bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nano-Flower MnO2 Coated Graphene Composite Electrodes for Energy Storage Devices
Authors: Cheng Qian , Tang Jie , Ma Jun , Zhang Han , Shinya Norio , Qin Lu-Chang 
Published: April 2011

ABSTRACTGraphene, two-dimensional layers of sp2-bonded carbon, has many unique properties. In this paper, graphene is decorated with flower-like MnO2 nanostructures for the application in energy storage devices. The as-prepared graphene and MnO2 nano-flowers, which were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were assembled into an asymmetric supercapacitor. The specific capacitance of the graphene electrode reached 245 F/g at a charging current of 1 mA. The MnO2 nano-flowers which consisted of tiny rods with a diameter of less than 10 nm were coated onto the graphene electrodes by electrodeposition. The specific capacitance after the MnO2 deposition is 328 F/g at the charging current of 1 mA with an energy density of 11.4Wh/kg and power density of 25.8 kW/kg. This work suggests that our graphene-based electrodes can be a promising candidate for high-performance energy storage devices.
Electronic Structures of Non-Pt Carbon Alloy Catalysts for Polymer Electrolyte Membrane Fuel Cells Revealed by Synchrotron Radiation Analyses
Authors: Oshima Masaharu , Niwa Hideharu , Saito Makoto , Kobayashi Masaki. , Horiba Koji , Harada Yoshihisa , Terakura Kiyoyuki , Ikeda Takashi , Ozaki Jun-ichi , Nabae Yuta , Miyata Seizo 
Published: April 2011

ABSTRACTThe oxygen reduction reaction (ORR) mechanism of non-Pt catalysts was elucidated by investigating electronic structures of carbon alloy catalysts (CACs) for polymer electrolyte membrane fuel cells (PEMFC). For metal phthalocyanine-based carbon alloy catalysts with 1-2% of nitrogen and less than 0.1% of Co or Fe, photoelectron spectroscopy, X-ray absorption spectroscopy (XAS), and X-ray Absorption Fine Structure (XAFS) have revealed that Co or Fe metal sites are not the ORR active site, whereas the carbon atoms adjacent to graphitic nitrogens at a zigzag edge of graphite may act as the ORR active site, which is in good agreement with first principles calculations. These studies have also revealed that the zigzag edges, detected as a XAS shoulder component, are well evolved for catalysts pyrolyzed at 600°C, which show the maximum ORR activity. Based on these analyses, we have realized significantly improved carbon alloy based ORR performance, up to about 70 % of that with Pt catalysts. Further, to analyze the electronic structure of CACs during operation, we constructed a new in situ soft X-ray emission spectroscopy system with very high energy resolution (ΔE) of 120 meV at 640 eV at the University of Tokyo beamline BL07LSU in SPring-8.
Electrical and photoelectrical measurements on ZnO-Nanowires coated with PEDOT:PSS for Dye-Sensitized Solar Cells
Authors: Waltermann Julia , Günther Kay-Michael , Kontermann Stefan , Waldvogel Siegfried R. , Schade Wolfgang 
Published: April 2011

ABSTRACTDye-sensitized solar cells composed of an n-doped ZnO nanowire array and a p-doped polymer layer appears to be a promising candidate for low-cost production of environment-friendly solar cells. In this work, we investigate hybrid devices consisting of a transparent conducting oxide (TCO) substrate, ZnO-nanowires (ZnO-NW) or a sol-gel prepared ZnO layer, a ruthenium dye (N719) and a PEDOT:PSS or P3HT layer. The dense polycrystalline ZnO layer is able to prevent short circuits, which have a strong effect on the performance of the solar cells. This is demonstrated by the use of only the ZnO layer which improves the open circuit voltage by a factor of 2 and the efficiency by a factor of 1.7 compared to cells with nanowires. That indicates that the system combined with a thin but dense ZnO layer and NW grown on it will show further improvement. Furthermore three different TCO substrates were investigated. Impedance spectroscopy (IS) reveals at least one additional Schottky barrier formed with ZnO:Al substrates. Spectral photovoltage measurements clearly show distinct absorption features correlated with the ZnO and N719 dye.
SYNTHESIS OF CNT-METAL OXIDE NANO-COMPOSITE ELECTRODE MATERIALS FOR SUPERCAPACITATOR BY LOW-PRESSURE MOCVD
Authors: Arod Pallavi , Shivashankar S.A. 
Published: April 2011

