Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session T30: Materials: Synthesis, Growth and Processing (Bulk & Films) |
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Sponsoring Units: DCMP Chair: Yunfeng Shi, Rensselaer Polytechnic Institute Room: C147/154 |
Wednesday, March 23, 2011 2:30PM - 2:42PM |
T30.00001: ABSTRACT WITHDRAWN |
Wednesday, March 23, 2011 2:42PM - 2:54PM |
T30.00002: UHV-Compatible Aerosol-Molecule Beam Deposition Source for Organic Electronic Films Levan Tskipuri, Qian Shao, Janice Reutt-Robey The rapidly advancing technologies of flexible electronics and organic photovoltaics have triggered strong interest in new methods for electronic materials deposition from the solution phase. Materials deposition based upon direct aerosol flow offers advantages both for fundamental studies of film growth and analysis and for industrial preparation of high-performance materials. We describe an aerosol deposition source based upon a spray-jet molecular beam technique. The source produces a supersonic molecular beam of solutes (such as C$_{60 }$PCBM ([6,6]-phenyl-C$_{61}$-butyric acid methyl ester) or graphene flakes) in $\sim $10 $\mu $ solvent droplets entrained in a nitrogen carrier gas. The twice-differentially pumped source is then mated to a UHV-STM system, for fundamental studies. The source has been used to generate films of C$_{60 }$PCBM, CNT's, and graphene/PPV composites on SiO$_{2}$ and mica substrates. The spray-jet deposition provides much greater control of the growth kinetics, relative to conventional spin-coating, permitting films to be grown with submonolayer control, as we demonstrate in the growth of C$_{60 }$PCBM films. [Preview Abstract] |
Wednesday, March 23, 2011 2:54PM - 3:06PM |
T30.00003: Preparation and Characterization of $\alpha $-Fe$_{2}$O$_{3}$ Nanoparticles by a Solution-Phase Auto-Combustion Method Marc Doyle, Michael Lattanzi, Brian Kelly, Karl Unruh The effects of the reaction conditions on the structural and magnetic properties of $\alpha $-Fe$_{2}$O$_{3}$ nanoparticles prepared from the combustion products of Fe(III)-nitrate/citric acid/NaOH solutions have been systematically studied in order to gain insights that might be useful in the preparation of more complex oxides from other solution-phase auto-combustion precursors. This work has focused on the effects of the initial solution pH and fuel/oxidant ratio. In particular, precursor powders have been prepared from solutions with pH values between 1 and 12 and with fuel/oxidant ratios between 0.5 and 1.5. Increasing the solution pH and/or the fuel/oxidant ratio lead to significantly less dense and more porous precursor powders due to the greater amount of gaseous reaction products produced under these conditions. X-ray diffraction measurements indicated that under these reaction conditions a higher annealing temperature was required to obtain a phase pure $\alpha $-Fe$_{2}$O$_{3}$ product. [Preview Abstract] |
Wednesday, March 23, 2011 3:06PM - 3:18PM |
T30.00004: Synthesis, Microstructure and Bulk Properties of Complex Nasicon-Type Ceramics Kristina Lipinska, Oliver Hemmers, Julien Romann, Stanislav Sinogeikin, Patricia Kalita, Shekar Balagopal, Anthony Nickens Fast ion-conductors from the NASICON family (Na$_{1+x}$Zr$_{2}$Si$_{x}$P$_{3-x}$O$_{12})$ have been the subject of extensive research due to their use in electrochemical devices such as batteries, fuel cells, thermoelectric generators and chemical sensors A fabrication challenge for these materials is to maintain long term chemical and physical stability in harsh environments We apply a multi-technique approach to show how partial substitutions with tetravalent and pentavalent cations produce NASICONs with specific morphology and modify the primary to secondary crystalline phase ratios. We use in situ synchrotron x-ray diffraction to investigate pressure-induced structural modifications and compressibility. [Preview Abstract] |
Wednesday, March 23, 2011 3:18PM - 3:30PM |
T30.00005: Crystal structure and multiferroic properties of the 0.7(BaTiO$_{3})$ -- 0.3(Bi$_{0.45}$Dy$_{0.55}$FeO$_{3})$ ceramic composite Ricardo Martinez, Nora Ortega, Ashok Kumar, Ratnakar Palai, Ram S. Katiyar Magnetoelectric multiferroics are a novel class of next generation multifunctional materials. Intensive research is being pursued towards the development of new room temperature multiferroics with strong magnetoelectric (ME) coupling. BaTiO$_{3 }$(BT) is well known ferroelectric and Bi$_{0.45}$Dy$_{0.55}$FeO$_{3 }$(BDFO) is multiferroic in nature with weak ferroelectric properties. We have synthesized lead free ceramic composite consisting of 0.7BT--0.3BDFO (BT-BDFO) by conventional solid state. X-ray diffraction and Raman analysis revealed two sets of peaks which belong to BT and BDFO suggesting that the individual phases are retained in the composite ceramic, no additional peaks were observed. The presence of ferromagnetic and ferroelectric hysteresis loops at room temperature (M$_{s}$=14.3 emu/cm$^{3}$, M$_{r}$=1.7 emu/cm$^{3}$, P$_{r}$=3.6 $\mu $C/cm$^{2}$ and E$_{c}$=1.7 kV/cm) showed multiferroic nature of the BT-BDFO ceramic. Although the polarization and magnetization values obtained were lower compared with pure BaTiO$_{3 }$and BDFO respectively, magneto-dielectric measurements reveled a shifting of the dielectric constant peak from 2 MHz to 4 MHz with increase of magnetic field from 0 T to 2 T. [Preview Abstract] |
