Presence Of Deuterium Research Articles

Early deuteration steps of Pd- and Ta/Pd- catalyzed Mg 70Al 30 thin films observed at room temperature

Deuterium absorption in Mg 70Al 30 thin films coated with a Pd layer and a Ta/Pd bilayer were investigated using in situ neutron reflectometry at room temperature and deuterium pressures up to 1.3 bar. The approach used provides a detailed profile, at the nanoscale, of the deuterium content inside the specific layers that constitute the films. It is found that Mg 70Al 30 can store up to 5 wt.% under these mild conditions following a two-step mechanism. The latter involves the deuteration of the top and bottom catalyst layers first, followed by the main Mg 70Al 30 layer. The presence of deuterium throughout the films in the early absorption stages evidences atomic deuterium spillover from the catalyst layers. The addition of a Ta layer between the Pd and Mg 70Al 30 was found to allow observable absorption at a pressure 10 times lower than on the Ta-free sample, without affecting the storage capacity. Our measurements imply that this improvement in kinetics is due to a lowering of the nucleation barrier for the formation of the hydride phase in the Mg 70Al 30 layer.

Laser-induced removal of co-deposits from graphitic plasma-facing components: Characterization of irradiated surfaces and dust particles

Laser-induced fuel desorption and ablation of co-deposited layers on limiter plates from the TEXTOR tokamak have been studied. Gas phase composition was monitored in situ, whereas the ex situ studies have been focused on the examination of irradiated surfaces and broad analysis of dust generated by ablation of co-deposits. The size of the dust grains is in the range of few nanometers to hundreds of micrometers. These are fuel-rich dust particles, as determined by nuclear reaction analysis. The presence of deuterium in dust indicates that not all fuel species are transferred to the gas phase during irradiation. This also suggests that photonic removal of fuel and the ablation of co-deposit from plasma-facing components may lead to the redistribution of fuel-containing dust to surrounding areas.

Effect of adsorbed hydrogen on the stability of titanium atoms on aluminum surfaces

The thermal stability of Ti atoms evaporated onto polycrystalline Al and Al(100) surfaces was studied using ion scattering spectroscopy. Measurements were made in vacuum and in the presence of deuterium. When heated in vacuum, Ti begins to disappear from the surface at substrate temperatures below $100\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ and is not detected on the surface at temperatures above $250\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$. When measurements are made while the sample is being exposed to atomic D, Ti persists on the surface to noticeably higher temperatures. Diffusion coefficients for surface Ti moving into the Al substrate were obtained at temperatures in the range $25--150\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$. The experimental results are compared to density-functional theory calculations, which indicate that direct and Al mediated H-Ti interactions stabilize surface Ti. At H coverages around 1 ML (monolayer), the most stable structure has 1/2 ML Ti in the second layer and 1 ML H on specific bridge sites on the top Al layer. Ti directly exposed to the surface is less stable and thus likely to be less active for Ti catalysis of H sorption in alanate H storage materials.

10.1007/s11700-008-1011-3

The results of neutron diffraction microstructure investigation of a eutectic lead-potassium melt bubbled with heavy water are presented. The structure factors and pair correlation functions for pure eutectic and eutectic bubbled with heavy water are compared. Evidence of the presence of deuterium in the latter melt has been shown in the diffraction pattern.

Impact of high-pressure deuterium oxide annealing on the blocking efficiency and interface quality of metal-alumina-nitride-oxide-silicon-type flash memory devices

We have investigated the effect of high-pressure deuterium oxide annealing (HPDOA) on metal-alumina-nitride-oxide-silicon-type flash memory device. HPDOA was performed in a high-pressure wet vapor ambient (N2:D2O=10atm:2atm) at 250°C for 5min. HPDOA devices achieved the improvements of blocking oxide quality as well as tunneling oxide/Si interface quality. The improvement of blocking oxide induced the lower charge loss through the blocking oxide, lower leakage current density, lower erase saturation level, and a larger memory window after the program/erase cycles. In addition, the presence of deuterium at the tunneling oxide/Si improved the interface quality by the formation of Si–D bonds.

Clusters and gigantic heterophase water clusters

We have analyzed the concept of gigantic heterophase water clusters (GHWC) in connection with the data available in the literature on various mechanisms of the formation of clusters in water. We have made conclusions on the fact that the GHWC composition may include water clusters of small sizes, while the presence of deuterium in the water in the form of HDP may play a significant role in the formation and stabilization of GHWC.

Organics Captured from Comet 81P/Wild 2 by the Stardust Spacecraft

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

The Impact of Deuterated CMOS Processing on Gate Oxide Reliability

In recent literature, a controversy has arisen over the question whether deuterium improves the stability of the MOS gate dielectric. In particular, the influence of deuterium incorporation on the bulk oxide quality is not clear. In this letter, deuterium or hydrogen is introduced during either the gate oxidation, postoxidation anneal, and/or the postmetal anneal (PMA). The oxide bulk degradation was evaluated using charge-to-breakdown and stress-induced leakage current; and the oxide interface degradation using hot-carrier degradation and low-frequency noise. The obtained results show that the oxide bulk does not benefit from the presence of deuterium, regardless of the stage of deuterium introduction, or the gate oxide thickness. The oxide interface is more stable only when deuterium is introduced in the PMA.

