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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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DOE OSTI2024

Adsorption of Ag, Au, Cu, and Ni on MoS 2 : theory and experiment

Abstract Here, we present results of a computational and experimental study of adsorption of various metals on MoS2. In particular, we analyzed the binding mechanism of four metallic elements (Ag, Au, Cu, Ni) on MoS2. Among these elements, Ni exhibits the strongest binding and lowest mobility on the surface of MoS2. On the other hand, Au and Ag bond very weakly to the surface and have very high mobilities. Our calculations for Cu show that its bonding and surface mobility are between these two groups. Experimentally, Ni films exhibit a composition characterized by randomly oriented nanoscale clusters. This is consistent with the larger cohesive energy of Ni atoms as compared with their binding energy with MoS2, which is expected to result in 3D clusters. In contrast, Au and Ag tend to form atomically flat plateaued structures on MoS2, which is contrary to their larger cohesive energy as compared to their weak binding with MoS2. Cu displays a surface morphology somewhat similar to Ni, featuring larger nanoscale clusters. However, unlike Ni, in many cases Cu exhibits small plateaued surfaces on these clusters. This suggests that Cu likely has two competing mechanisms that cause it to span the behaviors seen in the Ni and Au/Ag film morphologies. These results indicate that calculations of the initial binding conditions could be useful for predicting film morphologies. In addition, out calculations show that the adsorption of adatoms with odd electron number like Ag, Au, and Cu results in 100% spin-polarization and integer magnetic moment of the system. Adsorption of Ni adatoms, with even electron number, does not induce a magnetic transition.

Harms, Haley↗
DOE OSTI2022

Low-redshift quasars in the SDSS Stripe 82 – III. MOS observations

ABSTRACT We present multi-object optical spectroscopy of the galaxies in the environment of 12 low-redshift (z < 0.5) quasars and of 11 inactive massive galaxies chosen to match the properties of the quasar host galaxies to probe physical association and possible events of recent star formation (SF). The quasars are selected from a sample of QSOs in the Sloan Digital Sky Survey (SDSS) Stripe 82 region for which both the host galaxy and the large-scale environments were previously investigated. The new observations complement those reported in our previous works on close companion galaxies of nearby quasars. For the whole data set, we find that for about half (19 out of 44) of the observed QSOs, there is at least one associated companion galaxy. In addition to the new spectroscopic observations, we add data from the SDSS data base for the full sample of objects. We find that the incidence of companion galaxies in the fields of QSO (17 per cent) is not significantly different from that of inactive galaxies (19 per cent) similar to quasar hosts in redshift and mass. Nevertheless, the companions of quasars exhibit more frequently emission lines than those of inactive galaxies, suggesting a moderate link between the nuclear activity and recent SF in their environments.

Astronomy & Astrophysics↗
DOE OSTI2022

Quality Control Metrics to Assess MoS 2 Sputtered Films for Tribological Applications [Slides]

Easily measured metrics that could assign quantifiable values to coating batches for quality control have started to be developed. High-density is an attribute of quality films. Increased density results in harder, more wear resistant coatings in inert and humid environments. Denser films are more resistant to oxidation from aging, limiting the severity and depth of oxide into the coating. Future work includes using metrics for quality. The next step is to develop in house deposition capabilities to develop process-structure relationships.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