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1

Reduction Kinetics of Graphene Oxide Determined by Electrical Transport Measurements and Temperature Programmed Desorption  

E-print Network

and Temperature Programmed Desorption Inhwa Jung, Daniel A. Field, Nicholas J. Clark, Yanwu Zhu, Dongxing Yang, Richard D. Piner, Sasha Stankovich,§ Dmitriy A. Dikin,§ Heike Geisler,| Carl A. Ventrice, Jr

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

Temperature-programmed desorption of tritium loaded into beryllium  

NASA Astrophysics Data System (ADS)

The influence of grain size and amount of beryllium oxide BeO on the tritium release characteristics of the S-65H and I-220H beryllium grades was investigated. The beryllium samples were loaded with hydrogen at a temperature of 1123 K for 6 h at a pressure of 4 bar in a gas mixture of molecular protium with 45 wppm tritium. The tritium release measurements were performed using a stepped heating ramp with steps of 50 K in the temperature range of 473-1373 K with a duration of each step of 1 h. Five major release peaks were observed. Interpretations of the nature of the peaks are suggested. In particular, we ascribe the low-temperature peaks (300-723 K) to desorption from the surface and connect the shift of the peak at elevated temperature (900-1000 K) with the enhanced diffusion of hydrogen along grain boundaries. The high temperature peak (1123-1373 K) is attributed to dissociation of beryllium hydroxide Be(OH)2, which is formed on the surface and grain boundaries of a sample in a reaction of hydrogen isotopes with beryllium oxide.

Chakin, V.; Rolli, R.; Vladimirov, P.; Kurinskiy, P.; Klimenkov, M.; Moeslang, A.; Ryczek, L.; Dorn, C.; Markovsky, A.

2009-12-01

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...

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

2007-01-01

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 present in interstellar clouds.

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

2008-11-21

6

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

NASA Astrophysics Data System (ADS)

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

Tzvetkov, George; Netzer, Falko P.

2013-07-01

7

Analyte separation utilizing temperature programmed desorption of a preconcentrator mesh  

DOEpatents

A method and system for controllably releasing contaminants from a contaminated porous metallic mesh by thermally desorbing and releasing a selected subset of contaminants from a contaminated mesh by rapidly raising the mesh to a pre-determined temperature step or plateau that has been chosen beforehand to preferentially desorb a particular chemical specie of interest, but not others. By providing a sufficiently long delay or dwell period in-between heating pulses, and by selecting the optimum plateau temperatures, then different contaminant species can be controllably released in well-defined batches at different times to a chemical detector in gaseous communication with the mesh. For some detectors, such as an Ion Mobility Spectrometer (IMS), separating different species in time before they enter the IMS allows the detector to have an enhanced selectivity.

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

2007-11-27

8

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

SciTech Connect

The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

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

1990-08-01

9

Qualitative and quantitative analysis of complex temperature-programmed desorption data by multivariate curve resolution  

NASA Astrophysics Data System (ADS)

The substantial amount of information carried in temperature-programmed desorption (TPD) experiments is often difficult to mine due to the occurrence of competing reaction pathways that produce compounds with similar mass spectrometric features. Multivariate curve resolution (MCR) is introduced as a tool capable of overcoming this problem by mathematically detecting spectral variations and correlations between several m/z traces, which is later translated into the extraction of the cracking pattern and the desorption profile for each desorbate. Different from the elegant (though complex) methods currently available to analyze TPD data, MCR analysis is applicable even when no information regarding the specific surface reaction/desorption process or the nature of the desorbing species is available. However, when available, any information can be used as constraints that guide the outcome, increasing the accuracy of the resolution. This approach is especially valuable when the compounds desorbing are different from what would be expected based on a chemical intuition, when the cracking pattern of the model test compound is difficult or impossible to obtain (because it could be unstable or very rare), and when knowing major components desorbing from the surface could in more traditional methods actually bias the quantification of minor components. The enhanced level of understanding of thermal processes achieved through MCR analysis is demonstrated by analyzing three phenomena: i) the cryogenic desorption of vinyltrimethylsilane from silicon, an introductory system where the known multilayer and monolayer components are resolved; ii) acrolein hydrogenation on a bimetallic Pt-Ni-Pt catalyst, where a rapid identification of hydrogenated products as well as other desorbing species is achieved, and iii) the thermal reaction of Ti[N(CH 3) 2] 4 on Si(100), where the products of surface decomposition are identified and an estimation of the surface composition after the thermal reaction is afforded. Since this work constitutes, to the best of our knowledge, the first effort to introduce multivariate analysis to TPD data, the procedures, algorithms and strategies employed are described in full detail.

Rodrguez-Reyes, Juan Carlos F.; Teplyakov, Andrew V.; Brown, Steven D.

2010-10-01

10

Solid-phase microextraction with temperature-programmed desorption for the analysis of iodination disinfection byproducts.  

PubMed

An analytical approach for the determination of chlorination and iodination disinfection byproducts based on solid-phase microextraction (SPME) was developed. Solid-phase microextraction presents a simple, rapid, sensitive, and solvent-free approach to sample preparation in which analytes in either air or water matrixes are extracted into the polymeric coating of an optical fiber. Analytes are subsequently thermally desorbed in the injection port of a gas chromatograph for separation, detection, and quantitation. Thermal degradation of iodoform was observed during desorption from a polyacrylate fiber in initial GC/MS and GC/ECD experiments. Experiments were designed to determine SPME conditions that would allow quantification without significant degradation of analytes. Isothermal and temperature-programmed thermal desorptions were evaluated for efficacy in transferring analytes with wide-ranging volatilities and thermal stabilities into chromatographic analysis columns. A temperature-programmed desorption (TPD) (120-200 degrees C at 5 degrees C/min with an on-column injection port or 150-200 degrees C at 25 degrees C/min with a split/splitless injection port) was able to efficiently remove analytes with wide-ranging volatilities without causing thermal degradation. The SPME-TPD method was linear over 2-3 orders of magnitude with an electron capture detector and detection limits were in the submicrogram per liter range. Precision and detection limits for selected trihalomethanes were comparable to those of EPA method 551. Extraction efficiencies were not affected by the presence of 10 mg/L soap, 15 mg/L sodium iodide, and 6000 mg/L sodium thiosulfate. The SPME-TPD technique was applied to the determination of iodination disinfection byproducts from individual precursor compounds using GC/MS and to the quantitation of iodoform at trace levels in a water recycle system using GC/ECD. PMID:9470491

Frazey, P A; Barkley, R M; Sievers, R E

1998-02-01

11

Study of temperature-programmed desorption of tert-butylamine to measure the surface acidity of solid catalysts  

SciTech Connect

In this paper, the technique of temperature-programmed desorption of tert-butylamine is described to measure the surface acidity of solid catalysts. The use of this base has advantages over the use of ammonia, pyridine, and n-butylamine. The desorption measurement is carried out by two methods, gas chromatography and thermogravimetry, and the advised conditions are described for both methods. Catalysts of SiO{sub 2}/Al{sub 2}O{sub 3}, bifunctionals of Ni-SiO{sub 2}/Al{sub 2}O{sub 3}, and a commercial cracking zeolite have been studied. A comparison of the desorption results with those of the other acidity measurement techniques (such as titration with n-butylamine in the liquid phase and kinetic measurement of isomerization of n-butenes as the test reaction) allows the acidity measured with tert-butylamine desorption to be classified as strong, corresponding to the active sites in most of the reactions among the hydrocarbon compounds catalyzed by acids.

Aguayo, A.T.; Arandes, J.M.; Olazar, M.; Bilbao, J. (Dept. de Ingenieria Quimica, Univ. del Pais, Vasco. Apartado 655, 48080 Bilbao (ES))

1991-08-01

12

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

13

Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.  

PubMed

An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release. PMID:23549366

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

2013-01-01

14

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

15

A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages  

NASA Astrophysics Data System (ADS)

In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach.

Haegel, Stefan; Zecho, Thomas; Wehner, Stefan

2010-03-01

16

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

PubMed

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

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

2013-03-30

17

Characterization of the carbonaceous residues on a used Ni/SiO[sub 2] hydrogenation catalyst by temperature-programmed desorption methods  

SciTech Connect

The carbonaceous residues formed during hydrogenation of 2-ethyl-2-hexenal (A) to 2-ethyl-hexanal (B) and 2-ethyl-hexanal (C) on a Ni/SiO[sub 2] catalyst has been studied by temperature-programmed desorption (TPD), temperature-programmed hydrogenation (TPH), temperature-programmed oxidation (TPO), and by extraction. TPD displayed below 200[degrees]C dimers, B and C. Between 200 and 400[degrees]C B, C, and alkenes were detected, and at higher temperatures alkenes and some benzenes. TPH showed the same compounds, except that methane was formed above 500[degrees]C. Both TPD and TPH produced CO, CO[sub 2], and H[sub 2]O above 450[degrees]C formed by reaction of carbonaceous deposits or H[sub 2] with unreduced NiO. TPO showed a large peak just below 400[degrees]C, a shoulder at 400-500[degrees]C, and in some experiments a small peak at about 150[degrees]C. The H/C ratio was 1.5-2.0. Above 200[degrees]C the H/C ratio increased with temperature during TPO. The total amount of carbon atoms on the surface was 10-20 times the number of surface nickel atoms indicating that carbon was also present on the support. The extract, after extraction of the used catalyst in methanol or methylene chloride, contained mainly 2-ethyl-hexanal and some 2-ethyl-hexanal. 13 refs., 8 figs., 1 tab.

Wrammersfors, A.; Andersson, B. (Chalmers Univ. of Technology, Goeteborg (Sweden))

1994-05-01

18

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

19

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

20

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

Microsoft Academic Search

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

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

1996-01-01

21

Laser desorption from a room temperature ionic liquid  

NASA Astrophysics Data System (ADS)

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

Harris, Peter Ronald

22

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

23

Water adsorption and desorption on microporous solids at elevated temperature  

Microsoft Academic Search

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

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

2005-01-01

24

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

PubMed

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

Chistiakova, M V; Armani, A M

2014-10-01

25

Development of ultralow energy (110 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids  

SciTech Connect

Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 110 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH{sub 2}{sup +}.

Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J.; Pradeep, T., E-mail: pradeep@iitm.ac.in [DST Unit of Nanoscience (DST UNS), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India); Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian [Extrel CMS, LLC, 575 Epsilon Drive, Pittsburgh, Pennsylvania 15238 (United States)] [Extrel CMS, LLC, 575 Epsilon Drive, Pittsburgh, Pennsylvania 15238 (United States)

2014-01-15

26

Influence of the sample temperature on the desorption of matrix molecules and ions in matrix-assisted laser desorption ionization  

NASA Astrophysics Data System (ADS)

The effect of the (initial) sample temperature on the threshold laser fluences and the increase of signal intensities with laser fluence has been investigated for UV-laser desorbed 2,5-dihydroxybenzoic acid (DHB) ions and (photoionized) neutral DHB molecules using a `flat-top' laser profile for desorption. A linear increase in threshold fluence with decreasing temperature was observed for neutrally desorbed molecules as well as ions in the investigated temperature range of approximately - 100[degree sign]C to + 20[degree sign]C. The results are discussed and interpreted in the framework of a quasi-thermal desorption model (IJMSIP 141 (1995) 127-148).

Schurenberg, M.; Dreisewerd, K.; Kamanabrou, S.; Hillenkamp, F.

1998-01-01

27

Water Vapor Adsorption - Desorption Behavior of a Small Piece of Desiccant Rotor in Temperature Swing  

NASA Astrophysics Data System (ADS)

This study aims to clarify the adsorption / desorption behavior of water vapor onto / from a desiccant rotor in temperature swing. A magnetic suspension balance followed time variations of the weight of a small piece of desiccant rotor at various desorption temperature, adsorption / desorption time and their duration time ratio. Adsorption-desorption swing in steady state settled down at certain amplitude of the amount adsorbed keeping the balance of the adsorption and desorption rates averaged over each period. At low regeneration temperature around 40-50 oC, adsorption and desorption rates were affected considerably by the change of driving force of adsorption q*-q rather than the temperature dependence of the mass transfer coefficient. At constant adsorption and desorption air conditions, the adsorption /desorption rates could be summarized by the amount of adsorption and temperature, independently of the length of cycle time. Also, region of the amount of adsorption at which adsorption - desorption swing occurred was predicted considering the adsorption / desorption rates - amount adsorbed relationship and the adsorption / desorption duration ratio.

Washio, Yasuko; Kodama, Akio

28

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

PubMed Central

Ultrathin (?3 ) zirconium oxide films were grown on a single-crystalline Pt3Zr(0001) substrate by oxidation in 1 107 mbar of O2 at 673 K, followed by annealing at temperatures up to 1023 K. The ZrO2 films are intended to serve as model supports for reforming catalysts and fuel cell anodes. The atomic and electronic structure and composition of the ZrO2 films were determined by synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Oxidation mainly leads to ultrathin trilayer (OZrO) films on the alloy; only a small area fraction (1015%) is covered by ZrO2 clusters (thickness ?0.510 nm). The amount of clusters decreases with increasing annealing temperature. Temperature-programmed desorption (TPD) of CO was utilized to confirm complete coverage of the Pt3Zr substrate by ZrO2, that is, formation of a closed oxide overlayer. Experiments and DFT calculations show that the core level shifts of Zr in the trilayer ZrO2 films are between those of metallic Zr and thick (bulklike) ZrO2. Therefore, the assignment of such XPS core level shifts to substoichiometric ZrOx is not necessarily correct, because these XPS signals may equally well arise from ultrathin ZrO2 films or metal/ZrO2 interfaces. Furthermore, our results indicate that the common approach of calculating core level shifts by DFT including final-state effects should be taken with care for thicker insulating films, clusters, and bulk insulators.

2014-01-01

29

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

PubMed

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

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

2011-06-16

30

Thermally stimulated desorption of neutral CF3 from CF3I on Ag(111)  

Microsoft Academic Search

The low temperature thermal chemistry of CF3I on Ag (111) presents an example of competing reaction pathways; molecular desorption vs desorption of radical CF3. Temperature programmed desorption and angle resolved temperature programmed desorption, complemented with Auger electron spectroscopy and low energy electron diffraction, were used to discern the mechanism of the CF3 radical desorption channel. CF3 desorption is limited to

K. H. Junker; Z.-J. Sun; T. B. Scoggins; J. M. White

1996-01-01

31

Effects of temperature on trichloroethylene desorption from silica gel and natural sediments. 2. Kinetics  

Microsoft Academic Search

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-stepped desorption (TSD) rates were measured for these solids in columns prepared and equilibrated at 30°C, but heated instantaneously to 60°C after nearly 1000

Charles J. Werth; Martin Reinhard

1997-01-01

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 (VOCs) 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 VOCs 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

Photon-stimulated desorption of Na from a lunar sample: temperature-dependent effects  

NASA Astrophysics Data System (ADS)

We report recent results in an investigation of source mechanisms for the origin of Na atoms in tenuous planetary atmospheres, focusing on non-thermal processes. Experiments include photon stimulated desorption (PSD), electron stimulated desorption (ESD), and ion sputtering of Na atoms from the surface of a lunar basalt sample. Bombardment of the sodium covered surface by 3 keV Ar + ions removes Na from the surface by sputtering into vacuum and by implantation into the sample bulk. Bombardment of the Na covered surface by ultraviolet photons or by low energy electrons ( E>3 to 4 eV) causes desorption of "hot" Na atoms. These results are consistent with our previous measurements of sodium and potassium desorption from a silica surface: electron- or photon-induced charge transfer from the substrate to the ionic adsorbate causes formation of a neutral alkali atom in a repulsive configuration, from which desorption occurs. There is a strong temperature-dependence of Na ESD and PSD signals, under conditions where the Na surface coverage is constant and thermal desorption is negligible. The yield of Na (atoms/photon) increases by 10 from 100 to 470 K; an activation energy of 20 meV is measured. This phenomenon may be attributed to thermally-induced changes in surface bonding sites, and will affect recent modeling of the sodium atmospheres of Mercury and the Moon.

Yakshinskiy, Boris V.; Madey, Theodore E.

2004-03-01

34

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

PubMed

Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420-841 ?m and fine soil with particles <250 ?m. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 C; at 600 C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer. PMID:24352542

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

2014-03-01

35

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

36

Mechanisms for gas adsorption and desorption in silica aerogels: the effect of temperature.  

PubMed

We present a theoretical study of the adsorption and desorption mechanisms of fluids in silica aerogels, focusing on the effect of temperature. We adopt a coarse-grained lattice description in which the gel structure is generated by a diffusion-limited cluster-cluster aggregation algorithm and the fluid configurations are computed using local mean-field (i.e., density functional) theory. Our calculations reproduce qualitatively the changes in the shape of the hysteresis loops observed with (4)He in gels of varying porosity. We study in detail the morphology of the condensation and evaporation events that correspond to the irreversible processes (avalanches) which are at the origin of the hysteresis. Depending on porosity and temperature, these avalanches may be localized, involve regions that extend beyond the gel correlation length, or even span the entire sample. This makes difficult the characterization of aerogels based on analyzing sorption isotherms. PMID:15350065

Detcheverry, F; Kierlik, E; Rosinberg, M L; Tarjus, G

2004-09-14

37

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

SciTech Connect

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

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

1999-12-07

38

Concept of a Single Temperature for Highly Nonequilibrium Laser-Induced Hydrogen Desorption from a Ruthenium Surface  

NASA Astrophysics Data System (ADS)

Laser-induced condensed phase reactions are often interpreted as nonequilibrium phenomena that go beyond conventional thermodynamics. Here, we show by Langevin dynamics and for the example of femtosecond-laser desorption of hydrogen from a ruthenium surface that light adsorbates thermalize rapidly due to ultrafast energy redistribution after laser excitation. Despite the complex reaction mechanism involving hot electrons in the surface region, all desorption product properties are characterized by equilibrium distributions associated with a single, unique temperature. This represents an example of ultrahot chemistry on the subpicosecond time scale.

Fchsel, G.; Tremblay, J. C.; Klamroth, T.; Saalfrank, P.; Frischkorn, C.

2012-08-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

40

Diffusion-promoted-desorption mechanism for D 2 desorption from Si(100) surfaces  

NASA Astrophysics Data System (ADS)

Temperature-programmed-desorption (TPD) spectra and isothermal desorption rates of D 2 molecules from a Si(100) surface have been calculated to reproduce experimental ?1, A -TPD spectra and isothermal desorption rate curves. In the diffusion-promoted-desorption (DPD) mechanism, hydrogen desorption from the Si(100) (2 1) surfaces takes place via D atom diffusion from doubly-occupied Si dimers (DODs) to their adjacent unoccupied Si dimers (UODs). Taking a clustering interaction among DODs into consideration, coverages ?DU of desorption sites consisting of a pair of a DOD and UOD are evaluated by a Monte Carlo (MC) method. The TPD spectra for the ?1, A peak are obtained by numerically integrating the desorption rate equation R = ?A exp(- Ed, A / kBT) ?DU, where ?A is the pre-exponential factor and Ed, A is the desorption barrier. The TPD spectra calculated for Ed, A = 1. 6 eV and ?A = 2.7 10 9 /s are found to be in good agreement with the experimental TPD data for a wide coverage range from 0.01 to 0.74 ML. Namely, the deviation from first-order kinetics observed in the coverage dependent TPD spectra as well as in the isothermal desorption rate curves can be reproduced by the model simulations. This success in reproducing both the experimental TPD data and the very low desorption barrier validates the proposed DPD mechanism.

Narita, Y.; Inanaga, S.; Unoko, C.; Namiki, A.

2011-01-01

41

Retrospective identification of chemical warfare agents by high-temperature automatic thermal desorptiongas chromatographymass spectrometry  

Microsoft Academic Search

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

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

2001-01-01

42

Desorption Kinetics of Methanol, Ethanol, and Water from Graphene  

SciTech Connect

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

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

2014-09-18

43

Desorption kinetics of methanol, ethanol, and water from graphene.  

PubMed

The desorption kinetics of methanol, ethanol, and water from graphene covered Pt(111) are investigated. The temperature programmed desorption (TPD) spectra for both methanol and ethanol have well-resolved first, second, third, and multilayer layer desorption peaks. The alignment of the leading edges is consistent with zero-order desorption kinetics from all layers. In contrast, for water, the first and second layers are not resolved. At low water coverages (<1 monolayer (ML)) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10-100 ML), the desorption leading edges are in alignment throughout the desorption of the film. The coverage dependence of the desorption behavoir suggests that at low water coverages the nonalignment of the desorption leading edges is due to water dewetting from the graphene substrate. Kinetic simulations reveal that the experimental results are consistent with zero-order desorption. The simulations also show that fractional order desorption kinetics would be readily apparent in the experimental TPD spectra. PMID:24654652

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

2014-09-18

44

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

NASA Astrophysics Data System (ADS)

The water formation reaction has been studied on a hot polycrystalline palladium catalyst and a theoretical model has been derived with Chemkin in order to fit the experimental data. The results were compared with similar studies for platinum. The H 2/O 2 reaction was measured with LIF and microcalorimetry on palladium at a temperature of 1300 K, pressures of 13 and 26 Pa and flows of 100 and 200 SCCM. The experiments were performed in a stagnation-point flow field, which was also the geometry modelled with Chemkin. The maximum in water production as a function of ?H 2 ( ?H 2,H 2O max), occurs at about 20% on platinum, while it occurs at about 40-45% on palladium; ?H 2 is the hydrogen mixing ratio. However, the maximum in OH desorption ( ?H 2,OH max), occurs at about the same ?H 2 for both palladium and platinum. In order that the theoretical model would match the experimental data for palladium it was necessary to assume a coverage dependent OH desorption energy, Ead,OH, according to Ead,OH( ?)= Ead,OH(0)- B?, where B is a constant equal to 100 kJ/mol. The apparent desorption energy for OH on palladium was also measured at ?H 2=17% to 200 kJ/mol and ?H 2=45% to 220 kJ/mol. The main water-forming reaction on platinum is thought to be the hydrogen addition reaction H * + OH * ? H 2O *. For palladium, there are difficulties to determine the main water formation route because the OH desorption energy is believed to be coverage dependent. The reverse of reaction H * + OH * ? H 2O * seems to have greater importance for the OH formation on palladium than on platinum. The initial sticking coefficient of hydrogen and oxygen is found to be greater on palladium than on platinum by a factor of about 10.

Johansson, .; Frsth, M.; Rosn, A.

2003-04-01

45

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

PubMed

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. PMID:25362420

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

2014-10-01

46

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

47

Temperature and concentration effects in electron-stimulated desorption of sodium atoms from sodium layers adsorbed on tungsten coated with a gold film  

NASA Astrophysics Data System (ADS)

The yield and energy distributions of sodium atoms upon electron-stimulated desorption from sodium layers adsorbed on tungsten coated with a gold film are investigated for the first time as functions of the thickness of the gold film, the concentration of deposited sodium, and the surface temperature. It is found that the energy distributions exhibit two peaks, namely, a narrow peak with a maximum at about 0.15 eV, whose intensity continuously increases with increasing temperature, and a broad peak with a maximum at about 0.35 eV, whose intensity either decreases or remains constant with increasing temperature. It is shown that both peaks arise as a result of the same excitation, which gives rise to different channels of electron-stimulated desorption of sodium atoms. Possible mechanisms of electron-stimulated desorption and the kinetics of destruction of the surface coating are discussed.

Ageev, V. N.; Kuznetsov, Yu. A.; Potekhina, N. D.

2008-08-01

48

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

PubMed

An automated thermal desorption (ATD)-gas chromatography-mass spectrometry method was developed for the analysis of selected chemical warfare (CW) agents. Suitable methods were developed for analytes of high volatility to low volatility. The less volatile CW agents required the purchase and installation of a high-temperature valve upgrade kit allowing valve temperatures of up to 260 degrees C to be reached. The limit of detection was 50 ng on the tube for most CW agents in full scan. Chloropicrin exhibited some temperature dependence, with detection limits improving as ATD temperatures were decreased below 150 degrees C. A sample storage trial was undertaken to establish the most suitable storage environment for CW agents adsorbed onto Tenax TA. Temperature and time of storage were found to influence recovery of analytes with best recoveries being observed after 1 day storage in a freezer (-12 degrees C). This method was evaluated during a trial of procedures for sampling and identification of chemical agents at Porton Down, UK. Sulfur mustard was detected downwind of a simulated exploded munition. PMID:11519809

Carrick, W A; Cooper, D B; Muir, B

2001-08-01

49

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

SciTech Connect

We find that NO dosed on rutile TiO2(110)-11 at substrate temperatures as low as 50 K readily reacts to produce N2O which desorbs promptly from the surface leaving an oxygen adatom behind. The desorption rate of N2O reaches a maximum value after 1 2 sec at an NO flux of 1.2 1014 NO/cm2?sec and then decreases rapidly as the initially clean, reduced TiO2(110) surface with ~5% oxygen vacancies (VOs) becomes covered with oxygen adatoms and unreacted NO. The maximum desorption rate is also found to increase as the substrate temperature is raised up to about 100 K. Interestingly, the N2O desorption during the low-temperature (LT) NO dose is strongly suppressed when molecular oxygen is predosed, whereas it persists on the surface with VOs passivated by surface hydroxyls. Our results show that the surface charge, not the VO sites, plays a dominant role in the LT N2O desorption induced by a facile NO reduction at such low temperatures.

