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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

Temperature Programmed Desorption Study of Graphene Oxide  

Microsoft Academic Search

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

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

2009-01-01

3

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

4

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

Microsoft Academic Search

The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially,

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

2006-01-01

5

Reversible hydrogen adsorption on MoS sub 2 studied by temperature-programmed desorption and temperature-programmed reduction  

Microsoft Academic Search

The adsorption and desorption of hydrogen on MoSâ were studied using a combination of temperature-programmed desorption (TPD) and temperature-programmed reduction (TPR) with a control of the maximum temperature. Reversible hydrogen adsorption was observed in the temperature range of 375-500 K. MoSâ samples reduced in hydrogen at different temperatures behaved distinctively towards reversible hydrogen adsorption. The amount of the reversible hydrogen

X. S. Li; Q. Xin; X. X. Guo; P. Grange; B. Delmon

1992-01-01

6

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

SciTech Connect

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

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

1991-03-15

7

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

Microsoft Academic Search

This paper presents temperature programmed desorption (TPD) data for perdeuterated propylene carbonate (PC-dâ) condensed at cryogenic temperatures on Li films vapor deposited onto polycrystalline (poly) Au and Ag foils and represents an extension of previous work involving the reactivity of tetrahydrofuran (THF) toward Li supported on Ag(poly). The findings suggest that the product of the reaction between PC and metallic

Guorong Zhuang; Gary Chottiner; Daniel A. Scherson; Ernest B. Yeager

1995-01-01

8

Intermittent temperature-programmed desorption study of perovskites used for catalytic purposes  

NASA Astrophysics Data System (ADS)

A differential desorption technique, called intermittent temperature-programmed desorption (ITPD), was used to give new insights into the properties of La 1- xSr xCo 0.8Fe 0.2O 3 perovskites as a contribution to improve their performances with respect to various important application fields such as catalysis, electrocatalysis and solid oxide fuel cells (SOFC). Both ITPD and interrupted TPD (carried out at different heating rates) evidenced two distinct oxygen adsorbed states, desorbing at temperatures lower than 400 °C, corresponding to less than 5% of a compact monolayer of oxide ions. The first one, for low desorption temperatures (lower than 290 °C) exhibits a heat of adsorption (? H) distribution from 101 to 121 kJ mol -1. The second one, for higher desorption temperatures (between 290 and 400 °C) corresponds to ? H = 146 ± 4 kJ mol -1. Additionally, for temperatures higher than 400 °C, we observed a continuous desorption of oxygen species, probably originating from the sub-surface or semi-bulk, with an associated activation energy of desorption ?175 kJ mol -1.

Gaillard, F.; Joly, J. P.; Boréave, A.; Vernoux, P.; Deloume, J.-P.

2007-04-01

9

Temperature-Programmed Desorption of Oxalate from the Goethite Surface  

SciTech Connect

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

Boily, Jean F.

2007-08-31

10

Automatic apparatus for catalyst characterization by temperature-programmed reduction\\/desorption\\/oxidation  

Microsoft Academic Search

An apparatus is described for the automatic quantitative registration of reduction, desorption\\/adsorption, and oxidation phenomena which occur when a catalyst sample is heated or cooled under temperature programming in a flowing gas that contains either hydrogen or oxygen as the reactive component. The design considerations and the automation scheme are fully discussed. A typical example of the characterization of a

H. Boer; W. J. Boersma; N. Wagstaff

1982-01-01

11

Encapsulation of Gases in Zeolite 3A and Temperature Programmed Desorption of the Trapped Gases  

Microsoft Academic Search

Gases (Ar, N? and CO?) were encapsulated in zeolite 3A at high temperature (350ºC) and pressure (maximum pressure obtained from a gas cylinder). Temperature programmed desorption (TPD), with a linear temperature schedule, was applied to study the kinetics of the release of the trapped gases. The TPD spectra for argon show two peaks ( a large peak at about 350ºC

Yun-cheung Chan

1976-01-01

12

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

13

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

14

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

15

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

SciTech Connect

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

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

2007-11-15

16

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

SciTech Connect

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

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

2004-10-01

17

Injector-internal thermal desorption from edible oils performed by programmed temperature vaporizing (PTV) injection.  

PubMed

Injector-internal thermal desorption is a promising technique for the analysis of a wide range of food components (e.g., flavors) or food contaminants (e.g., solvent residues, pesticides, or migrants from packaging materials) in edible oils and fats or fatty food extracts. Separation from the fatty matrix occurs during injection. Using programmed temperature vaporizing (PTV) injection, the oily sample or sample extract was deposited on a small pack of glass wool from which the components of interest were evaporated and transferred into the column in splitless mode, leaving behind the bulk of the matrix. Towards the end of the analysis, the oil was removed by heating out the injector and backflushing the precolumn. The optimization dealt with the gas supply configuration enabling backflush, the injector temperature program (sample deposition, desorption, and heating out), separation of the sample liquid from the syringe needle and positioning it on a support, deactivation of the support surface, holding the plug of fused silica wool by a steel wire, and the analytical sequence maintaining adsorptivity at the desorption site low. It was performed for a mixture of poly(vinyl chloride) (PVC) plasticizers in oil or fatty food. Using MS in SIM, the detection limit was below 0.1 mg/kg for plasticizers forming single peaks and 1 mg/kg for mixtures like diisodecyl phthalate. For plasticizers, RSDs of the concentrations were below 10%; for the slip agents, oleamide and erucamide, it was 12%. The method of incorporating PTV injection was used for about one year for determining the migration from the gaskets of lids for glass jars into oily foods. PMID:17120821

Fankhauser-Noti, Anja; Grob, Koni

2006-10-01

18

Study of chemisorption and hydrogenation of 1-butene on platinum by temperature-programmed desorption  

SciTech Connect

The temperature-programmed desorption (TPD) chromatograms of 1-butene from platinum black comprised four peaks, A, B, C, and D, with peak maxima at about 265, 390, 580, and higher than 770 K, respectively. Peak A was identified to be 1-butene with a trace amount of n-butane. Peaks B and C were the mixtures of 1-butene and propylene. Peak D was methane. The methane and propylene were formed from chemisorbed 1-butene by decomposition as the temperature was raised during the subsequent TPD. The reactivities of various types of chemisorbed hydrogen previously detected by TPD were also investigated with regard to the hydrogenation of 1-butene. Two types of chemisorbed hydrogen, presumed to be present on the surface in the form of hydrogen atoms chemisorbed on top of platinum atoms and in the bridge form of molecular hydrogen, were found to react with 1-butene.

Tsuchiya, S.; Yoshioka, N.

1984-05-01

19

Initial adsorption and C-incorporation of organosilanes at Si(0 0 1) investigated by temperature-programmed desorption  

NASA Astrophysics Data System (ADS)

Temperature-programmed desorption (TPD) has been used to study the initial adsorption and C-incorporation of organosilanes [monomethylsilane (MMS), dimethylsilane (DMS) and trimethylsilane (TMS)] at Si(0 0 1) surfaces. Hydrogen was the only desorbing species observed in the TPD spectra from organosilanes. Organosilane molecules adsorb dissociatively on the Si(0 0 1) surfaces at room temperature. TPD spectra from DMS- and TMS-adsorbed Si surfaces present carbon-related hydrogen (H 2) desorption peaks from the initial adsorption. The carbon-incorporation ratio was found to be larger in the order of TMS > DMS > MMS, with the sticking probability of molecules being almost identical for the three organosilane molecules.

Senthil, K.; Suemitsu, M.

2005-04-01

20

Investigation of a Co-MgO-ZSM catalyst by temperature-programmed reduction, temperature-programmed desorption, and IR spectroscopy  

Microsoft Academic Search

The 32% Co-3% MgO-ZSM (SiO2\\/Al2O3=38) system has been studied by means of temperature-programmed reduction, temperature-programmed desorption, and IR spectroscopy. The data from temperature-programmed reduction show that cobalt exists on the surface of the catalyst in the form of Co2+, CoO, Co3O4, and CoO·MgO solid solutions. Reduction of the sample results in the formation of a very inhomogeneous surface with four

A. Yu. Krylova; A. L. Lapidus; S. D. Sominskii; L. F. Rar; A. Zukal; J. Ratkousky; M. Jancalkova; V. I. Yakerson

1992-01-01

21

The Influence of Ultraviolet Irradiation on the Surface Chemistry of Ztetraol Magnetic Hard Disk Lubricant: a Combined Temperature Programed Desorption and X-Ray Photoelectron Spectroscopic Study  

Microsoft Academic Search

Magnetic hard disks coated with ztetraol lubricant were characterized with temperature programed desorption (TPD) and X-ray\\u000a photoelectron spectroscopy (XPS). Ztetraol was found to have two adsorbed states, with desorption temperatures of ~650 and ~950 K.\\u000a The complete removal of the low temperature state by solvent extraction identified it as due to the mobile lubricant. Desorption\\u000a of the CF3 mass fragment was observed only

Paul M. Jones; Alexei Merzikline; Xiaoping Yan; Lei Li; Lang Dinh; Michael Stirniman; Huan Tang

22

Temperature-programmed reduction and temperature-programmed desorption studies of CuO\\/ZrO 2 catalysts  

Microsoft Academic Search

Copper\\/zirconia catalysts were prepared by an impregnation method. The reducibility and characteristics of the supported copper oxide catalysts with various copper loadings were revealed and determined by H2-TPR, CO-TPR, XRD and O2-TPD, respectively. Five H2-TPR peaks could be observed. In conjunction with the observations by X-ray diffraction (XRD), three temperature-programmed reduction (TPR) peaks with lower peak temperatures (namely, ?1, ?2

Ren-xian Zhou; Tie-ming Yu; Xiao-yuan Jiang; Fang Chen; Xiao-ming Zheng

1999-01-01

23

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

PubMed

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

Niwa, Miki; Katada, Naonobu

2013-10-01

24

Programmed-temperature desorption study of hydrogen adsorption on disperse and sintered group VIII metal blacks  

SciTech Connect

Data are presented on the thermodesorption of hydrogen from disperse and sintered Group VIII metal blacks. It is shown that the activation energy for desorption of chemisorbed molecular and atomic complexes of hydrogen increases in the noblemetal triads with increasing atomic number of the element, both in the case of disperse blacks (nonactivated adsorption) and in the case of sintered blacks (activated adsorption).

Babenkova, L.V.; Popova, N.M.

1986-02-01

25

Hydrogen absorption and temperature programmed desorption (TPD) studies of iron- and chromium-substituted ZrV/sub 2/  

SciTech Connect

The hydrogen absorption proterties of the alloys Zr(V/sub 1-x/Cr/sub x/)/sub 2/, x = 0.4 and 0.5, were studied at 450/sup 0/C from 10/sup -3/ atm to 10 atm. the alloy ZrV/sub 0.8/Cr/sub 1.2/ was studied at 350/sup 0/, 400/sup 0/, and 450/sup 0/C from 10/sup -3/ atm to 10 atm, and from these data partial molar enthalpies and entropies of solution were calculated for several hydride compositions. A free energy against cell volume plot of the cubic chromium-containing materials compared with earlier data on hexagonal as well as cubic iron-substituted alloys shows that electronic factors are probably more important than structural factors in determining the free energies of the ternary Zr(V/sub 1-x/B/sub x/)/sub 2/ systems. Temperature-programmed desorption (TPD) of several hydride compositions in the systems ZrV/sub 1.6/Fe/sub 0.4/H/sub y/ and ZrV/sub 1.2/Cr/sub 0.8/H/sub y/ revealed two distinct peaks. The TPD results appear to correlate with changes in the pressure-composition isotherms when plotted on a log-log plot. These changes may be related to thermodynamic changes in the desorption of hydrogen. The so called trapping model (Pfeiffer and Wipf, 1976; Flanagan, Wulff, and Bowerman, 1980) is presented as a possible explanation of the observed TPD behavior. 7 figures, 2 tables.

Mendelsohn, M.H.; Gruen, D.M.

1981-01-01

26

Quantification of lateral repulsion between coadsorbed CO and N on Rh(100) using temperature-programmed desorption, low-energy electron diffraction, and Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption of CO coadsorbed with atomic N on Rh(100), reveals both long- and short-range interactions between adsorbed CO and N. For CO desorption from Rh(100) at low coverage we find an activation energy Ea of 137+/-2 kJ/mol and a preexponential factor of 1013.8+/-0.2 s-1. Coadsorption with N partially blocks CO adsorption and destabilizes CO by lowering Ea for CO desorption. Destabilization at low N coverage is explained by long-range electronic modification of the Rh(100) surface. At high N and CO coverage, we find evidence for a short-range repulsive lateral interaction between COads and Nads in neighboring positions. We derive a pairwise repulsive interaction ?CO-NNN=19 kJ/mol for CO coadsorbed to a c(2×2) arrangement of N atoms. This has important implications for the lateral distribution of coadsorbed CO and N at different adsorbate coverages. Regarding the different lateral interactions and mobility of adsorbates, we propose a structural model which satisfactorily explains the observed effects of atomic N on the desorption of CO. Dynamic Monte Carlo simulations were used to verify the experimentally obtained value for the CO-N interaction, by using the kinetic parameters and interaction energy derived from the temperature-programmed desorption experiments.

van Bavel, A. P.; Hopstaken, M. J. P.; Curulla, D.; Niemantsverdriet, J. W.; Lukkien, J. J.; Hilbers, P. A. J.

2003-07-01

27

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

PubMed Central

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

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

2013-01-01

28

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

SciTech Connect

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

Tewell, Craig R.

2002-08-19

29

Simultaneous quantitation of volatile compounds in citrus beverage through stir bar sorptive extraction coupled with thermal desorption-programmed temperature vaporization.  

PubMed

Due to disparate concentrations and physiochemical properties of analytes, difficulties in terms of sensitivity and reproducibility are commonly encountered in flavour analysis. In this study, we attempted to improve the performance of stir bar sorptive extraction coupled with thermal desorption and programmed temperature vaporization (SBSE-TD-PTV) based on a model citrus beverage. Through response surface methodology, thermal desorption conditions (i.e. desorption flow, thermal desorption time and cryofocusing temperature) were optimised based on constrained optimisation. Solute discrimination during injection was alleviated by normalising the variability of peak responses of different analytes. In addition, the effects of extraction conditions (i.e. ionic strength, stirring speed, extraction time, temperature and pH) were also investigated using partial factorial design. The obtained method showed high precision and good linearity over the concentration ranged from 0.10 to 20.00 ?g L(-1) with the correlation coefficients higher than 0.991 for most of the selected chemicals, except indole. The limit of detection ranged from 0.03 to 3.89 ?g L(-1). Hence, our results indicated that through the systematic study, SBSE-TD-PTV method became much less solute discriminative and more reliable to quantitate complex analytes. PMID:23598201

Cheong, Mun Wai; Lee, Justin Yong Kiang; Liu, Shao Quan; Zhou, Weibiao; Nie, Yunyun; Kleine-Benne, Eike; Curran, Philip; Yu, Bin

2013-03-30

30

A Study of Ethanol Reactions over Pt\\/CeO 2 by Temperature-Programmed Desorption and in Situ FT-IR Spectroscopy: Evidence of Benzene Formation  

Microsoft Academic Search

The reaction of ethanol over unreduced and H2-reduced 1 wt% Pt\\/CeO2 has been investigated primarily by temperature-programmed desorption (TPD) and in situ Fourier transform infrared spectroscopy (FT-IR). Steady state reactions have been conducted to provide information regarding the kinetics of the above reaction. Characterisation of the catalyst has been achieved through the use of XPS and titration of surface metal

Anna Yee; Scott J. Morrison; Hicham Idriss

2000-01-01

31

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

SciTech Connect

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

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

2007-01-01

32

Temperature-programmed desorption investigation of the adsorption and reaction of butene isomers on Pt(111) and ordered Pt-Sn surface alloys  

SciTech Connect

The influence of alloyed Sn on the chemistry of C{sub 4} butene isomers, including 1-butene, cis-2-butene, and isobutene, chemisorbed on Pt(111) was investigated by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy electron diffraction (LEED). Pt-Sn alloy chemistry was probed by investigation of two ordered surface alloys formed when Sn atoms were incorporated within the topmost layer on a Pt(111) substrate. All three butenes undergo decomposition on Pt(111) during TPD which accounts for 50-60% of the chemisorbed monolayer. Alloying Sn into the surface causes a large reduction in the reactivity of the surface, and the fraction of the chemisorbed layer which decomposes is decreased to 3-7% on the (2 x 2) alloy, and no decomposition occurs on the ({radical}3 x {radical}3)R30{degree} alloy. The strong reduction of decomposition on these two surface alloys may be due to the elimination of adjacent pure Pt 3-fold hollow sites. No large changes occur in the coverage of chemisorbed monolayer of butenes in the presence of up to 33% of a monolayer of alloyed Sn, showing that the adsorption ensemble requirement for chemisorption of these alkenes on Pt(111) and the two Sn/Pt(111) alloys is at most a few Pt atoms. 39 refs., 15 figs., 1 tab.

Tsai, Y.L.; Koel, B.E. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

1997-04-10

33

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

National Technical Information Service (NTIS)

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

E. Morales de Leguizamon

1984-01-01

34

Determination of the adsorption heat of n-hexane and n-heptane on zeolites beta, L, 5A, 13X, Y and ZSM-5 by means of quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA)  

Microsoft Academic Search

Measurements of temperature-programmed desorption and adsorption of n-hexane and n-heptane under quasi-equilibrium conditions (QE-TPDA) were performed for several zeolites in TPD apparatus equipped with a TCD detector. One-step adsorption profiles for zeolites X and Y and two-step adsorption profiles for beta, L, 5A and ZSM-5 were observed. Approximate adsorption isobars calculated from the QE-TPDA profiles did not depend on the

Wac?aw Makowski; ?ukasz Ogorza?ek

2007-01-01

35

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

36

Electronic Desorption from Internal Surfaces of Porous Low Temperature Ice  

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

37

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

PubMed

Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1-10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH2(+). PMID:24517785

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

2014-01-01

38

Probing the interaction of hydrogen chloride with low-temperature water ice surfaces using thermal and electron-stimulated desorption.  

PubMed

The interaction and autoionization of HCl on low-temperature (80-140 K) water ice surfaces has been studied using low-energy (5-250 eV) electron-stimulated desorption (ESD) and temperature programmed desorption (TPD). There is a reduction of H(+) and H(2)(+) and a concomitant increase in H(+)(H(2)O)(n=1-7) ESD yields due to the presence of submonolayer quantities of HCl. These changes are consistent with HCl induced reduction of dangling bonds required for H(+) and H(2)(+) ESD and increased hole localization necessary for H(+)(H(2)O)(n=1-7) ESD. For low coverages, this can involve nonactivated autoionization of HCl, even at temperatures as low as 80 K; well below those typical of polar stratospheric cloud particles. The uptake and autoionization of HCl is supported by TPD studies which show that for HCl doses ?0.5 ± 0.2 ML (ML = monolayer) at 110 K, desorption of HCl begins at 115 K and peaks at 180 K. The former is associated with adsorption of a small amount of molecular HCl and is strongly dependent on the annealing history of the ice. The latter peak at 180 K is commensurate with desorption of HCl via recombinative desorption of solvated separated ion pairs. The activation energy for second-order desorption of HCl initially in the ionized state is 43 ± 2 kJ/mol. This is close to the zero-order activation energy for ice desorption. PMID:21548613

Olanrewaju, Babajide O; Herring-Captain, Janine; Grieves, Gregory A; Aleksandrov, Alex; Orlando, Thomas M

2011-06-16

39

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

40

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...

41

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. ...

42

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. ...

43

Investigation of the interaction of benzene with vanadium-molybdenum oxide catalysts by programmed thermal desorption  

SciTech Connect

Programmed thermal desorption was used to investigate the interaction of benzene with vanadium-molybdenum oxide catalysts. It was established that the amount of maleic anhydride desorbed from the catalyst surface depends on the catalyst composition and that it varies with its activity and selectivity.

Belokopytov, Yu.V.; Pyatnitskii, Yu.I.; Grebennikov, Yu.N.

1985-09-01

44

Effect of temperature on the sorption and desorption of perfluorooctane sulfonate on humic acid.  

PubMed

Sorption and desorption of perfluorooctane sulfonate (PFOS) on humic acid at different temperatures were studied. It was found that the sorption process could be modeled with power kinetic equation very well, suggesting that diffusion predominated the sorption of PFOS on the humic acid. The sorption capacity was doubled when the temperature increased from 5 to 35 degrees C, and thermodynamics parameters deltaG0 was calculated to be -7.11 to -5.04 kJ/mol, AHo was 14.2 kJ/mol, and deltaS0 was 69.5 J/(mol x K), indicating that the sorption was a spontaneous, endothermic, and entropy driven process. Desorption hysteresis occurred at all studied temperatures which suggested that humic acid may be an important sink of PFOS in the environment. PMID:20614776

Jia, Chengxia; You, Chun; Pan, Gang

2010-01-01

45

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

EPA Science Inventory

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

46

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

47

Adsorption, diffusion, dewetting, and entrapment of acetone on Ni(111), surface-modified silicon, and amorphous solid water studied by time-of-flight secondary ion mass spectrometry and temperature programmed desorption  

NASA Astrophysics Data System (ADS)

Interactions of acetone with the silicon surfaces terminated with hydrogen, hydroxyl, and perfluorocarbon are investigated; results are compared to those on amorphous solid water (ASW) to gain insights into the roles of hydrogen bonds in surface diffusion and hydration of acetone adspecies. The surface mobility of acetone occurs at ~60 K irrespective of the surface functional groups. Cooperative diffusion of adspecies results in a 2D liquid phase on the H- and perfluorocarbon-terminated surfaces, whereas cooperativity tends to be quenched via hydrogen bonding on the OH-terminated surface, thereby forming residues that diffuse slowly on the surface after evaporation of the physisorbed species (i.e., 2D liquid). The interaction of acetone adspecies on the non-porous ASW surface resembles that on the OH-terminated Si surface, but the acetone molecules tend to be hydrated on the porous ASW film, as evidenced by their desorption during the glass-liquid transition and crystallization of water. The roles of micropores in hydration of acetone molecules are discussed from comparison with the results using mesoporous Si substrates.

Souda, Ryutaro

2011-10-01

48

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

EPA Science Inventory

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

49

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

EPA Science Inventory

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

50

Finite-temperature hydrogen adsorption and desorption thermodynamics driven by soft vibration modes.  

PubMed

It has been widely accepted that enhanced dihydrogen adsorption is required for room-temperature hydrogen storage on nanostructured porous materials. Here we report, based on results of first-principles total energy and vibrational spectrum calculations, finite-temperature adsorption and desorption thermodynamics of hydrogen molecules that are adsorbed on the metal center of metal-porphyrin-incorporated graphene. We have revealed that the room-temperature hydrogen storage is achievable not only with the enhanced adsorption enthalpy, but also with soft-mode driven vibrational entropy of the adsorbed dihydrogen molecule. The soft vibration modes mostly result from multiple orbital coupling between the hydrogen molecule and the buckled metal center, for example, in Ca-porphyrin-incorporated graphene. Our study suggests that the current design strategy for room-temperature hydrogen storage materials should be modified with explicitly taking the finite-temperature vibration thermodynamics into account. PMID:23971592

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

2013-08-01

51

Deuterium desorption temperature of Mg-Ti composites prepared by the method of atom-by-atom component mixing  

NASA Astrophysics Data System (ADS)

The plasma evaporation-sputtering method has been applied to obtain composite materials of the Mg-Ti system. Variations in the temperature of the ion-implanted deuterium desorption as a function of the component concentration are studied. It has been established, that introduction of titanium into magnesium leads to the significant decrease of deuterium desorption temperature, namely, to 400-450 K as compared to ~800 K in the case of deuterium release (desorption) from magnesium. The step-like shape of the deuterium desorption temperature curve evidences on the existence of two different structural states of the Mg-Ti composite depending on the ratio of components. The deuterium temperature drop can be caused by filamentary inclusions composed of titanium atoms in magnesium (insoluble component in magnesium) produced in the process of composite formation and providing the deuterium release from the sample at lower temperature (channels for deuterium diffusion and desorption through the surface barrier). The deuterium desorption data obtained on the example of Mg-Ti composites provide a support for further research into hydrogen storage materials containing not readily soluble chemical elements in the alloy components.

