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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Investigations of the Fundamental Surface Reactions Involved in the Sorption and Desorption of Radionuclides

Models for describing solution- and surface-phase reactions have been used for 30 years, but only recently applicable to complex surfaces. Duff et al., using micro-XANES, found that Pu was concentrated on Mn-oxide and smectite phases of zeolitic tuff, providing an evaluation of contaminant speciation on surfaces for modeling. Experiments at Los Alamos demonstrated that actinides display varying surface residence time distributions, probably reflective of mineral surface heterogeneity. We propose to investigate the sorption/desorption behavior of radionuclides from mineral surfaces, as effected by microorganisms, employing isolates from Nevada Test Site deep alluvium as a model system. Characterizations will include surface area, particle size distribution, x-ray diffraction (XRD), microprobe analysis, extractions, and microbiology. Surface interactions will be assessed by electron spectroscopy (XPS), x-ray absorption fine structure spectroscopy (XAFS), X-ray emission spectroscopy, transmission electron microscopy (TEM) and Scanning electron microscopy (SEM). Desert Research Institute (DRI), University of Nevada, Reno (UNR), and University of Nevada, Las Vegas (UNLV) researchers will collaborate to enhance scientific infrastructure and the understanding of contaminant behavior on surfaces, with broader implications for the management of DOE sites.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2019

Internal Energy Distribution of Secondary Ions Under Argon and Bismuth Cluster Bombardments: “Soft” Versus “Hard” Desorption–Ionization Process

The emission/ionization process under massive argon cluster bombardment was investigated by measuring the internal energy distributions of a series of benzylpyridinium ions. Argon clusters with kinetic energies between 10 and 20 keV and cluster sizes ranging from 500 to 10,000 were used to establish the influence of their size, energy, and velocity on the internal energy distribution of the secondary ions. It is shown that the internal energy distribution of secondary ions principally depends on the energy per atom or the velocity of the cluster ion beam (E/n ∝ v{sup 2}). Under low energy per atom (E/n ˂ 10 eV), the mean internal energy and fragmentation yield increase rapidly with the incident energy of individual constituents. Beyond 10 eV/atom impact (up to 40 eV/atom), the internal energy reaches a plateau and remains constant. Results were compared with those generated from bismuth cluster impacts for which the mean internal energies correspond well to the plateau values for argon clusters. However, a significant difference was found between argon and bismuth clusters concerning the damage or disappearance cross section. A 20 times smaller disappearance cross section was measured under 20 keV Ar{sub 2000}{sup +} impact compared to 25 keV Bi{sub 5}{sup +} bombardment, thus quantitatively showing the low damage effect of large argon clusters for almost the same molecular ion yield. .

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Sorption and desorption properties of a CaH{sub 2}/MgB{sub 2}/CaF{sub 2} reactive hydride composite as potential hydrogen storage material

The hydrogenation behavior of 3CaH{sub 2}+4MgB{sub 2}+CaF{sub 2} composite was studied by manometric measurements, powder X-ray diffraction, differential scanning calorimetry and attenuated total reflection infrared spectroscopy. The maximum observed quantity of hydrogen loaded in the composite was 7.0 wt%. X-ray diffraction showed the formation of Ca(BH{sub 4}){sub 2} and MgH{sub 2} after hydrogenation. The activation energy for the dehydrogenation reaction was evaluated by DSC measurements and turns out to be 162{+-}15 kJ mol{sup -1} H{sub 2}. This value decreases due to cycling to 116{+-}5 kJ mol{sup -1} H{sub 2} for the third dehydrogenation step. A decrease of ca. 25-50 deg. C in dehydrogenation temperature was observed with cycling. Due to its high capacity and reversibility, this composite is a promising candidate as a potential hydrogen storage material. - Graphical abstract: PCI of 3CaH{sub 2}+4MgB{sub 2}+CaF{sub 2} reactive hydride composite at 325 deg. C and 350 deg. C. Open marks: dehydrogenation, closed marks: hydrogenation. Highlights: > The hydrogenation and dehydrogenation behavior of CaF{sub 2} doped CaH{sub 2}/MgB{sub 2} RHC is presented. > The new composite presents a superior hydrogen uptake compared with the non-doped composite.. > A reduction in the E{sub a} and the dehydrogenation temperature was observed by CaF{sub 2} doping and cycling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

O({sup 3}P{sub J}) formation and desorption by 157-nm photoirradiation of amorphous solid water

