Nov_Dec_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 | N O V E M B E R / D E C E M B E R 2 0 1 7 1 2 SHAPE MEMORY RESEARCH STRIKES GOLD Scientists at the Karlsruhe Insti- tute of Technology (KIT), Germany, and the Technion – Israel Institute of Technology observed, for the first time, self-healing in tiny particles of pure gold. The discovery overturns the long-held assumption that pure metals are incapable of shape memory. First, researchers simulated mechanical de- fects in gold particles of various shapes using high-powered computing, then produced the defects in actual particles with the measurement tip of a scanning force microscope. They found that an- nealing air temperatures far below the melting temperature of gold caused the gold atoms to move along surface steps back into the dents, refilling them almost completely and nearly returning the particles to their original shapes. Because such surface steps occur in many deformed metals, the scien- tists expect that other metals pos- sess self-healing properties as well. Until now, the search for self- healing materials has been concen- trated on metal al- loys and complex polymers, neither of which exhibit complete shape memory. The new findings could lead to the design of components for structures smaller than one thousandth of a millimeter. kit.edu/english , www.technion.ac.il/en. SNOW-CLEARING CONCRETE A groupof U.S. researchers demon- strated a method to produce road and runway surfaces that clear themselves of ice and snow, offering an environ- mentally friendly, nondestructive al- ternative to chemical deicers, salt, and plowing. The team—from Drexel Uni- versity, Purdue University, and Oregon State University—embedded the phase change material (PCM) paraffin oil into concrete. Paraffin oil is widely available, chemically stable, and relatively inex- pensive, and like all PCMs, it releases thermal energy when shifting between physical states. As temperatures fall, paraffin in a roadway would change from liquid to solid, emitting heat and melting ice and snow. Adding paraffin oil to the aggregate used in concrete mix could give it the ability to melt ice and snowwhen tempera- tures fall. EMERGING TECHNOLOGY The U.S. DOE is launching a multi-lab effort to apply high-performance computing to the development of materials for severe environments. The High Performance Computing for Materials Program will connect U.S.-based industry with the resources of national laboratories including Lawrence Livermore, Los Alamos, Oak Ridge, and the National Energy Technology Laboratory, adding more as the program grows. The initial focus will be challenges posed by corrosion, chemicals, vibration, fatigue or stress, and extremes in pressure, radiation, and temperature, along with lightweight materials development. hpc4mtls.llnl.gov. BRIEF Gold atoms move into a previous dent, refilling it almost completely. Courtesy of KIT. To test their method, the team created three concrete slabs—one containing paraffin-filled pipes, one containing porous, paraffin-infused aggregate, and a control slab without paraffin. Each was sealed each in an insulated container and covered with five inches of lab-made snow. At tem- peratures between 35° and 44°F, both paraffin-treated slabs completely melt- ed the snow within 25 hours, while the control remained frozen. The slab with tubes melted the snow fastest, proba- bly because the consistent diameter of the tubes allowed the paraffin inside to solidify more quickly. In a second ex- periment, with air temperatures below freezing, the aggregate was most ef- fective because capillary pore pressure reduced the rate of freezing, allowing a more gradual release of heat. Next, the team plans to research how em- bedded PCMs affect the durability, skid resistance, and long-term stability of pavement. drexel.edu , purdue.edu , oregonstate.edu .