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12th Polymer Electrolyte Fuel Cell Symposium, PEFC 2012 - 222nd ECS Meeting

作者： Kolla, P. Kerce, K. Normah, Y. Houk, J. Rhine, W. Dixon, D. Zhao, Y. Fong, H. Smirnova, A. Materials Engineering and Science Program South Dakota School of Mines and Technology Rapid City 57701 United States Department of Chemistry South Dakota School of Mines and Technology Rapid City 57701 United States Department of Chemical and Biological Engineering South Dakota School of Mines and Technology Rapid City 57701 United States Aspen Aerogel Inc. Northborough MA 01532 United States

ISBN: (纸本)9781607683506

3D-carbon aerogel nanomatrix has been modified with iron nitrate in the amounts of 10 and 20 wt. % by wet incipient method. The crystal structure, morphology, and electrocatalytic activity of the formed nanocomposites have been studied in comparison to the unmodified carbon aerogels after their heat-treatment at 900°C, 1200°C and 1400°C in argon. The mass and specific surface area losses in these materials reduced with iron doping is clear from BET isotherms and BJH pore size analysis. The HRTEM analysis confirms the presence of uniformly distributed ∼43.5nm iron nanoparticles surrounded by graphite layers. The XRD analysis show that the level of graphitization increases with the sintering temperature and the concentration of the iron-containing phase. The ORR electrocatalytic activity studies demonstrate the influence of the heat-treatment temperature of samples on the ORR activity. Temperature programed reduction is carried out to understand the reduction behavior of these catalysts to metallic iron, to use them as substrates for direct CNT growth. © The Electrochemical Society.

关键词： Graphitization

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Correlation and relativistic effects in U metal and U-Zr alloy: Validation of ab initio approaches

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Physical Review B 2013年第23期88卷 235128-235128页

作者： Wei Xie (谢玮) Wei Xiong Chris A. Marianetti Dane Morgan Materials Science Program University of Wisconsin-Madison Madison Wisconsin 53706 USA Department of Materials Science and Engineering University of Wisconsin-Madison Madison Wisconsin 53706 USA Department of Applied Physics and Applied Mathematics Columbia University New York New York 10027 USA Department of Engineering Physics University of Wisconsin-Madison Madison Wisconsin 53706 USA

Ab initio calculations have been performed on all solid phases of U metal and U-Zr alloy, the basis of a promising metallic fuel for fast nuclear reactors. Based on generalized gradient approximation, both density functional theory (DFT) in its standard form and the so-called DFT plus Hubbard U (DFT+U) modification are evaluated. The evolution of calculated energetics, volume, magnetic moments, electronic structure, and f-orbital occupation as functions of the effective Hubbard U parameter, Ueff, is carefully examined at Ueff from 0 to 4 eV. DFT is found to overestimate energetics, underestimate volume, downward shift some f bands near Fermi level and overestimate f-orbital occupation against existing experimental and/or computational data. The error is ∼0.07 eV/atom in terms of enthalpy, which affects phase stability modeling for δ(U,Zr) and γ(U,Zr). DFT+U at Ueff=1−1.5 eV offers clear improvement on these calculated properties (∼0.05 eV/atom in terms of enthalpy) and in general still neither promotes ordered magnetic moments nor opens unphysical band gaps, which occur at higher Ueff values. The empirical Ueff values of 1–1.5 eV are close to but smaller than the theoretical estimations of 1.9–2.3 eV that we obtain from the linear response approach. Ueff is found to vary only slightly (≤0.24 eV) between different phases and at different compositions of U and U-Zr; thus, a single Ueff=1.24 eV, which is the statistical optimal from energetic fitting, is suggested for both U and U-Zr. Besides correlation, the relativistic effect of spin-orbit coupling (SOC) is also systematically explored. SOC is found to lower energy, increase volume, and split the 5f shell above Fermi level and reduce f-orbital occupation. The effect predominates in the unoccupied states and is very small on all these calculated ground state properties (∼0.02 eV/atom in terms of enthalpy).

