What I find
intriguing is that a suspension is produced.
It may be possible to charge up a receptive layer that acts as an
attractor and generates a skin of graphene.
This could then be treated in order to set the layer and then processed
to remove all but a single layer. The
whole process can then be repeated again and again until a near continuous layer less than three
thick is produced.
This can
generate high volumes of sheet graphene and through continuous milling we may
produce a continuous ribbon. With that
most anything else can be realistically fabricated including the skin of a MFEV
or a magnetic field exclusion vessel.
That is why a
working suspension of an electro magnetically active substance is naturally
useful.
How
to make graphene in a kitchen blender
20 Apr 2014
Don’t try this at home. No really, don’t: it
almost certainly won’t workand you won’t be able to use your kitchen
blender for food afterwards. But buried in the supplementary information of
a research paper published
today is a domestic recipe for producing large quantities of clean flakes of
graphene.
The carbon sheets are the world’s thinnest,
strongest material; electrically conductive and flexible; and tipped to transform everything from
touchscreen displays to water treatment. Many researchers — including Jonathan Coleman at Trinity College
Dublin — have been chasing ways to make large amounts of good-quality graphene
flakes.
In Nature
Materials, a team led by Coleman
(and funded by the UK-based firm Thomas Swan) describe how they took a high-power
(400-watt) kitchen blender and added half a litre of water, 10–25 millilitres
of detergent and 20–50 grams of graphite powder (found in pencil leads). They
turned the machine on for 10–30 minutes. The result, the team reports: a large
number of micrometre-sized flakes of graphene, suspended in the water.
Coleman adds, hastily, that the recipe
involves a delicate balance of surfactant and graphite, which he has not yet
disclosed (this barrier dissuaded me from trying it out; he is preparing a
detailed kitchen recipe for later publication). And in his laboratory,
centrifuges, electron microscopes and spectrometers were also used to separate
out the graphene and test the outcome. In fact, the kitchen-blender recipe was
added late in the study as a bit of a gimmick — the
Still, he says, the example shows just how
simple his new method is for making graphene in industrial quantities. Thomas
Swan has scaled the (patented) process up into a pilot plant and, says
commercial director Andy Goodwin, hopes to be making a kilogram of graphene a
day by the end of this year, sold as a dried powder and as a liquid dispersion
from which it may be sprayed onto other materials.
“It is a significant step forward towards
cheap and scalable mass production,” says Andrea Ferrari, an expert on graphene
at the University of Cambridge, UK. “The material is of a quality close to the best
in the literature, but with production rates apparently hundreds of times
higher.”
The quality of the flakes is not as high as
that of the ones the winners of the 2010 Nobel Prize in Chemistry, Andre Geim and Kostya Novoselov from
Manchester University, famously isolated using Scotch Tape to peel off single
sheets from graphite. Nor are they as large as the metre-scale graphene sheets
that firms today grow atom by atom from a vapour. But outside of high-end
electronics applications, smaller flakes suffice — the real question is how to
make lots of them.
Although hundreds of tons of graphene are
already being produced each year — and you can easily buy some online — their quality is variable. Many of
the flakes in store are full of defects or smothered with chemicals, affecting
their conductivity and other properties, and are tens or hundreds of layers
thick. “Most of the companies are selling stuff that I wouldn’t even call
graphene,” says Coleman.
The blender technique produces small flakes
some four or five layers thick on average, but apparently without defects —
meaning high electrical conductivity. Coleman thinks the
blender induces shear forces in the liquid sufficient to prise off sheets of
carbon atoms from the graphite chunks (“as if sliding cards from a deck”, he
explains).
Kitchen blenders aren’t the only way to
produce reasonably high-quality flakes of graphene. Ferrari still thinks that
using ultrasound to rip graphite apart could give better materials in some
cases. And Xinliang Feng, from the Max Planck Institute for Polymer Research in
Mainz, Germany, says that his recent publication, in the Journal of the American Chemical
Society, reports a way to produce
higher-quality, fewer-layer graphene at higher rates by electrochemical means.
(Coleman points out that Thomas Swan have taken the technique far beyond what
is reported in the paper.)
As for applications, “the graphene market
isn’t one size fits all”, says Coleman, but the researchers report testing it
as the electrode materials in solar cells and batteries. He suggests that the
flakes could also be added as a filler into plastic drinks bottles — where
their added strength reduces the amount of plastic needed, and their ability to
block the passage of gas molecules such as oxygen and carbon dioxide maintains
the drink’s shelf life.
In another application altogether, a small
amount added to rubber produces a band whose conductivity changes as it
stretches — in other words, a sensitive strain sensor. Thomas Swan’s commercial
manager, Andy Goodwin, mentions flexible, low-cost electronic displays; graphene flakes
have also been suggested for use in desalination plants and even condoms.
In each case, it has yet to be proven that
the carbon flakes really outperform other options — but the new discoveries for
mass-scale production mean that we should soon find out. At the moment, an
array of firms is competing for different market niches, but Coleman predicts a
thinning-out as a few production techniques dominate. “There are many companies
making and selling graphene now: there will be many fewer in five years’ time,”
he says.
No comments:
Post a Comment