This research focuses on the fundamental processes of corrosion and multi-phase diffusion in metal particle polymer composites with functionalized nano behavior. The knowledge attained by this research will enable a new type of MEMS-based corrosion sensor technology that is small-size, tailorable and smart, ultimately allowing the US to better focus financial investments earmarked for infrastructure repair. Experiments will be carried out to (i) understand the fundamental issues associated with the fabrication of polymers with micro- and nano-particle inclusions and (ii) study material performance in simulated corrosive environments. Atomistic simulation is used to study the nanoscale details of diffusion and corrosion in particle polymer composites. The proposed simulations will provide a detailed understanding of the role of the inclusions on the structure of the polymer chains in the matrix and on the transport of corrosive molecules through the composite. Fundamental aspects of diffusion and particle reactions in the composites studied in this work potentially have broad applicability to other sensing technologies. This project will integrate the NSF REU site in the Department of Mechanical Engineering, NSF DUE site for Robert Noyce Scholarships Program, and George Washington Carver program at the University of Arkansas to recruit underrepresented students and interface with STEM K-12 teachers in high-need areas.
Intellectual Merit The ultimate goal of this research is the creation of a micro fabricated corrosion sensor utilizing micro- and nano-technologies. This project deals with the fundamental understanding on the diffusion properties of the corrosion sensing element. By understanding diffusion in and out of the polymeric metal particle composites sensing element, the desired and optimized sensing characteristics can then be designed. However, the methods of experimentally characterizing diffusion properties of nano-materials is difficult and often cost prohibitive due to large material samples needed for traditional testing methods. Thus, experimental and computation techniques were employed complementarily to help gather the understanding of its fundamental scientific processes. Experimental: An optical scanning technology (using widely available flat-bed scanners) was implemented to characterize the diffusion of corroding agents and by-products into and out of the micro/nano-particle polymer composites. Separately, automated video imaging and processing was used to characterize the swelling of the polymers immersed in supercritical carbon dioxide. This was used to swell the polymer to aid diffusion in and out of the composite. Both techniques were successfully developed, among others, to allow the study of the composites. Numerical: In terms of simulation, the completion of the pure-polymer (PDMS) and metal-polymer codes was followed by the much more challenging problem of polymer cross-linking and how it relates to experimental methods. Molecular Dynamics Simulation was used to track every single molecule of the polymer and polymer-metal composites to understand how corroding agents penetrates the material. The polymer used (silicone rubber) is an ultra large molecule due to the cross-linking of shorter lengths of the same polymer to form a solidified polymer composite. Thus, the successfully developed simulation codes allowed the study of this process (cross-linking) and how it affects the diffusion behavior of the resulting composites. Broader Impacts The annual cost of corrosion related issues is over 5% of the nation's Gross Domestic Product. Even if a small fraction of corrosion can be prevented or protected by health monitoring systems, it would represent billions of dollars of annual savings and increasing the safety of our civil infrastructures. However, to make such a health monitoring system feasible, it must require minimum manual (field worker) efforts in order to be cost-effective and practical. Thus, the availability of a smart, low-cost, and mass-producible corrosion sensor is critical to the success of corrosion-based infrastructure health monitoring and prevention regime. During the course of this project, recruited and/or graduated both 7 graduate (6 M.S. and 1 Ph.D.) and 8 undergraduate (5 from under-represented groups) students to train future scientists and engineers while solving one facet of the problem of aging infrastructure. At the same time, the PI has undertaken summer workshops on micro/nano/electronics technologies to future STEM teachers from the University of Arkansas Masters in Arts for Teaching students. The PI also established connection with the researchers at the Universidad Interamericana de Puerto Rico, BC-campus, to bring-forth the science and technology of this research as part of future educational and research partnership between the two institutions.
