April_AMP_Digital

15 / 50

A D V A N C E D
M A T E R I A L S
&
P R O C E S S E S |
A P R I L
2 0 1 5
1 5
SURFACE ENGINEERING
BRIEFS
Aleris, Cleveland, offers a new 7017 aluminum alloy in North America for commercial
plate and defense uses. After extensive review and testing, the U.S. Army Research
Lab issued MIL-DTL-32505 for use in armor applications. 7017 offers high strength,
good weldability, and corrosion resistance. It is currently used in Europe and A
combat vehicles to achieve superior ballistic protection. aleris.com.
CAGE-LIKE GLASS COATING
IMPROVES BATTERIES
One major problem in lithium-
sulfur batteries is reaction products,
called lithium polysulfides, that dis-
solve in the battery’s electrolyte and
travel to the opposite electrode per-
manently; decreasing the battery’s ca-
pacity over its lifetime. Researchers in
the Bourns College of Engineering at
the University of California, Riverside,
investigated a strategy to prevent this
polysulfide shuttling phenomenon by
creating nanosized sulfur particles, and
coating them in silica (SiO2), otherwise
known as glass.
Research groups have been work-
ing on designing a cathode material in
which silica cages “trap” polysulfides
having a very thin shell of silica, and
the particles’ polysulfide products now
face a trapping barrier—a glass cage.
The team used an organic precursor to
construct the trapping barrier. “Our big-
gest challenge was to optimize the pro-
cess to deposit SiO2—not too thick, not
too thin, about the thickness of a virus,”
says Mihri Ozkan.
“We decided to incorporate mild-
ly reduced graphene oxide (mrGO), a
close relative of graphene, as a con-
ductive additive in cathode material
design, to provide mechanical stability
to the glass caged structures,” says Oz-
kan. The new generation cathode pro-
vided an even more dramatic improve-
ment than the first design, because
both a polysulfide-trapping barrier
and a flexible graphene oxide blanket
that harnesses the sulfur and silica to-
gether during cycling were engineered.
For more information: Mihri Ozkan,
951.827.2900,
.
NANOPARTICLE PAINT MAKES
TOUGH SELF-CLEANING
SURFACES
A new paint to create robust self-
cleaning surfaces was developed by
a team led by University College Lon-
don, UK, researchers. The coating can
be applied to clothes, paper, glass, and
steel and when combined with adhe-
sives, maintains its self-cleaning prop-
erties after being wiped, scratched with
a knife, and scuffed with sandpaper.
“Being waterproof allows materi-
als to self-clean as water forms marble-
shaped droplets that roll over the sur-
face, acting likeminiature vacuumclean-
ers picking up dirt, viruses, and bacteria
along the way. For this to happen, the
surface must be rough and waxy, so we
set out to create these conditions on
hard and soft surfaces by designing our
own paint and combining it with differ-
ent adhesives to help the surfaces with-
stand damage,” says chemist Yao Lu.
Different coating methods were
used to create the water repellent sur-
faces, depending on the material. An
artist’s spray-gun was used to coat
glass and steel, dip-coating was used
on cotton wool, and a syringe was used
to apply the paint onto paper. All mate-
rials became waterproof and self-clean-
ing as water droplets of different sizes
were seen bouncing instead of wetting
the surface, removing the dirt applied
by the researchers. This was main-
tained after damage was inflicted on
the surfaces.
“Our paint works extremely well
for a variety of surfaces in tough con-
ditions which were designed to simu-
late the wear and tear of materials in
the real-world. For example, car paint
frequently gets scuffed and scratched
and we wanted to make sure our paint
would survive that,” says Lu.
Mihri and Cengiz Ozkan, both professors in the Bourns College of Engineering.
one-st p coating that blocks protein growth nd k lls su face-bound ba teria on si icone may significantly reduce infections
fromme ical devices uch as catheters, accordi g o a study at A*STAR Institute of Bioengineering and Nanotechnology,
Singapore. Yi Yan Yang and his intern tional co le gue accomplished t i with a synthetic technique that combines biomimetic
surface a hesion antimicrobial capabili ie into a brush-like polym r film.