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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 from LiAlO 2 treated with H 2  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption (TPD) measurements have been made of H 2O and H 2 desorption from LiAlO 2 treated at 923 K with He-H 2 mixtures containing 990, 495, and 247 vppm H 2. Desorptions were into sweep gases of pure He and into He-H 2 mixtures. The H 2O and H 2 desorption peaks were shown to be the sums of first order subpeaks which had reproducible desorption activation energy and pre-exponential terms. For H 2O desorption, the activation energies were 96, 117, and 134 kJ/mol (23, 28, and 32 kcal/mol). (Earlier work had identified an additional peak with an activation energy of 75 kJ/mol (18 kcal/mol.) Enhancement of desorption of H 2O by H 2 in the sweep gas was confirmed. The enhancement results not from modifying the activation energies and pre-exponential terms for the various sites but from changes in the populations of sites participating in the desorption process so that sites with lower activation energies are increasingly involved. For those runs with He as the sweep gas, desorption of H 2 could be observed. The subpeaks involved had activation energies within approximately 4 kJ/mol (1 kcal/mol) higher than the analogous peaks for H 2O desorption.

Fischer, Albert K.

1992-09-01

3

Analysis of molecular hydrogen formation on low-temperature surfaces in temperature programmed desorption experiments.  

PubMed

The study of the formation of molecular hydrogen on low-temperature surfaces is of interest both because it enables the exploration of elementary steps in the heterogeneous catalysis of a simple molecule and because of its applications in astrochemistry. Here, we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments, beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations, and the energy barriers of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results are used in order to evaluate the formation rate of H2 on dust grains under the actual conditions present in interstellar clouds. It is found that, under typical conditions in diffuse interstellar clouds, amorphous silicate grains are efficient catalysts of H2 formation when the grain temperatures are between 9 and 14 K. This temperature window is within the typical range of grain temperatures in diffuse clouds. It is thus concluded that amorphous silicates are good candidates to be efficient catalysts of H2 formation in diffuse clouds. PMID:17988107

Vidali, G; Pirronello, V; Li, L; Roser, J; Manicó, G; Congiu, E; Mehl, H; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

2007-12-13

4

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

E-print Network

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

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

2007-08-13

5

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

E-print Network

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

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

2007-01-01

6

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

7

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

8

Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)  

E-print Network

such as physisorption versus chemi- sorption and the orientation of water molecules in the first few monolayers deserveTemperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100 Abstract Thin water (D2O) films on MgO(100) surfaces have been studied. Water was deposited at 115 K

Reisler, Hanna

9

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

10

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

11

Temperature-Programmed Desorption Observation of Graphene-on-Silicon Process  

NASA Astrophysics Data System (ADS)

With its industrial adaptability, graphene-on-silicon (GOS), formed by ultrahigh-vacuum annealing of a SiC thin film on a silicon substrate, is attracting recent attention. Little is known, however, about the growth mechanism of GOS. We demonstrate in this paper that temperature-programmed-desorption spectroscopy of deuterium (D2-TPD) can be a powerful in-situ probe to investigate the surface chemistry during formation of epitaxial graphene (EG) on SiC crystals. Using the D2-TPD, the surface stoichiometry and the back-bonds of the surface atoms, including their dependence on the crystallographic orientations [Si(111), Si(100), and Si(110)] can be obtained. Difference in the growth mechanism of GOS among the orientations is discussed based on the results.

Abe, Shunsuke; Handa, Hiroyuki; Takahashi, Ryota; Imaizumi, Kei; Fukidome, Hirokazu; Suemitsu, Maki

2011-07-01

12

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

SciTech Connect

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

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

1986-07-03

13

Temperature programed desorption of C{sub 2}H{sub 4} from pure and graphite-covered Pt(111)  

SciTech Connect

Ethylene adsorption on Pt(111) at 95 K was studied by temperature programed desorption (TPD), low energy electron diffraction (LEED), and x-ray photoelectron spectroscopy. Ethylene desorbs reversibly at 112 K and irreversibly at 255 and 280 K. It is generally accepted that annealing of ethylene adsorbed on Pt(111) to 300 K results in a dehydrogenation to ethylidyne through an ethylidene intermediate. This was observed by a hydrogen desorption peak at 300 K. Also, hydrogenation of the adsorbed ethylene was observed by a small ethane desorption peak at 300 K. Upon heating to 700 K, the ethylidyne species will further dehydrogenate to carbidic carbon species with hydrogen desorption peaks at 460 and 640 K. If the carbidic species is heated to higher temperatures (up to 1000 K), it will further dehydrogenate and form graphitic islands which will accumulate by Ostwald ripening in larger islands at the step edges of the surface. After annealing the sample to 1000 K, a statistically distributed 8x8 superstructure of these graphite islands is achieved, as interpreted from A pattern in the LEED data. The TPD results indicate that ethylene adsorption on Pt(111) results in the formation of graphitic islands upon heating to 1000 K, contrary to previous conjectures of formation of a full graphite monolayer.

Vermang, B.; Juel, M.; Raaen, S. [Physics Department, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim (Norway)

2007-11-15

14

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

15

Adsorption and reaction of formic acid on NiO(lOO) films on Mo(l00): Temperature programmed desorption and high resolution electron  

E-print Network

Adsorption and reaction of formic acid on NiO(lOO) films on Mo(l00): Temperature programmed desorption and high resolution electron energy loss spectroscopy studies Charles M. Truong, Ming-Cheng Wu-3255 (Received 24 June 1992;accepted8 September1992) Adsorption and reaction of formic acid on well-defined Ni

Goodman, Wayne

16

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

PubMed

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

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

2014-01-01

17

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

18

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

SciTech Connect

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

Tewell, Craig R.

2002-08-19

19

Adsorption and decomposition of nickelocene on Ag(1 0 0): a high-resolution electron energy loss spectroscopy and temperature programmed desorption study  

NASA Astrophysics Data System (ADS)

Nickelocene adsorption and decomposition on the Ag(1 0 0) surface were studied with temperature programmed desorption and high resolution electron energy loss spectroscopy. At monolayer coverages on the relatively inert Ag(1 0 0) surface at 175 K, nickelocene physisorbs molecularly, with its molecular axis perpendicular to the surface plane. Nickelocene begins decomposing to adsorbed cyclopentadienyl and nickel at 225 K. Molecular desorption is only observed from multilayer material, at 210 K, or from the first monolayer if adjacent surface sites for decomposition are not available. The cyclopentadienyl decomposes through disproportionation to cyclopentadiene, which desorbs, and adsorbed nickel and carbon fragments on the Ag(1 0 0) surface with a maximum at 525 K.

Pugmire, D. L.; Woodbridge, C. M.; Boag, N. M.; Langell, M. A.

2001-02-01

20

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

E-print Network

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

Goodman, Wayne

21

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

22

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

23

Surface characterization of oxygen-functionalized multi-walled carbon nanotubes by high-resolution X-ray photoelectron spectroscopy and temperature-programmed desorption  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes were exposed either to nitric acid or to an oxygen plasma to synthesize oxygen-containing functional groups which were characterized by high-resolution X-ray photoelectron spectroscopy (XPS). The C 1s spectra revealed that the treatment with nitric acid mainly resulted in the formation of carboxylic (COOR) and phenolic (C sbnd OR) groups, whereas the plasma treatment led to a higher amount of carbonyl (C dbnd O) groups. Furthermore, the nitric acid treatment yielded a 60% higher surface oxygen concentration compared to the plasma treatment, and created a minor amount of nitrogen-containing functional groups. Thus, the nitric acid treatment was found to be more effective in creating acidic functional groups. The presence and the thermal stability of these groups was also investigated by temperature-programmed desorption (TPD). The release of carbon dioxide was detected at about 350 and 450 °C, indicating the decomposition of COOR groups. The C dbnd O groups were more stable decomposing even above 600 °C. In addition, ammonia was adsorbed as probe molecule followed by TPD to derive the amount and the acidity of the carboxylic and phenolic groups.

Xia, Wei; Wang, Yuemin; Bergsträßer, Ralf; Kundu, Shankhamala; Muhler, Martin

2007-10-01

24

NH{sub 3} adsorption and decomposition on Ir(110): A combined temperature programmed desorption and high resolution fast x-ray photoelectron spectroscopy study  

SciTech Connect

The adsorption and decomposition of NH{sub 3} on Ir(110) has been studied in the temperature range from 80 K to 700 K. By using high-energy resolution x-ray photoelectron spectroscopy it is possible to distinguish chemically different surface species. At low temperature a NH{sub 3} multilayer, which desorbs at {approx}110 K, was observed. The second layer of NH{sub 3} molecules desorbs around 140 K, in a separate desorption peak. Chemisorbed NH{sub 3} desorbs in steps from the surface and several desorption peaks are observed between 200 and 400 K. A part of the NH{sub 3ad} decomposes into NH{sub ad} between 225 and 300 K. NH{sub ad} decomposes into N{sub ad} between 400 K and 500 K and the hydrogen released in this process immediately desorbs. N{sub 2} desorption takes place between 500 and 700 K via N{sub ad} combination. The steady state decomposition reaction of NH{sub 3} starts at 500 K. The maximum reaction rate is observed between 540 K and 610 K. A model is presented to explain the occurrence of a maximum in the reaction rate. Hydrogenation of N{sub ad} below 400 K results in NH{sub ad}. No NH{sub 2ad} or NH{sub 3ad}/NH{sub 3} were observed. The hydrogenation of NH{sub ad} only takes place above 400 K. On the basis of the experimental findings an energy scheme is presented to account for the observations.

Weststrate, C.J.; Bakker, J.W.; Rienks, E.D.L.; Lizzit, S.; Petaccia, L.; Baraldi, A.; Vinod, C.P.; Nieuwenhuys, B.E. [Leids Instituut voor Chemisch Onderzoek, Universiteit Leiden, P.O. Box 9502, Einsteinweg 55, 2333 CC Leiden (Netherlands); Sincrotrone Trieste, Strada Statale 14 km 163.5, I-34012 Basovizza (Italy); Physics Department and Center of Excellence for Nanostructured Materials, Trieste University, Via Valerio 2, I-34127 Trieste (Italy); Laboratorio TASC-INFM, Strada Statale 14 Km 163.5, I-34012 Trieste (Italy); Leids Instituut voor Chemisch Onderzoek, Universiteit Leiden, P.O. Box 9502, Einsteinweg 55, 2333 CC Leiden (Netherlands); Schuit Institute of Catalysis, Technische Universiteit Eindhoven, P.O. Box 5600 MB, Eindhoven (Netherlands)

2005-05-08

25

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

SciTech Connect

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

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

2009-09-15

26

Desorption isotherms and glass transition temperature for chicken meat  

Microsoft Academic Search

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

Adriana E Delgado; Da-Wen Sun

2002-01-01

27

Reproducibility of Temperature-Selected Mass Spectra in Matrix-Assisted Laser Desorption Ionization of Peptides  

E-print Network

desorption ionization (MALDI)1-4 combined with time-of-flight (TOF) mass spectrometry is one of the mostReproducibility of Temperature-Selected Mass Spectra in Matrix- Assisted Laser Desorption experiment, a set of mass spectra was collected by repetitive irradiation of a spot on a sample. Even though

Kim, Myung Soo

28

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...

29

Catalytic reduction of CO with hydrogen sulfide. 3. Study of adsorption of O/sub 2/, CO, and CO coadsorbed with H/sub 2/S on anatase and rutile using Auger electron spectroscopy and temperature-programmed desorption  

SciTech Connect

In O/sub 2/ and CO adsorption on anatase, only one weakly bound molecular desorption state was observed. For CO on rutile, there was a strongly bound and a weakly bound state. For O/sub 2/ rutile, a weakly bound state and two strongly chemisorbed states were observed. These strongly bound states are associated with the surface lattice anion vacancies produced on rutile (110). The amount of chemisorption in one of the strongly bound oxygen desorption states is correlated with the initial rate of irreversible adsorption of H/sub 2/S on rutile. Coadsorption of CO and H/sub 2/S indicates that strongly chemisorbed CO interacts with strongly chemisorbed H/sub 2/S to yield intermediates which desorb as CH/sub 3/SH and CH/sub 4/ at T approx. 800 K. At higher temperatures the surface sulfide concentration dominates the -SH concentration, explaining the dominance of COS in the product mixture. Implications of commercial hydrodesulfurization catalysts are discussed.

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

1986-07-03

30

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

SciTech Connect

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

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

2008-09-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

32

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

SciTech Connect

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

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

2002-12-01

33

Evaluation of minimum desorption temperatures of thermal compressors in adsorption refrigeration cycles  

Microsoft Academic Search

The purpose of this paper is to identify the minimum desorption temperatures required to operate thermally driven adsorption beds of a solid sorption refrigeration system. The method is based on the evaluation of uptake efficiency of the adsorption bed and estimating there from conditions under which the compressor ceases to provide any throughput. The difference in the densities of the

B. B. Saha; I. I. El-Sharkawy; A. Chakraborty; S. Koyama; N. D. Banker; P. Dutta; M. Prasad; K. Srinivasan

2006-01-01

34

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. ...

35

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. ...

36

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

SciTech Connect

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

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

2013-01-01

37

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

PubMed

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

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

2003-06-15

38

Journal of Low Temperature Physics, Vol.111,Nos. 3/4, 1998 Desorption of Solid O2 Induced by Vibrational  

E-print Network

simple molecular material, low temperature, solid oxygen, used here as an analog matrix material. We viewJournal of Low Temperature Physics, Vol.111,Nos. 3/4, 1998 Desorption of Solid O2 Induced densities, guest molecules dissolved in the lattice were carried off by the matrix material. The evolution

Johnson, Robert E.

39

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.

40

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

EPA Science Inventory

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

41

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

NASA Astrophysics Data System (ADS)

The preparation of InSb (001) oxygen-free surfaces by thermal annealing at relatively low temperatures under molecular hydrogen flow is reported. This process is compared with thermal oxide desorption (TOD) at 400°C under ultrahigh vacuum conditions. Molecular hydrogen cleaning (MHC) at substrate temperature of 250°C and at hydrogen pressure of 5×10-6Torr resulted in complete desorption of the native oxide layer. Furthermore, no carbon contamination was observed on the surface following this treatment. The surface morphology of the samples following this process was found to be very smooth without any droplet structure. The In:Sb surface stoichiometry was nearly 1:1 along the MHC process. In addition, annealing the sample at 400°C in vacuum after oxide removal by MHC maintains the smoothness and the stoichiometry of the surface. In contrast, TOD at 400°C of an oxidized InSb surface in vacuum does not result in complete oxide removal from the surface. Furthermore, small droplets associated with In are produced at this annealing temperature. The surface stoichiometry shows In enrichment after TOD in vacuum above 360°C. The surface composition and chemical bonding were monitored by Auger electron spectroscopy and x-ray photoelectron spectroscopy as a function of process parameters. The surface morphology was analyzed by atomic force microscopy.

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

2007-01-01

42

Evaluation of steam as a sweep gas in low temperature thermal desorption processes used for contaminated soil clean up  

SciTech Connect

The purpose of this investigation was to compare the effectiveness of steam as a sweep gas in the low temperature thermal desorption (LTTD) process. The intent is to determine if steam may be substituted for nitrogen, which is the sweep gas of choice for many thermal desorption processes. Steam has several advantages over nitrogen. Among those advantages is lower cost and the availability of on-site generation facilities. The study was conducted by placing a stainless steel tube containing a predetermined amount of contaminated soil in an electrical furnace. The tube had openings at each end. One end of the tube was connected to the source of the sweep gas with the other end being connected to a ice bath condenser. The effectiveness of steam and nitrogen were compared as sweep gases at similar operating conditions. The contaminants of interest in this study were: volatile compounds, p-xylene (Normal Boiling Point (NBP), 138 C), trichloroethylene--TCE (NBP, 86.9 C), and a semi-volatile compound, phenanthrene (NBP, 340 C). Sweep gas flow rate was varied over a range that would be expected in a commercial size LTTD unit. The sweep gas efficiency was evaluated over a series of exposure times and three temperatures of 177, 232, and 288 C. The residual concentration of the contaminant was determined by gas chromatographic analysis. Rates of contaminant desorption were determined as a function of time, sweep gas volume, and specific contaminant. The data generated allowed a general comparison of nitrogen and steam as seep gases. In most cases tested, the treatments using steam as the sweep gas exhibited characteristics that were comparable to or better than nitrogen sweep gas treatments. The advantage of steam was more pronounced with the higher boiling point semi-volatile compound phenanthrene.

George, C.E.; Azwell, D.E.; Adams, P.A.; Rao, G.V.N. [Mississippi State Univ., MS (United States). Dept. of Chemical Engineering] [Mississippi State Univ., MS (United States). Dept. of Chemical Engineering; Averett, D.E. [Army Corps of Engineers, Vicksburg, MS (United States). Waterways Experiment Station] [Army Corps of Engineers, Vicksburg, MS (United States). Waterways Experiment Station

1995-12-31

43

Thermal desorption spectroscopy from the surfaces of metal-oxide-semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

An experimental setup, which combines direct heating and temperature measurement of metal nanofilms allowing temperature programmed desorption experiments is described. This setup enables the simultaneous monitoring of the thermal desorption flux from the surface of chemi-electric devices and detection of chemically induced hot charge carriers under UHV conditions. This method is demonstrated for the case of water desorption from a Pt/SiO2-n-Si metal-oxide-semiconductor nanostructure.

Meyburg, Jan Philipp; Nedrygailov, Ievgen I.; Hasselbrink, Eckart; Diesing, Detlef

2014-10-01

44

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

PubMed

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

Harper, Martin

2002-10-01

45

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

46

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

SciTech Connect

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

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

1982-04-01

47

Application of a diffusion-desorption rate equation model in astrochemistry.  

PubMed

Desorption and diffusion are two of the most important processes on interstellar grain surfaces; knowledge of them is critical for the understanding of chemical reaction networks in the interstellar medium (ISM). However, a lack of information on desorption and diffusion is preventing further progress in astrochemistry. To obtain desorption energy distributions of molecules from the surfaces of ISM-related materials, one usually carries out adsorption-desorption temperature programmed desorption (TPD) experiments, and uses rate equation models to extract desorption energy distributions. However, the often-used rate equation models fail to adequately take into account diffusion processes and thus are only valid in situations where adsorption is strongly localized. As adsorption-desorption experiments show that adsorbate molecules tend to occupy deep adsorption sites before occupying shallow ones, a diffusion process must be involved. Thus, it is necessary to include a diffusion term in the model that takes into account the morphology of the surface as obtained from analyses of TPD experiments. We take the experimental data of CO desorption from the MgO(100) surface and of D2 desorption from amorphous solid water ice as examples to show how a diffusion-desorption rate equation model explains the redistribution of adsorbate molecules among different adsorption sites. We extract distributions of desorption energies and diffusion energy barriers from TPD profiles. These examples are contrasted with a system where adsorption is strongly localized--HD from an amorphous silicate surface. Suggestions for experimental investigations are provided. PMID:25302396

He, Jiao; Vidali, Gianfranco

2014-01-01

48

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

E-print Network

THE EFFECT OF VARYING OVEN TEMPERATURES AND RES IDENCE TIMES ON THERMAL DESORPTION OF N-HEXANE AND 1-HEXENE FROM DIFFUSIVE ORGANIC VAPOR DOS IMETERS A Thesis bv KENNETH GARNETT STEELE Submitted to the Graduate College of Texas ARiM University... ORGANIC VAPOR DOSIMETERS A Thesis by KENNETH GARNETT STEELE Approved as to style and content by: (Cha' of C4 ttee) (Member ) ( e ) (He d f Departm ) December 1981 4804863 ABSTRACT The Effect of Varying Oven Temperatures and Residence Times...

Steele, Kenneth Garnett

2012-06-07

49

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

NASA Astrophysics Data System (ADS)

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

Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

2002-09-01

50

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

51

Water desorption from nanostructured graphite surfaces.  

PubMed

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

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

2013-12-21

52

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

SciTech Connect

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

Not Available

1980-06-01

53

Thermal desorption of 3He from T@C 60  

NASA Astrophysics Data System (ADS)

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

Sahoo, Rashmi R.; Patnaik, Archita

2001-11-01

54

Thermal desorption of circumstellar and cometary ice analogs  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

55

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

56

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

57

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

58

The Release of Trapped Gases from Amorphous Solid Water Films: II. “Bottom-Up” Induced Desorption Pathways  

SciTech Connect

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

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

2013-03-14

59

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

60

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

SciTech Connect

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

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

2007-11-14

61

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

62

Desorption From Interstellar Ices  

E-print Network

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

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

2007-08-24

63

Monte Carlo evaluation of thermal desorption rates  

SciTech Connect

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

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

1981-05-01

64

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

65

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

NASA Astrophysics Data System (ADS)

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

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

66

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...

67

Thermal desorption of circumstellar and cometary ice analogs  

E-print Network

Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2 O, CO, CO2, CH3 OH, and NH3 . The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. The TPD curves of water ice containing CO, CO2, CH3 OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and...

Martín-Doménech, Rafael; Bueno, Juan; Goesmann, Fred

2014-01-01

68

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

69

High-temperature interaction of nitrogen with thin iron films: Thermal desorption kinetics studies combined with microstructure analysis of Fe-N films  

NASA Astrophysics Data System (ADS)

The interaction of nitrogen with thin iron films at 673 K has been studied by means of thermal desorption mass spectrometry (TDMS) and a combination of scanning electron microscopy and transmission electron microscopy. TDMS spectra indicate the coexistence of atomic and molecular states of nitrogen adsorbed at 673 K and at a nitrogen pressure of 0.75 Pa. The origin of the molecular state is discussed as an intermediate state towards dissociative adsorption of nitrogen. Reconstruction of the polycrystalline iron film occurs as a result of both nitrogen interaction at 673 K and thermal desorption by heating the sample substrate to 950 K. The Fe grains become finer and the Fe film surface shows an increase in roughness upon interaction with nitrogen at 673 K. TDMS heating involves annealing of the Fe film and decomposition of the ``surface nitrides.'' The bulk structure of the Fe film is affected by the nitrogen-induced reconstruction of its topmost surface region.

Lisowski, W.; Keim, E. G.; Smithers, M. A.

2003-05-01

70

Finite difference program for calculating hydride bed wall temperature profiles  

SciTech Connect

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

Klein, J.E.

1992-10-29

71

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

72

Detecting Chemical Hazards with Temperature-Programmed  

E-print Network

covering this paper. Key Words chemiresistive, gas sensor, microarray, temperature dependence, toxic agents (CWAs) such as VX nerve agent (42 atoms, formula weight 267) and beyond. Hazardous compounds also include a variety of functional groups, such as the organic phosphonate nerve agents, the halogenated

Raman, Barani

73

THERMAL DESORPTION...NOW YOU'RE COOKIN'  

EPA Science Inventory

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

74

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

SciTech Connect

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

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

1994-12-01

75

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

PubMed

In this study a priority organic pollutants usually found in environmental water samples were considered to accomplish two extraction and analysis approaches. Among those compounds organochlorine compounds, pesticides, phthalates, phenols and residues of pharmaceutical and personal care products were included. The extraction and analysis steps were based on silicone rod extraction (SR) followed by liquid desorption in combination with large volume injection-programmable temperature vaporiser (LVI-PTV) and gas chromatography-mass spectrometry (GC-MS). Variables affecting the analytical response as a function of the programmable temperature vaporiser (PTV) parameters were firstly optimised following an experimental design approach. The SR extraction and desorption conditions were assessed afterwards, including matrix modification, time extraction, and stripping solvent composition. Subsequently, the possibility of performing membrane enclosed sorptive coating extraction (MESCO) as a modified extraction approach was also evaluated. The optimised method showed low method detection limits (3-35 ng L(-1)), acceptable accuracy (78-114%) and precision values (<13%) for most of the studied analytes regardless of the aqueous matrix. Finally, the developed approach was successfully applied to the determination of target analytes in aqueous environmental matrices including estuarine and wastewater samples. PMID:24209370

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

2013-12-15

76

PREDICTION OF RETENTION TIMES IN TEMPERATURE PROGRAMMED MULTICHROMATOGRAPHY  

EPA Science Inventory

The calculation of retention times for temperature programmed serially liked capillary gas chromatography columns is demonstrated. quations are derived for tbe verification of operating conditions via internal standards and for the precise calculation of ad-point pressure corresp...

77

Prediction of Retention Times in Temperature-Programmed Multichromatography.  

National Technical Information Service (NTIS)

The calculation of retention times for temperature programmed serially linked capillary gas chromatography columns is demonstrated. Equations are derived for the verification of operating conditions via internal standards and for the precise calculation o...

L. H. Wright, J. F. Walling

1991-01-01

78

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

SciTech Connect

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

Martínez-dlCruz, Lorena; Pfeiffer, Heriberto, E-mail: pfeiffer@iim.unam.mx

2013-08-15

79

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

80

THERMAL DESORPTION OF PETROLEUM CONTAMINATED SOILS  

EPA Science Inventory

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

81

Computational simulation characteristics desorption in TPS aggregates  

NASA Astrophysics Data System (ADS)

The article describes the modified model of desorption in a continuously operating apparatus in fluidized bed, which allows for a refined timing warm adsorbent particles of spherical shape at a flow of hot air to equalize the temperature along the radius of granules and assess relevant energy costs.