Synchrotron topographic and photoluminescence investigations of porous layer in HT‐HP treated silicon implanted with deuterium ions

The 001 oriented Cz-Si samples were implanted at room temperature with 200 keV deuterium ions to the dose 1.7 × 1017 cm–2 and treated at up to 950 °C under hydrostatic Ar pressure (HP) up to 11 kbar for up to 10 h. The sample properties were studied by means of monochromatic synchrotron X-ray diffraction topography as well as by rocking curve (RC) and photoluminescence (PL) measurements. The thermal annealing caused rapid disappearance of interference effects in RCs and topographs. This process was significantly moderated by HP providing the layers with spongy like structure owing the presence of deuterium - filled inclusions. In the last case the most significant contribution of the PL peaks attributed to dislocations was observed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Fusion and nucleosynthesis by hypervelocity impact using hybrid magnetic fields

The electromagnetic acceleration of a metallic ring carrying a high current, combined with the mutual interaction of a concentrical conductor carrying the same current, in the presence of a DC magnetic field, results in a converging beam of particles reaching a velocity above 1000 km/s. Lithium, gold, and uranium rings are considered and transient temperatures ranging from 108to 1010°K are expected. In the presence of deuterium and tritium fusion reactions will occur and the capture of the released neutrons may result in the synthesis of heavier elements. The considered device lends itself to a varied treatment allowing to consider velocities in the range of 2000 km/s.

Probing the Structure of the Infectious Amyloid Form of the Prion-forming Domain of HET-s Using High Resolution Hydrogen/Deuterium Exchange Monitored by Mass Spectrometry

The HET-s prion protein of Podospora anserina represents a valuable model system to study the structural basis of prion propagation. In this system, prion infectivity can be generated in vitro from a recombinant protein. We have previously identified the region of the HET-s protein involved in amyloid formation and prion propagation. Herein, we show that a recombinant peptide corresponding to the C-terminal prion-forming domain of HET-s (residues 218-289) displays infectivity. We used high resolution hydrogen/deuterium exchange analyzed by mass spectrometry to gain insight into the structural organization of this infectious amyloid form of the HET-s-(218-289) protein. Deuterium incorporation was analyzed by ion trap mass spectrometry for 76 peptides generated by pepsin proteolysis of HET-s-(218-289). By taking into account sequence overlaps in these peptides, a resolution ranging from 4-amino acids stretches to a single residue could be achieved. This approach allowed us to define highly protected regions alternating with more accessible segments along the HET-s-(218-289) sequence. The HET-s-(218-289) fibrils are thus likely to be organized as a succession of beta-sheet segments interrupted by short turns or short loops.

Rosseland and Planck mean opacities for primordial matter

We present newly calculated low-temperature opacities for gas with a primordial chemical composition. In contrast to earlier calculations which took a pure metal-free Hydrogen/Helium mixture, we take into account the small fractions of Deuterium and Lithium as resulting from Standard Big Bang Nucleosynthesis. Our opacity tables cover the density range -16 10^3 K. We find that, while the presence of Deuterium does not significantly alter the opacity values, the presence of Lithium gives rise to major modifications of the opacities, at some points increasing it by approximately 2 orders of magnitude relative to pure Hydrogen/Helium opacities.

Infrared Absorption Spectra of Deuterated Amorphous Carbon

We report infrared absorption spectra of hydrogenated amorphous carbon (HAC) deposits prepared in the presence of deuterium. Spectra of D:HAC and DAC are characterized by the appearance of additional features near 2175 cm-1 (4.6 μm) corresponding to stretching vibrations of CDn groups. These are accompanied by a weakening of absorption in the CHn absorption bands throughout the infrared. Laboratory data suggest that it may be possible to detect deuterium fractionations XD/H ≥ 7.4 × 10-3 in carbonaceous dust along the line of sight to Galactic center sources via absorption within the CDn stretching band near 4.6 μm.

Comparison between pure and deuterated potassium acid phthalate (DKAP) single crystals

Single crystals of pure and deuterated potassium acid phthalate (DKAP) have been grown from aqueous solution by slow cooling method. The effect of deuterium on morphology and crystal properties has been studied. Powder X-ray diffraction analysis confirms the structure and changes in lattice parameter values for the deuterated crystals. The presence of deuterium in the crystal lattice has been confirmed by FTIR analysis. The DKAP crystals possess relatively lower hardness values than the pure crystals. The transmittance of DKAP is found to be higher than KAP crystals.

The interaction of deuterium and tritium with radiation and other defects in austenitic steel and nickel

The methods of residual resistivity, annihilation of positrons, and nuclear reactions in nickel and austenitic steels were used to examine the interaction of deuterium and tritium with defects produced by electron- neutron- or ion-irradiation and plastic deformation. It was found that vacancies, dislocations and three-dimensional vacancy clusters captured hydrogen in nickel. Vacancy clusters were formed in the presence of deuterium and tritium at room temperature, when single vacancies were immobile. The type of the hydrogen isotope determined configurations of those clusters. Hydrogen atoms interacted with interstitial atoms at 150 K in nickel and at 220 K in steel. Deuterium segregation occurred both in nickel and austenitic steel under irradiation with deuterium ions, but the segregation exhibited a different behavior. A possible scheme of formation and evolution of deuterium segregation in the studied materials was proposed.

