2014 TMS RF Mehl Medal Symposium on Frontiers in Nanostructured Materials and Their Applications: Nanomaterials for Energy Applications and Carbon Related Materials
Sponsored by: TMS Electronic, Magnetic, and Photonic Materials Division, TMS: Thin Films and Interfaces Committee
Program Organizers: Nuggehalli Ravindra, New Jersey Institute of Technology; Ramki Kalyanaraman, University of Tennessee; Haiyan Wang, Texas A & M University; Yuntian Zhu, North Carolina State University; Justin Schwartz, North Carolina State University; Amit Goyal, Oak Ridge National Laboratories

Thursday 8:30 AM
February 20, 2014
Room: Ballroom E
Location: San Diego Marriott Marquis & Marina

Session Chair: Nitin Chopra, University of Alabama; Ashutosh Tiwari, University of Utah

8:30 AM  Invited
Charged Defect-induced Preferential Scattering for Enhanced Thermoelectric Performance in Few-layered n-Bi2Te3: Apparao Rao1; 1Clemson University
    In the past two decades the development of nano-structuring methods, such as the ball milling-hot pressing, melt spinning-spark plasma sintering, hydrothermal growth-cold pressing, and hot forging processes have improved the figure of merit (ZT) in the state-of-the art bulk thermoelectric (TE) materials. While these methods can enhance the TE performance of p-type Bi2Te3, they proved ineffective for n-type Bi2Te3 due to the inevitable deterioration of its TE properties in the basal plane. Here, we describe a novel chemical-exfoliation spark-plasma-sintering (CE-SPS) nano-structuring process that transforms the microstructure of n-type Bi2Te3 in an exceptional way without compromising its basal plane properties. The CE-SPS processing leads to a significant decrease in the electrical resistivity despite the presence of numerous grain boundaries, mitigates the bipolar effect leading to an upshift of the ZT peak by ~100 K, and stabilizes ZT to a value above 0.8 over a temperature range of ~150 K. The confluence of these highly desirable properties stems from the preferential scattering of electrons at the charged grain boundaries created by the CE-SPS process. In addition, compared to the compatibility factor of the commercial ingot the CE-SPS processed n-type Bi2Te3 exhibits a weak temperature dependence in the range of 300-500 K , thus paving the way for the integration of existing non-traditional TE materials into TE devices.

8:50 AM  Invited
Laser Ablation in Liquids: A Unique Route to Fabricate Hollow Micro/Nanoparticles from Bulk Materials: Douglas Chrisey1; 1Tulane University
    Hollow micro- and nanoparticles are attractive due to the wide range of applications based on their high specific surface area. Laser ablation in liquids has been a subject of intensive research in the past decade, but the particles generated by this method were limited to solid ones. We found that hollow particles could be generated by excimer laser ablation of Al, Cu, Pt, Fe-Ni alloy, TiO2 and Nb2O5 targets in water or aqueous solutions. The hollow particles generally have smooth shells, but may also be aggregated from nano- or even microparticles. Herein we extend the method to other materials and discuss the possibility of laser ablation in liquids as a general approach to fabricate hollow particles directly from bulk materials. The hollow particles are formed on laser-induced bubbles. This mechanism provides the possibility to fabricate hollow particles from other materials and represents a new paradigm for hollow particle fabrication.

9:10 AM  Invited
A New Class of Molecularly-tailored Nanomaterials and Interfaces For Energy Conversion and Thermal Management: Ganpati Ramanath1; 1Rensselaer Polytechnic Institute
    This talk will describe new molecularly-directed synthesis and modification strategies to realize nanomaterials and interfaces for energy and electronics applications. I will first demonstrate a new class of doped-nanothermelectrics obtained by the assembly of surfactant-sculpted nanocrystals of pnictogen chalcogenides and oxides synthesized by a scalable and versatile microwave-solvothermal approach. Sintered nanostructure assemblies exhibit up to 250% higher figure of merit resulting from nanostructuring-induced ultralow thermal conductivities, and doping-induced enhancements in the power factor through control over charge carrier type, concentration and mobility through alterations in defect chemistry and electronic band structure. Property enhancement mechanisms will be discussed based upon electron microscopy, electron and X-ray absorption spectroscopies and first principles theoretical calculations. I will also demonstrate the ability to tune the interfacial thermal conductance by more than an order of magnitude using a nanomolecular layer that alters the interfacial bond chemistry and the vibrational band structure.

