Tech Briefs Magazine - February 2022 - 41

electrode material. The structures can
nevertheless remain relatively stable, so
they can be reused.
Rechargeable lithium-ion batteries
have two electrodes between which electrically
charged particles move. Lithium
cobalt oxide is used in one electrode
and in most of the batteries, the other is
made of carbon and copper. In traditional
battery recycling methods, some
of batteries' raw materials are lost and
lithium cobalt oxide turns into other
cobalt compounds that require a
lengthy chemical refinement process to
turn them back into electrode material.
The new method replenishes the spent
lithium in the electrode through an
electrolysis process, commonly used in
industry, through which the cobalt compound
can be directly reused.
The performance of electrodes newly
saturated with lithium is almost as good
as with those made of new material.
With further development, the method
would also work on an industrial scale.
The researchers will determine if the
same method could be used with nickelbased
batteries of electric cars.
For more information, contact Tanja Kallio,
Associate Professor, at tanja.kallio@aalto.fi.
Tires Turned into Graphene Make Stronger Concrete
An optimized flash process could reduce carbon emissions.
Rice University, Houston, TX
S
cientists have optimized a process to
convert waste from rubber tires into
graphene that can, in turn, be used to
strengthen concrete. Concrete is the
most-produced material in the world and
simply making it produces as much as 9
percent of the world's carbon dioxide
emissions. If less concrete can be used in
roads, buildings, and bridges, some of the
emissions can be eliminated at the start.
Recycled tire waste is already used as
a component of but graphene has
been proven to strengthen cementitious
ma terials, such as concrete, at the
molecular level. While the majority of
the 800 million tires discarded annually
are burned for fuel or ground up for
other applications, 16 percent of them
wind up in landfills.
The flash process has been used to
convert food waste, plastic, and other
carbon sources by exposing them to a
jolt of electricity that removes everything
but carbon atoms from the sample.
Those atoms reassemble into turbostratic
graphene, which has misaligned
layers that are more soluble
than graphene produced via
exfoliation
from graphite. That makes it easier
to use in composite materials.
Rubber proved more challenging
than food or plastic to turn into graph -
ene but the scientists optimized the
process by using commercial pyrolyzed
waste rubber from tires. After useful oils
are extracted from waste tires, this carbon
residue has until now had near-zero
value. Tire-derived carbon black or a
blend of shredded rubber tires and commercial
carbon black can be flashed into
graphene. Because turbostratic graphene
is soluble, it can easily be added to
cement to make more environmentally
friendly concrete.
Tech Briefs, February 2022
Cov
Carbon feedstock
Copper
electrode
Graphite
plugs
Quartz
tube
Turbostratic
flash graphene
Scientists optimized a process to turn rubber from discarded tires into turbostratic flash graphene.
(Photo: Courtesy of the Tour Research Group)
The scientists flashed tire-derived carbon
black and found about 70 percent
of the material converted to graphene.
When flashing shredded rubber tires
mixed with plain carbon black to add
conductivity, about 47 percent converted
to graphene.
The electrical pulses lasted between
300 milliseconds and 1 second. The
lab calculated electricity used in the
conversion process would cost about
$100 per ton of starting carbon. The
researchers blended minute amounts
of tire-derived graphene - 0.1
www.techbriefs.com
ToC
weight/percent (wt%) for tire carbon
black and 0.05 wt% for carbon black
and shredded tires - with Portland
cement and used it to produce concrete
cylinders.
Tested after curing for seven days,
the cylinders showed gains of 30 percent
or more in compressive strength.
After 28 days, 0.1 wt% of graphene sufficed
to give both products a strength
gain of at least 30 percent.
For more information, contact Mike Wil -
liams at mikewilliams@rice.edu; 713-3486728.
41
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