Advances and Discoveries in Non-equilibrium Driven Nanomaterials and Thin Films: Nanocomposites
Sponsored by: TMS Functional Materials Division, TMS: Energy Conversion and Storage Committee
Program Organizers: Ritesh Sachan, Oklahoma State University; Srinivasa Rao Singamaneni, University of Texas at El Paso; Amit Pandey, Lockheed Martin Space; Nuggehalli Ravindra, New Jersey Institute of Technology

Tuesday 2:00 PM
February 25, 2020
Room: Solana
Location: Marriott Marquis Hotel

Session Chair: Srinivasa Rao, University of Texas, El Paso


2:00 PM  Invited
Surface Chemistry Evolution in Ti-BNNT System Processed by SPS and its Correlation to Physico-chemical and Mechanical Properties: Sudipta Seal1; Tamil Selvan Sakthivel1; Jenniffer Bustillos2; Pranjal Nautiyal2; Aravind Agarwal2; 1University of Central Florida; 2Florida International University
    Composite borides and nitrides are extensively used in several industrial applications as they have extreme corrosion and wear resistance, electrical and thermal properties. The important properties of composite arise due to the existence of the resultant binary and ternary phases namely Ti-N, h-BN, Ti-B-N, etc. The material of interest is the titanium alloy (α+β) with Al and V alloying elements reinforced by Boron Nitride Nanotubes (BNNTs) prepared using Spark Plasma Sintering. In this system, we have explored to understand the evolution of chemical interactions and changes in features during thermal treatment. Detailed X-ray photoelectron spectroscopy (XPS) with imaging/mapping was performed to obtain the reaction phases between BNNT and titanium matrix and resulting morphological features were observed with microscopy. It appears that the nature of any chemical interaction in the system is strongly due to the extent of any physicochemical interactions which occurs at the interface of nanotubes and titanium matrix.

2:30 PM  
Enhanced Field Emission of CNT-W Nanowire Hierarchical Emitters: Narasimha Pulagara1; Gurjinder Kaur1; Indranil Lahiri1; 1IIT Roorkee
    Hierarchical structures have good potential for practical field emission applications. These emitter structures help to provide a high current density at low operating voltage and an excellent current stability for long periods. In the present work, hierarchical structures have been prepared by growing carbon nanotubes (CNTs) on W nanowires. W nanowires were synthesized on W foil and CNTs were grown on synthesized W nanowires by chemical vapor deposition (CVD) technique. Tungsten nanowires were chosen to prepare hierarchical field emitter structures because of high mechanical strength, high chemical and thermal stability and large electronic emissivity of W nanowires. Fabricated CNTs/W nanowires were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) characterization techniques to understand their structures and morphologies. These hierarchical structures were used as cathode to evaluate their performance as field emitters.

3:00 PM  
Metastable Silicon Nanocomposites via Plasma Synthesis and Spark Plasma Sintering: Steven Herzberg1; Devin Coleman1; Christian Roach1; Sabah Bux2; Suveen Mathaudhu1; Lorenzo Mangolini1; 1University of California, Riverside; 2Jet Propulsion Laboratory/California Institute of Technology
    Pervasively metastable materials have been shown to have enhanced and unique properties over their traditional equilibrium phases. These enhancements have largely been demonstrated in thin films, however “bulk” processing methods have yet to be sufficiently explored. This project explores a unique approach for creating pervasively metastable, bulk nanocomposite materials via low pressure, non-thermal plasma synthesis of non-equilibrium nanoparticles and the subsequent consolidation by spark plasma sintering (SPS). By using silane and methane precursors, plasma synthesis is used to create amorphous, non-stoichiometric silicon carbide nanopowders. SPS consolidates and crystallizes the nanopowder into a bulk silicon-silicon carbide nanocomposite. The silicon carbide remains dispersed within the silicon matrix, allowing for the formation of metastable nanostructures with unique functional properties that cannot be created through conventional powder processing techniques. The effects of these nanostructures on the thermoelectric properties of the silicon-silicon carbide system are explored.

3:20 PM  
Heat Capacity and Free Energy of Ni-Fe Nanocrystals: Stefan Lohaus1; Michel Johnson2; Peter Ahnn1; Mary Anne White2; Brent Fultz1; 1California Institute of Technology; 2Dalhousie University
    The thermodynamic stability of fcc nanocrystalline Ni-Fe with respect to a control sample with larger crystallites was studied through heat capacity measurements from 0.5 - 300 K. The heat capacity, dominated by phonons, was integrated to obtain the temperature dependence and grain size dependence of the enthalpy, entropy, and free energy. The nanomaterial, with an average crystallite size of 6 nm, was synthesized by high energy ball milling. It was also used in prior work to measure the phonon density of states. Vibrations cause a larger heat capacity of the nanomaterial, resulting in an excess entropy with respect to the control sample. The nanomaterial also has an excess enthalpy from grain boundaries and defects of approximately 2 kJ/mol. This excess enthalpy causes the free energy of the nanomaterial to exceed that of large-grained material, and entropic effects are not sufficient to alter significantly the relative stability of the nanomaterial.