Controlled Synthesis, Processing and Applications of Structural and Functional Nanomaterials: One Dimensional Nanomaterials I
Sponsored by: MS&T Organization
Program Organizers: Kathy Lu, Virginia Tech; Xudong Wang, University of Wisconsin - Madison; Eugene Olevsky, San Diego State University; Gurpreet Singh, Kansas State University; Nitin Chopra, The University of Alabama; Pu-Xian Gao, University of Connecticut; Jianyu Liang, Worcester Polytechnic Institute

Tuesday 8:00 AM
October 18, 2011
Room: C123
Location: Greater Columbus Convention Center

Session Chair: Gurpreet Singh, Kansas State University

8:00 AM  Invited
One-Dimensional ZnO Nanostructures for Photonic and Optoelectronic Applications: Min Gao1; 1Peking University/Kent State University
    In this paper, we summarize our recent efforts in exploring the potential of 1D ZnO nanostructures in photonic and optoelectronic applications. We demonstrate high waveguiding efficiency (>99%), ~70 meV vacuum Rabi splitting indicating strongly enhanced light-matter interaction, >3000 quality factor of ZnO nanorod cavities (compared to <221 for DBR-based planar ZnO microcavities), and the first observation of electron beam excited lasing behavior in ZnO nanostructures. We also show >60 nA photocurrent and >60 mV photovoltage in self-powered two-terminal devices of individual ZnO nanowires. In electrically powered ZnO nanodevices, only moderate temperature increase and emission redshifts were observed for the interesting diameter range for photonic applications. Above results demonstrate that multifunctional devices can be fabricated and integrated based on monotype 1D ZnO nanostructures and simple device structure. We will also report site-specific multi-stage growth of ultrafine ZnO nanorods/nanowires, which enables the integration of different device types along the nanostructure axis.

8:40 AM  
One-Dimensional Nanostructures of Transition Metal Oxides with Large Aspect Ratios: Haitao Zhang1; Padmanabha Chavvakula1; 1UNC Charlotte
    Transition metal oxides (TMOs) including WO3, MoO3, and V2O5 are a group of functional materials with wide applications in smart devices, and batteries, etc. One-dimensional (1D) nanostructures of WO3, MoO3, and V2O5 have been synthesized using low pressure chemical vapor deposition. 1D TMO nanostructures with extremely high aspect ratios have been developed with shapes of wires or belts. The diameters or thicknesses of these TMO nanostructures are about 50-500 nanometers, and the lengths range from tens microns to several millimeters. The formation of these 1D nanostructures is explained by the vapor-solid mechanism. The as-synthesized samples were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and other techniques. These TMO 1D nanostructures with large aspect ratios are good candidates to fabricate single nanostructure based devices. The electric and optical properties of these oxide nanostructures will be demonstrated.

9:00 AM  
Low Temperature Synthesis of Boron Carbide Nanowires with Multiple Twinning: Zhe Guan1; Timothy Gutu1; Terry Xu1; 1University of North Carolina at Charlotte
    Boron carbide nanowires, a promising class of high temperature thermoelectric nanomaterials, were synthesized by co-pyrolysis of diborane and methane in a low pressure chemical vapor deposition system. Nickel and iron were effective catalytic materials. The synthesis was realized at relatively lower temperatures, with 879 oC as the lowest one which is approximately 200 oC lower than common reported temperatures. Electron microscopy analysis showed that the nanowires had diameters between 25-80 nm and length up to 10 µm. The nanowires had single crystalline boron carbide cores and thin amorphous oxide sheaths. Both transverse twins and axial twins with twin planes as {101}h-type were observed. Growth models were discussed. For example, the growth of nanowires with axial twins can be attributed to a vapor liquid solid (VLS)-assisted twin-plane reentrant edge (TPRE) mechanism. These twinned nanowires are great coupons for studying of nanoscale transport properties, especially on understanding the boundary scattering effects.

9:20 AM  
Experimental and Theoretical Analysis of Spark-Plasma Sintering Mechanisms: Eugene Olevsky1; William Bradbury1; Wei Li1; Cristina Garcia1; Randall German1; 1San Diego State University
    Spark-plasma sintering mechanisms of powder particle coalescence and consolidation are analyzed at both microscopic and macroscopic levels. It is shown that for conductive metal powders the appearance of significant temperature gradients in the inter-particle contact areas is possible in the presence of metal oxides at the particle boundaries, while oxide-free metallic systems enable rapid heat transfer within the particle volumes. Fritting and channeling phenomena are introduced as a possible reason of significant Joule heat generation with limited heat conductivity within the oxidized particle contacts. The spark-plasma sintering densification mechanisms are investigated by a novel Multi-Step Pressure Dilatometry (MSPD) approach allowing the determination of the material strain rate sensitivity without cumbersome interruptive grain structure assessment. The MSPD technique is utilized for the comparative analysis of the densification of model powder systems under the same pressure and temperature conditions in the electric current-assisted and electric-current isolative environments.