Morozov, O. M.; Kulish, V. G.; Zhurba, V. I.; Neklyudov, I. M.; Progolaieva, V. O.; Kuprin, A. S.; Lomino, N. S.; Ovcharenko, V. D.; Kolodiy, I. V.; Galitskiy, O. G.

2013-12-01

52

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.

53

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

Microsoft Academic Search

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

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

2009-01-01

54

Influence of temperature on PCDD/PCDF desorption from waste incineration flyash under nitrogen.  

PubMed

A municipal solid waste incinerator flyash was heated to between 200 and 400 degrees C under nitrogen in a bench-scale, static bed reactor for 4 days soak time. The influence of temperature on the levels of PCDD and PCDF remaining in and desorbed from the ash were investigated using GC-MS/MS. PCDD and especially PCDF formation was seen on the flyash between 225 and 300 degrees C. Large increases in the I-TEQ of the treated ash relative to the increase in its overall PCDD/PCDF content indicated that the formation of 2378-substituted congeners was favoured over that of other substitution patterns. In the absence of a source of gaseous oxygen, formation was mainly attributed to de novo reactions involving solid phase oxygen. Dechlorination of the PCDD/PCDF in flyash became increasingly important above 275 degrees C. Maximum desorption was seen at 325 degrees C, with the equivalent of 35 wt% of the PCDD/F in the original flyash being recovered from the exhaust traps at this temperature. The desorbed species were mainly M(1)CDD/CDDF-T(3)CDD/CDDF resulting from dechlorination of higher chlorinated PCDD/PCDF, with consequently low I-TEQ values. PMID:16844194

Cunliffe, Adrian M; Williams, Paul T

2007-01-01

55

Retrospective identification of chemical warfare agents by high-temperature automatic thermal desorption–gas chromatography–mass spectrometry  

Microsoft Academic Search

An automated thermal desorption (ATD)–gas chromatography–mass spectrometry method was developed for the analysis of selected chemical warfare (CW) agents. Suitable methods were developed for analytes of high volatility to low volatility. The less volatile CW agents required the purchase and installation of a high-temperature valve upgrade kit allowing valve temperatures of up to 260°C to be reached. The limit of

Wendy A. Carrick; David B. Cooper; Bob Muir

2001-01-01

56

Programmed-Temperature Normal Freezing  

Microsoft Academic Search

A normal freezing apparatus is described where the cooling-bath temperature can be programmed between 0.5 × 10 and 6.0°C\\/mm. Runs with n-hexadecane\\/n-tetradecane test mixtures indicate that improved efficiencies result from programming the cooling bath during the run.

T. H. Gouw

1967-01-01

57

Characterization by temperature programmed reduction  

Microsoft Academic Search

Fresh and used EUROCAT Oxide-2 catalyst made up of V2O5, WO3 and TiO2 with SiO2, Al2O3 and CaO as main additives have been studied by means of temperature programmed reduction (TPR). As in the EUROCAT Oxide-1 project (V2O5\\/TiO2 catalysts) for similar conditions similar profiles were obtained in the different laboratories. In contrast to the V2O5\\/TiO2 catalysts (EUROCAT Oxide-1 project), where

M. A Reiche; M Maciejewski; A Baiker

2000-01-01

58

Temperature-Programmed Reduction and HDS Activity of Sulfided Transition Metal Catalysts: Formation of Nonstoichiometric Sulfur  

Microsoft Academic Search

Sulfided alumina-supported transition metal catalysts have been studied using temperature-programmed reduction (TPR). The H2 and H2S concentrations were determined simultaneously and the major processes occurring were discriminated, namely reduction of oxidic and sulfidic species and desorption of H2S. Because of the high maximum reduction temperature and the high hydrogen partial pressure applied, a complete description of all species was acquired,

P. J. Mangnus; A. Riezebos; A. D. Vanlangeveld; J. A. Moulijn

1995-01-01

59

Desorption kinetics from a surface derived from direct imaging of the adsorbate layer.  

PubMed

There are numerous indications that adsorbed particles on a surface do not desorb statistically, but that their spatial distribution is important. Evidence almost exclusively comes from temperature-programmed desorption, the standard method for measuring desorption rates. However, this method, as a kinetics experiment, cannot uniquely prove an atomic mechanism. Here we report a low-energy electron microscopy investigation in which a surface is microscopically imaged while simultaneously temperature-programmed desorption is recorded. The data show that during desorption of oxygen molecules from a silver single crystal surface, islands of oxygen atoms are present. By correlating the microscopy and the kinetics data, a model is derived that includes the shapes of the islands and assumes that the oxygen molecules desorb from the island edges. The model quantitatively reproduces the complex desorption kinetics, confirming that desorption is affected by islands and that the often used mean-field treatment is inappropriate. PMID:24834863

Günther, S; Mente?, T O; Niño, M A; Locatelli, A; Böcklein, S; Wintterlin, J

2014-01-01

60

Desorption kinetics from a surface derived from direct imaging of the adsorbate layer  

NASA Astrophysics Data System (ADS)

There are numerous indications that adsorbed particles on a surface do not desorb statistically, but that their spatial distribution is important. Evidence almost exclusively comes from temperature-programmed desorption, the standard method for measuring desorption rates. However, this method, as a kinetics experiment, cannot uniquely prove an atomic mechanism. Here we report a low-energy electron microscopy investigation in which a surface is microscopically imaged while simultaneously temperature-programmed desorption is recorded. The data show that during desorption of oxygen molecules from a silver single crystal surface, islands of oxygen atoms are present. By correlating the microscopy and the kinetics data, a model is derived that includes the shapes of the islands and assumes that the oxygen molecules desorb from the island edges. The model quantitatively reproduces the complex desorption kinetics, confirming that desorption is affected by islands and that the often used mean-field treatment is inappropriate.

Günther, S.; Mente?, T. O.; Niño, M. A.; Locatelli, A.; Böcklein, S.; Wintterlin, J.

2014-05-01

61

Annealing effect reversal by water sorption-desorption and heating above the glass transition temperature-comparison of properties.  

PubMed

Our objective is to compare the physical properties of materials obtained from two different methods of annealing reversal, that is, water sorption-desorption (WSD) and heating above glass transition temperature (HAT). Trehalose was annealed by storing at 100 °C for 120 h. The annealing effect was reversed either by WSD or HAT, and the resulting materials were characterized by differential scanning calorimetry (DSC), water sorption studies, and positron annihilation spectroscopy (PAS). While the products obtained by the two methods of annealing reversal appeared to be identical by conventional characterization methods, they exhibited pronounced differences in their water sorption behavior. Positron annihilation spectroscopy (PAS), by measuring the fractional free volume changes in the processed samples, provided a mechanistic explanation for the differences in the observed behavior. PMID:23834191

Saxena, A; Jean, Y C; Suryanarayanan, R

2013-08-01

62

Probing low-temperature water ice phases using electron-stimulated desorption  

SciTech Connect

Low-energy electron-stimulated desorption (ESD) of D+ from D2O has been used to examine the phase and growth behavior of nanoscale vapor-deposited ice films grown on Pt(111) between 90-155 K. The D+ yield from porous amorphous solid water (deposited at 90 K) shows evidence for sintering near 120 K, increases between 120-140 K, and then drops at the amorphous-crystalline phase transition near 155 K. Ice deposited at 155 K forms at epitaxial crystalline film, with a D+ yield nearly one-third larger than the yield from crystalline films prepared by annealing the amorphous phase. This suggests that the film formed by annealing may have a different crystalline ordering or morphology than the epitaxial film deposited between 150-155 K. Ice deposited at 90 K on-top of the expitaxial film is amorphous but crystallizes to a form similar to that of the underlying crystalline ice substrate. This suggests that in this case, the buried two-dimensional interface nucleates the crystallization.

Orlando, Thomas M.; Sieger, Matthew T.

2000-04-20

63

Application Guide for Thermal Desorption Systems.  

National Technical Information Service (NTIS)

This guide is intended to provide the Remediation Project Manager with guidance on implementing the use of thermal desorption systems at remedial action sites. The technology is referred to as either Low Temperature Thermal Desorption or High Temperature ...

D. Pal S. Fann S. Wight

1998-01-01

64

Thermal desorption of CO from Mo(110)  

NASA Astrophysics Data System (ADS)

Adsorption of CO on Mo(110) has been studied by temperature programmed desorption (TPD), photoelectron spectroscopy, and Monte-Carlo simulations. Carbon monoxide is partly dissociated when adsorbed on this surface at ambient temperatures. Two desorption regions, 250-400 K (molecular adsorption) and 850-1100 K (dissociative adsorption) are observed in the TPD spectra. Molecular species were identified by orbitals present in the photoemission measurements. It was found that the desorption signal corresponding to dissociative adsorption saturates rapidly for CO exposures below 1L, whereas the desorption intensity corresponding to molecular adsorption increases with exposure up to about 5L. Interpretation of desorption data is generally not straight forward due to the dependence of several properties of the surface and absorbed species. Therefore, the experimental data for the molecular adsorption region has been compared to Monte-Carlo simulations. The algorithm proposed by Meng and Weinberg [1] was employed. The presence of dissociated species on the surface has been modeled. Two different adsorption sites, "on-top" and "bridge" sites, was considered. Three different near neighbor interactions on the bcc(110) surface have been included. [1] B.Meng and W.H. Weinberg, J. Chem. Phys. 100, 5280 (1994).

Raaen, S.; Juel, M.

2003-03-01

65

The desorption of H2CO from interstellar grains analogues  

NASA Astrophysics Data System (ADS)

Context. Much of the formaldehyde (H2CO) is formed from the hydrogenation of CO on interstellar dust grains, and is released in the gas phase in hot core regions. Radio-astronomical observations in these regions are directly related to its desorption from grains. Aims: We study experimentally the thermal desorption of H2CO from bare silicate surfaces, from water ice surfaces and from bulk water ice in order to model its desorption from interstellar grains. Methods: Temperature-programmed desorption experiments, monitored by mass spectrometry, and Fourier transform infrared spectroscopy are performed in the laboratory to determine the thermal desorption energies in: (i.) the multilayer regime where H2CO is bound to other H2CO molecules; (ii.) the submonolayer regime where H2CO is bound on top of a water ice surface; (iii.) the mixed submonolayer regime where H2CO is bound to a silicate surface; and (iv.) the multilayer regime in water ice, where H2CO is embedded within a H2O matrix. Results: In the submonolayer regime, we find the zeroth-order desorption kinetic parameters ?0 = 1028 mol cm-2 s-1 and E = 31.0 +/-0.9 kJ mol-1 for desorption from an olivine surface. The zeroth-order desorption kinetic parameters are ?0 = 1028 mol cm-2 s-1 and E = 27.1 +/-0.5 kJ mol-1 for desorption from a water ice surface in the submonolayer regime. In a H2CO:H2O mixture, the desorption is in competition with the H2CO + H2O reaction, which produces polyoxymethylene, the polymer of H2CO. This polymerization reaction prevents the volcano desorption and co-desorption from happening. Conclusions: H2CO is only desorbed from interstellar ices via a dominant sub-monolayer desorption process (E = 27.1 +/ - 0.5 kJ mol-1). The H2CO which has not desorbed during this sub-monolayer desorption polymerises upon reaction with H2O, and does not desorb as H2CO at higher temperature.

Noble, J. A.; Theule, P.; Mispelaer, F.; Duvernay, F.; Danger, G.; Congiu, E.; Dulieu, F.; Chiavassa, T.

2012-07-01

66

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

PubMed

The effects of temperature and sediment-chemical contact time on desorption and bioaccumulation of sediment-spiked (14)C-labelled 2,2',4,4'-tetrabromo diphenyl ether (BDE-47) and benzo(a)pyrene (BaP) were examined. Experiments were performed after 2 or 6 weeks and 23 or 24 months sediment-chemical contact time at 10 and 20 degrees C. Desorption was measured in a sediment-water suspension using Tenax extraction, and bioaccumulation was measured by exposing Lumbriculus variegatus (Oligochaeta) to BDE-47 and BaP-spiked sediments in a 10d kinetic study. Biota-sediment accumulation factors (BSAFs) ranged between 2.9 and 4.3 for BDE-47 and between 0.5 and 0.9 for BaP. Thus, temperature and aging had a minor effect on bioavailability estimates. On the other hand, the difference between the chemicals was clear and could not be interpreted solely by reference to the size of the desorbing fractions, although the rapidly desorbing fraction-revised estimate clearly reduced the difference. The remaining discrepancy may be related to methodological (Tenax extraction vs. worm exposure) and/or biological (digestive extraction) causes. However, the data support the role of diffusional forces in the bioavailability of sediment-associated organic contaminants. Therefore, desorption-revised bioavailability estimates would lead to more precise bioavailability estimates than the traditional sediment organic carbon-organisms' lipids-based equilibrium partitioning approach. PMID:18973943

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

2009-05-01

67

STP Temperature Measurement Lennard-Jones Program  

NSDL National Science Digital Library

The STP TemperatureMeasurementLJ program simulates the exchange energy between a demon and a system of particles interacting via the Lennard-Jones potential. The program shows the kinetic temperature of the system as a function of time, and the energy distribution of the demon. The purpose of this simulation is to understand why the demon acts as an ideal thermometer The default system is a one-dimensional ideal gas of N=64 particles in a box with linear dimension 30 and initial kinetic energy per particle of 1.0. Additional states and parameters can be specified using the Display|Switch GUI menu item. STP TemperatureMeasurementLJ is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_TemperatureMeasurementLJ.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2009-03-03

68

STP Temperature Measurement Ideal Gas Program  

NSDL National Science Digital Library

The STP DemonIdealGas program displays a histogram of the energy of a demon that exchanges energy with an ideal gas of particles. The purpose of this simulation is to understand why the demon acts as a perfect thermometer and why its mean energy is a measure of the temperature of the gas. The default system is a one-dimensional ideal gas of N=40 particles. Additional states and parameters can be specified using the Display|Switch GUI menu item. STP DemonIdealGas is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_DemonIdealGas.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-05-28

69

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

Microsoft Academic Search

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

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

2002-01-01

70

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

Microsoft Academic Search

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

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

2002-01-01

71

Ion desorption from H2O chemisorbed on Si(100) by O 1s electron excitation at room temperature  

Microsoft Academic Search

The photon stimulated ion desorption (PSID) of H+ and O+ from monolayer H2O adsorbed on the Si(100) has been studied using pulsed synchrotron radiation in the 510–620 eV range. Ions were detected and mass analyzed by means of time-of-flight spectroscopy. Relative yield spectra of these ions indicated characteristic behavior near the O K edge. The predominant H+ fragment ion shows

Tetsuhiro Sekiguchi; Hiromi Ikeura; Kenichiro Tanaka; Kinichi Obi; Nobuo Ueno; Kenji Honma

1995-01-01

72

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

73

Desorption of chlorine organic solvents  

SciTech Connect

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

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

1982-03-01

74

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

75

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

76

Indium nitride surface structure, desorption kinetics and thermal stability  

NASA Astrophysics Data System (ADS)

Unique physical properties such as small effective mass, high electron drift velocities, high electron mobility and small band gap energy make InN a candidate for applications in high-speed microelectronic and optoelectronic devices. The aim of this research is to understand the surface properties, desorption kinetics and thermal stability of InN epilayers that affect the growth processes and determine film quality as well as device performance and life time. We have investigated the structural properties, the surface desorption kinetics, and the thermal stability using Auger electron spectroscopy (AES), x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high resolution electron energy loss spectroscopy (HREELS), and temperature programmed desorption (TPD). Investigations on high pressure chemical vapor deposition (HPCVD)-grown InN samples revealed the presence of tilted crystallites, which were attributed to high group V/III flux ratio and lattice mismatch. A study of the thermal stability of HPCVD-grown InN epilayers revealed that the activation energy for nitrogen desorption was 1.6+/-0.2 eV, independent of the group V/III flux ratio. Initial investigations on the ternary alloy In0.96Ga0.04N showed single-phase, N-polar epilayers using XRD and HREELS, while a thermal desorption study revealed an activation energy for nitrogen desorption of 1.14 +/- 0.06 eV. HREELS investigations of atomic layer epitaxy (ALE)-grown InN revealed vibrational modes assigned to N-N vibrations. The atomic hydrogen cleaned InN surface also exhibited modes assigned to surface N-H without showing In-H species, which indicated N-polar InN. Complete desorption of hydrogen from the InN surface was best described by the first-order desorption kinetics with an activation energy of 0.88 +/- 0.06 eV and pre-exponential factor of (1.5 +/- 0.5) x105 s-1. Overall, we have used a number of techniques to characterize the structure, surface bonding configuration, thermal stability and hydrogen desorption kinetics of InN and In0.96Ga0.04N epilayers grown by HPCVD and ALE. High group V/III precursors ratio and lattice mismatch have a crucial influence on the film orientation. The effects of hydrogen on the decomposition add to the wide variation in the activation energy of nitrogen desorption. Presence of surface defects lowers the activation energy for hydrogen desorption from the surface.

Acharya, Ananta

77

Downscaling daily extreme temperatures with genetic programming  

NASA Astrophysics Data System (ADS)

A context-free genetic programming (GP) method is presented that simulated local scale daily extreme (maximum and minimum) temperatures based on large scale atmospheric variables. The method evolves simple and optimal models for downscaling daily temperature at a station. The advantage of the context-free GP method is that both the variables and constants of the candidate models are optimized and consequently the selection of the optimal model. The method is applied to the Chute-du-Diable weather station in Northeastern Canada along with the National Center for Environmental Prediction (NCEP) reanalysis datasets. The performance of the GP based downscaling models is compared to benchmarks from a commonly used statistical downscaling model. The experiment results show that the models evolved by the GP are simpler and more efficient for downscaling daily extreme temperature than the common statistical method. The different model test results indicate that the GP approach significantly outperforms the statistical method for the downscaling of daily minimum temperature, while for the maximum temperature the two methods are almost equivalent. However, the GP method remains slightly more effective for maximum temperature downscaling than the statistical method.

Coulibaly, Paulin

2004-08-01

78

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

79

Temperature-programmed desorption and photoluminescence studies of thorium dioxide surface states  

Microsoft Academic Search

A mass spectroscopic study of the species desorbed from oxygen- or hydrogen-treated thorium dioxide and photoluminescence studies suggested that the fully hydrated thorium dioxide surface contains three anionic species: oxide lattice ions, hydroxyl ions, and vacancies. The stepwise mechanism of dehydration of the surface is analyzed and its relationship to acid-base properties of the surface and catalytic activity discussed.

M. Breysse; B. Claudel; L. Faure; M. Guenin

1979-01-01

80

Temperature-programmed desorption and photoluminescence studies of thorium dioxide surface states  

SciTech Connect

A mass spectroscopic study of the species desorbed from oxygen- or hydrogen-treated thorium dioxide and photoluminescence studies suggested that the fully hydrated thorium dioxide surface contains three anionic species: oxide lattice ions, hydroxyl ions, and vacancies. The stepwise mechanism of dehydration of the surface is analyzed and its relationship to acid-base properties of the surface and catalytic activity discussed.

Breysse, M.; Claudel, B.; Faure, L.; Guenin, M.

1979-06-01

81

Cyclic CO2 chemisorption-desorption behavior of Na2ZrO3: Structural, microstructural and kinetic variations produced as a function of temperature  

NASA Astrophysics Data System (ADS)

A structural, microstructural and kinetic analysis of the Na2ZrO3-CO2 system was performed over 20 chemisorption-desorption cycles. Different cyclic experiments were performed between 500 and 800 °C. Although the best results were obtained in Na2ZrO3 sample treated at 550 °C, all the samples treated between 500 and 700 °C presented good CO2 chemisorption efficiencies and stabilities. On the contrary, Na2ZrO3 sample treated at 800 °C presented a continuous decrement of the CO2 chemisorption. After 20 cycles all the samples presented a partial Na2ZrO3 decomposition, determined by the ZrO2 formation, which was associated to sodium sublimation. Additionally, the Na2ZrO3 microstructural analysis showed a systematic morphological evolution. It was microscopically observed that Na2ZrO3 particles tend to fracture due to the Na2CO3 formation. Later, after several cycles these tiny fractured particles sinter producing new polyhedral and dense Na2ZrO3-ZrO2 particles. Finally, an exhaustive kinetic analysis showed a high CO2 chemisorption-desorption stability at different temperatures.

Martínez-dlCruz, Lorena; Pfeiffer, Heriberto

2013-08-01

82

Kinetic Monte Carlo simulation scheme for studying desorption processes  

Microsoft Academic Search

We introduce a discrete event kinetic Monte Carlo (KMC) simulation program that is capable of reproducing thermal desorption data. The KMC program is suitable for the analysis of both, desorption in 2D quasi-equilibrium and desorption influenced by kinetic effects. Whereas the KMC simulation exhibits a clear advantage over approaches using rate equations regarding kinetic influences, the well-known quasi-equilibrium desorption provides

B. Lehner; M. Hohage; P. Zeppenfeld

2000-01-01

83

Atomic oxygen diffusion on and desorption from amorphous silicate surfaces.  

PubMed

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

He, Jiao; Jing, Dapeng; Vidali, Gianfranco

2014-02-28

84

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

PubMed

In this (Paper II) and the preceding companion paper (Paper I; R. May, R. Smith, and B. Kay, J. Chem. Phys. 138, 104501 (2013)), we investigate the mechanisms for the release of trapped gases from underneath amorphous solid water (ASW) films. In Paper I, we focused on the low coverage regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime, the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that these abrupt desorption bursts are due to pressure induced structural failure of the ASW overlayer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores formed during ASW deposition. The extent of desorption and the line shape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of ASW is used to vary the porosity of the overlayer and strongly supports the hypothesis that the low temperature desorption pathway is due to porosity that is templated into the ASW overlayer by the underlayer during deposition. PMID:23514504

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

2013-03-14

85

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

86

Measurement of Organic Matter on Si Wafer by Thermal Desorption Spectroscopy  

NASA Astrophysics Data System (ADS)

Organic matter on a Si surface was investigated using thermal desorption spectroscopy (TDS). It was clarified that acetone, ethanol and toluene contaminants on a bare Si surface can be detected by the TDS system, ESCO EMD-WA1000K, and these organic contaminants have different desorption temperatures and fragment patterns. Therefore organic contaminants on Si wafers were thought to be separated by desorption temperature, and characterized from the fragment pattern at that desorption temperature. Here, the desorption temperature is thought to be proportional to the activation energy for desorption. Thus bonding strength between organic contaminants and the Si surface is qualitatively estimated from the desorption temperature.

Okada, Chizuko; Takahashi, Isao; Kobayashi, Hiroyuki; Ryuta, Jiro; Shingyouji, Takayuki

1993-09-01

87

Measurement of organic matter on Si wafer by thermal desorption spectroscopy  

NASA Astrophysics Data System (ADS)

Organic matter on a Si surface was investigated using thermal desorption spectroscopy (TDS). It was clarified that acetone, ethanol, and toluene contaminants on a bare Si surface can be detected by the TDS system, ESCO EMD-WA1000 K, and these organic contaminants have different desorption temperatures and fragment patterns. Therefore organic contaminants on Si wafers were thought to be separated by desorption temperature, and characterized from the fragment pattern at that desorption temperature. Here, the desorption temperature is thought to be proportional to the activation energy for desorption. Thus bonding strength between organic contaminants and the Si surface is qualitatively estimated from the desorption temperature.

