157?nm) as the ionization source. The mass spectrum of four standard aromatic compounds (pyrene, coronene, rubrene and 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (OPC)) shows that parent ions dominate. By increasing the infrared laser power, this instrument is capable of detecting inorganic compounds. PMID:25601688

Wu, Qinghao; Zare, Richard N

2015-01-01

421

Sorption-desorption of aminocyclopyrachlor in selected Brazilian soils.  

PubMed

Aminocyclopyrachlor sorption/desorption was investigated in 14 soils from Brazil, representing a range of pH, and organic carbon (OC) and clay contents. The Freundlich equation adequately described behavior of aminocyclopyrachlor in soil. Freundlich sorption coefficient (K(f)) values ranged from 0.06 to 1.64 and 1/n values for ranged from 0.9 to 1.0. Sorption was correlated to OC (K(f,oc) ranged from 11 to 64) and clay contents. The lowest sorption was found for soils with very low OC contents (0.50-0.65%) and loamy-sand to sand textures. The 1/n values for desorption were lower than those observed for sorption, suggesting that aminocyclopyrachlor sorption by soil was not reversible; hysteresis coefficients ranged from 0.13 to 0.74. The results suggest that although aminocyclopyrachlor would be very mobile based on its sorption coefficients, its potential depth of leaching may be overestimated due to the hysteretic desorption. PMID:21384924

Oliveira, Rubem S; Alonso, Diego G; Koskinen, William C

2011-04-27

422

Unexpected Analyte Oxidation during Desorption Electrospray Ionization - Mass Spectrometry  

SciTech Connect

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

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

2008-01-01

423

The desorptivity model of bulk soil-water evaporation  

NASA Technical Reports Server (NTRS)

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

Clapp, R. B.

1983-01-01

424

Nonideal Sorption-Desorption and Extensive Elution Tailing  

NASA Astrophysics Data System (ADS)

Contamination of subsurface environments by organic compounds continues to pose a risk to the environment. Sorption is a critical process that influences the transport and fate of organic contaminants. Contaminant mobility, bioavailability, and the effectiveness of remediation efforts are mediated in part by sorption/desorption processes. Miscible-displacement experiments were conducted to characterize long-term, low-concentration elution tailing associated with sorption/desorption processes. A variety of soils and aquifer sediments, representing a range of particle-size distributions and organic-carbon contents, were employed, and trichloroethene (TCE) was used as the model organic compound. Trichloroethene transport exhibited extensive elution tailing for all media, with several hundred to several thousand pore volumes of water flushing required to reach the detection limit (~0.1 ?g/L). The elution tailing was more extensive for the media with higher organic-carbon contents and associated retardation factors. However, when normalized by retardation, the extent of tailing did not correlate directly to organic-carbon content. These latter results suggest that differences in the geochemical nature of organic carbon (e.g., composition, structure) among the various media influenced observed behavior. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous-distribution function was used to successfully simulate trichloroethene transport, including the extensive elution tailing.

Russo, A. E.; Akyol, N. H.; Schnaar, G. A.; Johnson, G. R.; Yolcubal, I.; Brusseau, M. L.

2011-12-01

425

Adsorption and desorption of bivalent metals to hematite nanoparticles.  

PubMed

The use of commercially prepared hematite nanoparticles (37.0?nm) was studied as an adsorbent in the removal of Cd(II), Cu(II), Pb(II), and Zn(II) from aqueous solutions. Single-metal adsorption was studied as a function of metal and adsorbent concentrations, whereas binary metal competition was found to be dependent on the molar ratio between the competing metals. Competitive effects indicated that Pb had strong homogenous affinity to the nanohematite surface, and decreased adsorption of Cd, Cu, and Zn occurred when Pb was present in a binary system. Metal adsorption strength to nanohematite at pH 6.0 increased with metal electronegativity: Pb?>?Cu?>?Zn???Cd. Equilibrium modeling revealed that the Langmuir-Freundlich composite isotherm adequately described the adsorption and competitive effects of metals to nanohematite, whereas desorption was best described by the Langmuir isotherm. The desorption of metals from nanohematite was found to be pH dependent, with pH 4.0?>?pH 6.0?>?pH 8.0, and results showed that greater than 65% desorption was achieved at pH 4.0 within three 24-h cycles for all metals. PMID:21994178

Grover, Valerie A; Hu, Jinxuan; Engates, Karen E; Shipley, Heather J

2012-01-01

426

Dynamics of SiF4 desorption during etching of silicon by XeF2  

NASA Astrophysics Data System (ADS)

Time-of-flight distributions have been obtained for SiF4, the principal product of the spontaneous etching reaction between silicon and XeF2. The data were extracted from modulated beam mass spectrometric measurements of SiF+4 intensity as a function of time. Comparison of the velocity and energy distributions derived from the data to the corresponding Maxwell-Boltzmann distributions shows clearly that although the most probable values of the distributions are very close to those expected when the desorbed species are in thermal equilibrium with the surface, the average values are not. The etch product velocity and energy distributions are not characterized by a single temperature, but comprise both hot and cool populations. These results show that the etch product desorption process cannot be described as simple evaporation of weakly bound species in equilibrium with the surface. The nature of the relationship between formation and volatilization is discussed.

