Archive for the ‘materials’ category: Page 11

Dec 30, 2023

Harnessing all-dielectric metamaterials to manipulate the polarization state of light

Posted by in categories: biotech/medical, materials

Polarization is one of the fundamental characteristics of electromagnetic waves. It can convey valuable vector information in sensitive measurements and signal transmission, which is a promising technology for various fields such as environmental monitoring, biomedical sciences, and marine exploration. Particularly in the terahertz frequency range, traditional device design methods and structures can only achieve limited performance. Designing efficient modulator devices for high-bandwidth terahertz waves presents a significant challenge.

Researchers led by Prof. Liang Wu at Tianjin University (TJU), China, have been conducting experiments in the field of all-dielectric metamaterials, specifically focusing on utilizing these materials and their to achieve effective broadband polarization conversion in the terahertz frequency range.

They propose a cross-shaped microstructure metamaterial for achieving cross-polarization conversion and linear-to-circular polarization conversion in the terahertz frequency range. The study, titled “An all-silicon design of a high-efficiency broadband transmissive terahertz polarization convertor,” was published in Frontiers of Optoelectronics.

Dec 29, 2023

Developing a futuristic elastomer with ultrahigh strain-induced crystallization

Posted by in categories: engineering, materials

Strain-induced crystallization can strengthen, toughen, and facilitate an elastocaloric effect in elastomers. The resulting crystallinity can be induced by mechanical stretching in common elastomers that are typically below 20%, with a stretchability plateau.

In a new report now published in Science Advances, Chase M. Hartquist and a team of scientists in and at MIT and Duke University in the U.S. used a class of elastomers formed by end-linking to achieve a percentage of strain-induced crystallinity.

The deswollen and end-linked star elastomer abbreviated as DELSE reached an ultrahigh stretchability to scale, beyond the saturated limit of common elastomers, to promote a high elastocaloric effect with an adiabatic temperature change.

Dec 27, 2023

Full-day, Solar-powered, Bidirectional Thermoregulatory Clothing that can respond to Changing Temperatures

Posted by in categories: materials, sustainability

A team of engineers, materials scientists and chemists at Nankai University, in China, has developed a microfiber-based meta-fabric that provides full-day thermoregulation of body temperature during periods of changing external temperatures.

In their paper published in the journal Science, the group describes how they developed their fabrics, how they work and how well they performed when tested. Xingyi Huang and Pengli, both with Shanghai Jiao Tong University, in China, have published a Perspective piece in the same journal issue outlining the work done by the team.

As the researchers note, clothing keeps people warm when it is cold, and in some cases, can help people stay cool in hot temperatures. Prior research efforts have attempted to extend the capabilities of clothing by adding heating or cooling elements, but thus far, most such products have proven to be too bulky for general use.

Dec 26, 2023

‘Negative capacitance’ could bring more efficient transistors

Posted by in categories: computing, materials

Researchers have experimentally demonstrated how to harness a property called negative capacitance for a new type of transistor that could reduce power consumption, validating a theory proposed in 2008 by a team at Purdue University.

The researchers used an extremely thin, or 2-D, layer of the semiconductor molybdenum disulfide to make a channel adjacent to a critical part of called the gate. Then they used a “ferroelectric material” called hafnium zirconium oxide to create a key component in the newly designed gate called a negative capacitor.

Capacitance, or the storage of electrical charge, normally has a positive value. However, using the ferroelectric material in a transistor’s gate allows for negative capacitance, which could result in far to operate a transistor. Such an innovation could bring more efficient devices that run longer on a battery charge.

Dec 26, 2023

AI system autonomously designs stable novel 2D compounds

Posted by in categories: materials, robotics/AI

Researchers develop an AI technique called Material Transformer Generator that integrates composition generation, structure prediction, and stability analysis to automatically design promising new two-dimensional materials.

Dec 26, 2023

Spectrotemporal shaping of itinerant photons via distributed nanomechanics

Posted by in categories: computing, materials

Optomechanical coupling enables an on-chip frequency comb and optical time-lens for 70-fold optical pulse compression.