Okada, Chizuko; Takahashi, Isao; Kobayashi, Hiroyuki; Ryuta, Jiro; Shingyouji, Takayuki

1993-09-01

88

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

PubMed

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

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

2014-06-28

89

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...

90

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...

91

Thermal Desorption Treatment.  

National Technical Information Service (NTIS)

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

D. Oberacker P. Lafornara P. dePercin

1991-01-01

92

Oxygen-sorptive and -desorptive properties of perovskite-related oxides under temperature-swing conditions for oxygen enrichment  

Microsoft Academic Search

A group of A- and\\/or B-site partially substituted strontium cobaltites was investigated for oxygen-sorptive properties under temperature-swing conditions in air. The cobaltites with perovskite structure desorbed and absorbed significant amounts of oxygen quickly as well as reversibly on heating or cooling in the temperature range between 300 and 1000 °C, while those with brownmillerite or 2H-BaNiO3 structure either lacked oxygen-sorptive

Hajime Kusaba; Go Sakai; Kengo Shimanoe; Norio Miura; Noboru Yamazoe

2002-01-01

93

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

SciTech Connect

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

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

2005-09-01

94

Adsorption, desorption, and diffusion of nitrogen in a model nanoporous material. I. Surface limited desorption kinetics in amorphous solid water.  

PubMed

The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programed desorption (TPD), and reflection-absorption infrared spectroscopy. 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 indicating 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, approximately 0.5 microm). 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. PMID:18020658

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

2007-11-14

95

EQLBRM: A Computer Program to Calculate High Temperature Chemical Equilibrium.  

National Technical Information Service (NTIS)

The report describes a program written to calculate the equilibrium composition of high temperature chemical systems. The program is generally applicable to systems for which the appropriate thermodynamic data is available. The method of calculation is ou...

A. D. Cross

1977-01-01

96

Pillared smectite modified with carbon and manganese as catalyst for SCR of NO x with NH 3 . Part II. Temperature?programmed studies  

Microsoft Academic Search

Temperature?programmed desorption (TPD) and surface reaction (TPSR), and additionally FTIR spectroscopy of adsorbed NO molecules\\u000a were used to characterise surface sites on pillared smectites modified with carbon and manganese. Much higher adsorption of\\u000a NH3 than NO was found, but acidic pre?treatment increased NO sorption to comparable values as well as catalytic performance in\\u000a SCR of NOx. In this case formation

L. Chmielarz; R. Dziembaj; T. Grzybek; J. Klinik; T. ?ojewski; D. Olszewska; A. W?grzyn

2000-01-01

97

Delay Cartridge with Temperature Programmed Flash Chamber.  

National Technical Information Service (NTIS)

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

M. L. Greene F. J. Valenta

1981-01-01

98

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

SciTech Connect

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

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

2010-12-21

99

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

SciTech Connect

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

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

2011-12-31

100

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

101

STP Temperature Measurement Einstein Solid Program  

NSDL National Science Digital Library

The STP DemonEinsteinSolid program displays a histogram of the energy of a demon that exchanges energy with an ideal gas of particles. The purpose of this simulation is to understand how the demon acts as an ideal thermometer. The default system is an Einstein solid of N=40 particles. Additional states and parameters can be specified using the Display|Switch GUI menu item. STP DemonEinsteinSolid is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_DemonEinsteinSolid.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-05-28

102

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

103

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

PubMed

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

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

2013-05-01

104

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

SciTech Connect

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

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

2006-12-21

105

Photon Stimulated Desorption  

NASA Astrophysics Data System (ADS)

The combination of the X-ray standing wave (XSW) technique and photon stimulated desorption (PSD) offers the possibility to investigate both the atomic structure as well as the mechanisms leading to the X-ray induced desorption of ions from the sample surface. Here, we present a review of surface systems studied by the XSW-PSD technique along with a brief description of the basic differences in XSW data evaluation when desorbing ions are used as secondary signal. We show how direct and indirect desorption processes can be identified and that even site-specific desorption cross-sections may be determined with this method.

Flege, Jan Ingo; Schmidt, Thomas; Falta, Jens; Hille, Alexander; Materlik, Gerhard

2013-01-01

106

Temperature programmed reduction of silica supported nickel catalysts  

Microsoft Academic Search

Nickel oxide promoted catalysts are prepared by simple precipitation, precipitation from homogeneous solution and impregnation methods and their reduction behavior is monitored with temperature programmed reduction (TPR) technique. The effect of different parameters such as metal loading, method of preparation and heat treatment temperature are also observed on the reducibility of the catalysts. It is observed that reduction temperature increases

M. Afzall; C. R. Theocharis; S. Karim

1993-01-01

107

Diurnal Soil Temperature Effects within the GLOBE® Program Dataset  

Microsoft Academic Search

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

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

2007-01-01

108

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

109

Detection of volatile organic compounds in breath using thermal desorption electrospray ionization-ion mobility-mass spectrometry.  

PubMed

A thermal desorption unit has been interfaced to an electrospray ionization-ion mobility-time-of-flight mass spectrometer. The interface was evaluated using a mixture of six model volatile organic compounds which showed detection limits of <1 ng sample loaded onto a thermal desorption tube packed with Tenax, equivalent to sampled concentrations of 4 microg L(-1). Thermal desorption profiles were observed for all of the compounds, and ion mobility-mass spectrometry separations were used to resolve the probe compound responses from each other. The combination of temperature programmed thermal desorption and ion mobility improved the response of selected species against background ions. Analysis of breath samples resulted in the identification of breath metabolites, based on ion mobility and accurate mass measurement using siloxane peaks identified during the analysis as internal lockmasses. PMID:20143891

Reynolds, J C; Blackburn, G J; Guallar-Hoyas, C; Moll, V H; Bocos-Bintintan, V; Kaur-Atwal, G; Howdle, M D; Harry, E L; Brown, L J; Creaser, C S; Thomas, C L P

2010-03-01

110

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...

111

High temperature static strain gage program  

NASA Technical Reports Server (NTRS)

Development of electrical resistance strain gages for static strain measurements of nickel or cobalt superalloy parts inside a gas turbine engine on a test stand was inititated. Measurements of this type are of great importance because without reliable knowledge of the stresses and strains which exist in specific components, it will be difficult to fully appreciate where improvements in design and materials can be implemented. The first part of this effort consists of a strain gage alloy development program which will be followed by an investigation of complete strain gage systems. Efforts to date are summarized.

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

1984-01-01

112

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

113

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

We describe an operating mode of a gas sensor that greatly enhances the capability of the device to determine the composition of a sensed gas. The device consists of a micromachined hotplate with integrated heater, heat distribution plate, electrical contact pads, and sensing film. The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for

R. E. Cavicchi; J. S. Suehle; K. G. Kreider; M. Gaitan; P. Chaparala

1995-01-01

114

FINAL REPORT. HIGH TEMPERATURE CONDENSED PHASE MASS SPECTROMETRIC ANALYSIS PROGRAM  

EPA Science Inventory

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

115

Desorption rates and sticking coefficients for CO and N2 interstellar ices  

NASA Astrophysics Data System (ADS)

We present Temperature Programmed Desorption (TPD) experiments of CO and N2 ices in pure, layered and mixed morphologies at various ice "thicknesses" and abundance ratios as well as simultaneously taken Reflection Absorption Infrared Spectra (RAIRS) of CO. A kinetic model has been developed to constrain the binding energies of CO and N2 in both pure and mixed environments and to derive the kinetics for desorption, mixing and segregation. For mixed ices N2 desorption occurs in a single step whereas for layered ices it proceeds in two steps, one corresponding to N2 desorption from a pure N2 ice environment and one corresponding to desorption from a mixed ice environment. The latter is dominant for astrophysically relevant ice "thicknesses". The ratio of the binding energies, R_BE, for pure N2 and CO is found to be 0.936 ± 0.03, and to be close to 1 for mixed ice fractions. The model is applied to astrophysically relevant conditions for cold pre-stellar cores and for protostars which start to heat their surroundings. The importance of treating CO desorption with zeroth rather than first order kinetics is shown. The experiments also provide lower limits of 0.87 ± 0.05 for the sticking probabilities of CO-CO, N2-CO and N2-N2 ices at 14 K. The combined results from the desorption experiments, the kinetic model, and the sticking probability data lead to the conclusion that these solid-state processes of CO and N2 are very similar under astrophysically relevant conditions. This conclusion affects the explanations for the observed anti-correlations of gaseous CO and N2H+ in pre-stellar and protostellar cores.

Bisschop, S. E.; Fraser, H. J.; Öberg, K. I.; van Dishoeck, E. F.; Schlemmer, S.

2006-04-01

116

Adsorption and Desorption Kinetics of Organosilanes at Si(001) Surfaces  

NASA Astrophysics Data System (ADS)

Adsorption and desorption kinetics of organosilanes [dimethylsilane (DMS) and monomethylsilane (MMS)] at Si(001) surfaces have been investigated by using temperature-programmed desorption (TPD), and compared with those of acetylene (C2H2)- and atomic hydrogen (H)-adsorbed Si surfaces. TPD spectra from DMS/Si(001) present ?1 (˜510°C), ?1' (˜550°C), ? (˜615°C) and ? (˜910°C) peaks while MMS/Si(001) shows only ?1 (˜510°C) and ? (˜870°C) peaks. C2H2/Si(001) presents ?1 (˜510°C) and ? (˜615°C) peaks as well but showed no ?1' and ? peaks. The ?1' peak, observed for DMS, is currently understood to be due to hydrogen desorption from the Si-H at a Si-C hetero-dimer. Unlike MMS, the appearance of the bulk-carbon related ? peak from the initial DMS adsorption suggests enhanced C incorporation with the use of DMS. The analysis of the hydrogen uptake curve also implies that DMS and MMS have different adsorption kinetics.

Senthil, Karuppanan; Nakazawa, Hideki; Suemitsu, Maki

2003-11-01

117

Characterisation of CuMFI catalysts by temperature programmed desorption of NO and temperature programmed reduction. Effect of the zeolite Si\\/Al ratio and copper loading  

Microsoft Academic Search

Copper MFI zeolites with different Si\\/Al ratios and different copper loadings, prepared by ion exchange, were characterised by XRD, H2-TPR and NO TPD. The results indicated the existence of diverse copper species in CuMFI catalysts, such as isolated CU2+, Cu+ ions and CuO species, whose concentrations depends on the catalyst Si\\/Al ratio and copper loading. In underexchanged catalysts (catalysts with

C. Torre-Abreu; M. F. Ribeiro; C. Henriques; G. Delahay

1997-01-01

118

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

119

The adsorption of H 2 and D 2 on Fe(110) . II. Angle resolved thermal desorption spectroscopy and kinetic mechanism  

NASA Astrophysics Data System (ADS)

Results of angle resolved thermal desorption spectroscopy (ARTDS) measurements for the adsorption of D 2 and H 2 on Fe(110) are presented. A detailed model of the interaction process has been developed using these results in combination with results obtained using thermal energy atom scattering (TEAS), reported in part I of this work, ARTDS was used to measure the desorption flux as a function of surface polar angle during temperature programming following adsorption at a low temperature. Second order desorption kinetics, as observed with TEAS in part I, were confirmed. H 2 and D 2 were found to adsorb directly, dissociatively and with an activation energy for adsorption of 700 cal/mol. The sticking coefficient was observed to decrease with increasing coverage as (1- ?) 2 for ? greater than 0.1.

Kurz, Edward A.; Hudson, John B.

120

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

121

The New England High-Resolution Temperature Program.  

NASA Astrophysics Data System (ADS)

The New England High-Resolution Temperature Program seeks to improve the accuracy of summertime 2-m temperature and dewpoint temperature forecasts in the New England region through a collaborative effort between the research and operational components of the National Oceanic and Atmospheric Administration (NOAA). The four main components of this program are 1) improved surface and boundary layer observations for model initialization, 2) special observations for the assessment and improvement of model physical process parameterization schemes, 3) using model forecast ensemble data to improve upon the operational forecasts for near-surface variables, and 4) transfering knowledge gained to commercial weather services and end users. Since 2002 this program has enhanced surface temperature observations by adding 70 new automated Cooperative Observer Program (COOP) sites, identified and collected data from over 1000 non-NOAA mesonet sites, and deployed boundary layer profilers and other special instrumentation throughout the New England region to better observe the surface energy budget. Comparisons of these special datasets with numerical model forecasts indicate that near-surface temperature errors are strongly correlated to errors in the model-predicted radiation fields. The attenuation of solar radiation by aerosols is one potential source of the model radiation bias. However, even with these model errors, results from bias-corrected ensemble forecasts are more accurate than the operational model output statistics (MOS) forecasts for 2-m temperature and dewpoint temperature, while also providing reliable forecast probabilities. Discussions with commerical weather vendors and end users have emphasized the potential economic value of these probabilistic ensemble-generated forecasts.

Stensrud, David J.; Yussouf, Nusrat; Baldwin, Michael E.; McQueen, Jeffery T.; Du, Jun; Zhou, Binbin; Ferrier, Brad; Manikin, Geoffrey; Ralph, F. Martin; Wilczak, James M.; White, Allen B.; Djlalova, Irina; Bao, Jian-Wen; Zamora, Robert J.; Benjamin, Stanley G.; Miller, Patricia A.; Smith, Tracy Lorraine; Smirnova, Tanya; Barth, Michael F.

2006-04-01

122

Characterization of nickel loaded mordenite catalysts by temperature programmed reduction  

Microsoft Academic Search

Temperature programmed reduction (TPR) has been used to study the redox behavior of Ni(II) ions in nickel sodium mordenite (NiNaM) and decationated nickel mordenite (NiHM). The TPR profiles suggest that Ni(II) ions occupy nonequivalent sites with different cooridination states in the mordenite. The reducibility of Ni(II) depends strongly on the zeolite acidity.

Z. Popova; R. Dimitrova; Chr Dimitrova; G. Wendt

1989-01-01

123

High-Pressure Temperature-Programmed Reduction of Sulfided Catalysts  

Microsoft Academic Search

Temperature-programmed reduction (TPR) of solids materials is a widely used technique of characterization in heterogeneous catalysis. So far all studies dealing with this technique have been carried out at ambient or subambient pressure. Because most catalytic processes are performed at higher hydrogen pressures, the impact of this technique could be enhanced by the development of a new generation of equipment

Franck Labruyère; Michel Lacroix; Daniel Schweich; Michèle Breysse

1997-01-01

124

Cerium dioxide crystallite sizes by temperature-programmed reduction  

Microsoft Academic Search

Yao and Yao recently reported that the temperature-programmed reduction (TPR) traces of unsupported ceria show two peaks, which are associated with surface capping oxide ions and bulk ions, respectively. The work reported here has confirmed their qualitative relationship between the magnitude of the capping oxide peak and BET surface areas of the ceria specimens. Furthermore, the observed quantity of hydrogen

M. F. L. Johnson; J. Mooi

1987-01-01

125

Temperature programmed reduction studies of nonpyrophoric Raney nickel catalysts  

Microsoft Academic Search

Temperature programmed reduction studies have revealed that the surface of nonpyrophoric Raney nickel catalysts is covered by readily reduceable nonstoichiometric metaloxygen structures. A method is suggested to calculate kinetic reaction parameters on the basis of analyzing the shape of one of the TPR curves.

A. B. Fasman; S. D. Mikhailenko; E. V. Leongard; T. A. Khodareva; A. I. Lyashenko

1989-01-01

126

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

127

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...

128

Supercritical fluid extraction and temperature-programmed desorption of phenol and its oxidative coupling products from activated carbon  

Microsoft Academic Search

Activated carbon remains one of the most economical adsorbents for the removal of contaminants from water. In particular, activated carbon is known to have an extremely high affinity for phenol and its derivatives. This has been shown to be the result of a catalytic process wherein activated carbon catalyzes the oxidative coupling reactions of phenol in aqueous solution when molecular

Raashina Humayun; Gurkan Karakas; Philip R. Dahlstrom; Umit S. Ozkan; David L. Tomasko

1998-01-01

129

Temperature-Programmed Reduction Studies of V-Ag Catalysts  

Microsoft Academic Search

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

Xin Ge; Hui-liang Zhang

1998-01-01

130

Temperature-programmed reduction of Ni-Mo oxides  

Microsoft Academic Search

Temperature-programmed reduction (TPR) has been employed to study Ni-Mo mixed oxides which were previously used as model hydrodesulphurization (HDS) catalysts, using compositions ranging from pure MoO3 to pure NiO. An assignment of TPR signals to the different bulk phases was attempted. Good agreement between TPR spectra and structural data obtained previously from X-ray and electron diffraction was observed. TPR traces

Joaquín L. Brito; Jorge Laine; Kerry C. Pratt

1989-01-01

131

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

PubMed

In order to develop a new method to study the mobility and bioavailability of organic contaminants in soils, a set of thermal desorption device was established. Water desorption and thermal desorption of toluene and pyrene in three types of soils were investigated. The two desorption occurred as bi-phase, which indicates that the combination states of the aromatic hydrocarbons in soils are different. The desorption was described by the first-order two compartment model and an exponential decay equation. Parameters, such as fast desorption fraction F(rap), water and thermal desorption rate constants, b(w) and b(t) were derived. For toluene, values of F(rap) in three soils were 27.9%, 12.5%, 16.0%, respectively, and 2.4%, 22.0%, and 19.1% for pyrene. Values of b(w) were 0.241, 0.018, 0.038 for toluene and 0.008, 0.013, 0.012 for pyrene. There is a significantly positive correlation relationship between F (rap) and b(w) (toluene: R2 = 0.982; pyrene: R2 = 0.991). At 250 degrees C, values of b(t) in three soils were 0.167, 0.064, 0.141 for toluene, and 0.036, 0.062, 0.047 for pyrene. At 400 degrees C, the corresponding values were 0.429, 0.084, 0.398 for toluene and 0.066, 0.162, 0.153 for pyrene. Meanwhile, the water b(w) shows a good correlation with b(t) at selected temperatures (250 degrees C: R2 = 0.985; 400 degrees C: R2 = 0.848). Moreover, F(rap) is positively correlated with b(t). As F(rap) has been used to predict bioavailability, thermal desorption can therefore be used to predict bioavailability. PMID:20329538

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

2010-01-01

132

REMOVAL OF CREOSOTE FROM SOIL BY THERMAL DESORPTION  

EPA Science Inventory

Performance of the thermal desorption process for removal of organic contaminants, mostly polynuclear aromatic hydrocarbons (PAHs), from soils was evaluated. uperfund Site Soil that was contaminated with creosote was tested. An operating temperature of 550 degrees C and an operat...

133

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

NASA Astrophysics Data System (ADS)

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

Becker, Kelly E.; Fichthorn, Kristen A.

2006-11-01

134

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

PubMed

We utilize accelerated molecular dynamics to simulate alkane desorption from the basal plane of graphite. Eight different molecules, ranging from n-pentane to n-hexadecane, are studied in the low coverage limit. Acceleration of the molecular dynamics simulations is achieved using two different methods: temperature acceleration and a compensating potential scheme. We find that the activation energy for desorption increases with increasing chain length. The desorption prefactor increases with chain length for molecules ranging from pentane to decane. This increase subsides and the value of the preexponential factor fluctuates about an apparently constant value for decane, dodecane, tetradecane, and hexadecane. These trends are consistent with data obtained in experimental temperature-programed desorption (TPD) studies. We explain the dependence of the preexponential factor on alkane chain length by examining conformational changes within the alkane molecules. For the shorter molecules, torsional motion is not activated over experimental temperature ranges. These molecules can be treated as rigid rods and their partial loss in translational and rotational entropies upon adsorption increases as chain length increases, leading to an increasing preexponential factor. At their typical TPD peak temperatures, torsions are activated in the longer adsorbed chain molecules to a significant extent which increases with increasing chain length, increasing the entropy of the adsorbed molecule. This increase counteracts the decrease in entropy due to a loss of translation and rotation, leading to a virtually constant prefactor. PMID:17115778

Becker, Kelly E; Fichthorn, Kristen A

2006-11-14

135

Desorption from interstellar grains  

NASA Technical Reports Server (NTRS)

Different desorption mechanisms from interstellar grains are considered to resolve the conflict between the observed presence of gaseous species in molecular clouds and their expected depletion onto grains. The physics of desorption is discussed with particular reference to the process of grain heating and the specific heat of the dust material. Impulsive heating by X-rays and cosmic rays is addressed. Spot heating of the grains by cosmic rays and how this can lead to desorption of mantles from very large grains is considered. It is concluded that CO depletion on grains will be small in regions with A(V) less than five from the cloud surface and n(H) less than 10,000, in agreement with observations and in contrast to expectations from pure thermal equilibrium. Even in very dense and obscured regions and in the absence of internal ultraviolet sources, the classical evaporation of CO or N2 and O2-rich mantles by cosmic rays is important.

Leger, A.; Jura, M.; Omont, A.

1985-01-01

136

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

PubMed

Long-term adsorption of phenanthrene to soils was characterized in a silt-loam (LHS), a sandy soil (SBS), and a podzolized soil (CNS) by use of the Polanyi-Manes model, a Langmuir-type model, and a black carbon-water distribution coefficient (K(BC)) at a relative aqueous concentration (C(e)/S(w)) of 0.002-0.32. Aqueous desorption kinetic tests and temperature-programmed desorption (TPD) were also used to evaluate phenanthrene diffusivities and desorption activation energies. Adsorption contribution in soils was 48-70% after 30 days and 64-95% after 270 days. Significant increases in adsorption capacity with aging suggest that accessibility of phenanthrene to fractions of SBS soil matrix was controlled by sorptive diffusion at narrow meso- and micropore constrictions. Similar trends were not significant for LHS silt-loam or CNS podzol. Analysis of TPD profiles reveal desorption activation energies of 35-53 kJ/mol and diffusivities of 1.6 x 10(-7-)9.7 x 10(-8) cm2/s. TPD tests also indicate that the fraction of phenanthrene mass not diffusing from soils was located within micropores and narrow width mesopores with a corresponding volume of 1.83 x 10(-5-)6.37 x 10(-5) cm3/g. These values were consistent with the modeled adsorption contributions, thus demonstrating the need for such complimentary analytical approach in the risk assessment of organic contaminants. PMID:16999118

Abu, Abdul; Smith, Steve

2006-09-01

137

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

138

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

139

Temperature programmed reduction studies of nickel manganite spinels  

Microsoft Academic Search

Temperature programmed reduction (TPR) of manganese, nickel monometallic oxides (Mn3O4, Mn2O3, MnO2 and NiO) and nickel manganite oxides (spinels NixMn3?xO4 with 0 < x ? 1 and ilmenite NiMnO3), under hydrogen, was investigated. Final and transient products produced were characterised by XRD.Manganese oxides are successively reduced to less oxidised oxide (MnO2 gives Mn2O3 which gives Mn3O4 which further gives MnO).

Laberty Christel; Alphonse Pierre; Duprat Anne-Marie Rousset Abel

1997-01-01

140

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

141

n-Alkanes on MgO(100). II. Chain Length Dependence of Kinetic Desorption Parameters for Small n-Alkanes  

SciTech Connect

Coverage-dependent desorption kinetics parameters are obtained from high quality temperature programmed desorption (TPD) 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 0.3 to 10.0 K/s. The inversion analysis method with its least-squares 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 pre-exponential factor for desorption increases dramatically with chain length from 1013.1 to 1019.1 s-1 over the range 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 gas-like transition state for desorption. The desorption energy increases with chain length as Ed(N) = 6.5 + 7.1 N, which implies an incremental increase of 7.1?0.2 kJ/mol per CH2.