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

2014-05-08

50

Ion desorption from molecules condensed at low temperature: A study with electron-ion coincidence spectroscopy combined with synchrotron radiation (Review)  

NASA Astrophysics Data System (ADS)

This article reviews our recent work on photostimulated ion desorption (PSID) from molecules condensed at low temperature. We have used electron-ion coincidence (EICO) spectroscopy combined with synchrotron radiation. The history and present status of the EICO apparatus is described, as well as our recent investigations of condensed H2O, NH3, CH3CN, and CF3CH3. Auger electron photon coincidence (AEPICO) spectra of condensed H2O at the O:1s ionization showed that H+ desorption was stimulated by O:KVV Auger processes leading to two-hole states (normal-Auger stimulated ion desorption (ASID) mechanism). The driving forces for H+ desorption were attributed to the electron missing in the O-H bonding orbitals and the effective hole-hole Coulomb repulsion. The normal ASID mechanism was also demonstrated for condensed NH3. The H+ desorption at the 4a1?O(N):1s resonance of both condensed H2O and condensed NH3 was found to be greatly enhanced. Based on the AEPICO spectra the following four-step mechanism was proposed: (1) the 4a1?1s transition, (2) extension of the HO-H (H2N-H) distance within the lifetime of the (1s)-1(4a1)1 state, (3) spectator Auger transitions leading to (valence)-2(4a1)1 states, and (4) H+ desorption. The enhancement of the H+ desorption yield was attributed to the repulsive potential surface of the (1s)-1(4a1)1 state. At the 3p?O:1s resonance of condensed H2O, on the other hand, the H+ yield was found to be decreased. The AEPICO spectra showed that the H+ desorption was stimulated by spectator Auger transitions leading to (valence)-2(3p)1 states. The decrease in the H+ yield was attributed to a reduction in the effective hole-hole Coulomb repulsion due to shielding by the 3p electron. Photoelectron photon coincidence (PEPICO) spectra of condensed H2O showed that the core level of the surface H2O responsible for the H+ desorption was shifted by 0.7 eV from that of the bulk H2O. The H+ desorption from condensed CH3CN was also investigated. In a study of condensed CF3CH3 using PEPICO spectroscopy, site-specific ion desorption was directly verified; that is, H+ and CH3+ desorption was predominant for the C:1s photoionization at the -CH3 site, while C2Hn+, CFCHm+, and CF3+ desorption was predominantly induced by the C:1s photoionization at the -CF3 site. These investigations demonstrate that EICO spectroscopy combined with synchrotron radiation is a powerful tool for studying PSID of molecules condensed at low temperature.

Mase, Kazuhiko; Nagasono, Mitsuru; Tanaka, Shin-ichiro; Sekitani, Tetsuji; Nagaoka, Shin-ichi

2003-03-01

51

Desorption of Hg(II) and Sb(V) on extracellular polymeric substances: effects of pH, EDTA, Ca(II) and temperature shocks.  

PubMed

Extracellular polymeric substances (EPS) existed ubiquitously in biological systems affect the mobility and availability of heavy metals in the environments. The adsorption-desorption behaviors of Hg(II) and Sb(V) on EPS were investigated. The sorption rates follow Sb(V) > Hg(II), and the desorption rates follow reverse order. Applications of ethylene diamine tetraacetic acid (EDTA), Ca(II) and pH shocks affect desorption rates and desorbed quantities of Hg(II) from EPS-Hg complex. Temperature shock minimally affects the desorption rate of Hg(II). Conversely, the EPS-Sb complex is stable subjected to EDTA, Ca(II), temperature or pH shocks. The excitation-emission matrix (EEM) fluorescence spectroscopy and fast-Fourier (FT-IR) analysis showed that Hg(II) and Sb(V) principally interacted with polysaccharides and protein-like compounds in the EPS, respectively. The EPS-Hg complex presents a time bomb that may release high levels of Hg(II) in short time period under environmental shocks. PMID:23247408

Zhang, Daoyong; Lee, Duu-Jong; Pan, Xiangliang

2013-01-01

52

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

E-print Network

Interaction of Acetone with Single Wall Carbon Nanotubes at Cryogenic Temperatures: A Combined The interaction of acetone with single wall carbon nanotubes (SWCNTs) at low temperatures was studied simulations, the desorption peaks of acetone can be assigned to the following adsorption sites: (i) sites

Borguet, Eric

53

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

SciTech Connect

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

Not Available

1980-06-01

54

Oxidation of Zircaloy-4 by H 2O followed by molecular desorption  

NASA Astrophysics Data System (ADS)

The interaction of H 2O with Zircaloy-4 (Zry-4) is investigated using Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) methods. Following adsorption of H 2O at 150 K the Zr(MNV) and Zr(MNN) Auger features shift by 6.5 and 4.5 eV, respectively, indicating surface oxidation. Heating H 2O/Zry-4 results in molecular desorption of water at both low and high temperatures. The low-temperature desorption is attributed to ice multilayers, whereas, three overlapping high-temperature features are presumably due to recombinative desorption. This high-temperature desorption begins before the surface oxide is dissolved, continues upon its removal, and is atypical for water/metal systems. Unexpectedly, no significant desorption of hydrogen is observed near 400 K, as is typically observed following O 2 adsorption on Zr-based materials. However, we do observe that H 2O adsorption on Zry-4 surfaces roughened by argon ion sputtering results in H 2 desorption.

Stojilovic, N.; Ramsier, R. D.

2006-06-01

55

Characterization of Biochar using Temperature Programmed Oxidation  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

56

Thermal desorption of circumstellar and cometary ice analogs  

NASA Astrophysics Data System (ADS)

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

Martn-Domnech, R.; Muoz Caro, G. M.; Bueno, J.; Goesmann, F.

2014-04-01

57

A STUDY OF ETHANOL REACTIONS OVER Pt\\/Al2O3 AND Pt\\/ZrO2 BY TEMPERATURE-PROGRAMMED SURFACE REACTION  

Microsoft Academic Search

The platinum supported catalysts were investigated by temperature-programmed desorption (TPD) and temperature-programmed surface reaction (TPSR), using He and 5% O2\\/He. Through a half-quantitative analysis of TPD, it was observed that the acidic sites of alumina favors the dehydration of ethanol, since the formation of ethylene in the Pt\\/Al2O3 catalyst is more significant. Despite the little formation of acetaldehyde in both

Carlos E. M. Guarido; Mariana M. V. M. Souza; Martin Schmal

58

Associative Electron Stimulated Desorption of Neutral CO Molecules  

NASA Astrophysics Data System (ADS)

The Electron Stimulated Desorption (ESD) of neutral CO molecules was studied on polycrystalline Ni surface. Combined ESD and temperature programmed desorption (TPD) measurements were used to observe the variations of neutral ESD yield in dependence on CO coverage, containing direct information about the cross section for ESD of neutral CO molecules in relation to various CO adsorption states. The results show evidence of ESD of neutral CO molecules from dissociative adsorption states. The cross section for this associative ESD process is relatively high in comparison with the CO ESD cross section for molecular CO adsorption.

utara, F.; Matoln, V.

2001-11-01

59

STP Temperature Measurement Lennard-Jones Program  

NSDL National Science Digital Library

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

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

2009-03-03

60

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

NASA Astrophysics Data System (ADS)

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

Narita, Yuzuru; Inanaga, Shoji; Namiki, Akira

2013-06-01

61

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

62

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

NASA Astrophysics Data System (ADS)

Electron stimulated molecular desorption (ESD) from a non-evaporable getters (NEG) St 707 (SAES Getters ) sample after conditioning and after saturation with isotopic carbon monoxide (cf. nomenclature in Handbook of Chemistry and Physics, CRC Press, 1994), 13C 18O, has been studied on a laboratory setup. Measurements were performed using an electron beam of 300 eV kinetic energy, with an average electron intensity of 1.610 15 electrons s -1. The electrons were impinging on the 15 cm 2 target surface at perpendicular incidence. It is found that the desorption yields ? (molecules/electron) of the characteristic gases in an UHV system (hydrogen, methane, water, carbon monoxide, carbon dioxide) for a fully activated NEG as well as for a NEG fully saturated with 13C 18O are lower than for OFHC copper baked at 120 C. A small fraction only of the gas which is required to saturate the getter surface can be re-desorbed and thus appears to be accessible to ESD.

Le Pimpec, F.; Grbner, O.; Laurent, J. M.

2002-10-01

63

Enantiospecific Desorption of Chiral Compounds from Chiral Cu(643) and Achiral Cu(111) Surfaces  

E-print Network

molecules on the Cu(643) surfaces. There are several high-temperature features in the TPD spectra: Temperature-programmed desorption (TPD) experiments have been conducted to investigate enantiospecific such as Cu have kinked and stepped structures which are nonsuperimposable mirror images of one another

Gellman, Andrew J.

64

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

65

Low-Temperature Power Electronics Program  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

67

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

NASA Astrophysics Data System (ADS)

In this (Paper II) and the preceding companion paper (Paper I; R. May, R. Smith, and B. Kay, J. Chem. Phys. 138, 104501 (2013), 10.1063/1.4793311), we investigate the mechanisms for the release of trapped gases from underneath amorphous solid water (ASW) films. In Paper I, we focused on the low coverage regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime, the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that these abrupt desorption bursts are due to pressure induced structural failure of the ASW overlayer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores formed during ASW deposition. The extent of desorption and the line shape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of ASW is used to vary the porosity of the overlayer and strongly supports the hypothesis that the low temperature desorption pathway is due to porosity that is templated into the ASW overlayer by the underlayer during deposition.

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

2013-03-01

68

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

69

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

70

In?uence of temperature and atmosphere on polychlorinated dibenzo-p-dioxins and dibenzofurans desorption from waste incineration fly ash.  

PubMed

A fly ash sample was heated for 1?h to 200C, 300C and 400C, in order to study the influence of temperature and gas phase composition on the removal of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from fly ash derived from municipal solid waste incineration. The tests were conducted by treating a fixed bed of fly ash both in an inert (nitrogen) and in a reducing (nitrogen?+?hydrogen) gas flow in a horizontal bench-scale quartz tubular reactor, heated by a surrounding tubular furnace. The results indicate that most of the PCDD/Fs in fly ash were removed by thermal treatment, especially when the temperature was higher than 300C: the PCDD/Fs' removal efficiency attained up to 96%. PCDD/Fs dechlorination and destruction were much more important than PCDD/Fs desorption, under either inert or reducing atmosphere. At 200C and 300C, the experiments with reducing atmosphere yielded slightly better results than those in nitrogen; yet, this tendency was reversed at 400C. In general, both treatment modes can fully meet the requirements regarding the concentration of dioxins in fly ash to be sent for landfill in China. PMID:25241904

Yang, Jie; Yan, Mi; Li, Xiaodong; Chen, Tong; Lu, Shengyong; Yan, Jianhua; Buekens, Alfons

2015-03-01

71

Temperature programmed decomposition of uranyl nitrate hexahydrate  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

72

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

SciTech Connect

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

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

2011-12-31

73

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

74

Thermal Desorption of Galliumchloride Adsorbed on GaAs (100)  

NASA Astrophysics Data System (ADS)

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

Sasaoka, Chiaki; Kato, Yoshitake; Usui, Akira

1991-10-01

75

The NASA high temperature superconductivity program  

NASA Technical Reports Server (NTRS)

It has been recognized from the onset that high temperature superconductivity held great promise for major advances across a broad range of NASA interests. The current effort is organized around four key areas: communications and data, sensors and cryogenics, propulsion and power, and space materials technology. Recently, laser ablated YBa2Cu3O(7-x) films on LaAIO produced far superior RF characteristics when compared to metallic films on the same substrate. This achievement has enabled a number of unique microwave device applications, such as low insertion loss phase shifters and high Q filters. Melt texturing and melt quenched techniques are being used to produce bulk materials with optimized magnetic properties. These yttrium enriched materials possess enhanced flux pinning characteristics and will lead to prototype cryocooler bearings. Significant progress has also occurred in bolometer and current lead technology. Studies are being conducted to evaluate the effect of high temperature superconducting materials on the performance and life of high power magneto-plasma-dynamic thrusters. Extended studies were also performed to evaluate the benefit of superconducting magnetic energy storage for LEO space station, lunar and Mars mission applications. The project direction and level of effort of the program are also described.

Sokoloski, Martin M.; Romanofsky, Robert R.

1990-01-01

76

Time-resolved photodissociation study of singly protonated peptides with a histidine residue generated by matrix-assisted laser desorption ionization: dissociation rate constant and internal temperature.  

PubMed

Product ion yields in post-source decay and time-resolved photodissociation at 193 and 266 nm were measured for some peptide ions with a histidine residue ([HF(6) + H](+), [F(6)H + H](+), and [F(3)HF(3) + H](+)) formed by matrix-assisted laser desorption ionization (MALDI). Compared with similar data for peptide ions without any basic residue reported previously, significant reduction in dissociation efficiency was observed. Internal temperatures (T) of the peptide ions and their dissociation kinetic parameters-the critical energy (E(0)) and entropy (DeltaS(double dagger))-were determined by the method reported previously. Slight decreases in E(0), DeltaS(double dagger), and T were responsible for the histidine effect-reduction in dissociation rate constant. Regardless of the presence of the residue, DeltaS(double dagger) was far more negative than previous quantum chemical results. Based on this, we propose the existence of transition structures in which the nitrogen atoms in the histidine residue or at the N-terminus coordinate to the reaction centers. Reduction in T in the presence of a histidine residue could not be explained based on popular models for ion formation in MALDI, such as the gas-phase proton transfer model. PMID:19467884

Yoon, So Hee; Moon, Jeong Hee; Kim, Myung Soo

2009-08-01

77

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

78

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

79

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

SciTech Connect

Isotopic labeling experiments have revealed correlations between hydrogen reactions, Ga desorption, and ammonia decomposition in GaN CVD. Low energy electron diffraction (LEED) and temperature programmed desorption (TPD) were used to demonstrate that hydrogen atoms are available on the surface for reaction after exposing GaN(0001) to deuterium at elevated temperatures. Hydrogen reactions also lowered the temperature for Ga desorption significantly. Ammonia did not decompose on the surface before hydrogen exposure. However, after hydrogen reactions altered the surface, N15H3 did undergo both reversible and irreversible decomposition. This also resulted in the desorption of N2 of mixed isotopes below the onset of GaN sublimation, This suggests that the driving force of the high nitrogen-nitrogen bond strength (226 kcal/mol) can lead to the removal of nitrogen from the substrate when the surface is nitrogen rich. Overall, these findings indicate that hydrogen can influence G-aN CVD significantly, being a common factor in the reactivity of the surface, the desorption of Ga, and the decomposition of ammonia.

Bartram, Michael E.; Creighton, J. Randall

1999-05-26

80

Evaluation of biochars by temperature programmed oxidation/mass spectroscopy  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

81

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

82

Photodissociation and desorption of multilayer acetone on a Si(100) surface by 193 nm laser irradiation  

NASA Astrophysics Data System (ADS)

Thermal desorption spectra of acetone on Si(100) were measured using a temperature programmed desorption (TPD) technique. Acetone molecules condensed on a Si(100) at 95 K desorbed at 133 K. The peak profile indicated a zeroth-order desorption mechanism. The desorption energy was estimated to be 47.6 4 kJ/mol. Dissociation and desorption of the acetone molecules condensed on the surface by 193 nm pulsed laser irradiation were investigated with a quadrupole mass spectrometer using a time-of-flight technique. When high fluence laser pulses of 363 mJ/cm 2 were irradiated to a thick layer of acetone formed by an exposure of 1500 L, hyperthermal acetone molecules of about 2 eV were observed desorbing from the surface. Acetyl and methyl radicals formed by dissociation were also vaporized simultaneously. Thermal dissociation of acetone leading to 2CH 3 and CO as products occurred slowly after the laser irradiation. These dissociation processes are different from those in the gas phase.

Kusunoki, I.; Sakashita, M.; Takaoka, T.; Range, H.

1996-06-01

83

Thermal desorption of hydrogen from graphane  

NASA Astrophysics Data System (ADS)

The process of hydrogen desorption from graphane (graphene sheet saturated by hydrogen adsorbed from both sides) has been studied using the method of molecular dynamics. The temperature dependences of the time of desorption onset for various hydrogen coverages on graphene are calculated and the corresponding activation energies in the Arrhenius equation are determined. It is established that graphane exhibits a rather high thermal stability that makes possible its use in two-dimensional electronics even at room temperature. For the same reason, graphane can hardly be considered as a promising hydrogen storage material for fuel cells.

Openov, L. A.; Podlivaev, A. I.

2010-01-01

84

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

85

Deconvolving Ocean Drilling Program temperature logging tool data to improve borehole temperature estimates: Chile Triple Junction  

Microsoft Academic Search

We present a technique for correcting borehole fluid temperature observations made by the Ocean Drilling Program (ODP) with the Lamont temperature logging tool (TLT), for the effects of the slow temperature response of one of its sensors. TLT data have been recorded in many ODP boreholes, but, perhaps partly because of tool response effects, the data have only rarely been

Dale S. Sawyer; Nathan L. Bangs; Xenia Golovchenko

1994-01-01

86

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

SciTech Connect

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

Taylor-Pashow, K.; Hobbs, D.

2011-06-10

87

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

88

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

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

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

1995-01-01

89

Desorption-induced recombination-cationization of metal-adsorbate adducts from sulfur precovered Ru(0001)  

NASA Astrophysics Data System (ADS)

Temperature programmed static secondary ion mass spectrometry (TPSS) studies of pyrrole, furan and water on sulfur precovered Ru(0001) reveal significant increases in the coverage corrected adduct yield when these species desorb from the surface in an autocatalytic fashion. This effect has been attributed to an enhancement in the recombination-cationization rate which occurs when sputtered-ruthenium species contact desorbed organics just after leaving the surface. Adsorbates which do not undergo autocatalytic/explosive desorption do not exhibit this effect.

Cocco, R. A.; Tatarchuk, B. J.

1990-03-01

90

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

NASA Technical Reports Server (NTRS)

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

Gray, Hugh R.; Ginty, Carol A.

1992-01-01

91

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

Microsoft Academic Search

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

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

1997-01-01

92

Enantiospecific desorption of R- and S-propylene oxide from D- or L-lysine modified Cu(100) surfaces.  

PubMed

The enantiospecific desorption kinetics of R- and S-propylene oxide (PO) from a Cu(100) surface modified by enantiomerically pure D- or L-lysine have been studied using temperature programmed desorption. These experiments have used R- or S-PO as the chiral probe for study of enantiospecific adsorption on Cu(100) surfaces modified with D- or L-lysine. This chiral probe/modifier/Cu system manifests a significant diastereomeric effect in the R- and S-PO peak desorption temperatures and, hence, true enantiospecific behavior. The enantiospecificity in the PO desorption kinetics is observed only over a narrow range of lysine modifier coverage with a maximum at a lysine coverage leaving an empty site density of ?(O) ? 0.25. The observation of enantiospecific behavior in the PO/lysine/Cu(100) system is in contrast with the failed results of prior attempts to observe enantiospecific desorption from chirally modified Cu surfaces. The potential for hydrogen-bonding interactions between the chiral probe and chiral modifier, which can depend on the coverage and configuration of the adsorbed modifier, may play a crucial role in enantiospecific adsorption on lysine modified Cu surfaces. PMID:23020648

Cheong, Wai Yeng; Gellman, Andrew J

2012-10-30

93

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

NASA Technical Reports Server (NTRS)

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

Ginty, Carol A.; Gray, Hugh R.

1992-01-01

94

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

95

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

96

[Adsorption-desorption performance of honeycomb-shaped activated carbon].  

PubMed

Honeycomb-shaped activated carbon is useful to control organic gas pollution of large air-flow and low concentration. Effects of adsorbents, toluene concentration, velocity of empty bed and temperature of desorption on its adsorption-desorption performance were studied by conducting on dynamic experiments. Results shown that adsorption properties of honeycomb-shaped activated carbon were increased with decreasing of the inlet toluene concentration under the condition of certain outlet toluene concentration, and gas velocity of empty bed was recommend as 1.2-1.8 m x s(-1). With increasing of the desorption temperature, the outlet toluene concentration appeared peak-value and fluctuated widely, and the recommended desorption temperature was 90 degrees C. Gas velocity of empty bed affected the peak value of concentration of the toluene, and practical value was 0.2-0.4 m x s(-1). PMID:22468536

Han, Zhong-Juan; Luo, Fu-Kun; Li, Ze-Qing

2011-12-01

97

Desorption atmospheric pressure photoionization.  

PubMed

An ambient ionization technique for mass spectrometry, desorption atmospheric pressure photoionization (DAPPI), is presented, and its application to the rapid analysis of compounds of various polarities on surfaces is demonstrated. The DAPPI technique relies on a heated nebulizer microchip delivering a heated jet of vaporized solvent, e.g., toluene, and a photoionization lamp emitting 10-eV photons. The solvent jet is directed toward sample spots on a surface, causing the desorption of analytes from the surface. The photons emitted by the lamp ionize the analytes, which are then directed into the mass spectrometer. The limits of detection obtained with DAPPI were in the range of 56-670 fmol. Also, the direct analysis of pharmaceuticals from a tablet surface was successfully demonstrated. A comparison of the performance of DAPPI with that of the popular desorption electrospray ionization method was done with four standard compounds. DAPPI was shown to be equally or more sensitive especially in the case of less polar analytes. PMID:17803282

Haapala, Markus; Pl, Jaroslav; Saarela, Ville; Arvola, Ville; Kotiaho, Tapio; Ketola, Raimo A; Franssila, Sami; Kauppila, Tiina J; Kostiainen, Risto

2007-10-15

98

Temperature-programmed oxidation of equilibrium fluid catalytic cracking catalysts  

Microsoft Academic Search

Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals was investigated\\u000a using temperature-programmed oxidation (TPO). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy\\u000a gas oil (SIHGO) were deconvoluted into four peaks (Peak K, L, M and N). The four peaks were assigned to different types of\\u000a coke on the catalyst. Peak L

O. Bayraktar; E. L. Kugler

2004-01-01

99

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

Microsoft Academic Search

Thermal desorption profiles were modelled based on SIMS measurements of implantation profiles and using the multi-trap diffusion code TMAP7 [G.R. Longhurst, TMAP7: Tritium Migration Analysis Program, User Manual, Idaho National Laboratory, INEEL\\/EXT-04-02352 (2004)]. The thermal desorption profiles were the result of 500eV\\/D+ irradiations on single crystal tungsten at 300 and 500K to fluences of 10221024D+\\/m2. SIMS depth profiling was performed

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

2008-01-01

100

The interaction of water with clean palladium films: A thermal desorption and work function study  

NASA Astrophysics Data System (ADS)

The adsorption-thermodesorption behavior of H 2O molecules on clean, thin polycrystalline Pd-films has been studied by means of work function (WF) and mass resolved temperature programmed desorption (TPD). Film morphology was varied and stabilized by annealing in the range 77-473 K. As deduced from WF changes during adsorption and TPD, unannealed films formed on glass at 77 K are highly porous. On the films at 77 K, H 2O adsorbs molecularly and binds to the surface through the O-atom as suggested by the decrease in work function. Data can be rationalized assuming that during TPD, the adsorbed H 2O molecules undergo decomposition. H 2 never evolved from the films, not even at 473 K, suggesting that the observed H 2O desorption peak at T>220 K should involve molecule rebuilding, as found in Pd single crystals.

Heras, J. M.; Esti, G.; Viscido, L.

1997-04-01

101

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

102

Deconvolving Ocean Drilling Program temperature logging tool data to improve borehole temperature estimates: Chile Triple Junction  

NASA Astrophysics Data System (ADS)

We present a technique for correcting borehole fluid temperature observations made by the Ocean Drilling Program (ODP) with the Lamont temperature logging tool (TLT), for the effects of the slow temperature response of one of its sensors. TLT data have been recorded in many ODP boreholes, but, perhaps partly because of tool response effects, the data have only rarely been used. It has been shown that a continuous temperature log is the convolution of a tool response function and the temperature history experienced by the tool. We use temperature data from ODP Leg 141 to estimate the tool response function of the TLT. We then use Wiener filter theory to design a decon volution operator to remove the effect of the tool response from the recorded data. We apply the deconvolution operator to the data from Leg 141, assess the effectiveness of the deconvolution technique, and extrapolate the resulting borehole fluid temperatures to estimate the equilibrium geotherm at the two sites considered. The geothermal gradient in the accretionary wedge near the Chile Triple Junction increases with depth. This suggests that the thermal environment is not steady state, that fluid flow is transporting heat, or, most likely, both. The average heat flow in the accretionary wedge near the Chile Triple Junction is higher over the subducting Chile Ridge axis than over subducting young oceanic crust near the ridge axis.

Sawyer, Dale S.; Bangs, Nathan L.; Golovchenko, Xenia

1994-06-01

103

Hydrogen absorption and desorption by the Li-Al-N-H system.  

PubMed

Lithium hexahydridoaluminate Li(3)AlH(6) and lithium amide LiNH(2) with 1:2 molar ratio were mechanically milled, yielding a Li-Al-N-H system. LiNH(2) destabilized Li(3)AlH(6) during the dehydrogenation process of Li(3)AlH(6), because the dehydrogenation starting temperature of the Li-Al-N-H system was lower than that of Li(3)AlH(6). Temperature-programmed desorption scans of the Li-Al-N-H system indicated that a large amount of hydrogen (6.9 wt %) can be released between 370 and 773 K. After initial H(2) desorption, the H(2) absorption and the desorption capacities of the Li-Al-N-H system with a nano-Ni catalyst exhibited 3-4 wt % at 10-0.004 MPa and 473-573 K, while the capacities of the system without the catalyst were 1-2 wt %. The remarkably increased capacity was due to the fact that the kinetics was improved by addition of the nano-Ni catalyst. PMID:16686512

Kojima, Yoshitsugu; Matsumoto, Mitsuru; Kawai, Yasuaki; Haga, Tetsuya; Ohba, Nobuko; Miwa, Kazutoshi; Towata, Shin-ichi; Nakamori, Yuko; Orimo, Shin-ichi

2006-05-18

104

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

105

[Desorption isotherms in amaranth flours].  

PubMed

In milled seeds amaranth (Amaranthus hybridus) samples locally known as "ataco or sangoracha" and harvested in two consecutive years, the vapor pressure at four temperatures (15 degrees, 20 degrees, 25 degrees, 30 degrees C) was determined in samples obtained for drying in oven at different times, within a range between 60 g water/100 g dry matter for fresh seeds to 10 g water/100 g dry matter or below, as measured in a Brabender equipment. Vapor pressure of distilled water was also determined for water activity calculation. The isotherms for each temperature are presented. Application of the G.A.B. model (Guggenheim-Anderson-De Boer) allowed to establish the water content of greater stability within a range of 9.9 to 7.6 g/100 g. The third degree polynomial equations presented, adjust satisfactorily with the experimental data, and can be used to calculate equilibrium moisture content from 0.15 to 0.95 water activity values. Water desorption isotherms of foods are important to determine the equilibrium relationship between the moisture content of foods and the water activity, information which permits to establish likely physical, chemical or biological changes. It is considered that the results obtained are useful in drying, milling or storing amaranth flour. PMID:2134142

Alvarado, J D; Toaza, E; Coloma, G

1990-09-01

106

OTEC gas desorption studies  

NASA Astrophysics Data System (ADS)

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

Chen, F. C.; Golshani, A.