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Graphene-Iike nanostructures obtained from biomass

Graphene-Iike nanostructures obtained from biomass

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2012 MRS Fall Meeting

作者： Barin, Gabriela Bonn Santos, Yane Honorato Rocha, Jennyfer Alves Da Costa, Luiz Pereira Filho, Antônio Gomes Souza De Fátima Gimenez, Iara Barreto, Ledjane Silva Pos-graduation Program of Science and Materials Engineering Federal University of Sergipe Marechal Rondon Ave São Cristóvão 49000-100 Brazil Department of Chemistry Federal University of Sergipe Marechal Rondon Ave São Cristóvão 49000-100 Brazil Pos Graduation Program of Industrial Biotechnology Tiradentes University Aracaju Brazil Department of Physic Federal University of Ceara Fortaleza Ceará Brazil

ISBN: (纸本)9781632660985

Two dimensional (2D) carbon nanomaterials such as few graphite layers or graphene are extensively studied due to their unique properties suitable to be exploiting in a wide range of technological applications. Recently, the growth of high quality graphene monolayers using insects and waste as carbon precursors was reported in the literature. This methodology opened a new way to convert the waste carbon into a high-value-added product. In the present work coconut coir dust, an agroindustrial biomass, was used as biotemplate for preparing carbonaceous materials. Carbon structures were synthesized through pyrolysis under nitrogen atmosphere (lOOmL/min) at 500, 1000, and 1500°C during 2 hours. Starting materials were coconut coir dust in natura and coconut coir dust hydrothermally treated. The samples were characterized by X-ray diffraction, Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Raman spectra showed the D band for all samples, related to the presence of defects in sp2 carbon structure and G band, indicative of graphite crystallites. It was also observed that the sample carbonized at 1500°C from coconut coir dust treated by hydrothermal method showed G' band at 2685cm-1 associated with the stacking order along the c-axis. X-ray diffraction analysis showed a broad peak around 2θ= 22° related to the presence of amorphous carbon. By increasing the pyrolysis temperature changes in XRD diffractograms were observed and the sample which was pyrolysed at 1500°C from coconut coir dust hydrothermally treated showed peaks at 28= 26.5°, 43° e 45° assigned to (002), (100) (101) graphite plans, respectively. Scanning electron microscopy images showed the presence of overlapping sheets and plates. Transmission Electron Microscopy (TEM) images of coconut coir dust in natura unveiled the formation of amorphous sheet. Coconut coir dust in natura and treated by the hydrothermal method pyrolysed at 1500°C, lead to the formation of

关键词： Graphene

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Liquid‐Free Lithium–Oxygen Batteries†

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Angewandte Chemie 2014年第2期127卷

作者： Moran Balaish Emanuel Peled Diana Golodnitsky Yair Ein‐Eli The Nancy & Stephen Grand Technion Energy Program Technion‐Israel Institute of Technology Haifa 3200003 (Israel) School of Chemistry Tel Aviv University Tel Aviv 69978 (Israel) Department of Materials Science and Engineering and The Nancy & Stephen Grand Technion Energy Program Technion‐Israel Institute of Technology Haifa 3200003 (Israel)

Non‐aqueous lithium–oxygen batteries are considered as most advanced power sources, albeit they are facing numerous challenges concerning almost each cell component. Herein, we diverge from the conventional and traditional liquid‐based non‐aqueous Li–O 2 batteries to a Li–O 2 system based on a solid polymer electrolyte (SPE‐) and operated at a temperature higher than the melting point of the polymer electrolyte, where useful and most applicable conductivity values are easily achieved. The proposed SPE‐based Li‐O 2 cell is compared to Li–O 2 cells based on ethylene glycol dimethyl ether (glyme) through potentiodynamic and galvanostatic studies, showing a higher cell discharge voltage by 80 mV and most significantly, a charge voltage lower by 400 mV. The solid‐state battery demonstrated a comparable discharge‐specific capacity to glyme‐based Li–O 2 cells when discharged at the same current density. The results shown here demonstrate that the safer PEO‐based Li–O 2 battery is highly advantageous and can potentially replace the contingent of liquid‐based cells upon further investigation.