Photodissociation of amorphous solid water (ASW) deposited on a thinly oxidized copper substrate at 82 K was studied by measuring O({sup 3}P{sub J=2,1,0}) photoproducts detected with resonance-enhanced multiphoton ionization. For each spin-orbit state, the oxygen atom time-of-flight spectrum was measured as a function of H{sub 2}O exposure, which is related to ice thickness, and 157-nm irradiation time. Four Maxwell-Boltzmann distributions with translational temperatures of 10 000 K, 1800 K, 400 K, and 82 K were found to fit the data. The most likely formation mechanisms are molecular elimination following ionization of water and ion-electron recombination, secondary recombination of hydroxyl radicals, and photodissociation of adsorbed hydroxyl radicals. Evidence for O-atom diffusion through bulk ASW was found for H{sub 2}O exposures of at least 5 Langmuir (1 L = 10{sup −6} Torr s). The cross sections for O({sup 3}P{sub 2}) depletion were 1.3 × 10{sup −19} and 6.5 × 10{sup −20} cm{sup 2} for 1 and 5 L, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

BLISTERING AND EXPLOSIVE DESORPTION OF IRRADIATED AMMONIA-WATER MIXTURES

We present laboratory studies on the thermal evolution of a solid ammonia-water mixture after it has been irradiated at 20, 70, and 120 K. In samples irradiated at {<=}70 K, we observed fast outbursts that appear to indicate grain ejection and correlate well with the formation of micron-sized scattering centers. The occurrence of this phenomenon at the lower irradiation temperatures indicates that our results may be most relevant for understanding the release of gas and grains by comets and the surfaces of some of the colder icy satellites. We observe outgassing at temperatures below those where ice sublimates, which suggests that comets containing radiolyzed material may have outbursts farther from the Sun that those that are passive. In addition, the estimated size of the grains ejected from our sample is on the order of the size of E-ring particles, suggesting that our results give a plausible mechanism for how micron-sized grains could be formed from an icy surface. Finally, we propose that the presence of the {approx}4.5 {mu}m N{sub 2}O absorption band on an icy surface in outer space will serve to provide indirect evidence for radiation-processed ices that originally contained ammonia or nitrogen, which could be particularly useful since nitrogen is such a weak absorber in the infrared and ammonia is rapidly decomposed by radiolysis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Rare Earth Adsorption and Desorption with PEGDA Beads

We synthesized PEGDA polymer hydrogel beads for cell embedding and compared REE biosorption with these beads via a gravity-driven flow through setup. One way to set up a flow through system is by cell encapsulation into polymer beads with a column setup similar to that used in the chromatography industry. To achieve this, we tested PEGDA for cell encapsulation, and tested REE biosorption under both batch mode and a follow through setup based on gravity . For making the cell embedded polymer beads, we used a fluidic device by which homogenous spherical particles of 0.5 to1 mm in diameter were synthesized. The beads are made relatively quickly, and the size of the beads can be controlled. PEGDA beads were polymerized by UV. Tb adsorption experiment was performed with beads with or without cells embedded.

15 GEOTHERMAL ENERGY↗
DOE OSTI2012

Effects and Mechanisms of Mechanical Activation on Hydrogen Sorption/ Desorption of Nanoscale Lithium Nitrides

The objective of this project is to investigate and develop novel, mechanically activated, nanoscale Li 3 N-based and LiBH 4 -based materials that are able to store and release ~10 wt% hydrogen at temperatures near 100°C with a plateau hydrogen pressure of less than 10 bar. Four (4) material systems have been investigated in the course of this project in order to achieve the project objective. These 4 systems are (i) LiNH 2 +LiH, (ii) LiNH 2 +MgH 2 , (iii) LiBH 4 , and (iv) LiBH 4 +MgH 2 .

08 HYDROGEN↗
DOE OSTI2015

Investigations into Alternative Desorption Agents for Amidoxime-Based Polymeric Uranium Adsorbents

Amidoxime-based polymeric braid adsorbents that can extract uranium (U) from seawater are being developed to provide a sustainable supply of fuel for nuclear reactors. A critical step in the development of the technology is to develop elution procedures to selectively remove U from the adsorbents and to do so in a manner that allows the adsorbent material to be reused. This study investigates use of high concentrations of bicarbonate along with targeted chelating agents as an alternative means to the mild acid elution procedures currently in use for selectively eluting uranium from amidoxime-based polymeric adsorbents.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2011

Desorption Induced Formation of Negative Nanowires in GaN

We report in-situ transmission electron microscopy studies of the formation of negative nanowires created by thermal decomposition of single crystal GaN. During annealing, vertical negative nanowires are formed in [0 0 0 1] by preferential dissociation of GaN along the 1 0 {bar 1} 0 prism planes, while lateral negative nanowires grow in close-packed 1 0 {bar 1} 0 by the self-catalytic solid-liquid-vapor (SLV) mechanism. Our quantitative measurements show that the growth rates of the laterally grown negative nanowires are independent of the wire diameter, indicating that the rate-limiting step is the decomposition of GaN on the surface of the Ga droplets that catalyze their creation. These nanoscale features offer controllable templates for the creation and integration of a broad range of nanoscale materials systems, with potential applications in nanoscale fluidics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