In a major advance, scientists have found a new and groundbreaking way to force electrons to flow only in one direction in a superconductor.
Category: materials – Page 204
The Donnan potential, revealed at last
The Donnan electric potential arises from an imbalance of charges at the interface of a charged membrane and a liquid, and for more than a century it has stubbornly eluded direct measurement. Many researchers have even written off such a measurement as impossible.
But that era, at last, has ended. With a tool that’s conventionally used to probe the chemical composition of materials, scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) recently led the first direct measurement of the Donnan potential.
“We were naïve enough to believe we could do the impossible,” said Ethan Crumlin, a staff scientist at Berkeley Lab’s Advanced Light Source (ALS), which generated the bright X-rays used in the experiment. Crumlin and his collaborators recently reported the measurement in Nature Communications.
Study observes Luttinger liquid behavior in a quasi-2D system
Luttinger liquids are usually paramagnetic materials exhibiting non-Fermi liquid behavior, such as molybdenum oxides. These “liquids” and their fascinating properties had so far been only observed in 1D and quasi-1D compounds, such as blue bronze A0.3 MoO3 (A= K, Rb, Tl) and purple bronze Li0.9 Mo6O17.
Researchers at Tsinghua University, ShanghaiTech University, and other institutes in China recently observed prototypical Luttinger liquid behavior in η-Mo4O11,a charge-density wave material with a quasi-2D crystal structure. Their findings, published in Nature Physics, could pave the way for the exploration of non-Fermi liquid behavior in other 2D and 3D quantum materials.
“In our previous work, we identified the Luttinger liquid phase in the normal state of blue bronzes, which is not surprising due to its quasi-1D nature,” Lexian Yang and Yulin Chen, two of the researchers who carried out the study, told Phys.org.
Scientists’ use of hydrogel materials leads to stem cells developing like human embryos
Materials scientists at UNSW Sydney have shown that human pluripotent stem cells in a lab can initiate a process resembling the gastrulation phase—where cells begin differentiating into new cell types—much earlier than occurs in mother nature.
For an embryo developing in the womb, gastrulation occurs at day 14. But in a dish in a lab at UNSW’s Kensington campus, Scientia Associate Professor Kris Kilian oversaw an experiment where a gastrulation-like event was triggered within two days of culturing human stem cells in a unique biomaterial that, as it turned out, set the conditions to mimic this stage of embryo development.
“Gastrulation is the key step that leads to the human body plan,” says A/Prof. Kilian.
Cooking with Phason Gas
Heat-transport measurements and neutron-scattering spectroscopy probe a form of thermal conduction based on excitations called phasons.
The understanding of how substances conduct heat is of great significance in materials science. It is needed for many important technological applications—from heat management in electronics to temperature control in buildings [1]. Therefore, when an unusual form of thermal transport is identified, materials scientists take notice. Michael Manley of Oak Ridge National Laboratory, Tennessee, and his colleagues have shown that excitations called phasons can provide the main contribution to thermal transport in a material known as fresnoite [2]. Phasons are collective lattice oscillations that occur in certain crystals with an aperiodic lattice structure—fresnoite being one of the best known. The researchers’ demonstration could pave the way for new heat-management strategies.
Thermal conductivity is a measure of a material’s ability to transfer heat. It is a property that we are all abruptly reminded of when we accidentally place our hand on a hot kitchen stove. The temperature gradient between our cooler skin and the hotter surface facilitates a transfer of energy into our hand, resulting in an unpleasant sensation. The notion that different materials conduct heat at different rates is similarly experienced when we perceive the cooling sensation of holding a metal spoon relative to a wooden one.
A robust self-healing polymer made from a common chemical
Material scientists at RIKEN have created a self-healing polymer by using an off-the-shelf compound for the first time. The strategy they used is promising for improving the durability and minimizing the environmental impact of various commercial polymers for a wide range of applications.
Polymers capable of healing themselves when damaged would last longer and thus reduce costs and the burden on the environment. Current strategies for producing self-healing polymers mainly employ reversible chemical reactions, but this usually entails complex synthesis processes. Furthermore, self-healing mechanisms based on chemical reactions may not work in certain environments such as in water and acidic and alkaline solutions.
Ideally, material scientists would like to produce polymers that self-heal under a wide range of conditions, from readily available materials, using simple synthesis processes.
Scientists Blown Away by the Toughest Material on Earth — “Unexpected Transformation”
Scientists have measured the highest toughness ever recorded, of any material, while investigating a metallic alloy made of chromium, cobalt, and nickel (CrCoNi). Not only is the metal extremely ductile – which, in materials science, means highly malleable – and impressively strong (meaning it resists permanent deformation), its strength and ductility improve as it gets colder. This runs counter to most other materials in existence.
“In the same units, the toughness of a piece of silicon is one, the aluminum airframe in passenger airplanes is about 35, and the toughness of some of the best steels is around 100. So, 500, it’s a staggering number.” —