ABSTRACTHomogeneous composite thin films of Fe2O3-carbon nanotube were synthesized in a novel, single-step process by metalorganic chemical vapor deposition (MOCVD) using ferric acetyl acetonate as precursor. The deposition of composite takes place in a narrow range of CVD conditions, beyond which the deposition either multiwall carbon nanotubes (MWNTs) only or hematite (α-Fe2O3) only takes place. The composite film formed on stainless steel substrates were tested for their supercapacitive properties in various aqueous electrolytes.
Polypyrrole Nanowire Array with High Aspect Ratio Fabricated by Block-Copolymer-Templated Electropolymerization
Authors: Komiyama Hideaki , Iyoda Tomokazu , Kamata Kaori 
Published: April 2011

ABSTRACTConducting polypyrrole (PPy) nanowire array was electrochemically fabricated by using microphase-separated block copolymer (PEOm-b-PMA(Az)n) thin film as an electrode template. Electropolymerization proceeds selectively through the perpendiculary oriented PEO nanocylindrical microdomains on an ITO electrode coated by the above polymer film. The length of the PPy nanowires was controllable in range of 10-120 nm by the thickness of the coated template film and the amount of passed charge. A 10 nm of diameter, 27 nm of periodicity, and 12 of aspect ratio of the crystalline PPy nanowires were successfully achieved. Selective removal of the template is also achieved simply by rinsing with solubility-controlled mixed solvent.
Nanostructure Dependent Surface Energy of Silica Nanorod Arrays through Block Copolymer Templating Processes
Authors: Zhao Yongbin , Chen Aihua , Iyoda Tomokazu 
Published: April 2011

ABSTRACTThe self-assembled block copolymer films with poly (ethylene oxide) (PEO) and hydrophobic polymetharylate (PMA) with azobenzene mesogen in the side chain, denoted as PEOm-b-PMA(Az)n, were used as the template to prepare hexagonally ordered silica nanorod arrays by immersing the template films in the silicate precursor containing tetraetoxysilane (TEOS). The diameter and the center-to-center distance of the SiO2 nanorod arrays were controlled by selecting the block copolymer with different PEO volume fraction. In addition, the contact angles of different kinds’ solvents for the SiO2 nanorod arrays were characterized. We further found, the diameter and the period distance of silica nanorods are very important factors for controlling the contact angle of different kind’s solvents on the surface of the SiO2 nanorod arrays.
Synthesis of Layered Titanate Micro/nano-materials for Efficient Pollutant Treatment in Aqueous Media
Authors: Tang Y. X. , Lai Y. K. , Gong D. G. , Dong Zhili , Chen Z. 
Published: April 2011

ABSTRACTIn this work, the one dimensional (1D) titanate nanotubes (TNT)/nanowires (TNW), bulk titanate micro-particles (TMP), and three dimensional (3D) titanate microsphere particles (TMS) with high specific surface area were synthesized via different approaches. The chemical composition and structure of these products have been characterized by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM) study and Raman scattering spectroscopy. The as-prepared TMS shows excellent adsorption performance compared with TMP, TNW and TNT when methylene blue (MB) and PbII ions are used as representative organic and inorganic pollutants.
Thermodynamic aspects of transition metals doped ZnO
Authors: Sedmidubský David , Sofer Zdeněk , Huber Štěpán , Leitner Jindřich 
Published: April 2011

ABSTRACTWe present a thermodynamic study of selected transition metals (TM=Cr, Mn, Fe and Co) solubility in ZnO based on the assessment of available thermodynamic data and ab-initio calculations in the respective TM-Zn-O systems. The ab-initio DFT calculations of enthalpies of formation of the involved phases and the energies of substitution defect (TM-Zn) formation were performed using the full-potential APW+lo technique (WIEN2k code) within GGA+U approximation. The calculated energies of mixed oxides and virtual (unstable) TMO end-members of (Zn,TM)O solid solutions are referred to well established thermodynamic data of binary oxides taken from SGTE database. The assessed thermodynamic data are subsequently used for calculation of phase equilibria and construction of the respective pO2-T-x phase (FactSage software). Whereas the solubility of Mn, Fe, and Co in ZnO is found not to exceed 1 mol% at low temperatures (T<900°C), the homogeneity range is substantially enlarged at elevated temperatures (~10 mol% at the eutectic temperature). By contrast, the solubility of Cr turned out to be negligible in the relevant range of T and pO2.
Growth of Ruthenium and Ruthenium oxide nanoplates
Authors: Meda Lamartine , Stevens Geoffrey D. 
Published: April 2011

