bluuebunny/crossref_metadata_2025 huggingface dataset:
Extraintestinal manifestations of inflammatory bowel diseases and their management
Authors: Garamszegi Mária
Published: April 2011

Extraintestinal manifestations of ulcerative colitis and Crohn’s disease are symptoms of variegated organ injuries due to systemic inflammatory process. Bowel disease seems to be primary but upon genetic disposition disturbed immune regulation may result in inflammation of other organs that may appear simultaneously, precede bowel disease or follow it in the quiescent phase. As far as possible extraintestinal manifestations have to be distinguished from the complications of the intestinal inflammation and also from side effects of drugs for its treatment. Involvement of bones and joints, skin, eyes, liver and biliary tract is more common but disease of blood coagulation system, lung, kidneys and nervous system may also appear. Treatment of extraintestinal manifestations is influenced by their association with the activity of the bowel disease. Beyond some specific interventions, to achieve improvement of manifestations independent from activity long lasting anti-inflammatory therapy or immunomodulation is almost always needed. Clinical evidence of different levels from reports support the favorable effect of biologic therapy in different extraintestinal manifestations of inflammatory bowel diseases as well. Care and follow-up of patients is a multidisciplinary task. Orv. Hetil., 2011, 152, 663–671.
Covalently interconnected and separated vanadosilicate shells
Authors: Wang Xiqu , Liu Lumei , Jacobson Allan J.
Published: April 2011

Four new compounds containing vanadosilicate clusters have been synthesized by hydrothermal reactions. The clusters are derived from the [V18O42] Keggin cluster by substitution of V=O caps by Si2O(O,OH)2 species. In Cs9[(V15Si6O46(OH)2Cl)(V2O4)](H2O)6.2, 1, the [V15Si6O46(OH)2] cluster shells are covalently interconnected by VO4 tetrahedra to form an infinite layer. In ((CH3)4N)4[V15Si6O42(OH)6(H2O)](H2O)20, 2, and ((CH3)4N)4(V(H2O)6)2/3 [V15Si6O42(OH)6 (H2O)](H2O), 3, separated [V15Si6O42(OH)6] cluster shells are interlinked by hydrogen bonds to form frameworks with wide channel systems. The separated cluster shell in ((CH3)4N)4((CH3)2NH2)((CH3)2NH) [V14Si8O42(OH)8(HCO2)] (H2O)4.7, 4, has four Si2O(OH)2 species in a tetrahedral configuration. The 2D structure of 1 and 0D structures of 2-4 complement the known 1D and 3D structures formed from such vanadosilicate shells.
The experimental determination of the onset of electrical and thermal conductivity percolation thresholds in carbon nanotube-polymer composites
Authors: Kim Byung-wook , Pfeifer Steven , Park Sung-Hoon , Bandaru Prabhakar R.
Published: April 2011

We show evidence of electrical and thermal conductivity percolation in polymer based carbon nanotube (CNT) composites, which follow power law variations with respect to the CNT concentrations in the matrix. The experimentally obtained percolation thresholds, i.e., ~ 0.074 vol % for single walled CNTs and ~ 2.0 vol % for multi-walled CNTs, were found to be aspect ratio dependent and in accordance with those determined theoretically from excluded volume percolation theory. A much greater enhancement, over 10 orders of magnitude, was obtained in the electrical conductivity at the percolation threshold, while a smaller increase of ~ 100 % was obtained in the thermal conductivity values. Such a difference is qualitatively explained on the basis of the respective conductivity contrast between the CNT filler and the polymer matrix.
Nucleation of the electroactive phase of poly(vinylidene fluoride) by ferrite nanoparticles: surface versus size effects
Authors: Martins P. , Costa C. M. , Benelmekki M. , Lanceros-Mendez S.
Published: April 2011