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

2005-04-22

142

Adsorption of H/sub 2/ and D/sub 2/ on Fe(110). 2. Angle resolved thermal-desorption spectroscopy and kinetic mechanism. Interim technical report  

SciTech Connect

Results of angle-resolved thermal desorption spectroscopy (ARTD) measurements for the adsorption of deuterium and hydrogen on iron are presented. A detailed model of the interaction process was developed using these results in combination with results obtained using thermal energy atom scattering (TEAS), reported in Part I of this work. Angle-Resolved-Thermal-Spectroscopy was used to measure the desorption flux as a function of surface polar angle during temperature programming following adsorption at a low temperature. Second-order desorption kinetics, as observed with TEAS in part I, were confirmed. H/sub 2/ and D/sub 2/ were found to adsorb directly, dissociatively, and with an activation energy of 700 cal/mole. The sticking coefficient was observed to decrease with increasing coverage.

Kurz, E.A.; Hudson, J.B.

1987-07-30

143

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

144

Thermal desorption of metals from tungsten single crystal surfaces  

NASA Technical Reports Server (NTRS)

After a short review of experimental methods used to determine desorption energies and frequencies the assumptions underlying the theoretical analysis of experimental data are discussed. Recent experimental results on the flash desorption of Cu, Ag, and Au from clean, well characterized W (110) and (100) surfaces are presented and analyzed in detail with respect to the coverage dependence. The results obtained clearly reveal the limitations of previous analytical methods and of the experimental technique per se (such as structure and phase changes below and in the temperature region in which desorption occurs).

Bauer, E.; Bonczek, F.; Poppa, H.; Todd, G.

1975-01-01

145

Calcium lignosulfonate adsorption and desorption on Berea sandstone.  

PubMed

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

Grigg, Reid B; Bai, Baojun

2004-11-01

146

Hydrogen absorption and desorption in rapidly solidified Mg Al alloys  

Microsoft Academic Search

The addition of Al to Mg has been indicated as a suitable way to destabilise the hydride phase, in order to bring the absorption and desorption reactions close to reasonable temperatures and pressure values for hydrogen storage. Rapid solidification is known to refine the microstructure of Mg-Al alloys and it might improve the H2 absorption\\/desorption kinetics. In this paper, the

J. Urgnani; M. Di Chio; M. Palumbo; M. Feuerbacher; J. F. Fernandez; F. Leardini; M. Baricco

2009-01-01

147

Removal of NO x : Part I. Sorption\\/desorption processes on barium aluminate  

Microsoft Academic Search

NOx adsorption\\/desorption capacities of barium aluminates were measured under representative exhaust gas mixture at temperatures below 550°C. The solid doped with Pt or not, exhibits good NO2 sorption capacities with a reversible adsorption to desorption process. With bulk BaO, desorption was observed at high temperature. The different behaviour between the two catalysts is explained by the fact that strongly bonded

S Hodjati; P Bernhardt; C Petit; V Pitchon; A Kiennemann

1998-01-01

148

Determination of residual solvents in pharmaceuticals by thermal desorption-GC/MS.  

PubMed

A novel method for the determination of residual solvents in pharmaceuticals by thermal desorption (TD)-GC/MS has been established. A programmed temperature pyrolyzer (double shot pyrolyzer) is applied for the TD. This method does not require any sample pretreatment and allows very small amounts of the sample. Directly desorbed solvents from intact pharmaceuticals (ca. 1 mg) in the desorption cup (5 mm x 3.8 mm i.d.) were cryofocused at the head of a capillary column prior to a GC/MS analysis. The desorption temperature was set at a point about 20 degrees C higher than the melting point of each sample individually, and held for 3 min. The analytical results using 7 different pharmaceuticals were in agreement with those obtained by direct injection (DI) of the solution, followed by USP XXIII. This proposed TD-GC/MS method was demonstrated to be very useful for the identification and quantification of residual solvents. Furthermore, this method was simple, allowed rapid analysis and gave good repeatability. PMID:11708147

Hashimoto, K; Urakami, K; Fujiwara, Y; Terada, S; Watanabe, C

2001-05-01

149

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

PubMed

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

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

2014-05-29

150

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

PubMed

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

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

2012-11-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

152

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

Microsoft Academic Search

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

M. J. Murphy; A. Hodgson

1998-01-01

153

Electron-Stimulated Desorption from Aluminum Surfaces  

NASA Astrophysics Data System (ADS)

Electron-stimulated desorption (ESD) of ions and neutrals from methanol-degreased aluminum-6063 alloy and from methanol-dosed Al(111) are studied by time-of-flight (TOF) mass spectrometry. From both systems, protons are the major component observed in the ion channel, and these are determined to desorb with kinetic energies in the several eV range. Laser ionization at 193 nm is used to detect the desorbed neutrals, and velocity distributions of the photofragmented neutrals are performed. Based on photofragmentation patterns, the parent desorbate, at room temperature, is assigned as the methoxy species. Velocity (energy) distributions from the methanol-degreased alloy and the methanol-dosed Al(111) peak at 250 m/s (0.01 eV) and 900 m/s (0.13 eV), respectively. Estimates are made of the ionic and neutral desorption yields, and the greater than order of magnitude difference in kinetic energies between the desorbed ions and neutrals is discussed in terms of possible desorption mechanisms. In addition to methoxy desorption from the methanol -dosed Al(111) system, a heretofore unexpected neutral ESD channel has been detected. lsotopic substitution studies and resonant laser ionization unequivocally demonstrate that a neutral aluminum-containing species is desorbed upon electron impact. Velocity distributions of this aluminum species are measured, and its yield is determined by direct comparison to sputtered Al signal. Neutral ESD, combined with x-ray photoelectron spectroscopy (XPS) is also used as a probe of changes in surface adsorbate composition as a function of temperature and of electron beam dose for the methanol/Al(111) system, and it is shown that neutral ESD can be used as a complementary technique to standard surface science techniques.

Whitten, James Edward

154

Studies of organic residues from ancient Egyptian mummies using high temperature-gas chromatography-mass spectrometry and sequential thermal desorption-gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry.  

PubMed

The techniques of gas chromatography-mass spectrometry (GC-MS) and sequential thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) have been utilised to characterise the constituents of tissue-derived or applied organic material from two Pharaonic Egyptian mummies with a view to identifying embalming practices/substances. The results obtained using TD-GC-MS revealed a series of monocarboxylic acids with the C16:0, C18:1 and C18:0 components dominating in both mummies. The thermal desorption products related to cholesterol, i.e., cholesta-3,5,7-triene and cholesta-3,5-diene (only in Khnum Nakht), were detected in both mummies. Khnum Nakht also contained a number of straight chain alkyl amides (C16-C18) and an alkyl nitrile (C18). Other products included the 2,5-diketopiperazine derivative (DKP) of proline-glycine (pro-gly) which was a major component (7.9%) in Khnum Nakht but only a very minor component in Horemkenesi. Py-GC-MS of samples of both specimens yielded a series of alkene/alkane doublets (Horemkenesi C6-C18, Khnum Nakht C6-C24) which dominated their chromatograms. Series of methyl ketones in the C9-C19 chain length range were also present, with C5-C7 cyclic ketones occurring in Horemkenesi only. These ketones are indicative of covalent bond cleavage, probably of polymerised acyl lipids. Nitrogenous products included nitriles (C9-C18) which were significant in both samples, and amides which were only detected in Khnum Nakht. Also present amongst the pyrolysis products were three steroidal hydrocarbons, cholest-(?)-ene, cholesta-3,5,7-triene and cholesta-3,5-diene. High temperature-GC-MS of trimethylsilylated lipid extracts yielded similar monocarboxylic acids to that obtained using TD-GC-MS, while a series of alpha, omega-dicarboxylic acids and a number of mono- and di-hydroxy carboxylic acids not seen in the thermal desorption or pyrolysis GC-MS analyses were significant constituents in both mummy samples. Overall, the use of GC-MS and sequential TD-GC-MS and Py-GC-MS has demonstrated in both mummies the presence of a complex suite of lipids and proteinaceous components whose compositions indicates extensive alteration via oxidative and hydrolytic processes during long-term interment. None of the classical embalming resins was detected but an exogenous origin for at least a proportion of these components cannot be discounted since fats, oils and gelatin have been proposed as embalming agents in mummification. The combined approach of sequential TD- and Py-GC-MS has potential for application to the characterisation of embalming materials in mummies. Most importantly these techniques virtually eliminate any destruction of the mummified bodies thereby allowing the scope of investigations of ancient Egyptian funerary practices to be significantly extended. PMID:10605875

Buckley, S A; Stott, A W; Evershed, R P

1999-04-01

155

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

USGS Publications Warehouse

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

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

2002-01-01

156

Thermal Desorption: A Technology Review.  

National Technical Information Service (NTIS)

New and innovative technologies have been developed to treat hazardous wastes because of the high costs of remediation. One such technology is thermal desorption, which heats soils, sediments, and sludges to volatilize any contaminants present. Thermal de...

T. P. Sullivan

1997-01-01

157

Thermal Desorption Treatment (February 1994).  

National Technical Information Service (NTIS)

The bulletin discusses various aspects of the thermal desorption technology including applicability, limitations of its use, residuals produced, performance data, site requirements, status of the technology, and sources of further information. The documen...

J. Rawe E. Saylor

1994-01-01

158

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

PubMed

Recently, the lean NOx trap technology using supported Pt catalyst on alumina was devised to store NOx under lean condition and to reduce into N2 and water under rich condition in lean burn engine. In this work, the effect of the Pt nanoparticle supported on hierarchical macro-meso-microporous BaO-Al2O3 on NO2 desorption has been investigated with NO2 temperature programmed desorption, TEM, SEM, TGA and hydrogen chemisorption. Crystalline BaO phase of 20-30 nm thickness were obtained on the hierarchical macro-meso-microporous Al2O3 with a simple impregnation of Ba(NO3)2 and Ba(ClO4)2. The interaction of Pt and BaO was resulted in the formation of atomically dispersed Pt nanoparticles and also decreased the desorption temperature of NO2 adsorbed on BaO at much lower temperature than that from the BaO-Al2O3 support only. This synergistic lowering of NO2 desorption temperature may be originated from the interaction between Pt and BaO. PMID:22103194

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

2011-08-01

159

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

160

Determination of non-stoichiometric oxygen in NiO by temperature-programmed reduction  

Microsoft Academic Search

Nickel oxide samples, calcined at various temperatures, have been studied by temperature-programmed reduction to determine quantitatively the amount of non-stoichiometric oxygen both in the surface and in the bulk.

Nikolay K. Kotsev; Luba I. Ilieva

1993-01-01

161

Temperature programmed reduction and oxidation of Ir\\/Al 2 O 3 catalysts  

Microsoft Academic Search

3 % Ir\\/Al2O3 catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher Tox) reducibility of the catalysts at low temperatures decreases.

T. Paryjczak; P. Zieli?ski; W. K. Jó?wiak

1985-01-01

162

Desorption by ultrasound: Phenol on activated carbon and polymeric resin  

SciTech Connect

An experimental feasibility study of using ultrasound to accomplish the difficult desorption of phenol from activated carbon and polymeric resin adsorbents is discussed. The desorption rates of activated carbon were found to significantly increase by ultrasound at 40 kHz and 1.44 MHz. Attrition of the activated carbon due to cavitation could be prevented by operating at a higher frequency and with an intensity below the threshold of the pulverization of carbon. According to the structural stability study of Amberlite XAD-4 and Dowex Optipore L-493 resins to withstand the abrasive cavitational effects of ultrasound at 40 kHz, the Dowex Optipore resin was stable under experimental conditions and phenol desorption rates were enhanced significantly with sonication. The ultrasonic desorption rates were favored by decreased temperature, aerated liquid medium, and increased ultrasound intensity. The desorption rates obtained without ultrasound appeared to be limited by pore diffusion, whereas those obtained without ultrasound appeared to be limited by pore diffusion, whereas those obtained in the presence of ultrasound were limited by surface reaction. The rate enhancement was due to an increase in diffusive transport within the pores caused by acoustic vortex microstreaming. The activation energy for desorption decreased with an increase in ultrasonic power density, thus making the ultrasound weaken the adsorption bond.

Rege, S.U.; Yang, R.T.; Cain, C.A. [Univ. of Michigan, Ann Arbor, MI (United States)] [Univ. of Michigan, Ann Arbor, MI (United States)

1998-07-01

163

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

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

164

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

165

49 NOx sorption-desorption mechanism of ZrO 2-based oxide  

Microsoft Academic Search

NOx sorption-desorption by zirconia-based sorbent, Pt-ZrO2\\/Al2O3 has been investigated. Oxidation of NO to NO2 and to nitrate ions is an important role for Pt. At low temperatures below 200°C, the oxidation activity of Pt is insufficient. As the sorption temperature increased, the amount of NOx desorbing at higher temperatures increased in comparison with the low temperature desorption in TPD. The

Suzue Kikuyama; Izumi Matsukuma; Tatsuya Takeguchi; Ryuji Kikuchi; Koichi Eguchi; Kazunari Sasaki

2003-01-01

166

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

167

Material evaluation program, high-temperature nitriding environment  

NASA Technical Reports Server (NTRS)

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

Marcy, R. D.

1973-01-01

168

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

Microsoft Academic Search

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

J. Villain

1991-01-01

169

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

PubMed Central

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

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

2013-01-01

170

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

171

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

172

A general strategy for performing temperature-programming in high performance liquid chromatography--prediction of segmented temperature gradients.  

PubMed

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed to predict retention times for segmented-temperature gradients based on temperature-gradient input data in liquid chromatography (LC) with high accuracy. The LES model assumes that retention times for isothermal separations can be predicted based on two temperature gradients and is employed to calculate the retention factor of an analyte when changing the start temperature of the temperature gradient. In this study it was investigated whether this approach can also be employed in LC. It was shown that this approximation cannot be transferred to temperature-programmed LC where a temperature range from 60°C up to 180°C is investigated. Major relative errors up to 169.6% were observed for isothermal retention factor predictions. In order to predict retention times for temperature gradients with different start temperatures in LC, another relationship is required to describe the influence of temperature on retention. Therefore, retention times for isothermal separations based on isothermal input runs were predicted using a plot of the natural logarithm of the retention factor vs. the inverse temperature and a plot of the natural logarithm of the retention factor vs. temperature. It could be shown that a plot of lnk vs. T yields more reliable isothermal/isocratic retention time predictions than a plot of lnk vs. 1/T which is usually employed. Hence, in order to predict retention times for temperature-gradients with different start temperatures in LC, two temperature gradient and two isothermal measurements have been employed. In this case, retention times can be predicted with a maximal relative error of 5.5% (average relative error: 2.9%). In comparison, if the start temperature of the simulated temperature gradient is equal to the start temperature of the input data, only two temperature-gradient measurements are required. Under these conditions, retention times can be predicted with a maximal relative error of 4.3% (average relative error: 2.2%). As an example, the systematic method development for an isothermal as well as a temperature gradient separation of selected sulfonamides by means of the adapted LES model is demonstrated using a pure water mobile phase. Both methods are compared and it is shown that the temperature-gradient separation provides some advantages over the isothermal separation in terms of limits of detection and analysis time. PMID:21872258

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

2011-09-28

173

On the interpretation of temperature programmed reduction patterns of transition metals sulphides  

Microsoft Academic Search

Transition metal sulphides show the temperature programmed reduction (TPR) patterns consisting of multiple reduction domains: those at lower temperatures are attributed to the “weakly bonded” sulphur, whereas the “bulk reduction” peaks are usually placed at high temperatures. The present paper is focusing attention on the last type TPR maxima. Due to the positive free energy of reduction of catalytically important

P. Afanasiev

2006-01-01

174

Optimal design of non-linear Temperature Programmed Reduction (TPR) experiments  

Microsoft Academic Search

The experimental method of temperature programmed reduction (TPR) is extended by application of non-constant temperature gradients. An optimal control problem is formulated with the D-optimality criterion as the objective function and ordinary differential equations (ODEs) as constraints. The problem is solved for systems with a single reaction and with two consecutive reactions. The results show that optimal nonlinear temperature profiles

Peter Heidebrecht; Kai Sundmacher; Lorenz T. Biegler

2009-01-01

175

DOPPLER Program for Calculating the Doppler Temperature Reactivity Coefficient.  

National Technical Information Service (NTIS)

An algorithm of calculating the Doppler temperature reactivity coefficient (TRC) for reactors with thermal and intermediate neutron spectra is considered. The method of small perturbation theory is used for the calculation. The Doppler TRC is expressed in...

V. M. Dekusar

1980-01-01

176

High-temperature oxidation and corrosion of materials program  

SciTech Connect

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

Whittle, D.P.

1980-03-01

177

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

178

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

179

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

180

Hydrogen adsorption\\/desorption properties of mechanically milled activated carbon  

Microsoft Academic Search

We investigated the hydrogen adsorption\\/desorption properties of activated carbon that was prepared by mechanical milling in a hydrogen atmosphere at an ambient temperature. Although the hydrogen concentration estimated by inert gas fusion-thermal conductivity method increased with milling time up to 10 h, samples milled for longer than 10 h showed little dependence on milling time. Ultimately, the hydrogen concentration reached

K. Shindo; T. Kondo; M. Arakawa; Y. Sakurai

2003-01-01

181

Thermal desorption study of selected austenitic stainless steels  

Microsoft Academic Search

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

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

2003-01-01

182

Desorption isotherm and heat pump drying kinetics of peas  

Microsoft Academic Search

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

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

1997-01-01

183

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

184

Guide for Conducting Treatability Studies under CERCLA: Thermal Desorption Quick Reference Fact Sheet.  

National Technical Information Service (NTIS)

Systematically conducted, well documented treatability studies are an important component of remedy evaluation and selection under the Superfund program. This fact sheet focuses on thermal desorption remedy selection treatability studies conducted in supp...

J. Rawe

1992-01-01

185

Overview of Thermal Desorption Technology.  

National Technical Information Service (NTIS)

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

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

1998-01-01

186

High Temperature Materials Needs in NASA's Advanced Space Propulsion Programs  

NASA Technical Reports Server (NTRS)

In recent years, NASA has embarked on several new and exciting efforts in the exploration and use of space. The successful accomplishment of many planned missions and projects is dependent upon the development and deployment of previously unproven propulsion systems. Key to many of the propulsion systems is the use of emergent materials systems, particularly high temperature structural composites. A review of the general missions and benefits of utilizing high temperature materials will be presented. The design parameters and operating conditions will be presented for both specific missions/vehicles and classes of components. Key technical challenges and opportunities are identified along with suggested paths for addressing them.

Eckel, Andrew J.; Glass, David E.

2005-01-01

187

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

PubMed

We have investigated the interaction of oxygen with the Ag/Pt(111) surface alloy by thermal desorption spectroscopy (TDS). The surface alloy was formed during the deposition of sub-monolayer amounts of silver on Pt(111) at 800 K and subsequent cooling to 300 K. The low-temperature phase of the surface alloy is composed of nanometer-sized silver rich stripes, embedded within platinum-rich domains, which were characterized with spot profile analysis low energy electron diffraction. The TDS measurements show that oxygen adsorption is blocked on Ag sites: the saturation coverage of oxygen decreases with increasing Ag coverage. Also, the activation energy for desorption (Edes) decreases with Ag coverage. The analysis of the desorption spectra from clean Pt(111) shows a linear decay of Edes with oxygen coverage, which indicates repulsive interactions between the adsorbed oxygen atoms. In contrast, adsorption on alloyed Ag/Pt(111) leads to an attractive interaction between adsorbed oxygen atoms. PMID:24952558

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

2014-06-21

188

Desorption of oxygen from alloyed Ag/Pt(111)  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

189

Particle size, grain size and gamma-MgH2 effects on the desorption properties of nanocrystalline commercial magnesium hydride processed by controlled mechanical milling  

Microsoft Academic Search

The hydrogen desorption properties of commercial nanocrystalline magnesium hydride (Tego Magnan® from Degussa-Goldschmidt) processed by controlled mechanical milling (CMM) are investigated. A profound effect of the powder particle size on the hydrogen desorption characteristics has been observed. The onset (TON) and peak hydrogen desorption temperatures measured by differential scanning calorimetry (DSC) decrease initially slowly with decreasing mean particle size of

R. A. Varin; T. Czujko; Z. Wronski

2006-01-01

190

Particle size, grain size and ?-MgH2 effects on the desorption properties of nanocrystalline commercial magnesium hydride processed by controlled mechanical milling  

Microsoft Academic Search

The hydrogen desorption properties of commercial nanocrystalline magnesium hydride (Tego Magnan® from Degussa–Goldschmidt) processed by controlled mechanical milling (CMM) are investigated. A profound effect of the powder particle size on the hydrogen desorption characteristics has been observed. The onset (TON) and peak hydrogen desorption temperatures measured by differential scanning calorimetry (DSC) decrease initially slowly with decreasing mean particle size of

R A Varin; T Czujko; Z Wronski

2006-01-01

191

Sorption/desorption reversibility of phenanthrene in soils and carbonaceous materials  

SciTech Connect

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

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

2007-02-15

192

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

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

Ferrizz, Robert Matthew

2007-08-01

193

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

194

Temperature-programmed reduction and oxidation of bimetallic Pd?Ni\\/Al 2 O 3 catalysts  

Microsoft Academic Search

Temperature-programmed reduction and oxidation of bimetallic catalysts Pd?Ni\\/Al2O3 seem to indicate phase segregation of palladium and nickel oxides and alloying of palladium and nickel in the process of reduction of oxidized catalysts.

T. Paryjczak; J. M. Farbotko; K. W. Jó?wiak

1982-01-01

195

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

196

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

197

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

Microsoft Academic Search

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

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

1992-01-01

198

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

NASA Astrophysics Data System (ADS)

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.; Yaskovets, I. I.; Uvarova, I. Y.; Dolbin, A. V.; Esel'son, V. B.; Basnukaeva, R. M.; Vinnikov, N. A.

2014-04-01

199

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

200

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

201

Hydrogen absorption and desorption properties of a novel ScNiAl alloy  

NASA Astrophysics Data System (ADS)

A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen reversibly. In this compound, hydrogen absorption is a two-step process; solid solution of hydrogen at temperatures below 180°C and decomposition into ScH2 and NiAl at higher temperatures. Detailed analysis of the hydrogen absorption/desorption has been performed using in situ synchrotron radiation powder X-ray diffraction and thermal desorption spectroscopy. The apparent activation energy for hydrogen desorption was determined to be 182 kJ/mol and the material is stable during cycling.

Sobkowiak, Adam; Ångström, Jonas; Nielsen, Thomas Kollin; Cerenius, Yngve; Jensen, Torben R.; Sahlberg, Martin

2011-07-01

202

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

203

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

204

Thermal Desorption of Sodium Atoms from Thin SiO2 Films  

NASA Astrophysics Data System (ADS)

The adsorption and thermal desorption of Na from thin SiO2 films have been studied. X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS), low energy ion scattering (LEIS), temperature-programmed desorption (TPD), low energy electron diffraction (LEED) and work function measurements have been used to characterize the growth mechanism and properties of stoichiometric SiO2 films deposited onto a Re (0001) substrate. Upon deposition of Na onto SiO2 at 250 K, the first monolayer of Na exhibits ionic character, and evidence of metallic Na (plasmon features in XPS) is observed for higher coverages. TPD spectra for Na from SiO2 include a monolayer peak at ~700 K, and the multilayer peak due to sublimation of bulk Na at ~330 K. Penetration of Na into SiO2 can be induced by heating, or by He ion bombardment of a Na/SiO2 layer. The sticking probability for Na on SiO2 is ~0.5 at 250 K, and it decreases at higher substrate temperatures.

