2014 TMS RF Mehl Medal Symposium on Frontiers in Nanostructured Materials and Their Applications: Keynote Session on Nanomaterials, General Properties and Others
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

Monday 8:30 AM
February 17, 2014
Room: Ballroom E
Location: San Diego Marriott Marquis & Marina

Session Chair: Haiyan Wang, Texas A&M University; Ravindra Nuggehalli , NJIT

8:30 AM  Keynote
Frontiers in Thin Film Epitaxy and Novel Nanostructured Materials: Jagdish (Jay) Narayan1; 1North Carolina State University
    This talk focuses on designing and processing of novel nanostructured materials of controlled size and orientation, and defects and interfaces (1). Thin film growth modes can be precisely controlled to produces zero- one-, two-, and three-dimensional nanostructures. The orientation control requires epitaxy across the misfit scale which is achieved by the paradigm of domain matching epitaxy. The DME paradigm emphasizes the matching integral multiples of lattice planes across the film-substrate interface, where domains are separated by dislocations and the misfit inbetween the integral multiples is accommodated by the principle of domain variation. This talk emphasizes on two-dimensional psuedomorphic metamaterials where the chemical composition is controlled by growth parameters and the structure is determined by the structure of the substrate which provides a template for thin film growth. The thickness (1-5 monolayers) can be controlled manipulating strain and internal thermodynamic free energy. (1) J. Narayan, “Recent progress in thin film epitaxy across the misfit scale,” Acta Materialia 61, 2703-2724 (2013).

9:10 AM  Keynote
Probing Structure, Properties and Dynamics of Nanostructures through Scanning Transmission Electron Microscopy: Stephen Pennycook1; Wu Zhou1; Jaekwang Lee1; Juan-Carlos Idrobo1; Myron Kapetanakis2; Junhao Lin2; Sokrates Pantelides2; 1Oak Ridge National Laboratory; 2Vanderdbilt University
    The aberration-corrected scanning transmission electron microscope (STEM) now allows direct, real space imaging at atomic resolution and low accelerating voltages to minimize damage. In two-dimensional materials such as BN and graphene, atom-by-atom characterization of atomic position, atomic species, chemical bonding and optical and electronic properties is feasible. Furthermore, through direct momentum transfer, the STEM probe can also reveal the dynamics of small clusters, which can be compared to density functional calculations to determine the energy landscape. Examples will be shown of a Si6 cluster in a graphene nanopore and metallic transition metal chalcogenide nanowires which self assemble with ohmic contacts to the surrounding two-dimensional layers. Research supported by DOE BES Materials Sciences and Engineering Division (SJP, JL, STP), ORNL’s ShaRE User Program, sponsored by DOE-BES (J-CI), an ORNL Wigner Fellowship (WZ), NSF DMR-0938330 (WZ, J-CI), DOE grant DE-FG02- 09ER46554 (MK, JL, STP) and the McMinn Endowment (STP) at Vanderbilt University.

9:30 AM  Keynote
Design and Applications of Nanostructured Energy Materials: Sungho Jin1; 1UC San Diego
    There is a strong need for advanced energy materials for harvesting of green energy. Energy materials having controlled nanoscale configurations offer a promise of much improved efficiency. In dye sensitized solar cells, photoanode nanostructures incorporating elongated nano conductors can provide a significant enhancement in the energy conversion performance and reliability. For water splitting hydrogen generation, a very large surface area electrode decorated with a uniform distribution of nanosized photocatalyst particles is desirable. For thermoelectric materials, the formation of nanograined alloy structure with a modulation doped layer is useful for optimizing the thermal conductivity and achieve increased figure of merit. For photovoltaic solar cells and solar thermal devices, nanoscale surface structures are desirable for enhanced light absorption and high performance energy conversion. In this presentation, various means for creating and controlling nanostructures in different types of energy materials will be described, and their implications for technical applications will be discussed.

9:50 AM  Keynote
Nanogenerators for Self-powered Systems and as Active Sensors: Zhong Wang1; 1Georgia Institute of Technology
    We demonstrate a simple, low cost and effective approach of using the charging process in friction to convert mechanical energy into electric power for driving small electronics. The triboelectric nanogenerator (TENG) is fabricated by stacking two polymer sheets made of materials having distinctly different triboelectric characteristics, with metal films deposited on the top and bottom of the assembled structure. Once subjected to mechanical deformation, a friction between the two films, owing to the nano-scale surface roughness, generates equal amount but opposite signs of charges at two sides, respectively. Thus, a triboelectric potential layer is formed at the interface region if the generated triboelectric charges are separated by a small distance; the electrons in the external load are driven to flow for generating an induced potential for screening the triboelectric potential. This is the mechanism of the trioboelectric nanogenerator.