Multiferroics and magnetoelectric materials show interesting scientific challenges and technnologial applications in sensors, acuators and data storage. In view of the fact that only a small number of materials show this kind of properties, exhaustive research activity is being pursued towards the development of new composite materials. Multiferroic nanocomposites films composed of piezoelectric poly(vinylidene fluoride) (PVDF) and magnetostrictive nanosize CoFe2O4, NiFe2O4 or NiZnFe2O4 ferrites were prepared by a solution method. Those ferrite nanoparticles have the ability to nucleate the electroactive β-phase of the polymer, providing in this way an easy route for the preparation of magnetoelectric particulate composites. The fact that the different nanoparticles promotes different amount of β-phase nucleation for different concentrations of nanoparticles indicates that filler size is not the most important parameter determining phase nucleation but the filler-matrix surface interaction. Further, when the polymer-ferrite surface interaction is modified through surfactation, the electroactive phase is not nucleated.
Self-Assembly of a Water-Soluble Tricyclic Heterocycle into J-Type Rosette Nanotubes
Authors: Borzsonyi Gabor , Beingessner Rachel L. , Yamazaki Takeshi , Cho Jae-Young , Myles Andrew J. , Kovalenko Andriy , Fenniri Hicham
Published: April 2011

The synthesis and self-assembly of a water-soluble, tricyclic, self-complementary heterocycle that features the hydrogen bond donor-acceptor arrays of both guanine (G) and cytosine (C) juxtaposed between a pyridine ring is presented. In solution, this tricycle, which has been termed xK1, self-assembles into Rosette Nanotubes (RNTs) that have an inner diameter of 1.4 nm. Unlike the RNTs formed from the bicyclic congener K1, we demonstrate that xK1 with its extended ð system, forms a J-type RNT assembly determined through UV-Vis, CD and fluorescence spectroscopy experiments. This observation brings the possibility of developing electrically conducting RNTs for applications in the areas of photovoltaics and molecular wires.
Nano Patterning on Surfaces of 3-D Micro Structures by Means of Block Copolymer Self Assembly
Authors: Warisawa Shin’ichi , Mino Hiroyuki , Kometani Reo , Ishihara Sunao
Published: April 2011

In this paper, we present the possibility of nano-scale patterning on surfaces of 3-D micro structures by means of block copolymer self assembly. We succeeded in forming vertical cylinders on the surfaces of the 3-D micro structures using dip-coat process with Au deposition instead of random copolymers. The material of 3-D structures fabricated by FIB-CVD was diamond-like carbon (DLC) due to selecting phenanthrene as a gas source. Since the surface energy of DLC is low, instead of PS-r-PMMA polymer brush, 100 nm-thick Au films were coated on the surfaces of 3-D structures. PS-b-PMMA (PS:PMMA = 50 kg/mol:21 kg/mol) was dip-coated on the Au coated surfaces and annealed. First, we prepared DLC 60° angled slope with size of 2.5 by 3 μm2. As a result, the vertical cylinders were formed in a similar way regardless of the places, i.e., top, middle and bottom on the slopes. vertical cylinders were formed regularly and densely on the entire slope. In order to investigate the effect of slope angle, we prepared 3-D micro structures with different angled slopes such as 70, 80 and 90°. There was no slope angle specific difference, and vertical cylinders were also formed on each slope.
Controlled Hydrothermal Synthesis of Complex Mixed Oxides Using Solution Redox Chemistry
Authors: Walton Richard I. , Sardar Kripasindhu , Playford Helen Y. , Modeshia Deena R. , Darton Richard J. , Fisher Janet , Thompsett David
Published: April 2011

We present the results of a study of the solvothermal synthesis of mixed-metal cerium-containing oxides all prepared from CeCl3.7H2O at less than 250 ºC in single step reactions. The use of NaBiO3 in the presence of aqueous NaOH yields fluorite solid solutions Ce1-xBixO2-x/2 (x ≤ 0.6), whereas the use of either H2O2 or NaBrO3 as oxidant in the presence of TiF3 yields a Ce(IV) pyrochlore (Na0.33Ce0.67)2Ti2O7. With replacement of a fraction of the Ti reagent by Sn(IV) acetate, tin doping is possible in the pyrochlore. The materials have all been assessed for their use in catalysis by performing temperature programmed reduction (TPR) experiments under dilute hydrogen flow. The cerium-bismuth oxides show large and apparently reversible hydrogen uptake, but in situ powder X-ray diffraction shows that this is accompanied by phase separation into bismuth metal and CeO2 that occurs over 5 or more TPR cycles. In contrast, the cerium (IV) titanate pyrochlore shows reversible reduction at low temperature (150 ºC, after an activation step), which gives the material potential use as a precious metal support for catalysis: such as in the water-gas-shift reaction. Although Sn doping lowers the onset of reduction of the pyrochlore, consistent with an expanded lattice, the materials suffer from collapse to give SnO.
DLC-coated Substrate for Infrared Absorption Spectroscopy in Supercritical Water
Authors: Ube Takuji , Ishiguro Takashi
Published: April 2011