ABSTRACTBy carefully manipulating and controlling the growth conditions, Ruthenium (Ru) and ruthenium oxide (RuO2) two-dimensional (2-D) nanostructure were self-assembled into a stack of plates on indium tin oxide coated glass substrate. The nanoplates were grown in a horizontal hot-wall metalorganic chemical vapor deposition (MOCVD) from ruthenocene. Each nanoplate has a thickness in the range of 25 - 60 nm and the average area is 1000 x 300 nm2. Each stack of nanoplates is approximately 1.2 m in height. A continuous layer of Ru and RuO2 thin film, which may serve as the growth template, is observed on the bottom of the nanoplate stacks. Field-emission scanning electron microscopy reveals that each stack of nanoplates was grown vertically aligned on the substrate and exhibited elongated shape. Structural properties which were examined by X-ray diffraction show that the nanoplates are polycrystalline.
Study of Silicon-metal Interaction in Adsorption Process: An Ab-initio Approach
Authors: Chakraborty Sudip , Ghaisas S. V. , Majumder Chiranjib 
Published: April 2011

Abstract:The formation of metal silicide plays important role in deciding the nature of the contact on silicon.Due to their chemically neautral nature,Au and Ag are used as contact metals in various devices.In particular the role of silicides is known to be crucial in defining the behavior of the electrical contact. The interaction of these metals with silicon at cluster level is still under the study.For naoscale devices, the nature at such interaction carries lot more inportance. Bulk Gold silicide(Cohesive energy ~ 3.81eV/atom) shows higher stability compared to silver silicide(Cohesive enrgy ~ 2.95 eV/atom). In the present work we show computational results based on Density Functional Theory(DFT) of Si cluster adsorption on Ag(111) surface and compare with the results of Si adsorption on Au(111). These results bring out the difference in Si cluster-metal surface interactions at the nanoscale. In particular the Si island-metal surface interaction shows island size dependence. We have presented results for most stable orientations only.
Spreading kinetics at a molecular level
Authors: Buraud Jean-Luc , Noel Olivier , Ausserre Dominique 
Published: April 2011

ABSTRACTThe spreading of a smectic nanodrop (8CB liquid crystal) on a solid surface was investigated by direct and real time imaging using the Surface Enhanced Ellipsometric Contrast (SEEC) microscopy [1-2]. The spreading ends with two molecular terraces (made of one monolayer and a bilayer). Two different behaviors were observed. In the first one the upper layer stays dense while shrinking. At the end of the process, the last molecules to disappear are located at the center of the initial disk. In the second one, nucleation and growth of holes is observed in the upper layer, in addition to shrinking. A model is proposed to describe the time evolution of the late stage structure. This model gives exact solutions of the kinetic equations, it covers strongly layered liquids such as smectic liquid crystals, it introduces the two dimensional Laplace pressure as an essential motor for spreading and it takes into account the liquid/gas transition in the surface layer that was consistently reported in experiments with 8CB. This model is in remarkable agreement with the experimental data and can explain the two observed behaviors [3].
Correlation of Nanoscale Structure and Magnetic Properties in Manganese Doped Germanium Dilute Magnetic Semiconductors
Authors: He Li , Yin Wenjing , Yu Jiani , Lu Jiwei , Wolf Stuart , Hull Robert 
Published: April 2011

ABSTRACTSpintronic devices generally require the spin of carriers to be utilized in the storage or manipulation of data. One theoretical model for ferromagnetism in dilute magnetic semiconductors (DMS) results from the percolation of ferromagnetic regions around dilute dopants such as Mn atoms in III-V or group IV materials through the interaction of Mn atoms with carriers. Our work employed Mn implantation in Ge with subsequent rapid thermal annealing or TEM in-situ annealing to study the correlation between structure and magnetic properties. The magnetic properties of 300-350 ºC implanted Ge:Mn (which produced crystalline Ge films) varied significantly with implantation dose and annealing condition due to precipitation and transformation of different MnxGe1-x secondary phases. It was found that Mn substitution of Ge and MnxGe1-x secondary phases can both result in ferromagnetic properties. By combining TEM in-situ annealing and ex-situ magnetic characterization, we have demonstrated detailed correlation of magnetic properties with nanoscale structures in Mn implanted Ge DMS materials.
Building 3D materials from adjustable 2D-units; towards the Design of new Bi-based compounds
Authors: Colmont M. , Endara D. , Huvé M. , Krivovichev S.V. , Mentré O. 
Published: April 2011

