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Mechanical behavior of Nanocrystalline Thin Films
Figure 1: High resolution transmission electron micrograph showing grains (crystallites) that are tens of nanometers in diameter. The white spots in G1 are atomic columns.
Figure 2: Micro-scale devices on a silicon chip.
Description
Many engineering materials consist of atoms arranged in ordered, repeating units to form crystallites or “grains”. When the size of these grains enters the nanometer range (Fig. 1), the properties of the material in question begin to change. Professor Kevin Hemker and his research group are working to understand why the mechanical response of these nanocrystalline materials is different from that of their traditional counterparts. Having a complete understanding of how these materials deform is essential for designing the next generation of small scale devices. Tiny manipulators and circuits made with nanocrystalline materials will allow for smaller, more complex technologies in the near future (Fig. 2). Micro-devices of this kind are currently used in applications ranging from computer chips to sensors for automobile airbags.
Professor Hemker’s work has found that the process by which nanocrystalline materials deform is vastly different from traditional materials. Transmission electron microscopy has shown that the grains of the material actually grow as it is deformed. Current work is focused on obtaining a more complete understanding of this process of grain growth in hope of identifying ways of controlling it. Controlling the modes of deformation will allow someone designing a new micro-device to tailor a material’s mechanical properties to the exact specifications needed for an efficient device.