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Category: materials – Page 59

MIT scientists found that metals like copper can become stronger when heated and impacted at high velocities, challenging traditional views and potentially enhancing materials for extreme environments like space and high-speed manufacturing.

Metals get softer when they are heated, which is how blacksmiths can form iron into complex shapes by heating it red hot. And anyone who compares a copper wire with a steel coat hanger will quickly discern that copper is much more pliable than steel.

But scientists at MIT have discovered that the opposite happens when metal is struck by an object moving at a super high velocity: The hotter the metal, the stronger it is. Under those conditions, which put extreme stress on the metal, copper can actually be just as strong as steel. The new discovery could lead to new approaches to designing materials for extreme environments, such as shields that protect spacecraft or hypersonic aircraft, or equipment for high-speed manufacturing processes.

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Lighting a gas grill, getting an ultrasound, using an ultrasonic toothbrush ⎯ these actions involve the use of materials that can translate an electric voltage into a change in shape and vice versa.

Known as piezoelectricity, the ability to trade between mechanical stress and electric charge can be harnessed widely in capacitors, actuators, transducers, and sensors like accelerometers and gyroscopes for next-generation electronics. However, integrating these materials into miniaturized systems has been difficult due to the tendency of electromechanically active materials to ⎯ at the submicrometer scale, when the thickness is just a few millionths of an inch ⎯ get “clamped” down by the material they are attached to, which significantly dials down their performance.

Rice University researchers and collaborators at the University of California, Berkeley have found that a class of electromechanically active materials called antiferroelectrics may hold the key to overcoming performance limitations due to clamping in miniaturized electromechanical systems. A new study published in Nature Materials reports that a model antiferroelectric system, lead zirconate (PbZrO3), produces an electromechanical response that can be up to five times greater than that of conventional piezoelectric materials even in films that are only 100 nanometers (or 4 millionths of an inch) thick.

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New materials engineered to be both stiff and heat-insulating could revolutionize thermal insulation applications in electronics.

Scientists have successfully engineered materials that are both rigid and effective at insulating against heat. This extremely rare combination of attributes offers significant potential for various applications, including the creation of new thermal insulation coatings for electronic devices.

“Materials that have a high elastic modulus tend to also be highly thermally conductive, and vice versa,” says Jun Liu, co-corresponding author of a paper on the work and an associate professor of mechanical and aerospace engineering at North Carolina State University. “In other words, if a material is stiff, it does a good job of conducting heat. And if a material is not stiff, then it is usually good at insulating against heat.

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Dr. Deepan Balakrishnan, the first author, said, “Our work shows the for single-shot 3D imaging with TEMs. We are developing a generalized method using physics-based machine learning models that learn material priors and provide 3D relief for any 2D projection.”

The team also envisions further generalizing the formulation of pop-out metrology beyond TEMs to any coherent imaging system for optically thick samples (i.e., X-rays, electrons, visible light photons, etc.).

Prof Loh added, “Like human vision, inferring 3D information from a 2D image requires context. Pop-out is similar, but the context comes from the material we focus on and our understanding of how photons and electrons interact with them.”

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Water is usually something you’d want to keep away from electronic circuits, but engineers in Germany have now developed a new concept for water-based switches that are much faster than current semiconductor materials.

Transistors are a fundamental component of electronic systems, and in a basic sense they process data by switching between conductive and non-conductive states – zeroes and ones – as the semiconductor materials in them encounter electrical currents. The speed of this switching (along with the number of transistors in a chip) is a primary factor in how fast a computer system can be.

Now, researchers at Ruhr University Bochum have developed a new type of circuit that can switch much faster than existing semiconductor materials. The key ingredient is, surprisingly, water, with iodide ions dissolved into it to make it salty. A custom-made nozzle fans this water out into a flattened jet only a few microns thick.

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Graphene has been called “the wonder material of the 21st century.” Since its discovery in 2004, the material—a single layer of carbon atoms—has been touted for its host of unique properties, which include ultra-high electrical conductivity and remarkable tensile strength. It has the potential to transform electronics, energy storage, sensors, biomedical devices, and more. But graphene has had a dirty little secret: it’s dirty.

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In the last year, two independent groups have observed electrons behaving like quasiparticles with fractional amounts of charge, like –²⁄₃ and –³⁄₅, without the influence of a magnetic field.

In the 127 years since the electron was discovered, it has undergone more scrutiny than perhaps any other particle. As a result, its properties are not just well known, but rote, textbook material: Electrons have a smidgen of mass and negative electric charge. In a conductor, they swim relatively unimpeded as a current; in an insulator, they barely move.

Over time, caveats have cropped up. Under an intense magnetic field, for example, electrons can lose their individual identities and form “quasiparticles”: collective entities, like the shape formed by a school of fish. But even these collective states have been well cataloged.

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