Houle, F. A.

1987-08-01

427

Thermal desorption study of air on laboratory analog of interstellar dusts  

NASA Astrophysics Data System (ADS)

Progress in the ultra high vacuum surface experiments allows us to simulate environments that exist in the dense interstellar medium. This enable us to study various physical and chemical parameters which are needed to explain the formation of complex molecules on the interstellar dust grains. Dense clouds have densities between 104 and 107 cm-3 and temperature as low as 8 K and impinging flux of molecular and atomic reactants. In this proceeding, we discussed on a new laboratory set-up which was recently built at S N Bose National Centre for Basic Sciences and presented thermal desorption study of air on olivine substrate which is a close analog of interstellar dust grains.

Acharyya, Kinsuk

2013-06-01

428

A Solid Trap and Thermal Desorption System with Application to a Medical Electronic Nose  

PubMed Central

In this paper, a solid trap/thermal desorption-based odorant gas condensation system has been designed and implemented for measuring low concentration odorant gas. The technique was successfully applied to a medical electronic nose system. The developed system consists of a flow control unit, a temperature control unit and a sorbent tube. The theoretical analysis and experimental results indicate that gas condensation, together with the medical electronic nose system can significantly reduce the detection limit of the nose system and increase the system's ability to distinguish low concentration gas samples. In addition, the integrated system can remove the influence of background components and fluctuation of operational environment. Even with strong disturbances such as water vapour and ethanol gas, the developed system can classify the test samples accurately.

Xu, Xuntao; Tian, Fengchun; Yang, Simon X.; Li, Qi; Yan, Jia; Ma, Jianwei

2008-01-01

429

Fabrication of chemical templates via selective laser-induced desorption of hexadecanethiol self-assembled monolayers  

NASA Astrophysics Data System (ADS)

A nonlinear photothermal laser patterning technique for rapid fabrication of chemical templates is demonstrated. Hexadecanethiol monolayers on Au-coated Si substrates are processed at ? = 532 nm, a 1/e2 spot diameter of d=2.8 ?m and ambient conditions. Local laser irradiation at high laser powers and short irradiation times in the micro-/millisecond range induces desorption of thiol molecules. The laser-depleted areas are backfilled with mercaptohexadecanoic acid in order to build up chemical templates. Atomic force microscopy, scanning electron microscopy and scanning Auger electron spectroscopy are used for characterization of these templates. In agreement with a selective laser process, the results indicate the formation of flat chemical patterns with well-defined boundaries. Complementary condensation experiments demonstrate the functionality of the patterns as hydrophilic/hydrophobic templates. In particular, upon decreasing the temperature below the dew point, selective formation of water droplets on the backfilled areas is observed.

Schröter, Anja; Mathieu, Mareike; Franzka, Steffen; Feydt, Jürgen; Irsen, Stephan; Hartmann, Nils

2013-08-01

430

High-Temperature-Turbine Technology Program: Phase II. Technology test and support studies. Design and development of the liquid-fueled high-temperature combustor for the Turbine Spool Technology Rig  

SciTech Connect

The concept selected by Curtiss-Wright for this DOE sponsored High Temperature Turbine Technology (HTTT) Program utilizes transpiration air-cooling of the turbine subsystem airfoils. With moderate quantities of cooling air, this method of cooling has been demonstrated to be effective in a 2600 to 3000/sup 0/F gas stream. Test results show that transpiration air-cooling also protects turbine components from the aggressive environment produced by the combustion of coal-derived fuels. A new single-stage, high work transpiration air-cooled turbine has been designed and fabricated for evaluation in a rotating test vehicle designated the Turbine Spool Technology Rig (TSTR). The design and development of the annular combustor for the TSTR are described. Some pertinent design characteristics of the combustor are: fuel, Jet A; inlet temperature, 525/sup 0/F; inlet pressure, 7.5 Atm; temperature rise, 2475/sup 0/F; efficiency, 98.5%; exit temperature pattern, 0.25; and exit mass flow, 92.7 pps. The development program was conducted on a 60/sup 0/ sector of the full-round annular combustor. Most design goals were achieved, with the exception of the peak gas exit temperature and local metal temperatures at the rear of the inner liner, both of which were higher than the design values. Subsequent turbine vane cascade testing established the need to reduce both the peak gas temperature (for optimum vane cooling) and the inner liner metal temperature (for combustor durability). Further development of the 60/sup 0/ combustor sector achieved the required temperature reductions and the final configuration was incorporated in the TSTR full-annular burner.

None

1981-06-01

431