Goldaev, Sergey; Khushvaktov, Alisher

2014-08-01

82

Temperature-programmed reduction and HDS activity of sulfided transition metal catalyst: Formation of nonstoichiometric sulfur  

SciTech Connect

Sulfided alumina-supported transition metal catalysts have been studied using temperature-programmed reduction (TPR). The H{sup 2} and H{sub 2}S concentrations were determined simultaneously and the major processes occurring were discriminated, namely reduction of oxidic and sulfidic species and desorption of H{sub 2}S. Because of the high maximum reduction temperature and the high hydrogen partial pressure applied, a complete description of all species was acquired, except for the Cr and Mn catalysts which could not be reduced below 1270 K. After sulfiding at 673 K, TPR of alumina-supported transition metals showed that several types of sulfur were present, viz. (i) sulfur species with a stoichiometry in agreement with bulk thermodynamics, indicated as stoichiometric sulfur, (ii) a nonstochiometric sulfur species (S{sub x}) which was present in excess of the S/Me ratio based on bulk thermodynamics (not identical to elemental sulfur since it is present after purging at 673 K), (iii) S-H groups, and (iv) adsorbed H{sub 2}S. The mechanism of S{sub x} formation is discussed. The amounts of nonstoichiometric sulfur mainly depended on the type of transition metal and the pretreatment procedure. The influence of the reducibility of the stoichiometric and nonstoichiometric sulfur species on the hydrodesulfurization activity is discussed. The results presented indicate that chemisorption measurements may depend on the pretreatment of sulfided catalysts. 26 refs., 13 figs., 4 tabs.

Mangnus, P.J.; Riezebos, A.; Langeveld, A.D. van; Moulijn, J.A. [Univ. of Asterdam (Netherlands)] [Univ. of Asterdam (Netherlands)

1995-01-01

83

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...

84

Progress in BNL High-Temperature Hydrogen Combustion Research Program  

Microsoft Academic Search

The objectives of the BNL High-Temperature Hydrogen Combustion Research Program are discussed. The experimental facilities are described and two sets of preliminary experiments are presented. Chemical reaction time experiments have been performed to determine the length of time reactive mixtures of interest can be kept at temperature before reaction in the absence of ignition sources consumes the reactants. Preliminary observations

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

1992-01-01

85

Interaction of Acetone with Single Wall Carbon Nanotubes at Cryogenic Temperatures: A Combined Temperature Programmed  

E-print Network

charge transfer or polarization was found. Carbon black was used to model amorphous carbonaceous impurities present in as-produced SWCNTs. Desorption of acetone from carbon black revealed two peaks at 140 desorption from SWCNTs was peak at 300 K that was not observed for carbon black. Care should be taken when

Borguet, Eric

86

Interaction of Wide-Band-Gap Single Crystals With 248-nm Excimer Laser Radiation: XI. The Effect of Water Vapor and Temperature on Laser Desorption of Neutral Atoms From Sodium Chloride  

SciTech Connect

We investigate the effect of water vapor and temperature on the desorption of neutral Na and Cl from cleaved, single crystal NaCl during pulsed laser irradiation at 248-nm (KrF excimer). Neutral emissions in the presence of {approx}10-5 Pa of water vapor are much more intense than in ultra high vacuum (total pressure <10-7 Pa). Emission intensities are also increased by raising the substrate temperature or the laser fluence. The neutral time-of-flight signals are well described by Maxwell Boltzmann velocity distributions for effusing particles, which we use to estimate the peak surface temperatures during the laser pulse. The neutral emission intensities display Arrhenius behavior when plotted against both the background substrate temperature and the peak surface temperature. The resulting activation energies correspond to different, rate limiting processes, one of which is enhanced in the presence of water vapor. We propose a mechanism for the effect of water on these neutral emissions and discuss the implications.

Nwe, K H.; Langford, Stephen C.; Dickinson, J T.; Hess, Wayne P.

2005-01-20

87

Lateral interactions in the desorption kinetics of weakly adsorbed species: unexpected differences in the desorption of C 4 alkenes and alkanes from Ag(110) due to oriented ?-bonding of the alkenes  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) techniques were used to compare the desorption kinetics of butanes and butenes. Even though these molecules are weakly adsorbed and of similar molecular weight, alkane desorption shows evidence of weak attractive intermolecular interactions, whereas alkenes show clear evidence for moderately strong repulsive interactions in desorption. This behavior is contrary to the weak attractive intermolecular interactions expected for both the butanes and the butenes based on theories of physical adsorption, since the second virial coefficients for both in the gas phase are negative below 550 K. Adsorption of the alkenes clearly introduces repulsive intermolecular forces that are not present in the gas phase. The origin of these intermolecular forces is revealed by NEXAFS measurements for the alkenes, which show a strong orientation of the double bond axis parallel to the surface, indicative of weak directional bonding between the surface and the alkene. It appears that this preferred orientation caused by the surface alters the intermolecular forces between colliding pairs of alkenes, leading to the repulsive interactions that produce the decrease in the activation energy for desorption with increasing alkene coverage. This effect does not occur for butane, whose weak intermolecular interactions in the adsorbed layer are consistent with the predictions for physical adsorption.

Pawela-Crew, Jacquelyn; Madix, Robert J.

1995-09-01

88

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

89

Interaction of wide-band-gap single crystals with 248-nm excimer laser radiation. XI. The effect of water vapor and temperature on laser desorption of neutral atoms from sodium chloride  

SciTech Connect

We show that low partial pressures of water vapor (10{sup -5} Pa) dramatically increase the intensity of neutral Na and Cl emissions from cleaved, single-crystal NaCl during pulsed laser irradiation at 248 nm (KrF excimer). The time-of-flight distributions of these emissions are consistent with thermal desorption from laser-heated surfaces. Significantly, introducing water vapor lowers the particle velocities and thus the effective surface temperature during emission. Transmission measurements confirm that laser absorption is reduced in the presence of water vapor. The Arrhenius analysis of the emission intensities and effective temperatures show reduced activation energies in the presence of water vapor, which more than compensate for the vapor-induced reduction in laser absorption and surface temperature. Atomic force and scanning electron microscopy of the irradiated surfaces show evidence for accelerated monolayer-scale erosion in the presence of water vapor. A mechanism for the effect of water on these emission and erosion processes is proposed and discussed.

Nwe, K.H.; Langford, S.C.; Dickinson, J.T.; Hess, W.P. [Physics Department, Washington State University, Pullman, Washington 99164-2814 (United States); Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States)

2005-02-15

90

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

PubMed

Insertion of a programmed temperature vaporizing (PTV) injector under conditions of concurrent solvent recondensation (CSR) into the on-line HPLC-GC interface for on-column transfer (such as the retention gap technique with partially concurrent eluent evaporation) enables filtering off high boiling or involatile sample constituents by a desorption temperature adjusted to the required cut-off. Details of this technique were investigated and optimized. Memory effects, observed when transferred liquid was sucked backwards between the transfer line and the wall of the injector liner, can be kept low by a small purge flow rate through the transfer line at the end of the transfer and the release of the liquid through a narrow bore capillary kept away from the liner wall. The column entrance should be within the well heated zone of the injector to prevent losses of solute material retained on the liner wall during the splitless period. The desorption temperature must be maintained until an elevated oven temperature is reached to prevent peak broadening resulting of a cool inlet section in the bottom part of the injector. PMID:23394744

Biedermann, Maurus; Grob, Koni

2013-03-15

91

High-pressure temperature-programmed reduction of sulfided catalysts  

SciTech Connect

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

Labruyere, F.; Lacroix, M.; Breysse, M. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [and others] [Institut de Recherches sur la Catalyse, Villeurbanne (France); and others

1997-04-15

92

Desorption of hot molecules from photon irradiated interstellar ices  

E-print Network

We present the first results of a project designed to characterise the photon-driven physics and chemistry of polycyclic aromatic hydrocarbons (PAHs) and water ice in the interstellar medium (ISM). Layers of benzene and water ice were irradiated with a laser tuned to an electronic transition in the benzene molecule. The translational energy of desorbed molecules was measured by time-of-flight (ToF) mass spectrometry. Three distinct photodesorption processes were identified - a direct adsorbate-mediated desorption producing benzene molecules with a translational temperature of around 1200 K, an indirect adsorbate-mediated desorption resulting in water molecules with a translational temperature of around 450 K, and a substrate-mediated desorption of both benzene and water producing molecules with translational temperatures of around 530 K and 450 K respectively. The translational temperature of each population of desorbed molecules is well above the temperature of the ice matrix. The implications for gas phase ...

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

2007-01-01

93

Desorption of hot molecules from photon irradiated interstellar ices  

E-print Network

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

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

2007-05-16

94

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

95

Thermal desorption of petroleum contaminated soils  

SciTech Connect

The US Environmental Protection Agency recently funded a study which addresses the treatment of soils contaminated by petroleum hydrocarbons using low temperature thermal desorption (LTTD). The proposed paper will summarize some of the results of that study. LTTD has become a major petroleum contaminated soil remediation technology. The paper will define LTTD and discuss fundamental thermal desorption mechanisms such as hydrocarbon vapor pressure, steam stripping and soil characteristics. Full-scale LTTD equipment such as asphalt kilns, rotary dryers, thermal screws and indirect fired calciners will be described. Typical off-gas treatment equipment such as afterburners, baghouses, wet scrubbers, carbon and condensation/recovery will also be discussed. Full-scale LTTD performance data, such as hydrocarbon destruction efficiency, carbon monoxide and particulate stack concentrations, and soil total petroleum hydrocarbon residuals will be summarized.

Troxler, W.L.; Yezzi, J.J.; Cudahy, J.J.; Rosenthal, S.I.

1992-01-01

96

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction  

SciTech Connect

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

Song, Chunshan; Schobert, H.H.

1993-02-01

97

Thermal desorption spectra of the PdHx system in a powder form  

Microsoft Academic Search

Thermal desorption spectroscopy (TDS) of hydrogen from metal hydrides is a technique where the rate of hydrogen desorption is measured as a function of temperature while the temperature is increased linearly with time. The authors present the TDS of a powdered PdHx (particle size approximately 2 mu m) for various initial concentrations and for various heating rates. The spectra develop

A. Stern; A. Resnik; D. Shaltiel

1984-01-01

98

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

SciTech Connect

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

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

2011-04-05

99

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

100

Thermal desorption spectra from cavities in helium-implanted silicon  

Microsoft Academic Search

Thermal desorption spectra at constant ramp rate have been determined after helium implantation into bare silicon prepared for a large set of experimental conditions. The spectra can phenomenologically be classified as composed by two peaks: the alpha peak, centered on a temperature of 750-800°C with a shoulder extending to lower temperature (down to 550°C), and the beta peak, centered on

G. F. Cerofolini; G. Calzolari; F. Corni; S. Frabboni; C. Nobili; G. Ottaviani; R. Tonini

2000-01-01

101

Effect of time, temperature, and kinetics on the hysteretic adsorption-desorption of H2, Ar, and N2 in the metal-organic framework Zn2(bpdc)2(bpee).  

PubMed

The intriguing hysteretic adsorption-desorption behavior of certain microporous metal-organic frameworks (MMOFs) has received considerable attention and is often associated with a gate-opening (GO) effect. Here, the hysteretic adsorption of N(2) and Ar to Zn(2)(bpdc)(2)(bpee) (bpdc = 4,4'-biphenyldicarboxylate; bpee = 1,2-bipyridylethene) shows a pronounced effect of allowed experimental time at 77 and 87 K. When the time allowed is on the order of minutes for N(2) at 77 K, no adsorption is observed, whereas times in excess of 60 h is required to achieve appreciable adsorption up to a limiting total coverage. Given sufficient time, the total uptake for N(2) and Ar converged at similar reduced temperatures, but the adsorption of Ar was significantly more rapid than that of N(2), an observation that can be described by activated configurational diffusion. N(2) and Ar both exhibited discontinuous stepped adsorption isotherms with significant hysteresis, features that were dependent upon the allowed time. The uptake of H(2) at 77 K was greater than for both N(2) and Ar but showed no discontinuity in the isotherm, and hysteretic effects were much less pronounced. N(2) and Ar adsorption data can be described by an activated diffusion process, with characteristic times leading to activation energies of 6.7 and 12 kJ/mol. Fits of H(2) adsorption data led to activation energies in the range 2-7 kJ/mol at low coverage and nonactivated diffusion at higher coverage. An alternate concentration-dependent diffusion model is presented to describe the stepwise adsorption behavior, which is observed for N(2) and Ar but not for H(2). Equilibrium is approached very slowly for adsorption to molecularly sized pores at low temperature, and structural change (gate opening), although it may occur, is not required to explain the observations. PMID:21973224

Sircar, Sarmishtha; Wu, Haohan; Li, Jing; Lueking, Angela D

2011-12-01

102

Laser desorption fast gas chromatography–Mass spectrometry in supersonic molecular beams  

Microsoft Academic Search

A novel method for fast analysis is presented. It is based on laser desorption injection followed by fast gas chromatography-mass\\u000a spectrometry (GC-MS) in supersonic molecular beams. The sample was placed in an open air or purged laser desorption compartment,\\u000a held at atmospheric pressure and near room temperature conditions. Desorption was performed with a XeCl Excimer pulsed laser\\u000a with pulse energy

Tzvi Shahar; Shai Dagan; Aviv Amirav

1998-01-01

103

DESORPTION KINETIC MODEL FOR SUPERCRITICAL FLUID EXTRACTION OF SPEARMINT LEAF OIL  

Microsoft Academic Search

To characterize the dynamic behavior in supercritical CO2 extraction of essential oil components (carvone and limonene) from spearmint leaves under pressures of 69.0 bar (near-critical), 84.5 bar (supercritical), and 103.4 bar (supercritical) and temperatures of 39 and 49°C, a simplified desorption kinetic model was developed. In the desorption model, a linear irreversible desorption kinetics was assumed, and the releasing rate

Kyoung Heon Kim; Juan Hong

2001-01-01

104

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

SciTech Connect

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

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

1995-12-31

105

Desorption of hydrogen trapped in carbon and graphite  

NASA Astrophysics Data System (ADS)

Thermal desorption behavior of deuterium (D2) from isotropic graphites and a carbon fiber carbon composite (CFC) charged with D2 gas has been investigated to obtain information concerning hydrogen recycling and tritium inventory in fusion experimental devices as well as a futuristic fusion reactor. After thermal desorption experiments were conducted at temperatures up to 1740 K, a desorption peak at approximately 1600 K (peak 4) was discovered. This is in addition to the previously known peak at approximately 1300 K (peak 3). Peak 3 can be attributed to the release of deuterium controlled by the diffusion process in a graphite filler grain and peak 4 can be attributed to the detrapping of deuterium released from an interstitial cluster loop edge site. Activation energies of peaks 3 and 4 are estimated to be 3.48 and 6.93 eV, respectively. TDS spectra of D2 from graphite and CFCs had previously not been thoroughly investigated. A desorption peak at approximately 1600 K was discovered in the TDS spectra for all samples heated with a linear ramp rate of 0.1 K/s. For an isotropic graphite, ISO-880U, four desorption peaks were recognized in the TDS spectra at approximately 660 K, 900 K, 1300 K, and 1600 K. These peaks were named as peaks 1, 2, 3, and 4 in order of increasing temperature. Major desorption peaks (i.e., peaks 3 and 4) were analyzed and discussed in detail. The temperature of peak 3 was dependent on the size of a graphite filler grain. The desorption process is suggested to be controlled by deuterium diffusion within the filler grain with a strong influence of trapping sites, where the migration takes place as a sequence of detrapping and retrapping. The desorption for peak 4 can be ascribed to the detrapping reaction from an interstitial cluster loop edge site. Activation energies were estimated from the peak shift by varying the heating rate of TDS to be 3.48 and 6.93 eV for peaks 3 and 4, respectively. Theoretical desorption curves for peaks 3 and 4 with the above mentioned activation energies were narrower than those for the experimental desorption curve. The observed peak broadening can be attributed to the effects of grain size and activation energy distributions.

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

2013-11-01

106

Progress in BNL High-Temperature Hydrogen Combustion Research Program  

SciTech Connect

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

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

1992-12-31

107

Progress in BNL High-Temperature Hydrogen Combustion Research Program  

SciTech Connect

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

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

1992-01-01

108

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

109

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

110

Desorption times from rate equations, the master equation, and the Fokker-Planck equation  

Microsoft Academic Search

A set of rate equations for the bound-state occupation functions with transition probabilities calculated microscopically serves as a basis for a detailed study of various approximations available for the calculation of desorption times in gas-solid systems exhibiting physisorption. The exact time evolution of the adsorbate during the desorption process shows that quasiequilibrium is only maintained at low temperatures, where perturbation

H. J. Kreuzer; R. Teshima

1981-01-01

111

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

112

The influence of potassium doping on hydrogen adsorption on carbon nanocone material studied by thermal desorption and photoemission  

NASA Astrophysics Data System (ADS)

Hydrogen adsorption/desorption on potassium doped carbon nanocones was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. TPD shows that the hydrogen storage was enhanced by up to 40% after potassium doping. Hydrogen adsorption on K-modified carbon nanocone material seems more stable than that on the undoped material. The XPS results indicate that there is charge transfer from potassium to carbon. The C 1s binding energy increases with increased potassium doping and the peak becomes wider. These binding energy shifts may be explained by work function changes related to potassium doping. The K 2p spectra indicate that there are two different local environments for potassium on the carbon cone material.

Yu, Xiaofeng; Raaen, Steinar

2013-04-01

113

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

114

Hydrogen retention in tungsten materials studied by Laser Induced Desorption  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

115

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

116

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

117

Desorption of hydrogen and carbon monoxide from Ni(100), Ni(100)p(2 × 2)S, and Ni(100)c(2 × 2)S surfaces  

NASA Astrophysics Data System (ADS)

The adsorption and desorption of hydrogen and carbon monoxide from Ni(100), Ni(100)p(2 × 2)S and Ni(100)c(2 × 2)S were investigated by temperature programmed desorption. The presence of sulfur reduced values of the kinetic parameters which characterized hydrogen recombination from E = 21.3 {kcal}/{gmole} and v = 5 × 10 -2{cm2}/{atom· s} on clean Ni(100) to ˜10 {kcal}/{gmole} and 3 × 10 -8{cm2}/{atom· s} on the c(2 × 2) surface. The low values of the activation energy and pre-exponential factor for hydrogen desorption from sulfurized Ni(100) surfaces correlate with the peaked spatial distribution of desorbing hydrogen observed by others. The low v values appear to originate from severe steric hindrance to hydrogen recombination on these surfaces. Surface sulfur reduced the amount of carbon monoxide adsorbed in the state characteristic of the clean Ni(100) surface while enhancing additional peaks at lower temperatures. Desorption spectra of CO on the clean, p(2 × 2), and c(2 × 2) surfaces suggested that the primary binding site for carbon monoxide on clean Ni(100) is the four-fold hollow rather than the on top site.

Johnson, S.; Madix, R. J.

1981-06-01

118

Adsorption and Desorption Studies of Cesium on Sapphire Surfaces  

NASA Astrophysics Data System (ADS)

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

Zavadil, Kevin R.; Ing, Judith L.

1994-07-01

119

Adsorption and desorption studies of cesium on sapphire surfaces  

NASA Astrophysics Data System (ADS)

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

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

120

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

Microsoft Academic Search

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

Steffen Wiese; Thorsten Teutenberg; Torsten C. Schmidt

2011-01-01

121

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

SciTech Connect

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

Shanahan, K; Jeffrey Holder, J

2006-08-17

122

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

123

Low-temperature thermal energy storage program annual operating plan  

Microsoft Academic Search

The LTTES program operating plans for FY 1978 are described in terms of general program objectives and the technical activities being implemented to achieve these objectives. The program structure provides emphasis on seasonal thermal storage, daily\\/short-term thermal storage, and waste heat recovery and reuse. A work breakdown structure organizes the efforts being carried out in-house or through subcontract within each

H. W. Hoffman; D. M. Eissenberg

1979-01-01

124

Field desorption ion source development for neutron generators  

NASA Astrophysics Data System (ADS)

A new approach to deuterium ion sources for deuterium-tritium neutron generators is being developed. The source is based upon the field desorption of deuterium from the surfaces of metal tips. Field desorption studies of microfabricated field emitter tip arrays have been conducted for the first time. Maximum fields of 3 V/Å have been applied to the array tip surfaces to date, although achieving fields of 2 V/Å to 2.5 V/Å is more typical. Both the desorption of atomic deuterium ions and the gas-phase field ionization of molecular deuterium have been observed at fields of roughly 2 and 2-3 V/Å, respectively, at room temperature. The desorption of common surface adsorbates such as hydrogen, carbon, water, and carbon monoxide is observed at fields exceeding ˜1 V/Å. In vacuo heating of the arrays to temperatures of the order of 800 °C can be effective in removing many of the surface contaminants observed.

Solano, I.; Reichenbach, Birk; Schwoebel, P. R.; Chichester, D. L.; Holland, C. E.; Hertz, K. L.; Brainard, J. P.

2008-03-01

125

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

126

High temperature aspects of the European Hermes programs  

Microsoft Academic Search

The European Space Agency's (ESA) program for the development of the Hermes spaceplane is the first program in Europe dealing with hypersonics on a complex shape. Aerodynamics and aerothermodynamics, particularly with respect to the hot hypersonic flight regime, as well as structures and thermal protection techniques, are among the most important technologies for Hermes. Since the beginning of the Hermes

D. Isakeit

1991-01-01

127

Toluene removal from indoor air using a miniaturized photocatalytic air purifier including a preceding adsorption\\/desorption unit  

Microsoft Academic Search

The performance of the miniaturized photocatalytic air purifier including a continuous adsorption\\/desorption unit with a zeolite particles-loaded honeycomb rotor was investigated in the photocatalytic purification of 1m3 air containing toluene at concentrations of 3–11mgm?3 (about 1–3ppmv). While operating the continuous adsorption\\/desorption unit only, and for desorption temperatures controlled within the range of 90–120 and 130–160°C, the unit took approximately 10min

Fumihide Shiraishi; Takaaki Ishimatsu

2009-01-01

128

SO 2 adsorption and desorption kinetics on Pt(111)  

NASA Astrophysics Data System (ADS)

SO 2/Pt(111) adsorption and desorption kinetics in the temperature range 160-300 K were investigated by molecular beam technique and TDMS measurements. The initial sticking probability s0SO2 turns out to be unity independent of surface temperature, and the SSO 2(?) curves indicate the operation of a precursor mechanism. The TDMS spectra of SO 2 could be analysed by means of second order desorption kinetics indicating that SO 2 seems to be adsorbed dissociatively even at low temperatures (at least for small coverages). The resulting kinetic parameters are interpreted as values determining the recombination process (SO) ad + O ad ? (SO 2) ad, assuming the SO 2 molecule to desorb directly. Combining these results with those on SO dissociation and recombination recently obtained by us, it was possible to complete our proposed potential energy diagram for sulfur-oxygen reactions on Pt(111).

Köhler, U.; Wassmuth, H.-W.

1983-03-01

129

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

Microsoft Academic Search

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

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

1981-01-01

130

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

131

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

132

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

133

Thermal Desorption of Water-Ice in the Interstellar Medium  

E-print Network

Water (H2O) ice is an important solid constituent of many astrophysical environments. To comprehend the role of such ices in the chemistry and evolution of dense molecular clouds and comets, it is necessary to understand the freeze-out, potential surface reactivity, and desorption mechanisms of such molecular systems. Consequently, there is a real need from within the astronomical modelling community for accurate empirical molecular data pertaining to these processes. Here we give the first results of a laboratory programme to provide such data. Measurements of the thermal desorption of H2O ice, under interstellar conditions, are presented. For ice deposited under conditions that realistically mimic those in a dense molecular cloud, the thermal desorption of thin films (~50 molecular layers) is found to occur with zero order kinetics characterised by a surface binding energy, E_{des}, of 5773 +/- 60 K, and a pre-exponential factor, A, of 10^(30 +/- 2) molecules cm^-2 s^-1. These results imply that, in the dense interstellar medium, thermal desorption of H2O ice will occur at significantly higher temperatures than has previously been assumed.

Helen J. Fraser; Mark P. Collings; Martin R. S. McCoustra; David A. Williams

2001-07-25

134

Air separation with temperature and pressure swing  

DOEpatents

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

Cassano, Anthony A. (Allentown, PA)

1986-01-01

135

A control system for maintaining a predetermined temperature program  

E-print Network

of human skill. For example, in the process1ng of Damascus steel, the metal smith heated the steel to the color of the rising sun. A hor . eman standing by would take the . teel, when it reached, the proper temperature, and gallop away swinging it about... of human skill. For example, in the process1ng of Damascus steel, the metal smith heated the steel to the color of the rising sun. A hor . eman standing by would take the . teel, when it reached, the proper temperature, and gallop away swinging it about...

Roots, Edmund Nelson

2012-06-07

136

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

137

DESORPTION ISOTHERM MODELLING OF BLACK TEA USING ARTIFICIAL NEURAL NETWORKS  

Microsoft Academic Search

Neural network approach was selected for the modelling of desorption isotherms of black tea and a neural network model trained using Levenberg-Marquardt algorithm. The trained network was used for studying the influence of randomised training data of temperature in the range of 25–80°C and the water activity range of 0.10–0.90 and different number of hidden neurons. The obtained results, compared

P. C. Panchariya; D. Popovic; A. L. Sharma

2002-01-01

138

Low energy electron stimulated desorption from DNA films dosed with oxygen  

PubMed Central

Desorption of anions stimulated by 1–18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50–250 K). The SAMs, composed of 10 nucleotides, are dosed with O2. The OH? desorption yields increase markedly with exposure to O2 at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O?, attributable to dissociative electron attachment to trapped O2 molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O2 shows that this surprising increase in OH? desorption, at elevated temperatures, arises from the reaction of O2 with damaged DNA sites. These results thus appear to be a manifestation of the so-called “oxygen fixation” effect, well known in radiobiology. PMID:22779623

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

2013-01-01

139

Isoparaffin production by aqueous phase processing of sorbitol over the Ni\\/HZSM-5 catalysts: Effect of the calcination temperature of the catalyst  

Microsoft Academic Search

Ni\\/HZSM-5 catalysts calcined at different temperatures were used in the isoparaffin production by aqueous phase processing of sorbitol and characterized by N2 physical adsorption, temperature-programmed reduction (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD) and Raman techniques. The effect of calcination temperature of the catalysts on the catalytic performance for the reaction was investigated. The activity test results indicated that the maximal

Qing Zhang; Ke Qiu; Bing Li; Ting Jiang; Xinghua Zhang; Longlong Ma; Tiejun Wang

2011-01-01

140

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

141

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

142

Desorption of uranium from amidoxime fiber adsorbent  

SciTech Connect

An amidoxime fibrous adsorbent is contacted with uranium-enriched seawater (10 ppm); about 10 mg uranium is loaded per 1 g dry fiber. Then the rate and yield of uranium desorption from the fiber are determined with various eluents. Acid solutions are superior to alkali carbonate solutions as eluents. With a 0.1 mol[center dot]L[sup [minus]1] HCl solution, desorption is completed in 2 hours regardless of the presence of uranium in the leaching solution up to 15 ppm ([approx]6 [times] 10[sup [minus]5]mol[center dot]L[sup [minus]1]). Serial operation of the adsorption-desorption cycle four times does not affect desorption efficiency, but the addition of heavy metal ions to the eluent at a level of 1.8 [times] 10[sup [minus]3]mol[center dot]L[sup [minus]1] significantly decreases desorption efficiency. 13 refs., 5 figs., 1 tab.

