Tech Briefs Magazine - August 2021 - 22

Electrical/Electronics
This innovation builds off NASA's work
in making high-quality crystalline SiGe
thin films grown on sapphire substrates. In
this case, a distinct layer structure is used
to create quantum well structures to provide
a very high-mobility pathway for both
p-type and n-type charge carriers.
The primary intended application is for
solar cells where the bandgap structure
and charge carrier mobility combine to
provide the potential for highly efficient
solar cells. The layer structure enables
back-side illumination such that the effective
solar cell area for light capture is maximized.
Conversion efficiency is expected
to be on the order of 30% or greater.
The fabrication method for high-mobility
layer structures of rhombohedrally
aligned SiGe on a triagonal substrate utilizes
C-plane (0001) sapphire, which has a
triangle plane, and a Si (Ge) (C) (111)
crystal or an alloy of group TV semiconductor
(111) crystal grown on the sapphire.
NASA is actively seeking licensees to commercialize
this technology. Please contact
NASA's Licensing Concierge at Agency-PatentLicensing@mail.nasa.gov
or call us at 202358-7432
to initiate licensing discussions.
Follow this link for more information: https://
technology.nasa.gov/patent/LAR-TOPS-166.
Lighter Radiation Shielding for Electronics
This new technique shields electronics from ionizing radiation in applications such as
military and space exploration.
North Carolina State University, Raleigh
new approach for shielding electronics
from ionizing radiation is
more cost-effective than existing techniques
and the secret ingredient is rust.
The approach can be used to maintain
the same level of radiation shielding
and reduce the weight by 30% or more
or maintain the same weight and im -
prove shielding by 30% or more compared
to the most widely used shielding
techniques.
Ionizing radiation can cause significant
problems for electronic devices.
To protect against this, devices that may
be exposed to radiation, such as devices
used in spacecraft, incorporate radiation
shielding. Weight is a significant
A
factor in designing aerospace technologies
and the shielding most commonly
found in aerospace devices consists of
putting an aluminum box around any
sensitive technologies. This has been
viewed as providing the best tradeoff
between a shield's weight and the protection
it provides.
The new technique relies on mixing
oxidized metal powder (rust) into a
polymer and then incorporating it into a
common conformal coating on the relevant
electronics. Metal oxide powder of -
fers less shielding than metal powder
but oxides are less toxic and don't pose
electromagnetic challenges that could
interfere with a device's operation.
Radiation transport calculations show
that inclusion of the metal oxide powder
provides shielding comparable to a conventional
shield. At low energies, the
metal oxide powder reduces both gamma
radiation to the electronics by a factor of
300 and the neutron radiation damage by
225%. At the same time, the coating is less
bulky than a shielding box. In computational
simulations, the worst performance
of the oxide coating still absorbed 30%
more radiation than a conventional shield
of the same weight. The oxide particulate
is also much less expensive than the same
amount of the pure metal.
For more information, contact Robert
Hayes at rbhayes@ncsu.edu; 919-515-2321.
High-Power/Pulsed-Power Electrical Switch
The switch has uses in circuit protection systems in the electric power grid, high-power
military applications, and power for materials processing.
Marshall Space Flight Center, Alabama
gnitrons are high-current switches that
can open and close very quickly using
vaporized-metal plasma arcs to complete a
circuit. Mercury is typically used because it
does not tend to plate out the internal surfaces
of the ignitron structure and cause a
short-circuit pathway, permanently closing
the switch. Mercury is toxic, making the
ignitrons difficult to manufacture, dispose
of, and service.
I
Gallium and its alloys have been considered
as alternatives to mercury. Not
only are they liquid at typical use temperatures
like mercury but they exhibit a
lower vapor pressure to withstand even
higher voltages. The key obstacle is that
using gallium or its alloys in typical igni22
Cov
tron
designs results in rapid plating of
internal surfaces and premature failure
of the switch. NASA Marshall uses a
novel internal structure of the ignitron
that prevents plating of the liquid metal
on inner surfaces.
Ignitrons are capable of conducting
high currents and withstanding high voltages,
thus providing high, instantaneous
power over a very short time. Such pulsedpower
applications as pulsed lasers,
pulsed fusion, and power rectification are
important to NASA.
Ignitron electrical switches have traditionally
been used in a number of industrial
applications in which the high-speed
switching of electrical current under high
www.techbriefs.com
ToC
voltage is needed. Today, many of these
applications are served by solid-state,
semiconductor-type switches, in part due
to the toxicity of the mercury and the lack
of suitable alternative designs. On the
whole, however, ignitrons can offer much
greater durability and reliability over
solid-state switch designs and can handle
even higher speeds and higher voltages.
NASA is actively seeking licensees to commercialize
this technology. Please contact
NASA's Licensing Concierge at AgencyPatent-Licensing@mail.nasa.gov
or call us
at 202-358-7432 to initiate licensing discussions.
Follow this link for more information:
https://technology.nasa.gov/patent/MFSTOPS-56.
Tech
Briefs, August 2021
https://technology.nasa.gov/patent/LAR-TOPS-166 https://technology.nasa.gov/patent/MFS-TOPS-56 http://www.techbriefs.com http://www.abpi.net/ntbpdfclicks/l.php?202108MDNAV
Tech Briefs Magazine - August 2021

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