Scientists explain what happens whennanoparticles collide4 April 2018, by Charlotte Hsu

A digital reconstruction shows how atoms in ananoparticle with crystal facets react when thatnanoparticle collides with another of similar shape andsize in a vacuum. The atoms turn blue when they are incontact with the opposing nanoparticle, which is notshown. In a new study, such reconstructions helped toreveal that nanoparticles with crystal facets are better attransferring energy during collisions than nanoparticleswith a more spherical shape. Credit: Yoichi Takato

Helmets that do a better job of preventingconcussions and other brain injuries. Earphonesthat protect people from damaging noises. Devicesthat convert "junk" energy from airport runwayvibrations into usable power.

New research on the events that occur when tinyspecks of matter called nanoparticles smash intoeach other could one day inform the developmentof such technologies.

Using supercomputers, scientists led by theUniversity at Buffalo modeled what happens whentwo nanoparticles collide in a vacuum. The teamran simulations for nanoparticles with three differentsurface geometries: those that are largely circular(with smooth exteriors); those with crystal facets;and those that possess sharp edges.

"Our goal was to lay out the forces that controlenergy transport at the nanoscale," says study co-author Surajit Sen, PhD, professor of physics inUB's College of Arts and Sciences. "When youhave a tiny particle that's 10, 20 or 50 atomsacross, does it still behave the same way as largerparticles, or grains? That's the guts of the questionwe asked."

"The guts of the answer," Sen adds, "is yes andno."

"Our research is useful because it builds thefoundation for designing materials that eithertransmit or absorb energy in desired ways," saysfirst author Yoichi Takato, PhD. Takato, a physicistat AGC Asahi Glass and former postdoctoralscholar at the Okinawa Institute of Science andTechnology in Japan, completed much of the studyas a doctoral candidate in physics at UB. "Forexample, you could potentially make an ultrathinmaterial that is energy absorbent. You couldimagine that this would be practical for use inhelmets and head gear that can help to preventhead and combat injuries."

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An illustration shows cross sections of two largelyspherical nanoparticles before and after they collided at31 meters per second in a computer simulation.Individual atoms within the particles are depicted as tinydots. Scientists studying nanoparticle collisionsgenerated images like these for many different crashtypes, such as those involving different velocities anddifferent nanoparticle shapes. Credit: Yoichi Takato

The study was published on March 21 in Proceedings of the Royal Society A by Takato, Senand Michael E. Benson, who completed his portionof the work as an undergraduate physics student atUB. The scientists ran their simulations at theCenter for Computational Research, UB's academicsupercomputing facility.

Additional multimedia not available throughEurekAlert! can be found at http://www.buffalo.edu/news/releases/2018/04/008.html.

What happens when nanoparticles crash

The new research focused on smallnanoparticles—those with diameters of 5 to 15nanometers. The scientists found that in collisions,particles of this size behave differently dependingon their shape.

For example, nanoparticles with crystal facetstransfer energy well when they crash into eachother, making them an ideal component ofmaterials designed to harvest energy. When itcomes to energy transport, these particles adhereto scientific norms that govern macroscopic linearsystems—including chains of equal-sized masseswith springs in between them—that are visible to thenaked eye.

In contrast, nanoparticles that are rounder in shape,with amorphous surfaces, adhere to nonlinear forcelaws. This, in turn, means they may be especiallyuseful for shock mitigation. When two sphericalnanoparticles collide, energy dissipates around theinitial point of contact on each one instead ofpropagating all the way through both. The scientistsreport that at crash velocities of about 30 metersper second, atoms within each particle shift onlynear the initial point of contact.

Nanoparticles with sharp edges are lesspredictable: According to the new study, theirbehavior varies depending on sharpness of theedges when it comes to transporting energy.

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A digital reconstruction shows how atoms in a largelyspherical nanoparticle react when that nanoparticlecollides with another of similar shape and size in avacuum. The atoms turn blue when they are in contactwith the opposing nanoparticle, which is not shown. In anew study, such reconstructions helped to reveal thatlargely spherical nanoparticles are better at absorbingenergy during collisions than nanoparticles with crystalfacets. Credit: Yoichi Takato

Designing a new generation of materials

"From a very broad perspective, the kind of workwe're doing has very exciting prospects," Sen says."It gives engineers fundamental information aboutnanoparticles that they didn't have before. If you'redesigning a new type of nanoparticle, you can nowthink about doing it in a way that takes into accountwhat happens when you have very smallnanoparticles interacting with each other."

Though many scientists are working withnanotechnology, the way the tiniest of nanoparticles behave when they crash into eachother is largely an open question, Takato says.

"When you're designing a material, what size doyou want the nanoparticle to be? How will you lay

out the particles within the material? How compactdo you want it to be? Our study can inform thesedecisions," Takato says.

More information: Yoichi Takato et al, Smallnanoparticles, surface geometry and contactforces, Proceedings of the Royal Society A:Mathematical, Physical and Engineering Science(2018). DOI: 10.1098/rspa.2017.0723

Provided by University at Buffalo

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APA citation: Scientists explain what happens when nanoparticles collide (2018, April 4) retrieved 15May 2022 from https://phys.org/news/2018-04-scientists-nanoparticles-collide.html

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