Nano-sized particles embedded in alloys can make alloys highly elastic and enable them to convert electrical and magnetic energy into movement. Credit: Physical Review Letters |
Rutgers researchers have
identified a class of high-strength metal alloys that show potential to make
springs, sensors, and switches smaller and more responsive.
The alloys could be used in blood vessel stents,
microphones, loudspeakers, and components that boost the performance of medical
imaging equipment, security systems, and clean-burning gasoline and diesel
engines.
While these nanostructured metal alloys are not new—they
are used in turbine blades and other parts demanding strength under extreme
conditions—the Rutgers researchers are pioneers at investigating these new
properties.
“We have been doing theoretical studies on these
materials, and our computer modeling suggests they will be super-responsive,”
said Armen Khachaturyan, professor of Materials Science and Engineering in the
Rutgers School of Engineering. He and postdoctoral researcher Weifeng Rao
believe these materials can be more responsive than today’s materials in the same
applications.
Published in Physical
Review Letters, the researchers describe how this class of metals with
embedded nanoparticles can be highly elastic, or “springy,” and can convert
electrical and magnetic energy into movement or vice-versa. Materials that
exhibit these properties are known among scientists and engineers as functional
materials.
One class of functional materials generates an electrical
voltage when the material is bent or compressed. Conversely, when the material
is exposed to an electric field, it will deform. Known as piezoelectric
materials, they are used in ultrasound instruments; audio components such as
microphones, speakers, and even venerable record players; autofocus motors in
some camera lenses; spray nozzles in inkjet printer cartridges; and several
types of electronic components.
The crystal structure of nanoparticles embedded in an alloy can be realigned under an electric or magnetic field, which in-turn deforms the material. Credit: Courtesy Weifeng Rao |
In another class of functional materials, changes in
magnetic fields deform the material and vice-versa. These magnetorestrictive
materials have been used in naval sonar systems, pumps, precision optical
equipment, medical and industrial ultrasonic devices, and vibration and noise
control systems.
The materials that Khachaturyan and Rao are investigating
are technically known as “decomposed two-phase nanostructured alloys.” They
form by cooling metals that were exposed to high temperatures at which the nano-sized
particles of one crystal structure, or phase, are embedded into another type of
phase. The resulting structure makes it possible to deform the metal under an
applied stress while allowing the metal to snap back into place when the stress
is removed.
These nanostructured alloys might be more effective than
traditional metals in applications such blood vessel stents, which have to be
flexible but can’t lose their “springiness.” In the piezoelectric and
magnetorestrictive components, the alloy’s potential to snap back into shape
after deforming—a property known as non-hysteresis—could improve energy
efficiency over traditional materials that require energy input to restore
their original shapes.
In addition to potentially showing responses far greater
than traditional materials, the new materials may be tunable; that is, they may
exhibit smaller or larger shape changes and output force based on varying
mechanical, electrical, or magnetic input and the material processing.
The researchers hope to test the results of their
computer simulations on actual metals in the near future.