The stability of several kinds of substrates, such as Corning #1737 glass, fused silica, synthetic silica, water free synthetic silica, zinc selenide, silicon, and diamond like carbon (DLC) coated Si in supercritical water (663K and 25MPa) were examined. Their reaction with the water was evaluated by using Fourier transform infrared (FT-IR) spectroscopy. As a result of the present experiment, it was found that DLC-coated Si is one of the most stable and useful substrates for IR spectroscopy in supercritical water.
Microstructural and Mechanical Properties of Polyester/Nanoclay Nanocomposites: Microstructure-Mixing Strategy Correlation
Authors: Dalir Hamid , Farahani Rouhollah D. , Nhim Vireya , Samson Benjamin , Lévesque Martin , Therriault Daniel
Published: April 2011

Different nanoclay mixing strategies using a three-roll mill and ultrasonication is proposed to obtain the desired polyester/nanoclay dispersion, intercalation, and exfoliation. The dispersion states of the modified nanoclay in polymer with 2, 4 and 6 wt% loading were characterized with X-ray diffraction, scanning electron microscopy (SEM), and low and high magnification transmission electron microscopy (TEM). The mechanical properties of the clay-reinforced polyester nanocomposites were a function of the nature and the content of the clay in the matrix. The nanocomposite containing 4 wt% modified Cloisite® 15A exhibits excellent improvement in modulus (by ~51%) and tensile strength (by ~12%) with a decrease in fracture strain (by ~26%) and fracture energy (by ~17%). These mechanical characteristic changes can be attributed to the dispersion, intercalation, and exfoliation of the nanoclays inside the polyester matrix.
Supercapacitor Based on Graphene – Polyaniline Nanocomposite Electrode
Authors: Gomez Humberto , Alvi Farah , Villalba Pedro , Ram Manoj. K. , Kumar Ashok
Published: April 2011

This paper aims to investigate the concept of high power density and wider voltage window supercapacitors based on graphene-conducting polymer electrodes. The high conductivity, wider tunable potential window, stability of the electrode material in the doped form, faster charge transfer rate, and short charging times in graphene (G)-polyaniline (PANI) systems, contribute to the design and fabrication of high performance supercapacitors. Novel chemistries were used to synthesize a higher electronic conducting nanocomposite material based on graphene and polyaniline. The G-PANI nanocomposites were characterized, where an interesting structure was observed using different ratios of graphene with the aniline monomer. The G-PANI nanocomposite materials has shown the specific capacitance of 300 to 500 F/g at a current density of 0.1A/g. Based on the present experimental findings, it could be conclude that the G-PANI polymer nanocomposite supercapacitor technology could be transformative, and could surpass the existing technologies when the present synthesized novel material approach will be taken.
In-situ XRD and FIB microscopy studies of the dynamics of intermetallic phase formation in thin layer Cu/Sn films for low-temperature isothermal diffusion soldering
Authors: Etschmaier Harald , Novák Jiří , Eder Hannes , Hadley Peter
Published: April 2011

In this contribution we report on the dynamics of the phase evolution in electrochemically deposited Sn thin films on copper coated substrates studied by in-situ X-ray diffraction (XRD) and Focused Ion Beam Microscopy (FIB). The data obtained is used to extract fundamental parameters such as the activation energy and the rate constant of the reaction. Results indicate that the formation of intermetallic phases in these thin layers, in which the grain size exceeds the layer thickness, is not limited by diffusion but rather by reaction kinetics.
Enhanced response characteristics of SnO2 thin film loaded with nanoscale catalytic clusters for Methane gas
Authors: Haridas Divya , Chowdhuri Arijit , Sreenivas K. , Gupta Vinay
Published: April 2011