关键词： Elektrolyte Kohlenstoffnanoröhren Lithium‐Sauerstoff‐Batterien Polymere Sauerstoff

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Facile, Green Synthesis of Large Single Crystal Copper Micro and Nanoparticles with Ascorbic Acid and Gum Arabic

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Open Journal of Applied sciences 2013年第5期3卷 332-336页

作者： Preston B. Landon Alexander H. Mo Carlos T. Ramos Jose J. Gutierrez Ratnesh Lal Department of Bioengineering University of California San Diego USA Department of Chemistry The University of Texas Pan American Edinburg USA Department of Mechanical Engineering University of California San Diego USA Materials Science and Engineering Program University of California San Diego USA

Large single crystal colloidal copper particles with diameters between 0.5 - 2 μm were created using a green synthesis process. The process used ascorbic acid to reduce Schweizer’s reagent created in situ using copper salts in the presence of various concentrations of gum arabic. The Schweizer’s reagents were created by varying the concentrations of ammonium hydroxide and copper nitrate solutions, copper hydroxide, or copper sulfate. The pH of the solution was controlled by the addition of ascorbic acid. Particle formation was favored at high temperature using copper sulfate at pH values ranging from 7.5 to 9, while the optimal formation occurred at a pH value of 8.5. At high concentrations, copper particle formation was found to occur from the aggregation of smaller particles which continued to nucleate once aggregated, and this resulted in the creation of globular particles and large aggregates of micron-sized particles. The addition of gum arabic resulted in the creation of large single crystal particles that did not aggregate. SEM was used to observe the effect of increasing gum arabic concentrations and EDX was used to confirm the elemental purity of the particles.

关键词： Copper Green Synthesis Microparticles Nanoparticles Gum Arabic Ascorbic Acid

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Tunable optical antennas enabled by the phase transition in vanadium dioxide

Tunable optical antennas enabled by the phase transition in ...

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作者： Earl, Stuart K. James, Timothy D. Davis, Timothy J. McCallum, Jeffrey C. Marvel, Robert E. Haglund Jr., Richard F. Roberts, Ann School of Physics University of Melbourne VIC 3010 Australia Australian National Fabrication Facility Clayton VIC 3168 Australia CSIRO Material Science and Engineering Private Bag 33 Clayton VIC 3168 Australia Interdisciplinary Materials Science Program Vanderbilt University Nashville TN 37235 United States Department of Physics and Astronomy Vanderbilt University Nashville TN 37325 United States

Optical antennas, subwavelength metallic structures resonating at visible frequencies, are a relatively new branch of antenna technology being applied in science, technology and medicine. Dynamically tuning the resonances of these antennas would increase their range of application and offer potential increases in plasmonic device efficiencies. Silver nanoantenna arrays were fabricated on a thin film of the phase change material vanadium dioxide (VO2) and the resonant wavelength of these arrays was modulated by increasing the temperature of the substrate above the critical temperature (approximately 68°C). Depending on the array, wavelength modulation of up to 110 nm was observed. ©2013 Optical Society of America.

关键词： Vanadium dioxide

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A low power miniaturized CMOS-based continuous glucose monitoring system

A low power miniaturized CMOS-based continuous glucose monit...

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2013 IEEE International Conference on Body Sensor Networks, BSN 2013

作者： Croce Jr., Robert A. Vaddiraju, Santhisagar Legassey, Allen Wang, Yan Burgess, Diane Papadimitrakopoulos, Fotios Jain, Faquir C. Biorasis Inc. Technology Incubation Program Storrs CT 06269 United States Department of Pharmaceutical Sciences University of Connecticut Storrs CT 06269 United States Dept. of Chemistry Institute of Materials Science University of Connecticut Storrs CT 06269 United States Department of Electrical and Computer Engineering University of Connecticut Storrs CT 06269 United States

ISBN: (纸本)9781479903306

This paper presents the design and fabrication of a highly-miniaturized system for continuous glucose monitoring which holds great promise for patients inflicted with diabetes mellitus. To achieve the realization of a truly implantable system, a variety of issues such as robust electrochemical sensor design, miniaturization of the electronic components and counteracting biofouling and negative tissue response need to be addressed. In this report, we present a highly-miniaturized transcutaneous continuous glucose monitoring system which holistically addresses the aforementioned tribulations associated with implantable devices. Specifically, a high performance amperometric electrochemical glucose sensor is integrated with custom designed complementary metal-oxide-semiconductor electronics. The fabricated electrochemical sensor is Clark-based, and employs stratification of five functional layers to achieve a linear response within the physiological range of glucose concentration (2-22 mM). Furthermore, the sensor is encased with a thick polyvinyl alcohol (PVA) hydrogel containing poly(lactic-co-glycolic acid) (PLGA) microspheres which provides continuous, localized delivery of dexamethasone utilized to combat inflammation and fibrosis. Such miniature size (0.665 mm2) and low power operation (140 μW) of the electronic system render it ideal for continuous glucose monitoring devices and other metabolic sensing systems. © 2013 IEEE.