9:30 AM  Invited
Atomistic Study of Thermoelectric, Electronic and Optical Properties of Suspended Graphene Nanosheet and Nanoribbons: Sarang Muley1; Ravindra Nuggehalli1; 1New Jersey Institute of Technology
    Non-equilibrium molecular dynamics (NEMD) simulations and Non-Equilibrium Green’s Function (NEGF) formalism have been used to investigate and compare the thermoelectric, electronic and optical properties of a series of both suspended pristine as well as p- and n-type doped 1D zigzag and armchair graphene nanoribbons (GNR) with 2D graphene nano-sheets. Thermoelectric and electronic properties are found to exhibit interesting width dependence. Also, these carbon nanostructures could have enhanced thermoelectric figure of merit (ZT) values at appropriate chemically-doped carrier concentration and operating temperature. Significant role of the quasi-1D geometry in determining the thermoelectric properties of the GNR has been observed. Optical absorption coefficient and refractive indices have been found to be independent of chemical doping (upto 12%) and incident wavelength (300-1000 nm) for single and bilayer graphene. Possessing an extraordinary set of properties, these carbon nanostructures can be promising candidates for high performance thermoelectric and opto-electronic devices.

9:50 AM Break

10:10 AM  Invited
Does Function Follow Form? The Role and Utility of Geometry in Carbon Nanotubes: Prabhakar Bandaru1; 1UC, San Diego
    The synthesis of nonlinear morphologies of nanotubes and nanowires, such as branched and coiled forms, has been widely reported and suggests novel applications, e.g., coiled forms for mechanical springs and electrical inductors, and branched structures for interconnect and switching applications, etc. Such nanostructure formation is also scientifically interesting in that nonlinearity abounds in nature, e.g., DNA based structures are often coiled and a connection could be seen to be made at the nanoscale between carbon based inorganic and organic structures. For application, it would be desirable to have control over the nanostructure morphology and geometry-which has not been achieved, due to an incomplete understanding of their growth mechanisms. In this talk, I will briefly review the forms and growth models in vogue, indicating the critical role of the catalyst and growth ambient. I will then discuss experimental results that indicate utility of such morphologies and whether they confer critical advantages.

10:30 AM  Invited
Improved Interlaminar/Interfacial Fracture Toughness through Polymer Nano-particle Thin Film/Spray Mediated Composites: Ranji Vaidyanathan1; Krishna Bastola1; 1Oklahoma State University
    Polyhedral Oligomeric Silsesquioxane (POSS), and graphene are classes of nano-sized additives that can potentially compete with techniques to improve the interlaminar/interfacial shear strength of carbon fiber epoxy laminate composites and outperform techniques such as interleaving, stitching, z-pinning, or hybridization with micro or nano-sized particles. The present study was undertaken to explore the possibility of modifying the interlaminar interface of carbon fiber epoxy laminate composites at the nanoscale using POSS or graphene oxide dispersed in a thermoplastic polymer carrier such as polyvinyl pyrrolidone (PVP) or starch and applied in the mid-plane of a composite laminate. Improvement of ~100% in the Mode I fracture toughness (GIc) that was observed makes the technique of using very small amounts of POSS or graphene oxide nano-particles (< 0.5% by weight) to modify interlaminar interface, an innovative means to improve the energy absorption capability and interlaminar shear strength of carbon fiber epoxy laminates.