Wednesday, March 23, 2011 3:30PM - 3:42PM |
T30.00006: Cation Ordering within the Perovskite Block of a Six-layer Ruddlesden-Popper Oxide from Layer-by-layer Growth Lei Yan, H.J. Niu, M.J. Rosseinsky The (AO)(ABO$_{3})_{n}$ Ruddlesden-Popper structure is an archetypal complex oxide consisting of two distinct structural units, an (AO) rock salt layer separating an n-octahedra thick perovskite block. Conventional high-temperature oxide synthesis methods cannot access members with n $>$ 3, but low temperature layer-by-layer thin film methods allow the preparation of materials with thicker perovskite blocks, exploiting high surface mobility and lattice matching with the substrate. This presentation describes the growth of an n = 6 member CaO/(ABO$_{3})_{n}$ (ABO$_{3}$: CaMnO$_{3}$, La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ or Ca$_{0.85}$Sm$_{0.15}$MnO$_{3})$ epitaxial single crystal films on the (001) SrTiO$_{3}$ substrates by pulsed laser deposition with the assistance of a reflection high energy electron diffraction (RHEED). [Preview Abstract] |
Wednesday, March 23, 2011 3:42PM - 3:54PM |
T30.00007: Morphological Transformation of Copper Catalysts within Helically Coiled Carbon Nanofibers Lifeng Dong, Liyan Yu, Qian Zhang With tailoring synthesis parameters, different carbon nanostructures including carbon nanotubes, carbon nanofibers, and graphene, can be synthesized using copper (Cu) as catalysts and acetylene as carbon source. Some remarkable progress has been made in synthesis techniques; however, pioneering breakthroughs have not been made yet in terms of growth mechanism, especially interactions between catalyst particles and acetylene molecules. In this study, the growth mechanism of helically coiled carbon nanofibers and morphological changes of Cu catalysts were investigated using a number of electron microscopy and microanalysis techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). Following the synthesis, single-crystal Cu particles deformed to small nanoparticles of cuprous oxide (Cu2O) due to internal strain, and Cu2O nanoparticles migrated within carbon nanofibers. [Preview Abstract] |
Wednesday, March 23, 2011 3:54PM - 4:06PM |
T30.00008: ABSTRACT WITHDRAWN |
Wednesday, March 23, 2011 4:06PM - 4:18PM |
T30.00009: Templated Electrodeposition of Highly Porous Nanostructured Materials Han-Chang Yang, Stephanie Lim, Jiabin Liu, Qian Wu, X.M. Cheng The fabrication of nanoporous materials has been of great interest for applications such as biosensors, photonic materials and energy storage. Compared to many other methods, the templated electrodeposition method is low cost, fast, and compatible with large-scale production. In this work, we developed a templated electrochemical deposition technique for fabricating highly ordered and highly porous nanostructured materials. The fabrication involves the following steps: self-assembly of monodispersed polystyrene spheres, electrochemical deposition of the desired materials, and sphere removal by a dissolution process. Deposition of Au and Ni layered metallic nanoporous structures were studied using different electrolytes at appropriate potentials. The pore size of the materials was tuned by using different sizes of template polystyrene spheres ranging from 50nm to 1000nm. Scanning electron microscopy images confirmed the highly ordered 3-dimensional hexagonal closed pack (hcp) structures in the samples. The templated electrochemical deposition technique provides a promising alternative approach to preparing highly porous anode materials for battery applications. [Preview Abstract] |
Wednesday, March 23, 2011 4:18PM - 4:30PM |
T30.00010: Entropic inflation of ideal zeolitic frameworks Vitaliy Kapko, Colby Dawson, Michael Treacy Ideal zeolites can be viewed as flexible networks of rigid, corner-sharing tetrahedra. Recent studies have shown that such systems can exist at a range of densities (termed the ``flexibility window'') without breaking topology or deforming the comprising tetrahedra. They also have shown that densities of real zeolites almost always correspond to the lowest densities within this range. This anomalous behavior is usually attributed to coulombic repulsion between oxygen atoms in framework cavities and channels. In this paper we show that the inflation of ideal zeolites can be driven by entropy. This effect is closely related to displacive phase transitions often observed in zeolites and related materials like quartz, which cannot be explained by potential energy minimization alone. We show that periodicity and high symmetry in ideal zeolites is a result of entropy maximization. An estimation of entropy using a harmonic oscillator model with a realistic force field is given. [Preview Abstract] |