1982-02-01

107

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

108

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

SciTech Connect

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

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

2011-01-01

109

Methylthiolate on Au(111): adsorption and desorption kinetics.  

PubMed

Low energy electron diffraction, Auger electron spectroscopy, X-ray photoelectron spectroscopy and line of sight mass spectrometry have been used to study the adsorption and desorption of dimethyldisulfide (DMDS) on Au(111). At 300 K adsorption is dissociative, forming a chemisorbed adlayer of methylthiolate with a 1/3 ML, (sq rt 3 x sq rt 3)R30 degrees, structure. At 100 K adsorption is molecular, with dissociation to form the 1/3 ML (sq rt 3 x sq rt 3)R30 degrees methylthiolate structure occurring at 138-160 K. A physisorbed DMDS layer, with a coverage of 1/6 ML of DMDS, forms on top of the (sq rt 3 x sq rt 3)R30 degrees chemisorbed MT surface for T < or = 180 K, with multilayers forming for T < or = 150 K. In temperature programmed desorption, multilayers of DMDS desorbed with zero order kinetics and an activation energy of 41 kJ mol(-1); the physisorbed layer desorbed with first order kinetics, exhibiting repulsive lateral interactions with an activation energy which varied from 63 kJ mol(-1) (theta = 0) to 51 kJ mol(-1) (theta = 1); the chemisorbed methylthiolate layer desorbed associatively as DMDS via the physisorbed layer, the activation energy for the reaction, 2 methylthiolate --> physisorbed DMDS, exhibiting repulsive lateral interactions with an activation energy which varied from 65 kJ mol(-1) (theta = 0) to 61 kJ mol(-1) (theta = 1). The physisorbed disulfide layer explains the pre-cursor state adsorption kinetics observed in sticking probability measurement, while its relatively facile formation provides a mechanism by which thiolate self-assembled monolayers can become mobile at room temperature. PMID:18292869

Roper, Mark G; Jones, Robert G

2008-03-01

110

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

111

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

SciTech Connect

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

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

2014-05-01

112

Effect of high-temperature on high-performance liquid chromatography column stability and performance under temperature-programmed conditions.  

PubMed

Six commercially available analytical (4.1 or 4.6 mm i.d.) columns were evaluated under temperature-programmed high-temperature liquid chromatography (HTLC) conditions to access their stability and performance at extreme temperatures. Seven components consisting of acidic, basic and neutral compounds were analyzed under temperature-programmed conditions and solvent gradient conditions using three different mobile phase compositions (acidic, basic and neutral). Each column was checked with a two-component test mix at various stages of the evaluation to look for signs of stationary phase collapse. Three zirconia based stationary phases studied exhibited column bleed under temperature-programmed conditions. The other three columns, a polydentate silica column, a polystyrene-divinylbenzene (PS-DVB) polymeric column, and a graphitic carbon column performed well with no evidence of stationary phase degradation. The R.S.D. for the retention times and efficiencies were less than 10% for most conditions, and not more than 15% during the course of the evaluation for each column. The polydentate silica stationary phase was temperature programmed to 100 degrees C, the PS-DVB stationary phase was temperature programmed up to 150 degrees C, and the graphitic carbon column was used with temperature programming up to 200 degrees C. Comparable peak capacities and similar retention behaviors were observed under solvent gradient and temperature-programmed conditions. Temperature programming with dynamic mobile phase preheating can replace solvent gradient analysis without a loss of peak capacity when used with 4.1 or 4.6 mm columns. PMID:15043277

Marin, Stephanie J; Jones, Brian A; Felix, W Dale; Clark, Jody

2004-03-19

113

HYDROGEN AND ITS DESORPTION IN RHIC.  

SciTech Connect

Hydrogen is the dominating gas specie in room temperature, ultrahigh vacuum systems of particle accelerators and storage rings, such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. Rapid pressure increase of a few decades in hydrogen and other residual gases was observed during RHIC's recent high intensity gold and proton runs. The type and magnitude of the pressure increase were analyzed and compared with vacuum conditioning, beam intensity, number of bunches and bunch spacing. Most of these pressure increases were found to be consistent with those induced by beam loss and/or electron stimulated desorption from electron multipacting.

HSEUH,H.C.

2002-11-11

114

Hysteretic Adsorption and Desorption of Hydrogen by Nanoporous MetalOrganic Frameworks  

Microsoft Academic Search

Adsorption and desorption of hydrogen from nanoporous materials, such as activated carbon, is usually fully reversible. We have prepared nanoporous metal-organic framework materials with flexible linkers in which the pore openings, as characterized in the static structures, appear to be too small to allow H2 to pass. We observe hysteresis in their adsorption and desorption kinetics above the supercritical temperature

Xuebo Zhao; Bo Xiao; Ashleigh J. Fletcher; K. Mark Thomas; Darren Bradshaw; Matthew J. Rosseinsky

2004-01-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

116

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 1764232 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

117

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

E-print Network

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

118

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

SciTech Connect

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

Not Available

2010-05-01

119

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

120

Characterization of nanoporous materials from adsorption and desorption isotherms  

Microsoft Academic Search

We present a consistent method for calculation of pore size distributions in nanoporous materials from adsorption and desorption isotherms, which form the hysteresis loop H1 by the IUPAC classification. The method is based on the nonlocal density functional theory (NLDFT) of capillary condensation hysteresis in cylindrical pores. It is implemented for the nitrogen and argon sorption at their boiling temperatures.

Peter I. Ravikovitch; Alexander V. Neimark

2001-01-01

121

Desorption of cesium from pyrolytic graphite basal surfaces with strongly non-equilibrium behaviour  

NASA Astrophysics Data System (ADS)

A field reversal kinetic study of the desorption of Cs + and Cs from a graphite basal surface (ZYB graphite) gives results that neither follow the Saha-Langmuir equation, nor fulfil the Schottky energy cycle. The non-equilibrium behaviour is due to a lowering of the rate of the ionic desorption, while the neutral desorption at low temperatures is described by normal rate parameters. At high temperatures, the neutral desorption rate constant is dominated by vertical diffusion into the bulk. The unexpected behaviour of the ion desorption is probably coupled to vertical diffusion too. It is suggested that the desorbing ions leave the surface from special positions on the surface, which are reached during the migration out from the bulk.

Mller, Kenneth; Holmlid, Leif

122

Desorption of cesium from pyrolytic graphite basal surfaces with strongly non-equilibrium behaviour  

NASA Astrophysics Data System (ADS)

A field reversal kinetic study of the desorption of Cs + and Cs from a graphite basal surface (ZYB graphite) gives results that neither follow the Saha-Langmuir equation, nor fulfil the Schottky energy cycle. The non-equilibrium behaviour is due to a lowering of the rate of the ionic desorption, while the neutral desorption at low temperatures is described by normal rate parameters. At high temperatures, the neutral desorption rate constant is dominated by vertical diffusion into the bulk. The unexpected behaviour of the ion desorption is probably coupled to vertical diffusion too. It is suggested that the desorbing ions leave the surface from special positions on the surface, which are reached during the migration out from the bulk.

Mller, Kenneth; Holmlid, Leif

1985-11-01

123

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

124

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

SciTech Connect

The kinetics of desorption both helium isotopes and molecules of hydrogen and deuterium from open-ended or ?-irradiated single-walled carbon nanotube bundles was investigated in temperature range of 10300?K. The gases desorption rates obey the Arrhenius law at high temperatures, deviate from it with temperature reduction and become constant at low temperatures. These results indicate the quantum nature of gas outflow from carbon nanotube bundles. We had deduced the crossover temperature below which the quantum corrections to the effective activation energy of desorption become significant. This temperature follows linear dependence against the inverse mass of gas molecule and is consistent with theoretical prediction.

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

2014-04-28

125

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

126

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

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

Ferrizz, Robert Matthew

2007-08-01

127

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

128

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

130

Adsorption-state-dependent subpicosecond photoinduced desorption dynamics  

SciTech Connect

Femtosecond laser excitation has been used to initiate desorption of molecular oxygen from the (111) surface of Pd and to study the adsorption-state dependence of the substrate-adsorbate coupling. The relative populations of the two chemical states, peroxo (O{sub 2}{sup 2-}) and superoxo (O{sub 2}{sup -}), were varied by changing the total coverage. Two-pulse correlation measurements exhibit a dominant 400 fs response and a slower 10 ps decay that are relatively independent of the initial O{sub 2} coverage. In contrast, the photodesorption yield and the nonlinearity of the fluence dependence show a systematic coverage dependence. The coverage-independent subpicosecond response indicates that the photoinduced desorption from the two states is driven primarily by the same electron-mediated mechanism, while the coverage dependence of the yield indicates that the desorption efficiency from the superoxo state is greater than that from the peroxo state. These results are discussed in the context of the electron-phonon two-temperature model with an empirical adsorbate-electron frictional coupling that depends on both the electronic temperature and the activation energy for desorption. With a coupling strength that decreases as the activation energy decreases, the trends with varying coverage, absorbed fluence, and time delay can all be reproduced. The model is consistent with a transition from a resonantly enhanced (diabatic) regime to an adiabatic regime as the system relaxes, accounting for the biexponential correlation behavior.

Szymanski, Paul; Harris, Alex L.; Camillone, Nicholas III [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

2007-06-07

131

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

SciTech Connect

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

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

2010-01-01

132

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

PubMed

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

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

2009-12-01

133

Internal friction and gas desorption of {C}/{C} composites  

NASA Astrophysics Data System (ADS)

{C}/{C} composites are the most promising candidates as high heat flux component materials, where temperature dependence of mechanical properties and gas desorption behavior at elevated temperature are important properties. At the beginning, the newly developed internal friction measurement apparatus, which enables the accurate measurement of dynamic elastic properties up to 1373 K along with the measurement of gas desorption behavior, was used. The materials studied were unidirectional (UD) {C}/{C} composites reinforced with mesophase pitch-based carbon fibers, which were heat treated at temperatures ranging from 1473 to 2773 K which produced a variety of graphitized microstructures. Two-dimensional (2D) {C}/{C} composites reinfored with flat woven fabrics of PAN type carbon fibers were also studied. These materials were heat treated at 1873 K. From the temperature spectrum of internal friction of 2D {C}/{C} composites, these internal friction peaks were detected and were related to gas desorption. Also the temperature dependence of Young's modulus of UD {C}/{C} composites, negative and positive dependence of Young's modulus were observed reflecting microstructure changes resulting from the heat treatments.

Serizawa, H.; Sato, S.; Kohyama, A.

1994-09-01

134

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

NASA Technical Reports Server (NTRS)

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

Eckel, Andrew J.; Glass, David E.

2005-01-01

135

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

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

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

SciTech Connect

Previous assessments of Colorado`s low-temperature geothermal resources were completed by the Colorado Geological Survey in 1920 and in the mid- to late-1970s. The purpose of the 1992--1993 low-temperature geothermal resource assessment is to update the earlier physical, geochemical, and utilization data and compile computerized databases of the location, chemistry, and general information of the low-temperature geothermal resources in Colorado. The main sources of the data included published data from the Colorado Geological Survey, the US Geological Survey WATSTOR database, and the files of the State Division of Water Resources. The staff of the Colorado Geological Survey in 1992 and 1993 visited most of the known geothermal sources that were recorded as having temperatures greater than 30{degrees}C. Physical measurements of the conductivity, pH, temperature, flow rate, and notes on the current geothermal source utilization were taken. Ten new geochemical analyses were completed on selected geothermal sites. The results of the compilation and field investigations are compiled into the four enclosed Quattro Pro 4 databases. For the purposes of this report a geothermal area is defined as a broad area, usually less than 3 sq mi in size, that may have several wells or springs. A geothermal site is an individual well or spring within a geothermal area. The 1992-1993 assessment reports that there are 93 geothermal areas in the Colorado, up from the 56 reported in 1978; there are 157 geothermal sites up from the 125 reported in 1978; and a total of 382 geochemical analyses are compiled, up from the 236 reported in 1978. Six geothermal areas are recommended for further investigation: Trimble Hot Springs, Orvis Hot Springs, an area southeast of Pagosa Springs, the eastern San Luis Valley, Rico and Dunton area, and Cottonwood Hot Springs.

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

1995-01-01

138

Characterization of coke on equilibrium fluid catalytic cracking catalysts by temperature-programmed oxidation  

Microsoft Academic Search

Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals is investigated using temperature-programmed oxidation (TPO) and temperature-programmed hydrogenation (TPH). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy gas oil (SIHGO) and ASTM standard-gasoil feed were deconvoluted into four peaks by fitting them into Gaussian-type functions. The four peaks are assigned to different

Oguz Bayraktar; Edwin L Kugler

2002-01-01

139

Electron-stimulated desorption of sodium atoms from germanium-coated tungsten  

NASA Astrophysics Data System (ADS)

The yield of sodium atoms and energy distribution upon electron-stimulated desorption from sodium layers adsorbed on tungsten coated with a germanium thin film are measured under variations in the electron energy, the sodium coverage, and the surface temperature by the time-of-flight method with the use of a surface ionization detector. It is revealed that the electron-stimulated desorption of sodium atoms occurs via three channels, namely, a channel involving ionization of adsorbed sodium; the most efficient channel, which is produced by the germanium ionization; and a channel associated with the formation of tungsten excitons, which brings about desorption of NaGe molecules.

Ageev, V. N.; Kuznetsov, Yu. A.

2007-05-01

140

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

141

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

NASA Astrophysics Data System (ADS)

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

Yougoubare, Y. Quentin; Pang, Su-Seng

2014-02-01

142

Low energy electron stimulated desorption from DNA films dosed with oxygen  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

143

Low energy electron stimulated desorption from DNA films dosed with oxygen.  

PubMed

Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O(2). The OH(-) desorption yields increase markedly with exposure to O(2) at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O(-), attributable to dissociative electron attachment to trapped O(2) molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O(2) shows that this surprising increase in OH(-) desorption, at elevated temperatures, arises from the reaction of O(2) 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, Lon

2012-06-21

144

Low energy electron stimulated desorption from DNA films dosed with oxygen  

PubMed Central

Desorption of anions stimulated by 118 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50250 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, Lon

2013-01-01

145

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

ERIC Educational Resources Information Center

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

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

2007-01-01

146

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

NASA Technical Reports Server (NTRS)

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

Cassenti, B. N.

1983-01-01

147

Pentachlorophenol adsorption and desorption characteristics of granular activated carbonI. Isotherms  

Microsoft Academic Search

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

Abdul H. Mollah; Campbell W. Robinson

1996-01-01

148

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

149

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

E-print Network

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

Gro, Andrea

150

Cesium Sorption\\/Desorption Experiments with IONSIV(R) IE911 in Radioactive Waste  

Microsoft Academic Search

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

2001-01-01

151

Temperature  

NSDL National Science Digital Library

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

Brieske, Joel A.

2002-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

1997-08-01

153

Molecular dynamics calculations of nuclear stimulated desorption  

Microsoft Academic Search

Molecular dynamics calculations of nuclear stimulated desorption are carried out for a palladium crystal containing radioactive palladium atoms. The total desorption probability from various sites are computed, as well as the angular distribution of the desorbing atoms. The implications of the results to different experimental scenarios are discussed.

E. Glikman; I. Kelson; N. V. Doan

1991-01-01

154

Molecular dynamics calculations of nuclear stimulated desorption  

SciTech Connect

Molecular dynamics calculations of nuclear stimulated desorption are carried out for a palladium crystal containing radioactive palladium atoms. The total desorption probability from various sites are computed, as well as the angular distribution of the desorbing atoms. The implications of the results to different experimental scenarios are discussed.

Glikman, E.; Kelson, I. (School of Physics and Astronomy, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel)); Doan, N.V. (Centre d'Etudes Nucleaires de Saclay, Cerem-Dtm-Srmp 91191 Gif-sur-Yvette Cedex (France))

1991-09-01

155

Flight summaries and temperature climatology at airliner cruise altitudes from GASP (Global Atmospheric Sampling Program) data  

NASA Technical Reports Server (NTRS)

Temperature data obtained by the Global Atmospheric Sampling Program (GASP) during the period March 1975 to July 1979 are compiled to form flight summaries of static air temperature and a geographic temperature climatology. The flight summaries include the height and location of the coldest observed temperature and the mean flight level, temperature and the standard deviation of temperature for each flight as well as for flight segments. These summaries are ordered by route and month. The temperature climatology was computed for all statistically independent temperture data for each flight. The grid used consists of 5 deg latitude, 30 deg longitude and 2000 feet vertical resolution from FL270 to FL430 for each month of the year. The number of statistically independent observations, their mean, standard deviation and the empirical 98, 50, 16, 2 and .3 probability percentiles are presented.

Nastrom, G. D.; Jasperson, W. H.

1983-01-01

156

Adsorption and thermal decomposition of C{sub 2}D{sub 5}I on the (110) and (111) planes of NiAl: A temperature programmed deposition and x-ray photoelectron spectroscopy study  

SciTech Connect

This study investigates the adsorption and the subsequent thermal decompoistion of d{sub 5}-iodoethane (C{sub 2}D{sub 5}I) on the (110) and (111) planes of NiAl using temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). Both I 3d{sub 5/2} and C 1s XPS data show that C{sub 2}D{sub 5}I adsorbs molecularly on both NiAl surfaces at 120 K. Upon heating the sample, the C{endash}I bond starts to cleave and the scission of this bond is complete on NiAl(110) and NiAl(111) by 150 and 300 K, respectively. It is suspected that this cleavage results in the formation of C{sub 2}D{sub 5(ad)} and I{sub (ad)}. TPD results show that the thermal decomposition of C{sub 2}D{sub 5(ad)} yields C{sub 2}D{sub 4} and D{sub 2} as the main products on both the surfaces. The main difference in the decomposition products of C{sub 2}D{sub 5(ad)} species on the two surfaces is that desorption of C{sub 2}D{sub 4} occurs on NiAl(111) at {approximately}315 K, {approximately}50 K higher than the corresponding value for NiAl(110). {copyright} {ital 1999 American Vacuum Society.}

Chaturvedi, S. [Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 (United States); Strongin, D.R. [Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)] [Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)

1999-05-01

157

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

158

Patterning graphene at the nanometer scale via hydrogen desorption.  

SciTech Connect

We have demonstrated the reversible and local modification of the electronic properties of graphene by hydrogen passivation and subsequent electron-stimulated hydrogen desorption with an scanning tunneling microscope tip. In addition to changing the morphology, we show that the hydrogen passivation is stable at room temperature and modifies the electronic properties of graphene, opening a gap in the local density of states. This insulating state is reversed by local desorption of the hydrogen, and the unaltered electronic properties of graphene are recovered. Using this mechanism, we have 'written' graphene patterns on nanometer length scales. For patterned regions that are roughly 20 nm or greater, the inherent electronic properties of graphene are completely recovered. Below 20 nm we observe dramatic variations in the electronic properties of the graphene as a function of pattern size. This reversible and local mechanism for modifying the electronic properties of graphene has far-reaching implications for nanoscale circuitry fabricated from this revolutionary material.

Sessi, P.; Guest, J. R.; Bode, M.; Guisinger, N.; Center for Nanoscale Materials; Politecnico di Milano

2009-12-01

159

Patterning graphene at the nanometer scale via hydrogen desorption.  

PubMed

We have demonstrated the reversible and local modification of the electronic properties of graphene by hydrogen passivation and subsequent electron-stimulated hydrogen desorption with an scanning tunneling microscope tip. In addition to changing the morphology, we show that the hydrogen passivation is stable at room temperature and modifies the electronic properties of graphene, opening a gap in the local density of states. This insulating state is reversed by local desorption of the hydrogen, and the unaltered electronic properties of graphene are recovered. Using this mechanism, we have "written" graphene patterns on nanometer length scales. For patterned regions that are roughly 20 nm or greater, the inherent electronic properties of graphene are completely recovered. Below 20 nm we observe dramatic variations in the electronic properties of the graphene as a function of pattern size. This reversible and local mechanism for modifying the electronic properties of graphene has far-reaching implications for nanoscale circuitry fabricated from this revolutionary material. PMID:19883050

Sessi, Paolo; Guest, Jeffrey R; Bode, Matthias; Guisinger, Nathan P

2009-12-01

160

Patterning graphene at the nanometer scale via hydrogen desorption  

NASA Astrophysics Data System (ADS)

We have demonstrated the reversible and local modification of the electronic properties of graphene by hydrogen passivation and subsequent electron-stimulated hydrogen desorption with an STM tip. In addition to changing the morphology, we show that the hydrogen passivation is stable at room temperature and modifies the electronic properties of graphene, opening a gap in the LDOS. This insulating state is reversed by local desorption of the hydrogen, and the unaltered electronic properties of graphene are recovered. Using this mechanism, we have ``written'' graphene patterns on nanometer length scales. This reversible and local mechanism for modifying the electronic properties of graphene has far-reaching implications for nanoscale circuitry fabricated from this revolutionary material.

Sessi, Paolo; Guest, Jeffrey; Bode, Matthias; Guisinger, Nathan

2010-03-01

161

Electron- and photon-stimulated desorption of atomic hydrogen from radiation-modified alkali halide surfaces  

NASA Astrophysics Data System (ADS)

The desorption yields of excited hydrogen atoms from the surfaces of KCl, KBr, NaCl, NaF, and LiF have been measured as a function of incident photon and electron energy and flux, time of irradiation, dosing pressure of H2 and sample temperature. As these surfaces are exposed to H2 gas during electron or photon bombardment, the fluorescence from excited hydrogen atoms ejected from the surface is monitored. The desorption yields are found to be contingent upon surface damage induced by the incident particle radiation, leading to dissociative adsorption at surface sites containing an excess of alkali metal. A desorption mechanism is presented in which incident electrons or photons induce a valence excitation to a neutral, antibonding state of the surface alkali hydride molecule complex, leading to the desorption of hydrogen atoms possessing several eV of kinetic energy.

Hudson, L. T.; Tolk, N. H.; Bao, C.; Nordlander, P.; Russell, D. P.; Xu, J.

2000-10-01

162

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

163

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

Microsoft Academic Search

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

Xiaofeng Lin; Tangbo Liu; Deguang Cao; Qingbao Huang

2009-01-01

164

Temperature-programmed oxidation of coked noble metal catalysts after autothermal reforming of n-hexadecane  

Microsoft Academic Search

Autothermal reforming (ATR) of n-hexadecane was carried out on zirconia-supported mono- and bimetallic noble metal (Rh, Pt) catalysts at 600, 700, and 800C. After ATR, the reactivity of coke deposits (2.89.9wt%) on the catalysts was investigated by temperature-programmed oxidation (TPO). Analysis of the results obtained from ATR and TPO experiments at various temperatures and on the different catalysts gave information

E. I. Kauppi; R. K. Kaila; J. A. Linnekoski; A. O. I. Krause; M. K. Veringa Niemel

2010-01-01

165

Dynamics of desorption with lateral diffusion  

NASA Astrophysics Data System (ADS)

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

Juwono, Tjipto; Rikvold, Per Arne

2013-09-01

166

Dynamics of desorption with lateral diffusion.  

PubMed

The dynamics of desorption from a submonolayer of adsorbed atoms or ions are significantly influenced by the absence or presence of lateral diffusion of the adsorbed particles. When diffusion is present, the adsorbate configuration is simultaneously changed by two distinct processes, proceeding in parallel: adsorption/desorption, which changes the total adsorbate coverage, and lateral diffusion, which is coverage conserving. Inspired by experimental results, we here study the effects of these competing processes by kinetic Monte Carlo simulations of a simple lattice-gas model. In order to untangle the various effects, we perform large-scale simulations, in which we monitor coverage, correlation length, and cluster-size distributions, as well as the behavior of representative individual clusters, during desorption. For each initial adsorbate configuration, we perform multiple, independent simulations, without and with diffusion, respectively. We find that, compared to desorption without diffusion, the coverage-conserving diffusion process produces two competing effects: a retardation of the desorption rate, which is associated with a coarsening of the adsorbate configuration, and an acceleration due to desorption of monomers "evaporated" from the cluster perimeters. The balance between these two effects is governed by the structure of the adsorbate layer at the beginning of the desorption process. Deceleration and coarsening are predominant for configurations dominated by monomers and small clusters, while acceleration is predominant for configurations dominated by large clusters. PMID:24089794

Juwono, Tjipto; Rikvold, Per Arne

2013-09-28

167

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

168

Surface topography dependent desorption of alkali halides  

PubMed

Electron-stimulated desorption of the (100)KBr surface has been investigated in vacuum with noncontact atomic force microscopy and mass spectroscopy. It has been found that both desorption components (K and Br) show oscillatory dependence on the electron dose with the oscillation amplitude decaying gradually. These results correspond with periodically varying, as a result of a layer-by-layer desorption, surface topography. It is proposed that the surface terrace edges act as traps for excited F centers diffusing in the crystal. The oscillating density of terrace edges varies surface recombination/reflection rates for the F centers and modulates the balance between surface and bulk deexcitation of the crystal. PMID:10978122

Such; Kolodziej; Czuba; Piatkowski; Struski; Krok; Szymonski

2000-09-18

169

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

170

Thermal Desorption Analysis of Hydrogen in High Strength Martensitic Steels  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

171

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

172

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

SciTech Connect

This paper presents an overview of the high-temperature electrolysis research and development program at the Idaho National Laboratory, with selected observations of electrolysis cell degradation at the single-cell, small stack and large facility scales. The objective of the INL program is to address the technical and scale-up issues associated with the implementation of solid-oxide electrolysis cell technology for hydrogen production from steam. In the envisioned application, high-temperature electrolysis would be coupled to an advanced nuclear reactor for efficient large-scale non-fossil non-greenhouse-gas hydrogen production. The program supports a broad range of activities including small bench-scale experiments, larger scale technology demonstrations, detailed computational fluid dynamic modeling, and system modeling. A summary of the current status of these activities and future plans will be provided, with a focus on the problem of cell and stack degradation.

