Tech Briefs Magazine - February 2023 - 26

Materials & Coatings
perform measurements on these tiny areas
of freestanding material.
The researchers then placed each substrate
on a thermal stage to precisely control
the temperature, heated each sample,
and performed micro-Raman spectroscopy.
By performing Raman measurements
on the three samples, they can extract
something called the temperature coefficient
that is substrate dependent. Using
these three different substrates and knowing
the TECs of the fused silica and the
copper, they can extract the intrinsic TEC
of the 2D material.
They performed this analysis on several
2D materials and found that they
all matched theoretical calculations.
But the researchers saw something they
didn't expect: 2D materials fell into a
hierarchy based on the elements that
comprise them. For instance, a 2D material
that contains molybdenum always
has a greater TEC than one which contains
tungsten.
The researchers dug deeper and learned
that this hierarchy is caused by a fundamental
atomic property known as electronegativity.
Electronegativity describes the
tendency for atoms to pull or extract electrons
when they bond. It is listed on the
periodic table for each element.
They found that the larger the difference
between electronegativities of elements
that form a 2D material, the lower
the material's thermal expansion coefficient
will be. An engineer could use this
method to quickly estimate the TEC for
any 2D material, rather than relying on
complex calculations that typically must
be crunched by a supercomputer.
The new study shows that this method
is highly accurate, achieving results that
match theoretical calculations. The approach
confirms that the TECs of 2D
materials fall into a much narrower
range than previously thought. This information
could help engineers design
next-generation electronics.
For more information, contact Abby
Abazorius at abbya@mit.edu; 617-2532709.
New
Coatings Reduce Impact Ice Adhesion Strength
The reduced ice adhesion strength may lead to decreased energy requirements for active ice
mitigation strategies currently used on aircraft.
Langley Research Center, Hampton, VA
A
ircraft icing is a serious problem.
There is a need for a passive durable
solution for both commercial and general
aviation aircraft. Scientists at NASA Langley
have been developing passive solutions
to this problem focusing on coatings for
aircraft surfaces that will reduce the adhesion
of impact ice.
Researchers at NASA Langley are developing
polymer coatings that reduce impact
ice adhesion strength. Current coating
compositions are based on epoxy resins
due to their availability and ease of fabrication.
It is anticipated that a successful com3.5
4
2.5
3
1.5
2
0.5
1
Control
FIG.
7
50
C7A in C3A/C7A coatings,%
NASA characterized the ice adhesion functionalities of its new ice mitigation coatings in in-flight icing
conditions at various temperatures in a test facility at Pennsylvania State University. As shown in the
graph here, the NASA coatings had a decreased ice adhesion strength compared to the control, and the
degree of adhesion reduction for the molecular coatings was temperature dependent. (Image: NASA)
26
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100
-8 °C
position could be used in other polymer
classes such as polyurethanes. Initial molecular
modeling studies of silanes terminated
with various functionalities suggest that
chain mobility effects the interface between
ice and the surface. To that end, surfaces
coated with these compounds were
applied to aluminum substrates and the
resulting monolayer coating investigated to
assess the effect of chemical functionality
and chain length under simulated in-flight
icing conditions.
The molecular coatings demonstrated
reduced ice adhesion strength, presumably
-12 °C -16 °C
as a result of the molecular flexibility imbued
by the aliphatic chains that has been
incorporated into polymers either within
the polymer backbone or as pendant
groups. Compared to an untreated aluminum
alloy surface, a test polymer coating
employing in-chain molecular flexibility
exhibited a 56 percent reduction in ice adhesion
strength at -16 °C. Similarly, another
test polymer coating employing pendant
group molecular flexibility exhibited a 19
percent reduction and a 63 percent reduction
in ice adhesion strength at -16 °C compared
to an aluminum alloy surface and a
rigid epoxy control surface, respectively.
The reduced ice adhesion strength
may lead to decreased energy requirements
for active ice mitigation strategies
currently used on aircraft when used in
conjunction. These anti-icing coatings
are a passive approach that are anticipated
to be applied to the aircraft surface
either as a topcoat or as a constituent of
aircraft paint. The coatings need to be
optimized for durability, with the goal of
achieving a reapplication frequency consistent
with routine aircraft maintenance
and painting requirements.
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/
LAR-TOPS-353.
Tech Briefs, February 2023
Ice Adhesive Shear Str., kPa

https://technology.nasa.gov/patent/LAR-TOPS-353 https://technology.nasa.gov/patent/LAR-TOPS-353 http://www.techbriefs.com

Tech Briefs Magazine - February 2023

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