Dec 25, 2023

Researchers find way to weld metal foam without melting its bubbles

Posted by in categories: materials, transportation

Researchers at North Carolina State University have now identified a welding technique that can be used to join composite metal foam (CMF) components together without impairing the properties that make CMF desirable. CMFs hold promise for a wide array of applications because the pockets of air they contain make them light, strong and effective at insulating against high temperatures.

CMFs are foams that consist of hollow, metallic spheres—made of materials such as or titanium—embedded in a metallic matrix made of steel, titanium, aluminum or other metallic alloys. The resulting material is both lightweight and remarkably strong, with potential applications ranging from aircraft wings to vehicle armor and body armor.

In addition, CMF is better at insulating against high heat than and alloys, such as steel. The combination of weight, strength and means that CMF also holds promise for use in storing and transporting , , explosives and other heat-sensitive materials.

Dec 25, 2023

New Photonic Chip Is the Full Package

Posted by in categories: computing, materials

The Sydney team exploited stimulated Brillouin scattering, a technique which involves converting electrical fields into pressure waves in certain insulators, such as optical fibers. In 2011, the researchers reported that Brillouin scattering held potential for high-resolution filtering, and developed new manufacturing techniques to combine a chalcogenide Brillouin waveguide on a silicon chip. In 2023, they managed to combine a photonic filter and modulator on the same type of chip. The combination gives the experimental chip a spectral resolution of 37 megahertz and a wider bandwidth than preceding chips, the team reported in a paper published 20 November in Nature Communications.

“The integration of the modulator with this active waveguide is the key breakthrough here,” says nanophotonics researcher David Marpaung of the University Twente in the Netherlands. Marpaung worked with the Sydney group a decade ago and now leads his own research group that is taking a different approach in the quest to achieve wide-band, high-resolution photonic radio sensitivity in a tiny package. Marpaung says that when someone reaches sub-10-MHz spectral resolution across a 100 gigahertz band, they will be able to replace bulkier electronic RF chips in the marketplace. Another advantage of such chips is that they would convert RF signals to optical signals for direct transmission through fiber optic networks. The winners of that race will be able to reach the huge market of telecoms providers and defense manufacturers who need radio receivers capable of reliably navigating complicated radio-frequency (RF) environments.

“Chalcogenide has a very strong Brillouin effect; it’s very good, but there is still a question of whether this is scalable…it’s still perceived as a lab material,” Marpaung says. The Sydney group had to figure out a new way to fit the chalcogenide waveguides in a 5-millimeter-square package into a standard manufactured silicon chip, which was no easy task. In 2017, the group figured out how to combine chalcogenide onto a silicon input/output ring, but it took until this year for anyone to manage the combination with a standard chip.

Dec 24, 2023

Puzzle Solved: New Near Unbreakable Material Rivals Diamond in Hardness

Posted by in categories: energy, materials

Scientists have discovered a new class of materials, carbon nitrides, which could rival diamonds in hardness. This discovery, the result of international collaboration and decades of research, opens up possibilities for various industrial applications due to their durability and other properties like photoluminescence and high energy density. Funded by international grants and published in Advanced Materials, this breakthrough marks a significant advancement in material science.

Scientists have solved a decades-long puzzle and unveiled a near unbreakable substance that could rival diamond, as the hardest material on earth, a study says.

Researchers found that when carbon and nitrogen precursors were subjected to extreme heat and pressure, the resulting materials – known as carbon nitrides – were tougher than cubic boron nitride, the second hardest material after diamond.

Dec 24, 2023

Controlling thermoelectric conversion in magnetic materials by magnetization direction

Posted by in categories: materials, particle physics

The National Institute for Materials Science (NIMS) has succeeded in directly observing the “anisotropic magneto-Thomson effect,” a phenomenon in which the heat absorption/release proportional to an applied temperature difference and charge current (i.e., Thomson effect) changes anisotropically depending on the magnetization direction in magnetic materials.

This research is expected to lead to further development of basic physics and related to the fusion area of thermoelectrics and spintronics, as well as to the development of new functionalities to control with magnetism. The study is published in the journal Physical Review Letters.

The Thomson effect has long been known as one of the fundamental thermoelectric effects in metals and semiconductors, along with the Seebeck and Peltier effects, which are driving principles of thermoelectric conversion technologies.

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