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 Strange but true: Turning a material upside down can sometimes make it softer
20.10.2017 | Universitat Autonoma de Barcelona

nachricht Metallic nanoparticles will help to determine the percentage of volatile compounds
20.10.2017 | Lomonosov Moscow State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>