Goto, Akira; Morooka, Shigeharu; Fukamachi, Masakazu; Kusakabe, Katsuki (Kyushu Univ., Fukuoka (Japan)); Kago, Tokihiro (Towa Univ., Fukuoka (Japan))

1993-10-01

143

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

144

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

PubMed

This manuscript investigates the thermal desorption behaviour of MgH(2)/Mg(OH)(2) composites by means of thermal desorption spectroscopy. Besides the H(2)O and H(2) desorption events due to Mg(OH)(2) dehydration and MgH(2) decomposition reactions, respectively, two additional H(2) desorption peaks arise at lower temperatures. These peaks are related to solid-state reactions between magnesium hydride and magnesium hydroxide through different channels. The low temperature H(2) peak ( approximately 150 degrees C) is related to reaction between a H atom diffusing from MgH(2) and a surface OH group, whereas the intermediate temperature H(2) peak ( approximately 350 degrees C) is due to an interface reaction between the hydride and the hydroxide. The present work supports the theory that the onset of the H(2) desorption coming from MgH(2) decomposition is controlled by an incubation process, consisting in the formation of catalytically active vacancies at the MgO/Mg(OH)(2) surface by dehydration. Possible ways to improve the H(2) desorption kinetics from MgH(2) are discussed in the light of the results obtained. PMID:20066343

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

2010-01-21

145

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

146

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

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

147

Development program for the high-temperature nuclear process heat system  

Microsoft Academic Search

A comprehensive development program plan for a high-temperature nuclear ; process heat system with a very high temperature gas-cooled reactor heat source ; is presented. The system would provide an interim substitute for fossil-fired ; sources and ultimately the vehicle for the production of substitute and synthetic ; fuels to replace petroleum and natural gas. The dwindling domestic reserves of

Jiacoletti

1975-01-01

148

Adsorption and desorption characteristics of arsenic onto ceria nanoparticles  

NASA Astrophysics Data System (ADS)

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 (? H 0 , ? S 0 , and ? G 0 ) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment.

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

2012-01-01

149

Adsorption and desorption characteristics of arsenic onto ceria nanoparticles.  

PubMed

The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (?H0, ?S0, and ?G0) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment. PMID:22269298

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

2012-01-01

150

Hydrogen absorption-desorption properties of U 2Ti  

NASA Astrophysics Data System (ADS)

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

Takuya, Yamamoto; Satoru, Tanaka; Michio, Yamawaki

1990-02-01

151

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

152

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

153

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

PubMed

The carbon dioxide (CO2) desorption rate from CO2- loaded aqueous diethanolamine (DEA) solutions was measured using a stirred cell with a flat gas-liquid interface. The measurements were performed in the temperature range of 293.15-313.15 K and an amine concentration range of 10-20% mass DEA. Measurements were based on a semibatch isothermal absorption of the gas until the equilibrium state was reached, followed by desorption, which was initiated by the pressure release in the system. A simplified mass transfer model based on the film theory coupled with CO2, mass balance was developed to interpret the experimental data. On the basis of the proposed model, the initial mass transfer rates were calculated from the experimental results. The calculated initial desorption rates enabled estimation of the enhancement factor for CO2 mass transfer from aqueous DEA solutions. Analysis of the experimental data showed that desorption took place in the diffusive mass transfer regime. PMID:20842932

Kierzkowska-Pawlak, Hanna; Chacuk, Andrzej

2010-08-01

154

Kinetic analysis of California oil shale by programmed temperature micropyrolysis  

SciTech Connect

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

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

1991-12-09

155

Temperature-programmed reaction in zeolites. I. The decomposition of Fe(CO)/sub 5/  

SciTech Connect

The nonisothermal kinetics of the decomposition of iron pentacarbonyl adsorbed on type Y zeolite have been studied. The spectra of the temperature-programmed reaction was recorded from the evolution of CO with a linear change in temperature. With a decrease in Fe(CO)/sub 5/ content in the specimen additional distinguishable maxima appear in the high-temperature region for high coverages, which is probably associated with the competition between the monomolecular and bimolecular decomposition of Fe(CO)/sub 5/. The high-temperature maxima are assigned to the successive release of CO molecules from Fe(CO)/sub 5/ fragments.

Zakharov, A.N.; Vanegas Fetekua, K.Kh.; Romanovskii, B.V.

1988-04-01

156

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

157

Thermal Desorption Analysis Applied to Materials Characterization.  

National Technical Information Service (NTIS)

Thermal desorption analysis is used to characterize the outgassing properties of both vacuum envelope materials and the hydrided sources and targets in neutron generators employing erbium deuteride films and erbium tritide target. (ERA citation 05:002698)

T. K. Mehrhoff

1979-01-01

158

Surface Electronic Spectra Detected by Atomic Desorption  

SciTech Connect

Using continuously tunable laser excitation of KI we measure the velocity profiles and the yield of desorbing hyperthermal iodine atoms as a function of photon energy. Based on the theoretical model of desorption we demonstrate that these spectra display a signature of a surface exciton and constitute a new sensitive method of surface specific desorption spectroscopy. Our results demonstrate that creation of surface excitions can be a much more general phenomenon than was previously thought based on extant spectroscopic measurements.

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

2003-10-10

159

Effect of CO2 Sorption and Desorption on the Creep Response of Polycarbonate  

E-print Network

transition temperature. Bubble nucleation and growth ensue in the polymer upon heating, and the cells. At the appropriate time, the foamed polymer is quenched in room temperature water to prevent further bubble growthEffect of CO2 Sorption and Desorption on the Creep Response of Polycarbonate Arun Pasricha, Gregory

Kumar, Vipin

160

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

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

2014-08-01

161

Adsorption, desorption and reaction kinetics of nitric oxide on a stepped pd(111) surface  

NASA Astrophysics Data System (ADS)

We performed LEED, TDMS and molecular beam measurements on the adsorption system NO/stepped Pd(111) down to 160 K. The initial sticking coefficient is found to be unity independent of temperature, and the adsorption kinetic is dominated by a precursor state. The saturation coverage at temperatures below 200 K is one monolayer, which is correlated with a sharp (2 × 2) LEED pattern. At temperatures above 400 K, a small amount of the adsorbed NO molecules dissociates, which occurs at structural defects, i.e. at steps, only. Besides NO the only desorbing species are N 2 and N 2O. The dissociation capability of the surface is extremely sensitive to adsorbed oxygen, which blocks the step sites. From thermal desorption measurements we could determine the fraction of NO molecules that dissociate as a function of the applied heating rate; this allowed an estimate of the kinetic parameters. The activation energy for dissociation was thus found to be 1.2 eV with a pre-exponential of 4 × 10 11 s -1. Since dissociation could be suppressed using a small pre-coverage of oxygen in thermal desorption experiments with NO we were able to determine the desorption kinetics from an evaluation of the desorption spectra via isothermic and isosteric desorption rates: in the low coverage limit the activation energy for desorption is 1.52 eV with a pre-exponential of 2.6 × 10 14 s -1. The variation of the desorption energy with coverage indicates the operation of strong lateral interactions between the adsorbed NO molecules.

Schmick, H.-D.; Wassmuth, H.-W.

1982-12-01

162

Molecular Desorption from Dust in Star-Forming Regions  

Microsoft Academic Search

The chemistry of collapsing protostellar cores has been reassessed so as to include the effects of desorption of molecular species from grain mantles. Several desorption mechanisms have been considered, including the mechanism by which desorption occurs as a result of H2 formation on the grains. Although the desorption time-scale is typically larger than the free-fall time, the desorption processes may

K. Willacy; J. M. C. Rawlings; D. A. Williams

1994-01-01

163

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

164

Kinetics for potassium desorption from an iron oxide catalyst studied by field reversal  

NASA Astrophysics Data System (ADS)

We apply the field reversal method for kinetics studies to alkali desorption from real catalysts. The electric field outside the catalyst surface is switched rapidly between accelerating and retarding field, and the transient signals due to desorbing neutral and ionic species are recorded to obtain first-order rate constants. The technique is applied to potassium emission from an industrial iron oxide catalyst used for styrene production. Desorption rate constants in the range of 10 -2-10 2 s -1 are obtained at catalyst temperatures of 790-1160 K, i.e. in the temperature range of the industrial process. Activation energies and pre-exponential factors are determined from the temperature dependence of the rate constants. We observe several parallel desorption modes corresponding to diffusion and desorption from different potassium populations on the catalyst. We identify a phase transition around 1000 K, diffusion-limited processes, as well as coupled diffusion-desorption modes. We conclude the field reversal technique to be a powerful method to characterise alkali processes on complex surfaces.

Lundin, Jörgen; Hansson, Tony; Pettersson, Jan B. C.

1994-04-01

165

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

SciTech Connect

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

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

1999-06-30

166

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

167

Low-Temperature Thermal Energy Storage Program Annual Progress Report for Period, October 1976--September 1977.  

National Technical Information Service (NTIS)

The Low-Temperature Thermal Energy Storage (LTTES) Program is a part of a national effort to develop means for reducing U.S. dependence on oil and natural gas as primary energy soures. To this end, LTTES addresses the development of advanced sensible and ...

H. W. Hoffman, R. J. Kedl, S. K. Fraley

1978-01-01

168

Temperature-programmed combustion studies of coal and maceral group concentrates  

Microsoft Academic Search

Temperature-programmed combustion profiles of coals and their maceral group concentrates were obtained by thermogravimetric analysis in air at a heating rate of 15 K min?1. The maceral group concentrates were prepared by density separation of demineralized, micronized coal samples. Particle size had a significant effect on combustion profiles, with increased complexity in terms of the number of peaks observed for

Jimmy B. Milligan; K. Mark Thomas; John C. Crelling

1997-01-01

169

Kinetics of hydrogen adsorption and desorption on thin platinum films  

NASA Astrophysics Data System (ADS)

The nature of hydrogen adsorption on thin platinum films at 78, 195, 273 and 298 K has been studied by means of sticking probability measurements and thermal desorption mass spectrometry (TDMS). A high value of the initial sticking coefficient ( S0 ? 0.95) was found at all temperatures. The behaviour of the sticking probability S as a function of hydrogen coverage ? has been analyzed. Three TDMS peaks of hydrogen were detected on Pt films when the adsorption was carried out at 195 K. The TDMS analysis carried out for hydrogen adsorbed at 78 K, revealed the existence of a molecular form of hydrogen deposit.

Lisowski, W.

1988-05-01

170

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

171

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

NASA Astrophysics Data System (ADS)

In the past 10 years, the Ocean Drilling Program (ODP) has drilled several medium to high temperature environments (T = 150-312 deg C). These environments include the Costa Rica Rift (Legs 140 and 148), the Middle Valley of the northern Juan de Fuca Ridge (Legs 139 and 169), the Trans-Atlantic Geotraverse (TAG) area (Leg 158), and the Manus Basin (Leg 193). Wireline and memory temperature probes deployed in high-temperature environments measured profiles of thermal history, and thus structural features controlling active fluid flow, in several of these environments. These experiences illustrate the importance of measuring in situ borehole temperatures while drilling and logging operations are underway. Hole cooling is one successful strategy that relies on the circulation of cool fluids and allows other downhole measurements to be made. However, hole cooling also adversely affects the stability of the drill hole. Temperature sensors built into the wireline cablehead provide additional information that decreases the risk of instrument damage due to high temperatures that can be encountered while logging. Likewise, a newly-developed core barrel device provides essential information for assessing temperature conditions that reduce the risk of instrument damage while drilling. These strategies are critical for acquiring wireline and logging-while-drilling (LWD) logs in high temperature environments. We discuss the technical approaches used to make these high temperature measurements and evaluate their success as well as their potential for future use in marine and continental scientific drilling.

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

2001-05-01

172

Thermal desorption spectra from cavities in helium-implanted silicon  

NASA Astrophysics Data System (ADS)

Thermal desorption spectra at constant ramp rate have been determined after helium implantation into bare silicon prepared for a large set of experimental conditions. The spectra can phenomenologically be classified as composed by two peaks: the ? peak, centered on a temperature of 750-800°C with a shoulder extending to lower temperature (down to 550°C), and the ? peak, centered on a lower temperature depending on the implantation-annealing conditions. The ? peak is attributed to the emission from cavities, while the ? peak is attributed to the emission from vacancylike defects. A detailed theory describing helium effusion from stable cavities as controlled by the interatomic helium-helium potential is proposed and found to reproduce accurately most of the ? peaks. The postimplantation of hydrogen into samples displaying a pure ? emission results in an ? peak which can be described by the same model as above provided that the cavities are unstable and shrink during desorption in such a way as to maintain constant the concentration of contained helium.

Cerofolini, G. F.; Calzolari, G.; Corni, F.; Frabboni, S.; Nobili, C.; Ottaviani, G.; Tonini, R.

2000-04-01

173

Adsorption and desorption of uranium (VI) in aerated zone soil.  

PubMed

In this paper, the adsorption and desorption behavior of uranium (VI) in aerated zone soil (from Southwest China) was systematically investigated using a static experimental method in order to provide useful information for safety assessment of the disposal of (ultra-)low uraniferous radioactive waste, as well as a potential remediation method for uranium-contaminated soils. The adsorption behavior of uranium (VI) was firstly studied by batch experiments as functions of contact time, pH, liquid/solid ratio, temperature, colloids, minerals and coexistent ions. The results indicated that the adsorption of uranium (VI) by natural soil was efficient at an initial concentration of 10 mg/L uranium (VI) nitrate solution with 100 mg natural soil at room temperature when pH is about 7.0. The adsorption was strongly influenced by the solution pH, contact time, initial concentration and colloids. The adsorption equilibrium for uranium (VI) in soil was obtained within 24 h and the process could be described by the Langmuir adsorption equation. For uranium (VI) desorption, EDTA, citric acid and HNO(3) were evaluated under different conditions of temperature, concentration and proportion of liquid to solid. The adsorbed uranium (VI) on natural soil could be easily extracted by all these agents, especially by HNO(3), implying that the uranium-contaminated soils can be remedied by these reagents. PMID:22939949

Li, Xiaolong; Wu, Jiaojiao; Liao, Jiali; Zhang, Dong; Yang, Jijun; Feng, Yue; Zeng, Junhui; Wen, Wei; Yang, Yuanyou; Tang, Jun; Liu, Ning

2013-01-01

174

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

PubMed Central

Summary 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 which signals to the transcription factor DAF-16/FOXO. Human TRPA1 can functionally substitute for worm TRPA-1 in promoting longevity. Our results reveal a new 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

2013-01-01

175

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

PubMed

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

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

2013-01-01

176

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

SciTech Connect

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

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

2011-07-15

177

Development of a stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry method for the simultaneous determination of several persistent organic pollutants in water samples.  

PubMed

Stir bar sorptive extraction (SBSE) and thermal desorption followed by capillary gas chromatography coupled to mass spectrometry (SBSE-TD-GC-MS) was applied to the simultaneous determination of ultra-traces of 16 polycyclic aromatic hydrocarbons (PAHs), 12 polychlorinated biphenyls (PCBs), 6 phthalate esters (PEs) and 3 nonylphenols (NPs) in water samples. The parameters that could affect the sorption-desorption efficiency were studied. A Plackett-Burman design was used for the screening of the main effects of the experimental parameters related to the desorption step (desorption time, desorption temperature, desorption flow, cryo-focusing temperature and vent pressure). Afterwards, two central composite designs were used to find the optimal process settings for the extraction and desorption steps. The best analytical compromise conditions for the simultaneous determination of analytes from spiked water samples were found to be: sample volume (20 mL), sodium chloride addition (30%), methanol addition (20%), desorption time (10 min), desorption temperature (300 degrees C), desorption flow (23 mL min(-1)), cryo-focusing temperature (-50 degrees C) and vent pressure (7 psi). Remarkable recovery, repeatability and reproducibility were attained. Furthermore, excellent linearities (r(2) = 0.959-0.999) and low detection limits (0.1-10 ng L(-1)) were also achieved for the congeners studied. The proposed methodology was applied for the simultaneous determination of PAHs, PCBs, PEs and NPs in sea and estuarine waters. The influence of humic acids on the recovery was also studied. PMID:17706230

Prieto, A; Zuloaga, O; Usobiaga, A; Etxebarria, N; Fernández, L A

2007-12-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

179

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

SciTech Connect

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

Horner, M.W.

1980-12-01

180

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...

181

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, ...

182

Enhanced desorption of 2,4,6 Trinitrotoluene  

E-print Network

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

Aturaliye, Upul Anuruddha

2012-06-07

183

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

Microsoft Academic Search

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

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

2007-01-01

184

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

185

THE SORPTION AND DESORPTION OF IODINE  

Microsoft Academic Search

Adsorption isothernas were measured for various substances for iodine in ; carbon tetrachloride at 20 deg C. Sorption of radioiodine by these solids from ; the gas phase was also measured at 200 deg C; exchange of the radioiodine with ; inactive iodine has shown considerable differences in behavior; thermal ; desorption is not easily accomplished. The results are discussed

F. Hudswell; E. Furby; J. G. Simons; K. L. Wilkinson

1960-01-01

186

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

187

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

188

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

189

Isothermal and isobaric desorption of carbon dioxide by purge  

Microsoft Academic Search

Adsorption and desorption constitute the two most basic steps in all pressure swing adsorption (PSA) processes for gas separation. The desorption steps are the primary energy-consuming steps in the PSA process. They also dictate the overall separation efficiency. Isothermal and isobaric desorption of carbon dioxide was experimentally evaluated by purging adsorbent columns saturated with pure carbon dioxide with pure hydrogen,

Shivaji Sircar; Timothy C. Golden

1995-01-01

190

Lindane Adsorption-Desorption on Chitin in Sea Water  

Microsoft Academic Search

The adsorption and desorption processes by solid materials are important in determining the movement and fate of pesticide compounds in aquatic systems. Chitin is one of the constituents of natural organic matter and may serve as a model organic phase for studying the pesticide adsorption-desorption in marine systems. The lindane adsorption-desorption to chitin has been studied as a function of

M. Gonzalez-davila; J. Perez-Peña; J. M. Santana-casiano

1992-01-01

191

Thermal desorption of CH4 retained in CO2 ice  

E-print Network

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

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

2008-01-21

192

Electron stimulated desorption of neutral species from (100) KCl surfaces  

NASA Astrophysics Data System (ADS)

Composition changes of a (100) KCl surface bombarded by 1 keV electrons have been studied by Auger electron spectroscopy. Intensity ratios of characteristic alkali and halogen Auger lines were monitored as a function of target temperature and beam current density. In addition, for the first time angle-resolved energy distributions of electron desorbed K and Cl atoms were measured using mass-analyzed time of flight techniques. For temperatures higher than about 100°C, a near-stoichiometric surface composition was obtained and a significant non-thermal component was observed in the kinetic energy distributions of Cl atoms emitted normal to the (100) surface. These results can be interpreted in terms of new concepts regarding the excitonic mechanism of electron stimulated desorption (ESD).

Szymonski, M.; Poradzisz, A.; Czuba, P.; Kolodziej, J.; Piatkowski, P.; Fine, J.; Tanovic, L.; Tanovic, N.

1992-01-01

193

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

194

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.

195

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

196

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

197

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

198

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

199

Desorption of hexachlorobiphenyl from selected particulate matter  

E-print Network

amounts of the HCBP. This is speculated to be a function of particle structure, organic carbon content of the particles, and HCBP's hydrophobic and lipophilic nature. Two mathematical models were developed considering sorption and desorption... to be first order processes. The model successfully predicted stripping HCBP from water as well as a 300 m J~l sand suspension. However, as the system became more complex ? 2 particle types--the models broke down. It was concluded that sorption...

Rorschach, Reagan Cartwright

2012-06-07

200

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

201

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

SciTech Connect

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

Blackaby, W.B.

1994-09-06

202

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

203

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

SciTech Connect

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

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

1980-03-01

204

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

205

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

206

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

207

Dynamics of the defect-mediated desorption of alkali halide surfaces  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

208

Laser desorption fast gas chromatography-mass spectrometry in supersonic molecular beams.  

PubMed

A novel method for fast analysis is presented. It is based on laser desorption injection followed by fast gas chromatography-mass spectrometry (GC-MS) in supersonic molecular beams. The sample was placed in an open air or purged laser desorption compartment, held at atmospheric pressure and near room temperature conditions. Desorption was performed with a XeCl Excimer pulsed laser with pulse energy of typically 3 mJ on the surface. About 20 pulses at 50 Hz were applied for sample injection, resulting in about 0.4 s injection time and one or a few micrograms sample vapor or small particles. The laser desorbed sample was further thermally vaporized at a heated frit glass filter located at the fast GC inlet. Ultrafast GC separation and quantification was achieved with a 50-cm-long megabore column operated with a high carrier gas flow rate of up to 240 mL/min. The high carrier gas flow rate provided effective and efficient entrainment of the laser desorbed species in the sweeping gas. Following the fast GC separation, the sample was analyzed by mass spectrometry in supersonic molecular beams. Both electron ionization and hyperthermal surface ionization were employed for enhanced selectivity and sensitivity. Typical laser desorption analysis time was under 10 s. The laser desorption fast GC-MS was studied and demonstrated with the following sample/matrices combinations, all without sample preparation or extraction: (a) traces of dioctylphthalate plasticizer oil on stainless steel surface and the efficiency of its cleaning; (b) the detection of methylparathion and aldicarb pesticides on orange leaves; (c) water surface analysis for the presence of methylparathion pesticide; (d) caffeine analysis in regular and decaffeinated coffee powder; (e) paracetamol and codeine drug analysis in pain relieving drug tablets; (f) caffeine trace analysis in raw urine; (g) blood analysis for the presence of 1 ppm lidocaine drug. The features and advantages of the laser desorption fast GC-MS are demonstrated and discussed. PMID:9879375

Shahar, T; Dagan, S; Amirav, A

1998-06-01

209

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

PubMed

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

Stolee, Jessica A; Vertes, Akos

2011-05-28

210

Sorption and desorption of cobalt by Oscillatoria anguistissima.  

PubMed

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

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

1999-07-01

211

Non-contact temperature measurement requirements of ground-based research and flight programs at JPL  

NASA Technical Reports Server (NTRS)

The Modular Containerless Processing Facility project is responsible for the development of flight equipment and of the accompanying scientific and technological research necessary to carry out containerless investigations in the low gravity of earth orbit. The requirement for sample temperature measurement is just one of the many physical properties determination needs that must be satisfied before the useful exploitation of low gravity and containerless experimentation techniques can be achieved. The specific implementation of temperature measurement for the ground-based research program is different from that of the flight hardware development project. The needs of the latter must also be differentiated according to the chronological order of the relevant space flight missions. Immediate demands of Spacelab instruments must be addressed by the adaptation of existing reliable technology to the special and restrictive on-orbit environment, while more advanced and yet unperfected techniques will be assigned to enterprises further in the future. The wide range of application of the containerless methods to the study of phenomena involving different states of matter and environmental conditions requires the satisfaction of a variety of boundary conditions through different approaches. An important issue to be resolved will be whether an integrated program dedicated to solve the problems of all the microgravity experimental effort will allow the solution of specific demands of existing as well as future flight equipment.

Trinh, E. H.

1989-01-01

212

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

PubMed Central

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

2013-01-01

213

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

214

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

215

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

216

Characteristics of isothermal adsorption and desorption of aluminum ion to/from humic acids.  

PubMed

The adsorption and desorption characteristics of Al3+ to/from humic acids at different pH, ionic strength, and temperature were studied by the C-25 glucosan-gel chromatography method. The results showed that the maximum adsorption amount (Q(max)) and adsorption constant (k) increased, whereas, the absolute value of standard thermodynamic molar free energy change (deltaG(m)0) decreased with the increase of pH at constant ionic strength and temperature. With ionic strength increasing from 0 to 0.15 mol/L, Q(max) and k increased and the absolute value of deltaG(m)0 decreased at constant pH and temperature. High temperature was unfavorable for the adsorption reaction, as indicated by the dramatic decrease of Q(max) and the absolute value of deltaG(m)0 with an increase in temperature. The standard thermodynamic molar free energy change (deltaG(m)0) and the standard thermodynamic enthalpy change (deltaH(m)0) of the adsorption reaction were both negative, suggesting that adsorption reaction was spontaneous and exothermic. The desorption rate of HA-Al3+ complex accelerated with the decrease of pH, and a significant linear relationship could be obtained between pH and the desorption rates of Al3+ from humic acids. These results demonstrated that the Al3+ adsorption reaction was a "biphase" reaction, and adsorption occurred at both the interior and exterior adsorption sites of humic acids. PMID:18575111

Wang, Qiang; Wei, Shiqiang; Huang, Yuming; Zhang, Jinzhong

2008-01-01

217

April 9-10, 2003 HAPL Program Meeting, SNL, Albuquerque, N.M. 1 Lowering Target Initial Temperature to  

E-print Network

April 9-10, 2003 HAPL Program Meeting, SNL, Albuquerque, N.M. 1 Lowering Target Initial Temperature National Laboratory, Albuquerque, N. M. April 9-10, 2003 #12;April 9-10, 2003 HAPL Program Meeting, SNL, Albuquerque, N.M. 2 Target Survival During Injection · Target heat source: energy exchange from chamber

Raffray, A. René

218

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

PubMed

A novel method in which the water sorption curve is observed under linearly temperature-raising conditions was proposed to estimate the gelatinization temperature of starch-containing foods, it was applied in an estimation of the gelatinization temperatures of dried noodles. The gelatinization temperatures of two kinds of spaghetti, dried at high and low temperature, were 52.3 and 53.1 °C, and those of udon, kishimen, juwari-soba, hachiwari-soba, so-called common soba, Malony(®), and kuzukiri were 57.0, 57.8, 61.1, 59.6, 57.4, 48.4, and 49.1 °C. The gelatinization temperatures estimated by the method were between the onset and peak temperatures obtained by differential scanning calorimetric measurement. PMID:23132576

Hasegawa, Ayako; Ogawa, Takenobu; Adachi, Shuji

2012-01-01

219

Plasma desorption mass spectrometry of organics at low temperatures  

E-print Network

irradiate and desorb iona from a sample surface, the analyte is supported on a substrate that absorbs light at the wavelen h of the incident hotons - intense electric fields form iona from heated samples supported on dendrites, microneedles, or tips... irradiate and desorb iona from a sample surface, the analyte is supported on a substrate that absorbs light at the wavelen h of the incident hotons - intense electric fields form iona from heated samples supported on dendrites, microneedles, or tips...

