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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Atomic layer deposition of ZnO on Cu-nanoclusters for methanol synthesis

The properties of ALD-grown ZnO thin films on Cu clusters supported on ZnO(1010) have been studied with scanning tunneling and scanning electron microscopy in combination with angle-resolved x-ray photoelectron spectroscopy. Deposition at room temperature of two monolayers of Cu on ZnO(1010) results in metallic Cu{sup 0} clusters {approx}8 nm wide by 1.4 nm high. Higher coverages of 15 ML results in a similar morphology, with slightly larger cluster sizes. Following air-exposure and ALD-growth of two cycles of ZnO, the Cu exhibits Cu{sup +} species characteristic of Cu{sub 2}O and the thin ZnO coating is hydroxylated. Electrochemical studies of ALD ZnO coatings on Cu suggest that they are more active for CO{sub 2} reduction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Antithermal mobility in Σ7 and Σ9 grain boundaries caused by stick-slip stagnation of ordered atomic motions about Coincidence Site Lattice atoms

Antithermal grain boundary migration is an interesting phenomenon that has been recently discovered. These grain boundaries behave opposite to what is expected of thermally activated grain boundary migration; the antithermal grain boundaries exhibit mobility that decreases with increasing temperature. Two recent studies have provided insight into important behaviors correlated with antithermal migration. O'Brien and Foiles (J Mater. Sci. Vol. 51, p. 6607–6623, 2016) demonstrated that the high mobility exhibited by an antithermal Σ7 grain boundary is enabled by ordered atomic motions. Ulomek and Mohles (Acta Mater. Vol. 103, p. 424–432, 2016) demonstrated that the thermal migration of a different Σ7 grain boundary exhibited a two-step migration process. In this work, we demonstrate that the antithermal temperature dependence exhibited by these types of grain boundaries is caused by a combination of these two discoveries. Specifically, ordered atomic motions about Coincidence Site Lattice atoms (atoms common to the lattices on either side of the grain boundary), seen by O'Brien and Foiles, are interrupted by additional thermal energy at higher temperature. This is the source of the two-step process seen by Ulomek and Mohles. This two-step process is akin to stick-slip behaviors observed in shear coupled grain boundary migration. As temperature is increased, the duration of the stagnant portion increases and the mobility decreases. This behavior is demonstrated through molecular dynamics simulations in nickel bicrystals over temperatures ranging from 100 to 1400 K for Σ7 and Σ9 grain boundaries. For these Σ7 and Σ9 grain boundaries, those that have ordered atomic mechanisms are almost exclusively antithermal, while those that do not have ordered atomic mechanisms are thermally activated.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Equilibrium vortex lattices of a binary rotating atomic Bose–Einstein condensate with unequal atomic masses

We perform a detailed numerical study of the equilibrium ground-state structures of a binary rotating Bose–Einstein condensate with unequal atomic masses. Our results show that the ground-state distribution and its related vortex configurations are complex events that differ markedly depending strongly on the strength of rotation frequency, as well as on the ratio of atomic masses. We also discuss the structures and radii of the clouds, the number and the size of the core region of the vortices, as a function of the rotation frequency, and of the ratio of atomic masses, and the analytical results agree well with our numerical simulations. This work may open an alternate way in the quantum control of the binary rotating quantum gases with unequal atomic masses. - Highlights: • A binary quantum gases with unequal atomic masses is considered. • Effects of the ratio of atomic masses and rotation frequency are discussed in full parameter space. • The detailed information about both the cloud and vortices are also discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