Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microbullet hits confirm graphene’s strength

01.12.2014

Rice University lab test material for suitability in body armor, spacecraft protection

Graphene’s great strength appears to be determined by how well it stretches before it breaks, according to Rice University scientists who tested the material’s properties by peppering it with microbullets.


Rice University scientists fired microbullets at supersonic speeds in experiments that show graphene is 10 times better than steel at absorbing the energy of a penetrating projectile. (Credit: Jae-Hwang Lee/Rice University)

The two-dimensional carbon honeycomb discovered a decade ago is thought to be much stronger than steel. But the Rice lab of materials scientist Edwin “Ned” Thomas didn’t need even close to a pound of graphene to prove the material is on average 10 times better than steel at dissipating kinetic energy.

The researchers report in the latest edition of Science that firing microscopic projectiles at multilayer sheets of graphene allowed the scientists to determine just how hard it is to penetrate at the nano level – and how strong graphene could be in macroscopic applications.

Thomas suggested the technique he and his research group developed could help measure the strength of a wide range of materials.

While other labs have looked extensively at graphene’s electronic properties and tensile strength, nobody had taken comprehensive measurements of its ability to absorb an impact, Thomas said. His lab found graphene’s ability to simultaneously be stiff, strong and elastic gives it extraordinary potential for use as body armor or for shielding spacecraft.

The lab pioneered its laser-induced projectile impact test (LIPIT), which uses the energy from a laser to drive microbullets away from the opposite side of an absorbing gold surface at great speed. In 2012, they first used an earlier version of LIPIT to determine the properties of multiblock copolymers that could not only stop microbullets but also completely encase them.

Since that study, Thomas and lead author Jae-Hwang Lee, a former research scientist at Rice and now an assistant professor at the University of Massachusetts at Amherst, have enhanced their technique to fire single microscopic spheres with great precision at speeds approaching 3 kilometers per second, much faster than a speeding bullet from an AK-47.

The researchers built a custom stage to line up multilayer graphene sheets mechanically drawn from bulk graphite. They tested sheets ranging from 10 to 100 nanometers thick (up to 300 graphene layers). They then used a high-speed camera to capture images of the projectiles before and after hits to judge their speed and viewed microscope images of the damage to the sheets.

In every case, the 3.7-micron spheres punctured the graphene. But rather than a neat hole, the spheres left a fractured pattern of “petals” around the point of impact, indicating the graphene stretched before breaking.

“We started writing the paper about the petals, but as we went along, it became evident that wasn’t really the story,” said Thomas, the William and Stephanie Sick Dean of Rice’s George R. Brown School of Engineering. “The bullet’s kinetic energy interacts with the graphene, pushes forward, stretches the film and is slowed down.”

The experiments revealed graphene to be a stretchy membrane that, in about 3 nanoseconds before puncture, distributes the stress of the bullet over a wide area defined by a shallow cone centered at the point of impact. Tensile stress cannot travel faster than the speed of sound in materials, and in graphene, it’s much faster than the speed of sound in air (1,125 feet per second).

“For graphene, we calculated the speed at 22.2 kilometers per second, which is higher than any other known material,” Thomas said.

As a microbullet impacts the graphene, the diameter of the cone it creates – determined by later examination of the petals – provides a way to measure how much energy the graphene absorbs before breaking.

“The game in protection is getting the stress to distribute over a large area,” Thomas said. “It’s a race. If the cone can move out at an appreciable velocity compared with the velocity of the projectile, the stress isn’t localized beneath the projectile.”

Controlled layering of graphene sheets could lead to lightweight, energy-absorbing materials. “Ideally you would have a lot of independent layers that aren’t too far apart or so close that they’re touching, because the loading goes from tensile to compressive,” Thomas said. That, he said, would defeat the purpose of spreading the strain away from the point of impact.

He expects LIPIT will be used to test many experimental materials. “Before you scale a project up, you’ve got to know what will work,” he said. “LIPIT lets us develop rapid methodologies to test nanoscale materials and find promising candidates. We’re working to demonstrate to NASA and the military that these microscopic tests are relevant to macroscopic properties.”

The paper’s co-authors are Rice graduate student Phillip Loya and Jun Lou, an associate professor of materials science and nanoengineering. The Defense Threat Reduction Agency and the Welch Foundation supported the research.

Ned Thomas shows how firing microbullets at graphene quantify its strength in this video: http://youtu.be/Sevm_DHu05o

Read the abstract at http://www.sciencemag.org/content/346/6213/1092.short

David Ruth | EurekAlert!

Further reports about: graphene graphene sheets kinetic kinetic energy materials microscopic properties technique

More articles from Materials Sciences:

nachricht Researchers printed graphene-like materials with inkjet
18.08.2017 | Aalto University

nachricht Superconductivity research reveals potential new state of matter
17.08.2017 | DOE/Los Alamos National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>