No matter how good a material is at conducting electricity, there’s usually some resistance – unless you use superconductive materials. Since they can conduct electricity with absolutely no loss, they could be revolutionary if not for one little problem: they only work if kept extremely cold. But now researchers at Max Planck have reported a new record high temperature for superconductivity, at a toasty −23° C (−9.4° F).
Using cutting-edge theoretical calculations performed at NERSC, researchers at Berkeley Lab’s Molecular Foundry have predicted fascinating new properties of lithium—a light alkali metal that has intrigued scientists for two decades with its remarkable diversity of physical states at high pressures.
“Under standard conditions, lithium is a simple metal that forms a textbook crystalline solid. However, scientists have shown that when you put a lithium crystal under pressure, the atomic structure changes and, somewhat counterintuitively, its conductivity drops, becoming less metallic,” said Stephanie Mack, a graduate student research assistant at Berkeley Lab and first author of the study, published in PNAS. “We’ve discovered it also becomes topological, with electronic properties similar to graphene.”
Topological materials are a recently discovered class of solids that display exotic properties, such as having insulating interiors yet highly conductive surfaces, even when deformed. They are exciting for potential applications in next-generation electronics and quantum information science. According to coauthors Sinéad Griffin and Jeff Neaton, lithium becomes topological at high but experimentally achievable pressures, comparable to one-quarter of the pressure at the Earth’s center.
There’s a known rule-breaker among materials, and a new discovery by an international team of scientists adds more evidence to back up the metal’s nonconformist reputation. According to a new study led by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and at the University of California, Berkeley, electrons in vanadium dioxide can conduct electricity without conducting heat.
The findings, to be published in the Jan. 27 issue of the journal Science, could lead to a wide range of applications, such as thermoelectric systems that convert waste heat from engines and appliances into electricity.
For most metals, the relationship between electrical and thermal conductivity is governed by the Wiedemann-Franz Law. Simply put, the law states that good conductors of electricity are also good conductors of heat. That is not the case for metallic vanadium dioxide, a material already noted for its unusual ability to switch from an insulator to a metal when it reaches a balmy 67 degrees Celsius, or 152 degrees Fahrenheit.
Arindam Banerjee, an associate professor of mechanical engineering and mechanics at Lehigh University, studies the dynamics of materials in extreme environments. He and his team have built several devices to effectively investigate the dynamics of fluids and other materials under the influence of high acceleration and centrifugal force.
One area of interest is Rayleigh-Taylor instability, which occurs between materials of different densities when the density and pressure gradients are in opposite directions creating an unstable stratification.
“In the presence of gravity—or any accelerating field—the two materials penetrate one another like ‘fingers,’” says Banerjee.
New research from the laboratory of Ozgur Sahin, associate professor of biological sciences and physics at Columbia University, shows that materials can be fabricated to create soft actuators—devices that convert energy into physical motion—that are strong and flexible, and, most important, resistant to water damage.
“There’s a growing trend of making anything we interact with and touch from materials that are dynamic and responsive to the environment,” Sahin says. “We found a way to develop a material that is water-resistant yet, at the same time, equipped to harness water to deliver the force and motion needed to actuate mechanical systems.”
The research was published online May 21 in Advanced Materials Technologies.
Posted in materials
In a terrifying breakthrough similar to the metal morphing villain in Terminator 2, scientists at the University of Sussex and Swansea University have discovered a way to apply electrical charges to liquid metal and coax it into 3D shapes such as letters and even a heart.
This discovery has been called an “extremely promising” new kind of material that can be programmed to alter its shape.
Yutaka Tokuda, the Research Associate, working on this project at the University of Sussex, says: “This is a new class of programmable materials in a liquid state which can dynamically transform from a simple droplet shape to many other complex geometry in a controllable manner.
