July_August_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 | J U L Y / A U G U S T 2 0 1 9 1 2 A NEW ERA OF ATOMIC ENGINEERING Scientists at MIT, Cambridge, Mass., in collaboration with international re- searchers, developed a method that can reposition atoms with a highly fo- cused electron beam and control their exact location and bonding orienta- tion. The finding could ultimately lead to new ways of making quantum com- puting devices or sensors and usher in a new age of atomic engineering, say researchers. In the new study, those tools are being used to control processes that are yet an order of magnitude smaller. While others have previously manipu- lated the positions of individual atoms, that method involved picking up each atomon the needlelike tip of a scanning tunneling microscope and then drop- ping it in position—a relatively slow mechanical process. The new technique manipu- lates atoms using a rela- tivistic electron beam in a scanning transmission electron microscope, so it can be fully controlled electronically by mag- netic lenses without re- quiring any mechanical parts. Using electronic con- trols and artificial in- telligence, the team be- lieves they will be able to manipulate atoms at microsecond timescales, according to lead researcher Ju Li. “That’s many orders of magnitude fas- ter than we can manipulate them now with mechanical probes. Also, it should be possible to have many elec- tron beams working simultaneously on the same piece of material,” adds Li. mit.edu. HIGH-STRENGTH SHAPE MEMORY ALLOYS Using a supercomputer simula- tion, researchers from the Agency for Science, Technology and Research (A*STAR), Singapore, have shown that high strength and shape memory can be realized at the same time by com- bining crystal grains of different sizes, a feat previously thought impossible. This finding unveils the potential of ad- vanced simulations for tailoring materi- als to achieve previously unattainable physical properties. EMERGING TECHNOLOGY A new multipurpose, state-of-the-art laboratory space for expanding scientific ac- tivities at the DOE’s Oak Ridge National Laboratory (ORNL), Tenn., is now under construction. The new Translational Research Capability (TRC) will be built for world-leading research in computing and materials science and will advance the science of quantum information. Located in the central ORNL campus, the $95 million TRC project will accommodate sensitive equipment, multipurpose labs, heavy equipment, and inert environment labs. ornl.gov. BRIEF However, shape memory alloys (SMAs) lose their functionality when the size of the constituent crystal grains goes below a certain limit—typically a few tens of nanometers. This is import- ant because SMAs, like most polycrys- talline metals, become strong at very small grain sizes, where the memory effect is lost. While obtaining strength and memory at the same time in the same material seemed impossible, the researchers proposed it could dramati- cally broaden the potential application and useful functions of SMAs. By studying a wide range of grain size combinations, researchers were able to show that the formation of the martensitic phase, and hence the ap- pearance of shape memory, could be controlled by modifying the microstruc- ture’s grain size distribution. Ultimate- ly, the team achieved a process for ob- taining a microstructure in which one region undergoes phase transforma- tion to martensite while other regions remain austenitic, enabling the possi- bility to design materials with varying degrees of shape memory functionality throughout. www.a-star.edu.sg . Diagram illustrates controlled switching of positions of a phosphorous atomwithin a layer of graphite by using an electron beam. Courtesy of MIT. Simulated shape memory phase transition in an SMA with small and large crystal grains. Courtesy of IOP Publishing. Conceptual drawing of ORNL’s Translational Research Capability lab.