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Undergraduate Research Opportunities Program

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End date: 2009 × Start date: 2009 × search.filters.applied.f.isOrgUnitOfPublicationTitle: College of Engineering × search.filters.applied.f.isOrgUnitOfPublicationTitle: School of Materials Science and Engineering ×

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Zinc Oxide coated Carbon Nanotubes as Piezoelectric Nanogenerators

2009-12 , Mason, Celeste

Piezoelectric nanogenerators were created using two designs: coating carbon nanotubes (CNTs) grown on a silicon wafer substrate with a thin film of zinc oxide (ZnO), coupled with an additional gold-coated CNT grown wafer to act as an electrodes and coating carbon nanotubes (CNTs) grown on carbon fiber with each type of coating to form flexible electrodes. The CNTs on all samples were grown using a standard recipe, with thermally evaporated iron as catalyst. ZnO deposition techniques such as RF sputtering and ion-assisted deposition were used. Gold deposition was accomplished by thermal evaporation and RF sputtering. Once electrodes were combined, preliminary electrical testing resulted in measurement of current densities of up to 4.2x10-7 A/cm3. Additional electrical measurements indicated that the current generated was the result of piezoelectric behavior of the ZnO coating. These values may be increased with better penetration of both gold and ZnO coatings during deposition on the CNTs. Improvement of film quality, such as gold adhesion and ZnO crystal orientation, may also increase current generation.

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Modeling and Simulation of the Impact Response of Linear Cellular Alloys for Structural Energetic Material Applications

2009-05-04 , Jakus, Adam

We investigate the deformation and fracture as well as stress transfer behavior of 250 maraging steel linear cellular alloys (LCAs) undergoing high velocity impact upon a rigid target. Of paramount importance for application as a ballistic delivery mechanism for thermite powders, is the ability to transfer stress along the inner length of the cell walls. Additionally, outward fragmentation of the LCA body upon impact must be controlled. Parameters for a Johnson-Cook strength model of 250 maraging steel are determined in conjunction with 3-dimensional Lagrangian based finite element analysis on a solid cylinder. These parameters are then applied to four, 25% theoretical density LCA geometries: hollow cylinder, pie, reinforced pie, and 9-cell waffle. Verification of the validity of the Johnson-Cook parameters determined from the solid cylinder experiments and simulations is analyzed through comparison of experiments of the four LCA geometries, produced using a direct reduction technique with corresponding simulations. Upon verification of the Johnson-Cook strength model for maraging steel, the deformation and fracture as well as the stress transfer response of the LCAs during impact is analyzed. Through transient analysis of finite element simulations, it has been determined that the 9-cell waffle geometry displays optimal stress transfer behavior as well as limited outward fragmentation.

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