September 06, 2015

Layered graphene makes fibers 15% stronger and 31-36% better electrical and thermal properties

A team of researchers working at Rensselaer Polytechnic Institute has found a way to create a graphene fiber that is stronger and maintains conductive properties better than prior efforts.

Prior research has shown that it is possible to make graphene fibers by creating graphene oxide (GO) sheets in a liquid solution using a wet-spinning method—the graphene fibers are created using a reduction of the GO fibers technique. Unfortunately, the material that is created does not have enough of the positive attributes of 2D graphene to make it useful. In this new effort, the researchers take the same approach, but go one step further—they weave sheets the same size as others have produced, then weave some more that are smaller, then they weave the two layers together—this allows for filling in the "voids" (defects that occur during the process) in the larger materials, which results in the creation of a final product that has better electrical properties (35.8 percent), better thermal properties (31.6 percent) and higher tensile strength (from 940 megapascals on average to 1080 MPa.)

The researchers believe their process paves the way for the creation of real world useful materials made with graphene such as those that could be used in managing heat in electronics in high power applications , or by allowing for the creation of composite materials with superior attributes, energy storage and new or better sensors and/or membranes.

Science - Highly thermally conductive and mechanically strong graphene fibers


Graphene, a single layer of carbon atoms bonded in a hexagonal lattice, is the thinnest, strongest, and stiffest known material and an excellent conductor of heat and electricity. However, these superior properties have yet to be realized for graphene-derived macroscopic structures such as graphene fibers. We report the fabrication of graphene fibers with high thermal and electrical conductivity and enhanced mechanical strength. The inner fiber structure consists of large-sized graphene sheets forming a highly ordered arrangement intercalated with small-sized graphene sheets filling the space and microvoids. The graphene fibers exhibit a submicrometer crystallite domain size through high-temperature treatment, achieving an enhanced thermal conductivity up to 1290 watts per meter per kelvin. The tensile strength of the graphene fiber reaches 1080 megapascals.

A superior mix of big and small

Graphene is often described as an unrolled carbon nanotube. However, although nanotubes are known for their exceptional mechanical and conductivity properties, the same is not true of graphene-based fibers. Xin et al. intercalated small fragments of graphene into the gaps formed by larger graphene sheets that had been coiled into fibers. Once annealed, the large sheets provided pathways for conduction, while the smaller fragments helped reinforce the fibers. The result? Superior thermal and electrical conductivity and mechanical strength.

15 pages of supplemental material

SOURCES - Physorg, Science, Rensselaer Polytechnic Institute

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