Phys.org August 4, 2021 Researchers at the University of Delaware hypothesized that the microbial communities of concrete reflect those of the concrete components and that these communities change as the concrete ages. To show how microbial communities change over 2 years of outdoor weathering they used two sets of concrete cylinders, one prone to the concrete-degrading alkali-silica reaction (ASR) and the other having the risk of the ASR mitigated. After identifying and removing taxa that were likely laboratory or reagent contaminants, they found that precursor materials, particularly the large aggregate (gravel), were the probable source of ∼50 to 60% of […]
Category Archives: Materials science
Exotic property of ‘ambidextrous’ crystals points to new magnetic phenomena
Phys.org August 4, 2021 Researchers in Sweden used symmetry-based analysis and numerical computations to predict the existence of antichiral ferromagnetism—a kind of ferromagnetic ordering when both types of chirality (handedness) exist simultaneously and alternate in space. They predicted a fundamentally different magnetic ordering in tetrahedral ferromagnets. They showed that antichiral ferromagnetism can be observed in a class of crystals in which many minerals are formed naturally by studying magnetic ordering in the structure with tetrahedral crystal symmetry and used micromagnetic analysis to derive the new antichiral ordering. The proposed magnetic ordering might result in a rich family of magnetic phenomena […]
Molecular library of OLED host materials
Nanowerk July 27, 2021 OLED pixels normally consist of multiple layers which ensure, for example, that electrons can travel in the pixel with as little resistance as possible. The fine-tuning of the layer properties, for example, electron mobility or the emitted wavelength (color of the light), is a complex task. An international team of researchers (South Korea, Ukraine, Belgium, Germany) compared a wide range of computer-simulated and experimentally measured properties of OLED thin films, trying to understand whether OLED design can be guided solely by computer. They established a molecular library of typical OLED materials to streamline the design of […]
To de-ice planes on the fly, researchers aim to control rather than combat ice formation
Phys.org July 26, 2021 A team of researchers in the US (Virginia Tech, UC Santa Barbara) created a de-icing method based on Cassie’s Law, which shows that air can be trapped under water drops if the drops are suspended atop a structure that is bumpy and water-repellent. They sought to make ice form in a layer with lower adhesion to the surface. They created an array of pillars, each one millimeter tall by half a millimeter wide. The tiny pedestals were machined into a pattern with a millimeter between the pillars. As the temperature dropped, frost preferentially grew on the […]
Cooling high power electronics – boron arsenide spreads heat better than diamond
Nanowerk July 9, 2021 A team of researchers in the US (UCLA, UC Irvine) explored the interface energy transport in semiconductor materials with high thermal conductivity, including boron arsenide (BAs) and boron phosphide (BP). They showed that BAs and BP cooling substrates can be heterogeneously integrated with metals, a wide-bandgap semiconductor (gallium nitride, GaN) and high-electron-mobility transistor devices. GaN-on-BAs structures exhibit a high thermal boundary conductance of 250 MW m−2 K−1, and comparison of device-level hot-spot temperatures with length-dependent scaling (from 100 μm to 100 nm) shows that the power cooling performance of BAs exceeds that of reported diamond devices. Operating AlGaN/GaN high-electron-mobility transistors with […]
Scientists Have Created a New Bendy And Flexible Form of Ice
Science Alert July 9, 2021 An international team of researchers (USA – UC Berkeley, China) used tungsten needle in a ultracold chamber around -50 deg C into which water vapor was released and applied an electric field. Water molecules were attracted to the tip of the needle, where they crystallized, forming a microfiber with a maximum width of around 10 micrometers. When the temperature was lowered to between minus 70 and minus150 degrees Celsius they were able to bend. At minus 150 degrees Celsius, the microfiber 4.4 micrometers across was able to bend into a nearly circular shape, with a […]
Ultrathin semiconductors are electrically connected to superconductors for the first time
Phys.org July 6, 2021 For future applications in electronics and quantum technology, researchers are focusing on the development of new components that consist of monolayer semiconducting material. An international team of researchers (Switzerland, Japan) has demonstrated superconducting vertical interconnect access (VIA) contacts to a monolayer of molybdenum disulfide (MoS2) using MoRe as a contact material. The electron transport was mostly dominated by a single superconductor/normal conductor junction with a clear superconductor gap. They found MoS2 regions that are strongly coupled to the superconductor resulting in resonant Andreev tunneling and junction-dependent gap characteristics, suggesting a superconducting proximity effect. Magnetoresistance measurements showed […]
A crystal made of electrons
Phys.org July 1, 2021 An international team of researchers (Switzerland, USA – Harvard University, Germany, Japan) has succeeded in observing Wigner crystals which consist of only electrons predicted almost ninety years ago. The team used optical spectroscopy to demonstrate that electrons in a monolayer semiconductor with density lower than 3 × 1011 per centimetre squared. The combination of a high electron effective mass and reduced dielectric screening enabled them to observe electronic charge order even in the absence of a moiré potential or an external magnetic field. The findings demonstrate that charge-tunable transition metal dichalcogenide monolayers enable the investigation of […]
Making the invisible visible
Science Daily May 20, 2021 It has so far been difficult to gain a more accurate picture of the course of chemical reactions at the atomic level. An international team of researchers (Germany, USA – UC Berkeley, UC San Diego, SLAC National Accelerator Laboratory, France) has shown second harmonic generation on a table-top extreme ultraviolet source. To investigate the surface of titanium sample down to the atomic level they set up a special focusing geometry, consisting of an elliptically shaped mirror to concentrate the laser radiation onto a small area. They focused the radiation with a wavelength of 32.8 nanometres […]
A new ‘gold standard’ compound for generating electricity from heat
Phys.org May 26, 2021 The principal challenges in current thermoelectric power generation modules are the availability of stable, diffusion-resistant, lossless electrical and thermal metal–semiconductor contacts that do not degrade at the hot end nor cause reductions in device efficiency. Transverse thermoelectrics avoid this problem by producing a current that runs perpendicular to the conducting device, requiring contacts only on the cold end of the generator. However, the materials known to create this sideways voltage are impractically inefficient. A team of researchers in the US (Ohio State University, University of Illinois) demonstrated that a layered crystal consisting of the elements rhenium […]