In recent years, an increase in usage of methane gas in household and automobile industry has been observed. Detection of methane is always a great cause of concern for safety at home or automobile industries, productions in mines and chemical factories. This paper reports the response characteristics of rf-sputtered SnO2 thin films (90 nm thin) loaded with nanoscale catalytic clusters for detection of methane. Ultrathin (8 nm) metal and metal-oxide catalysts (Pt, Ag, Ni, Pd, Au, NiO, Au2O3) clusters are loaded over the surface SnO2 thin film. The SnO2-Pd cluster structure is found to exhibit an enhanced response (97.2%) for 200 ppm of methane at a relatively low operating temperature (220oC). The enhanced response is shown to be primarily due to the dominant roles played by both Fermi level energy control mechanism and spillover mechanism.
Near white light emission from ZnO nanostructures
Authors: Brahma Sanjaya , Jaiswal P. , Nanda K. K. , Kukreja L. M. , Shivashankar S.A.
Published: April 2011

We report white light emission from ZnO nanostructures in powder form, prepared by microwave irradiation-assisted chemical synthesis, in the presence of a structure directing agent. Determination of their crystallinity, actual shape, and orientation was made using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and optical properties have been studied through photoluminescence (PL), measured using He-Cd laser (325 nm) as the excitation source. There is a noticeable variation in the luminescence correlated with variation of process parameters, such as microwave power, duration of irradiation, and the type/concentration of surfactants. The CIE (Commission Internationale l’Eclairage) diagram shows that the luminescence lies in yellow region of the color space. As the luminescence from the powder of ZnO lies in the yellow region, it is possible to produce white light from the powder of ZnO by using a blue laser as the excitation source.
Fabrication of Photovoltaic Devices using Novel Organic Polymer/Nanostructure Blends
Authors: Black David , Salaoru Iulia , Paul Shashi
Published: April 2011

Organic photovoltaic devices offer a potentially cheap source of electrical power due to the relative ease of processing compared to silicon devices. Over the last decade the efficiency of these devices has improved significantly and the best devices are currently have >6% power conversion efficiency and ~100% quantum efficiency.

A novel blend of ferroelectric nanostructures, poly(3-hexylthiophene) (P3HT) and [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) has been used to fabricate hybrid organic and inorganic photovoltaic devices. These devices comprise a glass substrate coated with indium tin oxide (ITO) and an layer of PEDOT:PSS to form the first electrode. The active layer was deposited by spin coating and finally metallic top contacts have been added by thermal evaporation. The devices were characterized using standard current-voltage (IV) measurements under illuminated and dark conditions using an AM1.5 solar simulator and a source-voltage device and the results indicate a difference in efficiency compared to similar devices fabricated at the same time without the novel nanostructures. Additional UV-Vis measurements were used to determine the absorption characteristics of the active layers. The initial results suggest an improvement in the absorption of light in the visible region and higher open circuit voltages and short circuit currents compared to P3HT/PCBM alone.
Use of doped-YAG nanoparticles as down-converters for Photovoltaics
Authors: Raccurt Olivier , de Borniol Mervyn , Le Blevennec Gilles , Gerritsen Eric , Thony Philippe , Tebby Zoe
Published: April 2011

Increasing solar cell efficiency by using spectral conversion is addressed in this article. To that purpose rare-earth doped YAG nanoparticles exhibiting down-conversion and quantum cutting properties have been prepared. These nanoparticles have been synthesized with different concentrations of dopants in order to optimize the luminescence and the quantum cutting efficiency. Results on the incorporation of selected material into the encapsulating layer of c-Si based PV-modules are also presented. The effect of down-conversion has been demonstrated through the increase of photocurrent of encapsulated silicon solar cells.
pO2 stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ
Authors: Wagner Stefan F. , Taufall Simon , Niedrig Christian , Götz Holger , Menesklou Wolfgang , Baumann Stefan , Ivers-Tiffée Ellen
Published: April 2011

The mixed-conducting perovskite oxide Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), given its outstanding oxygen ionic and electronic transport properties, is considered a promising material composition for oxygen transport membranes (OTM) operated at high temperatures.

