A technique to produce graphene on an industrial level

Graphene Roll (Image courtesy Christine Daniloff, MIT. All rights reserved)
Graphene Roll (Image courtesy Christine Daniloff, MIT. All rights reserved)

An article published in the journal “Applied Materials and Interfaces” describes a scalable process to produce graphene sheets relatively cheaply and quickly, with speeds of 5 centimeters per minute. A team of MIT researchers applied a technique based on chemical vapor deposition to synthesize high-quality graphene of uniform quality. This process allows to create graphene with nanopores, microscopic holes of the desired size to use it as a filter.

Over the years, various researches proposed a number of techniques to produce graphene. The product’s quality is the first priority because if’t is low that graphene will not have the desired characteristics and therefore can’t be used in the various fields in which revolutionary possibilities have been announced for some time.

The next problem is that of the industrial production of graphene. In the laboratory it’s possible to produce many things slowly and at a high cost, but when researchers try to apply their results to mass production, problems start emerging. Too often, the application of those techniques at industrial level requires years.

The team that includes a number of researchers who at the time were at MIT led by Professor John Hart tried to create a graphene production system that would ensure high quality to the product but was based from the beginning on processes applicable at industrial level. Chemical vapor deposition is a technique already widely used also to produce carbon-based materials including graphene.

In the technique already used in some variants, they start from a low pressure mix of hydrogen, methane and in some cases other elements. Passing the gas over a copper sheet it acts as a catalyst pulling the hydrogen from the methane leaving pure carbon that sticks to the surface and aligns perfectly with other carbon atoms to form pure graphene.

The new technique uses a sheet of copper but it’s unrolled and sent into a small furnace through a pair of tubes. In the first tube, the sheet is heated to a temperature suitable for graphene to deposit. In the second tube, a mix of methane and hydrogen gas is pumped over the copper. At that point, graphene start forming in small areas that grow to form a continuous sheet.

When the copper sheet emerges from the furnace, it’s completely covered by a graphene layer and is then rolled up on a spool. At that point, Professor John Hart and his team cut the sheet into samples and put a mesh over the graphene layer before removing the copper. The mesh is composed of a polymer with protuberances larger than graphene’s nanopores, which increases its stability and keeps the nanopores open.

Graphene is often associated with promises of a new generation of electronic equipment but Professor John Hart’s team focused on its filtering properties. For example, in March 2015 an article published in the journal “Nature Nanotechnology” described a research on a new technique of desalination of sea water using a porous membrane made of graphene. At MIT, filtering tests were conducted using solutions containing various compounds.

Various experiments conducted over the last few years showed excellent results in the purification of polluted water using graphene membranes but again the problem is in costs. The technique developed by Professor John Hart’s team aims to lower them considerably with mass production. To achieve that result, he and his team intend to perfect their technique to be able to create an industrial machinery that produces graphene continuously.

In recent years there were a number cases in which it seemed that the production of graphene could take a decisive step to enable the adoption of this material in various fields on the wide scale promised for some time. This research had precisely the purpose of creating an industrial production process so it could be the long awaited technique.

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