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John O | March 2018

New computer model shows why sticky tape makes graphene


by josh perry, editor
jperry@coolingzone.com

 

graphene has been the source of a number of studies since its initial discovery two decades ago and now researchers at university college london (u.k.) have used supercomputers to model the process of exfoliating graphene sheets from graphite with adhesive tape to determine what makes this process so effective for creating the two-dimensional material.

 


the research examined how graphene can be produced with sticky tape.
(wikimedia commons)

 

according to a report on the ucl website, researchers were able to model individual flakes of graphite being exfoliated to make atom-thick layers of graphene. “they also reveal that the process of peeling a layer of graphene demands 40% less energy than that of another common method called shearing,” the report continued.

 

the sticky tape process was described as “peeling egg boxes apart with a vertical motion,” which is easier than pulling horizontally and the polymethyl methacrylate adhesive on sticky tape was shown to be “ideal” for getting the edge of a graphene sheet to peel it away from the graphite flake.

 

the article explained, “graphite occurs naturally, its basic crystalline structure is stacks of flat sheets of strongly bonded carbon atoms in a honeycomb pattern. graphite’s many layers are bound together by weak interactions and can easily slide large distances over one another with little friction due to their superlubricity.”

 

ucl models matched empirical data from an experiment run by the lawrence berkeley lab (berkeley, calif.) that used a microscope with atomic resolution to examine the process.

 

“the supercomputer’s results matched berkeley’s observations showing that there is less movement when the graphene atoms neatly line up with the atoms below,” the article added.

 

with these models, the researchers hope to make creating graphene easier to produce for other scientists as well as for those seeking to commercialize the material.

 

the research was recently published in advanced materials. the abstract stated:

 

“graphite's lubricating properties due to the ‘weak’ interactions between individual layers have long been known. however, these interactions are not weak enough to allow graphite to readily exfoliate into graphene on a large scale.

 

“separating graphite layers down to a single sheet is an intense area of research as scientists attempt to utilize graphene's superlative properties. the exfoliation and processing of layered materials is governed by the friction between layers. friction on the macroscale can be intuitively understood, but there is little understanding of the mechanisms involved in nanolayered materials.

 

“using molecular dynamics and a new forcefield, graphene's unusual behavior in a superlubric state is examined, and the energy dissipated between two such surfaces sliding past each other is shown. the dependence of friction on temperature and surface roughness is described, and agreement with experiment is reported.

 

“the accuracy of the simulated behavior enables the processes that drive exfoliation of graphite into individual graphene sheets to be described. taking into account the friction between layers, a peeling mechanism of exfoliation is predicted to be of lower energy cost than shearing.”

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