Shear Stress Affects Mechanical Properties of Nanomaterials

February 24, 2010

2 Min Read
Shear Stress Affects Mechanical Properties of Nanomaterials

Extensive research on various nanomaterials during the past several years has revealed that many materials behave differently on the nanoscale than on the "macroscale." Researchers from Johns Hopkins University (Baltimore, MD) are the latest to make headway in this area, finding that activity on the atomic level can impact a material's mechanical properties when a certain stress is applied. This discovery could have implications for the development of microdevices.



Lead author Kevin Hemker, seated between models representing how atoms are packed within an individual grain in a material, holds a silicon wafer onto which nanocrystalline aluminum thin film specimens have been deposited. Photo: Will Kirk/

A grain boundary is the interface between two 3-D crystallite clusters of atoms (grains) with differing geometries. Because they were assumed to be static, grain boundaries have always been credited with helping to resist material deformation and contributing to a material's strength. During experiments on nanocrystalline aluminum thin films, however, the researchers concluded that this long-held science belief wasn't entirely true in the case of nanomaterials.Upon applying force in the form of shear stress, the scientists observed growth of the grains, which they say can only be caused by boundary migration. Consequently, the researchers have deduced that some nanomaterials could offer better plasticity, less brittleness, higher reliability, and longer life than originally thought. They could also provide less strength, however.This breakthrough in nanomaterials research could impact the development of microdevices, MEMS-based products, and integrated circuits from some thin films and other nanomaterials. More information on this research can be found in the researchers' paper in the journal Science.

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