School of Engineering

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  • William Nix

    William Nix

    Lee Otterson Professor in the School of Engineering, Emeritus

    BioI have been engaged in the study of mechanical properties of materials for nearly 50 years. My early work was on high temperature creep and fracture of metals, focusing on techniques for measuring internal back stresses in deforming metals and featuring the modeling of diffusional deformation and cavity growth processes. My students and I also studied high temperature dispersion strengthening mechanisms and described the effects of threshold stresses on these creep processes. Since the mid-1980's we have focused most of our attention on the mechanical properties of thin film materials used in microprocessors and related devices. We have developed many of the techniques that are now used to study of thin film mechanical properties, including nanoindentation, substrate curvature methods, bulge testing methods and the mechanical testing of micromachined (MEMS) structures. We are also known for our work on the mechanisms of strain relaxation in heteroepitaxial thin films and plastic deformation of thin metal films on substrates. In addition we have engaged in research on the growth, characterization and modeling of thin film microstructures, especially as they relate to the development of intrinsic stresses. Some of our recent work dealt with the mechanical properties of nanostructures and with strain gradients and size effects on the mechanical properties of crystalline materials. Our most recent work deals with the mechanical properties of lithiated nanostructures that are being considered for lithium-ion battery applications.