Material Science News and Discussions

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A thermal management material that responds to heat or cold by folding or unfolding without need for a power source
https://phys.org/news/2022-09-thermal-m ... power.html
by Bob Yirka , Phys.org
A team of researchers at Nankai University has developed a thermal management multi-layer material that responds to heat or cold by folding or unfolding itself without the need for an external power source. In their paper published in Proceedings of the National Academy of Sciences, the group describes how they came to develop the material and detail its performance when tested.

As scientists around the world work to develop alternative energy sources, others work on ways to use those that have already been developed—solar power, for example, or radiative cooling technologies. In this new effort, the researchers sought a way to shift a device between its use of solar heating or radiative cooling, automatically and without the need for a secondary power source.

For inspiration, the researchers turned to the Himalayan rabbit, which has fur that changes color depending on the season, and the leaves of the Mimosa pudica plant—its leaves open and close in reaction to changes in temperature. Their observations suggested that a material could be made that would behave similarly to the plant, allowing for switching between thermal devices.
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Engineers create the highest specific strength titanium alloy using 3D printing techniques
https://techxplore.com/news/2022-09-hig ... alloy.html
by Monash University

A world-first study led by Monash University engineers has demonstrated how cutting-edge 3D-printing techniques can be used to produce an ultra strong commercial titanium alloy—a significant leap forward for the aerospace, space, defense, energy and biomedical industries.

Australian researchers, led by Professor Aijun Huang and Dr. Yuman Zhu from Monash University, used a 3D-printing method to manipulate a novel microstructure. In doing so, they achieved unprecedented mechanical performance.

This research, published in Nature Materials, was undertaken on commercially available alloys and can be applied immediately.

"Titanium alloys require complex casting and thermomechanical processing to achieve the high strengths required for some critical applications. We have discovered that additive manufacturing can exploit its unique manufacturing process to create ultra strong and thermally stable parts in commercial titanium alloys, which may be directly implemented in service," Professor Huang says.

"After a simple post-heat treatment on a commercial titanium alloy, adequate elongation and tensile strengths over 1,600 MPa are achieved, the highest specific strength among all 3D printed metal to date. This work paves the way to fabricate structural materials with unique microstructures and excellent properties for broad applications."

In the past decade, 3D-printing has led a new era in metal fabrication due to its design freedom that can fabricate almost any geometrical part.

Titanium alloys are presently the leading 3D-printed metal components for the aerospace industry. However, most commercially available titanium alloys made by 3D-printing do not have satisfactory properties for many structural applications, especially their inadequate strength at room and elevated temperatures under harsh service conditions.
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Chemically bathed silkworm silk is 70% stronger than spider silk
By Nick Lavars
October 06, 2022
https://newatlas.com/materials/chemical ... ider-silk/

As one of the strongest materials known to science, spider silk regularly finds itself at the center of exciting engineering breakthroughs, and a new study involving a quick chemical bath could take this research into new terrain. Scientists have developed a novel treatment method for silkworm silk that alters its make up to boost its performance, with the finished product offering 70% greater strength than indomitable spider silk.

Scientists have been working to replicate the incredible properties of spider silk in some interesting ways. Farming spiders to produce the material in great quantities is one possibility, but their territorial nature doesn’t lend itself so well to these environments.

We’ve seen researchers make inroads by engineering bacteria to produce their own version of silk, and create synthetic versions of it with many of the same properties as spider silk. Some inventive advances have even involved feeding spiders graphene to make their silk stronger, or adding nanocrystals to make synthetic versions stronger and tougher than the real deal.

The silk that silkworms produce to build their cocoons is another point of interest in these research circles. Silkworm farming generates almost all commercially used silk around the world, but its lower durability than spider silk sees its use mostly limited to fashion and textiles. We’ve seen scientists address this by devising chemical treatments designed to make silkworm silk stiffer, and now a team from China’s Tianjin University has come up with a promising recipe of its own.
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New form of silicon could revolutionize semiconductor industry
https://phys.org/news/2022-10-silicon-r ... ustry.html
by Alena Kuzub, Northeastern University
After a 10-year research study that started by accident and was met with skepticism, a team of Northeastern University mechanical engineers was able to synthesize highly dense, ultra-narrow silicon nanowires that could revolutionize the semiconductor industry. Their research appears in Nature Communications.

