Nanotechnology for Energy, Healthcare and Industry : Session II
Program Organizers: Gary Pickrell, Virginia Tech; Suveen Mathaudhu, U.S. Army Research Office; Wolfgang Sigmund, University of Florida; Jud Ready, Georgia Institute of Technology; George Wei, Osram Sylvania; Ke Wang, Virginia Tech; Zhiwei Shan, Xi'an Jiaotong University; Alpesh Shukla, Lawrence Berkeley National Laboratory; Nitin Chopra, The University of Alabama; Sudipta Seal, Univ of Central Florida; Navin Manjooran, Siemens Corporation; Julia Greer, California Institute of Technology
Wednesday 2:00 PM
October 19, 2011
Room: C125
Location: Greater Columbus Convention Center
Session Chair: Navin Manjooran, Siemens Corporate Technology; Nitin Chopra, The University of Alabama Tuscaloosa
2:00 PM
Multi-Functional Nanoscale Heterostructures Derived from 1-D Nanostructures: Nitin Chopra1; 1The University of Alabama
The research in heterostructures evolved with invention of transistors utilizing thin film multilayer structures. However, with the increasing demands of multi-functionality and high density packing of structures on substrates, it is desired to achieve nanoscale heterostructures combining different nanostructures. This is now not only becoming critical for nanoelectronics/magnetic but also for emerging area of alternative energy. In this talk, I will focus on our unique approach to develop nanoscale heterostructures comprised of 1-D nanostructures and nanoparticles by coupling chemical vapor deposition method and surfactant-free chemical approach. These heterostructures are thoroughly studied for their growth mechanisms and physico-chemical characteristics using high resolution electron microscopy, spectroscopy, and diffraction methods. Finally, these heterostructures are demonstrated to be efficient solar-active substrates. For example, CuO nanowire-Co3O4 nanoparticles showed unique optical characteristics leading to enhanced absorbance in visible light. Such nanoscale heterostructures-based devices can have a huge impact on energy technologies as will be discussed here.
2:40 PM
Controlling Electron Transport in CNT-Supported Organometallic Catalysts: Yuan Lu1; Bruce Hinds1; Matthew Beck1; 1University of Kentucky
Carbon nanotubes (CNTs) hold great potential as supports for organometallic catalysts for a range energy applications. Experiments have suggested that the atomic configuration of the molecule-CNT attachment bonds has an important effect on catalytic activity due to its influence on electron transport between the CNT and the molecule. Existing experimental characterization techniques do not clearly reveal details of this effect. Here we use electronic structure calculations and a quantum transport hopping model to examine different binding attachments. We show how the electronic structure of the CNT-molecule bond and nearby molecular bonds does, in fact, control the electron transport between CNT and molecule.
3:00 PM
Anodization of Aluminum-Titanium Alloys for Solar Cell Applications: Neslihan Alpay1; George Demopoulos1; Mathieu Brochu1; 1McGill University
Titania (TiO2) is deposited in the form of nanostructures such as nanoparticles, nanowires or nanotubes to perform as a semiconducting layer in dye-sensitized solar cells. The substrate is of crucial importance to collect the electricity. Typical substrates used for this application are conducting glass or plastics and steel. Aluminum alloys are not considered as ideal substrate to collect electricity due to the presence of the surface oxide layer that acts as insulator. In this research, aluminum-titanium binary alloys are fabricated using powder metallurgy route, which includes powder mixing and spark plasma sintering. After producing the convenient microstructures, Al alloys are anodized in oxalic acid (H2C2O4) to form anodic oxide (Al2O3) and TiO2 phases. X-ray diffraction (XRD) analysis is carried out to identify the phases, scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) analysis are performed to examine and compare the surface structures of the samples.
