http://news.rice.edu/2020/01/27/rice-lab-turns-trash-into-valuable-graphene-in-a-flash-2/
Lab
turns trash into valuable graphene in a flash
'Green'
process promises pristine graphene in bulk using waste food,
plastic and other materials
That banana peel, turned into graphene, can help facilitate a
massive reduction of the environmental impact of concrete and
other building materials. While you're at it, toss in those
plastic empties.
A new process introduced by the Rice University lab of chemist
James Tour can turn bulk quantities of just about any carbon
source into valuable graphene flakes. The process is quick and
cheap; Tour said the "flash graphene" technique can convert a
ton of coal, food waste or plastic into graphene for a fraction
of the cost used by other bulk graphene-producing methods.
"This is a big deal," Tour said. "The world throws out 30% to
40% of all food, because it goes bad, and plastic waste is of
worldwide concern. We've already proven that any solid
carbon-based matter, including mixed plastic waste and rubber
tires, can be turned into graphene."
As reported in Nature, flash graphene is made in 10 milliseconds
by heating carbon-containing materials to 3,000 Kelvin (about
5,000 degrees Fahrenheit). The source material can be nearly
anything with carbon content. Food waste, plastic waste,
petroleum coke, coal, wood clippings and biochar are prime
candidates, Tour said. "With the present commercial price of
graphene being $67,000 to $200,000 per ton, the prospects for
this process look superb," he said.
Tour said a concentration of as little as 0.1% of flash graphene
in the cement used to bind concrete could lessen its massive
environmental impact by a third. Production of cement reportedly
emits as much as 8% of human-made carbon dioxide every year.
"By strengthening concrete with graphene, we could use less
concrete for building, and it would cost less to manufacture and
less to transport," he said. "Essentially, we're trapping
greenhouse gases like carbon dioxide and methane that waste food
would have emitted in landfills. We are converting those carbons
into graphene and adding that graphene to concrete, thereby
lowering the amount of carbon dioxide generated in concrete
manufacture. It's a win-win environmental scenario using
graphene."
"Turning trash to treasure is key to the circular economy," said
co-corresponding author Rouzbeh Shahsavari, an adjunct assistant
professor of civil and environmental engineering and of
materials science and nanoengineering at Rice and president of
C-Crete Technologies. "Here, graphene acts both as a 2D template
and a reinforcing agent that controls cement hydration and
subsequent strength development."
In the past, Tour said, "graphene has been too expensive to use
in these applications. The flash process will greatly lessen the
price while it helps us better manage waste."
"With our method, that carbon becomes fixed," he said. "It will
not enter the air again."
The process aligns nicely with Rice's recently announced Carbon
Hub initiative to create a zero-emissions future that repurposes
hydrocarbons from oil and gas to generate hydrogen gas and solid
carbon with zero emission of carbon dioxide. The flash graphene
process can convert that solid carbon into graphene for
concrete, asphalt, buildings, cars, clothing and more, Tour
said.
Flash Joule heating for bulk graphene, developed in the Tour lab
by Rice graduate student and lead author Duy Luong, improves
upon techniques like exfoliation from graphite and chemical
vapor deposition on a metal foil that require much more effort
and cost to produce just a little graphene.
Even better, the process produces "turbostratic" graphene, with
misaligned layers that are easy to separate. "A-B stacked
graphene from other processes, like exfoliation of graphite, is
very hard to pull apart," Tour said. "The layers adhere strongly
together.
But turbostratic graphene is much easier to work with because
the adhesion between layers is much lower. They just come apart
in solution or upon blending in composites.
"That's important, because now we can get each of these
single-atomic layers to interact with a host composite," he
said.
The lab noted that used coffee grounds transformed into pristine
single-layer sheets of graphene.
Bulk composites of graphene with plastic, metals, plywood,
concrete and other building materials would be a major market
for flash graphene, according to the researchers, who are
already testing graphene-enhanced concrete and plastic.
The flash process happens in a custom-designed reactor that
heats material quickly and emits all noncarbon elements as gas.
"When this process is industrialized, elements like oxygen and
nitrogen that exit the flash reactor can all be trapped as small
molecules because they have value," Tour said.
He said the flash process produces very little excess heat,
channeling almost all of its energy into the target. "You can
put your finger right on the container a few seconds
afterwards," Tour said. "And keep in mind this is almost three
times hotter than the chemical vapor deposition furnaces we
formerly used to make graphene, but in the flash process the
heat is concentrated in the carbon material and none in a
surrounding reactor.
"All the excess energy comes out as light, in a very bright
flash, and because there aren't any solvents, it's a super clean
process," he said.
