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1 0 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 | M A Y / J U N E 2 0 1 9 cules out of place that form deforma- tions and fractures. This in turn leads to a cascade of damage at increas- ingly larger scales, culminating in to- tal mechanical breakdown. That pro- cess is of urgent interest to researchers studying how to build high-strength composite materials for critical com- ponents ranging from airplane wings and wind turbine blades to artificial knee joints. Scientists from the Na- tional Institute of Standards and Tech- nology (NIST), Gaithersburg, Md., and their colleagues have devised a way to observe the effects of strain at the sin- gle-molecule level by measuring how an applied force changes the 3D align- ment of molecules. The technique uses single-mole- cule, super-resolution optical micros- copy, which can resolve objects in the range of 20 nm. The new method TESTING | CHARACTERIZATION TRACKING CRYSTAL GROWTH PATTERNS ATOM BY ATOM Scientists have discovered a new mode of crystal growth at the atomic level. Researchers at the DOE’s Argonne National Laboratory (ANL), Lemont, Ill., found that the seemingly random arrangement of islands that form to begin new layers are actually very sim- ilar from layer to layer. In this mode of layer-by-layer crystal growth, the crys- tal surface starts out very smooth at the atomic level. New atoms that arrive on the surface tend to skate around until they find each other. When this hap- pens, they begin to form a new one- atom-thick layer by joining, creating a flat region known as an island. As more atoms arrive, additional islands form at other places on the surface. Eventually the islands cover the whole surface, coalescing to form a new atomic layer. By using coherent x-ray scatter- ing techniques to observe the crystal surface at the atomic scale during crys- tal growth, the team was able to char- acterize the exact arrangements of the islands as they form. The scientists note that the nucleation of new islands is not influenced by defects in the crystal structure. “This is a dynamic relation- ship. The layer that is almost completely grown communicates with the layer that is beginning to grow on top of it,” says physicist Peter Zapol. “If we under- stand how crystals grow in this mode, we might be able to bet- ter understand some of the mechanisms behind defect forma- tion and develop tech- niques to synthesize new types of crystals.” anl.gov. EXPLORING DAMAGE INCEPTION Catastrophic fail- ure in materials begins with just a few mole- Researchers compared calculated images of single molecules in different orientations (left) with experimental ones (right) to determine the 3D alignment of fluorescent molecules. Courtesy of NIST. Island formation during layer-by-layer growth of a gallium nitride crystal. Courtesy of ANL. Olympus, Tokyo, announces the launch of the Olympus Industrial Re- search Chair on Ultrasonic Nondestructive Testing with École de tech- nologie supérieure (ETS), Montreal. Representatives from Olympus, a manufacturer of NDT equipment, joined the ETS researchers to outline the challenges they will tackle over the next five years. These include sim- plifying data interpretation from ultrasonic testing, designing ultrasonic transducers for harsh environments, and engineering new ways to test materials without damage or disassembly. www.olympus-ims.com/en. BRIEFS Particle Testing Authority (PTA), a division of Micromerit- ics Instrument Corp., Norcross, Ga., announces the opening of its European laboratory in Munich. The new lab focuses on materi- als characterization services for fine powders and solid materials. particletesting.com . (a) (b)