Wednesday, March 23, 2011 4:30PM - 4:42PM |
T30.00011: Topological defects in model nanoporous carbon: population, structural characterizations and adsorption properties Xi Mi, Jeremy Palmer, Jorge Pikunic, Keith Gubbins, Yunfeng Shi Nanoporous carbon materials have drawn substantial research interests because of their unique capabilities to mediate the mass-transport, uptake through adsorptions and catalyze chemical reactions of the guest species. All aforementioned properties depend sensitively on the structural characteristics of the nanoporous carbon, including hybridization state of carbon, presence of functional groups, topology of carbon rings and curvature/connectivity of graphene sheets. Among all these defects, carbon pentagons are of particular interests since they possess 108$^{\circ}$ C-C-C bond angles which are dramatically different from the 120$^{\circ}$ angles typical for carbon hexagons and larger carbon rings. However, the pentagon concentration in the bulk has not been determined. Here we use a realistic nanoporous carbon model proposed recently to systematically synthesize a large number of samples with different concentrations of carbon pentagons using molecular simulation methods. We evaluate the different porous structures in terms of their deviations in s(q) from experiments so as to estimate pentagon concentrations. Moreover, the porous structures are related to the adsorption properties through simulated argon adsorption tests. [Preview Abstract] |
Wednesday, March 23, 2011 4:42PM - 4:54PM |
T30.00012: The stability of capillary climbing flows in porous media opposed by gravity force B. Markicevic, H.K. Navaz The experimental and numerical data reveal that the capillary climb opposed by gravity force starts as a stable flow for low climbing height, which is followed by unstable flow and multiphase pattern for higher climbing heights. For the stable flow, a sharp interface between the liquid and gas phase exists, which transforms later into a flow front of increasing thickness as climbing progresses. The flow front thickness is calculated from the difference between instantaneous climbing height and maximum stable climbing height. We carry out the analysis of capillary climb flow stability using the capillary and the Bond number, as well as using the generalized Bond number. The critical generalized Bond number defines the condition for which the interface transforms to the flow front. For three distinct porous media consisting of glass beads, and having a thin layer of low permeable material at the bottom of the glass beads columns, the values of critical generalized Bond number and the exponents in the power law of flow front thickness as a function of the generalized Bond number are compared. Furthermore, the flow stability analysis is extended to two additional cases in which a low-permeable layer is removed from the column bottom, and the case of pure capillary flow (without gravity). The corresponding critical generalized Bond numbers and the power law exponents are compared. [Preview Abstract] |
Wednesday, March 23, 2011 4:54PM - 5:06PM |
T30.00013: Soaring to New Heights in Natural Materials Sara Bodde, James Kiang, Joanna McKittrick Feathers are the most distinguishable feature of all modern Aves. Flight feathers exemplify several materials science phenomena. The most obvious attribute is the branching or hierarchical structure at macroscale to mesoscale. The primary shaft, or rachis from which secondary features project, of the flight feather is a sandwich structured composite. The thin brittle cortex of the rachis and barbules encloses a relatively thick, low-density medullary core or cellular solid. The cortex of the rachis is constructed as a fiber-reinforcement composite, and structural variations along the length of the feather invoke the comparison to functionally graded materials. We have studied microstructure and mechanical properties of the feather rachis in a piecewise fashion, and we will present results of investigations of the mechanical behavior and failure of the composite and parts thereof in tension, compression, and flexure. [Preview Abstract] |
Wednesday, March 23, 2011 5:06PM - 5:18PM |
T30.00014: Three-dimensional video imaging of drainage and imbibition processes in model porous medium Prerna Sharma, P Aswathi, Anit Sane, Shankar Ghosh, Sabyasachi Bhattacharya We report experimental results where we have performed three dimensional video imaging of the displacement of an oil phase by an aqueous phase and vice versa in a model porous medium. The stability of the oil water interface was studied as a function of their viscosity ratios, the wettability of the porous medium and the variation in the pore size distribution. Our experiments captures the pore scale information of the displacement process and its role in determining the long time structure of the interface. [Preview Abstract] |
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