Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “functioning”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

Complex oxides exhibit a wide range of crystal structures, chemical compositions and physical properties. The underlying drivers determining the complicated structure-composition-property phase diagrams are the relative positions and orbital overlaps between the metal cations and the oxygen anions. Here we report a combined experimental and theoretical investigation of the structure and bonding in a series of lanthanum chromium oxides prepared by reactive molecular beam epitaxy. Of particular interest is the charge state and local coordination of the Cr. We have stabilized LaCrO 3 , LaCrO 4 and La 2 CrO 6 films by controlling the three elemental fluxes during deposition, and have carried out x-ray diffraction, x-ray photoemission, and x-ray absorption spectroscopy, as well as first-principles calculations, to determine structure, charge state, chemical bonding, and electronic structure. Significant changes in bonding character and orbital interaction are revealed with decreasing ligand symmetry from octahedral to tetrahedral Cr coordination. Both LaCrO 4 and LaCrO 6 with tetrahedrally coordinated Cr show strong pre-edge features in the Cr K-edge near-edge structure whereas LaCrO 3 with octahedrally coordinated Cr exhibits very weak pre-edge features. The origin of these pre-edge features is discussed based on various selection rules and ligand symmetry. We also demonstrate an increase in cation-anion orbital hybridization and a decrease in long-range ligand coupling induced by this symmetry reduction. These in turn result in dramatic modifications of the macroscopic optical and magnetic properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Dual Functional Star Polymers for Lubricants

Star-shaped poly(alkyl methacrylate)s (PAMAs) with a 3-arm architecture were designed, prepared and their performance as a dual additive (viscosity index improver and friction modifier) for engine oils was evaluated. Furthermore, the structure-property relationships between macromolecular structure and lubricant performance were studied. Several co-polymers of dodecylmethacrylate with polar methacrylates in various amounts and various topologies, were synthesized as model compounds. Star polymers with a polar content of at least 10% effectively reduced the friction coefficient in both mixed and boundary lubrication regime only in block or tapered block topology. However, a polar content of 20% was efficient in reducing friction in both random and block topologies.

Cosimbescu, Lelia↗
DOE OSTI2017

Flexible monomer-based covalent organic frameworks: design, structure and functions

The design and synthesis of flexible monomer-based covalent organic frameworks (COFs) have been considered a challenge. We describe the design and synthesis of a new flexible monomer-based COF, termed PPN-30 (PPN meaning porous polymer network), by the use of a flexible alkyl amine, 1,4-cyclohexanediamine, combined with 1,3,5-triformylbenzene. The structure and gas adsorption properties of PPN-30 were carefully investigated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Design of functional composite and all-inorganic nanostructured materials via infiltration of polymer templates with inorganic precursors

Robust and efficient approaches for the synthesis of materials with structure, porosity, and composition controlled at the nanoscale are highly important for a wide range of applications. Polymer templates are promising platforms to achieve such control. The self-assembly process of polymers provides access to diverse structures that can serve as templates for the deposition of inorganic materials. By infiltrating metal precursors from gas or liquid phases, using sequential infiltration synthesis (SIS) or swelling-based infiltration (SBI), respectively, into the polymer templates, one can create finely-tuned texturing of the surface films and bulk materials. In this review, we outline the specifics and dynamics of the polymer infiltration process and characterize the structure and properties of the synthesized materials. Finally, we highlight recent progress in implementing polymer infiltration-based nanoporous ceramics for many applications, including sensors, antireflective coatings, oil-absorbing foams, nanolithographic patterns, and catalytic materials.

Berman, Diana↗