Shirey, Eldon Lynn

2012-06-07

220

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

PubMed

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention times based on temperature-gradient as well as isothermal input data was investigated. For a small temperature interval of ?T=40°C, both approaches result in very similar predictions. Average relative errors of predicted retention times of 2.7% and 1.9% were observed for simulations based on isothermal and temperature-gradient measurements, respectively. Concurrently, it was investigated whether the accuracy of retention time predictions of segmented temperature gradients can be further improved by temperature dependent calculation of the parameter S(T) of the LES relationship. It was found that the accuracy of retention time predictions of multi-step temperature gradients can be improved to around 1.5%, if S(T) was also calculated temperature dependent. The adjusted experimental design making use of four temperature-gradient measurements was applied for systematic method development of selected food additives by high-temperature liquid chromatography. Method development was performed within a temperature interval from 40°C to 180°C using water as mobile phase. Two separation methods were established where selected food additives were baseline separated. In addition, a good agreement between simulation and experiment was observed, because an average relative error of predicted retention times of complex segmented temperature gradients less than 5% was observed. Finally, a schedule of recommendations to assist the practitioner during systematic method development in high-temperature liquid chromatography was established. PMID:22218327

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

2012-01-27

221

Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets.  

PubMed

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

Endo, Satoshi; Yuyama, Masaki; Takada, Hideshige

2013-09-15

222

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

SciTech Connect

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

Bonne, R.L.C.; Langeveld, A.D. van; Moulijn, J.A. [Univ. of Amsterdam (Netherlands)] [Univ. of Amsterdam (Netherlands)

1995-06-01

223

Thermal desorption mass spectrometer for mass metrology  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

224

Decomposition of thin titanium deuteride films; thermal desorption kinetics studies combined with microstructure analysis  

NASA Astrophysics Data System (ADS)

The thermal evolution of deuterium from thin titanium films, prepared under UHV conditions and deuterated in situ at room temperature, has been studied by means of thermal desorption mass spectrometry (TDMS) and a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The observed Ti film thickness dependent morphology was found to play a crucial role in the titanium deuteride (TiD y) film formation and its decomposition at elevated temperatures. TDMS heating induced decomposition of fine-grained thin Ti films, of 10-20 nm thickness, proceeds at low temperature (maximum peak temperature Tm about 500 K) and its kinetics is dominated by a low energy desorption ( ED = 0.61 eV) of deuterium from surface and subsurface areas of the Ti film. The origin of this process is discussed as an intermediate decomposition state towards recombinative desorption of molecular deuterium. The TiD y bulk phase decomposition becomes dominant in the kinetics of deuterium evolution from thicker TiD y films. The dominant TDMS peak at approx. Tm = 670 K, attributed to this process, is characterized by ED = 1.49 eV.

Lisowski, Wojciech; Keim, Enrico G.; Kaszkur, Zbigniew; Smithers, Mark A.

2008-02-01

225

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

226

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

227

High temperature experiments on a 4 tons UF6 container TENERIFE program  

SciTech Connect

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

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

1991-12-31

228

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

NASA Astrophysics Data System (ADS)

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 hydride, and when the particle size reaches a certain critical threshold value, the desorption temperatures start decreasing more rapidly with further decrease of particle size. The total drop of desorption temperature from its initial value for the as-received MgH2 to the value attained for the milled MgH2 having a particle size of ~500-600 nm is within the range 40-60 °C. The metastable ?-MgH2 hydride coexists with the stable nanocrystalline ?-MgH2 in the microstructure of the MgH2 powders ball milled for 10 h and longer. Quantitative evidence shows that two factors, namely the refined powder particle size and the ?-MgH2 phase residing within the powder particles, acting additively, are responsible for a substantial reduction of the hydrogen desorption temperature of MgH2 hydride.

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

2006-08-01

229

Water in a Polymeric Electrolyte Membrane: Sorption/Desorption and Freezing phenomena  

E-print Network

Nafion is a perfluorosulfonated polymer, widely used in Proton Exchange Membrane Fuel Cells. This polymer adopts a complex structural organisation resulting from the microsegregation between hydrophobic backbones and hydrophilic sulfonic acid groups. Upon hydration appear water-filled channels and cavities, in which are released the acidic protons to form a solution of hydronium ions in water embedded in the polymer matrix. Below 273 K, a phenomenon of water sorption/desorption occurs, whose origin is still an open question. Performing neutron diffraction, we monitored the quantity of ice formed during the sorption/desorption as a function of temperature down to 180 K. Upon cooling, we observe that ice forms outside of the membrane and crystallises in the hexagonal Ih form. Simultaneously, the membrane shrinks and dehydrate, leading to an increase of the hydronium ions concentration inside the matrix. Reversibly, the ice melts and the membrane re-hydrate upon heating. A model of solution, whose freezing point varies with the hydronium concentration, is proposed to calculate the quantity of ice formed as a function of temperature. The quantitative agreement between the model and experimental data explains the smooth and reversible behavior observed during the sorption or desorption of water, pointing out the origin of the phenomena. The proposed picture reconciles both confinement and entropic effects. Other examples of water filled electrolyte nano-structures are eventually discussed, in the context of clarifying the conditions for water transport at low temperature.

Marie Plazanet; Francesco Sacchetti; Caterina Petrillo; Bruno Deme; Paolo Bartolini; Renato Torre

2013-05-02

230

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 ...

231

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

232

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

SciTech Connect

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

Palmer, C.R.

1996-04-01

233

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

SciTech Connect

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

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

1983-06-01

234

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

235

Integrated field emission array for ion desorption  

SciTech Connect

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

236

High-speed thermo-microscope for imaging thermal desorption phenomena  

NASA Astrophysics Data System (ADS)

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

Staymates, Matthew; Gillen, Greg

2012-07-01

237

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

238

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

PubMed Central

We report on the direct consequences of reversible water adsorption on the optical performance of silica-based nanoporous antireflective (AR) coatings as they are applied on glass in photovoltaic and solar thermal energy conversion systems. In situ UV-VIS transmission spectroscopy and path length measurements through high-resolution interferometric microscopy were conducted on model films during exposure to different levels of humidity and temperature. We show that water adsorption in the pores of the film results in a notable increase of the effective refractive index of the coating. As a consequence, the AR effect is strongly reduced. The temperature regime in which the major part of the water can be driven-out rapidly lies in the range of 55°C and 135°C. Such thermal desorption was found to increase the overall transmission of a coated glass by ~ 1%-point. As the activation energy of isothermal desorption, we find a value of about 18?kJ/mol. Within the experimental range of our data, the sorption and desorption process is fully reversible, resulting in optical breathing of the film. Nanoporous AR films with closed pore structure or high hydrophobicity may be of advantage for maintaining AR performance under air exposure. PMID:25307536

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

2014-01-01

239

Mercury recovery from cold cathode fluorescent lamps using thermal desorption technology.  

PubMed

Cold cathode fluorescent lamps (CCFLs) are globally used components of high technology products. A large amount of mercury in waste CCFLs is being recovered by thermal desorption technology in Taiwan. However, the complexity of the samples affects the thermal desorption efficiency and increases costs. This study identifies the mercury release behaviour of amalgam, phosphor and mercury-containing components as well as waste CCFLs by bench scale thermal desorption test. The results show that the mercury was released from amalgam and mercury/fluorescent powder from a real treatment plant at temperatures between 550 degrees C to 850 degrees C, which is much higher than from cinnabar at 300 degrees C to 380 degrees C and that of pure mercury, high pressure mercury lamps, and fluorescent tubes containing mercury/fluorescent-powder at 50 degrees C to 250 degrees C. In addition, the experiment also showed the mercury release peak of the mercury/fluorescent powders from a real treatment plant occurs at much higher temperatures than that of commercial phosphor at 50 degrees C to 200 degrees C. Thus, complete separation of the cracked CCFLs is necessary to effectively recover phosphor and mercury at low financial and energy cost. PMID:19723829

Chang, T C; Chen, C M; Lee, Y F; You, S J

2010-05-01

240

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

241

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

PubMed

We report on the direct consequences of reversible water adsorption on the optical performance of silica-based nanoporous antireflective (AR) coatings as they are applied on glass in photovoltaic and solar thermal energy conversion systems. In situ UV-VIS transmission spectroscopy and path length measurements through high-resolution interferometric microscopy were conducted on model films during exposure to different levels of humidity and temperature. We show that water adsorption in the pores of the film results in a notable increase of the effective refractive index of the coating. As a consequence, the AR effect is strongly reduced. The temperature regime in which the major part of the water can be driven-out rapidly lies in the range of 55°C and 135°C. Such thermal desorption was found to increase the overall transmission of a coated glass by ~ 1%-point. As the activation energy of isothermal desorption, we find a value of about 18?kJ/mol. Within the experimental range of our data, the sorption and desorption process is fully reversible, resulting in optical breathing of the film. Nanoporous AR films with closed pore structure or high hydrophobicity may be of advantage for maintaining AR performance under air exposure. PMID:25307536

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

2014-01-01

242

The mathematical model of insulin desorption from the bioactive, fibrous artificial store.  

PubMed

The aim of this study was to study insulin desorption from fibrous insulin artificial store in vitro as well as in vivo, with the intention to define a mathematical model that would describe this process. Release profile of cylindrical fibrous matrixes for various insulin concentrations, desorption temperatures, time periods, and pH were presented. Change of insulin concentration in the fibers and the effect of insulin release were discussed. This model was also used to predict the optimal conditions of the release process. Possibility of predicting the effect of the fibrous store design parameters (fibre radius, amount of bonded insulin, fiber type) on the resulting insulin release rate was the major advantage of this mathematical model. Also, taking all the relevant conditions regarding these experiments into consideration, by the application of mathematical model, the diffusion coefficient during insulin release was determined. PMID:16826597

Medovic, Adela; Skundric, Petar; Kostic, Mirjana; Pajic-Lijakovic, Ivana

2006-12-01

243

Continuous electron stimulated desorption using a ZrO2/Ag permeation membrane  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

245

The kinetics of CO desorption from Ni(110)  

NASA Astrophysics Data System (ADS)

The kinetics of CO desorption from clean Ni(110) have been measured by thermal desorption mass spectrometry (TDMS) using the method of variation of heating rates. Analysis of the desorption spectra gives the coverage dependence of the preexponential factor ?d, and the activation energy Ed, of the desorption rate constant. For 0desorption kinetics. The experimental results for ?d(?) are compared with those predicted for desorption by three precursor mechanisms and for desorption of a lattice gas with lateral interactions.

Feigerle, C. S.; Desai, S. R.; Overbury, S. H.

1990-07-01

246

More realistic soil cleanup standards with dual-equilibrium desorption.  

PubMed

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

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

2002-01-01

247

Testosterone sorption and desorption: Effects of soil particle size.  

PubMed

Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay>silt>sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36-65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles like clays have less potential for desorption. The results provide indirect evidence on the colloid (clay)-facilitated transport of hormones (micro-pollutants) in soil environments. PMID:25108102

Qi, Yong; Zhang, Tian C; Ren, Yongzheng

2014-08-30

248

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

NASA Astrophysics Data System (ADS)

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

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

249

Computer program for afterheat temperature distribution for mobile nuclear power plant  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

250

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. PMID:24349927

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

2013-01-01

251

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

252

A Time Domain Mixed-Mode Temperature Sensor with Digital Set-Point Programming  

Microsoft Academic Search

To realize the on-chip temperature monitoring of VLSI chips, an accurate time domain mixed-mode CMOS temperature sensor based on delay lines is proposed. Without any bipolar transistor, a temperature sensor composed of single delay line is utilized to generate the delay time proportional to the measured temperature. A succeeding multiplexer (MUX), instead of conventional voltage\\/current DAC or external resistor, along

Poki Chen; Chun-Chi Chen; Tuo-Kuang Chen; Shi-Wei Chen

2006-01-01

253

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

254

Microchannel membrane separation applied to confined thin film desorption  

SciTech Connect

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

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

2006-08-15

255

Salt Tolerance of Desorption Electrospray Ionization (DESI)  

SciTech Connect

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

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

2007-01-01

256

Redox transformations in desorption electrospray ionization  

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

257

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

USGS Publications Warehouse

Coal desorption techniques typically use the U.S. Bureau of Mines (USBM) canister-desorption method as described by Diamond and Levine (1981), Close and Erwin (1989), Ryan and Dawson (1993), McLennan and others (1994), Mavor and Nelson (1997) and Diamond and Schatzel (1998). However, the coal desorption canister designs historically used with this method have an inherent flaw that allows a significant gas-filled headspace bubble to remain in the canister that later has to be compensated for by correcting the measured desorbed gas volume with a mathematical headspace volume correction (McLennan and others, 1994; Mavor and Nelson, 1997).

Barker, Charles E.; Dallegge, Todd A.

2005-01-01

258

TREATMENT OF HAZARDOUS PETROLEUM CONTAMINATED SOILS BY THERMAL DESORPTION TECHNOLOGIES  

EPA Science Inventory

Spills, leaks, and accidental discharges of petroleum products have contaminated soil at thousands of sites in the United States. ne remedial action technique for treating petroleum contaminated soil is the use of thermal desorption technologies. his paper describes key elements ...

259

Hydrogen Desorption and Adsorption Measurements on Graphite Nanofibers  

NASA Technical Reports Server (NTRS)

Graphite nanofibers were synthesized and their hydrogen desorption and adsorption properties are reported for 77 and 300 K. Catalysts were made by several different methods including chemical routes, mechanical alloying and gas condensation.

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

1998-01-01

260

Modeling arsenic desorption from herbicide-contaminated soils.  

PubMed

The application of arsenical herbicides has created legacy environmental problems by contaminating soil in some agricultural areas and at various industrial sites. Numerous previous studies have suggested that the adsorption of arsenic by common soil components is largely controlled by kinetic factors. Four arsenic-contaminated soil samples collected from industrial sites were characterized and subjected to sequential leaching using a synthetic acid rain solution in order to study the release of arsenic. A dual-site numerical sorption-desorption model was constructed that describes arsenic desorption from these soils in terms of two different release mechanisms: Release from type I (equilibrium) and type II (kinetic) sorption sites. Arsenic held on both type I and II sorption sites is accessible through extensive acid rain leaching. Arsenic desorption from these sites follows a linear Kd model; the manner of approaching the Kd model, however, differs. Arsenic desorption from type I sites reached equilibrium with the aqueous phase under the physical environment provided by the experiment (shaking for 24 h at 25 degrees C), while desorption from type II sites followed a first-order kinetic pattern when approaching equilibrium. During synthetic acid rain sequential leaching of the soils, type I sites released their sorbed arsenic rapidly and subsequent desorption was dominated by the kinetic release of arsenic from type II sites. This shift in desorption mechanism dominance generated data corresponding to two intersecting straight lines in the n-logC dimension for all four soils. The dual-site desorption model was solved analytically and proven to be successful in simulating sorption processes where two different mechanisms are simultaneously controlling the aqueous concentration of a trace element. PMID:19199372

Qi, Yongqiang; Donahoe, Rona J

2009-06-01

261

Desorption of cesium from kaolinite and illite using alkylammonium salts  

Microsoft Academic Search

This study addresses Cs+ desorption from a kaolinite (KGa-1b) and an illite (Morris, IL) by quaternary ammonium ions. The Cs+ sorption capacities on the kaolinite and illite were 14 and 24 mmol\\/kg, respectively. Desorption of Cs+ from Cs+-preloaded kaolinite and illite at different loading levels followed different trends. In general, Cs+ was more readily removed from kaolinite than from illite.

Cari Willms; Zhaohui Li; Lori Allen; Christine V Evans

2004-01-01

262

Sorption and desorption of pyrethroid insecticide permethrin on concrete.  

PubMed

Use of pesticides around residential homes is linked to contamination of urban waterways, where impervious surfaces like concrete are considered as sources or facilitators of the contamination. However, the fate of pesticides on urban hard surfaces is poorly understood. We characterized sorption and desorption of permethrin, the most used pyrethroid insecticide, on concrete surfaces, to understand its availability for contaminating runoff water. Sorption of (14)C-permethrin to concrete was rapid, and the sorption isotherm was linear, with surface area-normalized K(d) of 1.91 ± 0.1 mL/cm(2). When small permethrin-treated concrete cubes (14 × 14 × 8 mm) were subjected to 300 h sequential desorption, both the parent compound and total (14)C showed an initial rapid desorption, followed by prolonged slow desorption. Meanwhile, permethrin became more resistant to desorption as the pesticide contact time on the concrete increased. When desorption was performed 1 and 7 d after the treatment, the desorbed permethrin after 300 h was 34.1 ± 3.2% and 23.7 ± 1.1% of the spiked amount, respectively, as compared to 56.2 ± 6.1% for the freshly spiked samples. The decreased desorption was partially attributed to permethrin decomposition on the alkaline concrete. However, even after 300 h, over 20% of the applied (14)C still remained in the concrete. Therefore, when pesticide-treated concrete surfaces come in contact with runoff water, elevated concentrations may be expected initially, while the extended desorption implies a potential for sustained contamination. PMID:21133424

Jiang, Weiying; Gan, Jay; Haver, Darren

2011-01-15

263

Kinetics of petroleum generation and cracking by programmed-temperature closed-system pyrolysis of Toarcian Shales  

Microsoft Academic Search

Primary kerogen-to-petroleum and secondary oil-to-gas conversion processes in marine source rocks have been studied contemporaneously by programmed-temperature closed-system (MSSV) pyrolysis of Toarcian Shale concentrates at heating rates of 0.1, 0.7 and 5.0K min?1 in the temperature range of 300–610°C. All pyrolysates were analysed by single-step on-line gas chromatography. The cumulative evolution profiles of liquid and gaseous compounds were deconvoluted into

V. Dieckmann; H. J. Schenk; B. Horsfield; D. H. Welte

1998-01-01

264

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

USGS Publications Warehouse

Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.

Delaney, P.T.

1988-01-01

265

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

SciTech Connect

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

Zaczek, M.; /Fermilab

1997-08-11

266

Optimizing contaminant desorption and bioavailability in dense slurry systems. 1. Rheology, mechanical mixing, and PAH desorption.  

PubMed

Intermittently mixed batch reactor (IMBR) systems were employed to evaluate the effects of mechanical mixing and corresponding power consumption on rates of phenanthrene desorption from natural and synthetic model sorbent phases to the aqueous phase in dense slurry reactors. Sorbent slurries comprising 57-67% (w/w) solids exhibited non-Newtonian (pseudoplastic) fluid behaviors, with apparent viscosities varying with shear rate. Dimensionless power numbers varied inversely with the Reynolds number under laminar flow conditions, indicating that small increases in mixing revolution number and auger size effect significant increases in power and torque requirements for the mechanical mixing of dense slurries. Rates of release of phenanthrene associated with rapidly desorbing or labile fractions of sorbent organic matter (SOM) to the aqueous phase were markedly enhanced by relatively low-level auger mixing, but significantly less further enhancement was observed as higher levels of mixing were applied. Conversely, desorption of phenanthrene associated with slowly desorbing or resistant fractions of SOM was relatively unaffected by auger mixing, being limited as it is by slow intraparticle-scale diffusion processes that are not enhanced by reactor-scale mixing. The experimental results lead to and support a conclusion that auger mixing at relatively low intensity is an attractive strategy for optimizing dense slurry reactor systems for remediation of hydrophobic organic contaminants associated with labile (rapidly desorbing) fractions of SOM with respect to performance efficiency and cost-effectiveness. PMID:15871263

Weber, Walter J; Kim, Han S

2005-04-01

267

Data quality in tissue analysis using desorption electrospray ionization.  

PubMed

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

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

2011-10-01

268

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

SciTech Connect

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

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

1996-10-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

270

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

271

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

272

Ground-Based Measurements of Mesosphere Temperature and Gravity Wave Structure as Part of the TIMED-CEDAR Collaborative Program  

NASA Astrophysics Data System (ADS)

Ground-based observations of the mesosphere and lower thermosphere (MLT) region provide an effective and complementary component to the TIMED-CEDAR research program. As part of this collaboration two sensitive CCD imaging systems, developed at Utah State University, are being used to investigate two key aspects of mesospheric dynamics: (a) seasonal, diurnal and wave-induced variability in mesospheric temperatures at the ~87 and 94 km level using measurements of the near infrared OH and O2(0,1) airglow emissions, and (b) the occurrence and properties of short-period (< 1 hour) gravity waves over the ~80-100 km region using all-sky, multi-wavelength airglow observations. The temperature measurements are being conducted from Maui, HI (20.8 N) alongside the University of Illinois Wind/Temperature lidar as part of the Maui-MALT program. Over 130 nights of data have been obtained since October 2001 providing detailed information on low-latitude mesospheric temperature and its fluctuations of importance to TIMED validation. The small-scale gravity wave measurements are being conducted from Bear Lake Observatory, UT (41.6 N) as part of a chain of imagers designed to investigate the sources and dynamics of short-period waves over the Rocky Mountains which may act to significantly influence the regional mesospheric structure. Examples of the ongoing measurements and data analysis, focusing on the seasonal and nocturnal temperature variability and the gravity wave occurrence frequency during the first 6-months of TIMED operations, will be presented. It is planned to deploy a third imaging system near Ft. Collins, CO to complement ongoing Wind/Temperature lidar and radar measurements.

Taylor, M. J.; Zhao, Y.; Taori, A.; Chu, X.

2002-12-01

273

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

274

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...

275

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

SciTech Connect

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

Song, Chunshan; Schobert, H.H.

1993-02-01

276

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

PubMed

This study reports of the novel water-induced shape-memory of bioabsorbable poly(D,L-lactide). We have developed an orientation-based programming process that generates an ability for poly(D,L-lactide) to transform its shape at 37°C in an aqueous environment without external energy and to adapt to a predefined stress level by stress generation or relaxation. In this orientation-programming process, polymer material is deformed and oriented at an elevated temperature and subsequently cooled down while retaining its deformed shape, tension, and polymer chain entanglements. At body temperature and in an aqueous environment, the shape-memory is activated by the plasticizing effect of water molecules diffused into the polymer matrix causing an entropy-driven directed relaxation of oriented and preloaded polymer chains. This plasticizing effect is clearly seen as a decrease of the onset glass transition temperature by 10-13°C. We found that ?-irradiation used for sterilizing the orientation-programmed materials strongly affected the shape-recovery rate, but not the recovery ratio. Both non-?-irradiated and ?-irradiated sample materials showed excellent shape-recovery ratios during a ten-week test period: 94 and 97%, respectively. The orientation-programmed materials generated a predefined load in a 37°C aqueous environment when their shape-recovery was restricted, but when external tension was applied to them, they adapted to the predefined level by stress relaxation. Our results show that functionality in terms of shape-memory can be generated in bioabsorbable polymers without tailoring the polymer chain structure thus shortening the time from development of technology to its utilization in medical devices. PMID:22203516

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

2012-03-01

277

Flash desorption/mass spectrometry for the analysis of less- and nonvolatile samples using a linearly driven heated metal filament.  

PubMed

In this paper, the important issue of the desorption of less- and nonvolatile compounds with minimal sample decomposition in ambient mass spectrometry is approached using ambient flash desorption mass spectrometry. The preheated stainless steel filament was driven down and up along the vertical axis in 0.3 s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1 mm in 50 ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~10(4) °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 ?g with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. Figure ? PMID:23982934

Usmanov, Dilshadbek T; Ninomiya, Satoshi; Hiraoka, Kenzo

2013-11-01

278

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

279

Flash Desorption/Mass Spectrometry for the Analysis of Less- and Nonvolatile Samples Using a Linearly Driven Heated Metal Filament  

NASA Astrophysics Data System (ADS)

In this paper, the important issue of the desorption of less- and nonvolatile compounds with minimal sample decomposition in ambient mass spectrometry is approached using ambient flash desorption mass spectrometry. The preheated stainless steel filament was driven down and up along the vertical axis in 0.3 s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1 mm in 50 ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~104 °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 ?g with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. [Figure not available: see fulltext.

Usmanov, Dilshadbek T.; Ninomiya, Satoshi; Hiraoka, Kenzo

2013-11-01

280

Adsorption and desorption of samarium atoms on the surface of pure iridium and iridium covered with a graphite monolayer  

NASA Astrophysics Data System (ADS)

Methods of thermionic emission and thermodesorption spectroscopy (TDS) have been used to study the adsorption and condensation of samarium on the surface of pure iridium and iridium covered with a graphite monolayer (valence-saturated neutral substrate) Ir(111)-C. It is shown that at temperatures of 700 < T a < 1200 K the work function ? decreases monotonically from 5.8 to 2.7 eV and during the subsequent deposition of samarium grows slowly to 2.9 eV. It has been found that in all TDS peaks there were observed several phases of samarium. The deposition of samarium onto an Ir-C surface at 700 < T < 1700 K led to a very weak change in the thermionic current in comparison with pure iridium. At temperatures above ˜700 K, samarium is not condensed on the surface of Ir-C, but it is condensed at lower temperatures. By the method of temperature modulation, the heat of samarium desorption was determined to be E ˜ 1.9 eV upon the desorption from an Ir-C surface (at a small coverage) and ˜6 eV upon the desorption from pure Ir.

