ORNL Highlights

1-10 of 206 Results

Importance of diminished local structural distortions and magnetism in causing iron-based superconductivity
— By analyzing the role of structural variation and magnetism of Cu dopants in FeAs planes, researchers demonstrated that orthorhombic distortions that give strong spin-density-wave spin (SDW) fluctuations are detrimental to superconductivity in BaFe2As2. The results provide new information about the interplay between local composition, magnetism and superconductivity.

Metallic Glasses: Different Deformation Properties Underpinned by the Same Trigger
— A novel simulation approach demonstrates that a universal deformation trigger exists in metallic glasses and that the spatial organization of these triggers is closely related to the dynamics and stabilities of the system. This work demonstrates that a universal trigger initiates deformation and the organization of such triggers significantly affects bulk behavior.

Laser speckle analysis resolves mesoscale transitions
— An elegant experimental approach, which requires only simple and widely available equipment, provides previously inaccessible spatial and temporal resolution on coexisting electronic domains in a technologically promising transition-metal oxide.

Creating and Activating a Terahertz Nanorotor in Graphene
— Replacing a hexagonal ring of carbon atoms in a graphene layer with a silicon trimer results in a terahertz rotor (1012 rotations/sec) with low friction. This demonstrates that the ultimate miniaturization of a mechanical device (switch, oscillator, stirrer) down to a triangular arrangement of three atoms is possible.

Double-Magic Nature of 132Sn and 208Pb

Reference: Phys. Rev. Lett.

Chemical and Morphological Changes of High Voltage Lithium-Manganese Rich Cathodes with Cycling
— Researchers used full-field transmission X-ray microscopy (TXM), capable of 3D imaging at high spatial resolution over a field of view of about 30×30×30 μm, to study the mechanisms driving structural degradation and voltage fade in a high capacity cathode material with nominal composition Li1.2Mn0.525Ni0.175Co0.1O2.

Direct observation of ferroelectric field effect and oxygen vacancy screening at ferroelectric–metal interface
— Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) studies of ferroelectric–metal interfaces revealed two distinct polarization charge screening mechanisms, with oxygen vacancies compensating negative charge and electrons compensating positive charge.

Magnetic fluctuations are good for superconductivity
— Atomic scale measurements of the strength of the magnetic fluctuations in a series of iron-based superconductors were made using high- resolution electron spectroscopy. Surprisingly, the superconducting transition temperature was higher when the magnitude of the fluctuating iron magnetic moment or “spin” was larger.

Thermopower Enhancement in Designer Oxide Superlattices
— A layer-by-layer design of 2D oxide superlattices with precisely controlled interface compositions has improved the thermopower of oxide thermoelectrics by 300% compared to that of bulk counterparts. Controlling the 2D carrier density through a new materials design strategy is critical for developing highly efficient thermoelectrics.

Structure-dependent Properties Guide Catalyst Design for Oxygenates Conversion
— The catalytic transformation of oxygenates (i.e. aldehydes, alcohols, ketones) on metal oxides to generate value added products such as fuels and additives is of great importance industrially, yet is not well-understood. ORNL researchers have provided new insights into how oxygenates react on metal oxide particles with well-defined structures.

 
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