Material's Spacing is Key to Brittle-to-ductile Transition
07-16-12
Julia R. Greer, her postdoctoral scholar Dr.Dongchan Jang, and colleagues have used experiments and atomistic simulations of nano-twinned metals (which have the unique combined effect of being strong and ductile) to decipher the specific role of the twin boundaries. They have found that it is the spacing between the twin boundaries that determines whether a material is brittle or ductile as opposed to the sample size, as would be expected. Greer states "this is probably the first study that truly isolated the twin boundaries by making samples which contained only twin boundaries, periodically spaced throughout the sample, and then tested them in tension. This understanding will help in the design of better structural materials and provide a certain amount of predictability in doing so, which has not been possible to date." [Nature Nanotechnology Article and Movies]
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Julia Greer
Dongchan Jang
postdocs
Light as a Feather, Stiffer Than a Board
11-18-11
Julia R. Greer, Assistant Professor of Materials Science and Mechanics, and colleagues have developed the world’s lightest solid material, with a density of 0.9 milligrams per cubic centimeter. The new material, called a micro-lattice, relies, on a lattice architecture: tiny hollow tubes made of nickel-phosphorous are angled to connect at nodes, forming repeating, asterisklike unit cells in three dimensions. "We're entering a new era of materials science where material properties are determined not only by the microscopic makeup of the material but also by the architecture of the constituents," Greer says. [Caltech Feature]
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Julia Greer