Yakshinskiy, B. V.; Madey, T. E.; Ageev, V. N.

205

OTEC gas-desorption studies  

SciTech Connect

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

Chen, F.C.; Golshani, A.

1981-01-01

206

Temperature-programmed reduction of bimetallic Ir?Fe\\/Al 2 O 3 catalysts  

Microsoft Academic Search

Investigations on the temperature-programmed reduction of 3% Ir?Fe\\/Al2O3 catalysts after their oxidation at different temperatures Tox have been carried out. A substantial promoting effect of iridium on the reducibility of iron has been observed for all the investigated catalysts, at Tox applied.

T. Paryjczak; P. Zielinski; J. M. Farbotko

1986-01-01

207

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

208

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

209

Neutrino-recoil induced desorption  

Microsoft Academic Search

Nuclear decay induced [sup 37]Cl ion desorption from the electron capture decay [sup 37]Ar[r arrow][sup 37]Cl+[nu] is reported for the first time. A mixture of one part [sup 36]Ar and [similar to]5[times]10[sup [minus]5] parts [sup 37]Ar ([sup 36\\/37]Ar) is physisorbed on a gold-plated Si wafer kept at 16 K under ultrahigh vacuum conditions. The time of flight (TOF) of recoiled

L. Zhu; R. Avci; G. J. Lapeyre; M. M. Hindi; R. L. Kozub; S. J. Robinson

1994-01-01

210

Desorption Kinetics of Water from Poly (methyl methacrylate) Films and other Polymer Films  

NASA Astrophysics Data System (ADS)

We present herein the water desorption from the dipole oriented poly (methyl methacrylate) PMMA. Water desorption from PMMA presents the ``ice species'' at 150 K and a bulk peak at about 280 K. We note that the desorption peak temperature does not vary greatly with increasing coverage. The energy of desorption is obtained by employing the Arrhenius and Polany-Wigner equations. The comparison with previous thermal desorption spectra of water from two ferroelectric polymers is also discussed. [1] Dowben, P.A., Rosa, Luis G., Ilie, C.C., Zeitschrift f"ur Physikalische Chemie 222 (2008) 755-778. [2] Ilie, C.C., Rosa, L.G., Poulsen, M., Takacs, J., Integrated Ferroelectrics (2011) 125:1, 98-103.

Ilie, Carolina; Kane, Thorin; Netusil, Ross; Yorke, Anastasia

2013-03-01

211

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

212

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

213

Temperature-programmed reduction and oxidation of metals supported on. gamma. -alumina  

Microsoft Academic Search

Quantitative measurements of temperature-programmed reduction and oxidation (TPR\\/TPO) at temperatures up to 1200°C were used to characterize 2% metal on γ-alumina catalysts. The TPR\\/TPO results were also compared with the redox behavior of the bulk compounds. It was found that supported FeâOâ, MoOâ, and NiO could be reduced to metal only at temperatures near 1100°C. In all cases reduction of

A. Kadkhodayan; A. Brenner

1989-01-01

214

Probing adsorbed water on lunar regolith materials using thermal and non-thermal desorption (Invited)  

NASA Astrophysics Data System (ADS)

Results from the Moon Mineralogy Mapper (M3) on the Chandrayaan-1 spacecraft, the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini during its flyby of the moon in 1999, and the extended mission for the Deep Impact Spacecraft (EPOXI) have recently implicated the existence of hydroxyl and water on the Moon. More recently, the potential presence of water on and within the surface regolith material of the Moon was somewhat validated by the Lunar Crater Observation and Sensing Satellite (LCROSS) impact event. LCROSS examined ejecta from a permanently-shadowed crater in the southern polar region, whereas the spacecraft observations characterized optical features in the 2-3.5 micron region throughout the polar and equatorial regions on the sunlit side. These optical features are thought to be indicative of hydroxyl and/or water-bearing materials with concentrations between 10 - 1000 parts per million and possibly higher. Though the source(s) of the hydroxyl and water is (are) not known, their formation via solar wind proton irradiation has been strongly suggested. There is precedent in the literature for proton irradiation-induced defect production and hydroxyl formation in silicates and some minerals. However, there are actually no reports that clearly indicate that proton irradiation leads to the formation of molecular water. We report our recent experimental probes of the desorption kinetics and binding energies of water adsorbed on minerals such as anorthosite, albite and a standard JSC1A lunar stimulant material. The temperature programmed desorption profiles clearly indicate the presence of chemisorbed water for all materials studied. The chemisorbed water requires intrinsic surface and grain boundary defects. We also report a combined low-energy (5-100 eV) electron and 5 keV proton (D+) beam bombardment study of anorthosite, albite and JSC-1A. Low-energy electron stimulated production and desorption of H3O+ (and DH2O+ after D+ bombardment) does occur, however, this involves the intrinsic water bound to surface defects and terminal -OH groups. Ion-beam bombardment does produce terminal -OH (OD) sites as expected, however, we do not observe ion-beam induced production of molecular water. Though molecular water formation is not induced via electronic excitations brought about by solar particle impact events, it may be produced via a thermally-induced recombinative desorption process. This seems to require temperatures well above the high temperatures (400K) reached as a result of solar irradiation and may also require trapped hydrogen.

Orlando, T. M.; McLain, J.; Poston, M.; Greives, G.; Alexandrov, A.; Dyar, M. D.; Hibbitts, C.

2010-12-01

215

Low-temperature CO oxidation over CuO-CeO 2\\/SiO 2 catalysts: Effect of CeO 2 content and carrier porosity  

Microsoft Academic Search

The effects of CeO2 contents and silica carrier porosity with their pore diameters ranging from 5.2 nm to 12.5 nm of CuO–CeO2\\/SiO2 catalysts in CO oxidation were investigated. The catalysts were characterized by N2 adsorption\\/desorption at low temperature, X-ray diffraction (XRD), temperature-programmed reduction by H2 (H2-TPR), oxygen temperature programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS). The results suggested that,

Jingjie Luo; Wei Chu; Huiyuan Xu; Chengfa Jiang; Tao Zhang

2010-01-01

216

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

SciTech Connect

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

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

2010-01-01

217

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

218

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

219

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.

Fojut, Tessa L.; Young, Thomas M.

2014-01-01

220

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) [Allentown, PA

1986-01-01

221

Evaluation of a structure-driven retention model for temperature-programmed gas chromatography.  

PubMed

The solvation parameter model is suitable for describing the retention properties of compounds of varied structure in temperature-programmed gas chromatography. An empirical second-order model provides a good account of the change in system constants as a function of program rate. These relationships codify the reduction in retention time at higher program rates and changes in elution order (selectivity) with program rate. The prediction of retention times from structure, while quite good, is probably adversely affected by descriptor quality and the possibility of a mixed retention mechanism on polar stationary phases. Plots of experimental against predicted temperature-programmed retention times for varied compounds are linear but generally contain a small bias from an ideal model (slope of one and an intercept of zero). The average absolute deviation in temperature-programmed retention times on three columns (DB-210, DB-1701 and EC-Wax) varied from 0.15 to 0.89 min with the best results obtained at higher program rates on the columns of lower polarity. PMID:14760855

Nawas, Mohamed I; Poole, Colin F

2004-01-01

222

Desorption of CO{sub 2} from MDEA and activated MDEA solutions  

SciTech Connect

A packed column was used for investigating the desorption rate of CO{sub 2} from aqueous methyldiethanolamine (MDEA) and activated MDEA solutions. Experiments were conducted within the temperature range 30--70 C, the concentration of MDEA was 4.28 kmol/m{sup 3}, and the concentration of piperazine (PZ) was 0.10 kmol/m{sup 3} for aqueous activated MDEA solutions. Experimental data confirmed that the kinetics model of absorption CO{sub 2} into aqueous MDEA and activated MDEA solutions can be applicable to the situations in which desorption occurs, and the desorption rate of model predictions agree well with that of experimental determination.

Xu, G.W.; Zhang, C.F.; Qin, S.J.; Zhu, B.C. [East China Univ. of Science and Technology, Shanghai (China). Research Inst. of Inorganic Chemical Technology

1995-03-01

223

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

NASA Astrophysics Data System (ADS)

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

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

224

Characterization of silica- and alumina-supported vanadia catalysts using temperature programmed reduction  

Microsoft Academic Search

Supported and bulk vanadia catalysts are important catalysts for the partial oxidation of hydrocarbons. The nature of the vanadia-support interaction for silica and alumina-supported V[sub 2]O[sub 5] catalysts was investigated using temperature programmed reduction (TPR), temperature programmed oxidation, and solid-state [sup 51]V NMR. Solid-state [sup 51]V NMR for the V[sub 2]O[sub 5]\\/SiO[sub 2] catalysts indicated the presence of microcrystalline bulk-like

M. M. Koranne; J. G. Jr. Goodwin; G. Marcelin

1994-01-01

225

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

SciTech Connect

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

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

1982-09-01

226

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

PubMed

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

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

2014-08-01

227

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

Microsoft Academic Search

We utilize accelerated molecular dynamics to simulate alkane desorption from the basal plane of graphite. Eight different molecules, ranging from n-pentane to n-hexadecane, are studied in the low coverage limit. Acceleration of the molecular dynamics simulations is achieved using two different methods: temperature acceleration and a compensating potential scheme. We find that the activation energy for desorption increases with increasing

Kelly E. Becker; Kristen A. Fichthorn

2006-01-01

228

Development of thermal desorption gas chromatography\\/mass spectrometry as a rapid method for ambient particulate characterization  

Microsoft Academic Search

A direct thermal desorption gas chromatography\\/mass spectrometry (TD GC\\/MS) method for air particulate matter (PM) analysis of volatile and semivolatile organic compounds was investigated. This technique uses a specially designed microdesorption GC inlet utilizing an inductively heated ferromagnetic foil with a Curie point temperature suitable for desorption, which can accommodate microgram amounts of material deposited on a thin strip of

Sue Anne N. Sheya

2002-01-01

229

Calculations of thermal desorption spectra of hydrogen molecule and hydrocarbon molecule from graphite using the mass balance equations  

Microsoft Academic Search

The thermal desorption spectra of hydrogen molecules and hydrocarbon molecules emitted from graphite have been theoretically calculated using the solution of the mass balance equations, in which the rate constants of thermal detrapping, retrapping, local molecular recombination, and hydrocarbon formation are included.It is shown that the peak temperature of the thermal desorption spectra of both hydrogen and hydrocarbon molecules is

Kenji Morita; Yoshio Muto

1995-01-01

230

Low energy electron stimulated desorption from DNA films dosed with oxygen  

SciTech Connect

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

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

2012-06-21

231

Temperature-programmed reduction of MoOâ and MoOâ  

Microsoft Academic Search

The reduction of MoOâ and MoOâ is studied by temperature-programmed reduction (TPR). TPR patterns appear to be highly dependent on HâO content of the reducing mixture, sample size, precalcination temperature, and heating rate. Activation energy values for reduction have been calculated from TPR series with various heating rates. A consistent interpretation of the complex TPR results is constructed, in which

P. Arnoldy; J. C. M. de Jonge; J. A. Moulijn

1985-01-01

232

Temperature-programmed Reduction of Metal-exchanged Zeolite-a Catalysts  

Microsoft Academic Search

The reduction of metal (Co, Ni, and Cu)-exchangedzeolite-A was studied by a temperature programmed reduction (TPR) technique.\\u000a The TPR profiles indicate that the metals are in a dispersed form. The hydrogen consumption in the reduction process demonstrates\\u000a that the metals are present in monovalent and divalent forms. High-temperature reduction peaks are also observed in the cases\\u000a of CoA and NiA.

M. Afzal; G. Yasmeen; M. Saleem; J. Afzal

2000-01-01

233

Characterization of platinum on sulfated zirconia catalysts by temperature programmed reduction  

Microsoft Academic Search

Temperature programmed reduction, X-ray photoelectron spectroscopy, and X-ray diffraction were used for comparative characterization of Pt on sulfated and nonsulfated zirconia catalysts calcined both in situ and ex situ at different temperatures in the range 25-800°C. The effect of sulfur species on the state of Pt was twofold. They decreased the interactions between Pt oxide and the support, thus leading

A. Dicko; Xuemin Song; A. Adnot; A. Sayari

1994-01-01

234

Temperature-programmed reduction and CO oxidation studies over Ce–Sn mixed oxides  

Microsoft Academic Search

The reduction behaviour of Ce–Sn mixed oxides has been studied by a temperature-programmed hydrogen reduction technique and compared with that of pure SnO2 and CeO2. The mixed oxides were found to reduce at lower temperature as compared to that of individual oxides. Carbon monoxide oxidation studies showed that mixed oxides have better activity for CO oxidation reaction than the constituent

R. Sasikala; N. M. Gupta; S. K. Kulshreshtha

2001-01-01

235

Desorption of COâ from MDEA and activated MDEA solutions  

Microsoft Academic Search

A packed column was used for investigating the desorption rate of COâ from aqueous methyldiethanolamine (MDEA) and activated MDEA solutions. Experiments were conducted within the temperature range 30--70 C, the concentration of MDEA was 4.28 kmol\\/m³, and the concentration of piperazine (PZ) was 0.10 kmol\\/m³ for aqueous activated MDEA solutions. Experimental data confirmed that the kinetics model of absorption COâ

Guo-Wen Xu; Cheng-Fang Zhang; Shu-Jun Qin; Bin-Chen Zhu

1995-01-01

236

Time of flight spectra in thermal desorption of helium  

NASA Astrophysics Data System (ADS)

Time of flight spectra are calculated within the cascade model of phonon-mediated desorption for helium desorbing from graphite, sapphire and Nichrome. One and three-dimensional theories are compared. Deviations from Knudsen's cosine law are traced to dynamical effects. The spectra are — as a function of time — narrower than a Maxwellian distribution and their maxima are generally shifted to shorter times indicating that the desorbed molecules are hotter than the solid temperature. Relevant experiments are discussed. Experimental geometries are analysed.

Gortel, Z. W.; Kreuzer, H. J.; Schäff, M.; Wedler, G.

1983-12-01

237

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.

2002-01-01

238

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

Microsoft Academic Search

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

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

2006-01-01

239

Pentachlorophenol adsorption and desorption characteristics of granular activated carbon—I. Isotherms  

Microsoft Academic Search

The adsorption\\/desorption of pentachlorophenol (PCP) with Calgon F300 granular activated carbon (GAC) was studied and modelled. A modified Radke-Prausnitz (1972) isotherm model, incorporating a temperature- and pH-dependent proportionality constant, was found to best describe the observed PCP adsorption and desorption. The modified isotherm is valid in the ranges 4 ? pH ? 11 and 10 ? T ? 60°C. The

Abdul H. Mollah; Campbell W. Robinson

1996-01-01

240

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

Microsoft Academic Search

Thermal desorption spectroscopy (TDS), along with Auger electron spectroscopy, was used to study the desorption of H2 and CO from baked 304 and 347 stainless-steel samples exposed only to residual gases. Both 347 and 304 samples gave identical TDS spectra. The spectra for CO contained a sharp leading peak centered in the temperature range 410-440C and an exponentially increasing part

S. Rezaie-Serej; R. A. Outlaw

1994-01-01

241

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

SciTech Connect

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

Marenkov, E. D., E-mail: edmarenkov@gmail.com [National Nuclear Research University Moscow Engineering and Physics Institute (Russian Federation); Smirnov, R. D.; Krasheninnikov, S. I. [University of California, San Diego (United States)] [University of California, San Diego (United States)

2013-11-15

242

Layer growth and desorption kinetics of a discoid molecular acceptor on Au(1 1 1)  

Microsoft Academic Search

The layer growth and desorption kinetics of discoid organic acceptor molecules hexaazatriphenylene-hexacarbonitrile (HAT-CN) on Au(111) have been studied by thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD). The molecules form two wetting layers of flat lying molecules when evaporated at or below room temperature. Increasing the coverage beyond two monolayers and upon

Paul Frank; Norbert Koch; Markus Koini; Ralph Rieger; Klaus Müllen; Roland Resel; Adolf Winkler

2009-01-01

243

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

NASA Astrophysics Data System (ADS)

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

Samokhvalov, Alexander; Tatarchuk, Bruce J.

2011-07-01

244

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

245

Temperature-programmed reduction. Metal-support interaction on supported monometallic Ru and Cu Catalysts  

Microsoft Academic Search

Ru and Cu samples supported on SiO2, Al2O3 and MgO were studied by the temperature-programmed reduction (TPR) technique. Experiments were carried out both on unreduced impregnated salts and after oxidation of already reduced samples.

S. Galvagno; C. Crisafulli; R. Maggiore; G. R. Tauszik; A. Giannetto

1985-01-01

246

Temperature-programmed reduction of nickel\\/silica catalysts using [ 3 H]-hydrogen  

Microsoft Academic Search

Details of a novel temperature-programmed reduction technique are described, which allowed nickel oxide\\/silica catalysts to be reduced with [3H]-hydrogen. In addition to obtaining characteristic reduction profiles for the catalysts it was possible to study hydrogen isotope exchange over the catalysts during the reduction process.

J. R. Jones; A. P. Sharratt; S. D. Jackson; R. W. Griffiths; L. F. Gladden; F. J. Robertson; G. Webb

1992-01-01

247

Temperature-programmed reduction and oxidation of bimetallic catalysts Rh?Ag\\/Al 2 O 3  

Microsoft Academic Search

Investigations of temperature-programmed reduction and oxidation of bimetallic catalysts Rh?Al2O3 seem to indicate that there are no strong interactions between rhodium and silver. Bimetallic catalysts rather show the additive properties of individual components, i. e. rhodium and silver.

T. Paryjczak; J. Góralski; K. W. Jó?wiak

1981-01-01

248

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

Microsoft Academic Search

The oxygen content and reducibilities of four base metal oxides, six nonconducting cuprates, and three superconducting cuprates were investigated by temperature-programmed reduction (TPR) from 30 to 900C. It was shown that the copper, bismuth, and thallium ions of these oxides were reduced to the zero valence state. Thus, TPR is a useful technique for determining the actual oxygen stoichiometry of

I. Halasz; Hungwen Jen; A. Brenner; M. Shelef; S. Kao; K. Simonng

1991-01-01

249

Temperature-programmed reduction study of chromium oxide supported on zirconia and lanthana–zirconia  

Microsoft Academic Search

Temperature-programmed reduction (TPR) has been applied to study the reduction behavior of chromium oxide supported on pure zirconia and on lanthana-containing zirconia. The results revealed influences of support nature and chromium loading on the state of the supported chromium oxide. With catalysts containing lanthana and only low amounts of chromium, the decrease of the chromium oxidation state during TPR corresponded

D. L Hoang; H Lieske

2000-01-01

250

High-Temperature Burner-Duct-Recuperator (HTBDR) Program. Annual Report, October 1981-September 1982.  

National Technical Information Service (NTIS)

The objectives of the HTBDR program are to develop, construct, operate, and evaluate a 2000 exp 0 F combustion air heat recovery system in a typical industrial furnace application. The HTBDR comprises a high-temperature ceramic recuperator; a dual fuel bu...

M. Coombs D. Kotchick H. Strumpf

1983-01-01

251

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

ERIC Educational Resources Information Center

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

Kelter, Paul B.; Carr, James D.

1983-01-01

252

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

253

Accelerating rare events while overcoming the low-barrier problem using a temperature program  

NASA Astrophysics Data System (ADS)

We present a hierarchical coarse-grained simulation technique called the temperature programmed molecular dynamics (TPMD) method for accelerating molecular dynamics (MD) simulations of rare events. The method is targeted towards materials where a system visits many times a collection of energy basins in the potential energy surface, called a superbasin, via low-barrier moves before escaping to a new superbasin via a high-barrier move. The superbasin escape events are rare at the MD time scales. The low-barrier moves become accessible to MD by employing a temperature program, i.e., the MD temperature changes during the simulation. Once a superbasin is detected, transitions within the superbasin are ignored, in effect causing coarse-graining of basins. The temperature program enables the system to escape from the superbasin with reduced computational cost thereby overcoming the "low-barrier" problem. The main advantage of our approach is that the superbasin-to-superbasin transitions are accurately obtained at the original temperature with a reasonable computational cost. We study surface diffusion in Ag/Ag(001) system and demonstrate the ability of the TPMD method to span a wide-range of timescales.

Divi, Srikanth; Chatterjee, Abhijit

2014-05-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

255

Electron-stimulated desorption of D+ from D2O ice: Surface structure and electronic excitations  

NASA Astrophysics Data System (ADS)

We present a study of the electron-stimulated desorption of deuterium cations (D+) from thin (1-40 ML) D2O ice films vapor deposited on a Pt(111) substrate. Measurements of the total yield and velocity distributions as a function of temperature from 90 to 200 K show that the D+ yield changes with film thickness, surface temperature, and ice phase. We observe two energy thresholds for cation emission, near 25 and 40 eV, which are weakly dependent upon the ice temperature and phase. The cation time-of-flight (TOF) distribution is at least bimodal, indicating multiple desorption channels. A decomposition of the TOF distributions into ``fast'' and ``slow'' channels shows structure as a function of excitation energy, film thickness, and temperature. The D+ yield generally increases with temperature, rising near 120 K on amorphous ice, and near 135 K on crystalline ice. The amorphous-crystalline phase transition at ~160 K causes a drop in total desorption yield. The temperature dependence of D- desorption via the 2B1 dissociative electron attachment resonance is very similar to the slow D+ yield, and likely involves similar restructuring and lifetime effects. The data collectively suggest that a thermally activated reduction of surface hydrogen bonding increases the lifetime of the excited states responsible for ion desorption, and that these lifetime effects are strongest for excited states involving a1 bands

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

1997-08-01

256

Kinetic analysis of thermogravimetric data obtained under linear temperature programming—a method based on calculations of the temperature integral by interpolation  

Microsoft Academic Search

A new technique, called interpolation method, with general application in the kinetic analysis of processes studied by thermogravimetry (TG) under linear temperature programming is developed. It is based on the linear relationship, with slope 1, between logg(?) and logI(?, ?) for the appropriate kinetic function, where I(?, ?) is the normalized temperature integral, ? the normalized temperature (?=T\\/T0) and ?

J. J. M Órfão; F. G Martins

2002-01-01

257

Adsorption and desorption characteristics of arsenic onto ceria nanoparticles  

PubMed Central

The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (?H0, ?S0, and ?G0) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment.

2012-01-01

258

A genetic program promotes C. elegans longevity at cold temperatures via a thermosensitive TRP channel.  

