Tests elucidate high fatigue lifetime of graphene
- PDF / 365,430 Bytes
- 1 Pages / 585 x 783 pts Page_size
- 59 Downloads / 197 Views
says, “The silicon-carbon composite electrodes with the controllable silicon content, excellent flexibility, high initial coulombic efficiency show great potential for flexible and durable electronics.” Xu was not involved in this study. The research team has confirmed that the topological transformation of cellulose
is universal. Li says, “Similar results can be achieved with appropriate regulatory parameters when different materials, tin nanoparticles for example, are used to replace silicon nanoparticles, which provides a good opportunity to develop functional composites for different applications.” Tianyu Liu
Amplitude, A1 (nm)
G
says Tobin Filleter, a mechanical and industrial engineering professor at the University of Toronto. “And the answer is yes, there’s a mechanism that will lead to failure at loads below tensile strength. This sets the stage for understanding fatigue life of this general class of 2D materials.” The research team led by Filleter, materials science and engineering professor Chandra Veer Singh and mechanical engineering professor Yu Sun also at Toronto, conducted physical experiments as well as molecular dynamics simulations. In the experiments, they pressed an atomic force microscope (AFM) tip to the center of freestanding films of the graphene and graphene oxide material and then oscillated the tip at a frequency of 100 KHz. AFM is a widely available technique, but the researchers had to build a special device for the experiments in order to handle these very thin 2D material samples. They etched a silicon chip with half a million holes, each just a few micrometers in diameter, and stretched a graphene sheet over the holes. “There’s
Static Deflection, δ 1 (nm)
no commercial approach to do this type of mechanical testing on atomically thin materials where we’re controlling static load plus cyclic load,” Filleter says. raphene is known to be the world’s They used a load that was 50–70% of strongest material. Its first comthe material’s ultimate tensile strength, the mercial uses, in sports equipment and same fraction that is used in studies on metspecialty gear, rely on this mechanical als and alloys. They found that the materiresilience. Yet, it is also brittle, fracturing als could withstand an average stress of 71 when the load on it passes that maximum GPa for over a billion cycles before failing. strength level. Computer simulations showed differ But what happens to the material when ent failure mechanisms for graphene and it faces a small mechanical load over and graphene oxide. In graphene, mechanical over again? This fatigue life of graphene loading and thermal fluctuation cause an and associated damage mechanism reirreversible bond rotation near the site of main unknown. In a recent study puba defect, causing the material to abruptly lished in Nature Materials (doi:10.1038/ fail without a progressive buildup of s41563-019-0586-y), researchers have cracks or damage as would happen norfound that the two-dimensional (2D) mamally in metals. terial can withstand more than a billion
Data Loading...