Orudzhov, A. K.; Dashdemirov, A. O.

2009-01-01

281

Measuring the stratum corneum reservoir: desorption kinetics from keratin.  

PubMed

High keratin binding and slow desorption kinetics are assumed to be responsible for the formation of the stratum corneum (SC) reservoir. We measured equilibrium binding coefficients (K(b)) and desorption rate constants (k(off)) with bovine hoof/horn keratin and six solutes with similar molecular weight (180-288 Da) and varying lipophilicities [expressed as octanol-water distribution coefficient, i.e., a partition coefficient corrected for pH (log K(pH))-0.13 to 3.8]. Two ionizable solutes within this set were tested at different pH values as degree of ionization and lipophilicity were expected to influence equilibrium binding and desorption kinetics. The unbound fraction at equilibrium varied between 18% and 93%. All solutes exhibited linear binding isotherms within the investigated concentration range. Equilibrium binding and the rate of desorption are both functions of solute lipophilicity [log K(b) = 1.23 + 0.32 log K(pH); log k(off) = 1/(25.75 + 8.35 K(pH) (0.34))]. Our results prove that slow desorption from keratin may be a major contributor to the SC reservoir. Also, they prove that reservoir formation is relevant for lipophilic solutes independent of drug class, thus allowing new options for topical pharmacotherapy. PMID:22733612

Seif, Salem; Hansen, Steffi

2012-10-01

282

Environmental controls of cadmium desorption during CO? leakage.  

PubMed

Geologic carbon sequestration represents a promising option for carbon mitigation. Injected CO(2), however, can potentially leak into water systems, increase water acidity, and mobilize metals. This study used column experiments to quantify the effects of environmental controls on cadmium desorption during CO(2) leakage in subsurface systems without ambient flow. Results show that fast leakage rates are responsible for earlier and larger amounts of Cd desorption. Long weathering time of Cd laden clay leads to low Cd desorption. Calcite content as low as 10% can mitigate the effect of pH reduction and result in zero Cd desorption. Increasing the salinity of the leaking fluid has a relatively minor effect, primarily due to the offsetting impacts of an increased extent of ion exchange and the decrease in CO(2) solubility (and therefore acidity). This work systematically quantifies, for the first time, the effects of environmental controls on Cd desorption and points to key parameters for risk assessment associated with metal mobilization during CO(2) leakage. PMID:22424591

Frye, Evan; Bao, Chen; Li, Li; Blumsack, Seth

2012-04-17

283

Influence of surface coverage on the chemical desorption process  

NASA Astrophysics Data System (ADS)

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

Minissale, M.; Dulieu, F.

2014-07-01

284

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

285

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

SciTech Connect

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

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

2008-01-01

286

Real-time studies of gallium adsorption and desorption kinetics on sapphire (0001) by grazing incidence small-angle x-ray scattering and x-ray fluorescence  

SciTech Connect

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

Wang Yiyi; Oezcan, Ahmet S.; Ludwig, Karl F. [Physics Department, Boston University, Boston, Massachusetts 02215 (United States); Bhattacharyya, Anirban [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States)

2008-05-15

287

The study of 'microsurfaces' using thermal desorption spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

288

Desorption mass spectrometry for nonvolatile compounds using an ultrasonic cutter.  

PubMed

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

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

2014-07-01

289

137Cs desorption from lichen using acid solutions  

NASA Astrophysics Data System (ADS)

Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl ( A) and HNO3 ( B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions were the most successful. Lichen desorbed with the stated solutions did not undergo structural changes. The amount of absorbed water from solutions A and B, used for desorption from lichen, in relation to the starting volume (expressed in %) showed that solution concentration did not take place. Lichen act as neutralizing agents because the pH of the lichen thallus is higher than the pH value of the solution used

?u?ulovi?, A. A.; Veselinovi?, D.; Miljani?, S. S.

2009-09-01

290

Influence of functional groups on desorption of organic compounds from carbon nanotubes into water: insight into desorption hysteresis.  

PubMed

Adsorption-desorption of nitrobenzenes, phenols, and anilines on five multiwalled carbon nanotubes (MWCNTs) with different degrees of surface oxidation were investigated to examine the influence of functional groups of both organic chemicals and CNTs on desorption hysteresis. Desorption hysteresis was not observed for nitrobenzenes, phenols, and 4-nitroaniline from all MWCNTs. Significant desorption hysteresis was observed for aniline and 4-methylaniline on surface-oxidized MWCNTs but not on unoxidized MWCNTs. Formation of an irreversible amide bond (i.e.,-CONH-) by amidation reaction of amino group of anilines with oxygen-containing groups (i.e., carboxyl or lactonic groups) on MWCNTs was observed. We proposed that desorption hysteresis could be attributed to the immobilization of organic compounds on the surface of CNTs resulting from the irreversible chemical reaction/binding. The irreversible chemical immobilization is compound functional group selective and dependent on the surface oxygen-containing groups of CNTs. Hysteresis index (HI) values of aniline or 4-methylaniline on MWCNTs increased with the amounts of oxygen-containing groups on MWCNTs. Moreover, HI values of anilines on a given oxidized MWCNT followed an order of 4-nitroaniline < 4-chloroaniline < aniline < 4-methylaniline. PMID:23848495

Wu, Wenhao; Jiang, Wei; Zhang, Weidie; Lin, Daohui; Yang, Kun

2013-08-01

291

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

292

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

293

137 Cs desorption from lichen using acid solutions  

Microsoft Academic Search

Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl (A) and HNO3 (B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was\\u000a shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions

A. A. ?u?ulovi?; D. Veselinovic; S. S. Miljanic

2009-01-01

294

Explosive desorption of icy grain mantles in dense clouds  

NASA Technical Reports Server (NTRS)

The cycling of the condensible material in dense clouds between the gas phase and the icy grain mantles is investigated. In the model studied, desorption of the ice occurs due to grain mantle explosions when photochemically stored energy is released after transient heating by a cosmic ray particle. It is shown that, depending on the grain size distribution in dense clouds, explosive desorption can maintain up to about eight percent of the carbon in the form of CO in the gas phase at typical cloud densities.

Schutte, W. A.; Greenberg, J. M.

1991-01-01

295

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

NASA Astrophysics Data System (ADS)

It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i) physisorption and (ii) chemisorption. Physisorption is associated with lower binding energies in the order of 1-10 kJ mol-1 compared to chemisorption ranging from 100 to 1000 kJ mol-1. Furthermore, chemisorption forms only monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws, however, it can be influenced by hysteresis effects. In the present experiment we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. We proved the pressure effect on physisorption for CO2, CH4 and H2O by decanting a steel and an aluminium cylinder completely. The results are in excellent agreement with a monolayer adsorption model for both cylinders. However, adsorption on aluminium (0.3 ppm and 0 ppm for CO2 and H2O) was about 20 times less than on steel (6 ppm and 30 ppm, respectively). In the climate chamber the cylinders were exposed to temperatures between -10 to +50 °C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO2 ranging from 0.0011 to 0.0133 ppm °C-1 for steel cylinders and -0.0003 to -0.0005 ppm °C-1 for aluminium cylinders. The reversed temperature dependence for aluminium cylinders is most probably due to temperature and gas consumption induced pressure changes. After correction, aluminium cylinders showed no temperature independence. Temperature coefficients for CH4, CO and H2O adsorption were, within their error bands, insignificant. These results do indicate the need for careful selection and usage of gas cylinders for high precision calibration purposes such as requested in trace gas applications.

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

2014-07-01

296

New Computer Programs Using Diurnal Temperature Time Series to Determine Streambed Percolation Velocities  

NASA Astrophysics Data System (ADS)

Streambed percolation is one of the most important routes for groundwater recharge. Among many methods, using diurnal temperature in the streambed to determine percolation velocity is one the most frequently used methods. Several numerical codes, VS2DH, SUTRA, and TOUGH2, have been developed primarily for 2D or 3D heat transport simulation and also for use in streambed percolation velocity calculation, but, with great complexity. This research simplifies percolation velocity calculation by developing new computer codes that solve the 1D heat transfer equation. Using diurnal temperature data, percolation velocity can be determined easily to each day of the monitoring period. More percolation velocity data will enable more understanding for the river/groundwater interaction. This work also conducts a field test for studying streambed percolation in the Choshui stream, Central Taiwan. The data show the average percolation velocity at approximately 6.8×10-6 m/s.

Chen, W.; Chen, J.; Lu, W.; Huang, C.

2012-12-01

297

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

Microsoft Academic Search

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

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

2009-01-01

298

Active Oxygen Species and Mechanism for Low-Temperature CO Oxidation Reaction on a TiO 2-Supported Au Catalyst Prepared from Au(PPh 3)(NO 3) and As-Precipitated Titanium Hydroxide  

Microsoft Academic Search

The active oxygen species and mechanism for catalytic CO oxidation with O2 on a highly active TiO2-supported Au catalyst (denoted as Au\\/Ti(OH)*4), which was prepared by supporting a Au–phophine complex on as-precipitated wet titanium hydroxide followed by calcination at 673 K, have been studied by means of oxygen isotope exchange, O2 temperature-programmed desorption (O2 TPD), electron spin resonance (ESR), and

Haichao Liu; Alexander I. Kozlov; Anguelina P. Kozlova; Takafumi Shido; Kiyotaka Asakura; Yasuhiro Iwasawa

1999-01-01

299

Desorption or `Surface Melting' of Lubricant Films  

Microsoft Academic Search

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

D. Tabor

1941-01-01

300

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

NASA Astrophysics Data System (ADS)

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

Harrison, D.; Thonhauser, T.

2014-09-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

302

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

NASA Astrophysics Data System (ADS)

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

Terashita, Masashi; Fukada, Satoshi

2011-10-01

303

Positron and thermal desorption studies on He ion implanted nuclear graphite  

NASA Astrophysics Data System (ADS)

The positron beam Doppler Broadening (DB) and Thermal Helium Desorption Spectroscopy (THDS) techniques are applied to study the behavior of radiation induced point defects in IG-110 nuclear graphite. The defects are introduced by irradiation at room temperature with 200keV He+ at doses ranging from 1015 to 1017 He/cm2. In the thermal desorption spectroscopy, the release of He+ is observed between 500K and 800K. With increasing He+ implantation dose, the fraction of He+ desorbed decreases from 27% to 3%. In the DB-curves showing the S parameter values versus positron implantation depth, the derived vacancy type defect distribution are in accordance with those obtained by SRIM calculations. Subsequent annealing of the implanted samples in steps of 100K for 5 minutes up to 1200K shows a distinct decrease of the S parameter value to its reference value between 500K and 700K. This temperature interval corresponds to the literature values for single vacancy migration energy of 1-2eV.

Hu, Z.; Li, Z.; Zhou, Z.; Shi, C.; Schut, H.; Pappas, K.

2014-04-01

304

Photoinduced desorption of sulfur from gold nanoparticles loaded on metal oxide surfaces.  

PubMed

We now report photoinduced sulfur desorption from the surfaces of Au nanoparticles loaded on metal oxides. This reaction occurs in water at ordinary temperature and pressure. Nanometer-sized Au particles have been formed on the surfaces of various metal oxides by deposition-precipitation (Au/oxides). Elemental sulfur (S8) is selectively adsorbed on the Au nanoparticle surfaces of Au/oxides in an atomic state at a coverage of (theta) 1/3. Irradiation (lambdaex > 300 nm) of the sulfur adsorbed Au/anatase TiO2 in water has led to reductive desorption of the sulfurs at room temperature. Electrochemical measurements using Au/oxides indicate that the driving force for this reaction is the photoinduced upward shift of Fermi energy of the metal oxide-supported Au nanoprticles. This study will open up a novel and wide application of heterogeneous photocatalysis for thermal catalysts. PMID:15584715

Tada, Hiroaki; Soejima, Tetsuro; Ito, Seishiro; Kobayashi, Hisayoshi

2004-12-15

305

Distinguishibility of Oxygen Desorption From the Surface Region with Mobility Dominant Effects in Nanocrystalline Ceria Films  

SciTech Connect

We present an investigation of oxygen (18O) uptake measurements in 1 ?m thick nanocrystalline ceria films grown on single crystal Al?O? (0001) by nuclear reaction analysis (NRA). Oxygen uptake measurements were carried out in the temperature range of 200 0C-600 0C at a background 18O pressure of 4.0 x 10-6 Torr. Average grain-size in the as-grown films, synthesized by sol-gel process was ~ 3 nm confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) measurements. From the diffusion depth profiles, changes in intensity and slopes in surface and interface regions indicate dominating oxygen mobility effects. Oxygen desorption is clearly distinguishable in the film surface region as a result of shift in the oxygen peak intensity. It is argued that high defect density in nanocrystalline ceria which is associated with nano-grain surface combined with intermediate temperature reducing environment triggers multiple processes like diffusion, desorption and exchange interaction. The promising nature of NRA is realized as an effective tool to acquire the depth-dependent information regarding such complex reactions that exists in nanocrystalline environment.

Saraf, Laxmikant V.; Shutthanandan, V.; Zhang, Yanwen; Thevuthasan, Suntharampillai; Wang, Chong M.; El-Azab, Anter; Baer, Donald R.

2004-11-15

306

Ab initio statistical mechanics of surface adsorption and desorption. I. H2O on MgO ,,001... at low coverage  

E-print Network

Ab initio statistical mechanics of surface adsorption and desorption. I. H2O on MgO ,,001... at low of the chemical potential as a function of coverage and temperature. It avoids all statistical mechanical approximations, except for the use of classical statistical mechanics for the nuclei, and assumes nothing

Alfè, Dario

307

A study of the formation of cluster ions from metal acetates using plasma desorption mass spectrometry  

E-print Network

A novel application of desorption/ionization methods of mass spectrometry, e. g. plasma desorption mass spectrometry (PDMS), is the analysis of both the composition and structure of solid materials in one experiment. Cluster ions emitted from...

Mendez Silvagnoli, Winston Reinaldo

2012-06-07

308

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

E-print Network

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

Sparks, Donald L.

309

USING METHANOL-WATER SYSTEMS TO INVESTIGATE PHENANTHRENE SORPTION-DESORPTION ON SEDIMENT  

EPA Science Inventory

Sorption isotherm nonlinearity, sorption-desorption hysteresis, slow desorption kinetics, and other nonideal phenomena have been attributed to the differing sorptive characteristics of the natural organic matter (NOM) polymers associated with soils and sediments. A conceptualizat...

310

INITIAL SCREENING OF THERMAL DESORPTION FOR SOIL REMEDIATION  

EPA Science Inventory

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

311

INITIAL SCREENING OF THERMAL DESORPTION FOR SOIL REMEDIATION  

EPA Science Inventory

The purpose of this paper is to present procedures for collecting and evaluating key data that affect the potential application of thermal desorption for a specific site. hese data are defined as "critical success factors". he screening procedure can be used to perform an initial...

312

LASER DESORPTION IONIZATION OF ULTRAFINE AEROSOL PARTICLES. (R823980)  

EPA Science Inventory

On-line analysis of ultrafine aerosol particle in the 12 to 150 nm size range is performed by laser desorption/ionization. Particles are size selected with a differential mobility analyzer and then sent into a linear time-of-flight mass spectrometer where they are ablated w...

313

Atomic hydrogen desorption from thin palladium hydride films  

NASA Astrophysics Data System (ADS)

It has been proved that hydrogen atoms desorb from the surface of a decomposing thin palladium hydride film. A thin gold film deposited and sintered in situ was used as a selective adsorbent for atomic hydrogen. The TDMS (thermal desorption mass spectrometry) technique was applied to detect the adsorption of hydrogen on gold and to determine the amount adsorbed.

Lisowski, W.; Nowicka, E.; Wolfram, Z.; Du?, R.

1988-01-01

314

Influence of surface coverage on the chemical desorption process  

E-print Network

In cold astrophysical environments, some molecules are observed in the gas phase whereas they should have been depleted, frozen on dust grains. In order to solve this problem, astrochemists have proposed that a fraction of molecules synthesized on the surface of dust grains could desorb just after their formation. Recently the chemical desorption process has been demonstrated experimentally, but the key parameters at play have not yet been fully understood. In this article we propose a new procedure to analyze the ratio of di-oxygen and ozone synthesized after O atoms adsorption on oxidized graphite. We demonstrate that the chemical desorption efficiency of the two reaction paths (O+O and O+O$_2$) is different by one order of magnitude. We show the importance of the surface coverage: for the O+O reaction, the chemical desorption efficiency is close to 80 $\\%$ at zero coverage and tends to zero at one monolayer coverage. The coverage dependence of O+O chemical desorption is proved by varying the amount of pre-...

Marco, Minissale

2014-01-01

315

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

EPA Science Inventory

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

316

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

EPA Science Inventory

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

317

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

EPA Science Inventory

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

318

Water absorption and desorption in shuttle ablator and insulation materials  

NASA Technical Reports Server (NTRS)

Shuttle systems ablator and insulation materials underwent water soak with subsequent water desorption in vacuum. Water accumulation in these materials after a soak for 24 hours ranged from +1.1% for orbiter tile to +161% for solid rocket booster MSA-1. After 1 minute in vacuum, water retention ranged from none in the orbiter tile to +70% for solid rocket booster cork.

Whitaker, A. F.; Smith, C. F.; Wooden, V. A.; Cothren, B. E.; Gregory, H.

1982-01-01

319

Ontogeny of Water Sorption-Desorption in the Perinatal Rat  

Microsoft Academic Search

In mammals, birth marks a transition to a cold and gaseous environment that requires rapid physiologic adaptations limiting heat and water loss. In this study, the perinatal Sprague-Dawley rat was utilized as a model to study the behavior of water binding to the external body surface following birth. Water sorption and desorption were quantified by measurement of skin surface capacitance

Randall R. Wickett; Julie L. Mutschelknaus; Steven B. Hoath

1993-01-01

320

Environmental controls of Cadmium desorption during CO2 leakage  

NASA Astrophysics Data System (ADS)

In an effort to reduce greenhouse gas (GHG) emissions related to fossil fuel burning, geologic carbon sequestration represents an opportunity for long-term storage of carbon dioxide. One particular concern related to carbon sequestration is the migration of CO2 into overlying surface and groundwater resources, therefore deteriorating water quality. This work aims to understand and quantify the impact of CO2 leakage on cadmium mobilization through desorption from clay minerals using a series of column leaching experiments. Experimental variables include mineral composition (the presence or lack of pH buffering minerals such as calcite), the leakage rate, as well as the salinity of intruding CO2-saturated water. Experimental results suggest that with the CO2 leakge, pH in general drops by one to two units. The total amount of cadmium desorption vary under different environmental conditions. With 10% of calcite as the buffering mineral, the Cd(II) does not desorb at all, while it does desorb when there is no calcite present. The amount of cadmium desorption in a column with a larger leakage rate is larger than that from a column with a slower leakage rate by a factor of four. Higher salinity of leaking fluid leads to a smaller amount of dissolved CO2, higher pH, and therefore lower amount of Cd desorption. These results provide insights into key environmental parameters that determine the impact of CO2 leakage on water quality.

Frye, E. J.; Li, L.; Blumsack, S.

2011-12-01

321

Letters to Analytical Chemistry Surface-Enhanced Transmission Mode Desorption  

E-print Network

laser desorption, the use of plasmas, and extraction methods.3 The most compelling motivations reported to address this issue and exploits the addition of specific reagents to the spray solution prominently utilized ambient ioniza- tion methods.7 In the DESI process, ions are produced by directing

Gelb, Michael

322

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

EPA Science Inventory

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

323

Thermogravimetric Study on Oxygen Adsorption\\/Desorption Properties of Double Perovskite Structure Oxides REBaCo 2 O 5+? (RE = Pr, Gd, Y)  

Microsoft Academic Search

The oxygen adsorption\\/desorption properties of double perovskite structure oxides PrBaCo2O5+?, GdBa-Co2O5+? and YBaCo2O5+? were investigated by the thermogravimetry (TG) method in the temperature range of 400 ? 900 °C. The calculated oxygen adsorption\\/desorption surface reaction rate constants ka and kd of these double perovskite structure oxides were larger than the commonly used cubic perovskite oxides, such as Ba0.95Ca0.05Co0.8Fe0.2O3-? and Ba0.5

Hao Haoshan; Zheng Lu; Wang Yingfang; Liu Shijiang; Hu Xing

2007-01-01

324

Characterization of graphite-supported palladium-cobalt catalysts by temperature-programmed reduction and magnetic measurements  

SciTech Connect

Graphite-supported cobalt, palladium, and cobalt-palladium systems were prepared by a simple impregnation technique and submitted to hydrogen reduction in a temperature-programmed mode. Using X-ray diffraction to define the structure of the calcined precursors, magnetic measurements to determine the amount of metallic cobalt formed after reduction, and analysis of the gaseous medium during the reduction, a general model for the reduction of the graphite supported catalysts has been suggested. At room temperature, both pure PdO and PdO associated with Co{sub 3}O{sub 4} are reduced to the metallic state. In the case of bimetallic systems, a fraction of Co{sub 3}O{sub 4} in close proximity or interfaced with PdO can be reduced to the metallic state and to COO species, demonstrating a strong catalytic effect of palladium on the reduction of cobalt oxides. At temperatures between 298 and 500 K, depending on the catalyst formulation, the presence of metallic palladium promotes the reduction of a large fraction of oxidized cobalt. At higher reduction temperature, at least two competitive phenomena were detected: direct reduction of the residual oxidized cobalt by the graphite, leading to carbon monoxide and dioxide formation, and hydrogasification of the graphite catalyzed by the supported metals, leading mainly to methane formation. Together with a possible short-range palladium-activated hydrogen migration, at low and moderate temperatures, long-range migration of particles is necessary to explain the observations. These migrations, in turn, favor the formation of bimetallic particles, after reduction at 773 K. 53 refs., 5 figs., 3 tabs.

Noronha, F.B.; Schmal, M. [Universidade Federal do Rio de Janeiro (Brazil)] [Universidade Federal do Rio de Janeiro (Brazil); Nicot, C. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [and others] [Institut de Recherches sur la Catalyse, Villeurbanne (France); and others

1997-05-01

325

Determination of the carbon isotopic composition of whole/intact biological specimens using at-line direct thermal desorption to effect thermally assisted hydrolysis/methylation.  

PubMed

In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography-combustion isotope-ratio mass spectrometry (GC/C-IRMS) analysis of whole/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped programmed-temperature vaporizer (PTV) liners to the PTV injector and chemical derivatisation (thermally assisted hydrolysis/methylation; THM) such that a profile of a cellular fatty acids is obtained. Flow-cytometric sorted microalgae and handpicked zooplankton are used as samples with trimethylsulfonium hydroxide (TMSH) as methylating reagent. A major advantage of this novel approach over the Curie-point technique is the automation of the total procedure, which allows unattended analysis of large sample series. The profiles and delta(13)C carbon isotopic signatures of the fatty acid methyl esters (FAMEs) produced are very similar to those obtained using the Curie-point flash pyrolysis method. It is shown that algal samples must be kept no longer than 48 h in the DTD sample tray prior to the THM-analysis in order to maintain the integrity of their FAME profile. PMID:17897655

Akoto, Lawrence; Vreuls, René J J; Irth, Hubertus; Floris, Virgilio; Hoogveld, Hans; Pel, Roel

2008-04-01

326

Investigations into ultraviolet matrix-assisted laser desorption  

SciTech Connect

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

Heise, T.W.

1993-07-01

327

Climate change report on atmospheric temperatures; NASA science programs lack money and balance  

NASA Astrophysics Data System (ADS)

The U.S. Climate Change Science Program issued on 2 May the first of 21 climate change assessment reports being prepared by the federal government. The report finds that there no longer exists disagreement between data that showed warming at the Earth's surface but not above it. Some people had cited such a discrepancy to question the validity of climate models. Errors in data from satellites and weather balloons had led some researchers to believe that the troposphere had not been warming along with the planet surface, but now these errors have been corrected, according to the report. Researchers to believe that the troposphere had not been warming along with the planet surface, but now these errors have been corrected, according to the report. Researchers have also acquired new data sets that do not show the disagreement in warming.

Zielinski, Sarah

2006-05-01

328

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

PubMed

The development of a method for screening of organic compounds with a wide range of physico-chemical properties in water, based on dual stir bar sorptive extraction coupled with thermal desorption and gas chromatography-mass spectrometry (dual SBSE-TD-GC-MS) is described. The investigated water sample is divided into two aliquots and extracted with stir bar sorptive extraction at two different conditions: using addition of methanol or sodium chloride, respectively. Following extraction, the two stir bars are inserted into the same glass thermal desorption liner and are simultaneously desorbed and analysed by GC-MS. The method optimisation was performed using 45 environmentally harmful substances with different volatilities (boiling point from 193 to 495°C), polarity (logK(ow) from 2.17 to 8.54) and acido-basic properties. The majority of model compounds was selected from the EU list of priority substances in the field of water policy and from the US EPA method 625, respectively. Optimisation was performed for extraction parameters (sample volume, extraction time, stirring rate, addition of modifiers) as well as for the thermal desorption conditions (desorption flow, desorption time, cryofocusing temperature). Performance characteristics (recovery, repeatability, carryover, linearity, limits of detection and quantification) were determined for the optimised method. An example of analysis of a contaminated groundwater sample is presented. PMID:22099662

Tölgyessy, Peter; Vrana, Branislav; Krascsenits, Zoltán

2011-12-15

329

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

330

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

NASA Technical Reports Server (NTRS)

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

Lee, A. Y.

