Johns Hopkins researchers have discovered that, under the right conditions, newly developed nanocrystalline materials exhibit surprising activity in the tiny spaces between the geometric clusters of atoms called nanocrystals from which they are made.
This finding, detailed recently in the journal Science, is important because these nanomaterials are becoming more ubiquitous in the fabrication of microdevices and integrated circuits. Movement in the atomic realm can affect the mechanical properties of these futuristic materials -- making them more flexible and less brittle -- and may alter the material's lifespan.
"As we make smaller and smaller devices, we've been using more nanocrystalline materials that have much smaller crystallites -- what materials scientists call grains -- and are believed to be much stronger," said Kevin Hemker, professor and chair of Mechanical Engineering in Johns Hopkins' Whiting School of Engineering and senior author of the Science article. "But we have to understand more about how these new types of metal and ceramic components behave, compared to traditional materials. How do we predict their reliability? How might these materials deform when they are subjected to stress?"
The experiments conducted by a former undergraduate research assistant and supervised by Hemker focused on what happens in regions called grain boundaries. A grain or crystallite is a tiny cluster of atoms arranged in an orderly three-dimensional pattern. The irregular space or interface between two grains with different geometric orientations is called the grain boundary. Grain boundaries can contribute to a material's strength and help it resist plastic deformation, a permanent change of shape. Nanomaterials are believed to be stronger than traditional metals and ceramics because they possess smaller grains and, as a result, have more grain boundaries.
Most scientists have been taught that these grain bounda
|Contact: Phil Sneiderman|
Johns Hopkins University