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

2009-06-01

173

Computer Program for Calculation of a Gas Temperature Profile by Infrared Emission: Absorption Spectroscopy  

NASA Technical Reports Server (NTRS)

A computer program to calculate the temperature profile of a flame or hot gas was presented in detail. Emphasis was on profiles found in jet engine or rocket engine exhaust streams containing H2O or CO2 radiating gases. The temperature profile was assumed axisymmetric with an assumed functional form controlled by two variable parameters. The parameters were calculated using measurements of gas radiation at two wavelengths in the infrared. The program also gave some information on the pressure profile. A method of selection of wavelengths was given that is likely to lead to an accurate determination of the parameters. The program is written in FORTRAN IV language and runs in less than 60 seconds on a Univac 1100 computer.

Buchele, D. R.

1977-01-01

174

Laboratory study of sticking and desorption of H2 and its significance in the chemical evolution of dense interstellar medium  

NASA Astrophysics Data System (ADS)

The temperature-programmed desorption spectra of H2 is recorded under ultrahigh vacuum conditions on an olivine substrate with more than 90 per cent forsterite content for different coverage and temperatures. Then, using an empirical kinetic model, binding energy of H2 on the substrate is found to be 480 10 K (41.36 0.86 meV). Lower limit of sticking coefficient is estimated by comparing gas load at room temperature and at low temperature, which varies between 0.82 and 0.25 for temperatures between 7 and 14 K. Using a gas-grain chemical network, it is found out that a steady state is reached around after 50 yr at 10 K and both the steady-state abundance and time required to attend steady state is a strong function of temperature. Then, this model is used to check the effect of sticking of H2 on the grain surface chemistry. It is found that for H2O, CH4, NH3 and HCN, abundance due to reaction pathways involving H2 is within 1 per cent, when compared with the abundance achieved considering most dominant pathways. Thus, neglecting sticking of H2 will not change overall abundance of these molecules. For carbon chain molecules, it was found that the reaction pathways with H2 may be important and could contribute significantly to account for the observed abundances. Since, sticking of H2 is temperature sensitive, increase in temperature will reduce the effect of these reactions.

Acharyya, K.

2014-09-01

175

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

176

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

SciTech Connect

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

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

2014-05-14

177

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

PubMed

Electron induced reactions in molecular nanofilms of chlorodifluoroacetic acid (CClF(2)COOH) are studied by electron stimulated desorption (ESD) of fragment anions and temperature programed thermal desorption spectroscopy (TDS). The fragment anions O(-), F(-), OH(-), and Cl(-) are formed from broad resonance features in the energy range of 4-14 eV and assigned to dissociative electron attachment (DEA) of molecules or dimers at or near the surface of the film, followed by desorption. The strong low energy DEA resonances (0-2 eV) observed in a previous gas phase study [J. Kopyra et al., Int. J. Mass. Spectrom. 285, 131 (2009)] are completely suppressed in ESD. Electron irradiation at energies above 10 eV results in the formation of CO(2), as revealed by TDS. The extended irradiation of a 3 ML film (25 nA, 240 min) results in a nearly completely transformation of the initial compound in favor of CO(2) and other by-products. PMID:21090864

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

2010-11-21

178

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

PubMed

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

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

2013-05-01

179

Adsorption and desorption mechanisms for allylamine, propylamine, propylchloride, and propylene on the Si(100)-2x1 surface  

NASA Astrophysics Data System (ADS)

The mechanisms for adsorption and desorption of allylamine, propylamine, propylchloride, and propylene on the Si(100)-2x1 surface has been investigated experimentally using thermal desorption spectroscopy (TDS) and computationally using density functional theory (DFT) calculations. TDS was carried out to track down possible desorption products and their desorption temperatures and DFT calculations were done to help elucidate the experimental results, and to more fully probe mechanistic pathways consistent with the TDS results. All of these molecules are three carbon chain moieties with differing terminal functional groups and were chosen to self-consistently probe amine and alkene functional group chemistry on this surface. Results from the adsorption of propylene and allylamine were mostly consistent with previous studies on adsorption of these molecules, with the main difference being the observation of a prominent m/z = 17 desorption product in the case of TDS after allylamine adsorption. TDS after propylamine and allylamine adsorption gave rise to a prominent propylene (m/z = 42) desorption channel. The TDS results showed that propylene and halo-alkanes such as chloro-propane also display a propylene desorption channel, but it appears at a lower surface temperature than for the amines. This is an indication that the amine adsorption and decomposition mechanisms is different than halo-alkane or alkene reaction on the Si(100)-2x1 surface, in that it does not involve any silicon-carbon bond forming reactions initially. This is consistent with the computational results as well.

Adhikari, Lekh; Casey, Sean

2011-11-01

180

Further development of the dynamic gas temperature measurement system. Volume 2: Computer program user's manual  

NASA Technical Reports Server (NTRS)

The Dynamic Gas Temperature Measurement System compensation software accepts digitized data from two different diameter thermocouples and computes a compensated frequency response spectrum for one of the thermocouples. Detailed discussions of the physical system, analytical model, and computer software are presented in this volume and in Volume 1 of this report under Task 3. Computer program software restrictions and test cases are also presented. Compensated and uncompensated data may be presented in either the time or frequency domain. Time domain data are presented as instantaneous temperature vs time. Frequency domain data may be presented in several forms such as power spectral density vs frequency.

Stocks, Dana R.

1986-01-01

181

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

NASA Technical Reports Server (NTRS)

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

Purpura, P. T.

1983-01-01

182

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

183

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

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

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

Microsoft Academic Search

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

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

2010-01-01

186

Characterizations of alumina-supported gold with temperature-programmed reduction  

Microsoft Academic Search

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

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

1998-01-01

187

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

SciTech Connect

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

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

1980-11-30

188

Program accomplishments and future prospects for low-temperature geothermal resource assessment in New Mexico  

SciTech Connect

An important component of the State-coupled program has been basic studies in specific regions of New Mexico, including areas adjacent to the cities of Albuquerque, Las Cruces, Socorro, and Truth or Consequences. Considerable geological, hydrological, electrical resistivity, gravity, magnetic, seismic, water analysis, and subsurface temperature data have been compiled and analyzed for these locations. During the four-year research program, a total of 25 tasks have been undertaken. Eleven of these tasks were focused toward collecting and compiling statewide data, six were regional studies covering more than one county, and eight were research projects directed primarily toward data collection near specific cities or known resource areas. Two of these latter studies contributed significantly to the confirmation of the Las Alturas geothermal anomaly east of Las Cruces. A brief summary of the program accomplishments by task is presented. The resource assessment programs in New Mexico have been very successful in (1) delineating low-temperature geothermal resources throughout New Mexico on statewide, regional, and area-specific scales; (2) developing a strong community of in-state geothermal energy research and development professionals and practitioners; and (3) elevating the level of awareness of geothermal energy potential among commerce, industry, and the general public. Future prospects for the state are presented.

Icerman, L.; Ruscetta, C.A. (ed.)

1982-07-01

189

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

190

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

SciTech Connect

This paper provides a status update on the high-temperature electrolysis (HTE) research and development program at the Idaho National Laboratory (INL), with an overview of recent large-scale system modeling results and the status of the experimental program. System analysis results have been obtained using the commercial code UniSim, augmented with a custom high-temperature electrolyzer module. The process flow diagrams for the system simulations include an advanced nuclear reactor as a source of high-temperature process heat, a power cycle and a coupled steam electrolysis loop. Several reactor types and power cycles have been considered, over a range of reactor coolant outlet temperatures. In terms of experimental research, the INL has recently completed an Integrated Laboratory Scale (ILS) HTE test at the 15 kW level. The initial hydrogen production rate for the ILS test was in excess of 5000 liters per hour. Details of the ILS design and operation will be presented. Current small-scale experimental research is focused on improving the degradation characteristics of the electrolysis cells and stacks. Small-scale testing ranges from single cells to multiple-cell stacks. The INL is currently in the process of testing several state-of-the-art anode-supported cells and is working to broaden its relationship with industry in order to improve the long-term performance of the cells.

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

2009-04-01

191

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 350C 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?m100?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

192

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

SciTech Connect

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

Walker, D.D.

2001-02-13

193

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

EPA Science Inventory

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

194

Diffusion of electronic defects in calcia-stabilized zirconia from a desorption rate study  

Microsoft Academic Search

This paper reports on rates of desorption of oxygen from samples of calcis-stabilized zirconia (CSZ) measured as a function of oxygen saturation pressure, of temperature, and of the impurity content of CSZ. The results have been interpreted to determine the diffusion coefficient, {ital D}, for electronic defects in CSZ. {ital D} was independent of the oxygen saturation pressure from 0.5

Shixue Dou; C. R. Masson; P. D. Pacey

1990-01-01

195

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

EPA Science Inventory

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

196

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

197

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, ...

198

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...

199

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

200

A microsystems enabled field desorption source.  

SciTech Connect

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

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

2010-07-01

201

MEASUREMENT OF VOCS DESORBED FROM BUILDING MATERIALS--A HIGH TEMPERATURE DYNAMIC CHAMBER METHOD  

EPA Science Inventory

Mass balance is a commonly used approach for characterizing the source and sink behavior of building materials. Because the traditional sink test methods evaluate the adsorption and desorption of volatile organic compounds (VOC) at ambient temperatures, the desorption process is...

202

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

203

Abnormal InGaN growth behavior in indium-desorption regime in metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

InGaN strained bulk layers were grown by low-pressure metalorganic chemical vapor deposition on c-plane GaN/sapphire templates. Two growth regimes, mass-transport limited regime and indium desorption regime, were examined for InGaN growth. In the indium desorption regime, more indium source must be fed to keep a constant indium content. In the indium desorption regime, we found an abnormally enhanced GaN growth rate, which was proved to be related to the indium desorption and dependent on the growth temperature and the indium source flow. Due to the enhanced growth rate, the optical quality of In0.16Ga0.84N layers degraded significantly.

Zhou, Kun; Ikeda, Masao; Liu, Jianping; Zhang, Shuming; Li, Zengcheng; Feng, Meixin; Tian, Aiqin; Wen, Pengyan; Li, Deyao; Zhang, Liqun; Yang, Hui

2015-01-01

204

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

SciTech Connect

The Department of Energys 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

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 (38.1C) and early-low late-high (LH). This second profile had low (36.9C) eggshell temperature for the first 3 d, and standard temperature until the last 3 d when eggs were subjected to elevated (38.9C) 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-Rondn, E O; Wineland, M J; Wilson, J; Montiel, E

2014-08-01

206

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

PubMed

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

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

2014-09-16

207

On factors controlling activity of submonolayer bimetallic catalysts: Nitrogen desorption  

SciTech Connect

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

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

2014-01-07

208

On factors controlling activity of submonolayer bimetallic catalysts: Nitrogen desorption  

NASA Astrophysics Data System (ADS)

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

Guo, Wei; Vlachos, Dionisios G.

2014-01-01

209

Observation of thermal desorption and MBE growth rate using laser light scattering  

Microsoft Academic Search

We applied Laser Light Scattering (LLS) to study oxide surface desorption on InSb substrates, and the subsequent growth of CdTe layers by molecular beam epitaxy. LLS measurements allowed us to determine the critical temperature before surface degradation of InSb, which is not clearly noticed by Reflection High Energy Electron Diffraction (RHEED). Surface defects appeared on substrates where this temperature was

J. Huerta-Ruelas; M Lpez-Lpez; O Zelaya-Angel

2000-01-01

210

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

PubMed

In this study, a high-performance TixZrySizO flash memory is demonstrated using a sol-gel spin-coating method and formed under a low annealing temperature. The high-efficiency charge storage layer is formed by depositing a well-mixed solution of titanium tetrachloride, silicon tetrachloride, and zirconium tetrachloride, followed by 60 s of annealing at 600C. 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 85C) and 10% (at 125C) charge loss. The barrier height of the TixZrySizO film is demonstrated to be 1.15 eV for hole trapping, through the extraction of the Poole-Frenkel current. The excellent performance of the memory is attributed to high trapping sites of the low-temperature-annealed, high-? sol-gel film. PMID:23899050

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

2013-01-01

211

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

NASA Astrophysics Data System (ADS)

In this study, a high-performance Ti x Zr y Si z O flash memory is demonstrated using a sol-gel spin-coating method and formed under a low annealing temperature. The high-efficiency charge storage layer is formed by depositing a well-mixed solution of titanium tetrachloride, silicon tetrachloride, and zirconium tetrachloride, followed by 60 s of annealing at 600C. 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 85C) and 10% (at 125C) charge loss. The barrier height of the Ti x Zr y Si z O film is demonstrated to be 1.15 eV for hole trapping, through the extraction of the Poole-Frenkel current. The excellent performance of the memory is attributed to high trapping sites of the low-temperature-annealed, high- ? sol-gel film.

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

2013-07-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

213

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

214

Dependence of surface oxidation on hydrogen absorption and desorption behaviors of Ti-6Al-4V alloy  

NASA Astrophysics Data System (ADS)

The hydrogen absorption and desorption behaviors of surface oxidized and degassed Ti-6Al-4V alloys under a condition of hydrogen pressure near to the pressure during glow discharge conditioning in reactor were evaluated by thermal desorption spectroscopy (TDS). The equilibrium hydrogen concentration, Ceq, of degassed Ti-6Al-4V alloy decreased with increase of temperature. The Ceq was about half of that of pure Ti in the temperature region of 673-873 K. The desorption peak of degassed Ti-6Al-4V alloy appeared at the temperature of 790 K. The peak temperature was almost the same even when the absorption amount changed. The absorption amount, Cab, of surface oxidized alloy largely decreased with the increase of atomic ratio (O/Ti) on the top surface and the thickness of the oxide layer when adsorption time was 1 h. In addition, the desorption peak shifted to a higher temperature region with the increase of O/Ti ratio. In the surface oxidized Ti-6Al-4V alloy with an oxide layer of about 10 nm, the Cab was two orders of magnitude smaller than that of the degassed sample when the absorption temperature and time were kept at lower than 650 K and 1 h, respectively. However, the Cab of surface oxidized alloy became comparable with that of degassed sample when the absorption temperature was higher than 800 K because the oxide layer disappeared in the higher temperature region.

Hirohata, Y.; Nakamura, T.; Aihara, Y.; Hino, T.

215

Thermal desorption study of physical forces at the PTFE surface  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

216

Thermal desorption study of physical forces at the PTFE surface  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

217

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

218

Laser-induced thermal desorption mass spectrometry of functionalized silicon surfaces  

NASA Astrophysics Data System (ADS)

Functionalization of materials and laser patterning of chemisorbed layers play an increasing role in tailoring and structuring surface properties on the nanoscale. An attractive method of investigating organic functionalizations is laser-induced thermal desorption (LITD). The analysis of well-defined H- and D-terminated Si(1 1 1)-(1 1):H(D) surfaces was used to quantify the LITD technique. Moreover, oxidized silicon surfaces were functionalized with trimethylsilyl (TMS) and (3,3,3-trifluoropropyl)-dimethylsilyl (TFP) hydrophobic end groups. The samples were irradiated normal to the surface with focused XeCl laser pulses. The desorbed species were monitored at an oblique angle and their time-of-flight (TOF) distributions were measured with a quadrupole mass analyzer. The TOF temperatures of silicon were calibrated for different laser pulse energies by desorption of H 2 and D 2. In the LITD experiments, the desorption of trimethylsilanol groups was observed for TMS terminations, indicating that essentially the whole molecule desorbs from the surface. The TOF data could be fitted to Maxwellian distributions, providing the desorption yield of the emitted species, their mass, and temperature. On the other hand, several characteristic fragments were found for the TFP-terminated surface. The TOF distributions indicate that the fragments detected with the analyzer derived from different desorbed species.

Lingenfelser, Dominic; Hess, Peter

2007-07-01

219

Electron-stimulated defect formation in single-walled carbon nanotubes studied by hydrogen thermal desorption spectroscopy  

NASA Astrophysics Data System (ADS)

Defects in single-walled carbon nanotubes introduced by low-energy electron irradiation at 8 K were sensitively detected by cryogenic thermal desorption of hydrogen molecules H 2 in the temperature range of 10-40 K. The thermal desorption spectrum was found to change significantly with sample annealing at temperatures as low as 40-70 K. Experimental results suggest that the H 2 physisorption sites responsible for the 'defect' peak at 28 K are interstitial channel space between nanotubes closely packed in bundles which becomes more easily accessible on damage. It is also suggested that the disordering provides groove sites for H 2 physisorption with smaller binding energy causing the damage-induced spectral component around 16 K, slightly lower than the desorption peak at 20 K that is observed in undamaged samples. The spectral change at 40-70 K could be interpreted by migration of adatoms at the low temperatures.

Arima, Satoshi; Lee, Sangkil; Mera, Yutaka; Ogura, Shohei; Fukutani, Katsuyuki; Sato, Yoshinori; Tohji, Kazuyuki; Maeda, Koji

2009-11-01

220

Electron stimulated desorption of H 3O + from 316L stainless steel  

NASA Astrophysics Data System (ADS)

Surface ions generated by electron stimulated desorption from mass spectrometer ion source grids are frequently observed, but often misidentified. For example, in the case of mass 19, the source is often assumed to be surface fluorine, but since the metal oxide on grid surfaces has been shown to form water and hydroxides, a more compelling case can be made for the formation of hydronium. Further, fluorine is strongly electronegative, so it is rarely generated as a positive ion. A commonly used metal for ion source grids is 316L stainless steel. Thermal vacuum processing by bakeout or radiation heating from the filament typically alters the surface composition to predominantly Cr 2O 3. X-ray photoelectron spectral shoulders on the O 1s and Cr 2p 3/2 peaks can be attributed to adsorbed water and hydroxides, the intensity of which can be substantially increased by hydrogen dosing. On the other hand, the sub-peak intensities are substantially reduced by heating and/or by electron bombardment. Electron bombardment diode measurements show an initial work function increase corresponding to predominant hydrogen desorption (H 2) and a subsequent work function decrease corresponding to predominant oxygen desorption (CO). The fraction of hydroxide concentration on the surface was determined from X-ray photoelectron spectroscopy and from the deconvolution of temperature desorption spectra. Electron stimulated desorption yields from the surface show unambiguous H 3O + peaks that can be significantly increased by hydrogen dosing. Time of flight secondary ion mass spectrometry sputter yields show small signals of H 3O +, as well as its constituents (H +, O + and OH +) and a small amount of fluorine as F -, but no F + or F + complexes (HF +, etc.). An electron stimulated desorption cross-section of ?+ 1.4 10 -20 cm 2 was determined for H 3O + from 316L stainless steel for hydrogen residing in surface chromium hydroxide.

Cole, C. R.; Outlaw, R. A.; Champion, R. L.; Holloway, B. C.; Kelly, M. A.

2007-02-01

221

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

222

Photo-desorption from copper alloys  

Microsoft Academic Search

In support of PEP-II, a high luminosity B factory, photo-desorption of Cu alloys were measured to demonstrate suitability for ultra-high performance under high radiation loads. Results show that [eta][sub eff][le]2[times]10[sup [minus]6] mol\\/photon is a practical design value for Cu vacuum chambers. Commissioning times to attain this value in B factories can be expected to be <50 h. Pre-cleaning with Ar

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

1992-01-01

223

Photo-desorption from copper alloys  

Microsoft Academic Search

In support of PEP-II, a high luminosity B factory, photo-desorption of Cu alloys were measured to demonstrate suitability for ultra-high performance under high radiation loads. Results show that η{sub eff}210⁻⁶ mol\\/photon is a practical design value for Cu vacuum chambers. Commissioning times to attain this value in B factories can be expected to be <50 h. Pre-cleaning with Ar glow

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

1992-01-01

224

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

PubMed

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

Yang, Wenli; Holmn, Britt A

2007-06-01

225

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

226

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

227

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

228

High-Temperature-Turbine-Technology Program. Phase II. Technology test and support studies. Final report  

SciTech Connect

The Phase II program summarized in this report involved the development of the key high temperature turbine subsystem components toward a goal of technology readiness. Transpiration air-cooling (TAC) for the turbine blades and vanes was selected for this program not only because it is the most effective air cooling concept known but also because it has the potential to be highly resistant to the erosion, corrosion and deposition that could occur from contaminants expected to be present in coal-derived fuels. Demonstration of the capability of transpiration air cooling to perform satisfactorily up to 3000/sup 0/F and to resist the attack of solid and liquid particulate matter and high levels of alkali metals was accomplished using two full scale gas turbine engines and associated combustor/stator cascade rigs. The first of these engines was a low pressure turbine operating with turbine inlet pressure of 3 atm. The second engine, the Turbine Spool Technology Rig, was designed to duplicate in full scale the high pressure spool turbine of a 17:1 pressure ratio, 2-spool gas turbine unit of 70 MW electric output. The demonstration of turbine performance and durability was reinforced by development of two combustor designs - one using simulated LBG fuel and the other using coal-liquid SRC-II fuel. Test evaluations at up to 6 atm and 3000/sup 0/F showed the capability of burning these relatively low grade fuels with high efficiency and low emissions of environmental pollutants. As a concluding effort, the information obtained in the various test programs and analytical studies was applied to update the baseload plant designs for low btu gas and coal-liquid.

Not Available

1983-02-01

229

Low-temperature alteration of mesozoic oceanic crust, Ocean Drilling Program Leg 185  

NASA Astrophysics Data System (ADS)

Basalts drilled from the Mesozoic crust at Ocean Drilling Program (ODP) Sites 801 and 1149 during Leg 185 have been affected by a succession of submarine, variably oxidative alteration processes by cold seawater. The low-temperature alteration resulted in various combinations of secondary minerals both as replacements of igneous phases, and as void and crack fillings. Mg-smectite, calcite, celadonite and Fe-oxyhydroxide are the dominant secondary minerals. Quartz, chalcedony and phillipsite are always very minor phases that fill open spaces. The rocks generally exhibit concentric haloes, 0.5 to 1 cm in thickness, around gray inner cores and usually adjacent to exposed surfaces. Color zonations result from the abundance of various secondary mineral assemblages present in each zone. The green rocks are dominated by celadonitic phyllosilicates, whereas the dusky red haloes are characterized by abundant iddingsite and Fe-oxyhydroxides replacing the fine clinopyroxene. Finally Mg-smectite calcite, are the most common secondary phases in the inner gray cores. The most unusual effects of the low-temperature alteration of the study rocks are the pervasive, pale green to gray green color and the relatively abundant dusky red haloes surrounding inner reddish gray cores. Alteration of Mesozoic crust cored during Leg 185 is comparable with low-temperature alteration of 310 m thick uppermost volcanic section of the 5.9 My old crust of Hole 504B. Except the renewed precipitation of calcite in veins, the aging of oceanic crust does not depend on time probably because it occurs during the first few millions of years after the accretion, and ceases when the crust is sealed off.

Talbi, El Hassan; Honnorez, Jos

2003-05-01

230

Measurements and analysis of water adsorption and desorption  

SciTech Connect

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

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

1996-02-01

231

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

PubMed

High operating temperature and slow kinetics retard the practical applications of the Li-Mg-N-H system for hydrogen storage. To alleviate these problems, a first attempt was carried out by synthesizing Li(2)MgN(2)H(2) through sintering a mixture of Mg(NH(2))(2)-2LiNH(2) and investigating its size-dependent hydrogen storage performance. A dramatically enhanced kinetics for hydrogen absorption/desorption was achieved with a reduction in the particle size. For the dehydrogenation reaction, a three-dimensional diffusion-controlled kinetic mechanism was identified for the first time by analyzing isothermal hydrogen desorption curves with a linear plot method. The experimental improvement and mechanistic understanding on the dehydrogenation kinetics of the Li-Mg-N-H system shed light on how to further decrease the operating temperature and enhance the hydrogen absorption/desorption rate of the amide/hydride combined materials. PMID:19191702

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

2009-02-11

232

Highly efficient electron stimulated desorption of O+ from gadolinia-doped ceria surfaces.  

PubMed

Highly efficient electron stimulated desorption of O+ from gadolinia-doped ceria (GDC) surfaces annealed at 850 K in ultrahigh vacuum is observed and investigated. O+ desorption has a major threshold of approximately 40 eV and an intrinsic kinetic energy of approximately 5.6 eV. Since the threshold energy is close to Ce 5s and Gd 5s core levels, Auger decay of core holes is likely associated with O+ desorption from sites related to oxygen vacancies. The interactions of water and molecular oxygen with GDC surfaces result in a decrease in O+ desorption, suggesting that water and oxygen molecules adsorb mainly to oxygen vacancies. The dependence of O+ kinetic energies on the incident electron energy and temperature reveals surface charging as a result of electron trapping, hole trapping, and electron-hole recombination. The activation energy for surface charge dissipation is found to be 0.43 eV, close to the activation energy for ionic conduction (0.47 to 0.6 eV) in the same material. PMID:16771326

Chen, Haiyan; Aleksandrov, Alex; Zha, Shaowu; Liu, Meilin; Orlando, Thomas M

2006-06-01

233

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

NASA Technical Reports Server (NTRS)

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

Sollit, Luke S.; Beegle, Luther W.

2008-01-01

234

Adsorption and desorption of selected VOCs in dust collected on air filters  

NASA Astrophysics Data System (ADS)

Adsorption and desorption properties of the dust accumulated on air filters were examined by using a small-scale test apparatus with model compounds. The dust samples were loaded with the model compounds either by adsorption from a constant concentration in air flow or by direct injection into the dust. Desorption was measured at three different relative humidities of air (4-5%, 40-50%, 70-80%). Results indicated that constant relative humidity (RH) of air did not affect the rate of desorption in the test conditions. However, an increase in humidity substantially increased desorption of the model compounds. Similar results were obtained when experiments were conducted using dirty filters without added model compounds. In addition, emission products from clean and dusty filter materials were analyzed at two temperatures (50C and 100C) by using an automatic thermodesorption device. The main compounds released were carboxylic acids, aldehydes and terpenes. The emission profiles were similar for the pre-filters and main filters, but the emissions were higher from pre-filters than from the main filters. This result is consistent with the earlier findings of higher odor emissions from pre-filters.