1967-01-01

331

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

SciTech Connect

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

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

1986-01-01

332

Sorption and Desorption of Atrazine and Diuron onto Primary Soil Particles  

E-print Network

to receiving water bodies. The objectives of this study were to: · Compare sorption and desorption behavior can represent water dispersible colloids (WDCs) under field conditions. Sorption and desorptionSorption and Desorption of Atrazine and Diuron onto Primary Soil Particles Peng Wang and Arturo A

Keller, Arturo A.

333

Kinetic parameters obtained from area integration of single peak thermal desorption spectra  

Microsoft Academic Search

This paper presents a method to analyze thermal desorption spectra based on area integration of the desorption peaks. An expression is derived for the rate of desorption in a thermal-activated process which permits evaluation of the rate from the intensity and area values for each point of the curve. Arrhenius plots of the rate data yield the activation energy and

A. L. Cabrera

1990-01-01

334

Sorption and desorption characteristics of a packed bed of clay-CaCl{sub 2} desiccant particles  

SciTech Connect

Desiccants can be used in conjunction with solar energy to provide a viable alternative to traditional air conditioning techniques. A desiccant consisting of clay and calcium chloride was developed and tested using multiple sorption and desorption cycles. During sorption, inlet air temperatures from 23 to 36 C with corresponding relative humidities of 42-66% were tested. Additionally, superficial air velocities from 0.17 to 0.85 m/s were tested. During desorption, inlet air temperatures from 50 to 57 C and superficial air velocities of approximately 0.30 and 0.60 m/s were tested. A regression equation was determined for the mass of water sorbed by the clay-CaCl2 desiccant with a R{sup 2} value of 0.917. The desorption data was regressed to an exponential function and significant k-values were determined. An equation for pressure drop through the desiccant was determined and compared to existing models. The desiccant was found to perform well during the repeated test cycles though small masses of desiccant were lost due to surface disintegration of the desiccant spheres. (author)

Tretiak, C.S.; Abdallah, N. Ben [Department of Process Engineering and Applied Science, Dalhousie University, P.O. Box 1000, Halifax, Nova Scotia (Canada)

2009-10-15

335

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

336

Improving low temperature properties of synthetic diesel fuels derived from oil shale. Alternative fuels utilization program  

SciTech Connect

The ability of additives to improve the cold flow properties of shale oil derived fuels boiling in the diesel fuel range was evaluated. Because a commercial shale oil industry did not exist to provide actual samples of finished fuels, a representative range of hydroprocessed shale oil fractions was prepared for use in the additive testing work. Crude oil shale from Occidental Shale Company was fractionated to give three liquids in the diesel fuel boiling range. The initial boiling point in each case was 325/sup 0/F (163/sup 0/C). The final boiling points were 640/sup 0/F (338/sup 0/C), 670/sup 0/F (354/sup 0/C) and 700/sup 0/F (371/sup 0/F). Each fraction was hydrotreated to three different severities (800, 1200 and 1500 psi total pressure) over a Shell 324 nickel molybdate on alumina catalyst at 710 to 750/sup 0/F to afford 9 different model fuels. A variety of commercial and experimental additives were evaluated as cold flow improvers in the model fuels at treat levels of 0.04 to 0.4 wt %. Both the standard pour point test (ASTM D97) and a more severe low temperature flow test (LTFT) were employed. Reductions in pour points of up to 70/sup 0/F and improvements in LTFT temperatures up to 16/sup 0/F were achieved. It is concluded that flow improver additives can play an important role in improving the cold flow properties of future synthetic fuels of the diesel type derived from oil shale.

Frankenfeld, J.W.; Taylor, W.F.

1980-11-01

337

Desorption of PCDD/PCDF from municipal solid waste incinerator flyash under post-combustion plant conditions.  

PubMed

The influence of temperature on the levels of PCDD and PCDF remaining in, and desorbed from, a municipal solid waste incinerator flyash was investigated by heating the ash to between 200 and 400 degrees C under a simulated flue gas for four days reaction time. Considerable desorption of PCDD/PCDF from the flyash was seen at 275 degrees C and above. Maximum desorption occurred at 350 degrees C, with the equivalent of nearly eight times the total PCDD/PCDF concentration of the original flyash being lost to the vapour phase per unit mass of initial flyash. The I-TEQ value of the desorbed PCDD/PCDF was considerable, being over fourteen times that of the original flyash at 325 degrees C. The results indicate that formation of PCDD/PCDF on flyash deposits in the post-combustion plant of incinerators can result in the release of significant amounts of PCDD/PCDF to the flue gas stream. PMID:17498773

Cunliffe, Adrian M; Williams, Paul T

2007-08-01

338

Effect of internal and external conditions on ionization processes in the FAPA ambient desorption/ionization source.  

PubMed

Ambient desorption/ionization (ADI) sources coupled to mass spectrometry (MS) offer outstanding analytical features: direct analysis of real samples without sample pretreatment, combined with the selectivity and sensitivity of MS. Since ADI sources typically work in the open atmosphere, ambient conditions can affect the desorption and ionization processes. Here, the effects of internal source parameters and ambient humidity on the ionization processes of the flowing atmospheric pressure afterglow (FAPA) source are investigated. The interaction of reagent ions with a range of analytes is studied in terms of sensitivity and based upon the processes that occur in the ionization reactions. The results show that internal parameters which lead to higher gas temperatures afforded higher sensitivities, although fragmentation is also affected. In the case of humidity, only extremely dry conditions led to higher sensitivities, while fragmentation remained unaffected. PMID:25178932

Orejas, Jaime; Pfeuffer, Kevin P; Ray, Steven J; Pisonero, Jorge; Sanz-Medel, Alfredo; Hieftje, Gary M

2014-11-01

339

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

SciTech Connect

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

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

1998-08-28

340

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

DOEpatents

A furnace with two hot zones holds multiple analysis tubes. Each tube has a separable sample-packing section positioned in the first hot zone and a catalyst-packing section positioned in the second hot zone. A mass flow controller is connected to an inlet of each sample tube, and gas is supplied to the mass flow controller. Oxygen is supplied through a mass flow controller to each tube to either or both of an inlet of the first tube and an intermediate portion between the tube sections to intermingle with and oxidize the entrained gases evolved from the sample. Oxidation of those gases is completed in the catalyst in each second tube section. A thermocouple within a sample reduces furnace temperature when an exothermic condition is sensed within the sample. Oxidized gases flow from outlets of the tubes to individual gas cells. The cells are sequentially aligned with an infrared detector, which senses the composition and quantities of the gas components. Each elongated cell is tapered inward toward the center from cell windows at the ends. Volume is reduced from a conventional cell, while permitting maximum interaction of gas with the light beam. Reduced volume and angulation of the cell inlets provide rapid purgings of the cell, providing shorter cycles between detections. For coal and other high molecular weight samples, from 50% to 100% oxygen is introduced to the tubes.

LaCount, Robert B. (403 Arbor Ct., Waynesburg, PA 15370)

1993-01-01

341

Use of thermal desorption mass spectrometry for the detection of free acid impurities in pharmaceutical products.  

PubMed

A method utilizing thermal desorption mass spectrometry (TDMS) for the detection and quantitation of free acid forms in pharmaceutical drug products formulated as salts is presented. Selective detection of neutral drug forms is possible because the volatility of a drug present in its free acid form is typically much higher than that of its corresponding salt forms, which have negligible volatility even at high temperatures. Tandem mass spectrometric detection allows selective quantitation of the desired free acid drug forms without significant interferences from formulation excipients. The application of the TDMS approach is demonstrated for a sodium salt of a representative, carboxylated drug molecule. Excellent sensitivity, specificity, and adequate linearity of detector signal as a function of micrograms of free acid added were demonstrated in the presence of the sodium salt of the drug and formulation excipients. The sensitivity of the method was demonstrated at free acid levels of 0.6% w/w (6 microg absolute mass). Tablet samples were analyzed by thermal desorption EI-MS/MS with reference to external standards using a commercially available quadrupole ion trap mass spectrometer. The relative drug form stabilities in three different tablet formulations were differentiated using this method; the salt-to-free acid form conversion ranged between less than the limit of detection to near complete conversion during the stability study. PMID:16970338

Kemp, Eric A; Nelson, Eric D; Seburg, Randal A

2006-09-15

342

Kinetics of desorption of hexane from the microporous metal organic framework RPM-1  

SciTech Connect

The kinetics of desorption of hexane from the microporous metal framework RPM-1 has been studied using a pulse mass analyzer. In this method a small sample of organic liquid was injected into a heated carrier gas that passes through a packed bed of adsorbent. The change in mass of the bed with time was observed following the adsorption of the pulse. RPM-1 is a microporous material of the general formula [M3(bpdc)3(bpy)] · 4DMF · H2O, where M is either Co or Zn, bpdc is biphenyl dicarboxylate and bpy is 4,4?-bipyridine. The pores are channels of larger supercages (11 × 11 × 5 Å) connected by smaller windows of approximately 8 Å diameter. The desorption of hexane was well represented by a combination of two first order processes. Activation energies determined for the two processes over a temperature range of 373–473 K were 56 and 63 kJ/mol for RPM-1 (Co). The two activation energies are similar to isosteric heats of adsorption measured independently in earlier work at corresponding coverages. Similar values were found for RPM-1 (Zn). The pulse mass analyzer was found to be an effective way to investigate the dynamics of adsorption processes.

Smith, M.; Culp, J.T.; Bittner, E.; Parker, B. (Rutgers Univ., Piscataway, NJ); Li, J. (Rutgers Univ., Piscataway, NJ); Bockrath, B.C.

2007-11-01

343

Analysis of organic compounds in water by direct adsorption and thermal desorption. [Dissertation  

SciTech Connect

An instrument was designed and constructed that makes it possible to thermally desorb organic compounds from wet adsorption traps to a gas chromatograph in an efficient and reproducible manner. Based on this device, a method of analyzing organics in water was developed that is rapid, sensitive, and of broader scope than previously published methods. The system was applied to the analysis of compounds with a wide range of volatilities. Temperature and flow parameters were investigated and specific procedures for quantitation were established. Real samples, including tap water and well water, were also analyzed with this system. Depending on the analysis requirements, the thermal desorption instrument can be used with either packed column or high resolution open-tubular column gas chromatography. The construction plans of normal and high-resolution systems are presented along with chromatograms and data produced by each. Finally, an improved thermal desorption instrument is described. Modifications to the basic system, including splitless injection onto a capillary column, automation, dual cryogenic trapping, reduction of scale, and effluent splitting to dual detection are discussed at length as they relate to the improved instrument.

Ryan, J.P. Jr.

1980-03-01

344

Diffusion-desorption ratio of adsorbed CO and CO2 on water ice  

NASA Astrophysics Data System (ADS)

Context. Diffusion of atoms and molecules is a key process for the chemical evolution in star-forming regions of the interstellar medium. Accurate data on the mobility of many important interstellar species is often not available, however, which seriously limits the reliability of models describing the physical and chemical processes in molecular clouds. Aims: Here we aim to provide the astrochemical modeling community with reliable data on the ratio between the energy barriers for diffusion and desorption for adsorbed CO and CO2 on water ices. Methods: To this end, we used a fully atomistic, off-lattice kinetic Monte Carlo technique to generate dynamical trajectories of CO and CO2 molecules on the surface of crystalline ice at temperatures relevant for the interstellar medium. Results: The diffusion-to-desorption barrier ratios are determined to be 0.31 for CO and 0.39 for CO2. These ratios can be directly used to improve the accuracy of current gas-grain chemical models.

Karssemeijer, L. J.; Cuppen, H. M.

2014-09-01

345

Diffusion-desorption ratio of adsorbed CO and CO$_2$ on water ice  

E-print Network

Diffusion of atoms and molecules is a key process for the chemical evolution in the star forming regions of the interstellar medium. Accurate data on the mobility of many important interstellar species is however often not available and this provides a serious limitation for the reliability of models describing the physical and chemical processes in molecular clouds. Here we aim to provide the astrochemical modeling community with reliable data on the ratio between the energy barriers for diffusion and desorption for adsorbed CO and CO$_2$ on water ices. To this end, we use a fully atomistic, off-lattice kinetic Monte Carlo technique to generate dynamical trajectories of CO and CO$_2$ molecules on the surface of crystalline ice at temperatures relevant for the interstellar medium. The diffusion to desorption barrier ratios are determined to be 0.31 for CO and 0.39 for CO$_2$ . These ratios can be directly used to improve the accuracy of current gas-grain chemical models.

Karssemeijer, L J

2014-01-01

346

Diffusion barriers in the kinetics of water vapor adsorption/desorption on activated carbons  

SciTech Connect

The adsorption of water vapor on a highly microporous coconut-shell-derived carbon and a mesoporous wood-derived carbon was studied. These carbons were chosen as they had markedly different porous structures. The adsorption and desorption characteristics of water vapor on the activated carbons were investigated over the relative pressure range p/p{degree} = 0--0.9 for temperatures in the range 285--313 K in a static water vapor system. The adsorption isotherms were analyzed using the Dubinin-Serpinski equation, and this provided an assessment of the polarity of the carbons. The kinetics of water vapor adsorption and desorption were studied with different amounts of preadsorbed water for set changes in pressure relative to the saturated vapor pressure (p/p{degree}). The adsorption kinetics for each relative pressure step were compared and used to calculate the activation energies for the vapor pressure increments. The kinetic results are discussed in relation to their relative position on the equilibrium isotherm and the adsorption mechanism of water vapor on activated carbons.

Harding, A.W.; Foley, N.J.; Thomas, K.M. [Univ. of Newcastle upon Tyne (United Kingdom)] [Univ. of Newcastle upon Tyne (United Kingdom); Norman, P.R.; Francis, D.C. [CBD, Salisbury (United Kingdom)] [CBD, Salisbury (United Kingdom)

1998-07-07

347

Laser desorption mass spectrometry and small angle neutron scattering of heavy fossil materials  

SciTech Connect

The determination of the structural building blocks and the molecular weight range of heavy hydrocarbon materials is of crucial importance in research on their reactivity and for their processing. The chemically and physically heterogenous nature of heavy hydrocarbon materials, such as coals, heavy petroleum fractions, and residues, dictates that their structure and reactivity patterns be complicated. The problem is further complicated by the fact that the molecular structure and molecular weight distribution of these materials is not dependent on a single molecule, but on a complex mixture of molecules which vary among coals and heavy petroleum samples. Laser Desorption mass spectrometry (LDMS) is emerging as a technique for molecular weight determination having found widespread use in biological polymer research, but is still a relatively new technique in the fossil fuel area. Small angle neutron scattering (SANS) provides information on the size and shape of heavy fossil materials. SANS offers the advantages of high penetration power even in thick cells at high temperatures and high contrast for hydrocarbon systems dispersed in deuterated solvents. LDMS coupled with time of flight has the advantages of high sensitivity and transmission and high mass range. We have used LDMS to examine various heavy fossil-derived materials including: long chain hydrocarbons, asphaltenes from petroleum vacuum resids, and coals. This paper describes the application of laser desorption and small angle neutron scattering techniques to the analysis of components in coals, petroleum resids and unsaturated polymers.

Hunt, J.E.; Winans, R.E.; Thiyagarajan, P.

1997-09-01

348

Kinetic analysis of California oil shale by programmed temperature micropyrolysis. Revision 1  

SciTech Connect

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

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

1991-12-09

349

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

SciTech Connect

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

Thrower, J. D.; Abdulgalil, A. G. M.; Collings, M. P.; McCoustra, M. R. S.; Burke, D. J.; Brown, W. A.; Dawes, A.; Holtom, P. J.; Kendall, P.; Mason, N. J.; Jamme, F.; Fraser, H. J.; Rutten, F. J. M. [School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH 14 4AS (United Kingdom); Department of Chemistry, University College London, 20 Gordon Street, London W1CH 0AJ (United Kingdom); Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); SOLEIL Synchrotron, BP 48, L'Orme des Merisiers, F-91192 Gif surf Yvette Cedex (France); Department of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, John Anderson Building, 107 Rottenrow East, Glasgow G4 0NG (United Kingdom); School of Pharmacy and iEPSAM, Keele University, Keele ST5 5BG (United Kingdom)

2010-07-15

350

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

SciTech Connect

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

S. Semancik; R. E. Cavicchi; D. L. DeVoe; T. J. McAvoy [National Institute of Standards and Technology (US)]|[University of Maryland (US)

2001-12-21

351

Molecular diffusion between walls with adsorption and desorption.  

PubMed

The time dependency of the diffusion coefficient of particles in porous media is an efficient probe of their geometry. The analysis of this quantity, measured, e.g., by nuclear magnetic resonance, can provide rich information pertaining to porosity, pore size distribution, permeability, and surface-to-volume ratio of porous materials. Nevertheless, in numerous if not all practical situations, transport is confined by walls where adsorption and desorption processes may occur. In this article, we derive explicitly the expression of the time-dependent diffusion coefficient between two confining walls in the presence of adsorption and desorption. We show that they strongly modify the time-dependency of the diffusion coefficient, even in this simple geometry. We finally propose several applications, from sorption rates measurements to the use as a reference for numerical implementations for more complex geometries. PMID:23343268

Levesque, Maximilien; Bénichou, Olivier; Rotenberg, Benjamin

2013-01-21

352

Improved Imaging Resolution in Desorption Electrospray Ionization Mass Spectrometry  

SciTech Connect

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

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

2008-01-01

353

Molecular diffusion between walls with adsorption and desorption  

NASA Astrophysics Data System (ADS)

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

Levesque, Maximilien; Bénichou, Olivier; Rotenberg, Benjamin

2013-01-01

354

Laser-induced acoustic desorption (LIAD) mass spectrometry.  

PubMed

Large thermally labile molecules were not amenable to mass spectrometric analysis until the development of atmospheric pressure evaporation/ionization methods, such as electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), since attempts to evaporate these molecules by heating induces degradation of the sample. While ESI and MALDI are relatively soft desorption/ionization techniques, they are both limited to preferential ionization of acidic and basic analytes. This limitation has been the driving force for the development of other soft desorption/ionization techniques. One such method employs laser-induced acoustic desorption (LIAD) to evaporate neutral sample molecules into mass spectrometers. LIAD utilizes acoustic waves generated by a laser pulse in a thin metal foil. The acoustic waves travel through the foil and cause desorption of neutral molecules that have been deposited on the opposite side of the foil. One of the advantages of LIAD is that it desorbs low-energy molecules that can be ionized by a variety of methods, thus allowing the analysis of large molecules that are not amenable to ESI and MALDI. This review covers the generation of acoustic waves in foils via a laser pulse, the parameters affecting the generation of acoustic waves, possible mechanisms for desorption of neutral molecules, as well as the various uses of LIAD by mass spectrometrists. The conditions used to generate acoustic or stress waves in solid materials consist of three regimes: thermal, ablative, and constrained. Each regime is discussed, in addition to the mechanisms that lead to the ablation of the metal from the foil and generation of acoustic waves for two of the regimes. Previously proposed desorption mechanisms for LIAD are presented along with the flaws associated with some of them. Various experimental parameters, such as the exact characteristics of the laser pulse and foil used, are discussed. The internal and kinetic energy of the neutral desorbed molecules are also considered. Our research group has been instrumental in the development and use of LIAD. For example, we have systematically examined the influence of many parameters, such as the type of the foil and its thickness, as well as the analyte layer's thickness, on the efficiency of desorption of neutral molecules. The coupling of LIAD with different instruments and ionization techniques allows for broad use of LIAD in our research laboratories. The most important applications involve analytes that cannot be analyzed by using other mass spectrometric methods, such as large saturated hydrocarbons and heavy hydrocarbon fractions of petroleum. We also use LIAD to characterize lipids, peptides, and oligonucleotides. Fundamental research on the reactions of charged mono-, bi-, and polyradicals with biopolymers, especially oligonucleotides, also requires the use of LIAD, as well as thermochemical measurements for neutral biopolymers. These are but a few of the uses of LIAD in our research group. PMID:22641723

Dow, Alex M; Wittrig, Ashley R; Kenttämaa, Hilkka I

2012-01-01

355

Laser desorption in an ion trap mass spectrometer  

SciTech Connect

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

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

1993-01-01

356

Laser desorption in an ion trap mass spectrometer  

SciTech Connect

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

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

1993-02-01

357

Modeling of a Novel Desorption Cycle by Dielectric Heating  

NASA Astrophysics Data System (ADS)

The paper presents an adsorption cycle for cooling using the dielectric heating method for the regeneration process. Conventional adsorption (AD) chillers employs thermally driven processes for desorption and adsorption where the thermal resistances are high, resulting in a relatively low chiller COP. In this paper, dielectric heating is used to irradiate where the microwave power vibrates the dipole structure of the molecules. Owing to the direct method of energy delivery, the heating process is thus efficient, contributing to an increase in the chiller performance and the COPs. We present the modeling and simulations of the adsorption-desorption cycle in an AD chiller, demonstrating a significant improvement in chiller performance by as much as three folds.

Kumja, M.; Ng, K. C.; Yap, C.; Yanagi, H.; Koyama, S.; Saha, B. B.; Chakraborty, A.

358

Desorption of C60 upon thermal decomposition of cesium C58 fullerides.  

PubMed

A monodispersed fullerene material comprising exclusively C(58) cages was doped with Cs to generate Cs(x)C(58) films of various compositions. The resulting modified properties have been studied using a variety of surface analysis methods with emphasis on thermal desorption and ultraviolet photoelectron spectroscopies. Cs doping raises the thermal stability of C(58) films which are characterized by quasi-covalent cage-cage bonds between annelated pentagon sites. Desorption mass spectra show emission of significant amounts of C(60) at elevated temperatures implying that Cs doping can activate C(58)?C(60) conversion in the condensed phase. In the case of saturated Cs(x)C(58) films, up to 4.5% of the initially deposited C(58) can be desorbed as C(60). From the spectroscopic data, we infer that Cs insertion and transport into the interstitial sites of the C(58) solid is accompanied by spontaneous electron transfer to the electronegative fullerene framework-leading to a weakening of intercage carbon-carbon bonds. At the same time, the overall cohesion of the solid film is enhanced by the formation of multiple ionic Cs(+) (?)C(58) (-) (?) interactions. Near 800 K, Cs(+) activates?catalyzes concerted disproportionation reactions resulting in the transfer of C(2) from C(58) (-) (?) to neighbouring cages to yield C(60) (and C(56)). Heating Cs(x)C(58) films to beyond this temperature range yields a (high temperature) stable reaction product with a significantly modified UP spectrum and a finite density of states at the Fermi level. PMID:22443791

Ulas, Seyithan; Löffler, Daniel; Weis, Patrick; Böttcher, Artur; Kappes, Manfred M

2012-03-21

359

Desorption of C60 upon thermal decomposition of cesium C58 fullerides  

NASA Astrophysics Data System (ADS)

A monodispersed fullerene material comprising exclusively C58 cages was doped with Cs to generate CsxC58 films of various compositions. The resulting modified properties have been studied using a variety of surface analysis methods with emphasis on thermal desorption and ultraviolet photoelectron spectroscopies. Cs doping raises the thermal stability of C58 films which are characterized by quasi-covalent cage-cage bonds between annelated pentagon sites. Desorption mass spectra show emission of significant amounts of C60 at elevated temperatures implying that Cs doping can activate C58-->C60 conversion in the condensed phase. In the case of saturated CsxC58 films, up to 4.5% of the initially deposited C58 can be desorbed as C60. From the spectroscopic data, we infer that Cs insertion and transport into the interstitial sites of the C58 solid is accompanied by spontaneous electron transfer to the electronegative fullerene framework--leading to a weakening of intercage carbon-carbon bonds. At the same time, the overall cohesion of the solid film is enhanced by the formation of multiple ionic Cs+?C58-? interactions. Near 800 K, Cs+ activates/catalyzes concerted disproportionation reactions resulting in the transfer of C2 from C58-? to neighbouring cages to yield C60 (and C56). Heating CsxC58 films to beyond this temperature range yields a (high temperature) stable reaction product with a significantly modified UP spectrum and a finite density of states at the Fermi level.

Ulas, Seyithan; Löffler, Daniel; Weis, Patrick; Böttcher, Artur; Kappes, Manfred M.

2012-03-01

360

Internal energy distributions in desorption electrospray ionization (DESI)  

Microsoft Academic Search

The internal energy distributions of typical ions generated by desorption electrospray ionization (DESI) were measured using\\u000a the “survival yield” method, and compared with corresponding data for electrospray ionization (ESI) and electrosonic spray\\u000a ionization (ESSI). The results show that the three ionization methods produce populations of ions having internal energy distributions\\u000a of similar shapes and mean values (1.7–1.9 eV) suggesting similar

Marcela Nefliu; Jonell N. Smith; Andre Venter; R. Graham Cooks

2008-01-01

361

Kinetics of Mercury(II) Adsorption and Desorption on Soil  

E-print Network

Kinetics of Mercury(II) Adsorption and Desorption on Soil Y U J U N Y I N , H E R B E R T E . A L L of Delaware, Newark, Delaware 19716 D O N A L D L . S P A R K S Department of Plant and Soil Sciences kinetics of Hg(II) on four soils at pH 6 were investigated to discern the mechanisms controlling

Sparks, Donald L.