关键词： CMOS integrated circuits

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Roles of organic acids during exectrooxidation reaction over Pt-supported carbon electrodes in direct methanol fuel cells

Roles of organic acids during exectrooxidation reaction over...

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作者： Wong, Chee Yong Chen, Shi-Kun Lo, An-Ya Tseng, Chuan-Ming Lin, Chiu-Yue Liu, Shang-Bin Department of Materials Science and Engineering Fong Chia University Taichung 40724 Taiwan Green Energy Development Center and Master's Program of Green Energy Science and Technology Fong Chia University Taichung 40724 Taiwan Institute of Physics Academia Sinica Taipei 11529 Taiwan Institute of Atomic and Molecular Sciences Academia Sinica Taipei 10617 Taiwan Department of Chemistry National Taiwan Normal University Taipei 11677 Taiwan

A comprehensive study has been made to explore the role of organic acids on electrocatalytic performances of platinum (Pt) nanoparticles supported on carbon porous materials (CPMs) in proton exchange membrane fuel cells (PEMFCs). In particular, the effects of carboxylic acids (R-COOH), viz. formic acid, acetic acid, propionic acid, and butyric acid on catalytic activity, stability, and durability of anodic Pt/CPM electrocatalyst in direct methanol fuel cells (DMFCs) were investigated. In the presence of doped carboxylic acids, the electrooxidative activity of Pt/CPM follows the trend: HCOOH 3COOH 2H5COOH 3H 7COOH, revealing a consistent increase in the severity of catalyst deactivation with the number of carbons on the alkyl chain of the dopant. The Pt/CPM was found to exhibit electrocatalytic performances and tolerance for poisoning than a commercial Pt/XC-72 catalyst with a similar Pt loading (20 wt%). Moreover, a notable increase in mass activity up to ca. 150% over the spent Pt/CPM catalyst was observed up on removing the organic acid in the feed stream, indicating that catalyst poisoning by deactivation may be revived, even to its "intrinsic" activity. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Electrocatalysts

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Isolation of collagen from cortical bovine bone for preparation of porous collagen sponges

Isolation of collagen from cortical bovine bone for preparat...

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2012 Annual Conference on Experimental and Applied Mechanics

作者： Castro-Ceseña, Ana B. Novitskaya, Ekaterina E. Phadke, Ameya Varghese, Shyni McKittrick, Joanna Materials Science and Engineering Program University of California San Diego 9500 Gilman Dr. San Diego CA 92093 United States Department of Bioengineering University of California San Diego 9500 Gilman Dr. San Diego CA 92093 United States Department of Mechanical and Aerospace Engineering University of California San Diego 9500 Gilman Dr. San Diego CA 92093 United States

ISBN: (纸本)9781461444268

Fabrication of collagen sponges from type I collagen isolated from cortical bovine femur bone is reported. Collagen was extracted with 0.1 M EDTA by refreshing the solution every 24 h for 9 days. Sodium dodecyl sulfate poly-acrylamide gel electrophoresis (SDS-PAGE) demonstrated the isolation of intact pure type I collagen. The sponges were fabricated by freeze-drying and heat-dehydration cross-linking of collagen solution. The resulting sponges showed fibrils arranged in a highly porous network. These sponges can be used for tissue engineering as well as for bone-like composite fabrication. © The Society for Experimental Mechanics, Inc. 2013.

关键词： Collagen

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The green synthesis and environmental applications of nanomaterialsw

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RSC Green Chemistry 2013年 106-143页

作者： Han, Changseok Pelaez, Miguel Nadagouda, Mallikarjuna N. Obare, Sherine O. Falaras, Polycarpos Dunlop, Patrick S.M. Byrne, J. Anthony Choi, Hyeok Dionysiou, Dionysios D. Environmental Engineering and Science Program University of Cincinnati Cincinnati OH 45221 United States US Environmental Protection Agency ORD WSWRD 26 West MLK Drive Cincinnati OH 45268 United States Department of Chemistry Western Michigan University Kalamazoo MI 49008 United States Division of Physical Chemistry Institute of Advanced Materials National Center for Scientific Research Demokritos 15310 Aghia Parakevi Attikis Athens Greece Nanotechnology and Integrated BioEngineering Centre School of Engineering University of Ulster BT37 0QB United Kingdom Department of Civil Engineering University of Texas at Arlington Arlington TX 76019 United States

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