ABSTRACTIn the Bi2O3-MO-P2O5 diagram, on the basis of previous compounds based on 2D-ribbon like units, we have predicted and prepared the infinite term. It contains [Bi2O2]2+ planes arranged within a never-observed crystallographic form. In this series, the ribbons-like units are polycations built on the linkage of n O(Bi,M)4 tetrahedra along their width and infinite in a perpendicular dimension. Hence, this novel form completes the continuous series of analogue compounds, whose building units now extend from the single chain to the infinite plane, via a number of discrete n values (2,3,4,5,6,7,8,9,10,11). The presented materials of formulae Bi4MP2O12 (M= Zn and Mg) roughly show the same crystal structure. However different arrangements of the groups located between the [Bi2O2]2+ planes are at the origin of a complex superstructure in the case of the zinc compounds.
Silicon Micro Machining Technologies and Advanced Materials (Porous Silicon and PEEK-WC) for Realization of Micro-PEM Fuel Cells
Authors: Elena Tresso M. , Borello Luisa , Enrico Drioli , Gianolio Giuseppe , Guastella Salvatore , Perrone Denis , Quaglio Marzia , Rossi Andrea M. , Rosso Ilaria , Scaltrito Luciano , Trotta Francesco 
Published: April 2011

ABSTRACTIn view of the development of a miniature PEM fuel cell operating at low temperature on hydrogen or direct methanol as anodic feed and air as cathodic feed, we present preliminary results on the performances obtained by employing silicon-based microfabrication techniques and advanced materials which can be easily integrated in silicon technologies, such as porous silicon for the electrode fabrication and PEEK-WC for membranes alternative to Nafion. Powder blasting and reactive ion etching (RIE) have been used for obtaining anode and cathode micro-channels for hydrogen and methanol, in glass and in silicon bipolar plates. Localized micro-fusion processes has been successfully employed for sealing between silicon and membrane.
PEM fuel cell electrodes using Single Wall Carbon Nanotubes
Authors: Moloney Padraig , Huffman Chad , Springer Micah , Gorelik Olga , Nikolaev Pasha , Sosa Edward , Arepalli Sivaram , Yowell Leonard 
Published: April 2011

ABSTRACTSingle wall carbon nanotubes (SWCNT) have previously been considered potential catalyst supports in proton exchange membrane fuel cells (PEMFC) [1]. Earlier research and development of SWCNT for PEMFC catalyst supports has been advanced by utilizing differing SWCNT purities and carbon blacks in differing ratios. This study validates the performance of SWCNT and introduces new concepts for SWCNT membrane fabrication.
Thermal and Volumetric Studies of Complex Chemical Hydrides: Li-modified/Ti- doped Mg2FeH6, Sonicated LiNH2/LiH and Zn- doped NaBH4
Authors: Srinivasan Sesha , McElwee-White Lisa , Stefanakos Elias , Goswami Yogi , Dumbris Seth 
Published: April 2011

ABSTRACTLight weight hydrogen storage systems are indeed essential for the on-board automotive vehicular applications. Complex chemical hydrides bearing light elements such as Li, Na, Mg etc. and their catalytic doping with transition metal species are presently being investigated. The Li- modified Mg2FeH6structure have been thermally characterized using DSC and TGA techniques. It is interesting to notice that the reduction in the decomposition temperature of about 100° C has been unambiguously observed for the Li modified Mg2FeH6. Besides, there is an enhancement in sorption kinetics for the Ti- doped Mg2FeH6. The role of Ti- species on the dehydrogenation and rehdyrogenation properties of NaAlH4have been explored by heat flow measurements using high pressure differential scanning calorimetry. We have also developed the Li-amide/LiH system by sonicated process and studied their PCT characteristics. A new class of hydrogen storage system Zn(BH4)2with theoretical hydrogen capacity of 8.4 wt.% have been synthesized and we have determined their gravimetric and volumetric characteristics.
Evolved Gas Analysis of Heat-Treated Carbon Nanomaterials
Authors: Shulga Yury , Martynenko Vyacheslav M. , Loutfy R. O. , Moravsky Alex P. 
Published: April 2011