Yung Joon Jung, Northeastern professor of mechanical and industrial engineering, says it might have been his favorite research project.

"Everything is new, and it required a lot of perseverance," says Jung, who specializes in engineering and application of nanostructure systems and previously studied carbon nanotubes.

Jung and his collaborators, including another Northeastern professor of mechanical engineering, Moneesh Upmanyu, have achieved a major advancement in nanowire synthesis by discovering a new, highly dense form of silicon and mastering a new, scalable catalyst-free etching process to produce ultra-small silicon nanowires of two to five nanometers in diameter.

About 10 years ago, students brought Jung's attention to an unusual result of an experiment they were conducting using silicon wafers. The material he saw under an electron microscope was different from the one they intended to produce, Jung says.

He decided to find out more about this substance and discovered that it was silicon with "a very, very tiny" wire-like nanostructure, Jung says. They were able to reproduce the new material, he says, but when they tried to improve the synthesis process the nanowires didn't grow.

The scientist and his team had to rewind and study, from the beginning, the synthesis mechanism and the material's atomic-scale structure and properties. Jung, an experimentalist, decided to enlist Upmanyu, who uses theory, computer modeling and simulation to understand materials and explain experiments.
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Researchers develop thermoformable ceramics, 'a new frontier in materials'
https://phys.org/news/2022-10-thermofor ... rials.html
by Ian Thomsen, Northeastern University

It was one of those happy accidents of science. Northeastern professor Randall Erb and Ph.D. student Jason Bice were working on a product for a university client—and wound up with an entirely new class of material.

Their discovery of an all-ceramic that can be compression-molded into complex parts—an industry breakthrough—could transform the design and construction of heat-emitting electronics, including cellphones and other radio components.

"Our research group's lives are very much situated at the bleeding edge of technology," says Erb, an associate professor of mechanical and industrial engineering who heads the DAPS Lab at Northeastern. "Things break a lot, and every once in a while one of those breaks turns out to be good fortune."

Last July, Erb was in his Northeastern lab with Bice, who has since earned a mechanical engineering Ph.D. They were testing an experimental ceramic compound as part of a hypersonic project for an industrial partner when something appeared to go wrong.

"We blasted it with a blowtorch and, while we were loading it, it unexpectedly deformed and fell out of the fixture," Erb says. "We looked at the sample on the floor thinking that it was a failure."
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Study opens door to new class of slippery, water-loving surfaces
https://phys.org/news/2022-10-door-clas ... faces.html
by Matt Shipman, North Carolina State University

Researchers have demonstrated that engineered surfaces can be hydrophilic—meaning they have a strong affinity for water—and yet extremely slippery. The work runs counter to conventional wisdom regarding the development of slippery materials, and suggests a new area of research for the field.

"This finding is counter-intuitive, since the longstanding view has been that slippery surfaces tend to be hydrophobic—they repel water," says Arun Kumar Kota, corresponding author of a paper on the work and an associate professor of mechanical and aerospace engineering at North Carolina State University.

"But we've now demonstrated a way to engineer the surface of materials that makes them both very slippery and hydrophilic, or SLIC, surfaces. We have some specific applications where we think this may be useful, but this is essentially an unexplored class of surfaces. A lot of work needs to be done to fully understand the scope of potential applications."

"We've also articulated exactly how these SLIC surfaces can be designed, so that other researchers can expand what appears to be a very promising field," Kota says.

Previous ways of engineering a solid surface to make it slippery tended to take one of three approaches. One approach was to texture the material to trap a layer of air against the surface, with that air pocket serving as a lubricant. The second approach was to texture the surface and trap a layer of liquid lubricant against the material that would allow it to slide past other liquids or solids. In both of these cases, damage to the texture of the surfaces due to repeated use makes them less slippery. Similarly, the loss of the gaseous or liquid lubricants over time also makes them less slippery.
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Safe, sustainable photo-on-demand synthesis of polypeptide precursors

by Kobe University
https://phys.org/news/2022-10-safe-sust ... ptide.html
In nature, there are animals that make fibers that are strong and elastic—for example, the thread that spiders produce to make webs. These fibers have a polypeptide structure and serve as inspiration for research into the development of functional materials.

