Formation of Palladium Structures Combining Electrospinning and dc Sputtering
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0948-B05-12
Formation of Palladium Structures Combining Electrospinning and dc Sputtering Wilfredo OtaÒo1, Ariel O. Otero1, JosÈ M. OtaÒo2, Carlo S. OtaÒo2, Jorge J. Santiago3, and VÌctor M. Pantojas1 1 Mathematics-Physics, University of Puerto Rico at Cayey, 205 A. Barcelo Avenue, Cayey, 00736, Puerto Rico 2 Mechanical Engineering, University of Puerto Rico at Mayaguez, Mayaguez, 00680, Puerto Rico 3 Electrical and System Engineering, University of Pennsylvania, 200 S. 33rd. street, Philadelphia, PA, 16802 Abstract Electrospinning and dc sputtering techniques were combined for the formation of a variety of nano-to-microscale structures of palladium. Poly(ethylene oxide) fibers prepared by electrospinning were used as templates for the dc sputtering of palladium. Heating the fibers to 320 ∞C in air eliminated the central polymer core (fugitive phase) resulting in the formation of open and closed core fibers, depending on the amount of metal deposited. The formation of the structures is the result of sputtering being a line-of-sight deposition technique. Palladium is preferentially sputtered on top of the fiber part facing the target, resulting in a non-uniform deposition. Furthermore, it is proposed that the deposition of palladium on top of the fibers results in the nucleation of palladium crystals growing outward perpendicular to the fiber surface and producing interesting nanoscale features resembling thorns and scales. The fibers were analyzed by Scanning Electron Microscopy and X-ray Diffraction.
Introduction Palladium has important applications in hydrogen sensors, purification membranes, catalysis, templates for magnetic materials and others [1-4]. In hydrogen sensors technology Pd is chosen as the active sensing element since it can adsorb up to 900 times its volume in hydrogen gas. Its formation in structures with nanoscale dimensions is an important consideration in enhancing the performance of many of the devices developed for many of these applications (increasing the surface to volume ratio). Several methods have been used to form palladium nanotubes. Sun Y. et. al., for example, used a galvanic replacement reaction and was able to replace the atoms of Ag nanowires with Pd by refluxing with palladium nitrate [5]. This method limited the length of the nanotubes to less than 2 µm. In another work, Yu S. et. al., used an electroless plating method to deposit palladium within the pores of track-etched polycarbonate membrane [6]. The nanotubes produced by this method were composed of granular walls and where also limited in length. Nanostructures of palladium have been previously formed with the use of templates. The template technique entails the deposition of the desired material within the cavities of a host,
usually within the pores of a porous membrane [7]. Steinhart et. al. used ordered porous alumina membranes which were wetted with a solution containing poly(D,L-lactide) and palladium acetate [8]. Subsequent annealing of the membrane resulted in the degradation of the acetate to form palladium tu
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