362

Desorption of Hot Molecules from Photon Irradiated Interstellar Ices  

Microsoft Academic Search

We present experimental measurements of photodesorption from ices of astrophysical relevance. Layers of benzene and water ice were irradiated with a laser tuned to an electronic transition in the benzene molecule. The translational energy of desorbed molecules was measured by time-of-flight (ToF) mass spectrometry. Three distinct photodesorption processes were identified: a direct adsorbate-mediated desorption producing benzene molecules with a translational

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

2008-01-01

363

Helium in silicon: Thermal-desorption investigation of bubble precursors  

Microsoft Academic Search

Thermal desorption measurements are performed on (100)-oriented p-type Si wafers implanted with He ions at 20 keV. The doses have been selected in order to produce crystal damage avoiding the formation of detectable bubbles. The He effusion kinetics, studied both in isothermal and in constant heating rate conditions, exhibit effective activation energy heterogeneity indicating the presence of various kinds of

F. Corni; C. Nobili; G. Ottaviani; R. Tonini; G. Calzolari; G. F. Cerofolini; G. Queirolo

1997-01-01

364

Automatic thermal desorption in GC analysis of dairy product volatiles  

Microsoft Academic Search

Summary  Automatic thermal desorption (ATD) has been evaluated for the analysis of volatile components from dairy products. It has\\u000a resulted in a fast and reproducible method which needs only a low amount of sample. Volatile components from milk are collected\\u000a by off-line purging and trapped on cartridges packed which a suitable adsorbent. Cheese samples are submitted to the same\\u000a process or

E. Valero; E. Miranda; J. Sanz; I. Martínez-Castro

1997-01-01

365

Adsorption, aggregation, and desorption of proteins on smectite particles.  

PubMed

We report on adsorption of lysozyme (LYS), ovalbumin (OVA), or ovotransferrin (OVT) on particles of a synthetic smectite (synthetic layered aluminosilicate). In our approach we used atomic force microscopy (AFM) and quartz crystal microbalance (QCM) to study the protein-smectite systems in water solutions at pH ranging from 4 to 9. The AFM provided insights into the adhesion forces of protein molecules to the smectite particles, while the QCM measurements yielded information about the amounts of the adsorbed proteins, changes in their structure, and conditions of desorption. The binding of the proteins to the smectite surface was driven mainly by electrostatic interactions, and hence properties of the adsorbed layers were controlled by pH. At high pH values a change in orientation of the adsorbed LYS molecules and a collapse or desorption of OVA layer were observed. Lowering pH to the value ?4 caused LYS to desorb and swelling the adsorbed OVA. The stability of OVT-smectite complexes was found the lowest. OVT revealed a tendency to desorb from the smectite surface at all investigated pH. The minimum desorption rate was observed at pH close to the isoelectric point of the protein, which suggests that nonspecific interactions between OVT and smectite particles significantly contribute to the stability of these complexes. PMID:25216210

Kolman, Krzysztof; Makowski, Marcin M; Golriz, Ali A; Kappl, Michael; Pig?owski, Jacek; Butt, Hans-Jürgen; Kiersnowski, Adam

2014-10-01

366

Desorption of cesium from granite under various aqueous conditions.  

PubMed

In this work the desorption of cesium ions from crushed granite in synthetic groundwater (GW) and seawater (SW) was investigated. Results were compared with those obtained in deionized water (DW) and in two kinds of extraction solutions, namely: MgCl(2) and NaOAc (sodium acetate). In general, the desorption rate of Cs from crushed granite increased proportionally with initial Cs loadings. Also, amounts of desorbed Cs ions followed the tendency in the order SW>GW>NaOAc approximately equal MgCl(2)>DW solutions. This indicated that the utilization of extraction reagents for ion exchange will underestimate the Cs desorption behavior. Fitting these experimental data by Langmuir model showed that these extraction reagents have reduced Cs uptake by more than 90%, while only less than 1% of adsorbed Cs ions are still observed in GW and SW solutions in comparison to those in DW. Further SEM/EDS mapping studies clearly demonstrate that these remaining adsorbed Cs ions are at the fracture areas of biotite. PMID:20656497

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

2010-12-01

367

Reaction of NO2 with a pure, thick BaO film: the effect of temperature on the nature of NOx species formed  

SciTech Connect

The adsorption and reaction of NO2 on a thick (>30 ML), pure BaO film deposited onto an Al2O3/NiAl(110) substrate were investigated in the temperature range of 300 – 660 K using temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and x-ray photoelectron spectroscopy (XPS) techniques. The adsorption of NO2 on BaO at room temperature results in the formation of nitrite-nitrate ion pairs. During thermal desorption the nitrite species decompose first, releasing an NO molecule and leaving an O on the surface, while nitrate species decompose in two steps at higher temperatures: at lower temperature as NO2 only, then, at higher temperature, as NO + O2. In cyclic experiments when the BaO film was exposed to NO2 at 300 K, followed by annealing to 575 K, a large amount of NOx was stored as nitrates, and no saturation was achieved even after the 10th adsorption/anneal cycle. This suggests the gradual conversion of the BaO film into barium nitrate clusters at elevated temperatures. The rate of nitrate formation increases as the sample temperature during NO2 exposure increases up to 610 K, while at even higher temperatures the amount of nitrates formed decreases. NO2 adsorption on the thick BaO film at 610 K results in the formation of strongly bound nitrates as the major NOx species.

Yi, Cheol-Woo W.; Szanyi, Janos

2009-02-12

368

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

PubMed

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

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

2014-08-11

369

Surface enrichment of Pt 10Rh 90(111) . II. Exposure to high temperature environments at 760 Torr  

NASA Astrophysics Data System (ADS)

The variation in the surface composition of a model catalyst surface, a Pt 10Rh 90(111) single crystal, has been studied after exposure to oxidizing and reducing gas phase environments at 760 Torr at temperatures typical of automotive catalytic converter operation using ion scattering spectroscopy (ISS) with Ne 20, Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Under reducing conditions, the surface composition is enriched in Pt, consisting of 30% Pt in the surface layer. The Pt enrichment occurs only on the top one-two surface layers. This condition is identical to that obtained after annealing in vacuum at high temperature (1000°C) followed by cooling. Under oxidizing conditions, the surface layer quickly becomes enriched in Rh compared to the bulk, and is accompanied by oxidation of Rh to Rh 2O 3, as indicated by AES and XPS. The Rh enrichment in the oxide form extends several layers below the surface (5-6 nm), but the Rh oxide only accounts for part of the oxygen incorporated in the sample during the high temperature treatment in oxidizing conditions. This suggests a significant portion of the oxygen occupies interstitial sites in the alloy. Temperature programmed desorption in vacuum results in the observance of an intense oxygen desorption peak around 700°C, accounting for both the decomposition of surface Rh 2O 3 and removal of interstitial oxygen. At this point, the surface is still enriched in Rh, but is converted to a Pt-enriched surface by 950°C.

Beck, Donald D.; DiMaggio, Craig L.; Fisher, Galen B.

1993-12-01

370

Analysis of volatile radiolysis products in gamma-irradiated LDPE and polypropylene films by thermal desorption-gas chromatography-mass spectrometry.  

PubMed

Low-molecular-weight ('volatile') radiolysis products of low-density polyethylene (LDPE) and polypropylene (PP) films were investigated by thermal desorption-(TDS)-GC-MS after absorbed doses of up to 25 kGy. The films produce fingerprint chromatograms with highly characteristic patterns of groups of radiation-induced peaks; these are mainly hydrocarbons, aldehydes, ketones, and carboxylic acids with concentrations (after 25 kGy) ca one order of magnitude below that of the residual hydrocarbons (oligomers). PP additionally produces very substantial amounts of three degradation products of phenol-type antioxidants. The low molecular-weight (MW) radiolysis products are retained for considerable times in LDPE films and they are retained in PP films much longer than had been expected. Besides product identification, the following topics are addressed: Effects of the absorbed dose and the desorption temperature; comparison of several commercial (proprietary) films; high-temperature thermal desorption; the question whether TDS analyzes radiation-induced artifacts rather than genuine products; the possible existence of cyclic radiolysis products; the possibility of identifying an LDPE film as irradiated after a dose of only 1 kGy; and atypical trace fragments of antioxidants. Finally, the geometry and efficiency of the thermal desorption system is briefly discussed, and the implications of our findings for irradiation detection and for the safety of irradiated materials are considered. PMID:10697736

Buchalla, R; Boess, C; Bögl, K W

2000-02-01

371

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

PubMed

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

Hu, Jing; Aitken, Michael D

2012-10-01

372

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

PubMed

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

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

2014-01-01

373

Programs  

Cancer.gov

NCI's Office of Cancer Clinical Proteomics Research (OCCPR) works with the Small Business Innovation Research Program to help small business to develop and commercialize novel proteomic technologies and products to prevent, diagnose, and treat cancer.

374

Analytical prediction of moisture absorption/desorption in resin matrix composites exposed to aircraft environments  

NASA Technical Reports Server (NTRS)

The moisture absorption/desorption behavior of resin matrix composites was mathematically modeled by classical diffusion theory using an effective diffusion coefficient. Good agreement was found between calculated moisture content and published data for T300/5208 graphite fiber reinforced epoxy matrix composite. Weather Bureau data for Langley Air Force Base and Norfolk, Va., were used to calculate the amount of moisture a T300/5208 composite panel would contain if exposed outdoors. Results obtained by using average monthly weather data for several high aircraft usage locations around the world suggest that, except for desert areas, geographical locations should have only minimal effect on the moisture absorption level reached in composites. Solar radiation data together with cloud and wind information were included in the analysis to estimate an effective temperature of the composite panel during ground exposure.

Unnam, J.; Tenney, D. R.

1977-01-01

375

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

PubMed Central

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

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

2008-01-01

376

Mechanisms of thermal degradation of a polyester flame-retarded with antimony oxide\\/brominated polycarbonate studied by temperature-programmed analytical pyrolysis  

Microsoft Academic Search

Thermal degradation of a flame-retarded poly(butylene terephthalate) (FR-PBT) consisting of PBT and a synergistic flame-retardant system based on brominated polycarbonate (Br-PC) and Sb2O3 was studied by means of various temperature-programmed analytical pyrolysis techniques such as temperature-programmed pyrolysis-mass spectrometry (TPPy-MS), TPPy-atomic emission detection (TPPy-AED) and TPPy-gas chromatography (TPPy-GC). During the degradation of FR-PBT, brominated phenols were first observed to evolve at

Hiroaki Sato; Kiyotaka Kondo; Shin Tsuge; Hajime Ohtani; Nobuyuki Sato

1998-01-01

377

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

SciTech Connect

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

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

2006-01-01

378

Water sorption and glass transition temperatures in red raspberry ( Rubus idaeus)  

Microsoft Academic Search

Water sorption isotherms and glass transition temperatures of raspberries were determined to understand interactions between water and biopolymers. Water adsorption and desorption isotherms of raspberries were determined with an isopiestic method. Thermal transitions of raspberries equilibrated at selected water concentrations using adsorption and desorption were determined by differential scanning calorimetry (DSC). The sorption isotherm data were modeled by BET and

Roopesh M. Syamaladevi; Shyam S. Sablani; Juming Tang; Joseph Powers; Barry G. Swanson

2010-01-01

379

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

NASA Astrophysics Data System (ADS)

The terrestrial organic carbon (OC) represents one of the largest reservoirs of C on earth and thus plays a crucial role in the global C cycle, participating to the regulation of atmospheric chemistry. While degradation of sedimentary OC (petrogenic C) is a source of CO2 for the atmosphere, burial of biospheric C (e.g. plant debris and soil OC) is a long-term sequestration of atmospheric CO2. Over short timescales, the atmospheric CO2 level is also sensitive to variations of the residence time of carbon in continental reservoirs. Fluvial transport plays a crucial role in the organic carbon cycle, constituting the connection between the different reservoirs and promoting the transfer of C from one reservoir to the other. Moreover, thanks to the integrating effect of erosion, studying river sediments allows the spatial and temporal integration of organic carbon exchanges occurring in a given basin. OC transported by rivers (riverine OC) is known to be extremely heterogeneous in nature and reactivity, however; ranging from extremely refractory petrogenic C (e.g. graphite) to soil complex OC to labile vegetation debris. Here we use a recently developed method, a programmed-temperature pyrolysis-combustion system (PTP-CS) coupled to multiisotopic analysis, to determine the reactivity, age and nature of OC in river sediments. The method takes advantage of the wide range of reactivity and radiocarbon content of different components of riverine OC. We submitted to PTP-CS a set of river sediments from 1) the Ganges-Brahmputra river system and, 2) the lower Mississippi river. Preliminary results highlight the heterogeneous nature of riverine OC. Different components of the riverine OC pool decompose at different temperature and are characterized by extremely variable isotopic compositions. The decomposition of radiocarbon dead petrogenic C at very high temperature allows estimating the respective contribution of biospheric and petrogenic C. Moreover, biospheric OC appears to be itself composed of several components characterized by different reactivity and radiocarbon content. In sediments from the Ganges-Brahmaputra river system we identified at least two main constituents of the biospheric OC pool: 1) a labile component whose radiocarbon content agrees with that of vascular plant biomarkers and, 2) a refractory component, characterized by a very long residence time (ca. 17 Ka). Our first results indicate that PTP-CS has very promising potential to quantify the contribution and residence time of the different components of riverine OC. We expect it will permit significant advance in our understanding of the rate of exchange and flux of terrestrial OC during continental erosion.

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

2010-12-01

380

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

SciTech Connect

The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular precursors, that can be used in low concentrations (temperature-programmed conditions. In this quarter, we have synthesised several bimetallic complexes that contain Mo, Co, and S in a single molecule. Three of them are bimetallic thiocubanes: Mo{sub 2}Co{sub 2}S{sub 4}(S{sub 2} CNEt{sub 2})2(CH{sub 3} CN){sub 2}(CO){sub 2} [designated as MoCo-TCl], Mo{sub 2}Co{sub 2}S{sub 4}Cp{sub 2}(CO){sub 2} [MoCo-TC2], and Mo{sub 2}Co{sub 2}S{sub 4}(Cp`){sub 2}(CO){sub 2} [MoCo-TC3], in which Et, Cp and Cp` represent ethyl, cyclopentadiene, and pentainethylcyclopentadiene, respectively. These thiocubanes were synthesized in our laboratory based on the procedures reported in literature. For comparative examination, the tdanionic bimetallic complex, (PPh{sub 4}){sub 3}Co(MoS{sub 4}){sub 2}, was also synthesized. This bimetallic sulfide complex contains cobalt bis-tetrathiomolybdate trianion, Co(MoS{sub 4}){sub 2}{sup 3{minus}}, and is designated as MoCo-S.

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

1993-07-01

381

Classical studies of shock wave-induced desorption for model adsorbates  

SciTech Connect

The classical trajectory approach has been used to study the shock wave-induced desorption of a model triatomic linear adsorbate from a variety of model surfaces to which it is weakly adsorbed. The branching fraction among intact adsorbate desorption, fragmentation, and desorption with fragmentation has been analyzed as a function of shock wave energy, Debye frequency of the lattice, and the frequency and dissociation energy of the weak terminal interadsorbate bond. In general, fragmentation (with or without desorption) was observed to dominate over intact desorption. The results are explained partially in terms of resonances between low frequency adsorbate modes and the Debye frequency of the lattice. In addition, no evidence was found for a bottleneck in intact desorption which would allow the desorbing molecule to remain internally cold. {copyright} {ital 1996 American Institute of Physics.}

Dzegilenko, F.N. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)] [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States); Uzer, T. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)] [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Herbst, E. [Departments of Physics and Astronomy, The Ohio State University, Columbus, Ohio 43210 (United States)] [Departments of Physics and Astronomy, The Ohio State University, Columbus, Ohio 43210 (United States)

1996-12-01

382

Program  

Cancer.gov

Through the DCIDE program, the developer of a promising diagnostic agent or probe will be given access to the pre-clinical development resources of the National Cancer Institute in a manner that is intended to remove the most common barriers between laboratory discoveries and IND status.

383

Ambient desorption ionization mass spectrometry (DART, DESI) and its bioanalytical applications  

Microsoft Academic Search

In recent years, ambient desorption ionization techniques for mass spectrometry were introduced. Among them, the most established\\u000a techniques are Direct Analysis in Real Time (DART) and Desorption Electrospray Ionization (DESI). Therefore, the current review\\u000a focuses on the bioanalytical applications of ambient desorption ionization techniques by the example of DART and DESI mass\\u000a spectrometry. The potential and also limitations of both

Elena S. Chernetsova; Gertrud E. Morlock

2011-01-01

384

Combined temperature-programmed reaction and in situ x-ray scattering studies of size-selected silver clusters under realistic reaction conditions in the epoxidation of propene  

NASA Astrophysics Data System (ADS)

The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions for the first time. The approach is illustrated in a chemical industry highly relevant selective partial oxidation of propene on a monodisperse silver nanocatalyst. The shape of the catalyst undergoes rapid change already at room temperature upon the exposure to the reactants, followed by a complex evolution of shape with increasing temperature. Acrolein formation is observed around 50 °C while the formation of the propylene oxide exhibits a sharp onset at 80 °C and is leveling off at 150 °C. At lower temperatures acrolein is produced preferentially to propylene oxide; at temperatures above 100 °C propylene oxide is favored.

Vajda, Stefan; Lee, Sungsik; Sell, Kristian; Barke, Ingo; Kleibert, Armin; von Oeynhausen, Viola; Meiwes-Broer, Karl-Heinz; Rodríguez, Arantxa Fraile; Elam, Jeffrey W.; Pellin, Michael M.; Lee, Byeongdu; Seifert, Sönke; Winans, Randall E.

2009-09-01

385

Evaluation of Water Repellency in Petroleum Drilling Cuttings Treated by Thermal Desorption: Implications for Use in Construction and Agriculture  

NASA Astrophysics Data System (ADS)

Thermal desorption is one of many methods used for the remediation of hydrocarbon contaminated soils and similar materials. It has several advantages over competing technologies, especially with respect to treatment times. While the biological treatment of contaminated soils may take several months depending principally on the type of hydrocarbons and starting concentration, thermal desorption typically takes less than one month, depending on the treatment capacities of the equipment involved, and the volume of material requiring treatment. In the petroleum producing region of southeastern Mexico, this has been one of the principal methods used for the treatment of drilling cuttings, due mostly to the short time required. As with most remediation projects, as well as in the treatment of exploration and production (E&P) wastes, the criteria used to consider the remediation finalized is the concentration of hydrocarbons in the treated material. This is based on the supposition that at some (relatively low) hydrocarbon concentration, the toxicological affects are reduced to acceptable levels. However, little attention has been paid to the physical-chemical properties of supposedly treated material, which may suffer from water repellency, especially in thermal treatment methods. This could greatly reduce the options for final use of treated materials, especially to support plant growth. Conversely, there may be some construction uses of treated material in which some water repellence could be beneficial (caps for land fills, for example). Considering the relevance of the physical-chemical impacts of petroleum on soil and similar materials, we felt it was important to evaluate the efficiency of the principal method used to treat E&P wastes in Mexico (thermal desporption) based on these factors. In this study different operating conditions (temperature and residence time) of a sub-pilot scale thermal desorption unit were evaluated with respect not only to reduction in hydrocarbon concentration, but also based on water repellency. To our knowledge this is the first study of this type. Water repellency severity was measured in petroleum drilling cuttings which had been treated by thermal desorption to reduce the concentration of total petroleum hydrocarbons (TPHs). The initial TPH concentration in the untreated material was 16850mg/Kg (dry). The prototype batch rotary oven used in this study was operated at 25 rpm, at three temperatures and three treatment times: at 150, 200, and 300°C, for 10, 15, and 20 minutes. Four of the nine treatments complied with the Mexican environmental norm (TPH less than 3000 mg/Kg), these being: at 200°C for 20 minutes and at 300°C for 10, 15 and 20 minutes. The treatments at 150°C resulted in a TPH reduction insufficient to comply with Mexican norm, and also resulted in high MED values (3,46 - 3,67). At 200°C, the decrease in repellency was directly proportional to the treatment time (r=-0,950), with a final value of MED=2,61 after 20 minutes. At 300°C, an increase in water repellency was observed to be directly proportional to the treatment time (r=0,9997), with a final value of MED=3,73 (severe repellence) after 20 minutes. This may be due to the partial combustion (rather than only desorption) of hydrocarbons at this temperature, and their deposition on soil surfaces. Based on these observations, operating conditions of 200°C for 20 minutes are recommended to achieve effective thermal desorption while reducing water repellency in the treated material. If a final material with more severe water repellency is desired for use in construction, a higher operation temperature is required (300°C) for at least 15-20 minutes.

Domínguez-Rodríguez, Verónica I.; Guzmán-Osorio, Francisco J.; Adams Schroeder, Randy H.; Bautista-Margulis, Raúl G.

2010-05-01

386

Growth of M-plane GaN on ?- LiAlO2(1 0 0) : the role of Ga adsorption/desorption  

NASA Astrophysics Data System (ADS)

We study the adsorption and desorption kinetics of Ga on GaN(1 1¯ 0 0) using in situ reflection high-energy electron diffraction. Two stable surface phases are identified, which manifest themselves at low temperature by a (1×2) reconstruction at bilayer coverage and a (4×4) reconstruction at trilayer coverage. At growth temperature, Ga adsorbs layer-by-layer up to bilayer coverage after which Ga cluster and eventually droplet formation occurs. The bilayer desorption is delayed by “feeding” from this excess Ga. The optimum growth conditions with regard to surface morphology are those giving rise to trilayer coverage. This finding is in contrast to the case of GaN(0 0 0 1) where the optimum growth conditions are related to the formation of a Ga bilayer at the growth front.

Brandt, Oliver; Jun Sun, Yue; Däweritz, Lutz; H. Ploog, Klaus

2004-07-01

387

Laser Stimulated Desorption from Compound Semiconductors, Dimerization Enhanced Phase Transition  

NASA Astrophysics Data System (ADS)

Laser stimulated desorption (LSD) of neutral particles has been investigated in compound semiconductors MX of GaN, GaP, GaAs and CdS. No effects of crystallographic orientations on the characteristics of LSD, desorption yields, mean kinetic energies, and speed ratios have been recognized among (111) and (100) orientations in GaP and GaAs. This fact suggests that LSD does not follow the unimolecular dissociation of locally excited surface bonds, but occurs via a bulky event involving a phase transtion. The threshold laser powers for LSD were correlated to the crystal bond ionicities fi, which are good measures for the structural stability of tetrahedral covalent solids. It was found that with increasing fi of the solids, threshold laser powers tend to decrease. The dominant species ejected from MX were found to be in the forms of monomer M and X as well as dimer X2. The ratio of the yields of X2 to those of X increases as the single-bond energy of X2 increases. Considering these experimental results, we propose a model of a non-local electronic excitation mechanism for LSD; namely, LSD occurs via the dimerization enhanced phase transition in a high-density electron-hole plasma.

Namiki, Akira; Cho, Seiji; Ichige, Kenji

1987-01-01

388

Laser Desorption VUV Postionization MS Imaging of a Cocultured Biofilm  

PubMed Central

Laser desorption postionization mass spectrometry (LDPI-MS) imaging is demonstrated with a 10.5 eV photon energy source for analysis and imaging of small endogenous molecules within intact biofilms. Biofilm consortia comprised of a synthetic Escherichia coli K12 coculture engineered for syntrophic metabolite exchange are grown on membranes, then used to test LDPI-MS analysis and imaging. Both E. coli strains displayed many similar peaks in LDPI-MS up to m/z 650, although some observed differences in peak intensities were consistent with the appearance of byproducts preferentially expressed by one strain. The relatively low mass resolution and accuracy of this specific LDPI-MS instrument prevented definitive assignment of species to peaks, but strategies are discussed to overcome this shortcoming. The results are also discussed in terms of desorption and ionization issues related to the use of 10.5 eV single photon ionization, with control experiments providing additional mechanistic information. Finally, 10.5 eV LDPI-MS was able to collect ion images from intact, electrically insulating biofilms at ~100 ?m spatial resolution. Spatial resolution of ~20 ?m was possible, although a relatively long acquisition time resulted from the 10 Hz repetition rate of the single photon ionization source. PMID:23052888

Bhardwaj, Chhavi; Moore, Jerry F.; Cui, Yang; Gasper, Gerald L.; Bernstein, Hans C.; Carlson, Ross P.; Hanley, Luke

2012-01-01

389

Characterization of polymer decomposition products by laser desorption mass spectrometry  

NASA Technical Reports Server (NTRS)

Laser desorption mass spectrometry has been used to characterize the ash-like substances formed on the surfaces of polymer matrix composites (PMC's) during exposure on LDEF. In an effort to minimize fragmentation, material was removed from the sample surfaces by laser desorption and desorbed neutrals were ionized by electron impact. Ions were detected in a time-of-flight mass analyzer which allows the entire mass spectrum to be collected for each laser shot. The method is ideal for these studies because only a small amount of ash is available for analysis. Three sets of samples were studied including C/polysulfone, C/polyimide and C/phenolic. Each set contains leading and trailing edge LDEF samples and their respective controls. In each case, the mass spectrum of the ash shows a number of high mass peaks which can be assigned to fragments of the associated polymer. These high mass peaks are not observed in the spectra of the control samples. In general, the results indicate that the ash is formed from decomposition of the polymer matrix.

Pallix, Joan B.; Lincoln, Kenneth A.; Miglionico, Charles J.; Roybal, Robert E.; Stein, Charles; Shively, Jon H.

1993-01-01

390

Accounting for adsorption and desorption in lattice Boltzmann simulations.  