Methyl Side Chain Formation on the CrCp2/SiO2 Catalyst during Polymerisation of Ethylene: Spectroscopic Analyses and Theoretical Modelling

Polymerisations at different ethylene pressures and temperatures in the presence of deuterium as a chain transfer agent have been performed with a CrCp2/SiO2 catalyst. The polymers formed have been analysed by 1H, 2H, and 13C NMR spectroscopy. The results from the NMR analyses, DRIFTS analysis of the catalyst in the presence of ethylene, and theoretical modelling (DFT) have been used to investigate the mechanism for methyl branch formation. Indirect evidence for the presence of an isomerised chromium site has been found, where the chromium is bonded to a secondary carbon atom within the polymer chain. The DFT calculations indicate an energy barrier of 17 kcal/mol for the isomerisation, where a hydrogen atom is transferred from the α-carbon to the β-carbon through an olefin–chromium–hydrid intermediate. Propagation from the isomerised site gives a methyl branch. Ethyl branches are also observed, which may be explained by repeated isomerisation. The energy barrier for propagation from the isomerised site is significantly higher than for the regular site where chromium is bonded to the chain end, with barriers of 12 and 8 kcal/mol, respectively. The results support a model in which the observed strong pressure dependence of the activity on the partial pressure of ethylene is due to a higher rate of isomerisation than propagation from this site at low ethylene pressures.

Ethylene polymerization reactions with Ziegler-Natta catalysts. II. Ethylene polymerization reactions in the presence of deuterium

Ethylene polymerization reactions with many Ziegler–Natta catalysts exhibit several features which differentiate them from polymerization reactions of α-olefins: a relatively low ethylene reactivity, higher polymerization rates in the presence of α-olefins, a high reaction order with respect to ethylene concentration, and strong reversible rate depression in the presence of hydrogen. A detailed kinetic analysis of ethylene polymerization reactions (see ref. 1) provided the basis for a new reaction scheme which explains all these features by postulating the equilibrium formation of a TiC2H5 species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center. This mechanism predicts that the β-agostically stabilized TiC2H5 groups can decompose in the β-hydride elimination reaction with expulsion of ethylene and the formation of a TiH bond even in the absence of hydrogen in the reaction medium. If D2 is used as a chain transfer agent instead of H2, the mechanism predicts the formation of deuterated ethylene molecules, which copolymerize with protioethylene. To prove this prediction, several ethylene homopolymerization reactions were carried out with a supported Ziegler–Natta titanium-based catalyst in the presence of large amounts of D2. Analysis of gaseous reaction products and polymers confirmed the formation of several types of deuterated ethylene molecules and protio/deuterioethylene copolymers, respectively. In contrast, a metallocene catalyst, Cp2ZrCl2MAO, does not exhibit these kinetic features. In the presence of deuterium, it produces only DCH2CH2(CH2CH2)xCH2CH2D molecules. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4273–4280, 1999

Ethylene polymerization reactions with Ziegler–Natta catalysts. II. Ethylene polymerization reactions in the presence of deuterium

Ethylene polymerization reactions with Ziegler–Natta catalysts. II. Ethylene polymerization reactions in the presence of deuterium

Synthesis of deuterium- and tritium-labeled 25,26,26,26,27,27,27-heptafluorocholesterol

25,26,26,26,27,27,27-Heptafluorocholesterol (F7-cholesterol) is a novel analog of cholesterol with potential value in biological investigations. We have combined an isotope-labeling strategy described for 15-ketosterols with modifications in the original synthesis of F7-cholesterol to prepare analogs containing deuterium or tritium at the C-23 position. 1H, 2H, and 13C nuclear magnetic resonance spectra indicated high chemical purity of the deuterium-labeled analog and confirmed the presence of deuterium only at C-23. The tritium-labeled analog was synthesized in high radiochemical purity with a specific activity of 472 mCi/mmol. Copyright © 1999 John Wiley & Sons, Ltd.

The mechanism of hydrogenolysis and isomerization of oxacycloalkanes on metals: XV. Transformation of ethyl- and vinyloxirane on Cu–SiO 2

The isomerization and hydrogenolysis of vinyloxirane and, for comparison, those of ethyloxirane were studied on a Cu–SiO 2 catalyst at 373 K in a recirculation reactor, at various hydrogen pressures and in the presence of deuterium. It was established that in the case of ethyloxirane, the dominating reactions are deoxygenation associated with the formation of 1-butene and isomerization resulting in the formation of butanal. In the case of vinyloxirane, the enlargement of the oxirane ring to a five-membered ring also takes place in addition to deoxygenation and isomerization. Olefins are formed on Cu(0) while isomerization occurs on copper–copper oxide interfaces. The experimental results allow the identification of the probable reaction pathways leading to the formation of the individual products.