Its long-term stability under operating conditions is, however, still an important issue. Although the incompatibility of BSCF with CO2-containing atmospheres can be avoided by appropriate means (oxyfuel processes in the absence of carbon dioxide), the thermal as well as the chemical stability of BSCF itself are still under thorough investigation.

This work is focused on the stability of BSCF in the targeted temperature range for OTM applications (700…900 °C) and in atmospheres with low oxygen contents. Previous studies in literature suggest limited chemical stability below oxygen partial pressures pO2 of around 10-6 bar.

By using a coulometric titration method based on a zirconia “oxygen pump” setup, precise control of the oxygen partial pressure pO2 between 1 bar and 10-18 bar was facilitated. Combining electrical measurements on dense ceramic bulk samples performed as a function of pO2 with an XRD phase composition study of single phase BSCF powders subjected to various pO2 treatments, an assessment of the chemical stability of BSCF is facilitated as a function of oxygen partial pressure. It could thus be shown that the pO2 stability limit is considerably lower than previously assumed in literature.
Microwave Synthesis of Metallic Nanoparticles Supported on Porous Coordination Polymers: A Bi-functional Catalyst Design for CO2 Activation and Conversion
Authors: Abdelsayed Victor , Fan Yueying , Gardner Todd
Published: April 2011

The efficient separation and conversion of CO2 from power plant flue gases remains a significant and far reaching global goal. Partially, because of the high energy cost associated with CO2 separation which makes technologies, such as amine scrubbing and conventional sorbent materials, less attractive. In this work we have used a microwave-assisted method to prepare Mg-based porous coordination polymers (MOF-74) with open metal sites. The material shows a high CO2 uptake at room temperature mainly due to the high binding energy between the open Mg site (in the coordination polymer) and the oxygen atom of the adsorbed CO2 molecule. Our results show that the microwave-based Mg-MOF-74 shows superior properties compared to thermally prepared samples such as higher surface area, crystallinity and CO2 uptake. Pt nanoparticles (<5-10 nm) were deposited on the Mg-MOF-74 as manifested from the TEM results. The Pt nanoparticles were uniformly dispersed across the sample with more aggregations at higher Pt loadings. Different techniques were used to characterize the materials such as (BET surface area, XRD, SEM, EDS, TEM and TGA). These materials function as a bi-functional catalyst and sorbent material with the Mg-MOF-74 material responsible for CO2 capture and supported Pt nanoparticles responsible for its catalytic activity.
Synthesis and Dispersion of Ultra-Small Binary and Ternary Metal Oxide Nanoparticles for Dielectric Thin Films
Authors: Cheema Tarik A. , Taroata Dan , Schmid Guenter , Garnweitner Georg
Published: April 2011

Fabrication of dielectric thin films using dispersions of ultra-small ZrO2and BaTiO3nanoparticles with a low-temperature processing is reported. Highly crystalline and monodisperse cubic-ZrO2and tetragonal-BaTiO3nanoparticles were synthesized using non-aqueous approach. Post synthesis, nanoparticle dispersions were realized through chemical modification of their surface. The obtained dispersions were then employed for the fabrication of homogeneous and densely-packed dielectric thin films, verified through scanning electron microscopy.
Amorphous Photodiode with an Intermediate Contact for Improved Color Separation
Authors: Watty Krystian , Bablich Andreas , Seibel Konstantin , Merfort Christian , Boehm Markus
Published: April 2011