10:10 AM Break

10:30 AM  Keynote
Magnetoelectric Control of Exchange Coupling in Monodomain BiFeO3 Heterostructures : Chang-Beom Eom1; 1University of Wisconsin-Madison
    Multiferroic materials that exhibit coupling of ferroelectric and antiferromagnetic ordering form the basis of exciting heterostructures that can provide electric field control of magnetization. Such structures provide new directions for novel spintronic devices. In particular, the electric field control of exchange bias coupling to a ferromagnetic layer forming one electrode of a magnetic tunnel junction provides unprecedented control. Here we investigate the exchange coupling between monodomain multiferroic BiFeO3 (BFO) and a soft ferromagnetic Co overlayer. We use x-ray magnetic circular dichroism (XMCD) and anisotropic magnetoresistance (AMR) to investigate these heterostructres. We demonstrate that the exchange coupling between BFO and Co occurs without the contribution of domain walls. device applications.This work has been done in collaboration with W. Saenrang, B. A. Davidson, S. Ryu, J. Podkaminer, D. Lee, J. Frederick, T. Kim, S. Baek, M.S. Rzchowski, J. Freeland.

10:50 AM  Keynote
Stress-engineered Self-organized Nanostructure Array Assembly: A Rich Paradigm: Anupam Madhukar1; 1University of Southern California
    Two- and three-dimensional regular arrays of quantum confined nanostructures such as quantum wires and quantum dots constitute a basic and powerful platform for realization of electronic and optoelectronic technologies that underlie information sensing and processing systems for applications ranging from communications to energy conversion and biomedicine. The most successful growth-controlled approach to realizing such architectures to-date exploits engineering surface stress gradients to manipulate atomic migration direction and molecular reactions during growth and growth interruption. In this talk I will address the current status of the subject through illustrative examples of both lattice-matched and mismatched semiconductor combinations focusing on (a) the significance of the kinetics of atomistic processes in controlling the assembly and nature of the resulting quantum nanostructures, and (b) some key issues that require much deeper understanding to enable realizing the full potential of this powerful approach.

11:10 AM  Keynote
Mechanical Behaviors of Heterogeneous Nanostructured Metals: K. Lu1; 1Chinese Academy of Sciences
    In comparison with the strong-but-brittle homogeneous nano-grained metals, heterogeneous or hierarchical nanostructured metals are found to exhibit promising property combinations, such as simultaneous increment of strength and fracture toughness, and of strength and tensile ductility. In this talk, mechanical behaviors of three types of heterogeneous nanostructured metals will be introduced: (i) ultrafine-grains with nano-scale twins, (ii) nano-twinned grains mixed with coarse grains, and (iii) gradient nano-grained (GNG) structures. Mechanical properties including strength, ductility, work-hardening, rate sensitivity, and fatigue behaviors will be discussed with respect to the heterogeneous nanostructures with emphases on the nano-scale size effects. Several examples will be presented for illustrating the correlation between these heterogeneous nanostructures and their mechanical behaviors. Perspectives on heterogeneous nanostructured metals will be addressed as well.

11:30 AM  Keynote
The Principles of Grain Refinement during Severe Plastic Deformation: Terence Langdon1; 1University of Southern California
    The application of severe plastic deformation (SPD) to bulk materials provides an opportunity for achieving exceptional grain refinement to the submicrometer or even the nanometer level. Several SPD processing methods are now available but the most attractive are equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). This presentation examines the principles of grain refinement in these two processing methods with emphasis on the magnitudes of the final grain sizes.

11:50 AM  Keynote
Influence of Length Scales on Precipitation Phenomena in Al Alloys: Tao Hu1; Julie Schoenung1; Enrique Lavernia1; 1University of California, Davis
     Nanostructured metals and alloys have engendered scientific and technological interest, partly due to the discovery of novel deformation mechanisms, which provide a pathway for enhanced mechanical behavior. Much of the original research was conducted using pure metals and binary alloys systems. Recently, however, research has evolved to encompass precipitation-strengthened systems due to the fundamental questions related to the precipitation phenomena in nanostructured alloys that require investigation and the potential for increased mechanical performance via precipitation strengthening. In this lecture we will discuss recent results related to the influence of length scales on precipitation phenomena in Al alloys. Precipitation phenomena will be described in terms of the type, morphology, size and distribution of precipitates as a function of different length scales. In addition, the influence of defects, e.g. dislocations and grain boundaries, on the nucleation and growth of the precipitates at different length scales in precipitation-hardened Al alloys is also addressed.