9:40 AM Break

10:00 AM  Invited
Carbon Nanotube Coatings Laser Power and Energy Measurements: John Lehman1; 1National Institute of Standards and Technology
    Carbon nanotube (CNT) bearing films and composites present new opportunities for our next generation of standards for laser power and energy measurements. In addition to material processing, I will address the interaction of light and CNTs and compare CNTs to other carbon and nano-fractal materials. I will present examples of coatings prepared at NIST[1] and elsewhere such as CNT bearing films, vertically aligned CNTs, and composites consisting of polymer-derived silicon carbon nitride and CNTs. The topology of black materials and design goals for creating the nanotube coatings for laser exposures approaching 15 kW/cm2 will be presented. Measurement results from practical devices will be presented such as spectral responsivity, reflectance, ultraviolet aging and laser-induced damage. [1] NIST is The National Institute of Standards and Technology in Boulder, Colorado.

10:40 AM  Invited
Development of Nanostructured Composite Electrodes for All Solid-State Lithium Ion Batteries: Conrad Stoldt1; SeHee Lee1; James Trevey1; Hector MacPherson1; Brian Francisco1; 1University of Colorado
    Metal sulfide nanoparticles are being developed as high capacity active materials in nanostructured composite cathodes for all solid-state lithium ion batteries. This talk will detail our efforts to design and synthesize sub 500 nm particles using both the microwave synthesis and ball milling approaches. Solid-state, nanostructured composite electrodes containing active material, electrolyte, and conductive additive are developed and evaluated in an all solid-state lithium battery architecture for energy and power density. Notably, active materials of smaller dimensions show improved lithium ion diffusion kinetics at both room and elevated temperatures. In addition, long cycle life is demonstrated in all solid-state lithium batteries without appreciable loss of capacity. In-situ Raman spectroscopy measurements are presented to connect observed changes in electrode structure to battery performance.

11:20 AM  
Functional Metal Oxide Nanowires and Nano-Heterostructures: Sanjay Mathur1; Hao Shen1; Thomas Fischer1; Robin Hagen1; Ralf Müller1; Jun Pan1; 1University of Cologne
    One dimensional inorganic materials are gaining increasing attention because of their unique structural features and interesting functional properties. Given the structural stability, they show promising application potential in vacuum as well as in oxidizing atmospheres, which provides them a competitive edge over their carbon-based counterparts. A number of synthetic procedures have been developed and demonstrated for 1D nanostructures that have led to intriguing morphological variations (wires, tubes, belts, rods, etc.), however the control over radial and axial dimensions remains a continuing challenge. In addition, the choice of material is rather limited. We have developed a generic approach for the size-selective and site-specific growth of nanowires by combining vapor-liquid-solid approach with the chemical influence of molecular precursors. In particular, synthesis and structural characterization of SiCN@Ge, SnO2@Sn, ZnO@Si, and CdS@TiO2@SnO2 will be presented and their application potential will be discussed. In addition, hyperbranched structures grown by sequential CVD processes will be presented.

11:40 AM  Student
Synthesis and Spectroscopic Characterization of Si(B)CN Composite Nanowires: Romil Bhandavat1; Gurpreet Singh1; 1Kansas State University
    High temperature oxidation resistant polymer-derived ceramic Si(B)CN composite nanowires were synthesis through controlled pyrolysis of a novel boron-modified liquid polymer on the surfaces of individual multiwall carbon nanotubes. Chemical and structural characterization was performed by use of a range of spectroscopic techniques: presence of graphene like carbon, BN, SiC, Si3N4 phases in the ceramic shell was confirmed by Raman, Fourier transform infra-red, nuclear magnetic resonance and X-ray photoelectron spectroscopy. Electron microscopy and x-ray analysis revealed presence of a uniform non-crystalline Si(B)CN coating on individual nanotubes for all specimen processed below 1400C. Thermogravimetric analysis revealed high temperature stability of these nanowires in air. Possible applications include bulk spray coatings for laser thermal detectors and high temperature sensors.