October AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 1 8 1 2 SMART MATERIALS COULD OPEN NEW RESEARCH FIELD A group of smart materials discov- ered by Texas A&M University research- ers and their colleagues holds promise to greatly improve the fuel efficiency of jet engines. The materials, which could also reduce airplane noise over residen- tial areas, have additional applications in a variety of other industries. “What excites me is that we have just scratched the surface of something new that could not only open a com- pletely new field of scientific research, but also enable new technologies,” says Ibrahim Karaman, head of the universi- ty’s MSE department. The discovery involves shape memory alloys that can switch from one form to another with specific trig- gers, in this case temperature. Many potential applications for these alloys involve extremely hot environments. Until now, however, economical high temperature shape memory alloys (HTSMAs) have only worked at tem- peratures up to about 400°C. Karaman began this research to address a specific problem—controlling the clearance between turbine blades and the turbine case in a jet engine. HTSMAs incorporated into the turbine case could allow maintenance of the minimum clearance across all flight regimes, thereby improving thrust- specific fuel consumption. Another important potential ap- plication of HTSMAs is the reduction of noise from airplanes as they arrive at an airport. Karaman and his colleagues tried increasing the operating tempera- tures of HTSMAs by applying principles from high-entropy alloys. The team created materials composed of four or more elements known to form shape memory alloys (nickel, titanium, haf- nium, zirconium, and palladium), but purposefully omitted gold and plati- num due to cost. “When we mixed these elements in equal proportions we found that the resulting materials could work at tem- peratures well over 500°C—one worked at 700°C—without gold or platinum. That’s a discovery,” says Karaman. Fu- ture research will try to understand what is happening at the atomic scale by conducting computer simulations. tamu.edu . CONTROLLABLE SHAPE— SHIFTING MATERIAL University of Colorado Boulder engineers developed a new materi- al that can change into intricate pre- programmed shapes in response to light and temperature stimuli, and then completely revert to its origi- nal form. The new material achieves A newmaterial can transform into complex preprogrammed shapes via light and temperature stimuli. Courtesy of Bowman Lab/CU Boulder. EMERGING TECHNOLOGY Andrea Alù, director of the Photonics Initiative at the Advanced Science Research Center at The City University of New York received a DARPA award of $3.2 million to support basic nanophotonics research. The work will enable development of next-generation defense equipment based on engineered materials that manipulate electromagnetic waves. asrc.cuny.edu . BRIEF readily programmable two-way trans- formations on a macroscopic level by using liquid crystal elastomers (LCEs), the same technology underlying mod- ern television displays. The unique molecular arrangement of LCEs makes them susceptible to dynamic changes via heat and light. To solve this, researchers installed a light-activated trigger to LCE net- works that can set a desired molecu- lar alignment in advance by exposing the object to particular wavelengths of light. The trigger then remains inac- tive until exposed to the corresponding heat stimuli. The ability to transform and then change back makes this ma- terial suitable in a wide range of appli- cations, especially biomedical devices. colorado.edu . Electromagnetic waves (red inputs) interact with metamaterials that are designed to manipulate how the waves transform and propagate (blue, green, and orange outputs). A vacuum arc melter fabricating NiTiHf HTSMAs. Courtesy of Texas A&M.