UNIVERSITY OF ILLINOIS
Grant: $398,521 - National Science Foundation - Jun. 15, 2009
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Award Description: This research project integrates experiments and modeling to develop physics-based predictive models for the problem of room temperature creep in nanocrystalline metallic films. The novel experiments aim at extracting directly the grain-boundary (GB) sliding viscosity and the GB diffusivity. Model experiments augmented with atomic force microscopy measurements will obtain the displacement jumps as a function of time. The measured local GB parameters will be incorporated in cohesive models for the GBs in a multiscale model for polycrystalline Au to quantify the effect of inelastic GB mechanisms on the creep response of nanocrystalline Au films. While other homogenization schemes use the macroscale material behavior to fit microscale parameters, the proposed multiscale experimental/modeling protocol employs macroscale experiments to validate the multiscale modeling predictions. This project can have significant technological and educational impacts. Several thin film applications, such as radio frequency microelectromechanical systems, variable capacitors and tunable filters involve fixed-fixed metal structures that suffer from loss of mechanical stiffness due to creep at room temperature. Quantification of the GB mechanisms in nanocrystalline metals will allow for mitigating strategies to prevent room temperature creep but maintain the high yield strength that is controlled by dislocation crystal plasticity. Once perfected, the experiments will be integrated in the PI's experimental course 'Nanoscale Contact Mechanics' that provides theoretical and experimental education and training to graduate students by following a 'bottom-up' methodology in mechanics.
Project Description: OVERALL GOAL: The focus of our project activities in this quarter is to generate a first, physics-based, predictive model (two-dimensional) for the creep response of a nanocrystalline metals. At the same time are conducting experiments on the creep response of nanocrystalline metal films (gold and nikel.) EXPECTED RESULTS: 1. First level model for the prediction of the long term mechanical response of nanocrystalline metals. 2. Experimental data to develop trends and physical mechanisms to be integrated in the modeling effort in the second and later quarters of this project. This project will support two research assistants who are also pursuing their Ph.D. degrees in Mechanical Engineering at UIUC. Their research work is important in advancing our current knowledge and technology on nanocrystalline thin film metals impacting microscale sensor and thin film electronics technologies. The results of this work will have also direct application to bulk nanocrystalline metals that are currently explored as tougher and stronger materials compared to existing metals. This project will generate validated models for the long term mechanical behavior of a new class of metals which if transitioned to industry they will have a pervasive effect in many consumer applications, from the automobile to the aerospace industry. The current hurdle in the application and industrial transition of nanocrystalline metals is that, although they are strong, they are subject to creep which must be understood and suppressed before these materials are incorporated in consumer products.
Jobs Summary: N/A (Total jobs reported: 0)
Project Status: Less Than 50% Completed
This award's data was last updated on Jun. 15, 2009. Help expand these official descriptions using the wiki below.
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