PubMed

Both poikilotherms and homeotherms live longer at lower body temperatures, highlighting a general role of temperature reduction in lifespan extension. However, the underlying mechanisms remain unclear. One prominent model is that cold temperatures reduce the rate of chemical reactions, thereby slowing the rate of aging. This view suggests that cold-dependent lifespan extension is simply a passive thermodynamic process. Here, we challenge this view in C. elegans by showing that genetic programs actively promote longevity at cold temperatures. We find that TRPA-1, a cold-sensitive TRP channel, detects temperature drop in the environment to extend lifespan. This effect requires cold-induced, TRPA-1-mediated calcium influx and a calcium-sensitive PKC that signals to the transcription factor DAF-16/FOXO. Human TRPA1 can functionally substitute for worm TRPA-1 in promoting longevity. Our results reveal a previously unrecognized function for TRP channels, link calcium signaling to longevity, and, importantly, demonstrate that genetic programs contribute to lifespan extension at cold temperatures. PMID:23415228

Xiao, Rui; Zhang, Bi; Dong, Yongming; Gong, Jianke; Xu, Tao; Liu, Jianfeng; Xu, X Z Shawn

2013-02-14

259

Laser induced thermal desorption of hydrogen from Zr(0 0 0 1): Relationship to water dissociation and hydrogen dissolution  

NASA Astrophysics Data System (ADS)

On metals such as Zr, during hydrogen exposure, dissolution competes with desorption; this competition can be probed by thermal desorption at different heating rates. In the case of desorption from preadsorbed hydrogen, only ˜1% of the hydrogen can be desorbed even at heating rates of >10 10 K s -1. Recent measurements of the dynamics of hydrogen released by water dissociation on Zr(0 0 0 1) [G. Bussière, M. Musa, P.R. Norton, K. Griffiths, A.G. Brolo, J.W. Hepburn, J. Chem. Phys. 124 (2006) 124704] have shown that the desorbing hydrogen originates from the recombinative desorption of adsorbed H-atoms and that over 25% of the water collisions lead to hydrogen desorption. To gain further insight into the desorption and dissolution of hydrogen and in an attempt to resolve the paradox of the different desorption yields from H 2 vs. H 2O exposures, we report new measurements of the laser induced thermal desorption (LITD) of hydrogen from Zr(0 0 0 1) at initial temperatures down to 90 K. The low temperature was chosen because work function measurements suggested that hydrogen adsorbed into only the outermost (surface site) of the two available adsorption sites (surface and subsurface), from which we postulated much more efficient desorption at high heating rates compared to desorption from the sub-surface sites. However, hydrogen desorption by LITD from Zr(0 0 0 1) at 90 K still only accounts for 1% of the adsorbed species, the remainder dissolving into the bulk at LITD heating rates. The different yields alluded to above remain unexplained (Bussière, 2006).

Hu, Yuhai; Griffiths, Keith; Norton, Peter R.; Bussière, Guillaume; Hepburn, John

2007-09-01

260

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

SciTech Connect

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

Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Xiao Xue Deng; Pershing, D.W. (Univ. of Utah, Salt Lake City (United States)); Cundy, V.A.; Leger, C.B.; Jakway, A.L. (Louisiana State Univ., Baton Rouge (United States))

1992-05-01

261

VAC*TRAX - Thermal desorption for mixed wastes  

SciTech Connect

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

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

1995-12-01

262

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

263

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

Microsoft Academic Search

This report describes the successful completion of the development of an accurate in-process measurement instrument for galvanneal steel surface temperatures. This achievement results from a joint research effort that is a part of the American Iron and Steel Institute's (AISI) Advanced Process Control Program, a collaboration between the U.S> Department of Energy and fifteen North American Steelmakers. This three-year project

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

1999-01-01

264

Phase Transformations in Iron Fischer–Tropsch Catalysts during Temperature-Programmed Reduction  

Microsoft Academic Search

Temperature-programmed reduction using both carbon monoxide (CO-TPR) and hydrogen (H2-TPR) was used to study the phase transformations in iron catalysts. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) allowed us to follow the phase transformations in these iron catalysts during TPR. Two catalysts were used, a model supported catalyst with a nonporous silica support and a precipitated catalyst with

Yaming Jin; Abhaya K. Datye

2000-01-01

265

A Temperature-Programmed-Reduction Study on Alkali-Promoted, Carbon-Supported Molybdenum Catalysts  

Microsoft Academic Search

The reducibility of a series of carbon-supported, molybdenum-based catalysts with or without a potassium promoter was investigated using temperature-programmed reduction (TPR). The Mo loading and the K-doping level influence the reducibility of the K-Mo\\/C catalysts. The TPR spectra of both Mo\\/C and K-promoted Mo\\/C catalysts generally consist of four peaks. Two of these (located around 350 and 440°C) are attributed

Lijuan Feng; Xianguo Li; Dady B. Dadyburjor; Edwin L. Kugler

2000-01-01

266

The kinetic study of temperature-programmed reduction of nickel oxide in hydrogen atmosphere  

Microsoft Academic Search

The powder samples of nickel oxide were synthesized by sol–gel procedure. The non-isothermal reduction of nickel oxide using hydrogen was investigated by temperature-programmed reduction (TPR) at four different heating rates (2.5, 5, 10 and 20?Cmin-1). Reaction kinetics parameters (Ea, lnA) were determined using a few methods: Stationary point (SP), Kissinger, Friedman, Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. The Málek's kinetic procedure was

B. Jankovi?; B. Adna?evi?; S. Mentus

2008-01-01

267

Investigation of the chromium oxide system by means of temperature-programmed reduction  

Microsoft Academic Search

A temperature-programmed reduction study of Cr2O3 samples prepared at 673 and 1073 K in different gaseous media, air or helium, was carried out. It was established that one or two peaks arise from the Cr+3?Cr+2 transition for samples treated in air or inert gas, respectively. Results of chemical analysis, X-ray diffraction and adsorption measurements suggest that the different behaviour of

L. I. Ilieva; D. H. Andreeva

1995-01-01

268

In situ EXAFS analysis of the temperature programmed reduction of Cu-ZSM-5  

Microsoft Academic Search

High resolution in situ EXAFS during temperature-programmed reduction was performed on Cu-ZSM-5 to elucidate the state of copper under reaction conditions. Improvements in hardware and software allowed rapid acquisition of both XANES and EXAFS data during reduction, in particular, allowing observation of characteristic preedge features from various Cu oxidation states. EXAFS fitting and factor analysis of the normalized XANES edge

Michael K. Neylon; Christopher L. Marshall; A. Jeremy Kropf

2002-01-01

269

An alternative method for parameter identification from temperature programmed reduction (TPR) data  

Microsoft Academic Search

The experimental method of temperature programmed reduction (TPR) for the investigation of gas–solid reactions is well established and widely used since the 1970s. With regard to the temporal and financial effort for TPR measurements, the quantitative model-based analysis of the data is not adequately developed. The TPR data analysis is comprised of two aspects: a discrete model identification and a

Peter Heidebrecht; Vladimir Galvita; Kai Sundmacher

2008-01-01

270

Characterizations of alumina-supported gold with temperature-programmed reduction  

Microsoft Academic Search

Supported Au\\/Al2O3 samples of different gold loadings were prepared by the deposition-precipitation of AuCl3 onto alumina. Prepared samples were physically characterized by techniques of atomic emission (ICP), X-ray diffraction (XRD), transmission electron microscope (TEM) and temperature-programmed reduction (TPR). According to TEM and XRD observations, the size of gold crystallites dispersed on samples freshly prepared at 300K was ca. 8nm. TPR

Chao-Kang Chang; Yeong-Jey Chen; Chuin-tih Yeh

1998-01-01

271

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

272

Molybdenum species identification on pillared clays by temperature-programmed reduction  

Microsoft Academic Search

In order to use pillared clays (PILCs) as a support for HDS catalysts, a work was undertaken on which the effect of the support on creation and distribution of species was studied. As a support, aluminum-pillared clay (Al-PILC) and different precursors and loading conditions were used. Temperature-programmed reduction (TPR) and UV-diffuse reflectance (UV-DRS) techniques were applied to identify the formed

P. Salerno; M. B. Asenjo; S. Mendioroz

2001-01-01

273

Temperature-programmed reduction study on carbon-supported platinum–gold alloy catalysts  

Microsoft Academic Search

Alloy catalysts of Pt–Au\\/C with different Pt\\/Au ratios were prepared by the precipitation–deposition of metal chlorides and reduced by H2 at 470 K. The surface composition of alloy crystallites deposited on the prepared catalysts was characterized by a technique of temperature-programmed reduction (TPR). In the characterization, O2 was chemisorbed on the reduced catalysts and the chemisorbed O2 was reduced by

Kuan-Wen Wang; Chuin-Tih Yeh

2008-01-01

274

Analysis of temperature-programmed reduction profiles from metal-supported catalysts  

Microsoft Academic Search

An experimental procedure is proposed to enable analysis of Hâ emission\\/consumption data obtained during temperature-programmed reduction (TPR) of a metal-supported catalyst. Using the methods described allows one to account for chemical processes other than reduction and thus remove their contribution from the TPR profile. The resulting real TPR spectrum is a signature that reflects only reduction processes that occur under

Y. J. Huang; J. Xue; J. A. Schwarz

1988-01-01

275

Au\\/iron oxide catalysts: temperature programmed reduction and X-ray diffraction characterization  

Microsoft Academic Search

Gold on iron oxides catalysts have been characterized by temperature programmed reduction (TPR) and X-ray diffraction spectroscopy (XRD). The influence of preparation method, gold loading and pretreatment conditions on the reducibility of iron oxides have been investigated. On the impregnated Au\\/iron oxide catalysts as well as on the support alone the partial reduction of Fe(III) oxy(hydroxides) to Fe3O4 starts in

G Neri; A. M Visco; S Galvagno; A Donato; M Panzalorto

1999-01-01

276

Study of sulphur in oxidised coals by atmospheric pressure-temperature programmed reduction  

Microsoft Academic Search

The influence of oxidation of coal, performed with different oxidising agents, on the sulphur species was studied. Conversions of the sulphur species were investigated by the Atmospheric Pressure-Temperature Programmed Reduction method (AP-TPR). The removal of pyrite proved to be advantageous for AP-TPR analysis. It was found that non-thiophene sulphur species undergo easier oxidation by different agent then thiophenic structures.

M. Kozlowski; R. Pietrzak; H. Wachowska; J. Yperman

2004-01-01

277

Temperature-programmed-reduction studies of nickel oxide\\/alumina catalysts: effects of the preparation method  

Microsoft Academic Search

Two series of NiOAl2O3 catalysts with various metal loadings were prepared by incipientwetness impregnation and coprecipitation methods. The reducibilities of NiO over these catalysts were investigated by the temperature-programmed reduction (TPR) technique. For impregnated NiAl2O3 catalysts, more than one species was detected by TPR. At low nickel loadings, the NiO?Al2O3 interaction is strong, and at high Ni loadings NiO is

Chiuping Li; Yu-Wen Chen

1995-01-01

278

Application of temperature-programmed reduction to the characterization of anionic clays  

Microsoft Academic Search

Temperature-programmed reduction (TPR) has been used for characterization of anionic clays containing reducible cations. Results are reported on the reducibility properties of several anionic clays with the hydrotalcite or takovite structure containing transition metal cations, and of the products (usually a mixture of rock-salt-type oxides and spinels) thereof obtained by calcination. The systems studied include those possessing two reducible cations

V. Rives; M. A. Ulibarri; A. Montero

1995-01-01

279

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

Microsoft Academic Search

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

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

2008-01-01

280

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

281

Thermal Desorption Analysis of Hydrogen in High Strength Martensitic Steels  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

282

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

283

Simulation of NO and NO 2 sorption–desorption–reduction behaviours on Pt-impregnated HPW supported on TiO 2  

Microsoft Academic Search

NO and NO2 (NOx) sorption, desorption and reduction by hydrogen, carbon monoxide and\\/or propene were investigated on a TiO2-supported heteropolyacid, 12-tungstophosphoric acid hexahydrate (HPW), promoted by platinum. A model taking into account NOx sorption, desorption and reduction was established. Kinetic constants for NOx sorption, desorption and reduction were extracted by modelling for the investigated range of temperature (170–300°C).

M. Labaki; M. Mokhtari; J. F. Brilhac; S. Thomas; V. Pitchon

2007-01-01

284

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

285

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

SciTech Connect

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

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

2009-03-15

286

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

PubMed

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

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

2014-07-01

287

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

PubMed

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. PMID:24832297

Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

2014-05-14

288

Film growth, adsorption and desorption kinetics of indigo on SiO2  

NASA Astrophysics Data System (ADS)

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; Resel, Roland; Winkler, Adolf

2014-05-01

289

Water Vopar Desorption Characteristics of Powder Type Organic Sorbent in an Air Fluidized Bed  

NASA Astrophysics Data System (ADS)

This paper has dealt with water vapor desorption characteristics of powder type organic sorbent in an air fluidized bed. The Powder type organic sorbent was fluidized in a rectangular vessel by a humid air flow. The desorption rate of vapor and the variation in temperature in the sorbent bed were measured under various air temperature and humidity conditions. It was found that the air pressure loss of the fluidized sorbent layer increased with in an increase in water vapor concentration. Finally Sherwood number for mass transfer was correlated by means of Reynolds number,modified Stefan number. The ratio of sorbent particle diameter to the fluidized bed height and Schmidt number.

Inaba, Hideo; Kida, Takahisa; Horibe, Akihiko; Kameda, Kiyohiro; Okamoto, Tamio

290

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

291

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

292

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

293

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

294

Winter wheat cells subjected to freezing temperature undergo death process with features of programmed cell death.  

PubMed

Programmed cell death is a process defined as genetically regulated self-destruction or cell suicide. It can be activated by different internal and external factors, but few studies have investigated whether this process occurs under cold and freezing temperatures. In this study, a freezing treatment (-8 °C for 6 h) induced cell death with features of programmed cell death in suspension cultures of winter wheat (Triticum aestivum L.). This process occurred for 10 days after cold exposure. The death of cells in culture was slow and prolonged, and was accompanied by protoplast shrinkage, DNA fragmentation, and an increase in the level of reactive oxygen species. Other changes observed after the freezing treatment included an increase in the respiration rate, changes in mitochondrial transmembrane potential (?? m ), and the release of cytochrome c from mitochondria into the cytosol. These findings indicated that mitochondria are involved in the cell death process that occurs after a freezing treatment in cells of winter wheat. PMID:24126671

Lyubushkina, Irina V; Grabelnych, Olga I; Pobezhimova, Tamara P; Stepanov, Aleksey V; Fedyaeva, Anna V; Fedoseeva, Irina V; Voinikov, Victor K

2014-05-01

295

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

SciTech Connect

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

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

2007-01-01

296

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

PubMed

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

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

2013-05-01

297

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

298

Hydrogen bonding between water and methanol studied by temperature-programmed time-of-flight secondary ion mass spectrometry  

NASA Astrophysics Data System (ADS)

The interactions between condensed molecules at cryogenic temperatures (15-200 K) have been investigated on the basis of secondary ion mass spectrometry. It is demonstrated that the protonated molecular ions, emitted via the proton transfer reactions, provide us unique information about the reorganization of hydrogen-bonded molecules. From the CH3OH molecules adsorbed on the D2O-ice surface, the D+(CH3OH) ions are sputtered predominantly in the temperature range between 100 and 150 K since most of the CH3OH molecules are bound to the D2O layer via hydrogen bonds. A rapid and almost complete H/D exchange, yielding the D+(CH3OD) species, occurs above 150 K due to the enhanced mobility of the surface D2O molecules. Up to the desorption temperature of 180 K, a considerable amount of methanol exists on the surface without mixing with the heavy-water layer due to hydrophobicity of the methyl group. On the methanol-ice surface, the adsorbed D2O molecules form hydrogen bonds preferentially with the CH3OH molecules and tend to be incorporated in the thin-layer bulk of methanol above 120 K.

Souda, R.; Kawanowa, H.; Kondo, M.; Gotoh, Y.

2003-09-01

299

Characterization by Temperature-Programmed Reduction and by Temperature-Programmed Oxidation (TPR-TPO) of Chromium(III) Oxide-Based Catalysts: Correlation with the Catalytic Activity for Hydrofluoroalkane Synthesis  

Microsoft Academic Search

The catalytic activity of chromium (III) oxide for the fluorination of CF3CH2Cl (HCFC 133a) is proportional to the number of reversibly oxidized sites. The proportionality coefficient depends on the atmosphere employed during the pretreatment of the catalyst. The temperature-programmed reduction and temperature-programmed oxidation experiments constitute a simple technique that allows the number of reversibly oxidized chromium atoms to be measured.

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

1995-01-01

300

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

PubMed

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

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

2012-12-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

302

Characterization by temperature-programmed reduction of non-conventional catalysts for hydrotreatment  

Microsoft Academic Search

A temperature-programmed reduction (TPR) study of three series of biphasic hydrotreating (HDT) catalysts - PtS\\/?-Al2O3\\/(PtS\\/ ?-Al2O3+MoS2); Rh2S3\\/?-AlOOH\\/(Rh2S3\\/?-AlOOH+WS2) and PdS\\/?-Al2O3\\/(PdS\\/ ?-Al2O3+WS2) - is presented. In all cases, the quantity of H2S produced is larger than that which would correspond to the arithmetic addition of the quantities produced by each of the\\u000a sulfide phases alone. This fact suggests that the noble metal

S. A. Giraldo de León; P. Grange; B. Delmon

1997-01-01

303

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

NASA Astrophysics Data System (ADS)

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

Näslund, Lars-Åke

2013-12-01

304

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

PubMed

Footpad dermatitis begins early in life, and there is evidence of individual susceptibility. An experiment was conducted to evaluate the carryover effects of breeder feed restriction programs and incubation temperatures (TEM) on progeny footpad development at hatch, and 7 and 22 d. Cobb 500 fast feathering breeders were subjected to 2 dietary feed restriction programs during rearing: skip-a-day (SAD) and every-day feeding (EDF). At 60 wk of age, eggs from each group were collected and incubated according to 2 TEM, standard (S) eggshell temperature (38.1°C) and early-low late-high (LH). This second profile had low (36.9°C) eggshell temperature for the first 3 d, and standard temperature until the last 3 d when eggs were subjected to elevated (38.9°C) eggshell temperature. At hatch, 15 chicks from each treatment combination were sampled to obtain footpads for histological analysis. Seventy-two chicks per treatment were placed in 48 cages (6/cage), and raised to 22 d. At 7 and 22 d, 1 and 2 chickens, respectively, were sampled for footpads. The BW and group feed intake were recorded to obtain BW gain and feed conversion ratio at 7 and 21 d. Histological analysis assessed thickness and total area of stratus corneum (SC), epidermis, and dermis, and total papillae height. Data were analyzed as randomized complete block design in a 2 × 2 factorial arrangement of treatments. There was a negative effect of LH TEM on performance at both ages. An interaction effect on SC area and papillae height was observed at hatch. Additionally, SAD treatment increased thickness and area of footpad dermis. At 7 d, the SC parameters of the SAD progeny were increased. Epidermis thickness was affected by treatment interaction. Furthermore, LH TEM decreased epidermis thickness and dermis area. At 22 d, interaction effects were observed in thickness and area of SC and epidermis. Incubation S TEM increased thickness and area of dermis. It was concluded that breeder feed restriction programs and incubation TEM profiles may have carryover effects on histomorphological traits of footpads. PMID:24894526

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

2014-08-01

305

Formation of super'' As-rich GaAs(100) surfaces by high temperature exposure to arsine  

SciTech Connect

We report that arsine exposures between 100 and 350 {degree}C will produce super'' As-rich surfaces (arsenic coverages of up to {similar to}1.7 monolayers (ML, where 1 ML=6.26{times}10{sup 14} atoms cm{sup {minus}2})) of GaAs(100) that exhibit a {ital c}(4{times}4) low energy electron diffraction pattern. Temperature programmed desorption studies show that after AsD{sub 3} exposures of up to 2.6{times}10{sup 6} L (1 L=1{times}10{sup {minus}6} Torr s) to the Ga-stabilized surface, three excess As desorption speaks are observed with maxima at 440, 480, and 570 {degree}C. As{sub 4} desorption is detected from the lowest temperature state, while the other states desorb primarily as As{sub 2}. The significance of these results for the understanding of the atomic layer epitaxy process is addressed.

Banse, B.A.; Creighton, J.R. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1992-02-17

306

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

PubMed Central

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

2013-01-01

307

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

308

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

309

Photoinduced molecular desorption from graphene films  

NASA Astrophysics Data System (ADS)

Photoinduced molecular desorption from solid surfaces will modify the electrical transporting properties of matter and result in significant change in resistance. The UV induced resistive response of graphene films prepared by chemical vapor deposition was investigated. The resistance of graphene increased exponentially upon UV irradiation and decreased also in an exponential form when the UV light was turned off. Both processes exhibited large time constants of hundreds of seconds. UV-induced molecular desorption mechanisms for graphene, carbon nanotubes, and reduced graphene oxides were compared and discussed.

Sun, Pengzhan; Zhu, Miao; Wang, Kunlin; Zhong, Minlin; Wei, Jinquan; Wu, Dehai; Cheng, Yao; Zhu, Hongwei

2012-07-01

310

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

Microsoft Academic Search

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

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

2000-01-01

311

Absorption\\/desorption of NO x process on perovskites: performances to remove NO x from a lean exhaust gas  

Microsoft Academic Search

NOx adsorption\\/desorption capacities of perovskites (ABO3) were measured under representative exhaust gas mixture conditions at temperatures below 550°C, with A=Ca, Sr, Ba and B=Sn, Zr, Ti. The solids exhibited good NO2 sorption capacities with a reversible adsorption to desorption process according to the sequence Ba>Sr>Ca for A, while for element B the sequence Sn>Zr>Ti is observed. In the case of

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

2000-01-01

312

Effects of the Operating Conditions on Coke Deactivation of 5A Molecular Sieve in N-Decane Adsorption\\/Desorption  

Microsoft Academic Search

The influence of operating conditions (time-on-stream, temperature, pressure and paraffin feed concentration) on the deactivation of a 5A molecular sieve during the adsorption\\/desorption of n-decane has been studied using a cyclic operating procedure. After 10 adsorption\\/desorption cycles, the 5A molecular sieve used in this study showed the same deactivation level as an used industrial molecular sieve provided that the deactivation

M. A. Uguina; J. L. Sotelo; G. Calleja; J. A. Díaz; E. Castillo

2002-01-01

313

Thermal Desorption Spectroscopy Studies of Hydrogen Retention on FLIRE  

NASA Astrophysics Data System (ADS)

One advantage of using liquid Li for plasma-facing components is its ability to remove ash (He) and recycle unspent fuel (H). The Flowing Liquid-metal Retention Experiment (FLIRE) at the University of Illinois measures H and He retention in liquid Li and other molten materials. In the case of hydrogen, which is soluble in lithium, the long-term bound hydrogen contribution to the retention coefficient can be determined by heating the hydrogen-exposed lithium and measuring it's desorption rate as a function of temperature. A Thermal Desorption Spectroscopy chamber (TDS) was added to FLIRE to conduct these measurements. It has a separate heating and pumping system, and shares the RGA with the lower chamber. Helium release rate data as a function of temperature can help determine the surface recombination constant of Hydrogen atoms. Monitoring of other species like H_2O helped quantify the Li-surface oxygen content. H retention as LiH can be determined as a function of flow parameters and plasma conditions.

Olczak, W.; Nieto, M.; Stubbers, R.; Ruzic, D. N.

2003-10-01

314

Thermal analysis and temperature-programmed reduction studies of copper–zirconium and copper–zirconium–yttrium compounds  

Microsoft Academic Search

Differential thermal analysis evidenced that introduction of copper or yttrium into zirconia matrix delays its crystallization temperature. This result was connected to the stabilization of the zirconia tetragonal phase observed by X-ray diffraction. In addition, it was observed a decomposition delay of supported copper nitrate with yttrium content in a zirconia support. Temperature-programmed reduction revealed the existence of different copper

Madona Labaki; Jean-François Lamonier; Stéphane Siffert; Antoine Aboukaïs

2005-01-01

315

Multi-Routes Algorithm using Temperature Control of Boltzmann Distribution in Q value-based Dynamic Programming  

Microsoft Academic Search

In this paper, we propose a heuristic method trying to improve the efficiency of traffic systems in the global perspective, where the optimal traveling time for each origin-destination (OD) pair is calculated by extended Q value-based dynamic programming and the global optimum routes are produced by adjusting the temperature parameter in Boltzmann distribution. The key point is that the temperature

Shanqing Yu; Shingo Mabu; Manoj Kanta Mainali; Shinji Eto; Kaoru Shimada; Kotaro Hirasawa

2009-01-01

316

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...

317

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 ...

318

Desorption Activation Energies for Tritium Release from Ceramic Breeders.  