Hyttinen, Marko; Pasanen, Pertti; Kalliokoski, Pentti

235

Characterization of alkanethiol self-assembled monolayers on gold by thermal desorption spectroscopy.  

PubMed

SAM formation of undecanethiol (UDT) and mercaptoundecanoic acid (11-MUA) on Au(111) and on gold foils, using wet chemical preparation methods as well as physical vapor deposition (PVD) in UHV, has been studied by means of thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES). The main aim of this study was to explore the possible application of TDS to characterize the quality of a SAM and to determine its thermal stability. The influence of various parameters, like substrate pretreatment, film formation method, and type of the functional end group, has been studied in detail. Three different temperature regimes can be identified in TDS, which yields specific information about the organic layer: Desorption of disulfides around 400 K can be shown to result from standing molecules in a well-defined SAM. Desorption of intact molecules and of molecules with split-off sulfur is observed around 500 K, resulting from lying molecules. Finally, desorption of an appreciable amount of gold-containing molecules is observed around 700 K. This is more pronounced for 11-MUA than for UDT, and in addition more pronounced for solution-based SAMs than for PVD prepared SAMs. These results emphasize the important role of gold adatoms in SAM formation, as recently discussed in the literature. PMID:20345109

Stettner, Johanna; Winkler, Adolf

2010-06-15

236

Desorption Studies of DDGS under Varying CDS and Temperature Levels  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

237

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

238

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

PubMed Central

We study the physisorption of atomic hydrogen on graphitic surfaces with four different quantum mechanical methods: perturbation and effective Hamiltonian theories, close coupling wavepacket, and reduced density matrix propagation methods. Corrugation is included in the modeling of the surface. Sticking is a fast process which is well described by all methods. Sticking probabilities are of the order of a few percent in the collision energy range 025 meV, but are enhanced for collision energies close to those of diffraction resonances. Sticking also increases with surface temperature. Desorption is a slow process which involves multiphonon processes. We show, however, how to correct the close coupling wavepacket method to account for such phenomena and obtain correct time constants for initial state decay. Desorption time constants are in the range of 2050 ps for a surface temperature of 300 K. PMID:21428654

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

2011-01-01

239

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

Microsoft Academic Search

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

S. Yoshizawa; A. Karagiri; K. Watanabe

1979-01-01

240

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

NASA Technical Reports Server (NTRS)

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

Walker, K. P.

1981-01-01

241

Remediation of elemental mercury using in situ thermal desorption (ISTD).  

PubMed

In situ thermal desorption (ISTD) is a soil heating method that simultaneously applies heat and vacuum to the subsurface at temperatures up to 600 degrees C. As the soil is heated, the vapor pressure of the contaminant increases allowing mass transfer to the gas phase and extraction from the soil using vacuum wells. The overall goal of this research is to assess the feasibility of using ISTD to remove elemental mercury from soils. The initial phase of research included design of a laboratory soil column apparatus and preliminary soil column experiments with surrogate nonaqueous phase liquids (perfluorocarbons) to test the apparatus and investigate the effects of air flow rate and temperature on the ISTD process. Following the preliminary experiments, a mercury off-gas treatment system was added and mercury experiments were conducted. Experiments performed using elemental mercury showed greater than 99.8% removal of the mercury from Ottawa sand. These results show that ISTD can remove mercury from soil at temperatures well below its boiling point and that perfluorodecalin can be used as a surrogate for elemental mercury in laboratory experiments. A flow and transport simulator was used to model the results from both the perfluorocarbon and the mercury experiments. PMID:16646478

Kunkel, Anna M; Seibert, Jeremy J; Elliott, Lucas J; Kelley, Ricci; Katz, Lynn E; Pope, Gary A

2006-04-01

242

Temperature  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

243

Temperature programmed reduction for measurement of oxygen content in nanoscale zero-valent iron.  

PubMed

Nanoscale zerovalent iron (nZVI) has increasingly been used for environmental remediation and in toxic waste treatment. Most applications exploit its large surface area and high reactivity, the latter being a function of zerovalent iron content. In this work, temperature programmed reduction was applied to measure oxygen in nZVI. Iron oxides in nZVI were reduced by hydrogen to form metallic iron and water, which was then measured with an online mass spectrometer to determine oxygen content of the sample. For fresh nZVI prepared by sodium borohydride reduction of iron salts, average oxygen content was 8.21%. Total iron content was approximately 90.35% by the method of acid digestion; Fe(III) content was estimated at 14.37%, and that of zerovalent iron [Fe(0)] at 75.98%. The oxygen content quickly increased to 26.14% after purging with oxygen for four hours. Several other techniques were also used to characterize the iron nanoparticles. High resolution TEM provided direct evidence of the oxide shell structure and indicated that the shell thickness was predominantly in the range of 2-4 nm. The surface elemental composition was determined from high-resolution X-ray photoelectron spectroscopy. The nZVI oxygen content results fill a knowledge gap on nZVI composition. PMID:18546722

Cao, Jiasheng; Li, Xiaoqin; Tavakoli, Javad; Zhang, Wei-Xian

2008-05-15

244

Desorption of pentachlorophenol from soils using mixed solvents  

SciTech Connect

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

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

1999-12-15

245

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 ...

246

The regeneration characteristics of various red mud granular adsorbents (RMGA) for phosphate removal using different desorption reagents.  

PubMed

In this research, various red mud granular adsorbents (RMGA), which were made from red mud--a kind of waste residue from the alumina industry, were manufactured under different sintering temperatures (ST). For the purpose of investigating the regeneration characteristics of them for phosphate removal, systematic experiments were carried out, including adsorption, desorption (using different desorption reagents) and resorption tests. When RMGA were desorbed by HCl solutions, the desorption efficiencies were relatively higher due to acid erosion, but the corresponding resorption capacities became small owing to extraction of effective components. Although RMGA rarely released phosphate in desorption process when being desorbed by deionised water, it performed well on resorption of phosphate afterwards. It was assumed that the lower pH in resorption process, which was caused by the reductive release of CaO into solution, contributed to a weaker competition of OH(-) on phosphate resorption. When NaOH solution was employed as the desorption reagent, resorption capacities of RMGA were relatively larger and increased with the increase of NaOH concentration, because OH(-) might ameliorate the chemical composition on the surface of RMGA potentially. In addition, several RMGA manufactured under lower ST obtained larger resorption capacities than their original adsorption capacities, because of the comparatively unstable crystal structure which led to a stronger amelioration on them. PMID:20615614

Zhao, Yaqin; Yue, Qinyan; Li, Qian; Gao, Baoyu; Han, Shuxin; Yu, Hui

2010-10-15

247

Photon stimulated desorption of neutral species from aluminum  

SciTech Connect

Photon Simulated Desorption of neutral species (PSD) is the major dynamic gas load in electron synchrotron light source. In the National Synchrotron Light Source, PSD presented initial machine commissioning difficulty. Sensitivity to surface contamination on PSD had been experienced during an incident of Fomblin Oil contamination. U10B-Photon Stimulated Desorption Experimental Station is constructed to investigate: (1) the degree of the contribution to the photon stimulated desorption (PSD) from primary photon flux and scattered secondary photon flux, (2) the underlying mechanism for photon stimulated desorption, (3) criteria to chose the proper beam tube material for future a accelerator such as the Superconducting X-Ray Lithography Source (SXLS), Free Electron Laser (FEL), Superconducting Super Collider (SSC), Advanced Light Source (ALS) etc. In this report, only photon stimulated desorption of neutral species (PSD) from aluminum with different surface treatments is reported to show the great potential for this station to investigate beam tube material selection. 6 refs., 2 figs., 1 tab.

Chou, T.S.

1991-01-01

248

Adsorption and desorption studies on hazardous dye Naphthol Yellow S.  

PubMed

In the present study, the batch technique was adopted under a variety of conditions, viz., amount of adsorbent, contact time, concentration, temperature and pH. By using UV spectrophotometer, concentration of dye was measured before and after adsorption. Dye removal data were fitted into the Langmuir and Freundlich adsorption isotherm equations. The values of their corresponding constants were determined. Thermodynamic parameters like free energy (DeltaG), enthalpy (DeltaH) and entropy (DeltaS) of the systems were calculated by using Langmuir constant. The estimated values for (DeltaG) were -8.027x10(3) and -28.46x10(3) kJ mol(-1) over activated carbon and activated de-oiled mustard at 303 K (30 degrees C), indicate toward a spontaneous process. The adsorption process followed pseudo-first-order model. The values of % removal and k(ad) for dye systems were calculated at different temperatures ranging (303-323 K). Desorption studies indicate that elution by dilute NaOH through the fixed bed of the adsorbents columns could be regenerated and a quantitative recovery of Naphthol Yellow S can be achieved. PMID:20667651

Jain, Rajeev; Gupta, V K; Sikarwar, Shalini

2010-10-15

249

Effect of partial exfoliation in carbon dioxide adsorption-desorption properties of carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this study, we have experimentally studied the effect of partial exfoliation in low-pressure (<100 kPa) carbon dioxide adsorption and desorption behavior of multiwalled carbon nanotubes (MWNTs). MWNTs were partially exfoliated by controlled oxidation followed by hydrogen assisted low temperature exfoliation method. The adsorption capacity of partially exfoliated MWNTs (PEMWNTs) is 3.4 times that of MWNTs. Adsorption-desorption isotherms of MWNTs are unique, which shows trapping behavior. The desorption behavior in association with isothermal adsorbate retention of MWNTs and PEMWNTs suggests possible CO2 trapping inside the tubes and at interstitials. It is found that the CO2 adsorbed PEMWNTs system has higher molecular orbital energy than CO2 adsorbed MWNTs system. Areal adsorption capacity analysis suggests the significant influence of surface functional groups on adsorption capacity. Adsorption isosteres of both adsorbents follow the Arrhenius relation stating the temperature dependent adsorption rate. The isosteric heats and change in entropy of adsorption have been determined at multiple adsorbed amounts from the corresponding adsorption isosteres.

Tamilarasan, P.; Ramaprabhu, S.

2014-09-01

250

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

PubMed

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

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

2013-01-01

251

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

PubMed Central

Summary We present the results of our study about the deposition rate of focused electron beam induced processing (FEBIP) as a function of the substrate temperature with the substrate being an electron-transparent amorphous carbon membrane. When W(CO)6 is used as a precursor it is observed that the growth rate is lower at higher substrate temperatures. From Arrhenius plots we calculated the activation energy for desorption, E des, of W(CO)6. We found an average value for E des of 20.3 kJ or 0.21 eV, which is 2.53.0 times lower than literature values. This difference between estimates for E des from FEBIP experiments compared to literature values is consistent with earlier findings by other authors. The discrepancy is attributed to electron-stimulated desorption, which is known to occur during electron irradiation. The data suggest that, of the W(CO)6 molecules that are affected by the electron irradiation, the majority desorbs from the surface rather than dissociates to contribute to the deposit. It is important to take this into account during FEBIP experiments, for instance when determining fundamental process parameters such as the activation energy for desorption. PMID:24062973

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

2013-01-01

252

Probing water interactions and vacancy production on gadolinia-doped ceria surfaces using electron stimulated desorption.  

PubMed

Polycrystalline gadolinia-doped ceria (GDC) surfaces were studied using low-energy (5-400 eV) electron stimulated desorption (ESD). H(+), O(+), and H(3)O(+) were the primary cationic desorption products with H(+) as the dominant channel. H(+), H(3)O(+), and O(+) have a 22 eV threshold followed by a yield change around 40 eV. H(+) also has an additional yield change approximately 75 eV and O(+) has an additional change approximately 150 eV. The O(+) ESD yield change approximately 150 eV may indicate bond breaking of Gd-O and the involvement of oxygen vacancies. The H(+) and H(3)O(+) threshold data collectively indicate the presence of hydroxyl groups and chemisorbed water molecules on the GDC surfaces. ESD temperature dependence measurements show that the interaction of water with GDC surface defect sites, mainly oxygen vacancies, influences the desorption of H(+), O(+), and H(3)O(+). The temperature dependence of the O(+) ESD at 400 eV incident electron energy yields a 0.21 eV activation energy. This is close to the energy needed for oxygen vacancy production next to a pair of Ce(3+) on a CeO(2) surface. These results may indicate a correlation between the O(+) ESD yield and oxygen vacancy density on GDC surfaces and a potential correlation of O(+) ESD and GDC ionic conductivity. PMID:16852374

Chen, Haiyan; Aleksandrov, Alex; Chen, Yanfeng; Zha, Shaowu; Liu, Meilin; Orlando, Thomas M

2005-06-01

253

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 55C and 135C. 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

254

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

255

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

PubMed

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

Staymates, Matthew; Gillen, Greg

2012-07-01

256

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 55C and 135C. 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

257

Desorption of water cluster ions from the surface of solid rare gases  

NASA Astrophysics Data System (ADS)

Electron or photon irradiation of H2O adsorbed on the surface of rare gas solids induces the desorption of protonated water clusters, (H2O)nH+. The yield and the size n distribution of cluster ions depend on the coverage, the deposition temperature of the water, and the thickness of the rare gas film. These results indicate that the (H2O)nH+ ions originate from the isolated water clusters, and the most important factor determining the size n distribution of desorbed (H2O)nH+ is the sizes of water islands on the rare gas solid. The measurement of kinetic energy distributions indicated that the desorbing energy of clusters depend on the rare gas species of the substrates and the cluster size. It is suggested that the (H2O)nH+ desorption is due to Coulomb repulsion between the ionic water cluster and the rare gas ion.

Tachibana, T.; Miura, T.; Arakawa, I.

2006-11-01

258

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

SciTech Connect

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

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

2011-07-05

259

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

260

Modulated beam study of adsorption-induced-desorption reaction, H + D/Si(100) ' D2  

NASA Astrophysics Data System (ADS)

We have studied the kinetics mechanism of the adsorption-induced-desorption (AID) reaction, H + D/Si(100) ? D_2. Using a modulated H beam, two different types of AID reactions are revealed: one is the fast AID and the other is the slow AID reaction, occurring only at the beam on- and even at the beam off-cycles, respectively. Both the fast and slow AID reactions show the different dependence on surface temperature T_s, suggesting that their kinetics mechanisms are different. The fast AID reaction overwhelms the slow one in the desorption yield for all over the tested region 300K? Ts ? 650K. It proceeds along a first-order kinetics with respect to the incident H flux. Based on the experimental results, both two AID reactions are suggested to occur only on the 3 1 di-hydride phase accumulated under surface exposure to H atoms. Possible mechanisms for the two AID reactions are discussed.

Faridur Rahman, F. H. M.; Kiyonaga, T.; Tsurumaki, H.; Inanaga, S.; Namiki, A.

2004-03-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

262

Coincident thermal desorption and salt formation in CO+K coadsorbed layers  

NASA Astrophysics Data System (ADS)

Coadsorption of CO and K on metal surfaces leads to a mutual stabilization of both species and to their coincident thermal desorption. It is shown that the coincident desorption temperatures vary significantly with the nature of the metals and it increases in the sequence Cu-Pd-Ni-Ru-Pt-Rh-Fe: the difference between the lowest and highest value is about 239 K. It is concluded that neither salt formation nor the dissociation of CO, and hence the formation of a stable K-O species, could account for these features. It is proposed that a K 8+-CO ? surface complex is formed between CO and potassium which strongly interacts with the underlying metal. The stability of the complex on the surface is primarily determined by the bond strength of the CO with the host metal perturbed by potassium.

Solymosi, Frigyes; Berk, Andrs

1988-07-01

263

Application of central composite design in the optimisation of thermal desorption parameters for the trace level determination of the chemical warfare agent chloropicrin.  

PubMed

A quantitative trace-level thermal desorption gas chromatography mass spectrometry method was developed for chloropicrin CCl3NO2 using central composite design. Factors influencing the thermal decomposition were elucidated and optimum conditions for maximum response deduced. Four factors were investigated: desorption time, desorption temperature, valve temperature and line temperature. Only valve and line temperature influenced the response. The storage stability of chloropicrin on Tenax TA was investigated. Only the storage conditions affected recovery: no significant loss of chloropicrin was observed for spiked tubes stored in a refrigerator for up to 30 days. The application of central composite design to study thermal degradation of chloropicrin has not been described in the literature. The benefits in adopting this approach are reflected in the limit of detection, 22 ng on the sorbent tube (equivalent to 3.2 ppbv), the lowest atmospheric detection limit reported to date. PMID:12375843

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

2002-09-01

264

Integrated field emission array for ion desorption  

DOEpatents

An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

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

2013-09-17

265

Rickettsial hemolysis: adsorption, desorption, readsorption, and hemagglutination.  

PubMed Central

The energy-dependent adsorption of radioiodinated rickettsiae to sheep erythrocytes was demonstrated. The iodination procedure, however, decreased the hemolytic activity of the rickettsiae. No desorption of rickettsiae from isolated rickettsia-erythrocyte complexes (prevented from lysing by NaF) could be measured. On the other hand, rickettsiae desorbed from this complex during or after lysis and readsorbed and lysed other erythrocytes. Thus, the usual hemolytic assay measures multiple rounds of adsorption and lysis. Although lysis of the rickettsia-erythrocyte complex was insensitive to anti-rickettsial rabbit serum, adsorption and readsorption were completely inhibited by such antiserum. Hemagglutination of erythrocytes by rickettsiae was observed (in the presence of NaF to prevent lysis) and was sensitive to the same inhibitors as adsorption. Images PMID:409680

Winkler, H H

1977-01-01

266

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

SciTech Connect

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

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

2014-06-21

267

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

NASA Astrophysics Data System (ADS)

The desorption kinetics of deuterium from polycrystalline chemical vapor deposited diamond films were characterized by monitoring the isothermal thermionic emission current behavior. The reaction was observed to follow a first-order trend as evidenced by the decay rate of the thermionic emission current over time which is in agreement with previously reported studies. However, an Arrhenius plot of the reaction rates at each tested temperature did not exhibit the typical linear behavior which appears to contradict past observations of the hydrogen (or deuterium) desorption reaction from diamond. This observed deviation from linearity, specifically at lower temperatures, has been attributed to non-classical processes. Though no known previous studies reported similar deviations, a reanalysis of the data obtained in the present study was performed to account for tunneling which appeared to add merit to this hypothesis. Additional investigations were performed by reevaluating previously reported data involving the desorption of hydrogen (as opposed to deuterium) from diamond which further indicated this reaction to be dominated by tunneling at the temperatures tested in this study (<775 C). An activation energy of 3.19 eV and a pre-exponential constant of 2.3 1012 s-1 were determined for the desorption reaction of deuterium from diamond which is in agreement with previously reported studies.

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

2014-06-01

268

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

PubMed

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

Pastrana-Martnez, L M; Lpez-Ramn, M V; Moreno-Castilla, C

2009-03-01

269

High-temperature performance prediction of iron ore fines and the ore-blending programming problem in sintering  

NASA Astrophysics Data System (ADS)

The high-temperature performance of iron ore fines is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.

Yan, Bing-ji; Zhang, Jian-liang; Guo, Hong-wei; Chen, Ling-kun; Li, Wei

2014-08-01

270

Analysis of past relationships of temperature to hydrologic parameters. Global climate change response program. Final report  

Microsoft Academic Search

The relationship between surface temperature and precipitation is examined. Mean annual and seasonal values of temperature and precipitation for the Southern Plains area of the United States are compared. In general, there is a weak inverse relationship explaining, at best, 40 percent of the observed precipitation variability. Forty extreme precipitation events are studied in more detail. Nine surface temperature variables

Eddy

1991-01-01

271

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

PubMed

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

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

2013-07-01

272

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

273

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 90630?fmol). As LTP ionization method was applied and ionmolecule reactions took place in ambient atmosphere, various ionmolecule 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

274

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

275

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

Microsoft Academic Search

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

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

1996-01-01

276

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

Microsoft Academic Search

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

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

1999-01-01

277

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

PubMed Central

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

Zhang, Xiaotao; Wang, Ximing

2015-01-01

278

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

279

News on sputter theory: Molecular targets, nanoparticle desorption, rough surfaces  

NASA Astrophysics Data System (ADS)

Sputtering theory has existed as a mature and well-understood field of physics since the theory of collision-cascade sputtering has been developed in the late 1960s. In this presentation we outline several directions, in which the basic understanding of sputter phenomena has been challenged and new insight has been obtained recently. Sputtering of molecular solids: after ion impact on a molecular solid, not all of the impact energy is available for inducing sputtering. Part of the energy is converted into internal (rotational and vibrational) excitation of the target molecules, and part is used for molecule dissociation. Furthermore, exothermic or endothermic chemical reactions may further change the energy balance in the irradiated target. Nanoparticle desorption: usually, the flux of sputtered particles is dominated by monatomics; in the case of a pronounced spike contribution to sputtering, the contribution of clusters in the sputtered flux may become considerable. Here, we discuss the situation that nanoparticles were present on the surface, and outline mechanisms of how these may be desorbed (more or less intact) by ion or cluster impact. Rough surfaces: real surfaces are rough and contain surface defects (adatoms, surface steps, etc.). For grazing ion incidence, these influence the energy input into the surface dramatically. For such incidence angles sputtering vanishes for a flat terrace; however, ion impact close to a defect may lead to sputter yields comparable to those at normal incidence. In such cases sputtering also exhibits a pronounced azimuth and temperature dependence.

Urbassek, Herbert M.; Anders, Christian; Rosandi, Yudi

2011-05-01

280

A theoretical description and experimental demonstration of diffraction in electron-stimulated desorption.  

PubMed

The role of diffraction in electron-stimulated desorption (DESD) is demonstrated experimentally and described theoretically. Specifically, initial state effects in DESD of Cl (+) from Si(111)-(1 1):Cl and Si(111)-(7 7):Cl are examined and a theoretical treatment that includes spherical-wave effects and multiple scattering of low-energy incident electrons is presented. Although contributions from complicated defect configurations such as SiCl2 and SiCl3 cannot be ruled out, comparison of the experimental data with theory indicates that Cl (+) desorption from Si(111)-(1 1):Cl and Si(111)-(7 7):Cl surfaces may be dominated by monochloride terminal sites. The initial states probably contain significant Si 3s and/or Si-Cl ?-bonding character. In the Si(111)-(7 7):Cl case, these excitations favor a propensity for Cl (+) desorption from the unfaulted, rather than faulted, zones of the 7 7 reconstructed rest atom area. This propensity may be related to increased screening and hole localization in the Si-Si backbonds within the faulted region. Finally, introducing Debye-Waller factors into each scattering path accounts for much of the experimentally observed DESD width broadening at room temperature. PMID:21389377

Oh, Doogie; Sieger, Matthew T; Orlando, Thomas M

2010-03-01

281

A theoretical description and experimental demonstration of diffraction in electron-stimulated desorption  

NASA Astrophysics Data System (ADS)

The role of diffraction in electron-stimulated desorption (DESD) is demonstrated experimentally and described theoretically. Specifically, initial state effects in DESD of Cl + from Si(111)-(1 1):Cl and Si(111)-(7 7):Cl are examined and a theoretical treatment that includes spherical-wave effects and multiple scattering of low-energy incident electrons is presented. Although contributions from complicated defect configurations such as SiCl2 and SiCl3 cannot be ruled out, comparison of the experimental data with theory indicates that Cl + desorption from Si(111)-(1 1):Cl and Si(111)-(7 7):Cl surfaces may be dominated by monochloride terminal sites. The initial states probably contain significant Si 3s and/or Si-Cl ?-bonding character. In the Si(111)-(7 7):Cl case, these excitations favor a propensity for Cl + desorption from the unfaulted, rather than faulted, zones of the 7 7 reconstructed rest atom area. This propensity may be related to increased screening and hole localization in the Si-Si backbonds within the faulted region. Finally, introducing Debye-Waller factors into each scattering path accounts for much of the experimentally observed DESD width broadening at room temperature.

Oh, Doogie; Sieger, Matthew T.; Orlando, Thomas M.

2010-03-01

282

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

PubMed

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

Zhang, Xiaolong; Hu, Hongjiu; Guo, Manxia

2015-02-01

283

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

PubMed

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

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

2002-03-01

284

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

285

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

Microsoft Academic Search

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

Nicholas S. Samaras; Marwan A. Simaan

1998-01-01

286

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

NASA Technical Reports Server (NTRS)

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

Dempsey, Paula J.; Fabik, Richard H.

1993-01-01

287

Techniques for improving the accuracy of cryogenic temperature measurement in ground test programs  

NASA Technical Reports Server (NTRS)

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

Dempsey, Paula J.; Fabik, Richard H.

1993-01-01

288

Laser desorption mass spectrometry for biomolecule detection and its applications  

NASA Astrophysics Data System (ADS)

During the past few years, we developed and used laser desorption mass spectrometry for biomolecule detections. Matrix-assisted laser desorption/ionization (MALDI) was successfully used to detect DNA fragments with the size larger than 3000 base pairs. It was also successfully used to sequence DNA with both enzymatic and chemical degradation methods to produce DNA ladders. We also developed MALDI with fragmentation for direct DNA sequencing for short DNA probes. Since laser desorption mass spectrometry for DNA detection has the advantages of fast speed and no need of labeling, it has a great potential for molecular diagnosis for disease and person identification by DNA fingerprinting. We applied laser desorption mass spectrometry to succeed in the diagnosis of cystic fibrosis and several other nerve degenerative diseases such as Huntington's disease. We also succeeded in demonstrating DNA typing for forensic applications.

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

2001-08-01

289

Molecular beam-thermal hydrogen desorption from palladium  

SciTech Connect

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

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

2010-04-15

290

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 ...

291

Enhanced desorption ionization using oxidizing electrosprays.  