Alpha (α)-amino acid N-carboxyanhydrides (NCAs) are precursors for artificial polypeptides. However, this compound decomposes easily, making it difficult to obtain commercially. Therefore, it is necessary to synthesize the right quantity of α-amino acid NCAs at the location and time that they are required.

NCAs are usually synthesized from plant-derived amino acids and phosgene. However, phosgene is extremely toxic and dangerous to use, leading to growing demand for new chemical compounds and reactions that can be substituted for it. Using the photo-on-demand phosgenation method that they previously developed, Associate Professor TSUDA Akihiko's research group at Kobe University's Graduate School of Science has succeeded in synthesizing NCA in a safe, inexpensive and simple manner from chloroform (a common organic solvent) and amino acid.
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Researchers turn asphaltene into graphene for composites
https://phys.org/news/2022-11-asphalten ... sites.html
by Mike Williams, Rice University
Asphaltenes, a byproduct of crude oil production, are a waste material with potential. Rice University scientists are determined to find it by converting the carbon-rich resource into useful graphene.

Muhammad Rahman, an assistant research professor of materials science and nanoengineering, is employing Rice's unique flash Joule heating process to convert asphaltenes instantly into turbostratic (loosely aligned) graphene and mix it into composites for thermal, anti-corrosion and 3D-printing applications.

The process makes good use of material otherwise burned for reuse as fuel or discarded into tailing ponds and landfills. Using at least some of the world's reserve of more than 1 trillion barrels of asphaltene as a feedstock for graphene would be good for the environment as well.

"Asphaltene is a big headache for the oil industry, and I think there will be a lot of interest in this," said Rahman, who characterized the process as both a scalable and sustainable way to reduce carbon emissions from burning asphaltene.

Rahman is a lead corresponding author of the paper in Science Advances co-led by Rice chemist James Tour, whose lab developed flash Joule heating, materials scientist Pulickel Ajayan and Md Golam Kibria, an assistant professor of chemical and petroleum engineering at the University of Calgary, Canada.
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Using machine learning to infer rules for designing complex mechanical metamaterials
https://phys.org/news/2022-11-machine-i ... rials.html
by Ingrid Fadelli , Phys.org

Mechanical metamaterials are sophisticated artificial structures with mechanical properties that are driven by their structure, rather than their composition. While these structures have proved to be very promising for the development of new technologies designing them can be both challenging and time-consuming.

Researchers at University of Amsterdam, AMOLF, and Utrecht University have recently demonstrated the potential of convolutional neural networks (CNNs), a class of machine learning algorithms, for designing complex mechanical metamaterials. Their paper, published in Physical Review Letters, specifically introduces two-different CNN-based methods that can derive and capture the subtle combinatorial rules underpinning the design of mechanical metamaterials.
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Going back to basics yields a printable, transparent plastic that's highly conductive
https://phys.org/news/2022-12-basics-yi ... astic.html
by Joshua Stewart, Georgia Institute of Technology
It was a simple idea—maybe even too simple to work.

Research scientist James Ponder and a team of Georgia Tech chemists and engineers thought they could design a transparent polymer film that would conduct electricity as effectively as other commonly used materials, while also being flexible and easy to use at an industrial scale.

They'd do it by simply removing the nonconductive material from their conductive element. Sounds logical, right?

The resulting process could yield new kinds of flexible, transparent electronic devices—things like wearable biosensors, organic photovoltaic cells, and virtual or augmented reality displays and glasses.

"We had this initial idea that we have a conductive element that we're covering with a nonconductive material, so what if we just get rid of that," said Ponder, who earned a Ph.D. in chemistry at Georgia Tech and returned as a research scientist in mechanical engineering. "It's a simple idea, and there were so many points where it could have failed for different reasons. But it does work, and it works better than we expected."
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