National Technical Information Service (NTIS)

Desorption has been identified as an important process in determining the kinetics of tritium release from ceramic tritium breeder materials considered for use in fusion reactors. However, details of the desorption of tritium from ceramic materials are mo...

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

1989-01-01

319

APPLICATION OF THERMAL DESORPTION TECHNOLOGIES TO HAZARDOUS WASTE SITES  

EPA Science Inventory

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

320

APPLICATION OF THERMAL DESORPTION TECHNOLOGIES TO HAZARDOUS WASTE SITES  

EPA Science Inventory

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

321

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

PubMed

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

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

2001-08-15

322

Evaluation of GeO desorption behavior in the metal/GeO2/Ge structure and its improvement of the electrical characteristics  

PubMed Central

The relation between germanium monoxide (GeO) desorption and either improvement or deterioration in electrical characteristics of metal?GeO2?Ge capacitors fabricated by thermal oxidation has been investigated. In the metal?GeO2?Ge stack, two processes of GeO desorption at different sites and at different temperatures were observed by thermal desorption spectroscopy measurements. The electrical characteristics of as-oxidized metal?GeO2?Ge capacitors shows a large flat-band voltage shift and minority carrier generation due to the GeO desorption from the GeO2?Ge interface during oxidation of Ge substrates. On the other hand, the electrical properties were drastically improved by a postmetallization annealing at low temperature resulting in a metal catalyzed GeO desorption from the top interface.

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

2010-01-01

323

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

324

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

325

Photo-desorption from copper alloys.  

National Technical Information Service (NTIS)

In support of PEP-II, a high luminosity B factory, photo-desorption of Cu alloys were measured to demonstrate suitability for ultra-high performance under high radiation loads. Results show that (eta)(sub eff)(le)2(times)10(sup (minus)6) mol/photon is a p...

W. A. Barletta M. Calderon C. Foerester H. Halama G. Korn

1992-01-01

326

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

327

Laser desorption mass spectrometry for molecular diagnosis  

NASA Astrophysics Data System (ADS)

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

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

1996-04-01

328

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

329

Adsorption/desorption behavior of protein on nanosized hydroxyapatite coatings: A quartz crystal microbalance study  

NASA Astrophysics Data System (ADS)

Protein separation relates closely to the interactions between proteins and various kinds of adsorbents. To obtain a direct and comprehensive understanding of the protein interaction at the solid/solution interface, quartz crystal microbalance (QCM) technique was employed to in situ investigate the adsorption process of bovine serum albumin (BSA) on nanosized hydroxyapatite coatings, and factors affecting its adsorption such as pH, solution ionic strength and temperature were discussed in detail. The adsorption kinetic parameter and the desorption of adsorbed BSA caused by phosphate buffer solution (PBS) introduction were investigated and discussed as well, and an adsorption/desorption mechanism has been proposed. The obtained information suggests that QCM is a useful method for monitoring the adsorption/desorption behavior of BSA on nanosized hydroxyapatite coating.

Yang, Zhengpeng; Zhang, Chunjing

2009-02-01

330

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

331

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

332

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

NASA Astrophysics Data System (ADS)

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

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

2002-09-01

333

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

334

Comparison of dynamic adsorption/desorption characteristics of toluene on different porous materials.  

PubMed

Four different types of adsorbents, SBA-15, MCM-41, NaY and SiO2, were used to study the dynamic adsorption/desorption of toluene. To further investigate the influence of pore structure on its adsorption performance, two SBA-15 samples with different microspores were also selected. It is shown that microporous material NaY has the largest adsorption capacity of 0.2873 mL/g, and the amorphous SiO2 exhibits the least capacity of 0.1003 mL/g. MCM-41 also shows a lower break through capacity in spite of the relatively small pore diameter, because it can not provide the necessary small geometric confinement for the tiny adsorbates. However, the mesoporous SBA-15 silica with certain micropore volume shows relatively higher adsorption capacity than that of MCM-41 silica. The presence of micropores directly leads to an increase in the dynamic adsorption capacity of toluene. Although NaY has the highest adsorption capacity for toluene, its complete desorption temperature for toluene is high (> 350 degrees C), which limits its wide application. On the contrary, mesoporous silica materials exhibits a good desorption performance for volatile organic compounds at lower temperatures. Among these materials mesoporous SBA-15 samples, with a larger amount micropores and a lower desorption temperature, are a potentially interesting adsorbent for the removal of volatile organic compounds. This behavior should been related with the best synergetic effect of mesopores and micropores. PMID:22655368

Zhang, Weiwei; Qu, Zhenping; Li, Xinyong; Wang, Yi; Ma, Ding; Wu, Jingjing

2012-01-01

335

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

PubMed

The Hg(0) vapor adsorption experimental results on a novel sorbent obtained by impregnating a commercially available activated carbon (Darco G60 from BDH) with silver nitrate were reported. The study was performed by using a fundamental approach, in an apparatus at laboratory scale in which a synthetic flue gas, formed by Hg(0) vapors in a nitrogen gas stream, at a given temperature and mercury concentration, was flowed through a fixed bed of adsorbent material. Breakthrough curves and adsorption isotherms were obtained for bed temperatures of 90, 120 and 150 degrees C and for Hg(0) concentrations in the gas varying in the range of 0.8-5.0 mg/m3. The experimental gas-solid equilibrium data were used to evaluate the Langmuir parameters and the heat of adsorption. The experimental results showed that silver impregnated carbon was very effective to capture elemental mercury and the amount of mercury adsorbed by the carbon decreased as the bed temperature increased. In addition, to evaluate the possibility of adsorbent recovery, desorption was also studied. Desorption runs showed that both the adsorbing material and the mercury could be easily recovered, since at the end of desorption the residue on solid was almost negligible. The material balance on mercury and the constitutive equations of the adsorption phenomenon were integrated, leading to the evaluation of only one kinetic parameter which fits well both the experimentally determined breakthrough and desorption curves. PMID:22432297

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

2011-01-01

336

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

337

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

NASA Astrophysics Data System (ADS)

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

Tagle, J. A.; Pospieszczyk, A.

338

On factors controlling activity of submonolayer bimetallic catalysts: Nitrogen desorption  

NASA Astrophysics Data System (ADS)

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

Guo, Wei; Vlachos, Dionisios G.

2014-01-01

339

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

PubMed

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

Guo, Wei; Vlachos, Dionisios G

2014-01-01

340

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

NASA Technical Reports Server (NTRS)

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

Meitner, P. L.

1978-01-01

341

Thermal desorption study of physical forces at the PTFE surface  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

342

Thermal desorption study of physical forces at the PTFE surface  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

343

Temperature  

NSDL National Science Digital Library

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

Luis Miguel Orta Rial (None;)

2008-03-24

344

The role of temperature program and catalytic system on the quality of acrylonitrile-butadiene-styrene degradation oil  

Microsoft Academic Search

Thermal and catalytic degradation of acrylonitrile-butadien-styrene copolymer (ABS) was performed at 450°C by semi-batch operation. Four different temperature programs were used for thermal degradation. SA4 silica alumina and three SA4\\/iron oxide combinations (?-Fe2O3, a Fe3O4-C composite and ?-FeOOH) were used for catalytic degradation. The heating rate affects the quality of the degradation oil, the following heating program giving the lowest

Mihai Brebu; M Azhar Uddin; Akinori Muto; Yusaku Sakata; Cornelia Vasile

2002-01-01

345

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

SciTech Connect

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

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

1989-03-01

346

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

347

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

SciTech Connect

Evolution of volatile chlorine species during coal pyrolysis has been studied using a new temperature-programmed heating and gas-combustion technique. The pyrolysis apparatus consists of a pyrolysis chamber and an adjoining combustion chamber. Samples of coal are heated from ambient temperature to 800 C at a rate of 20 C/min in the pyrolysis chamber under a nitrogen atmosphere. The volatile products are carried with the nitrogen flow to the combustion chamber which is maintained at 850 C under a constant flow of oxygen. The gases flowing into the second chamber from the pyrolysis chamber are combusted. The combustion gases emitted are sampled through a capillary tube and analyzed with a quadrupole gas analyzer (QGA). Samples of Illinois high- and medium-chlorine coal were tested in the apparatus. For all these coals, HCl was the only chlorine species identified by the QGA. The combustion gases evolved from the coals were collected in a sodium carbonate solution and the chloride content was monitored by a potentiometric technique using a chloride ion-selective electrode. The chloride collected in the solution accounted for the total chlorine in the starting materials within the margins of analytical error. The HCl release profiles for the coals showed a broad peak between 250 C and 600 C with a maximum at 445 C. Neutron activation analysis for Na and Cl in the pyrolysis residues showed that 98% of chlorine in coal is volatilized as HCl during pyrolysis to 800 C and all the sodium is retained in the chars. Thus, it may be inferred that the chlorine in Illinois coals is released rapidly as HCl during combustion in a utility/industrial boiler, not as sodium chloride.

Chou, C.L.; Hackley, K.C.; Donnals, G.L.; Cao, J.; Ruch, R.R. (Illinois State Geological Survey, Champaign, IL (United States))

1992-01-01

348

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

349

Dispersion and surface states of copper catalysts by temperature-programmed-reduction of oxidized surfaces (s-TPR)  

Microsoft Academic Search

Surface and sub-surface oxidation of dispersed copper phase by N2O adsorptive decomposition at controlled temperature followed by H2 temperature-programmed-reduction of the Cu2O surface layers formed (s-TPR) was performed on siliceous supported catalysts (ca. 6wt.% Cu). The combined analysis permitted to measure the copper dispersion and to identify different surface copper species. Copper dispersion parameters were calculated from the H2-uptakes in

Antonella Gervasini; Simona Bennici

2005-01-01

350

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

PubMed

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

Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

2013-11-19

351

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

352

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

353

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

354

Computer Programs in Sweden for Calculation of Indoor Temperatures, Heating and Cooling Loads and Energy Consumptions of Buildings.  

National Technical Information Service (NTIS)

Computer programs are used in order to calculate indoor temperatures, heating and cooling loads, as well as the energy consumption of rooms and buildings. The accuracy of such calculations depends on how elaborate the simulation of the room or the buildin...

B. Adamson K. Kaellblad

1975-01-01

355

Kinetics of temperature programmed reduction of Fe 3 O 4 promoted with copper: application of iso-conversional methods  

Microsoft Academic Search

The temperature-programmed reduction of Cu\\/Fe3O4 in hydrogen was analyzed. The values of the apparent activation energy characteristic of this process were determined using the most widely known iso-conversional methods. In all cases a variation of the apparent activation energy with the degree of reduction was shown.

G. Munteanu; P. Budrugeac; L. Ilieva; T. Tabakova; D. Andreeva; E. Segal

2003-01-01

356

Gas absorption/desorption temperature-differential engine  

NASA Technical Reports Server (NTRS)

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

Miller, C. G.

1981-01-01

357

Prediction of retention times of polycyclic aromatic hydrocarbons and n-alkanes in temperature-programmed gas chromatography.  

PubMed

We have developed an iterative procedure for predicting the retention times of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes during separations by temperature-programmed gas chromatography. The procedure is based on estimates of two thermodynamic properties for each analyte (the differences in enthalpy and entropy associated with movements between the stationary and mobile phases) derived from data acquired experimentally in separations under isothermal conditions at temperatures spanning the range covered by the temperature programs in ten-degree increments. The columns used for this purpose were capillary columns containing polydimethylsiloxane-based stationary phases with three degrees of phenyl substitution (0%, 5%, and 50%). Predicted values were mostly within 1% of experimentally determined values, implying that the method is stable and precise. PMID:17851653

Aldaeus, Fredrik; Thewalim, Yasar; Colmsjö, Anders

2007-10-01

358

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

PubMed

This article presents case studies involving the use of thermal desorption gas chromatography-mass spectrometry to compositionally characterize pharmaceutical packaging materials for potential extractables. Knowledge of potential extractables and leachables early in the product development program allows the project team to make informed decisions, potentially minimizing redevelopment efforts and reducing cost. Case studies include selection of a label for use on a polyethylene bottle, selection of a drug contact surface of a blister packaging system, and selection of a stopper. PMID:20088248

Zweiben, Cindy; Shaw, Arthur J

2009-01-01

359

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

360

Desorption kinetics of small n-alkanes from magnesium oxide(100), platinum(111), and carbon(0001)/platinum(111) and studies of palladium nanoparticles: Growth and sintering on aluminum oxide(0001) and methane dissociation on magnesium oxide(100)  

NASA Astrophysics Data System (ADS)

Small alkane interactions with surfaces are of interest for a wide range of applications including catalysis, atmospheric chemistry, geochemistry and chemical sensing. We have investigated in fundamental detail the chemical physics underlying relevant elementary steps for heterogeneous catalysis by studying model surfaces that are well defined yet present the same local structure as on real industrial catalysts. We measured alkane desorption energy on MgO(100), Pt(111), and C(0001)/Pt(111) surfaces. The molecules, CNH2 N+2 (N = 1--4, 6, 8, 10), were each studied by temperature programmed desorption (TPD) over a range of initial coverages and heating rates. We developed a novel TPD analysis technique which allows for accurate determination of prefactors and coverage-dependent desorption energies. The prefactor for desorption was found to increase by several orders of magnitude with chain length. This increase can be physically justified by considering the increase in rotational entropy available to the molecules in the gas-like transition state for desorption. The desorption energy from each surface increased linearly with chain length with a small y-intercept. We also measured the dissociative sticking probability of methane on MgO-supported Pd nanoparticles and on Pd(111). On Pd(111), the sticking exhibits "normal energy scaling." We show that the Pd nanoparticle (˜3 nm wide) geometry must be decoupled from the measured sticking probabilities in order to compare the intrinsic reactivity of the Pd particles with Pd(111). We find that the sticking probability on ˜3 nm Pd particle surfaces is at most twice as large as on Pd(111). We have also examined the growth and sintering kinetics of Pd nanoparticles on alpha-Al2O3(0001) by non-contact atomic force microscopy and low-energy ion scattering spectroscopy. This is the first study of metal nanoparticles on a well-defined oxide surface where both of these techniques are used for characterization. The Pd grows initially as 2D islands at 300 K, with the transition to 3D particle growth at 0.25 monolayers. Upon heating at 1 K/s, the Pd particles (˜2.5 nm diameter for 0.8 monolayers at 300 K) sinters at a nearly constant rate, doubling in particle diameter by ˜1000 K.

Tait, Steven L., Jr.

361

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

NASA Astrophysics Data System (ADS)

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

Buendía, G. M.; Rikvold, P. A.

2013-07-01

362

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

363

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

PubMed

We present results of kinetic Monte Carlo simulations of a modified Ziff-Gulari-Barshad model for the reaction CO+O ? CO(2) on a catalytic surface. Our model includes impurities in the gas phase, CO desorption, and a modification known to eliminate the unphysical O poisoned phase. The impurities can adsorb and desorb on the surface, but otherwise remain inert. In a previous work that did not include CO desorption [Buendía and Rikvold, Phys. Rev. E 85, 031143 (2012)], we found that the impurities have very distinctive effects on the phase diagram and greatly diminish the reactivity of the system. If the impurities do not desorb, once the system reaches a stationary state, the CO(2) production disappears. When the impurities are allowed to desorb, there are regions where the CO(2) reaction window reappears, although greatly reduced. Following experimental evidence that indicates that temperature effects are crucial in many catalytic processes, here we further analyze these effects by including a CO desorption rate. We find that the CO desorption has the effect to smooth the transition between the reactive and the CO rich phase, and most importantly it can counteract the negative effects of the presence of impurities by widening the reactive window such that now the system remains catalytically active in the whole range of CO pressures. PMID:23944439

Buendía, G M; Rikvold, P A

2013-07-01

364

Ultraclean radioisotope marking by nuclear stimulated desorption  

SciTech Connect

A method for ultraclean radioactive marking is presented, utilizing the process of nuclear stimulated desorption. It employs a sequence of two slow radioactive decays. The primary decay causes a nucleus to desorb from a substrate onto which it had been placed. The desorbing daughter nuclei, being themselves radioactive, then constitute an ultraclean marking flux. A manifestation of this mechanism for the special case of the {sup 47}Ca{r arrow}{sup 47}Sc{r arrow}{sup 47}Ti decay is described. An application to end-point detection in wet etching is presented and quantitatively simulated.

Kelson, I.; Nir, D.; Zidon, A. (School of Physics and Astronomy, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv (Israel)); Dumont, H.; Perraillon, B. (CEN Saclay, 91191 Gif-sur-Yvette Cedex, (France)); Haustein, P. (Department of Chemistry, Brookhaven National Laboratory, Upton, Long Island, NY (USA))

1991-02-01

365

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

366

Sequential competitive sorption and desorption of chlorophenols in organoclay  

Microsoft Academic Search

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

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

2006-01-01

367

High-Temperature Materials Program Quarterly Progress Report for Period Ending January 31, 1965.  

National Technical Information Service (NTIS)

This report is divided into five sections: high-temperature materials development, materials compatibility studies, behavior of high-temperature materials under irradiation, uranium nitride, and tungsten metallurgy. (ERA citation 10:016519)

W. C. Thurber

1965-01-01

368

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

SciTech Connect

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

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

1993-08-01

369

A thermal desorption study of the kinetics of uranium hydride decomposition  

NASA Astrophysics Data System (ADS)

The decomposition of uranium hydride powder was studied using thermal desorption spectroscopy (TDS). In the TDS spectra, three distinct decomposition peaks were observed. However, only the high temperature peak was associated with an activation energy, calculated to be 43 kJ/mol H. This activation energy was used to construct outgassing diagrams that can be used to estimate the temperature and time dependence of UH3 decomposition. Potential models for explaining the three decomposition peaks and, thus, the decomposition mechanism are also presented and compared with H desorption energies calculated from first principles. Additional experiments on ?-U coupons containing UH3 corrosion pits were also performed. In those samples in excess of 6 peaks are observed. It is shown that the first three hydrogen peaks are related to the decomposition of UH3.

Lillard, R. S.; Taylor, C. D.; Wermer, J. R.; Mara, N. A.; Cooley, J. C.

2014-01-01

370

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

PubMed

Recycling of cellulases is an effective way to reduce the cost of enzymatic hydrolysis for the production of cellulosic ethanol. In this study, we examined the adsorption and desorption behaviors of cellulase at different pH values and temperatures. Furthermore, we developed a promising way to recover both free and bound cellulases by pH-triggered adsorption-desorption. The results show that acidic pH (e.g., pH 4.8) was found to favor adsorption, whereas alkaline pH (e.g., pH 10) and low temperature (4-37 °C) favored desorption. The adsorption of cellulases reached an equilibrium within 60 min at pH 4.8 and 25 °C, leading to approximately 50 % of the added cellulases bound to the substrate. By controlling the pH of eluent (citrate buffer, 25 °C), we were able to increase the desorption efficiency of bound cellulases from 15 % at pH 4.8 to 85 % at pH 10. To recover cellulases after enzymatic hydrolysis, we employed adsorption by fresh substrate and desorption at pH 10 to recover the free cellulases in supernatant and the bound cellulases in residue, respectively. The recycling performance (based on the glucose yield) of this simple strategy could reach near 80 %. Our results provided a simple, low-cost, and effective approach for cellulase recycling during the enzymatic hydrolysis of lignocellulosic biomass. PMID:24752845

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

2014-06-01

371

The influence of the surface electric field on water ionization: a two step dissociative ionization and desorption mechanism for water ion cluster emission from a platinum field emitter tip  

Microsoft Academic Search

Water ionization and desorption of protonated water clusters in high electric fields were studied on a Pt emitter tip in ultrahigh vacuum. Ramped field desorption (RFD) experiments were carried out at 109 and 145 K. As the tip potential was linearly ramped, crystalline ice adsorbed at low temperatures (145 K) was ionized and emitted from the tip as protonated water

Christopher J. Rothfuss; Valentin K. Medvedev; Eric M. Stuve

2003-01-01

372

Desorption of the NEG-coated Aluminum Chamber  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

373

Aluminum and iron surface modification by deuterium ion implantation and thermal desorption process  

Microsoft Academic Search

Fe and Al thin films were implanted at room temperature with 20 keV D2 ions at 3×1016 ions\\/cm2 fluence. The correlation between the effusion of the implanted deuterium and the evolution of the surface morphology was studied by thermal desorption spectroscopy (TDS) and scanning electron microscopy (SEM). Deuterium effusion from Fe thin films occurs at ?430 K and is controlled

R. Checchetto; L. M. Gratton; A. Miotello

2002-01-01

374

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

375

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

376

Low-temperature activity of Au\\/CeO 2 for water gas shift reaction, and characterization by ADF-STEM, temperature-programmed reaction, and pulse reaction  

Microsoft Academic Search

In Au\\/CeO2 catalysts prepared by the deposition–precipitation method, many Au particles smaller than 3nm in diameter were clearly observed by annular dark field scanning transmission electron microscopy (ADF-STEM). The water gas shift activity of Au\\/CeO2 was compared with that of Pt\\/CeO2, Au\\/TiO2, and Cu\\/ZnO\\/Al2O3 by using temperature-programmed reaction (TPRe) measurement in a stream of a reaction gas mixture composed of

H. Sakurai; T. Akita; S. Tsubota; M. Kiuchi; M. Haruta

2005-01-01

377

Electrospun nanofibers as substrates for surface-assisted laser desorption/ionization and matrix-enhanced surface-assisted laser desorption/ionization mass spectrometry.  

