Material Science News and Discussions

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Artificial intelligence for safer bike helmets and better shoe soles
https://techxplore.com/news/2023-12-art ... lmets.html
by ETH Zurich

Bike helmets that absorb the energy of an impact, running shoes that give you an extra boost with every step, or implants that behave just like natural bone. Metamaterials make such applications possible. Their inner structure is the result of a careful design process, following which 3D printers produce structures with optimized properties.

Researchers led by Dennis Kochmann, Professor of Mechanics and Materials in the Department of Mechanical and Process Engineering at ETH Zurich, have developed novel AI tools that bypass the time-consuming and intuition-based design process of metamaterials. Instead, they predict metamaterials with extraordinary properties in a rapid and automated fashion.

A novelty, their framework applies to large (so-called non-linear) loads, e.g., when a helmet absorbs major forces during an impact.

Kochmann's team has been among the pioneers in designing small-scale cellular structures (similar to beam networks in timber-frame houses) to create metamaterials with specific or extreme properties. "For example, we design metamaterials that behave like fluids: hard to compress but easy to deform. Or metamaterials that shrink in all directions when compressed in a particular one," explains Kochmann.

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Researchers find way to weld metal foam without melting its bubbles
https://techxplore.com/news/2023-12-wel ... -foam.html
by Matt Shipman, North Carolina State University

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 stainless steel 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 conventional metals and alloys, such as steel. The combination of weight, strength and thermal insulation means that CMF also holds promise for use in storing and transporting nuclear material, hazardous materials, explosives and other heat-sensitive materials.

However, in order to realize many of these applications, manufacturers would need to weld multiple CMF components together. And that has posed a problem.

"Traditional fusion welding uses a filler to connect two pieces of metal," says Afsaneh Rabiei, professor of mechanical and aerospace engineering at NC State and corresponding author of a paper on the new research published in Advanced Engineering Materials titled "A Study on Welding of Porous Metals and Metallic Foams."

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Tantalum cold spray boosts potential of fusion reactor chambers
By Michael Franco
December 15, 2023
https://newatlas.com/physics/tantalum-b ... n-reactor/

The insides of nuclear fusion reactors are violent and chaotic places. A new cold-spray coating can take the heat and also trap some rogue hydrogen particles at the same time, potentially making for smaller, better plasma chambers.

While nuclear fusion is still in a very experimental stage, the powering up of the world's largest and most advanced tokamak fusion reactor in Japan this month shows that the technology is constantly moving from theory towards reality.

In fusion reactions, an ionized hydrogen gas known as plasma is subjected to levels of pressure and heat that equal those at the center of the Sun. This causes the atomic nuclei to fuse and release a tremendous amount of clean energy.

Creating the chambers that hold the plasma needed for fusion has been a challenge due to the extreme levels of heat and pressure they need to reach. Another issue with the process is that sometimes hydrogen atoms can get neutralized and escape from the plasma, which weakens its potency.

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Rubber that doesn't grow cracks when stretched many times
https://phys.org/news/2023-12-rubber-doesnt.html
by Leah Burrows, Harvard John A. Paulson School of Engineering and Applied Sciences

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have increased the fatigue threshold of particle-reinforced rubber, developing a new, multiscale approach that allows the material to bear high loads and resist crack growth over repeated use. This approach could not only increase the longevity of rubber products such as tires but also reduce the amount of pollution from rubber particles shed during use.

The research is published in Nature.

Naturally-occurring rubber latex is soft and stretchy. For a range of applications, including tires, hoses, and dampeners, rubbers are reinforced by rigid particles, such as carbon black and silica. Since their introduction, these particles greatly improve the stiffness of rubbers but not their resistance to crack growth when the material is cyclically stretched, a measurement known as the fatigue threshold.

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A novel sandwich-structured composite from biopolymers for building envelope applications
https://phys.org/news/2023-12-sandwich- ... tions.html
by Thamarasee Jeewandara , Phys.org

A new sandwich-structured composite has been developed from the surface layers of polyhydroxyalkanoate (PHA) and the interlayer of polylactic acid and cellulose microfibers. The biodegradable cellulose microfibers can be modified chemically with a sol-gel process to improve the compatibility between natural reinforcement and the polymer matrix.

While the modified cellulose microfibers were chemically developed through different processes to improve the compatibility of natural reinforcement at the polymer matrix, the modified cellulose microfibers showed highly hydrophobic characteristics with homogenous dispersion in the polylactic acid matrix.

