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be able to offer us solutions for mobility
in harsh environments, like on Jupiter’s
moon Europa.”
The mystery material can be ex-
plained as both a metal and a glass by
looking at its atomic structure. Metals
have an organized crystalline arrange-
ment, but if they are heated to a liquid
state, they melt and atoms become ran-
domized. Upon rapid cooling—about
1832°F (1000°C) per second—their
non-crystalline, liquid form can be
trapped in place, producing a random
arrangement of atoms with an amor-
phous microstructure. That structure
gives these materials their common
names—amorphous metals, or metallic
glass.
By virtue of being cooled so rap-
idly, the material is technically a glass.
It can flow easily and be blow-molded
when heated, like windowpane glass.
When this glassymaterial is produced in
parts greater than about four tenths of
an inch (1 mm), it is called bulk metallic
glass, or BMG.
Among their attractive qualities,
BMGs have low melting temperatures.
That allows parts to be cast using in-
jection-molding technology, similar to
what is used in the plastics industry,
but with much higher strength and
wear-resistance. BMGs also do not get
brittle in extreme cold, a factor that can
lead to gear tooth fractures. This last
quality makes the material particularly
useful for the robotics being developed
at JPL. Not only can BMGs allow gears
to perform at low temperatures, they
can also be manufactured at a fraction
of the cost of their steel counterparts
without sacrificing performance. This is
potentially game changing for reducing
the cost of robots that use strain wave
gears, which are often their most ex-
pensive components.
For more informa-
tion: Douglas Hofmann,
dch@jpl.nasa.
gov,
www.jpl.nasa.gov.
Bulk metallic glass does not become brittle in extreme cold, making it an ideal material
for robotics operated in space. Courtesy of NASA/JPL-Caltech.
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