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[Image above] Credit: NIST

From metal to insulator and back again

New work from Carnegie Institution hones in on the physics underlying the recently discovered fact that some metals stop being metallic under pressure and instead become insulating. The onsets of these transitions can be determined by the positions of electrons within the basic structure of the material. Insulators typically become metallic by a reduction in the spacing between atoms in the material. For a metal to become an insulator, these reduced-spacing overlaps must be organized in a specific kind of asymmetry that was not previously recognized.

Huge reduction of heat conduction observed in flat silicon channels

Combining state-of-the-art realistic atomistic modeling and experiments, a new paper describes how thermal conductivity of ultrathin silicon membranes is controlled to large extent by the structure and the chemical composition of their surface. A detailed understanding of the connections of fabrication and processing to structural and thermal properties of low-dimensional nanostructures is essential to design materials and devices for phononics, nanoscale thermal management, and thermoelectric applications.

Electron spin brings order to high entropy alloys

Researchers from North Carolina State University have discovered that electron spin brings a previously unknown degree of order to the high entropy alloy nickel iron chromium cobalt (NiFeCrCo)—and may play a role in giving the alloy its desirable properties. In short, chromium’s spin properties force the chromium atoms to be as far apart as possible in the NiFeCrCo structure. And, because there is a high concentration of chromium atoms in the material, this creates nanoscale domains of order with the overall “chaos” of the high entropy alloy.

Pseudoparticles travel through photoactive material zinc oxide

Researchers of Karlsruhe Institute of Technology have unveiled an important step in the conversion of light into storable energy: Together with scientists of the Fritz Haber Institute in Berlin and the Aalto University in Helsinki/Finland, they studied the formation of so-called polarons in zinc oxide. The pseudoparticles travel through the photoactive material until they are converted into electrical or chemical energy at an interface. Their findings are of relevance to photovoltaics and other applications.

Synthesis of silicon oxides opens ‘new world in a grain of sand’

A discovery by University of Georgia chemistry researchers establishes new research possibilities for silicon chemistry and the semiconductor industry. The study gives details on the first time chemists have been able to trap molecular species of silicon oxides. Using a technique they developed in 2008, the team succeeded in isolating silicon oxide fragments for the first time, at room temperature, by trapping them between stabilizing organic bases.

Expanding the reach of metallic glass

Yale University engineers have found a unique method for designing metallic glass nanostructures across a wide range of chemicals. The team demonstrates a method for applying metallic glass nanostructures to a broad range of glass-forming alloys. The process involves depositing the material into the mold in vapor form, resulting in the ability to control the size, shape, and composition of alloys at the nanoscale. The process will enable the fabrication of an array of new materials, with applications for everything from fuel cells to biological implants.