Material Science News and Discussions

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weatheriscool
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A sweet breakthrough: Scientists develop recyclable plastics based on sugars

by University of Birmingham
https://phys.org/news/2022-01-sweet-bre ... stics.html
Researchers from the University of Birmingham, U.K., and Duke University, U.S., have created a new family of polymers from sustainable sources that retain all of the qualities of common plastics, but are also degradable and mechanically recyclable.

The scientists used sugar-based starting materials rather than petrochemical derivatives to make two new polymers, one that is stretchable like rubber and another which is tough but ductile, like most commercial plastics.
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Silicon fluorescence shines through microcracks in cement, revealing early signs of damage
https://phys.org/news/2022-01-silicon-f ... aling.html
by Mike Williams, Rice University
Concrete fractures that are invisible to the naked eye stand out in images produced through a technique created at Rice University.

A collaboration between research groups at Rice and the Kuwait Institute for Scientific Research discovered by chance that common Portland cement contains microscopic crystals of silicon that emit near-infrared fluorescence when illuminated with visible light. That led to two realizations. The first was that the exact wavelength of the emission can be used to identify the particular type of cement in a structure.

The second and perhaps more important is that the near-infrared emission can reveal even very small cracks in cement or concrete. The trick is to apply a thin coat of opaque paint to the concrete when it's new. In near-infrared scans, intact concrete appears black and glowing light reveals the tiniest of cracks.
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'Atomic Armor' for accelerators enables discoveries
https://phys.org/news/2022-01-atomic-ar ... eries.html
by Los Alamos National Laboratory
Protective coatings are common for many things in daily life that see a lot of use. We coat wood floors with finish; apply Teflon to the paint on cars; even use diamond coatings on medical devices. Protective coatings are also essential in many demanding research and industrial applications.

Now, researchers at Los Alamos National Laboratory have developed and tested an atomically thin graphene coating for next-generation, electron-beam accelerator equipment—perhaps the most challenging technical application of the technology, the success of which bears out the potential for "Atomic Armor" in a range of applications.

"Accelerators are important tools for addressing some of the grand challenges faced by humanity," said Hisato Yamaguchi, member of the Sigma-2 group at the Laboratory. "Those challenges include the quest for sustainable energy, continued scaling of computational power, detection and mitigation of pathogens, and study of the structure and dynamics of the building blocks of life. And those challenges all require the ability to access, observe and control matter on the frontier timescale of electronic motion and the spatial scale of atomic bonds."
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Scientists engineer new material that can absorb and release enormous amounts of energy
https://phys.org/news/2022-02-scientist ... ounts.html
by University of Massachusetts Amherst
A team of researchers from the University of Massachusetts Amherst recently announced in the Proceedings of the National Academy of Sciences that they had engineered a new rubber-like solid substance that has surprising qualities. It can absorb and release very large quantities of energy. And it is programmable. Taken together, this new material holds great promise for a very wide array of applications, from enabling robots to have more power without using additional energy, to new helmets and protective materials that can dissipate energy much more quickly.

"Imagine a rubber band," says Alfred Crosby, professor of polymer science and engineering at UMass Amherst and the paper's senior author. "You pull it back, and when you let it go, it flies across the room. Now imagine a super rubber band. When you stretch it past a certain point, you activate extra energy stored in the material. When you let this rubber band go, it flies for a mile."
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New set of chemical building blocks makes complex 3D molecules in a snap
https://phys.org/news/2022-02-chemical- ... cules.html
by University of Illinois at Urbana-Champaign
A new set of molecular building blocks aims to make complex chemistry as simple and accessible as a toy construction kit.

Researchers at the University of Illinois Urbana-Champaign and collaborators at Revolution Medicines Inc. developed a new class of chemical building blocks that simply snap together to form 3D molecules with complex twists and turns, and an automated machine to assemble the blocks like a 3D printer for molecules.

This automation could allow chemists and nonchemists alike to develop new pharmaceuticals, materials, diagnostic probes, catalysts, perfumes, sweeteners and more, said study leader Dr. Martin D. Burke, a professor of chemistry at Illinois and a member of the Carle Illinois College of Medicine, as well as a medical doctor. The researchers reported their findings in the journal Nature.
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Super-elastic high-entropy Elinvar alloy discovered with potential for aerospace engineering
https://phys.org/news/2022-02-super-ela ... ntial.html
by City University of Hong Kong
Metals usually soften when they expand under heating, but a research team led by a City University of Hong Kong (CityU) scholar and other researchers have discovered a first-of-its-kind super-elastic alloy that can retain its stiffness even after being heated to 1,000 K (726.85 degrees Celsius) or above, with nearly zero energy dissipation. The team believes that the alloy can be applied in manufacturing high-precision devices for space missions.

The research team was led by Professor Yang Yong from CityU's Department of Mechanical Engineering (MNE) together with his collaborators. The findings were published in the science journal Nature under the title "A Highly Distorted Ultraelastic Chemically Complex Elinvar Alloy."

Challenging thermal expansion principles

Usually, the elastic modulus, i.e. stiffness, of most solids, including metals, decreases when the temperature increases as a result of thermal expansion. However, Professor Yang and his team discovered that a high-entropy alloy called Co25Ni25(HfTiZr)50, or "the high-entropy Elinvar alloy," reveals the Elinvar effect. This means the alloy firmly retains its elastic modulus over a very wide range of temperature changes.