Luong did not expect to find graphene when he fired up the first
small-scale device to find new phases of material, beginning
with a sample of carbon black. "This started when I took a look
at a Science paper talking about flash Joule heating to make
phase-changing nanoparticles of metals," he said. But Luong
quickly realized the process produced nothing but high-quality
graphene.
Atom-level simulations by Rice researcher and co-author Ksenia
Bets confirmed that temperature is key to the material's rapid
formation. "We essentially speed up the slow geological process
by which carbon evolves into its ground state, graphite," she
said. "Greatly accelerated by a heat spike, it is also stopped
at the right instant, at the graphene stage.
"It is amazing how state-of-the-art computer simulations,
notoriously slow for observing such kinetics, reveal the details
of high temperature-modulated atomic movements and
transformation," Bets said.
Tour hopes to produce a kilogram (2.2 pounds) a day of flash
graphene within two years, starting with a project recently
funded by the Department of Energy to convert U.S.-sourced coal.
"This could provide an outlet for coal in large scale by
converting it inexpensively into a much-higher-value building
material," he said.
https://www.youtube.com/watch?v=GzDrnoGdLO4&feature=youtu.be
Rice
lab makes pristine graphene in a flash
A new process introduced in Nature by the Rice University lab of
chemist James Tour can turn bulk quantities of just about any
carbon source into valuable graphene flakes. The process is
quick and cheap; Tour said the "flash graphene" technique can
convert a ton of coal, food waste or plastic into graphene for
about $100 in electricity costs.
https://www.nature.com/articles/s41586-020-1938-0
Gram-scale
bottom-up flash graphene synthesis
Duy X.
Luong, et al.
Abstract
Most bulk-scale graphene is produced by a top-down approach,
exfoliating graphite, which often requires large amounts of
solvent with high-energy mixing, shearing, sonication or
electrochemical treatment1,2,3. Although chemical oxidation of
graphite to graphene oxide promotes exfoliation, it requires
harsh oxidants and leaves the graphene with a defective
perforated structure after the subsequent reduction step3,4.
Bottom-up synthesis of high-quality graphene is often restricted
to ultrasmall amounts if performed by chemical vapour deposition
or advanced synthetic organic methods, or it provides a
defect-ridden structure if carried out in bulk solution4,5,6.
Here we show that flash Joule heating of inexpensive carbon
sources—such as coal, petroleum coke, biochar, carbon black,
discarded food, rubber tyres and mixed plastic waste—can afford
gram-scale quantities of graphene in less than one second. The
product, named flash graphene (FG) after the process used to
produce it, shows turbostratic arrangement (that is, little
order) between the stacked graphene layers. FG synthesis uses no
furnace and no solvents or reactive gases. Yields depend on the
carbon content of the source; when using a high-carbon source,
such as carbon black, anthracitic coal or calcined coke, yields
can range from 80 to 90 per cent with carbon purity greater than
99 per cent. No purification steps are necessary. Raman
spectroscopy analysis shows a low-intensity or absent D band for
FG, indicating that FG has among the lowest defect
concentrations reported so far for graphene, and confirms the
turbostratic stacking of FG, which is clearly distinguished from
turbostratic graphite. The disordered orientation of FG layers
facilitates its rapid exfoliation upon mixing during composite
formation. The electric energy cost for FG synthesis is only
about 7.2 kilojoules per gram, which could render FG suitable
for use in bulk composites of plastic, metals, plywood, concrete
and other building materials.
WO2018085789A1
METHODS
OF FABRICATING LASER-INDUCED GRAPHENE AND COMPOSITIONS
THEREOF
[ PDF ]
Abstract
Methods that expand the properties of laser-induced graphene
(LIG) and the resulting LIG having the expanded properties.
Methods of fabricating laser-induced graphene from materials,
which range from natural, renewable precursors (such as cloth or
paper) to high performance polymers (like Kevlar). With multiple
lasing, however, highly conductive PEI- based LIG could be
obtained using both multiple pass and defocus methods. The
resulting laser-induced graphene can be used, inter alia, in
electronic devices, as antifouling surfaces, in water treatment
technology, in membranes, and in electronics on paper and food
Such methods include fabrication of LIG in controlled
atmospheres, such that, for example, superhydrophobic and
superhydrophilic LIG surfaces can be obtained. Such methods
further include fabricating laser-induced graphene by multiple
lasing of carbon precursors.
US10505193B2
Laser
induced graphene materials and their use in electronic
devices
[ PDF ]
Abstract
In some embodiments, the present disclosure pertains to methods
of producing a graphene material by exposing a polymer to a
laser source. I