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M A T E R I A L S
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P R O C E S S E S |
N O V E M B E R / D E C E M B E R
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The surface of an aluminum strip was
treated with an electrochemical etching
process and permanently bonded with
thermoplastic by heating. Courtesy of
Julia Siekmann/Kiel University.
to recover the magnets, their permalloy
brackets, circuit boards, aluminum, and
steel, while automatically destroying
data storage media to ensure security.
The magnets may then be directly
reused by hard drive manufactur-
ers or in motor assemblies, used in
other applications through resizing or
reshaping, or processed back to rare
earth metal. The recycling method can
be adapted to target other consumer
goods containing rare earth magnets,
such as used electric motors, appli-
ances, and heating and air conditioning
systems. ornl.gov, cmi.ameslab.gov.
ETCHING METAL CREATES
BETTER BONDS
Researchers at Kiel University,
Germany, changed the surface prop-
erties of metals without affecting their
mechanical stability or physical char-
acteristics. The method is based on
an electrochemical etching process, in
which the uppermost layer of a metal is
roughened on a micrometer scale in a
tightly controlled manner. Through this
nanoscale-sculpturing process, metals
such as aluminum, titanium, or zinc can
permanently be joined with nearly all
other materials, become water-repel-
lent, or improve their biocompatibility.
The surface of a metal is con-
verted into a semiconductor, which
can be chemically etched and specifi-
cally modified as desired. The unique
etching process does not damage the
metals and does not affect their stabil-
ity. “In this way, we can permanently
connect metals which could previously
not be directly joined, such as copper
and aluminum,” says researcher Jürgen
Carstensen.
Through the etching process, a 3D
structure with tiny hooks is created. If
a bonding polymer is applied between
two treated metals, the surfaces inter-
lock with each other in all directions
like a 3D puzzle. “These 3D puzzle con-
nections are practically unbreakable.
In our experiments, it was usually the
metal or polymer that broke, but not the
connection itself,” Carstensen notes.
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