"When this alloy is heated to 1,000 K, i.e., 726.85 degrees Celsius, or even above, it has stiffness comparable to that at room temperature, and it expands without any notable phase transition. This changes our textbook knowledge, as metals usually soften when they expand under heating," said Professor Yang.
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New material offers remarkable combo of toughness and stretchiness
https://phys.org/news/2022-02-material- ... iness.html
by North Carolina State University
Researchers have created new materials that are very stretchable and extremely tough.

"Materials that can be deformed, but that are difficult to break or tear, are desirable," says Michael Dickey, co-corresponding author of a paper on the work and the Camille & Henry Dreyfus Professor of Chemical and Biomolecular Engineering at North Carolina State University. "Nature is good at this; think of cartilage as an example. But engineering synthetic materials with these properties has been difficult, which makes our work here exciting."

The new materials fall under the broader category of ionogels, which are polymer networks that contain salts that are liquid at room temperature. These salts are called ionic liquids.

Dickey and his collaborators have made ionogels that are nearly 70% liquid, but have remarkable mechanical properties. Namely, they're tough—meaning they can dissipate a lot of energy when you deform them, making them very difficult to break. They're also easy to make, easy to process, and you can 3D print them.
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Mechanical metamaterials: Toughness and design criteria
https://phys.org/news/2022-02-mechanica ... teria.html
by Thamarasee Jeewandara , Phys.org
Mechanical metamaterials are an emerging class of materials primarily governed by their architecture to create lightweight materials with extreme mechanical properties. The functionality of such materials is limited by their tolerance to damage and defects, better known as "fracture toughness." Materials scientists credit the difficulty in part to the manufacture and characterization of a large number of unit cells. In a recent report now published on Nature Materials, Angkur Jyoti Dipanka Shaikeea and a team of scientists in engineering and metamaterials at the University of Cambridge U.K., and the University of California, Los Angeles, U.S., combined numerical and asymptotic analyses to extend the ideas of elastic fracture mechanics to mechanical 3D metamaterials and developed a design protocol to form optimally robust discrete solids.

The evolution of materials

The evolution of materials engineering has led to the development of a range of material properties with unique combinations, and the material property space can be expanded by introducing new alloys and new microstructures. Advances in additive manufacture have allowed intriguingly accurate small-scale, periodic and functionally graded architectures that can be formed into large networks to create man-made materials on the macroscopic scale known as metamaterials, alongside mechanical metamaterials more distinctly defined by their structure rather than composition.
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Strong, stretchy, self-healing polymers rapidly recover from damage
https://phys.org/news/2022-02-strong-st ... pidly.html
by RIKEN
A polymer that heals itself with unprecedented speed and efficacy when cut—almost completely recovering its original strength within minutes—has been developed by RIKEN researchers. It was produced using an advanced catalytic method for combining multiple precursors into a single polymer in a controlled fashion.

Increasing the structural complexity of polymers offers great promise for developing new materials with novel or improved properties. The controlled synthesis of complex polymers remains challenging, however.

Zhaomin Hou of the RIKEN Center for Sustainable Resource Science and his colleagues recently developed a controlled catalytic method for combining non-polar and polar olefin monomers into a single polymer. "We previously discovered that we could synthesize multiblock copolymers that exhibited excellent elasticity and self-healing by using the two-component copolymerization of non-polar ethylene and polar methoxyaryl-substituted propylenes by a half-sandwich scandium catalyst," says Hou.

The two-component polymers' properties depended strongly on the methoxyarylpropylene used. "This raised the intriguing question of whether a three-component 'terpolymer' of ethylene and two different methoxyaryl-functionalized propylenes would show unique synergistic effects on the mechanical and self-healing properties," adds Hou.

Now, Hou, four RIKEN colleagues and a collaborator have confirmed that terpolymers can show unprecedented mechanical and self-healing performance. Their elastomeric polymer could be stretched to almost 14 times its original length before breaking. And when cut in two, the polymer healed itself within five minutes to recover 99% of its toughness and 97% of its tensile strength (Fig. 1).
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Developing ultrathin films for stretchable and sturdy bioelectronic membranes

by University of California, Los Angeles
UCLA researchers have developed a unique design of ultrathin films for highly flexible yet mechanically robust bioelectronic membranes that could pave the way for diagnostic on-skin sensors that fit precisely over the body's contours and conform to its movements.

Science recently published a paper describing the research co-led by Xiangfeng Duan, professor of chemistry and biochemistry; and Yu Huang, professor and chair of the Materials Science and Engineering Department at the UCLA Samueli School of Engineering.

Held together by van der Waals forces, intermolecular interactions that can only take place at extremely close distances between atoms or molecules, the membrane is stretchable and adaptable to dynamically changing biological substrates, while being breathable and permeable to water and air. The advancement of the durable electronic material could lead to the development of noninvasive electronics for medicine, health care, biology, agriculture and horticulture. The researchers named the material van der Waals thin film, or VDWTF, which could serve as a foundational platform for living organisms to adopt electronic capabilities.

"Conceptually, the membrane is like a much-thinner version of kitchen cling film, with excellent semiconducting electronic functionality and unusual stretchability that naturally adapts to soft biological tissues with highly conformal interfaces," Duan said. "It could open up a diverse range of powerful sensing and signaling applications. For example, wearable health-monitoring devices built with this material can accurately track electrophysiological signals at the organism level or down to the level of individual cells."
https://phys.org/news/2022-03-ultrathin ... ranes.html
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