Most of actual photonic devices being sensitive in the visible (VIS) spectrum are based on crystalline silicon (x-Si). The production of x-Si requires an expensive high temperature process. The color reproduction with x-Si diodes additionally requires an integration of color filters [1] to realize a shift in spectral sensitivity. This work presents an amorphous silicon (a-Si:H) photodiode with an intermediate contact for color separation without color filters. Such detectors can be produced in a low cost and low temperature PECVD process, which allows their direct deposition on a custom specific ASIC [2]. Another advantage of a-Si:H is the up to 10 times higher light absorption compared to that of x-Si in the VIS spectrum [3]. The device consists of a metal (Cr) cathode, an amorphous NIP diode structure and a TCO (Al doped ZnO) anode. The I-layer includes an interior TCO contact buried between two P-layers. The thickness of this TCO layer is about 200 nm; the P-layers have a thickness of about 10 nm. The chromium cathode is sputtered on a glass substrate in a PVD process. The amorphous layers are deposited in a multi-chamber PECVD line; the buried and top TCO contacts are sputtered in the same line continuously under high-vacuum conditions. In a first photolithography step the top anode is patterned while the buried anode is uncovered. Afterwards, the diode must be patterned again, resulting in a final Cr, NIP-a-Si:H, TCO, PIP-a-Si:H and TCO multi-layer stack.

The spectral sensitivity of a common NIP diode can be shifted by external bias voltages. The spectral sensitivity at higher negative voltages overlays those of that at lower voltages and additionally shifts to longer wavelengths. The color reproduction is difficult; it can be improved by reducing the overlap of the spectral sensitivity [4]. The spectral response of the diodes presented in this work also can be shifted by the bias voltage. Furthermore, it can be split by substituting the disclosed anodes. The spectral response, using the cathode and top anode has a maximum at short wavelengths. If the diode between the interior anode and the cathode is used, the spectral sensitivity for longer wavelengths increases. Shorter wavelengths are blocked by the top part of the diode; it works like a filter. The presented device structure offers good prospects to improve color separation compared to currently existing detectors by using an additional intermediate contact.
Hydrostatically Coupled Dielectric Elastomer Actuators: New Opportunities for Haptics
Authors: Carpi Federico , Frediani Gabriele , De Rossi Danilo
Published: April 2011

Dielectric elastomer actuators (DEAs) have been demonstrated to represent today a high-performance technology for electromechanical transducers based on electroactive polymers. As a means to improve versatility and safety of DEAs for several fields of application, so-called ‘hydrostatically coupled’ DEAs (HC-DEAs) have recently been described. HC-DEAs are based on an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load, so as to enable hydrostatic transmission. This paper presents ongoing developments of bubble-like HC-DEAs and their promising potential application in the field of haptics. In particular, the first part of the paper describes a static and dynamic characterization of a prototype actuator made of two pre-stretched membranes (20 mm wide, 1.8 mm high, and 60 μm thick) of 3M VHB acrylic elastomer, coupled via silicone grease. The actuator exhibited a maximum stress of 1.3 kPa at 4.4 kV, a relative displacement of -80% at 4.4 kV, a -3dB bandwidth of 3 Hz, and a resonance frequency of 160 Hz. The second part of the paper presents possible applications of the tested actuator configuration for haptic interfaces. Two specific examples are considered. The first deals with a wearable tactile/haptic display used to provide users with tactile feedback during electronic navigation in virtual environments. The display consists of HC-DEAs arranged in contact with finger tips. As a second example of usage, an up-scaled prototype version of an 8-dots refreshable cell for dynamic Braille displays is shown. Each Braille pin consists of a miniature HC-DEA, with a diameter lower than 2 mm. Both types of applications clearly show the potential of the new technology and the prospective opportunities for haptics.
Effect of Trace Contaminants on PEM Fuel Cell Performance
Authors: Thampan Tony , Rocheleau Rick , Bethune Keith , Wheeler Douglas
Published: April 2011

At the Hawaii Fuel Cell Test Facility a systematic evaluation of the impact of impurities in hydrogen is underway to evaluate the effects on the performance of PEM fuel cells. Initial tests are being conducted using carbon monoxide and hydrocarbon contaminants. The effects of carbon monoxide poisons at atmospheric and pressurized operating conditions have shown a strong dependence on concentration of the impurity over the range 6.7 µmole/mole to 29.3 µmole/mole. Additionally, benzene and toluene were tested at 20 µmole/mole. Although both benzene and toluene showed no evidence of fuel cell degradation, on-line gas analysis of the exit anode stream showed that toluene hydrogenation occurs in the anode resulting in 90% conversion of the toluene to methyl-cyclohexane.
(Membrane) Attack of the Killer Radicals
Authors: Cipollini Ned Emidio
Published: April 2011