PubMed

A signal enhancement of two orders of magnitude was achieved when reactive desorption electrospray ionization (DESI) was used to investigate copper(II) dibutyl dithiocarbamate, Cu(II)(bu2dtc)2, found in a specialized polymer. Cu(II) was oxidized to Cu(III) during the DESI experiment by oxidants in the spray solvent. Such oxidants could be present or formed during electrospray (e.g., O2) or deliberately added to the spray solvent (this approach is called reactive DESI). When a strong oxidizing agent (e.g., iodine) was added to the spray solvent, the signal increased by two orders of magnitude relative to the pure solvent spray. The correlation between the standard reduction potential of the oxidant and the signal intensity and signal to noise ratio of the product ion for various reagents, was tested and discussed. The observed DESI enhancements in rates of oxidation are not observed in homogeneous solution. The major peaks in the collision induced dissociation (CID) spectrum of the complex ion Cu(III)(bu2dtc)2]+ were identified using isotopic distributions and MS3 data. PMID:16735130

Nefliu, Marcela; Cooks, R Graham; Moore, Colin

2006-08-01

292

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

293

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

294

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...

295

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

296

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

297

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

NASA Technical Reports Server (NTRS)

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

Ellis, J. R.

1985-01-01

298

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

NASA Technical Reports Server (NTRS)

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

Ellis, J. R.

1987-01-01

299

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

300

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

301

Leidenfrost phenomenon-assisted thermal desorption (LPTD) and its application to open ion sources at atmospheric pressure mass spectrometry.  

PubMed

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 1kDa) 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. PMID:23423791

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

2013-03-01

302

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 0.3s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1mm in 50ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~10(4)C/s at the filament temperature of 500C. 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

303

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

304

Use of a programmed temperature vaporizer for off-line SFE/GC analysis in food composition studies.  

PubMed

A simple procedure is proposed for off-line supercritical fluid extraction and capillary gas chromatography using a programmed temperature vaporizer (PTV) injector. The independent control of flow and temperature of the supercritical fluid is achieved by means of a variable restrictor (i.e., nozzle). The described system combines some advantages of the on-line coupling SFE/GC (high sensitivity and reduced sample handling) and the off-line approach (simpler performance and depressurization outside the chromatographic column). The proposed procedure and the solvent recovery method used to collect the extracted analytes are applied to the analysis of the essential oil obtained from Rosmarinus officinalis L. Also, a comparative study with the extracts obtained by using the simultaneous distillation extraction technique (SDE) is presented. PMID:8179209

Blanch, G P; Ibez, E; Herraiz, M; Reglero, G

1994-03-15

305

STRZ--A 7090 FORTRAN PROGRAM FOR THE STEADY-STATE TEMPERATURE DISTRIBUTION IN R-Z GEOMETRY WITH TEMPERATURE AND DIRECTION DEPENDENT HEAT CONDUCTION COEFFICIENTS AND RADIATION IN NARROW GAPS  

Microsoft Academic Search

A 7090 FORTRAN program for the calculation of the steady-state, ; rotationally symmetric temperature field in an inhomogeneous cylindrical body, in ; which heat production, radiation in narrow gaps, and heat conduction with ; temperature and direction dependent conduction coefficients may occur. The body ; can be divided into at most 70 regions of constant heat production rate and ;

B. H. Boonstra; F. W. Hoff; H. P. Struch

1963-01-01

306

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

307

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

SciTech Connect

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

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

2011-07-01

308

Influence of programmed circadian temperature changes upon levels of luteinizing hormone in the bovine.  

PubMed

A study was undertaken to determine the effects of controlled circadian patterns of elevated ambient temperatures (21-34 degrees C) upon the venous levels of luteinizing hormone (LH) in the bovine. Venous blood was collected from 8 16-month-old Angus heifers by indwelling cannulae to study LH levels in animals subjected to 2 ambient temperature regimes within 7 times 7.5 times 2.7 m psychrometric chambers. The control temperature regime was 17-21 degrees C diurnal variation, and the experimental temperature regime was 21-34 degrees C diurnal variation. The experimental regime significantly ( less than .05) decreased preovulatory and basal LH levels based upon 0800 and 1600 hour samples. Mean preovulatory LH levels were 6.4 ng/ml, where standard error of the mean (SEM) = 1.9 and number (n) = 16, in the control environment and 2.7 ng/ml (SEM = .9, N = 16) in the experimental regime. Comparable values for basal levels were .8 ng/ml (SEM = .02, n = 176). 7 of 8 animals exhibited an LH surge (greater than or equal to 4 ng/ml) while exposed to the control environment compared to only 3 of 8 at the experimental environment. PMID:4457134

Miller, H L; Alliston, C W

1974-09-01

309

Techniques for improving the accuracy of cryogenic temperature measurement in ground test programs  

Microsoft Academic Search

The performance of a sensor is often evaluated by determining to what degree of accuracy a measurement can be made using this sensor. The absolute accuracy of a sensor is an important parameter considered when choosing the type of sensor to use in research experiments. Tests were performed to improve the accuracy of cryogenic temperature measurements by calibration of the

Paula J. Dempsey; Richard H. Fabik

1993-01-01

310

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

Microsoft Academic Search

The performance of a sensor is often evaluated by determining to what degree of accuracy a measurement can be made using this sensor. The absolute accuracy of a sensor is an important parameter considered when choosing the type of sensor to use in research experiments. Tests were performed to improve the accuracy of cryogenic temperature measurements by calibration of the

Paula J. Dempsey; Richard H. Fabik

1993-01-01

311

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

SciTech Connect

A glovebox is described in which several environmental parameters are controlled and monitored. Included in these are particulate, tritium, water vapor, oxygen and temperature. The paper details the design rationale and process and describes the glovebox, presently in use for neutron generator production.

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

1996-07-01

312

Temperature-programmed surface reaction (TPSR) of CH 4 synthesis by Pd xNi 100- x nanoparticles  

NASA Astrophysics Data System (ADS)

A series of Pd xNi 100- x nanoparticles were prepared by the co-precipitation method and analyzed using a temperature-programmed surface reaction (TPSR) of their methanation reactions. ESCA measurement suggested that the as-prepared Pd-Ni alloys had Pd-core/Ni-shell structure. Surface Pd segregation occurred during H 2 reduction and resulted in a surface composition close to the nominal value. The TPSR experiments were performed by pre-adsorption of CO with H 2 to form methane. The peak temperature of methanation increased as Pd content increased, indicating that a methanation reaction is favored on Ni and Ni-rich alloy nanoparticles. For physical mixtures of Pd and Ni nanoparticles, methanation behaviors is similar to those of alloy nanoparticles; but the methanation temperatures of physical mixtures are always higher than those of alloy nanoparticles. This may be due to the formation of a Pd-enriched alloy surface layer during reduction in H 2 at 400 C, or because the CO molecules adsorbed on the Pd sites spill over onto the Ni sites for methanation. Using TPSR technique and measuring methanation temperature, the top-most surface of such bimetallic nanoparticles can be probed.

Wang, Kuan-Wen; Chung, Shu-Ru; Wei, Yu-Chen; Lee, Jyh-Fu; Perng, Tsong P.

2009-03-01

313

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

SciTech Connect

This report provides a description of the apparatus and the single cell testing results performed at Idaho National Laboratory during JanuaryAugust 2012. It is an addendum to the Small-Scale Test Report issued in January 2012. The primary program objectives during this time period were associated with design, assembly, and operation of two large experiments: a pressurized test, and a 4 kW test. Consequently, the activities described in this report represent a much smaller effort.

James O'Brien

2012-09-01

314

Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route  

NASA Astrophysics Data System (ADS)

Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance.Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance. Electronic supplementary information (ESI) available: TEM images, XRD patterns, N2 adsorption-desorption isotherms, TG-DTA curves, in situ time-resolved XRD patterns, stability test and H2O resistance study of the catalysts. See DOI: 10.1039/c3nr02631k

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

2013-09-01

315

Global climate change response program: Temperature-snowmelt analysis. Final report  

Microsoft Academic Search

A simple computer model for the Upper Colorado River above Glenwood Springs, Colorado, was written to determine possible effects of global climate changes in a small drainage basin near Glenwood Springs. First, an attempt was made to verify the 3.0 to 3.5 deg. F decrease in temperature per 1,000 feet increase in elevation which is frequently used on modeling snowmelt

Pick

1994-01-01

316

Characterization of hydrogen absorption/desorption states on lithium-carbon-hydrogen system by neutron diffraction  

NASA Astrophysics Data System (ADS)

The nanostructural hydrogenated graphite (CnanoHx) was synthesized from graphite by ball milling under hydrogen (H2) atmosphere. In this product, characteristic hydrogenated states in the form of polarized hydrocarbon groups (?CH, ?CH2, and ?CH3) are realized in the nanoscale. By synthesizing the composite of CnanoHx and lithium hydride (LiH), known as the Li ?C?H system, hydrogen was desorbed at 350C, which is a lower temperature compared to the decomposition temperature of each component. It is considered that this hydrogen desorption would be induced by destabilization of each hydrogen absorbed state due to an interaction between the polarized C ?H groups in CnanoHx and LiH. Therefore, in order to understand the hydrogen absorption/desorption mechanism of the Li ?C?H system, it is an important issue to investigate the change in the C ?H groups during hydrogen absorption/desorption reactions in the composite. The correlations among atoms contained in this composite are examined by neutron diffraction measurements, where the protium/deuterium (H/D) isotopic substitution was used to clarify the location of hydrogen atoms in this composite. Some C ?D and Li ?D correlations are found from the radial distribution function [RDF(r)] obtained by the neutron diffraction for the CnanoDx and LiD composite. After dehydrogenation, C ?C triple bond and Li ?C bond, ascribed to lithium carbide (Li2C2), are observed. Furthermore, the RDF(r ) corresponding to rehydrogenated composite indicates the presence of not only the Li ?D correlation but also the C ?D one.

Miyaoka, Hiroki; Itoh, Keiji; Fukunaga, Toshiharu; Ichikawa, Takayuki; Kojima, Yoshitsugu; Fuji, Hironobu

2008-09-01

317

Desorption process of GaAs surface native oxide controlled by direct Ga-beam irradiation  

NASA Astrophysics Data System (ADS)

In this study, the native oxide desorption process at GaAs(1 0 0) surface triggered by direct Ga molecular beam irradiation was investigated at a temperature of 440C in order to maintain surface flatness prior to molecular beam epitaxy (MBE). The oxide desorption process associated with the change in compositional and structural surface properties was characterized by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). With an increase in irradiated Ga dose, it is shown that an initial halo RHEED pattern from the native oxide layer transforms to a streaky one, indicating the desorption process taking place in a two-dimensional way with a decrease in oxide layer thickness. At a critical dose of 5.510 15 cm -2, which is confirmed by the change in RHEED intensities, the oxide layer is fully removed in conjunction with the smoothest surface morphology. Then the surface turns into a dark RHEED pattern corresponding to the accumulation of excess Ga in the form of droplets. The development of those surface properties monitored by RHEED is in good agreement with the change in root mean square (RMS) value of surface roughness obtained from AFM images. The minimum RMS roughness obtained is at the critical Ga dose, which is accurately controlled by RHEED measurements. The surface morphology treated at the critical Ga dose at 440C is maintained even after high-temperature annealing at 600C without causing deep pit. Therefore, the direct Ga-beam irradiation on GaAs oxide at 440C is considered to be an effective method providing a deoxidized smooth surface prior to MBE growth without the need of a buffer layer.

Asaoka, Y.

2003-04-01

318

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

PubMed Central

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

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

2015-01-01

319

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

SciTech Connect

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

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

1990-10-01

320

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 40kHz. 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 1ng. 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

321

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

322

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.; Lpez, J. J.; Kisi, O.; Shiri, J.

2012-04-01

323

A low-power pressure-and temperature-programmed separation system for a micro gas chromatograph.  

SciTech Connect

This thesis presents the theory, design, fabrication and testing of the microvalves and columns necessary in a pressure- and temperature-programmed micro gas chromatograph ({micro}GC). Two microcolumn designs are investigated: a bonded Si-glass column having a rectangular cross section and a vapor-deposited silicon oxynitride (Sion) column having a roughly circular cross section. Both microcolumns contain integrated heaters and sensors for rapid, controlled heating. The 3.2 cm x 3.2 cm, 3 m-long silicon-glass column, coated with a non-polar polydimethylsiloxane (PDMS) stationary phase, separates 30 volatile organic compounds (VOCs) in less than 6 min. This is the most efficient micromachined column reported to date, producing greater than 4000 plates/m. The 2.7 mm x 1.4 mm Sion column eliminates the glass sealing plate and silicon substrate using deposited dielectrics and is the lowest power and fastest GC column reported to date; it requires only 11 mW to raise the column temperature by 100 C and has a response time of 11s and natural temperature ramp rate of 580 C/min. A 1 m-long PDMS-coated Sion microcolumn separates 10 VOCs in 52s. A system-based design approach was used for both columns.

Sacks, Richard D. (University of Michigan, Ann Arbor, MI); Robinson, Alex Lockwood (Advanced Sensor Technologies, Albuquerque, NM); Lambertus, Gordon R. (University of Michigan, Ann Arbor, MI); Potkay, Joseph A. (University of Michigan, Ann Arbor, MI); Wise, Kensall D. (University of Michigan, Ann Arbor, MI)

2006-10-01

324

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

325

Nonthermal current-stimulated desorption of gases from carbon nanotubes.  

PubMed

The desorption of gases from carbon nanotubes is usually a slow process that limits the nanotubes' utility as sensors or as memristors. Here, we demonstrate that flow in the nanotube above the Poole-Frenkel conduction threshold can stimulate adsorbates to desorb without heating the sensor substantially. The method is general: alcohols, aromatics, amines, and phosphonates were all found to desorb. We postulate that the process is analogous to electron-stimulated desorption, but with an internally conducted rather than externally applied source of electrons. PMID:20829482

Salehi-Khojin, Amin; Lin, Kevin Y; Field, Christopher R; Masel, Richard I

2010-09-10

326

Adsorption and desorption in confined geometries: A discrete hopping model  

NASA Astrophysics Data System (ADS)

We study the adsorption and desorption kinetics of interacting particles moving on a one-dimensional lattice. Confinement is introduced by limiting the number of particles on a lattice site. Adsorption and desorption are found to proceed at different rates, and are strongly influenced by the concentration-dependent transport diffusion. Analytical solutions for the transport and self-diffusion are given for systems of length 1 and 2 and for a zero-range process. In the last situation the self- and transport diffusion can be calculated analytically for any length.

Becker, T.; Nelissen, K.; Cleuren, B.; Partoens, B.; Van den Broeck, C.

2014-12-01

327

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

328

Adsorption and desorption of thermally generated hydrogen atoms on Au(111) and Ag/Au(111)  

NASA Astrophysics Data System (ADS)

To explore the possibility of employing thermally generated H atoms to determine the chemical composition of a metallic surface, we investigated the adsorption and desorption of H atoms generated with a thermal cracker on surfaces Au(111) and Ag/Au(111). Angle-resolved photoemission spectra showed that the noble-metallic surfaces deteriorated upon exposure to a flux of H atoms at ~ 100 K. Upon subsequent annealing, the order of the surfaces was mostly recovered when H atoms on the surfaces desorbed, but the recovery was incomplete even with annealing at a temperature much higher than that at which H atoms desorb. X-ray photoemission spectra showed that O-containing contaminants existed on the surfaces after the H dosing. The evolution of O 1s during annealing indicated that the O-containing contaminants were H2O and its moieties generated during thermal cracking; the disturbances of the surfaces remaining above the desorption temperature of H atoms were likely caused by chemisorbed O. Our results show that it is possible to employ thermally generated H atoms to determine the chemical composition of a metallic surface, but a small proportion of H2O in a H2 gas line might be unavoidable; precautions against possible O contamination are required when a thermal cracker is employed.

Luh, Dah-An; Li, Kun-Rong; Huang, Ren-Yu; Chen, Ching-Hung; Cheng, Cheng-Maw; Tsuei, Ku-Ding; Wang, Chia-Hsin; Yang, Yaw-Wen

2015-05-01

329

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

330

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

PubMed

Palygorskite-montmorillonite (PM) was studied as a potential sewage treatment effluent filter material for carbamazepine. Batch sorption experiments were conducted as a function of granule size (0.3-0.6, 1.7-2.0 and 2.8mm) and different sewage effluent conditions (pH, ionic strength and temperature). Results showed PM had a mix of fibrous and plate-like morphologies. Sorption and desorption isotherms were fitted to the Freundlich model. Sorption is granule size-dependent and the medium granule size would be an appropriate size for optimizing both flow and carbamazepine retention. Highest and lowest sorption capacities corresponded to the smallest and the largest granule sizes, respectively. The lowest and the highest equilibrium aqueous (Ce) and sorbed (qe) carbamazepine concentrations were 0.4mgL(-1) and 4.5mgL(-1), and 0.6mgkg(-1) and 411.8mgkg(-1), respectively. Observed higher relative sorption at elevated concentrations with a Freundlich exponent greater than one, indicated cooperative sorption. The sorption-desorption hysteresis (isotherm non-singularity) indicated irreversible sorption. Higher sorption observed at higher rather than at lower ionic strength conditions is likely due to a salting-out effect. Negative free energy and the inverse sorption capacity-temperature relationship indicated the carbamazepine sorption process was favorable or spontaneous. Solution pH had little effect on sorption. PMID:25439731

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

2015-01-23

331

Microfabricated glow discharge plasma (MFGDP) for ambient desorption/ionization mass spectrometry.  

PubMed

A novel ambient ionization technique for mass spectrometry, microfabricated glow discharge plasma (MFGDP), is reported. This device is made of a millimeter-sized ceramic cavity with two platinum electrodes positioned face-to-face. He or Ar plasma can be generated by a direct current voltage of several hundreds of volts requiring a total power below 4 W. The thermal plume temperature of the He plasma was measured and found to be between 25 and 80 C at a normal discharge current. Gaseous, liquid, creamy, and solid samples with molecular weights up to 1.5 kDa could be examined in both positive and negative mode, giving limits of detection (LOD) at or below the fg/mm(2) level. The relative standard deviation (RSD) of manual sampling ranged from 10% to ~20%, while correlation coefficients of the working curve (R(2)) are all above 0.98 with the addition of internal standards. The ionization mechanisms are examed via both optical and mass spectrometry. Due to the low temperature characteristics of the microplasma, nonthermal momentum desorption is considered to dominate the desorption process. PMID:24000803

Ding, Xuelu; Zhan, Xuefang; Yuan, Xin; Zhao, Zhongjun; Duan, Yixiang

2013-10-01

332

Ex-Stream: A MATLAB program for calculating fluid flux through sediment-water interfaces based on steady and transient temperature profiles  

NASA Astrophysics Data System (ADS)

Temperature is a useful environmental tracer for quantifying movement and exchange of water and heat through and near sediment-water interfaces (SWI). Heat tracing involves analyzing temperature time series or profiles from temperature probes deployed in sediments. Ex-Stream is a MATLAB program that brings together two transient and two steady one-dimensional coupled heat and fluid flux analytical models. The program includes a graphical user interface, a detailed user manual, and postprocessing capabilities that enable users to extract fluid fluxes from time-series temperature observations. Program output is written to comma-separated values files, displayed within the MATLAB command window, and may be optionally plotted. The models that are integrated into Ex-Stream can be run collectively, allowing for direct comparison, or individually.

Swanson, Travis E.; Cardenas, M. Bayani

2011-10-01

333

Electron-stimulated cesium atom desorption from the Cs/CsAu/Au/W system  

NASA Astrophysics Data System (ADS)

This paper reports on a continuation of the investigation of electron-stimulated Cs-atom desorption from a tungsten surface on which cesium and gold films had been adsorbed at T = 300 K. Earlier studies revealed that Cs atoms start to desorb only after more than one monolayer of gold and more than one monolayer of cesium had been deposited on the tungsten surface. In this case, a coating consisting of a gold adlayer on tungsten, a CsAu compound possessing semiconducting properties, and a cesium monolayer capping CsAu (Cs/CsAu/Au/W) is formed on the tungsten surface at 300 K. The yield of atoms from this system exhibits a resonant dependence on the incident electron energy E e , with an appearance threshold of 57 eV and a maximum at 64 eV. In this case, Cs atoms desorb in two channels, with one of them involving Cs desorption out of the cesium monolayer, and the other, from the CsAu monolayer. The Cs yield at E e = 64 eV has been investigated in both desorption channels, with an additional cesium coating deposited on the already formed Cs/CsAu/Au/W layered system, as well as of the effect annealing produces on the yield and energy distributions of Cs atoms. It has been demonstrated that Cs atoms evaporated at 300 K on a layered coating with a cesium monolayer atop the CsAu layer on tungsten capped with a gold adlayer, rather than reflected from the cesium monolayer or adsorbing on it, penetrate through the cesium monolayer into the bulk of CsAu even with one CsAu layer present. The desorption yield does not vary with increasing cesium concentration at 300 K, but falls off gradually at 160 K. Annealing within the temperature range 320 K ? T H ? 400 K destroys the cesium monolayer and the one-layer CsAu coating, but the multilayer CsAu compound does not break up in this temperature range even after evaporation of the cesium monolayer. It is shown that Cs atoms escape from the multilayer CsAu compound primarily out of the top CsAu layer.

Ageev, V. N.; Kuznetsov, Yu. A.; Potekhina, N. D.

2010-09-01

334

Multivariate analysis of progressive thermal desorption coupled gas chromatography-mass spectrometry.  

SciTech Connect

Thermal decomposition of poly dimethyl siloxane compounds, Sylgard{reg_sign} 184 and 186, were examined using thermal desorption coupled gas chromatography-mass spectrometry (TD/GC-MS) and multivariate analysis. This work describes a method of producing multiway data using a stepped thermal desorption. The technique involves sequentially heating a sample of the material of interest with subsequent analysis in a commercial GC/MS system. The decomposition chromatograms were analyzed using multivariate analysis tools including principal component analysis (PCA), factor rotation employing the varimax criterion, and multivariate curve resolution. The results of the analysis show seven components related to offgassing of various fractions of siloxanes that vary as a function of temperature. Thermal desorption coupled with gas chromatography-mass spectrometry (TD/GC-MS) is a powerful analytical technique for analyzing chemical mixtures. It has great potential in numerous analytic areas including materials analysis, sports medicine, in the detection of designer drugs; and biological research for metabolomics. Data analysis is complicated, far from automated and can result in high false positive or false negative rates. We have demonstrated a step-wise TD/GC-MS technique that removes more volatile compounds from a sample before extracting the less volatile compounds. This creates an additional dimension of separation before the GC column, while simultaneously generating three-way data. Sandia's proven multivariate analysis methods, when applied to these data, have several advantages over current commercial options. It also has demonstrated potential for success in finding and enabling identification of trace compounds. Several challenges remain, however, including understanding the sources of noise in the data, outlier detection, improving the data pretreatment and analysis methods, developing a software tool for ease of use by the chemist, and demonstrating our belief that this multivariate analysis will enable superior differentiation capabilities. In addition, noise and system artifacts challenge the analysis of GC-MS data collected on lower cost equipment, ubiquitous in commercial laboratories. This research has the potential to affect many areas of analytical chemistry including materials analysis, medical testing, and environmental surveillance. It could also provide a method to measure adsorption parameters for chemical interactions on various surfaces by measuring desorption as a function of temperature for mixtures. We have presented results of a novel method for examining offgas products of a common PDMS material. Our method involves utilizing a stepped TD/GC-MS data acquisition scheme that may be almost totally automated, coupled with multivariate analysis schemes. This method of data generation and analysis can be applied to a number of materials aging and thermal degradation studies.

Van Benthem, Mark Hilary; Mowry, Curtis Dale; Kotula, Paul Gabriel; Borek, Theodore Thaddeus, III

2010-09-01

335

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

336

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 495C), 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

Tlgyessy, Peter; Vrana, Branislav; Krascsenits, Zoltn

2011-12-15

337

Laser-induced vibrational excitation and desorption in the Cs/Cu(1 1 1) and Na/Cu(1 1 1) systems  

NASA Astrophysics Data System (ADS)

The Cs/Cu(1 1 1) and Na/Cu(1 1 1) systems exhibit a transient excited electronic state localized on the adsorbate. Photo-excitation of this state triggers a motion of the alkali adsorbate away from the surface, leading to vibrational excitation of the adsorbate and possibly to desorption. A theoretical study of these photo-induced processes in the case of an exciting fs laser pulse is reported, based on a time-dependent approach of the adsorbate motion. The mean energy transfer from the laser photon energy to the adsorbate motion is shown to be weak, about 1% of the photon energy. Correspondingly, the vibrational excitation to high lying levels is very weak as well as the desorption process. The initial electronic state of the photo-induced process belongs to a continuum and vibrational excitation and desorption are found to vary rapidly with the energy of the initial electronic state. Initial vibrational excitation of the alkali adsorbate is also found to efficiently favour the desorption process, leading to a drastic variation of the desorption probability with the vibrational temperature of the adsorbate. The present results for the two systems are discussed and compared, in connection with available experimental data on these systems and on similar ones.

Gauyacq, J. P.; Kazansky, A. K.

2007-12-01

338

Electron Stimulated Desorption as a Source Mechanism for Ions in Mercury's Space Environment  

NASA Astrophysics Data System (ADS)

Electron-stimulated desorption experiments are performed using Na-bearing silicate targets to investigate nonthermal desorption and material removal processes on heterogeneous surfaces and interfaces under Mercurys conditions.

Orlando, T. M.; Sprague, A. L.; Grieves, G. A.; Schriver, D.; Trvn?ek, P. M.; McLain, J. L.; Starr, R. D.

2010-03-01

339

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

1995-01-01

340

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...

341

High-temperature-staged fluidized-bed combustion (HITS), bench scale experimental test program conducted during 1980. Final report  

SciTech Connect

An experimental program was conducted to evaluate the process feasibility of the first stage of the HITS two-stage coal combustion system. Tests were run in a small (12-in. ID) fluidized bed facility at the Energy Engineering Laboratory, Aerojet Energy Conversion Company, Sacramento, California. The first stage reactor was run with low (0.70%) and high (4.06%) sulfur coals with ash fusion temperatures of 2450/sup 0/ and 2220/sup 0/F, respectively. Limestone was used to scavenge the sulfur. The produced low-Btu gas was burned in a combustor. Bed temperature and inlet gas percent oxygen were varied in the course of testing. Key results are summarized as follows: the process was stable and readily controllable, and generated a free-flowing char product using coals with low (2220/sup 0/F) and high (2450/sup 0/F) ash fusion temperatures at bed temperatures of at least 1700/sup 0/ and 1800/sup 0/F, respectively; the gaseous product was found to have a total heating value of about 120 Btu/SCF at 1350/sup 0/F, and the practicality of cleaning the hot product gas and delivering it to the combustor was demonstrated; sulfur capture efficiencies above 80% were demonstrated for both low and high sulfur coals with a calcium/sulfur mole ratio of approximately two; gasification rates of about 5,000 SCF/ft/sup 2/-hr were obtained for coal input rates ranging from 40 to 135 lbm/hr, as required to maintain the desired bed temperatures; and the gaseous product yielded combustion temperatures in excess of 3000/sup 0/F when burned with preheated (900/sup 0/F) air. The above test results support the promise of the HITS system to provide a practical means of converting high sulfur coal to a clean gas for industrial applications. Sulfur capture, gas heating value, and gas production rate are all in the range required for an effective system. Planning is underway for additional testing of the system in the 12-in. fluid bed facility, including demonstration of the second stage char burnup reactor.