PubMed

We report a Lattice-Boltzmann scheme that accounts for adsorption and desorption in the calculation of mesoscale dynamical properties of tracers in media of arbitrary complexity. Lattice Boltzmann simulations made it possible to solve numerically the coupled Navier-Stokes equations of fluid dynamics and Nernst-Planck equations of electrokinetics in complex, heterogeneous media. With the moment propagation scheme, it became possible to extract the effective diffusion and dispersion coefficients of tracers, or solutes, of any charge, e.g., in porous media. Nevertheless, the dynamical properties of tracers depend on the tracer-surface affinity, which is not purely electrostatic and also includes a species-specific contribution. In order to capture this important feature, we introduce specific adsorption and desorption processes in a lattice Boltzmann scheme through a modified moment propagation algorithm, in which tracers may adsorb and desorb from surfaces through kinetic reaction rates. The method is validated on exact results for pure diffusion and diffusion-advection in Poiseuille flows in a simple geometry. We finally illustrate the importance of taking such processes into account in the time-dependent diffusion coefficient in a more complex porous medium. PMID:23944584

Levesque, Maximilien; Duvail, Magali; Pagonabarraga, Ignacio; Frenkel, Daan; Rotenberg, Benjamin

2013-07-01

391

Accounting for adsorption and desorption in lattice Boltzmann simulations  

NASA Astrophysics Data System (ADS)

We report a Lattice-Boltzmann scheme that accounts for adsorption and desorption in the calculation of mesoscale dynamical properties of tracers in media of arbitrary complexity. Lattice Boltzmann simulations made it possible to solve numerically the coupled Navier-Stokes equations of fluid dynamics and Nernst-Planck equations of electrokinetics in complex, heterogeneous media. With the moment propagation scheme, it became possible to extract the effective diffusion and dispersion coefficients of tracers, or solutes, of any charge, e.g., in porous media. Nevertheless, the dynamical properties of tracers depend on the tracer-surface affinity, which is not purely electrostatic and also includes a species-specific contribution. In order to capture this important feature, we introduce specific adsorption and desorption processes in a lattice Boltzmann scheme through a modified moment propagation algorithm, in which tracers may adsorb and desorb from surfaces through kinetic reaction rates. The method is validated on exact results for pure diffusion and diffusion-advection in Poiseuille flows in a simple geometry. We finally illustrate the importance of taking such processes into account in the time-dependent diffusion coefficient in a more complex porous medium.

Levesque, Maximilien; Duvail, Magali; Pagonabarraga, Ignacio; Frenkel, Daan; Rotenberg, Benjamin

2013-07-01

392

Desorption of biocides from renders modified with acrylate and silicone.  

PubMed

Biocides are used in the building industry to prevent algal, bacterial and fungal growth on polymericrenders and thus to protect buildings. However, these biocides are leached into the environment. To better understand this leaching, the sorption/desorption of biocides in polymeric renders was assessed. In this study the desorption constants of cybutryn, carbendazim, iodocarb, isoproturon, diuron, dichloro-N-octylisothiazolinone and tebuconazole towards acrylate and silicone based renders were assessed at different pH values. At pH 9.5 (porewater) the constants for an acrylate based render varied between 8 (isoproturon) and 9634 (iodocarb) and 3750 (dichloro-N-octylisothiazolinone), respectively. The values changed drastically with pH value. The results for the silicone based renders were in a similar range and usually the compounds with high sorption constants for one polymer also had high values for the other polymer. Comparison of the octanol water partitioning constants (Kow) with the render/water partitioning constants (Kd) revealed similarities, but no strong correlation. Adding higher amounts of polymer to the render material changed the equilibria for dichloro-N-octylisothiazolinone, tebuconazole, cybutryn, carbendazim but not for isoproturon and diuron. PMID:24059976

Styszko, Katarzyna; Bollmann, Ulla E; Wangler, Timothy P; Bester, Kai

2014-01-01

393

Experimental and modeling study of adsorption–desorption processes with application to a deep-well injection radioactive waste disposal site  

Microsoft Academic Search

Radionuclide (Sr-90 and Cs-137) behavior in the subsurface environment was evaluated with respect to natural attenuation, sorption and desorption kinetics, and equilibrium. Batch experiments were conducted with synthesized groundwater or acid (NaNO3; pH ?3) solutions under different temperature (T=20 and 70 °C) and pressure (P=Patm and P=3 MPa) conditions. Samples of sedimentary rock were selected as the solid phase from

V. G. Rumynin; P. K. Konosavsky; E. Hoehn

2005-01-01

394

Auger decay mechanism in photon-stimulated desorption of ions from surfaces  

SciTech Connect

Photon-stimulated desorption (PSD) of positive ions was studied with synchrotron radiation using an angle-integrating time-of-flight mass spectrometer. Ion yields as functions of photon energy near core levels were measured from condensed gases, alkali fluorides, and other alkali and alkaline earth halides. These results are compared to bulk photoabsorption measurements with emphasis on understanding fundamental desorption mechanisms. The applicability of the Auger decay mechanism, in which ion desorption is strictly proportional to surface absorption, is discussed in detail. The Auger decay model is developed in detail to describe Na/sup +/ and F/sup +/ desorption from NaF following Na(1s) excitation. The major decay pathways of the Na(1s) hole leading to desorption are described and equations for the energetics of ion desorption are developed. Ion desorption spectra of H/sup +/, Li/sup +/, and F/sup +/ are compared to bulk photoabsorption near the F(2s) and Li(1s) edges of LiF. A strong photon beam exposure dependence of ion yields from alkali fluorides is revealed, which may indicate the predominance of metal ion desorption from defect sites. The large role of indirect mechanisms in ion desorption condensed N/sub 2/-O/sub 2/ multilayers is demonstrated and discussed. Ion desorption spectra from several alkali halides and alkaline earth halides are compared to bulk photoabsorption spectra. Relative ion yields from BaF/sub 2/ and a series of alkali halides are discussed in terms of desorption mechanisms.

Parks, C.C.

1983-11-01

395

Interaction of Cl 2 with the Au(111) surface in the temperature range of 120 to 1000 K  

NASA Astrophysics Data System (ADS)

The interaction of gaseous chlorine (Cl 2) with a Au(111) single-crystal surface over the temperature range of 120-1000 K has been examined by using Auger electron spectroscopy (AES), X-ray and UV photoelectron spectroscopy (XPS and UPS), low-energy electron diffraction (LEED), temperature-programmed desorption (TPD), and work-function change (??) measurements. Chlorine dissociatively adsorbs at all temperatures above 120 K. The Cl 2 dissociative sticking coefficient decreases as the exposure temperature increases above 120 K, yielding an apparent activation energy of -0.2 kcal/mol for this process. No stable molecularly adsorbed Cl 2 state was found at 120 K, which is just above the temperature required to desorb condensed Cl 2 films. The work function increases with Cl 2 exposure and reaches a maximum value of ?? = 1.2 eV at 120 K and ?? = 0.9 eV for the 500 K dose, indicating occupation of adatom sites on the Au(111) surface. An upper limit for the saturation coverage of Cl atoms, ? satCl, produced by Cl 2 exposure under ultra-high vacuum conditions was estimated from AES calibration as ? satCl ? 2.9. A (?3 × ?3)R30° LEED pattern was observed for the first time at temperatures below 230 K. A structural model is proposed for the LEED pattern in which there are four Cl atoms per unit cell with atomic radii of 1.24 Å, giving ?Cl = 1.33. Loss of Cl from the surface starts to occur upon heating the Au substrate to 600 K, due primarily to desorption of Cl-containing species rather than diffusion into the bulk. Two desorption states, at 790 and 640 K, were observed in TPD which differ in their Cl +/Cl +2 ratio as detected by the mass spectrometer. We assign these peaks as due to desorption of Cl (g) and Cl 2(g), respectively, with desorption activation energies estimated to be 48 and 39 kcal/mol, respectively. No desorption of AuCl x species was observed. The Cl(2p) core-level peak at 197.3 eV binding energy (BE) in XPS did not shift with Cl 2 exposure or temperature. UPS identified chlorine-derived peaks at 1.9, 4.4, 5.5 and 6.9 eV BE, but no peaks were assigned to gold chlorides. Since only small changes in the chemical nature of Au surface atoms were observed in XPS and UPS, the interaction between Cl 2 and Au(111) forms chemisorbed chlorine adatoms, Cl (a), and not a surface chloride compound under our conditions. However, the work function and AES uptake curves exhibited local minima before the onset of the desorption, which might be interpreted as some incorporation of chlorine into the surface layer at large ? Cl. We have summarized the thermochemistry of chlorine adsorption on Au(111) and estimate that the dissociation energy of the Cl-Au bond, D(Au-Cl) is about 54 kcal/mol. This is at least 20 kcal/mol smaller than on Ag.

Kastanas, George N.; Koel, Bruce E.

1993-03-01

396

A Combined Desorption Ionization by Charge Exchange (DICE) and Desorption Electrospray Ionization (DESI) Source for Mass Spectrometry  

NASA Astrophysics Data System (ADS)

A source that couples the desorption ionization by charge exchange (DICE) and desorption electrospray ionization (DESI) techniques together was demonstrated to broaden the range of compounds that can be analyzed in a single mass spectrometric experiment under ambient conditions. A tee union was used to mix the spray reagents into a partially immiscible blend before this mixture was passed through a conventional electrospray (ES) probe capillary. Using this technique, compounds that are ionized more efficiently by the DICE method and those that are ionized better with the DESI procedure could be analyzed simultaneously. For example, hydroquinone, which is not detected when subjected to DESI-MS in the positive-ion generation mode, or the sodium adduct of guaifenesin, which is not detected when examined by DICE-MS, could both be detected in one experiment when the two techniques were combined. The combined technique was able to generate the molecular ion, proton and metal adduct from the same compound. When coupled to a tandem mass spectrometer, the combined source enabled the generation of product ion spectra from the molecular ion and the [M + H]+ or [M + metal]+ ions of the same compound without the need to physically change the source from DICE to DESI. The ability to record CID spectra of both the molecular ion and adduct ions in a single mass spectrometric experiment adds a new dimension to the array of mass spectrometric methods available for structural studies.

Chan, Chang-Ching; Bolgar, Mark S.; Miller, Scott A.; Attygalle, Athula B.

2011-01-01

397

Soil Aggregate Size Affects Phosphorus Desorption from Highly Weathered Soils and Plant Growth  

E-print Network

Soil Aggregate Size Affects Phosphorus Desorption from Highly Weathered Soils and Plant Growth X of P around soil aggregates (Gunary et al., 1964; Linquist etfrom soil, understanding P desorption from soils may improve the precision of P diagnosis and fertilization recommendations. Many al., 1997

van Kessel, Chris

398

Cell Adsorption and Selective Desorption for Separation of Microbial Cells by Using Chitosan-Immobilized Silica  

Microsoft Academic Search

Cell adsorption and selective desorption for separation of microbial cells were conducted by using chitosan- immobilized silica (CIS). When chitosan was immobilized onto silica surfaces with glutaraldehyde, bacterial cells adsorbed well and retained viability. Testing of the adsorption and desorption ability of CIS using various microbes such as Escherichia coli, Aeromonas hydrophila, Pseudomonas aeruginosa, Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus,

Munehiro Kubota; Masayoshi Matsui; Hiroyuki Chiku; Nobuyuki Kasashima; Manabu Shimojoh; Kengo Sakaguchi

2005-01-01

399

Kinetics and Mechanisms of Pb(II) Sorption and Desorption at the  

E-print Network

Kinetics and Mechanisms of Pb(II) Sorption and Desorption at the Aluminum Oxide-Water Interface D sorption at the mineral-water interface is often initially fast followed by a decrease in the sorption rate in the environment is highly dependent on sorption and desorption reactions on solid surfaces. In this study Pb

Sparks, Donald L.

400

Laser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon microcolumn arrays  

E-print Network

Laser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon for soft laser desorption/ionization (SLDI) mass spectrometry. Thin films of gold nanoparticles (with 12 to analyze a series of directly deposited polypeptide samples. In this new SLDI method, the required laser

Vertes, Akos

401

Adsorption, desorption and isotopic exchange of cadmium on illite: evidence for complete reversibility  

Microsoft Academic Search

Adsorption, desorption and isotopic exchange of Cd on illite clay have been studied at low Cd concentrations and low ionic strength. The results indicate that under the conditions of the experiments Cd sorption on illite is completely reversible. Long equilibration times (7–8 weeks) were shown to be essential because of slow desorption kinetics.

R. N. J. Comans

1987-01-01

402

Effect of desorption kinetics on colloid-facilitated transport of contaminants: Cesium, strontium, and illite colloids  

Microsoft Academic Search

To examine the importance of desorption kinetics to colloid-facilitated transport, we conducted column experiments comparing the transport of cesium and strontium through a saturated quartz sand porous medium in the absence and presence of illite colloids at two ionic strengths. Because cesium desorption from illite was anticipated to be slower than that of strontium, we expected to see a contrast

Ned B. Turner; Joseph N. Ryan; James E. Saiers

2006-01-01

403

A General Model for Kinetics of Heavy Metal Adsorption and Desorption on Soils  

E-print Network

chemistry (e.g., pH, cation competition, metal concentrations, etc.) and soil composition (e.g., soil chemistry and soil composition on metal adsorption/desorption kinetics in soils. Based an early versionA General Model for Kinetics of Heavy Metal Adsorption and Desorption on Soils Zhenqing Shi

Sparks, Donald L.

404

Kinetics of manganese adsorption, desorption, and oxidation in coastal marine sediments  

E-print Network

Kinetics of manganese adsorption, desorption, and oxidation in coastal marine sediments Dominique´bec a` Rimouski, Que´bec, Canada Abstract Ejection of excavated manganese (Mn)-laden particles from disturbances triggers desorption and oxidation of reduced manganese species. These competing reactions

Beaudoin, Georges

405

Characterization of sulfided Mo/Al[sub 2]O[sub 3] catalysts by temperature-programmed reduction and low-temperature fourier transform infrared spectroscopy of adsorbed carbon monoxide  

SciTech Connect

Sulfided Mo/Al[sub 2]O[sub 3] catalysts were studied by temperature-programmed reduction (TPRS) and transmission infrared spectroscopy of adsorbed CO at low temperatures. Reductive elimination of nonstoichiometric and stoichiometric sulfur from edge and corner sites creates coordinatively unsaturated Mo[sup 2+] sites. C-O stretching bands at 2100 cm[sup [minus]1] and at ca. 2060-2070 cm[sup [minus]1] were attributed to CO adsorption complexes on edge and corner sites, respectively. Evidence of morphological changes of MoS[sub 2] slabs during H[sub 2] treatment at 770 K is provided. IR spectroscopy of adsorbed CO at low temperature provides unique possibilities for the characterization of sulfided catalysts. 39 refs., 8 figs., 1 tab.

Mueller, B.; Knoezinger, H. (Universitaet Muenchen (Germany)); Langeveld, A.D. van; Moulijn, J.A. (Delft Univ. of Technology (Netherlands))

1993-09-02

406

Samarium Ion Exchanged Montmorillonite for High Temperature Cumene Cracking Reaction  

NASA Astrophysics Data System (ADS)

Montmorillonite clay is cation exchanged with samarium and its catalytic influence in cumene cracking reaction is investigated. Effect of exchange with sodium ions on further exchange with samarium ions is also noted. Acidity measurements are done using Temperature Programmed Desorption (TPD) of ammonia. The retention of basic structure is proved from FTIR spectra and XRD patterns. Elemental analysis result shows that samarium exchange has occurred, which is responsible for the higher catalytic activity. Surface area and pore volume remains more or less unaffected upon exchange. Thermogravimetric analysis indicates the enhanced thermal stability on exchanging. Cumene cracking reaction is carried out at atmospheric pressure in a fixed bed glass reactor at 673 K. The predominance of Brønsted acidity is confirmed from high selectivity to benzene.

Binitha, N. N.; Silija, P. P.; Suraj, V.; Yaakob, Z.; Sugunan, S.

2011-02-01

407

Energy Audit of Three Energy-Conserving Devices in a Steel Industry Demonstration Program. Task III. GTE High Temperature Recuperation.  

National Technical Information Service (NTIS)

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-temp...

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

1983-01-01

408

Helium in silicon: Thermal-desorption investigation of bubble precursors  

NASA Astrophysics Data System (ADS)

Thermal desorption measurements are performed on (100)-oriented p-type Si wafers implanted with He ions at 20 keV. The doses have been selected in order to produce crystal damage avoiding the formation of detectable bubbles. The He effusion kinetics, studied both in isothermal and in constant heating rate conditions, exhibit effective activation energy heterogeneity indicating the presence of various kinds of traps, precursor of the bubbles. The energy distribution results peaked at about 1.1 eV with an exponential decay towards higher energies and a width of about 0.2 eV. A semiquantitative model, based on the present knowledge about the Si:He system, is proposed, that accounts for He filled nanoblisters formation through interstitial He clustering and precipitation. The observed energy heterogeneity is ascribed to variations of the He solution energy from these cavities due to He-He and He-wall interactions.

Corni, F.; Nobili, C.; Ottaviani, G.; Tonini, R.; Calzolari, G.; Cerofolini, G. F.; Queirolo, G.

1997-09-01

409

FTMS method for high resolution matrix-assisted laser desorption  

NASA Astrophysics Data System (ADS)

A Fourier transform mass spectrometer with an external ion source has been modified for use with matrix-assisted laser desorption. High trapping potentials on the FTMS analyzer cell decelerate and trap the laser-produced ions, and a pulsed argon buffer gas coosl them prior to detection. For gramicidin S, only one laser pulse is needed to produce ass spectra with a high signal-to-noise ratio and a mass resolution of 1 100 000 (FWHM). Several other oligopeptides and small proteins have been analyzed, including bovine insulin that was detected at a mass resolution of 90 000. These results represent the highest mass resolution ever demonstrated for ions made by MALDI.

McIver, Robert T., Jr.; Li, Yunzhi; Hunter, Richard L.

1994-04-01

410

The desorption purge time and thermal stability of 1,3-butadiene in a charcoal sampling tube  

E-print Network

Thermal desorption is a technique used in the recovery of sampled airborne organic compounds from solid adsorbent trapping media. There are several advantages of this technique over solvent desorption: 1) absence of the toxic solvent; 2) greater...

Xie, Jianghua

2012-06-07

411

CRC (Coordinating Research Council) hot-start and driveaway driveability program at high and intermediate temperatures using gasoline-alcohol blends  

SciTech Connect

A cooperative CRC test program was conducted at Failure Analysis Associates Test Track in Phoenix, Arizona, from September 4 through October 4, 1985. The program investigated the hot-start driveability of thirteen 1985 model vehicles with eight hydrocarbon-alcohol blends and two hydrocarbon-only gasolines at nominal ambient temperatures of 90 and 70 F. The driveability procedure was modified to emphasize conditions that may cause fuel foaming. Carburetted, throttle-body-injected (TBI), port-fuel-injected (PFI), and port-fuel-injected turbocharged fuel systems were represented in the vehicle fleet. Ambient temperature effects were highly significant for carburetted and throttle-body-injected vehicle fuel-metering systems and for the total fleet. Carburetted vehicles were more sensitive to fuel properties and ambient conditions than fuel-injected vehicles.

Not Available

1988-08-01

412

Bench- and pilot-scale thermal desorption treatability studies on pesticide-contaminated soils from Rocky Mountain Arsenal  

SciTech Connect

Thermal desorption is being considered as a potential remediation technology for pesticide-contaminated soils at the Rocky Mountain Arsenal (RMA) in Denver, Colorado. From 1988 through 1992, numerous laboratory- and bench-scale indirect-heated thermal desorption (IHTD) treatability studies have been performed on various soil medium groups from the arsenal. RMA has contracted Argonne National Laboratory to conduct a pilot-scale direct-fired thermal desorption (DFTD) treatability study on pesticide-contaminated RMA soil. The purpose of this treatability study is to evaluate the overall effectiveness of the DFTD technology on contaminated RMA soils and to provide data upon which future conceptual design assumptions and cost estimates for a full-scale system can be made. The equipment used in the DFTD treatability study is of large enough scale to provide good full-scale design parameters and operating conditions. The study will also provide valuable-emissions and materials-handling data. Specifically this program will determine if DFTD can achieve reductions in soil contamination below the RMA preliminary remediation goals (PRGs), define system operating conditions for achieving the PRGs, and determine the fate of arsenic and other hazardous metals at these operating conditions. This paper intends to compare existing data from a bench-scale IHTD treatability study using equipment operated in the batch mode to new data from a pilot-scale DFTD operated in a parallel-flow continuous mode. Delays due to materials-handling problems and permit issues have delayed the start of the pilot-scale DFTD testing. The first pilot-scale test is scheduled for the flat week in January 1995. The available data will be presented March 9, 1995, at the Seventh Annual Gulf Coast Environmental Conference in Houston, Texas.

Swanstrom, C.P. [Argonne National Lab., IL (United States); Besmer, M. [Rocky Mountain Arsenal, Denver, CO (United States)

1995-03-09

413

Incubation time effects on imazaquin desorption as determined by nonequilibrium thin-soil disc flow.  

PubMed

Because organic sorption in soil may never reach equilibrium, a thin-disc flow nonequilibrium method may be helpful in understanding herbicide-soil interactions. This research was conducted to (i) determine the influence of incubation time on imazaquin [2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-3-quinolinecarboxylic acid] desorption from soil, (ii) examine the influence of solution flow velocities on desorption, and (iii) elucidate the most appropriate kinetic model to describe imazaquin leaching. Soil at 7.5% moisture w/w was treated with imazaquin and incubated for 24, 72, and 168 h. Treated soil was sealed in an in-line filter apparatus and rinsed with 5.0 mM CaCl2 at 0.33, 0.67, or 1.0 mL min(-1). Effluent was collected as 1.0-mL fractions for a total of 50 mL. Flow was stopped for 24 h. When flow resumed, fractions were collected for an additional 15 mL. After the initial desorption, 79% of the imazaquin incubated for 24 h was leached. Increasing incubation time beyond 24 h reduced imazaquin leaching. After both desorption events, 13% of the initially applied imazaquin remained in the soil incubated for 168 h, compared with 7% with soil incubated for 24 h. Elovich and Freundlich kinetics accounted for 98% of the variance observed in the imazaquin desorption curves. First-order and diffusion kinetics accounted for 91% of the variance. Incubating soil for 72 h before desorption reduced the rate of imazaquin desorption by approximately 12%, compared with the 24-h incubation treatment. Imazaquin desorption was not affected by wash solution flow rate. These data suggest that the kinetics of desorption in prolonged desorption events are limited by transport phenomena (i.e., particle and film diffusion). PMID:15074810

Smith, M Cade; Shaw, David R; Massey, Joseph H; Boyette, Michele; Kingery, William

2004-01-01

414

Desorption mechanisms in PMMA irradiated by high order harmonics  

NASA Astrophysics Data System (ADS)

The recent development of intense sources in the XUV range (10-100 nm), such as X-ray laser, Free Electron Laser and High order Harmonics (HoH), allows the study of high flux processes and ultra-fast dynamics in various domains. At the SLIC facility of CEA-Saclay, we have built a gas-harmonic beamline to investigate the interaction of intense XUV pulse with solids. High Harmonics of an IR laser (Ti:Sa at 800 nm, 35 fs, 13 mJ/pulse, 1 kHz) are generated in a rare gas cell (Xe). The useful XUV range (40-60 nm) is selected with metallic filters. The harmonic beam is focused with a parabolic mirror to a 10 ?m focal spot on sample, leading to a fluence per shot of up to 1 mJ/cm2 (within a typical 10 fs pulse duration). Studies aimed at understanding the damaging mechanisms caused by XUV irradiation on surface of various samples by systematically varying of fluence and exposure time. For PMMA irradiated in the desorption regime (fluence/shot <= 0.2 mJ/cm2), the surface presents craters whose profile depends on the dose (Grey [Gy] = 1 J/kg). The crater evolution proceeds from the competition between two main degradation processes, that is chain scission and cross linking. Namely, at low dose (<= 1 GGy) polymer chain scission is followed by the blow up of the volatile, molecular fragments, forming the crater. At high dose (> 10 GGy) the broken chain-ends, in the near-surface layer of the remaining material, recombine by cross-linking, opposing desorption by surface hardening. In a recent experiment at LCLS FEL facility, PMMA was irradiated at high fluence; the cross-linking signature was identified from Raman spectroscopy. A kinetic model could be adapted for interpreting these original and very promising results.

De Grazia, M.; Merdji, H.; Auguste, T.; Carré, B.; Gaudin, J.; Geoffroy, G.; Guizard, S.; Krejci, F.; Kuba, J.; Chalupsky, J.; Cihelka, J.; Hajkova, V.; Ledinský, M.; Juha, L.

2011-06-01

415

Heavy metal interactions with phosphatic clay: sorption and desorption behavior.  

PubMed

Heavy metals produced and released during agricultural and industrial activities may pose a serious threat to the environment. This study investigated the effectiveness of phosphatic clay, a by-product of the phosphate mining industry, for immobilizing heavy metals (Pb(+2), Cd(+2), and Zn(+2)) from aqueous solutions. A batch equilibrium technique was adopted to evaluate metal sorption in the presence of 0.05 M KNO3 background electrolyte solution. The amounts of metals sorbed onto phosphatic clay decreased in the order Pb(+2) > Cd(+2) > Zn(+2). Desorption data suggest that a large fraction of metals sorbed onto phosphatic clay stayed intact under a wide variation in extracting solution pH (ranging from 3 to 10). Desorption rates were slowest for Pb followed by Cd and Zn. Only 8.1 to 23.1% of Pb, 8.4 to 45% of Cd, and 21.9 to 73.9% of Zn sorbed on phosphatic clay was mobilized by USEPA toxicity characteristic leaching procedure (TCLP) solutions at pH 2.93+/-0.05 and 4.93+/-0.05, respectively. Formation of fluoropyromorphite [Pb10(PO4)6(F2)], confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), after reaction of aqueous Pb with phosphatic clay suggested that precipitation remained the dominant mechanism for Pb removal from aqueous solution. In the case of aqueous Cd and Zn interaction with phosphatic clay, we are not able to confirm the formation of a new amorphous and/or crystalline phase on the basis of available information. Other possible sorption mechanisms for Cd and Zn may include sorption and coprecipitation. Thus, phosphatic clay may be an effective amendment for in situ immobilization of heavy metals in contaminated soils and sediments. PMID:11790002

Singh, S P; Ma, L Q; Harris, W G

2001-01-01

416

Adsorption-desorption noise in plasmonic chemical/biological sensors in multiple analyte environment  

NASA Astrophysics Data System (ADS)

We analyzed the intrinsic noise of plasmonic sensors caused by the adsorption-desorption of gaseous analytes on the sensor surface. We analyzed a general situation when there is a larger number of different species in the environment. We developed our model and applied it to calculate various analyte mixtures, including some environmental pollutants, toxic and dangerous substances. The spectral density of mean square refractive index fluctuations follows a dependence similar to that of generation-recombination noise in photodetectors, flat at lower frequencies and sh