ABSTRACTGases evolved on heat-treatment of intact fullerite C60, single-walled (SW) and multi-walled nanotubes (MWNTs) and chemically modified carbon nanomaterials (deuterofullerites C60Dx, hydrogenated SWNTs and fluorinated MWNTs) are studied by mass spectrometry.
Structure and Thermal Conductivity of Silica Aerogels from Computer Simulations
Authors: Good Brian 
Published: April 2011

ABSTRACTAerogels are of current interest in the aerospace community due to their light weight and low thermal conductivity, making them suitable for a variety of applications, notably cryotank insulation.These gels typically exhibit a complex structure; the smallest feature is a “primary” particle of amorphous silica, typically 2-5nm in diameter. The primary particles aggregate to form “secondary” particles, typically an order of magnitude larger, and these, in turn, form pearl-necklace structures whose details depend on the density. The gels appear to exhibit fractal dimensionality, at least over a small range of length scales.In this work, we investigate the relationship between the structure of the gels, their dimensionality and density, and their thermal conductivity. We model the secondary-particle aggregate structure using a modified Diffusion Limited Cluster Aggregation (DLCA) model. The model produces qualitatively different structures at low and high densities that are consistent with experimental observation. At lower densities, we find evidence for a transition from fractal behavior at small length scales to approximately compact behavior at larger lengths.We model the thermal conductivity using a variant of the random resistor network approach that has been used to describe, e.g. hopping electrical conduction in doped semiconductors. In our model, each secondary particle is assigned an effective thermal conductance that depends on the particle's size, and on the details of its contacts with neighboring particles; the conductivity of the gel network is obtained using standard numerical techniques. The scaling of the thermal conductivity with density and fractal dimension is discussed.
A Novel Two-Step Hydrogen Cycled Methane Reforming Process
Authors: Breitkopf Richard , Smalley Yardlynne , Wang Zhong-Lin , Snyder Robert , Haluska Michael 
Published: April 2011

ABSTRACTWe have prepared novel transition metal fluorite materials for a 2-step hydrogen reformer process that generates low CO hydrogen for fuel cell applications. The nanopowder materials, which are converted to an oxygen vacancy rich form in the first step of the process using methane or any hydrocarbon fuel are subsequently brought back to their original state using water vapor while generating pure hydrogen in the process. We have observed large weight losses in TGA measurements below 500°C with our nanomaterials that we do not observe in similar powders with larger grain size that comprise an efficient low temperature first step. We have also observed decreases in lattice parameter in high temperature XRD measurements consistent with formation of a high concentration of oxygen vacancies. The process has produced fuel efficiencies as high as 65% with typical CO content below 30 ppm using methane fuel. Additionally, since we are using nanomaterials, we have enabled low temperature hydrogen generation with good cycling stability at 500°C.
Commercialization of Thermoelectric Technology
Authors: Stabler Francis R. 
Published: April 2011

ABSTRACTThermoelectric technology capable of solid state electric power generation and cooling has been has been known for almost 180 years. Only in the past 50 years has this technology found its way out of the laboratory and into niche military, space, and commercial products. Most of the profitable commercial products have made their appearance in the past decade. Many of you are working hard to advance the state of the art in thermoelectric materials, and I am sure that you do not want to wait another 180 years, 50 years, or even another decade to commercialize your results. There are many potential ways to commercialize this technology, but the area that I think represents the biggest market is the automotive industry. There are over 17 million automobiles sold in the US each year and over 60 million worldwide. With the possible exception of the electric power industry, I know of no other market segment that is even close to the potential of the automotive industry for using a high volume of thermoelectric materials. Every vehicle produced has an electrical system supplied by a one to two kilowatt generator with increasing power demand as electrical features are added. A high percentage of vehicles have air conditioning systems with 3 to 5 kilowatts of cooling. Sufficiently advanced thermoelectric materials can be the heart of systems that supplement or replace the mechanical or electro-mechanical devices performing these functions today. This paper addresses the boundary conditions for the function, quantity, and value needed to commercialize thermoelectric technology. Timing to introduce subsystems with this technology is also addressed. Thermoelectric technology has to compete with the existing technologies and other emerging technologies to be successfully commercialized. While it seems out of reach today, there is even the potential that sufficiently advanced thermoelectric materials and device construction could one day replace the internal combustion engine and even rival fuel cells in energy conversion efficiency.