Anderson, R E; Jassowski, D M; Newton, R A; Rudnicki, M L

1981-04-01

342

Programs  

Cancer.gov

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

343

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

SciTech Connect

The role of nitrogen in the fabrication of designer diamond was systematically investigated by adding controlled amount of nitrogen in hydrogen/methane/oxygen plasma. This has led to a successful recipe for reproducible fabrication of designer diamond anvils for high-pressure high-temperature research in support of stockpile stewardship program. In the three-year support period, several designer diamonds fabricated with this new growth chemistry were utilized in high-pressure experiments at UAB and Lawrence Livermore National Laboratory. The designer diamond anvils were utilized in high-pressure studies on heavy rare earth metals, high pressure melting studies on metals, and electrical resistance measurements on iron-based layered superconductors under high pressures. The growth chemistry developed under NNSA support can be adapted for commercial production of designer diamonds.

Vohra, Yogesh, K.

2009-10-28

344

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

345

Adsorption\\/thermal desorption with small cartridges for the determination of trace aqueous semivolatile organic compounds  

Microsoft Academic Search

Adsorption\\/thermal desorption (ATD) with small bed volume (0.68 cm³) Tenax cartridges and direct desorption to a fused-silica capillary gas chromatography column has been studied for the determination of a wide range of semivolatile compounds in water. Recoveries were determined for a 5 min, 250°C desorption step alone, as well as for the complete ATD method. Desorption recoveries near 100% were

James F. Pankow; Mary P. Ligocki; Michael E. Rosen; Lorne M. Isabelle; Kenneth M. Hart

1988-01-01

346

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

347

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...

348

Improving electronic noses using a trap and thermal desorption unit  

Microsoft Academic Search

A novel small enrichment unit based on the trap and thermal desorption technique was used in combination with a portable electronic nose. A better detection limit is achieved due to the trapping procedure during sampling. A better selectivity is achieved by means of degradation of disturbing compounds from the analysis. Especially, the extraction of ethanol is important for the analysis

W Muenchmeyer; A Walte; G Matz

2000-01-01

349

Laser induced desorption as tritium retention diagnostic method in ITER  

Microsoft Academic Search

Measurement and control of long term tritium retention is one of the most critical issues for ITER and future fusion devices. Since the measurement of the hydrogenic retention by post mortem tile analysis becomes more and more difficult in future devices due to active water cooling and tile activation, Laser Induced Desorption Spectroscopy (LIDS) is under development in TEXTOR to

M. Zlobinski; V. Philipps; B. Schweer; A. Huber; S. Brezinsek; Ch. Schulz; S. Mller; U. Samm

2011-01-01

350

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...

351

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 ...

352

Matrix-assisted Laser Desorption of *Peptidesin Transmission Geometry  

E-print Network

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

Vertes, Akos

353

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...

354

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...

355

Nitrate sorption and desorption in biochars from fast pyrolysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

356

Surface Area, Adsorption, and Desorption Studies on Indoor Dust Samples  

Microsoft Academic Search

Adsorption by dust samples from homes was studied to evaluate the extent to which household dust particles could act as carriers of vapors into the lower respiratory tract. The dust samples were examined for volatilizable and combustible materials via thermogravimetric analysis as well as for specific surface area and surface characteristics by nitrogen and formaldehyde adsorption and desorption isotherms. Particle

SIMON J. ROTHENBERG; PAUL A. NAGY; JOHN A. PICKRELL; CHARLES H. HOBBS

1989-01-01

357

Modulated hydrogen beam study of adsorption-induced desorption of deuterium from Si(100)-31:D surfaces  

NASA Astrophysics Data System (ADS)

We have studied the kinetic mechanism of the adsorption-induced-desorption (AID) reaction, H+D/Si(100)?D2. Using a modulated atomic hydrogen beam, two different types of AID reaction are revealed: one is the fast AID reaction occurring only at the beam on-cycles and the other the slow AID reaction occurring even at the beam off-cycles. Both the fast and slow AID reactions show the different dependence on surface temperature Ts, suggesting that their kinetic mechanisms are different. The fast AID reaction overwhelms the slow one in the desorption yield for 300 K?Ts?650 K. It proceeds along a first-order kinetics with respect to the incident H flux. Based on the experimental results, both two AID reactions are suggested to occur only on the 31 dihydride phase accumulated during surface exposure to H atoms. Possible mechanisms for the AID reactions are discussed.

Rahman, F.; Kuroda, M.; Kiyonaga, T.; Khanom, F.; Tsurumaki, H.; Inanaga, S.; Namiki, A.

2004-08-01

358

High Temperature Turbine Technology Program: Phase II. Technology test and support studies. Technical progress report, July 1-September 30, 1980  

SciTech Connect

Work performed on the High Temperature Turbine Technology Program, Phase II-Technology Test and Support Studies during the period from 1 July 1980 through 30 September 1980 is summarized. Objectives of the program elements as well as technical progress and problems during this Phase II quarterly reporting period are presented. Planned progress during the next quarterly reporting period is also defined. Inspection results including static flow bench testing of blades and vanes following the final 300 h of teest of the LP Rig Engine with hot gas stream particulates are described. Modifications to the distillate fueled 60/sup 0/ combustor sector rig to improve the exit radial profile in the outer portion are described along with subsequent tests to evaluate the effectiveness of the modifications. Testing of the synthesized LBG-fueled 60/sup 0/ combustor sector rig was continued to evaluate the effect of burner inlet conditions and fuel loading variation on combustion performance. Modifications for redistribution of primary zone air flow are defined. Initial testing of the TSTR stator vane cascade using distillate fuel is described and modifications defined to improve stator vane cooling are presented. Initial motoring of the Turbine Spool Technology Rig and partial disassembly of the rig for anticipated combustor and blading modifications to improve vane and blade cooling are discussed. Supporting Material and Process investigations are described. The single spool reference turbine subsystem aerodynamic/thermodynamic evaluations of the turbine and combustor sections and design of these sections are presented and discussed.

Not Available

1980-10-01

359

Triphasic desorption of highly resistant chlorobenzenes, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons in field contaminated sediment  

Microsoft Academic Search

Pollutants in aged field sediments seem to differ from spiked sediments in their chemical and biological availability. Biphasic desorption is often used as an explanation. In the present study, desorption kinetics and partitioning of chlorobenzenes (CBs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) in long term field contaminated sediment cores and top layer sediment were measured by gas-purging. Desorption

E. M. T. Ten Hulscher; B. A. Vrind; H. van den Heuvel; L. E. van der Velde; P. C. M. van Noort; J. E. M. Beurskens; H. A. J. Govers

1999-01-01

360

Classical and quantum-mechanical models of thermal and flash desorption of atoms from surfaces  

Microsoft Academic Search

Two models, one classical and the other quantum-mechanical, for nonequilibrium thermal and flash desorption of atoms and molecules from surfaces are proposed, and their predictions are compared with those of previous (classical) models (of thermal desorption). Deviations from the equilibrium dependencies, on desorption angle, of (a) the desorbing atomic flux, (b) the average energy of desorbing atoms, and (c) the

Frank O. Goodman

1983-01-01

361

Effects of conformational isomerism on the desorption kinetics of n-alkanes from graphite  

E-print Network

Effects of conformational isomerism on the desorption kinetics of n-alkanes from graphite Kris R surfaces have been studied by measuring the desorption kinetics of a set of n-alkanes from the surface of single crystalline graphite. Desorption rates were measured using a set of 21 monodispersed n-alkanes

Gellman, Andrew J.

362

Justification of statistical overlap theory in programmed temperature gas chromatography: thermodynamic origin of random distribution of retention times.  

PubMed

A specific distribution of compounds' standard-state changes of enthalpy and entropy between mobile and stationary phases in programmed temperature gas chromatography (PTGC) is shown to produce the Poisson distribution of retention times often postulated in statistical-overlap theory (SOT). A three-part model is proposed, in which the enthalpy change is Poisson distributed, the average entropy change depends on the enthalpy change, and the actual entropy change varies in a uniformly random manner about the average entropy change. To test the model, the entropy and enthalpy changes of 350 aliphatic and aromatic hydrocarbons in petroleum were calculated with commercial GC software. These changes are shown to follow the three-part model. The model then was used with Monte Carlo methods to mimic the enthalpy and entropy changes. The substitution of the mimicked enthalpy and entropy changes into an equation for the retention temperature in PTGC is shown to produce a Poisson distribution of retention times that is statistically significant. This finding establishes a scientific link between the thermodynamics governing retention in PTGC and the superficially ad hoc assumption of the Poisson retention time distribution in SOT. Similar thermodynamic distributions are found for flavors and fragrances and for tetrachlorodibenzo-p-dioxins and furans, which follow SOT based on the Poisson distribution, but not for polychloronaphthalenes, which do not follow that SOT. PMID:11101251

Davis, J M; Pompe, M; Samuel, C

2000-11-15

363

Light-induced atomic desorption in cells with different PDMS coatings  

NASA Astrophysics Data System (ADS)

Light-induced atomic desorption (LIAD) is a non-thermal process in which atoms adsorbed at a surface are released under illumination. It is applied mostly to implementing optical dispensers in the cases when high atomic density at low temperature is needed - for example, for loading atomic devices as atomic magnetometers, atomic clocks, magneto-optical traps and their miniaturization. However, as the desorption depends on the atom-surface interaction, it can also be used for optical characterization and manipulation of alkali metal nanoparticles. The paper describes an experimental investigation of the shape of the transmission spectra and their dependence on the illuminating blue-light power in PDMS coated cells prepared with two different concentrations of PDMS in ether. A comparison is conducted with the LIAD effect in SC-77 coated and in uncoated cells. All measurements are performed on the Rb D2 line in vacuum. The potential is discussed for application of these dependences to analyzing the quality of the coating surface and its optimization.

Tsvetkov, S.; Gateva, S.; Taslakov, M.; Mariotti, E.; Cartaleva, S.

2014-05-01

364

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

365

Microwave-induced plasma desorption/ionization source for ambient mass spectrometry.  

PubMed

A new ionization source based on microwave induced plasma was developed for ambient desorption/ionization. The microwave-induced plasma desorption/ionization source (MIPDI) was composed of a copper Surfatron microwave cavity where a fused-silica tube was centered axially. Stable nonlocal thermodynamic equilibrium plasma was generated in the quartz discharge tube when a microwave at a frequency of 2450 MHz was coupled to the microwave cavity. Analytes deposited on the surface of poly(tetrafluoroethylene) (PTFE) or quartz slide after hydrofluoric acid (HF) etching were desorbed and ionized by the plasma. The performance of the MIPDI technique was validated by the analysis of a variety of chemical substances, polymer compounds, and pharmaceutical drugs using argon or helium as the discharge gas. Protonated [M + H](+) or deprotonated [M - H](-) ions were observed in the positive or negative mode. MIPDI was also used for the analysis of compounds in a complex matrix without any sample preparation. MIPDI was also capable of analyzing liquid samples. The signal-to-noise ratio was 463 in the analysis of 9.2 ng of phenylalanine, and the limit of detection was 60 pg for phenylalanine. MIPDI could desorb and ionize analytes with a molecular weight of up to 1200, which was demonstrated by the analysis of polyethylene glycol 800 (PEG800). MIPDI has advantages of simple instrumentation, relatively high temperature, stability, and reproducibility. PMID:23534913

Zhan, Xuefang; Zhao, Zhongjun; Yuan, Xin; Wang, Qihui; Li, Dandan; Xie, Hong; Li, Xuemei; Zhou, Meigui; Duan, Yixiang

2013-05-01

366

TEMLOPI\\/V.2: a computer program for estimation of fully transient temperatures in geothermal wells during circulation and shut-in  

Microsoft Academic Search

This paper describes the development, validation and application of the TEMLOPI\\/V.2 computer program. This program is a useful tool for estimating in-situ the transient temperature distribution of the fluids employed for drilling geothermal wells. TEMLOPI\\/V.2 is based on a mathematical model which is developed to consider two-dimensional transient heat transfer during drilling and shut-in conditions in and around a geothermal

G. Espinosa-Paredes; A. Garcia; E. Santoyo; I. Hernandez

2001-01-01

367

N-acetylglucosamine (GlcNAc) triggers a rapid, temperature-responsive morphogenetic program in thermally dimorphic fungi.  

PubMed

The monosaccharide N-acetylglucosamine (GlcNAc) is a major component of microbial cell walls and is ubiquitous in the environment. GlcNAc stimulates developmental pathways in the fungal pathogen Candida albicans, which is a commensal organism that colonizes the mammalian gut and causes disease in the setting of host immunodeficiency. Here we investigate GlcNAc signaling in thermally dimorphic human fungal pathogens, a group of fungi that are highly evolutionarily diverged from C. albicans and cause disease even in healthy individuals. These soil organisms grow as polarized, multicellular hyphal filaments that transition into a unicellular, pathogenic yeast form when inhaled by a human host. Temperature is the primary environmental cue that promotes reversible cellular differentiation into either yeast or filaments; however, a shift to a lower temperature in vitro induces filamentous growth in an inefficient and asynchronous manner. We found GlcNAc to be a potent and specific inducer of the yeast-to-filament transition in two thermally dimorphic fungi, Histoplasma capsulatum and Blastomyces dermatitidis. In addition to increasing the rate of filamentous growth, micromolar concentrations of GlcNAc induced a robust morphological transition of H. capsulatum after temperature shift that was independent of GlcNAc catabolism, indicating that fungal cells sense GlcNAc to promote filamentation. Whole-genome expression profiling to identify candidate genes involved in establishing the filamentous growth program uncovered two genes encoding GlcNAc transporters, NGT1 and NGT2, that were necessary for H. capsulatum cells to robustly filament in response to GlcNAc. Unexpectedly, NGT1 and NGT2 were important for efficient H. capsulatum yeast-to-filament conversion in standard glucose medium, suggesting that Ngt1 and Ngt2 monitor endogenous levels of GlcNAc to control multicellular filamentous growth in response to temperature. Overall, our work indicates that GlcNAc functions as a highly conserved cue of morphogenesis in fungi, which further enhances the significance of this ubiquitous sugar in cellular signaling in eukaryotes. PMID:24068964

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

2013-01-01

368

N-acetylglucosamine (GlcNAc) Triggers a Rapid, Temperature-Responsive Morphogenetic Program in Thermally Dimorphic Fungi  

PubMed Central

The monosaccharide N-acetylglucosamine (GlcNAc) is a major component of microbial cell walls and is ubiquitous in the environment. GlcNAc stimulates developmental pathways in the fungal pathogen Candida albicans, which is a commensal organism that colonizes the mammalian gut and causes disease in the setting of host immunodeficiency. Here we investigate GlcNAc signaling in thermally dimorphic human fungal pathogens, a group of fungi that are highly evolutionarily diverged from C. albicans and cause disease even in healthy individuals. These soil organisms grow as polarized, multicellular hyphal filaments that transition into a unicellular, pathogenic yeast form when inhaled by a human host. Temperature is the primary environmental cue that promotes reversible cellular differentiation into either yeast or filaments; however, a shift to a lower temperature in vitro induces filamentous growth in an inefficient and asynchronous manner. We found GlcNAc to be a potent and specific inducer of the yeast-to-filament transition in two thermally dimorphic fungi, Histoplasma capsulatum and Blastomyces dermatitidis. In addition to increasing the rate of filamentous growth, micromolar concentrations of GlcNAc induced a robust morphological transition of H. capsulatum after temperature shift that was independent of GlcNAc catabolism, indicating that fungal cells sense GlcNAc to promote filamentation. Whole-genome expression profiling to identify candidate genes involved in establishing the filamentous growth program uncovered two genes encoding GlcNAc transporters, NGT1 and NGT2, that were necessary for H. capsulatum cells to robustly filament in response to GlcNAc. Unexpectedly, NGT1 and NGT2 were important for efficient H. capsulatum yeast-to-filament conversion in standard glucose medium, suggesting that Ngt1 and Ngt2 monitor endogenous levels of GlcNAc to control multicellular filamentous growth in response to temperature. Overall, our work indicates that GlcNAc functions as a highly conserved cue of morphogenesis in fungi, which further enhances the significance of this ubiquitous sugar in cellular signaling in eukaryotes. PMID:24068964

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

2013-01-01

369

Reversible hydrogen desorption from LiBH4 catalyzed by graphene supported Pt nanoparticles.  

PubMed

The thermally induced de-/rehydrogenation performance of the graphene supported Pt nanoparticles (Pt/G) doped LiBH4 was greatly improved even at very low catalyst content due to a synergetic effect of Pt addition and nanoconfinement in graphene. For the 5 wt% Pt/G doped LiBH4 sample, the onset hydrogen desorption temperature is about 140 C lower than that of the pure LiBH4. With increasing loading of the Pt/G catalysts in LiBH4 samples, the onset dehydrogenation temperature and the two main desorption peaks from LiBH4 were found to decrease while the hydrogen release amount increased. About 17.8 wt% can be released from the 50 wt% Pt/G doped LiBH4 sample below 500 C. Moreover, variation of the equilibrium pressure (350-450 C) indicates that the dehydrogenation enthalpy is reduced from 74 kJ mol(-1) H2 for the pure LiBH4 to ca. 48 kJ mol(-1) H2 for the 10 wt% Pt/G doped LiBH4, showing improved thermodynamic properties. More importantly, a reversible capacity of ca. 8.1 wt% in the 30th de-/rehydrogenation cycle was achieved under 3 MPa H2 at 400 C for 10 h, indicating that the Pt/G catalysts play a crucial role in the improvement of the hydrogen uptake reversibility of LiBH4 at lower temperature and pressure conditions. Especially, LiBH4 was reformed and a new product, Li2B10H10, was detected after the rehydrogenation process. PMID:23719649

Xu, Juan; Qi, Zhongqing; Cao, Jianyu; Meng, Rongrong; Gu, Xiaofang; Wang, Wenchang; Chen, Zhidong

2013-09-28

370

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

SciTech Connect

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

Leckey, J.H.

1995-03-01

371

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

372

Nanoparticle-assisted laser desorption/ionization for metabolite imaging.  

PubMed

Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) has enabled the spatial analysis of various molecules, including peptides, nucleic acids, lipids, and drug molecules. To expand the capabilities of MALDI-IMS, we have established an imaging technique using metal nanoparticles (NPs) to visualize metabolites, termed nanoparticle-assisted laser desorption/ionization imaging mass spectrometry (nano-PALDI-IMS). By utilizing Ag-, Fe-, Au-, and TiO2-derived NPs, we have succeeded in visualizing various metabolites, including fatty acid and glycosphingolipids, with higher sensitivity and spatial resolution than conventional techniques. Herein, we describe the practical experimental procedures and methods associated with nano-PALDI-IMS for the visualization of these molecules. PMID:25361676

Waki, Michihiko; Sugiyama, Eiji; Kondo, Takeshi; Sano, Keigo; Setou, Mitsutoshi

2015-01-01

373

Single molecule desorption studies on immobilized nanoclay particle surfaces.  

PubMed

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

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

2010-06-01

374

Spatially resolved thermal desorption/ionization coupled with mass spectrometry  

DOEpatents

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

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

2013-02-26

375

About Temperature  

NSDL National Science Digital Library

Beverly Lynds at the Unidata Program Center has made available the About Temperature Web Site. Lynds provided a thorough discussion of temperature along with information about and diagrams of thermometers, heat and thermodymanics, kinetic theory, and radiation temperature. Additionally, she provides links to acknowledgment and external resources for further study.

Lynds, Beverly

376

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

377

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

PubMed

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

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

2015-02-01

378

Kinetics of Mercury(II) Adsorption and Desorption on Soil  

E-print Network

kinetics of Hg(II) on four soils at pH 6 were investigated to discern the mechanisms controllingKinetics 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

Sparks, Donald L.

379

Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry  

SciTech Connect

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

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

2012-01-03

380

Scale-dependent desorption of uranium from contaminated subsurface sediments  

Microsoft Academic Search

Column experiments were performed to investigate the scale-dependent desorption of uranyl [U(VI)] from a contaminated sediment collected from the Hanford 300 Area at the U.S. Department of Energy (DOE) Hanford Site, Washington. The sediment was a coarse-textured alluvial flood deposit containing significant mass percentage of river cobble. U(VI) was, however, only associated with its minor fine-grained (<2 mm) mass fraction.

Chongxuan Liu; John M. Zachara; Nikolla P. Qafoku; Zheming Wang

2008-01-01

381

Ultrasonic Enhanced Desorption of DDT from Contaminated Soils  

Microsoft Academic Search

In this study, using high-power low-frequency ultrasound, heated slurries with anionic surfactant sodium dodecyl sulfate (SDS)\\u000a were treated to enhance desorption of DDT from soils with high clay, silt, and organic matter content and different pH (5.68.4).\\u000a The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20wt.%\\u000a were studied. For

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

2011-01-01

382

Dehalogenation reactions in californium-252 plasma desorption mass spectrometry  

Microsoft Academic Search

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

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

1985-01-01

383

Increasing ion sorption and desorption rates of conductive electrodes  

DOEpatents

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

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

2014-12-30

384

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 (1.71.9 eV) suggesting similar

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

2008-01-01

385

System operation: Continuous volatile organic compound air monitoring of 56 ozone precursors with the Perkin-Elmer 8700 GC and automatic thermal desorption system  

SciTech Connect

As part of the Coastal Oxidant Assessment for Southeast Texas (COAST) program, two sites were chosen by the Texas Natural Resource Conservation Commission (TRNCC) and equipped with a Perkin-Elmer VOC system composed of the 8700 Gas Chromatograph, ATD-400 Automatic Thermal Desorption and Turbochrom III Data system on DEC computers. The systems were equipped with a dual capillary column application capable of resolving 56 distinct target ozone precursors. These components were separated and quantified on an hourly basis 24 hours each day. Each system generated 96 data files and approximately 30 documentation files each day totaling nearly 3 megabytes of information. The system was fully automated and monitored rigorously via high-speed modem communication. The modem communication proved to be essential in the handling of the large volume of data generated each day. A fully automated data transfer system was developed to allow unattended file archiving thus eliminating many problems associated with manual handling of files and facilitating the rapid evaluation of the data. This paper will identify the major issues in operation and maintenance of these systems (not including the chromatographic application). Problems which were encountered can be subdivided into 2 categories, (a) hardware system problems such as power failures, equipment malfunction and temperature/humidity fluctuations, and (b) software issues: capability/incompatibility, bugs, communication problems and a plethora of computer or computer-related issues (confusion).

Radenheimer, P. [Consolidated Sciences Corp., Pasadena, TX (United States); Gibich, J. [Texas Natural Resource Conservation Commission, Austin, TX (United States); Ogle, L. [Radian Corp., Austin, TX (United States)

1994-12-31

386

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

SciTech Connect

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

None

1981-06-01

387

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.

388

LASER DESORPTION IONIZATION MASS SPECTROMETRY ON SILICON NANOWELL ARRAYS  

PubMed Central

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

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

2010-01-01

389

Production of negative osmium ions by laser desorption and ionization  

NASA Astrophysics Data System (ADS)

The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs+ ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionization with pulsed lasers and identification of the ions by time-of-flight mass spectrometry. First investigations of negative osmium ion production using a pulsed laser for desorption and ionization and a commercial matrix-assisted laser desorption/ionization time-of-flight system for identification has demonstrated the suitability of this technique. More than 103 negative osmium ions per shot were registered after bombarding pure osmium powder with a 5 ns pulse width Nd:yttrium aluminum garnet laser. The limitation in the ion number was imposed by the detection limit of the microchannel plate detector.

Rodrguez, D.; Sonnenschein, V.; Blaum, K.; Block, M.; Kluge, H.-J.; Lallena, A. M.; Raeder, S.; Wendt, K.

2010-01-01

390

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-Jrgen; Kiersnowski, Adam

2014-10-01

391

Laser desorption lamp ionization source for ion trap mass spectrometry.  

PubMed

A two-step laser desorption lamp ionization source coupled to an ion trap mass spectrometer (LDLI-ITMS) has been constructed and characterized. The pulsed infrared (IR) output of an Nd:YAG laser (1064?nm) is directed to a target inside a chamber evacuated to ~15?Pa causing desorption of molecules from the target's surface. The desorbed molecules are ionized by a vacuum ultraviolet (VUV) lamp (filled with xenon, major wavelength at 148?nm). The resulting ions are stored and detected in a three-dimensional quadrupole ion trap modified from a Finnigan Mat LCQ mass spectrometer operated at a pressure of ? 0.004?Pa. The limit of detection for desorbed coronene molecules is 1.5?pmol, which is about two orders of magnitude more sensitive than laser desorption laser ionization mass spectrometry using a fluorine excimer laser (157?nm) as the ionization source. The mass spectrum of four standard aromatic compounds (pyrene, coronene, rubrene and 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (OPC)) shows that parent ions dominate. By increasing the infrared laser power, this instrument is capable of detecting inorganic compounds. Copyright 2015 John Wiley & Sons, Ltd. PMID:25601688

Wu, Qinghao; Zare, Richard N

2015-01-01

392

Unexpected Analyte Oxidation during Desorption Electrospray Ionization - Mass Spectrometry  

SciTech Connect

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

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

2008-01-01

393

The desorptivity model of bulk soil-water evaporation  

NASA Technical Reports Server (NTRS)

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

Clapp, R. B.