3:20 PM Break
4:00 PM
Highly Active Porous Catalysts Fabricated by Attachment of Metal Nanoparticles on Hierarchical Carbon Structures: Hema Vijwani1; Sharmila Mukhopadhyay1; 1Wright State University
The effectiveness of catalysts can be significantly enhanced if surface area in a given volume is increased by the creation of hierarchical nanostructures. This concept is demonstrated here in the Palladium-graphite system. Pd nanoparticles are deposited on porous carbon-foam substrates whose surface area has been increased by orders of magnitude through the attachment of carbon-nanotubes. This type of structure can lead to unprecedented miniaturization of catalytic devices since a very small amount of precious metal can be used to provide high level of surface activity in very compact volume. Potential devices include sensors, water-purification systems, fuel-cell electrodes and hydrogen storage devices. In this project, fabrication issues of these structures will be presented along with microstructure and spectroscopic analysis. Electrochemical behavior and water purification capabilities of these structures are being investigated in collaboration with other groups, and initial results are very encouraging, indicating extensive application potential of these structures.
4:20 PM
Fabrication of P-Type Silicon Optical Fiber: Adam Floyd1; Brian Scott1; Ke Wang1; Gary Pickrell1; 1Virginia Tech
Fabrication of silicon optical fibers with p-type silicon cores is experimentally demonstrated. In addition, optical and material characterizations of these fibers are presented. The fabricated fibers have outer diameters from 200 µm to 1 mm and inner diameters from 10 to 200 µm. Crystal orientation analysis using Electron Backscatter Diffraction shows that the core is polycrystalline along the fiber axis. Energy dispersive spectroscopy and secondary ion mass spectrometry analysis verifies the p-type silicon core with a boron doping level of 8.48 x 1018 /cm3.
4:40 PM
Nanoscale Carbon in Metals for Energy Applications: David Forrest1; Lourdes Salamanca-Riba2; Lloyd Brown3; Jennifer Wolk1; Peter Joyce3; X. Jie Zhang1; 1Naval Surface Warfare Center; 2University of Maryland; 3United States Naval Academy
Recent advances in nanomanufacturing have made it possible for large amounts (> 5 wt.%) of nanoscale carbon to be retained in solid solution in different metals including aluminum and copper. The carbon is highly stable despite its presence not being predicted in phase diagrams, and it remains dispersed after remelting and resolidification. These nanomaterials, termed “covetic” by Third Millennium Metals LLC, display some highly unusual characteristics that are not well-understood: 1. The carbon is detectable by EDS but not by analytic methods such as LECO and GDMS; 2. Nanoscale carbon raises the melting points and surface tension; 3. Warm-worked and cold-worked strengths are higher; 4. When warm-worked they are more strongly textured and have significantly finer grains; 5. Thermal conductivity is enhanced in the working direction; and 6. Electrical conductivity is increased in aluminum. This presentation provides recent results in our ongoing characterization of copper and aluminum covetic materials.
5:00 PM
Novel Catalytic Behavior of Ultra-Small Ceria Nanoparticles for Water Splitting through DFT Investigation: Xing Huang1; Matthew Beck1; 1University of Kentucky
Experiments show that ultra-small ceria nanoparticles (CNPs) (<5nm in diameter) exhibit enhanced oxygen storage capacity and autocatalytic activity over bulk ceria, agglomerated clusters, and larger diameter nanoparticles. Using DFT calculations, we show that 1-2 nm CNPs are super-oxidized under both O-lean and O-rich conditions, in direct contrast to the reduced state of bulk ceria, extended ceria surfaces, or larger CNPs. Ultra-small CNPs are found to exhibit stable molecular oxygen species chemically bonded at surfaces. These surface oxygen molecules suggest new catalytic behavior of ultra-small CNPs that involve the complex interaction between water molecules and surface-bonded molecular oxygen species, as opposed to the oxygen-vacancy controlled catalytic behavior in bulk ceria systems. Following this implication, we will show the significant impact of these structures on the catalytic mechanism of water splitting at ultra-small CNPs.