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
rexresearch.com