1983-01-01

394

Adsorption-desorption behavior of thiram onto humic acid.  

PubMed

The adsorption/desorption behavior of pure thiram (Thi-P) and formulated thiram (Thi-F) onto commercial humic acids (HA) was studied using a batch equilibration procedure. Results of adsorption kinetic experiments showed that thiram adsorption is a fast process since 85% of the equilibrium concentration is reached within two hours. Experimental K(D) values between 0.110 to 0.210 L g(-1) were obtained for the adsorption of both Thi-P and Thi-F onto HA, suggesting that thiram is strongly sorbed by humic acids. In general, for both Thi-P and Thi-F, the lower the initial thiram concentration, the stronger is its adsorption (higher K(D) and percentage adsorption values). The adsorption isotherms were found to match the BET model. The results show that thiram adsorption onto condensed humic acids cannot be explained only in terms of specific interactions, such as those identified in studies of adsorption of thiram with humic acids in solution. The comparison of sorption and desorption results allowed the observation of hysteresis phenomena. Desorption K(D) values were consistently higher than those for adsorption at the same equilibrium concentration. Hysteresis was lower for the formulated thiram suggesting that adsorption is more reversible in the presence of the formulation components turning the pesticide more susceptible to be leached. PMID:19425576

Filipe, O M S; Vidal, M M; Duarte, A C; Santos, E B H

2009-06-10

395

Ambient aerodynamic desorption/ionization method for microparticle mass measurement.  

PubMed

An ambient desorption/ionization method, named aerodynamic desorption (AD), was proposed for the in situ rapid mass measurement of microparticles. The AD method exploited the discontinuous atmospheric pressure interface (DAPI) to generate a pulsed airflow, which was used to desorb the microparticles under atmospheric pressure. Various microparticles, e.g., bacteria, cell, polystyrene, synthetic diamond, and silica particles, with different size and surface component were successfully desorbed. Similar to that in the conventional laser-induced acoustic desorption (LIAD) method, these microparticles were desorbed as precharged ions in the AD process and the charge number was largely relevant to the particle size. However, compared with LIAD, the sensitivity of the AD method was higher. A lower concentration of particles was required for the analysis. In addition, the construction and sampling process of AD source were much simpler. All types of liquid, solid, or/and gaseous samples can be directly sampled under ambient condition. As a demonstration of this AD method, the in situ mass analysis of red blood cells (RBCs) and E. coli bacteria were carried out using a homemade ambient AD mass spectrometer consisting of AD source, QIT mass analyzer, and charge detector. Their mass and mass distributions were obtained successfully. PMID:23534443

Xiong, Caiqiao; Zhou, Xiaoyu; Wang, Jianing; Zhang, Ning; Peng, Wen-Ping; Chang, Huan-Cheng; Nie, Zongxiu

2013-05-01

396

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

397

Sorption and desorption of lead (II) from wastewater by green algae Cladophora fascicularis.  

PubMed

Biosorption is an effective method to remove heavy metals from wastewater. In this work, adsorption features of Cladophora fascicularis were investigated as a function of time, initial pH, initial Pb(II) concentrations, temperature and co-existing ions. Kinetics and equilibria were obtained from batch experiments. The biosorption kinetics followed the pseudo-second order model. Adsorption equilibria were well described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity was 198.5 mg/g at 298K and pH 5.0. The adsorption processes were endothermic and the biosorption heat was 29.6 kJ/mol. Desorption experiments indicated that 0.01 mol/L Na(2)EDTA was an efficient desorbent for the recovery of Pb(II) from biomass. IR spectrum analysis suggested amido or hydroxy, CO and C-O could combine intensively with Pb(II). PMID:17049733

Deng, Liping; Su, Yingying; Su, Hua; Wang, Xinting; Zhu, Xiaobin

2007-05-01

398

Diffusion of electronic defects in calcia-stabilized zirconia from a desorption rate study  

SciTech Connect

This paper reports on rates of desorption of oxygen from samples of calcis-stabilized zirconia (CSZ) measured as a function of oxygen saturation pressure, of temperature, and of the impurity content of CSZ. The results have been interpreted to determine the diffusion coefficient, {ital D}, for electronic defects in CSZ. {ital D} was independent of the oxygen saturation pressure from 0.5 to 101 kPa. The activation energy was 88 kJ/mol for one sample from 1228 to 1577 K and 113 kJ/mol for another from 1515 to 1667 K. {ital D} was inversely proportional to the iron impurity concentration in the CSZ. This observation was interpreted in terms of a mechanism in which electron holes were trapped by iron impurity sites.

Dou, S. (Dept. of Materials Science and Engineering, Univ. of New South Wales, Kensington (AU)); Masson, C.R. (Atlantic Research Lab., National Research Council, Halifax, Nova Scotia, B3H 3Z1 (CA)); Pacey, P.D. (Dept. of Chemistry, Dalhousie Univ., Halifax, Nova Scotia, B3H 4J3 (CA))

1990-11-01

399

Electron-stimulated desorption of silicates: A potential source for ions in Mercury's space environment  

NASA Astrophysics Data System (ADS)

The potential role of electron-stimulated desorption (ESD) in the formation of Mercury's exosphere has been examined. Experimental results involving electron irradiation of Na- and K-bearing silicate glasses yielded direct desorption of H+, H2+, O+, H3O+, Na+, K+, and O2+. A simulation has also been performed to calculate electron precipitation fluxes and energies that may be used in the interpretation of measurements made by MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) spacecraft instruments and to better understand the formation of the ion and neutral exosphere at Mercury. The electron fluxes are estimated to be 1010 cm-2 s-1 with average energies up to 500 eV. The threshold energies for production/release of ions have been measured to be 25 2 eV for H+; 30 2 eV for O+, Na+, and K+; 40 2 eV for H2+ and H3O+; and 90 2 eV for O2+. The 25-30 eV thresholds correlate with deep valence holes in the O 2s levels that undergo Auger decay. The thresholds for H2+ and H3O+ correspond to two-hole states in chemisorbed water, which produce energetic protons that undergo reactive scattering on the surface. A significant increase in ESD yield of all ions is observed above a substrate temperature of 350 K. The estimated total cross section for ESD at a surface temperature of 400 K is ?10-19 cm2, much larger than neutral production followed by electron impact ionization or photoionization in the gas phase. These results indicate that ESD may contribute to the production and release of regolith constituents, particularly in ionic form, directly into the exosphere of Mercury.

McLain, Jason L.; Sprague, Ann L.; Grieves, Gregory A.; Schriver, David; Travinicek, Pavel; Orlando, Thomas M.

2011-03-01

400

Structural changes of thin MgAl films during hydrogen desorption  

NASA Astrophysics Data System (ADS)

We used neutron reflectometry (NR) to study the structural changes of thin Pd-capped Mg 0.7Al 0.3 and Mg 0.6Al 0.4 alloy films after hydrogen absorption and during hydrogen desorption. NR enabled us to determine the hydrogen content and hydrogen distribution in these thin MgAl alloy films along with the structural changes associated with the desorption process. The thin films expand by about 20% during the hydrogen absorption and the hydrogen is stored only in the MgAl layer with no hydrogen content in the Pd layer. The Mg 0.7Al 0.3 films are fully desorbed at 448 K, whereas for the Mg 0.6Al 0.4 films a temperature of 473 K is needed to fully desorb the hydrogen. Our NR measurements show that the higher annealing temperature needed to desorb the hydrogen from the Mg 0.6Al 0.4 films led to an interdiffusion of the Pd layer into the MgAl layer. This Pd interdiffusion was also observed in a Mg 0.7Al 0.3 film after a 9 h annealing at 473 K. So, the Pd interdiffusion into a MgAl film that has been charged with hydrogen is a common feature of the Pd/Mg 0.7Al 0.3 and Pd/Mg 0.6Al 0.4 alloy system. In contrast, for the as-prepared hydrogen-free Pd/Mg 0.7Al 0.3 film the Pd layer stays intact and only a small interdiffusion zone occurs at the Pd/MgAl interface.

Fritzsche, Helmut; Saoudi, Mouna; Haagsma, Julian; Ophus, Colin; Harrower, Chris T.; Mitlin, David

2009-02-01

401

Heavy-ion irradiation defect accumulation in ZrN characterized by TEM, GIXRD, nanoindentation, and helium desorption  

NASA Astrophysics Data System (ADS)

A study on zirconium nitride was performed to assess the effect of radiation damage by heavy ions at cryogenic and elevated temperatures. Cross-sectional transmission electron microscopy, grazing incidence X-ray diffraction, nanoindentation, and helium desorption studies were used to assess the damage and its effects. Xenon and krypton were used as heavy ions at 300 keV to displacement damage as high as 200 dpa. Implants were cryogenic, 350 C, 580 C, and 800 C. Amorphization was not observed at low temperatures nor was bubble formation observed at elevated temperatures, however, defect migration was observed at elevated temperatures. Nanoindenter results showed the onset of defect saturation. Helium release studies were performed to show the effect of increasing damage by Xe to 40 dpa.

Egeland, G. W.; Valdez, J. A.; Maloy, S. A.; McClellan, K. J.; Sickafus, K. E.; Bond, G. M.

2013-04-01

402

Ion desorption efficiency and internal energy transfer in carbon-based surface-assisted laser desorption/ionization mass spectrometry: desorption mechanism(s) and the design of SALDI substrates.  

PubMed

Ion desorption efficiency and internal energy transfer were probed and correlated in carbon-based surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using benzylpyridinium (BP) salt as the thermometer chemical. In a SALDI-MS experiment with a N(2) laser (at 337 nm) used as the excitation light source and with multiwalled carbon nanotubes (CNT), buckminsterfullerene (C(60)), nanoporous graphitic carbon (PGC), non-porous graphite particles (G), highly oriented pyrolytic graphite (HOPG), or nanodiamonds (ND) as the SALDI substrate, both the desorption efficiency in terms of ion intensity of BP and the extent of internal energy transfer to the ions are dependent on the type and size of the carbon substrates. The desorption efficiency (CNT approximately C(60) > PGC > G > HOPG > ND) in general exhibits an opposite trend to the extent of internal energy transfer (CNT < C(60) approximately PGC < G approximately HOPG < ND), suggesting that increasing the extent of internal energy transfer in the SALDI process may not enhance the ion desorption efficiency. This phenomenon cannot be explained by a thermal desorption mechanism, and a non-thermal desorption mechanism is proposed to be involved in the SALDI process. The morphological change of the substrates after the laser irradiation and the high initial velocities of BP ions (1100-1400 ms(-1)) desorbed from the various carbon substrates suggest that phase transition/destruction of substrates is involved in the desorption process. Weaker bonding/interaction and/or a lower melting point of the carbon substrates favor the phase transition/destruction of the SALDI substrates upon laser irradiation, consequently affecting the ion desorption efficiency. PMID:19449861

Tang, Ho-Wai; Ng, Kwan-Ming; Lu, Wei; Che, Chi-Ming

2009-06-15

403

Highly efficient electron-stimulated desorption of benzene from amorphous solid water ice  

NASA Astrophysics Data System (ADS)

The desorption of benzene (C6H6) from the surface of compact amorphous solid water (ASW) during irradiation with electrons in the range 100-350 eV has been investigated. Two desorption components, with particularly large cross-sections, were present in the observed desorption signal. The fast component, with a cross-section of >10-15cm2, is attributed to desorption of isolated C6H6 molecules that are ?-hydrogen bonded to small clusters of water (H2O) molecules on the compact ASW surface. The slower component, with a cross-section of ca. 10-16cm2, is attributed to a more complex desorption process involving larger C6H6 islands on the compact ASW surface. Possible desorption mechanisms are discussed.

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

2011-03-01

404

Quantum dynamics of laser-induced desorption from metal and semiconductor surfaces, and related phenomena  

Microsoft Academic Search

Recent progress towards a quantum theory of laser-induced desorption and related phenomena is reviewed, for specific examples. These comprise the photodesorption of NO from Pt(111), the scanning tunnelling microscope and laser-induced desorption and switching of H at Si(100), and the electron stimulated desorption and dissociation of CO at Ru(0001). The theoretical methods used for nuclear dynamics range from open-system density

Peter Saalfrank; Mathias Nest; Ivan Andrianov; Tillmann Klamroth; Dominik Krner; Stephanie Beyvers

2006-01-01

405

Kinetics of neptunium(V) sorption and desorption on goethite: An experimental and modeling study  

Microsoft Academic Search

Various sorption phenomena, such as aging, hysteresis and irreversible sorption, can cause differences between contaminant (ad)sorption and desorption behavior and lead to apparent sorption asymmetry. We evaluate the relevance of these characteristics for neptunium(V) (Np(V)) sorption\\/desorption on goethite using a 34-day flow-cell experiment and kinetic modeling. Based on experimental results, the Np(V) desorption rate is much slower than the (ad)sorption

Ruth M. Tinnacher; Mavrik Zavarin; Brian A. Powell; Annie B. Kersting

2011-01-01

406

Kinetics of neptunium(V) sorption and desorption on goethite: An experimental and modeling study  

Microsoft Academic Search

Various sorption phenomena, such as aging, hysteresis and irreversible sorption, can cause differences between contaminant (ad)sorption and desorption behavior and lead to apparent sorption 'asymmetry'. We evaluate the relevance of these characteristics for neptunium(V) (Np(V)) sorption\\/desorption on goethite using a 34-day flow-cell experiment and kinetic modeling. Based on experimental results, the Np(V) desorption rate is much slower than the (ad)sorption

Ruth M. Tinnacher; Mavrik Zavarin; Brian A. Powell; Annie B. Kersting

2011-01-01

407

Scavenging of BHCs and DDTs from soil by thermal desorption and solvent washing.  

PubMed

Intensive remediation of abandoned former organochlorine pesticides (OCPs) manufacturing areas is necessary because the central and surrounding soils contaminated by OCPs are harmful to crop production and food safety. Organochlorine and its residues are persistent in environments and difficult to remove from contaminated soils due to their low solubility and higher sorption to the soils. We performed a comprehensive study on the remediation of OCPs-contaminated soils using thermal desorption technique and solvent washing approaches. The tested soil was thermally treated at 225, 325, 400, and 500 C for 10, 20, 30, 45, 60, and 90 min, respectively. In addition, we tested soil washing with several organic solvents including n-alcohols and surfactants. The optimal ratio of soil/solvent was tested, and the recycling of used ethanol was investigated. Finally, activities of polyphenol oxidase (PPO), urease (URE), alkaline phosphatase, acid phosphatase (ACP), and invertase (INV) were assayed in the treated soils. The tested soil was thermally treated at 500 C for 30 min, and the concentration of contaminants in soil was decreased from 3,115.77 to 0.33 mg kg(-1). The thermal desorption in soil was governed by the first-order kinetics model. For the chemical washing experiment, ethanol showed a higher efficiency than any other solvent. Using a 1:20 ratio of soil/solvent, the maximum removal of OCPs was achieved within 15 min. Under this condition, approximately 87 % of OCPs was removed from the soils. More than 90 % of ethanol in the spent wash fluid could be recovered. Activities of some enzymes in soils were increased after ethanol treatment. But ALP, ACP, and INV activities were decreased and PPO and URE showed slightly higher activities following remediation by thermal treatment. Both heating temperature and time were the key factors for thermal desorption of OCPs. The n-alcohol solvent showed higher removal of OCPs from soils than surfactants. The highly efficient removal of OCPs from soil was achieved using ethanol. More than 90 % of ethanol could be recovered and be reused following distillation. This study provides a cost-effective and highly efficient way to remediate the OCPs-contaminated soils. PMID:22661262

Gao, Yan Fei; Yang, Hong; Zhan, Xin Hua; Zhou, Li Xiang

2013-03-01

408

Photo-stimulated desorption from water and methane clusters on the surface of solid neon  

NASA Astrophysics Data System (ADS)

Photo-stimulated desorption of ions from methane and water heteroclusters on the surface of solid neon was studied. The desorption yields of various photo-desorbed species showed strong dependence on the composition and size of the mother cluster. It was found that presence of a water molecule in the cluster significantly enhanced, or was almost essential for, desorption of all species observed. Systematic investigation of the correlation between the cluster size and desorption yield of each ion revealed the corresponding mother cluster for each species of the desorbed ions.

Arakawa, Ichiro; Matsumoto, Daigo; Takekuma, Shinichi; Tamura, Reimi; Miura, Takashi

2012-08-01

409

Effective desorption of tritium from diverse solid matrices and its application to routine analysis of decommissioning materials.  

PubMed

Tritium extraction from materials is most commonly carried out using oxidative thermal desorption in purpose-built furnace systems and typically involves trapping the product in a water bubbler which is sampled for measurement using liquid scintillation counting (LSC). The performance of perhaps the most widely used commercial system, the Raddec Pyrolyser, has been evaluated for a broad range of sample types. Several parameters that were expected to affect tritium desorption and recovery were systematically studied. These included sample heating rates and end-point temperatures, carrier/oxidant gas flows, catalyst temperature, bubbler trapping and carry-over/memory effects. A catalyst such as platinised-alumina is used to ensure the quantitative oxidation of volatile combustion products to HTO and CO(2). This also ensures that the trapped decomposition products do not colourise the bubbler solutions that are subsequently sampled for LSC. Tritium evolution profiles were determined for a range of sample types and were obtained by systematically changing bubblers at a set of progressively increasing temperatures. These experiments showed the maximum heating temperature and total combustion time required for the complete recovery of tritium from samples was dependent on the sample matrix types and the (3)H form. These evolution profiles need only be determined once and are readily transferable to other Pyrolyser systems. For example tritiated water is rapidly liberated from samples at temperature around 100 degrees C whereas (3)H substituted for structural H in organic species can require a temperature in excess of 300 degrees C to be released. Higher temperatures (up to 900 degrees C) are needed to liberate (3)H originating from neutron capture reactions on trace Li or B within a material (e.g. reactor graphite or concrete). The furnace system investigated is highly effective at extracting tritium and (14)C from all sample types studied (soil, sediment, biota, wood, metal, plastic, concrete, graphite, etc.) and overall it demonstrates high and reproducible recoveries. PMID:20800748

Warwick, P E; Kim, D; Croudace, I W; Oh, J

2010-08-31

410

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

411

Desorption electrospray ionization imaging of small organics on mineral surfaces.  

PubMed

Desorption electrospray ionization (DESI)-mass spectrometry facilitates the ambient chemical analysis of a variety of surfaces. Here we describe the protocol for using DESI imaging to measure the distributions of small prebiotically relevant molecules on granite surfaces. Granites that contain a variety of juxtaposed mineral species were reacted with formamide in order to study the role of local mineral environment on the production of purines and pyrimidines. The mass spectrometry imaging (MSI) methods described here can also be applied to the surface analysis of rock samples involved in other applications such as petroleum or environmental chemistries. PMID:25361668

Bennett, Rachel V; Fernndez, Facundo M

2015-01-01

412

Application of electron-stimulated desorption for studying adsorbed layers  

NASA Astrophysics Data System (ADS)

After a brief discussion of the main result of the research initiated by N.I. Ionov in his laboratory using electron-stimulated desorption for studying the surface layers of tungsten, we consider in greater detail recent results on layered coatings formed on the tungsten surface upon simultaneous adsorption of sodium (or cesium) and gold atoms on this surface, as well as the effect of sputtering of samarium atoms on the (Cs + Au)/W(100) surface that has already been formed at 300 K.

Ageev, V. N.; Kuznetsov, Yu. A.; Potekhina, N. D.

2013-06-01

413

ANALYSIS OF ESTUARINE TRACER-GAS TRANSPORT AND DESORPTION.  

USGS Publications Warehouse

The riverine tracer-gas technique provides a direct, reach-averaged measure of gas exchange, is fairly simple to implement, and is widely accepted for determining reaeration-rate coefficients in rivers. The method, however, is not directly applicable to flows having vertical density gradients. Consequently, studies were undertaken to develop and evaluate methods for obtaining surface-exchange coefficients from estuarine tracer-gas data. Reasonable estimates of the desorption coefficient (within 50 percent of the correct value) were obtained when an analytical solution of the transport equation was compared with data from a numerically simulated continuous release of tracer gas.

Bales, Jerad D.; Holley, Edward R.

1987-01-01

414

Evidence for a Surface Exciton in KBr via Laser Desorption  

SciTech Connect

We demonstrate that direct photoexcitation of the KBr surface exciton leads to desorption of hyperthermal neutral bromine atoms. We have for the first time produced separately the hyperthermal and the near-thermal components of neutral halogen emission from an alkali halide. The source of hyperthermal bromine emission is attributed to decay of a surface exciton excited at photon energies below that of the bulk exciton. We further demonstrate that the frequently observed near-thermal component is derived from excitation within the bulk crystal. Our experimental data provides strong support to a theoretical emission model previously described in the literature.

Beck, Kenneth M. (BATTELLE (PACIFIC NW LAB)); Joly, Alan G. (BATTELLE (PACIFIC NW LAB)); Hess, Wayne P. (BATTELLE (PACIFIC NW LAB))

2001-01-01

415

Evidence for a surface exciton in KBr via laser desorption  

SciTech Connect

We demonstrate that direct photoexcitation of the single crystal KBr surface leads to desorption of hyperthermal neutral bromine atoms. We have produced separately the hyperthermal and the near-thermal components of neutral halogen emission from an alkali halide. The source of hyperthermal bromine emission is attributed to decay of a surface exciton excited at photon energies below that of the bulk exciton. We argue that the frequently observed near-thermal component is derived from excitation within the bulk crystal. Our experimental data provide strong support to a theoretical excitonic emission model previously described in the literature.

Beck, Kenneth M.; Joly, Alan G.; Hess, Wayne P.

2001-03-15

416

A study of sorption\\/desorption and diffusion of substituted aromatic probe molecules into semi interpenetrating polymer network of polyurethane\\/polymethyl methacrylate  

Microsoft Academic Search

The sorptiondesorptionresorptionredesorption experiments have been conducted to evaluate the transport behaviour of polyethylene glycol (PEG) based polyurethane\\/polymethyl methacrylate (PU\\/PMMA, 50\\/50) semi interpenetrating polymer network (SIPN) with aromatic probe molecules. Molecular migration depends on the nature of the organic solvent, membranesolvent interaction, temperature, solubility parameter, molecular volume and free volume available within the polymer matrix. The transport parameters like sorption (S),

H. Kumar; Siddaramaiah

2005-01-01

417

Xenon and Krypton Adsorption on Palladium (100) and Electron Stimulated Desorption of Xenon, Krypton, and Argon.  

NASA Astrophysics Data System (ADS)

The adsorption of Xe and Kr on the Pd(100) surface has been studied with thermodynamic, low energy electron diffraction, and work function experiments. Unlike on Ag(111), we observe no 2D island formation for Xe down to 10K. Quantitative measurements of the liquid-like diffraction pattern show that the diffuse ring of intensity increases in diameter, narrows, and becomes more intense continuously with increasing coverage, suggesting repulsive adatom interactions. The isosteric heat vs. coverage gives the average potential energy in the lateral interactions which suggests a steep repulsion at short distances and no attractive well. At high temperatures the results for Kr are similar but there is evidence for island formation near 10K. The isosteric heat indicates a weak attractive interaction. The results are compared with published simulations for hard and soft disks. It is speculated that the additional interadatom repulsion on Pd is due to the direct overlap of the deformed electron distribution in the substrate. Electron stimulated desorption cross sections have been measured for Xe, Kr, and Ar adsorbed on Ag(111). The Xe cross section is less than 10('-4) (ANGSTROM)('2); the Kr cross section is strongly temperature dependent, rising from 0.01 (ANGSTROM)('2) at 10K to 0.18 (ANGSTROM)('2) at 50K; the Ar cross section is 4 (ANGSTROM)('2) and temperature independent. These results are rationalized using a model of the stimulated desorption similar to that proposed by Antoniewicz (Phys. Rev. B21(1980)3811), in which an atom is ionized by the incident beam, accelerates toward its image and is neutralized, desorbing only if the kinetic energy gained is greater than the neutral atom binding energy at the neutralization position. Rather than the effect of the mass on the ion velocity, the most important effect in determining the diverse behavior of the different gases is that the equilibrium position for the heavier gases is farther up the overlap repulsive potential and so in a region of more rapid neutralization. The model identifies several contributions to the isotope effect, predicting it to be temperature dependent. The results are extremely sensitive to the anharmonicity of the holding potential.

Moog, Elizabeth Rahm

1984-06-01

418

Prediction Computer Program for Whole Body Temperatures and its Application under Various Working Level and Thermal Environmental Condition Combinations  

Microsoft Academic Search

We introduced a computer program developed for the numerical analysis of thermal conditions of all segments and blood circulatory systems in the human body to precisely evaluate human thermal physiological responses. In this program, a cylindrical model consisting of internal multi-layers is adapted for the segment of the human body. For the multi-layered concentric cylindrical model we adopted a new

Shintaro YOKOYAMA; Michiyoshi TAO; Naoto KAKUTA

2007-01-01

419

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

420

Scanning electron-stimulated desorption microscopy of red blood cells.  

PubMed

Scanning electron-stimulated desorption (SESD) has been used to image the surface of unfixed red blood cells with high surface specificity and with a lateral spatial resolution of less than or equal to 1 micron. The micrographs were obtained using a scanning Auger microprobe with an appended secondary ion mass spectrometer (SIMS). The instrument was operated at low electron beam energies (2 kV) to maximize electron-stimulated desorption probabilities and minimize the interaction of the electrons with the biological substrate. ESD spectra from the surface of red blood cells prepared from smears of whole blood show H+ as the predominant desorbed positive ion and O+, OH+, H3O+, Na+, and Cl+ as secondary species. SESD images and line-scans obtained with the above ion signals demonstrate that SESD can be used to map the surface chemistry of cells at submicron resolution. The parent molecules contributing to the desorbed ion signals are shown to originate from the first few atomic layers of the cell surface and are believed to be components of the blood plasma (H2O, NaCl, etc.) which coalesced onto the cells as they dehydrated in the vacuum chamber of the microprobe. An interesting extension of this work is the possibility of mapping the concentration of adsorption sites of specific cell-surface binding species using ESD labels. PMID:6505612

Dylla, H F; Abrams, J H

1984-01-01