10:50 AM  Invited
Gold Nanoparticle Inside Graphene Shells: Prospects in Sensors and Plasmonics: Nitin Chopra1; 1The University of Alabama
    In–situ growth of graphene on noble metal surfaces is of great importance for applications in chemical and biological sensors and nanophotonics. In this talk, I will be discussing some major advancement made by us in the area of chemical vapor deposition (CVD) growth of graphene shells encapsulated gold nanoparticles (GNPs). This approach utilizes surface oxidized gold nanoparticles for the direct growth of well-controlled graphene shells around it. The growth approach also overcomes the issue of aggregation of nanoparticles during the CVD growth process and allows for the formation of stable dispersion of GNPs. A detailed analysis of morphological evolution and electron/analytical characterization of GNPs will be explained. As a next step, complex architectures of these hybrid nanoparticles are achieved on 1-D nanostructures such as CNTs and semiconducting nanowires. Mathematical modeling of plasmonic behavior, their biofunctionalization, and applications in sensors will be discussed.

11:10 AM  
Carbon Nanotube Coated Conductor Composites: Terry Holesinger1; Raymond Depaula1; John Rowley1; Pallas Papin1; 1Los Alamos National Laboratory
    The development of industrially-scalable processes for aligning very thick coatings of carbon nanotubes (CNTs) on a suitable wire former is a key step in multi-functional CNT coated conductors. Aligned CNT coatings up to 100 microns thick have been prepared by conventional solution coating and wire drawing. We have successfully produced wires that display some of the lowest reported resistivity values for CNT coatings. For our best result, an overall wire resistivity was measured to be 2.12 -cm from which the CNT coating resistivity was calculated to be 5.5 -cm. In terms of conductivity, the composite wire and CNT coating values were 46 and 18 MS/m, respectively. Electron microscopy has been extensively used to identify and eliminate current limiting defects. Prospects for scale-up and application development will be discussed.This work was supported by the Research Partnership to Secure Energy for America (RPSEA) via subcontract 09121-3300-10 and the Chevron Corporation.

11:30 AM  
Optical, Electrical and Electronic Properties of Vanadium Oxides – An Analysis: Chiranjivi Lamsal1; Nuggehalli Ravindra1; 1New Jersey Institute of Technology
    An overview of the optical, electrical and electronic properties of vanadium oxides, VO_2, V_2O_3, and V_2O_5, is presented. The properties are analyzed for various structures, as a function of polarization and temperature, utilizing phenomenological approaches. The first order reversible, insulator to metal (IMT) phase transition of the V-O systems is studied as an effect of temperature change. Electrical and optical conduction mechanisms are interpreted for both metal and insulating states using suitable models. Electronic properties are studied using electronic structure calculation packages.

11:50 AM  
Encapsulating Polymeric Nitrogen in Carbon Nanotubes: El Mostafa Benchafia1; Zafar Iqbal1; Nuggehalli Ravindra; 1New Jersey Institute of Technology
    Polymeric phases of compounds, generally known only in their molecular forms, have been synthesized in minor quantities using High Pressure/Temperature approaches. Here, we present Plasma Enhanced Chemical Vapor Deposition as an alternative to synthesize a polymeric Phase of Nitrogen that can hold at ambient conditions using Carbon Nanotubes as substrate . This long sought-after polymeric Nitrogen is promising to be the highest density energetic material. Simplicity, ease and stability at ambient conditions make our approach very important. FTIR and Raman spectra along with DFT calculations are used to identify the structure and the vibrational frequencies assignment for this polymeric phase.

12:10 PM  Invited
Magnetic Spinel Ferrite Thin Films and Nanostructures: Arunava Gupta1; 1University of Alabama
    There is considerable interest in spinel ferrite films because of their numerous technological applications in areas such as microwave integrated devices and magnetoelectric coupling heterostructures. The growth and properties of epitaxial spinel ferrite films will be reviewed, including our work on films grown by pulsed laser deposition and chemical vapor deposition techniques. Of particular interest are systematic studies on formation of antiphase boundaries in epitaxial NiFe2O4 films grown on different substrates and the accurate determination of the band gap of this material using optical spectroscopy and first principles calculations. In addition to thin films, spinel ferrite nanostructures are being investigated both because of fundamental scientific interest and technological applications arising from the unique properties in reduced dimension. We have synthesized monodisperse nanocrystals and nanostructures of a number of spinel ferrites using facile solution-based methods and investigated their structural and magnetic properties.