Masoud Dadras Chomachayi and a research team at the Laval University, Canada, observed thermogravimetric analyses of the constructs to show improved thermal stability. They improved the mechanical properties of the constructs to increase its tensile modulus and strength. When the scientists added untreated fibers to the constructs, the water vapor permeability of the sandwich composite increased to show the superiority of modified cellulose microfibers when compared to untreated cellulose microfibers to develop building envelopes

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Swift 4-D printing with shape-memory polymers
https://phys.org/news/2023-12-swift-d-s ... ymers.html
by Thamarasee Jeewandara , Phys.org

Shape-memory polymers or shape-shifting materials are smart materials that have gained significant attention within materials science and biomedical engineering in recent years to build smart structures and devices. Digital light processing is a vat photopolymerization–based method with significantly faster technology to print a complete layer in a single step to create smart materials.

Fahad Alam and a team of scientists in electrical and computer engineering, and nuclear engineering at the King Abdullah University of Science and Technology, Saudi Arabia developed a facile and fast method to 3D print shape-memory polymer-based smart structures with a digital light printing 3D printer and custom resin.

They combined a liquid crystal (a material that can change its shape with temperature) with resin, to introduce shape-memory properties to directly 3D print thermoresponsive structures—while avoiding the complexity of resin preparation. The team printed the structures with different geometries and measured the shape-memory response. The shape-memory polymers can be conveniently prepared for use as smart tools, toys, and meta-materials.

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Piezo composites with carbon fibers for motion sensors
https://techxplore.com/news/2023-12-pie ... otion.html
by Tohoku University

An international research group has engineered a novel, high-strength flexible device by combining piezoelectric composites with unidirectional carbon fiber (UDCF), an anisotropic material that provides strength only in the direction of the fibers. The new device transforms kinetic energy from human motion into electricity, providing an efficient and reliable means for high-strength and self-powered sensors.

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Amorphous Silicon Carbide is Ten Times Stronger Than Kevlar and Great to Microchips
January 11, 2024 by Brian Wang

https://www.nextbigfuture.com/2024/01/a ... chips.html
Researchers at Delft University of Technology, led by assistant professor Richard Norte, have unveiled a remarkable new material with potential to impact the world of material science: amorphous silicon carbide (a-SiC). Beyond its exceptional strength, this material demonstrates mechanical properties crucial for vibration isolation on a microchip. Amorphous silicon carbide is therefore particularly suitable for making ultra-sensitive microchip sensors.

Amorphous silicon carbide boasts a yield strength 10 times greater than Kevlar, renowned for its use in bulletproof vests. IF you could make duct tape out of Amorphous silicon carbide you would need to hang about ten medium-sized cars end-to-end off that strip before it breaks.

The range of potential applications is vast. From ultra-sensitive microchip sensors and advanced solar cells, to pioneering space exploration and DNA sequencing technologies. The advantages of this material’s strength combined with its scalability make it exceptionally promising.

Nanostrings of Amorphous Silicon Carbide

The researchers adopted an innovative method to test this material’s tensile strength. Instead of traditional methods that might introduce inaccuracies from the way the material is anchored, they turned to microchip technology. By growing the films of amorphous silicon carbide on a silicon substrate and suspending them, they leveraged the geometry of the nanostrings to induce high tensile forces. By fabricating many such structures with increasing tensile forces, they meticulously observed the point of breakage. This microchip-based approach not only ensures unprecedented precision but also paves the way for future material testing.

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Tiny capsules that transform in the blink of an eye could be key to developing smaller electronics
https://phys.org/news/2024-01-tiny-caps ... aller.html
by Meg Cox, Loughborough University

Our phones and electronic devices could soon be smaller and sleeker without the risk of overheating thanks to microcapsules that transform in the blink of an eye.

Dr. Goran Vladisavljevic, of Loughborough University, and a team of researchers have designed and manufactured microcapsules filled with "phase change materials" (PCMs) that absorb heat by turning from a solid to a liquid when temperatures are elevated.

The paper, titled "Lego-Inspired Glass Capillary Microfluidic Device: A Technique for Bespoke Microencapsulation of Phase Change Materials," is published in ACS Applied Materials and Interfaces.

The capsules—which are around 0.2mm wide and do not require an energy source—could be used to absorb significant amounts of heat that would otherwise be transferred to elements in electronic devices.

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New superconducting material discovered in transition-metal dichalcogenides materials

by Zhao Weiwei and Zhang Changjin, Hefei Institutes of Physical Science, Chinese Academy of Sciences
https://phys.org/news/2024-01-supercond ... nides.html

With the support of electrical transport and magnetic measurement systems of Steady High Magnetic Field Facility (SHMFF), a research team from Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS), discovered a new superconducting material called (InSe2)xNbSe2, which possesses a unique lattice structure. The superconducting transition temperature of this material reaches 11.6 K, making it the transition metal sulfide superconductor with the highest transition temperature under ambient pressure.

The results were published in Journal of the American Chemical Society.