Tech Briefs Magazine - May 2023 - 41

Cryogenic Selective Surfaces
Maintaining cryogenic temperatures in deep space using a novel thermal coating.
Kennedy Space Center, Merritt Island, FL
T
hermal control coatings, i.e. coatings
with different visible versus infrared
emission, have been used by NASA on
the Orbiter and Hubble Telescope to reflect
sunlight, while allowing heat rejection
via infrared emission. However,
these coatings absorb at least 6 percent
of the Sun's irradiant power, limiting the
minimum temperature that can be
reached to about 200 K. NASA needs
better solar reflectors to keep cryogenic
fuel and oxidizers cold enough to be
maintained passively in deep space for
future missions.
A new thermal control coating material,
developed for use as a coating or rigid
tiles, reflects essentially all solar radiation
in the space environment. The novel
material has the potential to be an
enabler for long-term storage of cryogenic
liquids and propellants in space. It
can also support the long-term operation
of low-temperature devices and systems
used on spacecraft. It is based on
readily available raw materials.
These materials, which are composed
of highly optically transmissive materials,
are engineered to provide near-perfect
reflection of the full solar spectrum in
space. The materials are finely divided
such that they scatter and reflect the incoming
radiation from the UV down
A disk coated with highly reflective coating (left). Light reflecting off of the coated disk (right).
(Image: NASA)
into the mid-IR and are also coated in
some fashion with silver to extend the
reflectance down into the far IR region
of the solar spectrum.
With this near-perfect reflectance of
the complete solar spectrum, the scientists
envision use of these materials for
maintaining cryogenic temperatures
for extended periods of time in space.
The use and storage of cryogenics fluids
is critical to many space operations,
and while there are thermal control
coatings in use today for spacecraft,
none can provide this near-perfect reflection
required for long-term maintenance
of cryogenic temperatures.
NASA is actively seeking licensees to
commercialize this technology. Please
contact NASA's Licensing Concierge at
Agency-Patent-Licensing@mail.nasa.gov
or call at 202-358-7432 to initiate licensing
discussions. For more information, visit
https://technology.nasa.gov/patent/
KSC-TOPS-59.
Robust Synthesis of Vertically Aligned Single-Walled
Carbon Nanotubes
Applications include lithium-ion batteries, thermal interfaces, water purification,
supercapacitors, breathable fabrics, and sensors.
Lawrence Livermore National Laboratory, Livermore, CA
R
esearchers at Lawrence Livermore
National Laboratory (LLNL) are
scaling up the production of vertically
aligned single-walled carbon nanotubes
(SWCNT) that could revolutionize diverse
commercial products ranging from
rechargeable batteries, automotive parts
and sporting goods to boat hulls and water
filters. The research appears in the
journal Carbon.
Most CNT production today is used in
bulk composite materials and thin films,
which rely on unorganized CNT archiTech
Briefs, May 2023
tectures. For many uses, organized CNT
architectures such as vertically aligned
forests provide important advantages for
exploiting the properties of individual
CNTs in macroscopic systems.
" Robust synthesis of vertically aligned
carbon nanotubes at large scale is required
to accelerate deployment of numerous
cutting-edge devices to emerging
commercial applications, " said
LLNL Scientist and lead author Francesco
Fornasiero. " To address this need, we
demonstrated that the structural characwww.techbriefs.com
teristics
of single-walled CNTs produced
at wafer scale in a growth regime dominated
by bulk diffusion of the gaseous
carbon precursor are remarkably invariant
over a broad range of process conditions. "
The
team found that the vertically oriented
SWCNTs retained very high quality
when increasing precursor concentration
(the initial carbon) up to 30-fold,
the catalyst substrate area from 1 cm2
to
, growth pressure from 20 to 790
Mbar and gas flowrates up to 8-fold.
41
180 cm2

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Tech Briefs Magazine - May 2023

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