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Category: particle physics – Page 14

Smart phonon control boosts efficiency in eco-friendly thermoelectric material

A research team has discovered how to make a promising energy-harvesting material much more efficient—without relying on rare or expensive elements. The material, called β-Zn4Sb3, is a tellurium-free thermoelectric compound that can convert waste heat into electricity.

In their study published in Advanced Science, scientists used advanced neutron scattering techniques to peek inside the crystal and found something surprising: tiny heat vibrations (called phonons) were being disrupted by “rattling” atoms inside the structure. This phenomenon, known as avoided crossing, dramatically slowed down how heat travels through the material.

Thanks to this effect, the material’s dropped to extremely low levels—great news for . Even better, the researchers found that the single-crystal version of this material also conducts electricity better than its polycrystalline counterpart, reaching a high power conversion efficiency of 1.4%.

Porphyrin-based nanosheets capture viruses; researchers work to improve air flow for mask applications

The COVID-19 pandemic increased public awareness of the importance of mask use for personal protection. However, when the mesh size of mask fabrics is small enough to capture viruses, which are usually around one hundred nanometers in size, the fabric typically also restricts air flow, resulting in user discomfort. Researchers from Japan have now developed a new filter material that effectively captures nanoparticles, although further improvements are needed to make it suitable for comfortable mask use.

In a study published this month in Materials Advances, researchers from the Institute of Industrial Science at the University of Tokyo have developed a filter capable of capturing nanoparticles such as viruses. While the filter demonstrates high filtration efficiency, its airflow resistance is currently higher than the standards required for face masks, indicating that additional development is necessary before it can be used for personal protective equipment.

The filter is constructed from nanosheets consisting of an ordered mesh composed of porphyrins, which are flat, ring-shaped molecules with a central hole. The in the porphyrin molecules are suitably sized to allow the easy passage of the small gas molecules in air while blocking the movement of larger particles, such as viruses. The nanosheets are then supported on a fabric modified with nanofibers containing pores of several hundred nanometers to form the filter.

Closing the gaps—MXene-coated air filters show enhanced performance and reusability

Despite improvements to air filtration technology in the aftermath of the COVID-19 pandemic, some of the smallest particles—those of automobile and factory emissions—can still make their way through less efficient, but common filters. An interdisciplinary team of researchers from Drexel University’s College of Engineering have introduced a new way to improve textile-based filters by coating them with a type of two-dimensional nanomaterial called MXene.

Recently published in the journal C—Journal of Carbon Research, the team’s research reports that a non-woven polyester textile—a low-cost material with low filtration efficiency—coated with a thin layer of MXene nanomaterial can turn it into a potent filter capable of pulling some of the finest nanoparticles from the air.

“It can be challenging for common filters to contend with particles less than 100 nanometers, which include those emitted by industrial processes and automobiles,” said Michael Waring, Ph.D., a professor in Drexel’s College of Engineering, and co-author of the research. “Being able to augment a filter, through a simple coating process, to make it effective against these emissions is a significant development.”

Detecting the primordial black holes that could be today’s dark matter

Besides particles like sterile neutrinos, axions and weakly interacting massive particles (WIMPs), a leading candidate for the cold dark matter of the universe are primordial black holes—black holes created from extremely dense conglomerations of subatomic particles in the first seconds after the Big Bang.

Primordial black holes (PBHs) are classically stable, but as shown by Stephen Hawking in 1975, they can evaporate via , radiating nearly like a blackbody. Thus, they have a lifetime; it’s proportional to the cube of their initial mass. As it’s been 13.8 billion years since the Big Bang, only PBHs with an initial mass of a trillion kilograms or more should have survived to today.

However, it has been suggested that the lifetime of a black hole might be considerably longer than Hawking’s prediction due to the memory burden effect, where the load of information carried by a black hole stabilizes it against evaporation.