PubMed

Electrospun polymeric nanofibers (polyacrylonitrile, poly(vinyl alcohol), and SU-8 photoresist) and carbon nanofibers pyrolyzed to final temperatures of 600, 800, and 900 °C were used as substrates for surface-assisted laser desorption/ionization (SALDI) and matrix-enhanced surface-assisted laser desorption/ionization (ME-SALDI) analyses. Sample preparation of polymeric analytes using the electrospun target plate for SALDI analysis is simple and fast. Signal enhancements for poly(ethylene glycol) were noted with nanofibrous carbon substrates compared to those obtained with commercially available stainless steel plates when no organic matrix is used. Minimal fragmentation was observed. Poly(ethylene glycol) with a molecular weight as high as 900?000 Da was successfully detected using the carbon nanofibrous substrate processed to 800 °C, which is the highest molecular weight that has been studied by SALDI. Small molecules were detected using nanofibrous carbon substrate processed to 800 °C. For example, spectra of glucose, arginine, and crystal violet were obtained with no observed interferences in the low molecular weight range. The SALDI results show enhanced shot-to-shot reproducibility compared to matrix-assisted laser desorption/ionization (MALDI). High-quality polystyrene spectra were obtained for the first time using SALDI nanofibrous polyacrylonitrile substrates. Significantly enhanced signal-to-noise ratios were obtained using ME-SALDI compared to conventional MALDI or SALDI for the studied analytes. A detection limit of 400 amol was achieved for angiotensin I using the nanofibrous carbon ME-SALDI substrate. PMID:23537004

Lu, Tian; Olesik, Susan V

2013-05-01

378

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

Microsoft Academic Search

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

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

1971-01-01

379

Temperature-programmed reduction of calcined chromia-coated alumina and silica catalysts: probing chromium (VI)-oxygen species  

Microsoft Academic Search

Chromia-coated alumina and silica, containing 0.5, 5 and 10 wt%Cr2O3, have been prepared by adding Cr(NO3)3 solution to a suspension of the support in NH4OH followed by calcination at 600°C. Temperature-programmed reduction (TPR) of a corresponding unsupported chromia showed peaks at 370 and 490°C, due to reduction of surface chromate groups; commercial ?-Cr2O3 showed no hydrogen uptake. TPR measurements on

Mohamed I. Zaki; Nasr E. Fouad; Geoffrey C. Bond; Saad F. Tahir

1996-01-01

380

Effect of palladium and nickel on the temperature programmed reduction of metal oxides and metal oxide layers  

Microsoft Academic Search

A new binary oxide support was suggested as being useful in many commercial reactions. Our study was focused on the reduction\\u000a effect of metal oxide layer on alumina during reaction. Hence temperature programmed reduction of both bulk metal oxide and\\u000a metal oxide layer on alumina was studied first and the effect of palladium and nickel on the reduction of the

Jong Pal Kim

2004-01-01

381

Identification of Pd 3+ ions in zeolite L by temperature programmed reduction and electron paramagnetic resonance spectroscopy  

Microsoft Academic Search

Pd supported on KL zeolite has been studied by temperature programmed reduction (TPR) and electron paramagnetic resonance (EPR) spectroscopy. It has been found that upon calcination in pure oxygen Pd3+ and Pd2+ ions are formed; the Pd3+ ions are identified by their EPR signal. As Pd3+ ions in the cancrinite cages are difficult to reduce, the H2 consumption in conventional

Sanjay N. Gandhi; Guan-Dao Lei; Wolfgang M. H. Sachtler

1993-01-01

382

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

Microsoft Academic Search

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

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

1981-01-01

383

Study of the reducibility of copper in CuO?ZnO catalysts by temperature-programmed reduction  

Microsoft Academic Search

Temperature-programmed reduction (TPR) has been used in this work to study the reduction of copper in CuO?ZnO catalysts with different CuZn atomic ratios using H2 as reducing agent. In all catalysts, CuO was completely reduced to metal. The influence exerted by ZnO on the reduction of copper was evaluated for a wide range of composition and a scale of reducibility

G. Fierro; M. Lo Jacono; M. Inversi; P. Porta; F. Cioci; R. Lavecchia

1996-01-01

384

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

Microsoft Academic Search

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

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

1993-01-01

385

Temperature-Programmed Reduction and XRD Studies of Ammonia-Treated Molybdenum Oxide and Its Activity for Carbazole Hydrodenitrogenation  

Microsoft Academic Search

The change structure and composition of molybdenum nitride catalysts with cooling in a stream of ammonia or helium gas after NH3 treating was determined using temperature-programmed reduction (TPR) and X-ray powder diffraction analyses. The relationship between the molybdenum species and the catalytic activities of the molybdenum nitride catalysts for the hydrodenitrogenation (HDN) of carbazole was discussed. MoO2, ?-Mo2N, and Mo

M. Nagai; Y. Goto; A. Miyata; M. Kiyoshi; K. Hada; K. Oshikawa; S. Omi

1999-01-01

386

Temperature-programmed oxidation of ethane and ethylene in the presence and absence of {sup 13}C labeled methane  

SciTech Connect

The objective of this project is to perform short- and long-term studies to identify new concepts and technological barriers for the development of a process to convert natural gas to liquid fuels. Temperature-programmed oxidation of ethane and ethylene in the presence and absence of {sup 13}C labeled methane was conducted to determine the relative reactivity of ethane and ethylene compared to methane.

Shamsi, A.

1992-07-01

387

Electronic structure of sodium nitrate: Investigations of laser desorption mechanisms  

Microsoft Academic Search

This theoretical study uses ab initio quantum mechanical methods to investigate the electronic properties of ground and excited state sodium nitrate. We calculated electronic properties of the crystalline material for bulk, clean, and defected surfaces. The results of these calculations are used to explain the photoexcitation\\/desorption mechanism and support the conclusions of an earlier experimental investigation of the laser desorption

Maureen I. McCarthy; Kirk A. Peterson; Wayne P. Hess

1996-01-01

388

Desorption of pentachlorophenol from soils using mixed solvents  

SciTech Connect

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

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

1999-12-15

389

Laser desorption mass spectrometry for DNA analysis and sequencing.  

National Technical Information Service (NTIS)

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

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

1995-01-01

390

Cooperative desorption of CO and alkali atoms from metal surfaces  

NASA Astrophysics Data System (ADS)

Thermal desorption of CO and alkali atoms coadsorbed on metal surfaces is studied by using the lattice gas model incorporating the mutual interaction between the two adspecies. Calculated thermal desorption spectra show that both adspecies desorb cooperatively in almost simultaneous bursts when the mutual interaction is sufficiently attractive.

Ishi, Shin-Ichi; Asada, Hiromu; Ohno, Yuichi

1986-05-01

391

Cooperative desorption of CO and alkali atoms from metal surfaces  

NASA Astrophysics Data System (ADS)

Thermal desorption of CO and alkali atoms coadsorbed on metal surfaces is studied by using the lattice gas model incorporating the mutual interaction between the two adspecies. Calculated thermal desorption spectra show that both adspecies desorb cooperatively in almost simultaneous bursts when the mutual interaction is sufficiently attractive.

Ishi, Shin-Ichi; Asada, Hiromu; Ohno, Yuichi

392

Kinetics of soil cadmium desorption under simulated acid rain  

Microsoft Academic Search

Soil acidification can result in the release of heavy metals stabilized by soil components into soil solution, and therefore it causes ecological risk. The kinetics of Cd desorption from two Chinese soils (ultisol and oxisol) distributed in the acid rain sensitive areas of southern China, were studied using a flow-stirred method under simulated acid rain conditions. Cd desorption was well

Dai-Zhang Wang; Xin Jiang; Wei Rao; Ji-Zheng He

2009-01-01

393

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 ...

394

Desorption by ultrasound: Phenol on activated carbon and polymeric resin  

Microsoft Academic Search

An experimental feasibility study of using ultrasound to accomplish the difficult desorption of phenol from activated carbon and polymeric resin adsorbents is discussed. The desorption rates of activated carbon were found to significantly increase by ultrasound at 40 kHz and 1.44 MHz. Attrition of the activated carbon due to cavitation could be prevented by operating at a higher frequency and

Salil U. Rege; Ralph T. Yang; Charles A. Cain

1998-01-01

395

Modelling the effect of salinity on radium desorption from sediments  

Microsoft Academic Search

The desorption of the four naturally occurring radium isotopes 223 Ra, 224 Ra, 226 Ra, and 228 Ra from estuarine sediments is investigated. These isotopes are created within sediments by the radioactive decay of insoluble thorium parents. Due to competition from other ions for the occupation of adsorption sites on the sediment grains, radium desorption is a function of salinity.

Ian T. Webster; Gary J. Hancock; Andrew S. Murray

1995-01-01

396

Slow desorption of halogenated aliphatic hydrocarbons in soils  

Microsoft Academic Search

The sorption of organic compounds to soils and sediments retards their transport, microbial transformation, and certain abiotic chemical reactions. Sorption is normally modeled as a rapid equilibrium. However, several studies have shown that adsorption\\/desorption can be quite slow for some fraction of sorbed compound. Transport or degradation of this fraction can be limited by desorption. An extreme example of this

Pignatello

1988-01-01

397

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

398

Modeling Organic Contaminant Desorption from Municipal Solid Waste Components  

NASA Astrophysics Data System (ADS)

Approximately 25% of the sites on the National Priority List (NPL) of Superfund are municipal landfills that accepted hazardous waste. Unlined landfills typically result in groundwater contamination, and priority pollutants such as alkylbenzenes are often present. To select cost-effective risk management alternatives, better information on factors controlling the fate of hydrophobic organic contaminants (HOCs) in landfills is required. The objectives of this study were (1) to investigate the effects of HOC aging time, anaerobic sorbent decomposition, and leachate composition on HOC desorption rates, and (2) to simulate HOC desorption rates from polymers and biopolymer composites with suitable diffusion models. Experiments were conducted with individual components of municipal solid waste (MSW) including polyvinyl chloride (PVC), high-density polyethylene (HDPE), newsprint, office paper, and model food and yard waste (rabbit food). Each of the biopolymer composites (office paper, newsprint, rabbit food) was tested in both fresh and anaerobically decomposed form. To determine the effects of aging on alkylbenzene desorption rates, batch desorption tests were performed after sorbents were exposed to toluene for 30 and 250 days in flame-sealed ampules. Desorption tests showed that alkylbenzene desorption rates varied greatly among MSW components (PVC slowest, fresh rabbit food and newsprint fastest). Furthermore, desorption rates decreased as aging time increased. A single-parameter polymer diffusion model successfully described PVC and HDPE desorption data, but it failed to simulate desorption rate data for biopolymer composites. For biopolymer composites, a three-parameter biphasic polymer diffusion model was employed, which successfully simulated both the initial rapid and the subsequent slow desorption of toluene. Toluene desorption rates from MSW mixtures were predicted for typical MSW compositions in the years 1960 and 1997. For the older MSW mixture, which had a low plastics content, the model predicted that 50% of the initially sorbed toluene desorbed over a period of 5.8 days. In contrast, the model predicted that 50% of the initially sorbed toluene desorbed over a period of 4 years for the newer MSW mixture. These results suggest that toluene desorption rates from old MSW mixtures exceed methanogenic toluene degradation rates (toluene half-lives of about 30 to 100 days have been reported for methanogenic systems) and thus imply that biodegradation kinetics control the rate at which sorbed toluene is mineralized in old landfills. For newer MSW mixtures with a larger plastics content, toluene desorption rates are substantially slower; therefore, toluene desorption kinetics likely control the rate at which sorbed toluene can be mineralized in new landfills.

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

2002-12-01

399

Include low-temperature boiler components in your powerplant life-extension program  

Microsoft Academic Search

The role of surveillance programs in extending boiler life for 25, 30, or more years is examined. Aside from evaluating hightemperature components such as superheaters and reheaters, lownace-wall tubes and the steam drum should also be evaluated. It is essential, the author says, that these components be included in a condition-assessment or life-extension program. Hydrogen produced in the corrosive reaction

G. H. Harth; M. R. Rechner

1985-01-01

400

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

PubMed

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

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

2010-02-14

401

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

Microsoft Academic Search

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

Li Yongju; Huang Yuqi; Li Boyuan; Dai Wenting

2011-01-01

402

Charge Assisted Laser Desorption/Ionization Mass Spectrometry of Droplets  

PubMed Central

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

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

2008-01-01

403

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

404

Program for the development of high temperature electrical materials and components  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

405

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

PubMed

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

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

1999-03-19

406

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

NASA Astrophysics Data System (ADS)

Nonresonant multiphoton ionization with time-of-flight mass spectrometry has been used to monitor the desorption of aluminum chloride (AlxCly) etch products from the Al(111) surface at 100 and 500 K during low-coverage (<5% monolayer) monoenergetic Cl2 (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 Cl2, 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 AlCl3. Cl2 sticking probability measurements and AlxCly etch rate measurements show etching even at Cl2 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 AlCl3 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.

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

2004-11-01

407

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

PubMed Central

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

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

2013-01-01

408

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

PubMed

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

Staymates, Matthew; Gillen, Greg

2012-07-01

409

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

410

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...

411

Temperature-programmed catalytic liquefaction of low rank coal using dispersed Mo catalyst.  

National Technical Information Service (NTIS)

In the presence of catalyst, the specific reaction conditions have a direct effect on conversion in coal liquefaction and on the product distribution. At temperatures lower than 300(degree)C, catalyst precursors such as ammonium tetrathiomolybdate may not...

L. Huang C. Song H. H. Schobert

1992-01-01

412

Photon stimulated desorption phenomena at the Taiwan Light Source vacuum system  

NASA Astrophysics Data System (ADS)

The photon stimulated desorption (PSD) by the synchrotron radiation irradiated from the Taiwan Light Source (TLS) vacuum chambers were analyzed. The desorption behavior of the various gas species were compared by either adjusting the electron beam orbit and hitting the photons on the fresh chamber walls or turning off the pumps. The dominated gases during the earlier years' operation are the H2, in concentration of > 90followed by other gases, e.g. CO, H2O, CH4, etc.. However, some of the massive gas species, e.g. CxHy, CxFy, were observed after replacing the new vacuum parts or unsuitable baking the O-ring gate valves in higher temperature. The contaminated gases are to be reduced by beam-self cleaning treatment. Planning in upgrading the storage ring vacuum system is also described.

Hsiung, G. Y.; Hsu, Y. J.; Chen, J. R.

1997-05-01

413

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.

2014-06-01

414

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

415

Isothermal desorption measurements of self-diffusion in supercooled o-terphenyl.  

PubMed

Isothermal desorption of o-terphenyl thin-film bilayers was used to measure self-diffusion coefficients of supercooled o-terphenyl near the glass transition temperature (Tg=243 K). Diffusion coefficients from 10(-15.5) to 10(-12) cm2 s(-1) were obtained between 246 and 265 K. Protio and deuterio o-terphenyl were sequentially vapor deposited, then annealed to simultaneously diffuse and desorb the sample in a vacuum chamber. During the desorption of the bilayer, the concentration of each isotope was detected by a mass spectrometer, which revealed the extent of interfacial broadening. In these experiments, isotopic interdiffusion is indistinguishable from self-diffusion and the measured interfacial broadening is consistent with Fickian diffusion. The samples prepared under several different deposition conditions yielded the same self-diffusion coefficients, indicating that the experiments were conducted in the equilibrium supercooled liquid state. PMID:16468904

Mapes, Marie K; Swallen, Stephen F; Kearns, Kenneth L; Ediger, M D

2006-02-01

416

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

NASA Astrophysics Data System (ADS)

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 × 1012 s-1 were determined for the desorption reaction of deuterium from diamond which is in agreement with previously reported studies.

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

2014-06-01

417

Adsorption and thermal desorption of the herbicide fluroxypyr on activated carbon fibers and cloth at different pH values.  

PubMed

Adsorption of fluroxypyr was studied at pH values between 2 and 10 and at temperatures of 298 and 313 K. Adsorption capacity decreased when the solution pH increased. This was explained by changes in fluroxypyr solubility and in dispersive and electrostatic adsorbent-adsorbate interactions with the increase in pH. The highest adsorption was found at pH 2, when the solubility was the lowest and only dispersive interactions operated. An increase in temperature produced a decrease in adsorption capacity. Thermal desorption of fluroxypyr up to 1073 K left a residue on the carbon surface, which increased with higher adsorption pH. Differential thermogravimetry (DTG) profiles showed two desorption peaks at pH values of 2 and 4 and only one peak at pH values of 7 and 10. The appearance of one or two peaks may be related to the type of adsorbate-adsorbent interactions established during adsorption. The predominance of electrostatic interactions favours the strongly bound or chemisorbed fluroxypyr. One important conclusion is that the highest amounts of fluroxypyr are adsorbed and thermally desorbed when there are only non-electrostatic interactions between fluroxypyr molecules and carbon surface. Activation desorption energy and pre-exponential factor were obtained from the shift in temperature of desorption peaks with higher heating rate. PMID:19012898

Pastrana-Martínez, L M; López-Ramón, M V; Moreno-Castilla, C

2009-03-01

418

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

419

Electron stimulated desorption of positive ions from alkali halide surfaces  

NASA Astrophysics Data System (ADS)

Electron stimulated desorption (ESD) of positive ions from LiF, LiBr and RbF is observed in the incident electron energy region below 800 eV. In ESD from LiF, the experimental results are mostly explained in terms of the Knotek-Feibelman (KF) mechanism. On the other hand the KF mechanism is not satisfactory to understand the desorption yield spectra from LiBr, because the threshold energy of desorption was not necessarily observed at binding energies of core levels of LiBr. Since the yield spectrum of Li + ions showed quite different profile from that of Br + ions in ESD from LiBr, it is possible that the desorption mechanism for cations is not the same as that for anions. In the case of ESD from RbF the enhancement of the desorption yields was observed at about 80 eV of the incident energy, which does not agree with any interband transition or ionization energy. We observed the desorption of Rb 2+ ions besides that of Rb + and F + ions, which are always associated with the desorption of H 2O + ions. The role of H 2O + ions is also discussed.

Yasue, Tsuneo; Ichimiya, Ayahiko; Ohtani, Shunsuke

1987-07-01

420

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

421

Studies of acidic sites on boralities by temperature-programmed desorption (TPD) of NH[sub 3], C[sub 2]H[sub 4], and 1-C[sub 4]H[sub 8  

SciTech Connect

The acidity of [Al]-ZSM-5 is considerably strong leading to isomerization, dimerization, cracking, and coking reactions that may take place concurrently. Fine-tuning the acidity of ZSM-5 by incorporating boron into the zeolite framework is a goal of this research. From the position of boron in the periodic table, it would be expected that the substitution of aluminum with boron in the framework of pentasil zeolites would weaken the acidic strength of the zeolites. Ammonia, 1-butene, and ethylene have been used as probe molecules to study the acidic sites of zeolites. These results show that three types of acidic sites are present on boron-containing zeolites, i.e., one inactive for reactions of 1-butene, another active for dimerization of 1-butene, and a final one responsible for isomerization of butene. Framework aluminum plays an important role in adsorption of butene or ethylene molecules on boron/aluminium ZSM-5. Butene or ethylene adsorption appears to be nonlinear with the number of acidic sites, and aluminum appears to activate the adsorption of butene or ethylene on boron acidic sites. 20 refs., 10 figs., 5 tabs.

Xu, Wen-Qing; Suib, S.L.; O'Young, Chi-Lin (Univ. of Connecticut, Storrs, CT (United States))

1993-11-01

422

Innovative site remediation technology: Thermal desorption. Volume 6  

SciTech Connect

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

Anderson, W.C.

1993-11-01

423

252-Californium plasma desorption mass spectrometry of glycerophospholipids.  

PubMed

252-Californium plasma desorption mass spectrometry was applied to the study of five different classes of phospholipids namely phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine and phosphatidylinositol. Positive and negative ion spectra were compared to spectra obtained using other ionization techniques. Plasma desorption mass spectra provide useful information on the molecular weight of compounds from all classes, particularly in the case of phosphatidylserine--a class that has failed to show satisfactory quasimolecular ions with either Fast atom bombardment, FAB or Field desorption, FD. The observed fragmentation is also indicative of the structure of the studied compounds. PMID:2955827

Demirev, P A

1987-05-01

424

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 extensometers.

Ellis, J. R.

1987-01-01

425

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

426

Include low-temperature boiler components in your powerplant life-extension program  

SciTech Connect

The role of surveillance programs in extending boiler life for 25, 30, or more years is examined. Aside from evaluating hightemperature components such as superheaters and reheaters, lownace-wall tubes and the steam drum should also be evaluated. It is essential, the author says, that these components be included in a condition-assessment or life-extension program. Hydrogen produced in the corrosive reaction between fluid and tube metal causes decarburizing of the tube from the inside. Ultrasonic detection is a suggested means to visually identify hydrogen damage from the outside of a tube unless it has been ruptured. If it has been ruptured, it is necessary to use non-destructive techniques for it's detection, such as a variation of the shearwave method. Steam-drum problems are discussed.

Harth, G.H.; Rechner, M.R.

1985-12-01

427

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

Microsoft Academic Search

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.

C. Jammes; P. Filliatre; B. Geslot; T. Domenech; S. Normand

2011-01-01

428

Feedback-enabled discrimination enhancement for temperature-programmed chemiresistive microsensors  

Microsoft Academic Search

Temperature cycling can be used to enrich signal streams in gas phase sensing, however drift that can occur when repeatedly applying such cycles can degrade target recognition over time. A method for correcting heater drift through operational feedback has been implemented specifically to examine the level of performance improvement introduced for a single microhotplate-based chemiresistive sensing element exposed to multiple

Phillip H. Rogers; Steve Semancik

2011-01-01

429

ISY Sea Surface Temperature Validation Test Program in Mutsu Bay (Japan).  

National Technical Information Service (NTIS)

An accuracy validation test project for the Sea Surface Temperature (SST) estimation by satellite data in Mutsu bay (Japan), undertaken as part of the International Space Year (ISY), is reported. The sea and air truth data are provided by the four observa...

R. Yokoyama S. Tanba T. Souma H. Maejima K. Maeda

1992-01-01

430

Computer program for the calculation of short-circuit temperature rise on optical ground wires  

Microsoft Academic Search

Optical ground wires (OPGW) are increasingly being used on overhead transmission lines throughout the world. OPGW conductors protect the power line against lightning or short-circuit and provide communication through optical fibres embedded inside the conductor. In case of conventional ground wire, the permissible instantaneous temperature is limited by the highest allowable loss of tensile strength of metallic materials caused by

L. Varga; O. Guntner; L. Pekanovics

1999-01-01

431

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

EPA Science Inventory

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

432

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

433

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

PubMed

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

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

2014-08-15

434

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

PubMed

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

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

2013-01-01

435

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

PubMed Central

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

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

2013-01-01

436

Characterization of nonstoichiometric nickel manganite spinels Ni x Mn 3? x ? 3 ?\\/4 O 4+ ? by temperature programmed reduction  

Microsoft Academic Search

Cation deficient spinels NixMn3?x?3?\\/4O4+? (0?x?1) have been prepared by thermal decomposition of mixed oxalates Nix\\/3Mn(3?x)\\/3(C2O4)·nH2O in air at 623 K. They have been characterised by temperature programmed reduction (TPR) under H2, the reaction being followed by gravimetric and powder X-ray diffraction measurements. It has been shown that TPR proceeds in several steps. The first steps correspond to the loss of

Christel Laberty; Jerzy Pielaszek; Pierre Alphonse; Abel Rousset

1998-01-01

437

Preliminary design of an alternate high-temperature turbine. A topical report for Phase II of the High-Temperature-Turbine Technology Program  

SciTech Connect

The feasibility of designing a convectively air-cooled turbine to operate in the environment of a 3000/sup 0/F combustor exit temperature with maximum turbine airfoil metal temperatures held to 1500/sup 0/F was established. The United Technologies-Kraftwerk Union V84.3 gas turbine design was used as the basic configuration for the design of the 3000/sup 0/F turbine. Turbine cooling requirements were determined based on the use of the modified V84.3 type silo combustor with a pattern factor of 0.1. The convective air-cooling technology levels in terms of cooling effectiveness required to satisfy the airfoil cooling requirements were identified. Cooling schemes and fabrication technologies required are discussed. Turbine airfoil cooling technology levels required for the 3000/sup 0/F engine were selected. The performance of the 3000/sup 0/F convectively air-cooled gas turbine in simple and combined cycle was calculated. The 3000/sup 0/F gas turbine combined-cycle system provides an increase in power of 61% and a decrease in heat rate of 10% compared to a similar system with a combustor exit temperature of 2210/sup 0/F and the same airflow. The development of a successful 3000/sup 0/F convectively air-cooled turbine can be accomplished with a reasonable design and fabrication development effort on the cooled turbine airfoils. Use of the convectively air-cooled turbine provides the transfer of technology from extensive aircraft engines developed programs and operating experience to industrial gas turbines. It eliminates the requirement for large investments in alternate cooling techniques tailored specifically for industrial engines which offer no additional benefits.

Strough, R.I.

1981-08-01

438

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

439

News on sputter theory: Molecular targets, nanoparticle desorption, rough surfaces  

NASA Astrophysics Data System (ADS)

Sputtering theory has existed as a mature and well-understood field of physics since the theory of collision-cascade sputtering has been developed in the late 1960s. In this presentation we outline several directions, in which the basic understanding of sputter phenomena has been challenged and new insight has been obtained recently. Sputtering of molecular solids: after ion impact on a molecular solid, not all of the impact energy is available for inducing sputtering. Part of the energy is converted into internal (rotational and vibrational) excitation of the target molecules, and part is used for molecule dissociation. Furthermore, exothermic or endothermic chemical reactions may further change the energy balance in the irradiated target. Nanoparticle desorption: usually, the flux of sputtered particles is dominated by monatomics; in the case of a pronounced spike contribution to sputtering, the contribution of clusters in the sputtered flux may become considerable. Here, we discuss the situation that nanoparticles were present on the surface, and outline mechanisms of how these may be d