Use of nanoparticles and nanotubes for the development of high-performance nanoresins and nanocomposites

Gudapati, Vamshi Mohan
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[Honolulu] : [University of Hawaii at Manoa], [May 2011]
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In this study, a brittle epoxy polymer resin has successfully been toughened and strengthened by very small concentrations of diamond and SiC nanoparticles as well as Nanodiamonds (collectively called "nanoparticles" here). The tensile stress-strain response (based on the ASTM tensile tests for polymers) and the fracture energy release rate, GIC, (based on the ASTM Single-Edge-Notched-Bending, SENB, tests for polymers) of neat and nano-reinforced epoxy polymer were characterized over a range of "nanoparticle" concentrations. In addition to the large-scale improvements in mechanical properties, the nanoresins developed in this work also showed other superior multifunctional performances such as structural damping and acoustic properties. In the later part of this study, horizontally (in-plane, i.e., completely parallel to the surface) aligned multi-walled carbon nanotube (MWCNT with diameters of less than 100 nm) nanocarpet-nanotapes are developed as reinforcements to enhance the overall performance of resins, adhesives, and composites, globally (when it is interleaved within the composites to cover or "carpet" the entire surface of the parts) or locally (when it is used to locally reinforce the locations of joints, cut-outs, holes, etc, where stress concentrations exist). In addition to large scale improvements in mechanical properties, the nanocomposites developed in this work also showed enhanced multifunctional performance such as damping, electro-magnetic interference shielding (EMI), coefficient of thermal expansion (CTE), and Thermal Conductivity. Finally, we report the use of chemically modified vertically aligned carbon nanotube nanoforest nanofilm directly assembled on carbon paper as Gas Diffusion Layers (GDLs) for fuel cells. GDLs enhance the delivery of gases to the catalyst layers by controlling the water in the pore channels while simultaneously completing the electrical and electronic circuits needed to deliver the power generated by the Proton Exchange Membrane (PEM) Fuel Cells. Current carbon paper products for the GDLs offer limited hydrophobic characteristics which are often enhanced by a Teflon® PTFE coating on the surfaces of the carbon paper. Our invention substantially improves both the hydrophobic nature of the carbon paper and its porosity in the fuel cell as well as enhances the electrical conductivity and the electron/proton conduction. While the GDLs prepared by current technology have major performance losses at elevated temperatures and low humidities, our modified GDL based on the nanoforest nanofilm carbon paper technology, developed in this work, shows no performance loss when operated at elevated temperatures with lower humidity conditions in additon to the enhancement in peak power density.
Ph.D. University of Hawaii at Manoa 2011.
Includes bibliographical references.
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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Mechanical Engineering.
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