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Category: materials – Page 40

The propagation of charged particles in a medium at a speed exceeding the phase speed of light in the medium (this speed also called superluminal) leads to the generation of radiation. The diagram of generated radiation during this process has a conical structure. This effect, called the Cherenkov effect, has many fundamental and applied applications, and its explanation was awarded the Nobel Prize in Physics in 1958.

The oblique incidence of light on the between two media is a similar phenomenon; in this case, a wave of secondary radiation sources is formed along the interface, which propagates at a exceeding the phase speed of light.

The and reflection of light from an interface is the result of the addition of the amplitudes of waves from all sources formed during light incidence. If one considers the interface with photo emissive material—the cathode, on which light is incident obliquely and causes of electron emission—then an electron density wave will form along the cathode surface at superluminal speed.

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Graphene, composed of layers of carbon atoms arranged in a honeycomb pattern, is recognized as a supermaterial due to its exceptional conductivity and mechanical advantages. These properties are key to advancing flexible electronics, innovative batteries, and composite materials for aerospace applications. Despite these benefits, creating elastic and durable films has been difficult. In a recent edition of Angewandte Chemie, researchers have proposed a solution by connecting graphene nanolayers through extendable bridging structures, potentially overcoming previous limitations.

The special capabilities of microscopic graphene nanolayers often drop off when the layers are assembled into foils, because they are only held together by relatively weak interactions—primarily hydrogen bonds. Approaches that attempt to improve the mechanical properties of graphene foils by introducing stronger interactions have only been partially successful, leaving particular room for improvement in the stretchability and toughness of the materials.

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Wei Zhang, Qing Liang, Xiujuan Li, Lai-Peng Ma, Xinyang Li, Zhenzhen Zhao, Rui Zhang, Hongtao Cao, Zizhun Wang, Wenwen Li, Yanni Wang, Meiqi Liu, Nailin Yue, Hongyan Liu, Zhenyu Hu, Li Liu, Qiang Zhou, Fangfei Li, Weitao Zheng, Wencai Ren, Meng Zou, Discovery of natural few-layer graphene on the Moon, National Science Review, 2024;„ https://doi.org/10.1093/nsr/nwae211.

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A group of physicists specialized in solid-state physics from the University of Cologne and international collaborators have examined crystals made from the material BaCO2V2O8 in the Cologne laboratory.

They discovered that the magnetic elementary excitations in the crystal are held together not only by attraction, but also by repulsive interactions. However, this results in a lower stability, making the observation of such repulsively bound states all the more surprising.

The results of the study, “Experimental observation of repulsively bound magnons,” are published in Nature.

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Year 2016 face_with_colon_three

Clothing tears could be a thing of the past if a new material capable of “healing” itself after being ripped proves to be commercially viable.

Researchers at Pennsylvania State University created a fabric-coating technology derived from squid ring teeth that allows conventional textiles to self-repair.

“Fashion designers use natural fibers made of proteins like wool or silk that are expensive and they are not self-healing,” said Melik Demirel, a professor of engineering science and mechanics at Penn State. “We were looking for a way to make fabrics self-healing using conventional textiles. So we came up with this coating technology.”

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Researchers continue to expand the case for the Younger Dryas Impact hypothesis. The idea proposes that a fragmented comet smashed into the Earth’s atmosphere 12,800 years ago, causing a widespread climatic shift that, among other things, led to the abrupt reversal of the Earth’s warming trend and into an anomalous near-glacial period called the Younger Dryas.

Now, UC Santa Barbara emeritus professor James Kennett and colleagues report the presence of proxies associated with the cosmic airburst distributed over several separate sites in the eastern United States (New Jersey, Maryland and South Carolina), materials indicative of the force and temperature involved in such an event, including platinum, microspherules, meltglass and shock-fractured quartz. The study appears in the journal Airbursts and Cratering.

“What we’ve found is that the pressures and temperatures were not characteristic of major crater-forming impacts but were consistent with so-called ‘touchdown’ airbursts that don’t form much in the way of craters,” Kennett said.

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