The conventional Fenton mechanism is reviewed and then slightly modified to incorporate additional data. Following the DuPont attack mechanism closely, we explain why the FER is proportional to the carboxylic acid end-group concentration in Fenton tests. We then make a case that in-cell testing introduces additional decay reactions operating locally in the membrane. These additional reactions explain the shape of the FER vs. time curve and why the FER is nearly independent of the carboxylate end group concentration. A semi-quantitative model is introduced to support the self consistency of the proposed reaction scheme.
Sol-Gel SiO2-Polymer Hybrid Heteropoly Acid-Based Proton-Exchange Membranes
Authors: Pern F. John , Turner John A. , Meng Fanqin , Herring Andrew M.
Published: April 2011

Heteropoly silicotungstic acid (STA)-based, cross-linked hybrid proton exchange membranes for intermediate-temperature (80°-120°C) fuel cell applications were fabricated by incorporating STA in a host matrix of binding silane, SiO2sol gel, ethylene methacrylate copolymer containing glycidyl methacrylate groups (PMG), and molecular cross-linker. The STA loading level relative to the sum of the PMG and a cross-linker exceeded 100 weight%. Upon curing at 145° under pressure, the composite membranes were nearly 100% cross-linked and were flexible, showed high thermal and chemical stability against Fenton’s reagent, and exhibited a break-in behavior during cyclic voltammetric (CV) scans. The best proton conductivity, which was obtained from CV results, decreased from ∼8-15 mS/cm at 80°C and 100% relative humidity (RH), to ∼1.5 mS/cm at 100°C and 46% RH, and ∼0.25 mS/cm at 120°C and 23%RH.
Functionalized ORMOSIL-Based Hybrid Membranes for Polymer Electrolyte Membrane Fuel Cells
Authors: Licoccia Silvia , D'Epifanio Alessandra , Di Vona Maria Luisa , Ahhmed Zakarya , Belitto Serafina , Marani Debora , D'Ottavi Cadia , Moroni Emiliano , Trombetta Marcella , Traversa Enrico
Published: April 2011

Sulfonated poly ether ether ketone (SPEEK) with a high degree of sulfonation (DS = 0.9) was mixed with a modified silane bearing a sulfonic acid function (sulfonated diphenylsilanediole, SDPDO).

Homogeneous composite membranes with several SPEEK:SDPDO ratios, were obtained. The addition of the ormosil significantly improved the water uptake and solubility properties of pure SPEEK.

The structural and electrochemical characteristics of the composite membranes were investigated by means of thermogravimetric analysis (TG), field emission scanning electron microscopy (FE-SEM), and electrochemical impedance spectroscopy (EIS). The conductivity values of the composites SPEEK/SDPDO demonstrated that they possess good proton transport characteristics, thus being suitable for application in Polymer Electrolyte Fuel Cells operating at intermediate temperature.
Hydrogen Production from Methane by Using Composite-Type Oxygen Permeable Membranes
Authors: Takamura Hitoshi , Ogawa Masayuki , Aizumi Yusuke , Kamegawa Atsunori , Okada Masuo
Published: April 2011

This paper describes preparation and methane reforming characteristics of a proto-type reformer based on a composite-type oxygen permeable membrane. The tape-cast membrane of Sm-doped CeO2 and 15 vol% MnFe2O4 composite was combined with ferric stainless steel separator with a same thermal expansion coefficient. For the reformer module, high CH4 conversion, CO and H2 selectivity of 96%, 84% and 89% were achieved, respectively. Based on C, H and O balances, oxygen permeation flux was found to be 5.7 mu-mol/cm2s. Joule heat caused by the oxygen permeation was estimated to be approximately 17.5 W, and this covered most part of heat required for reforming reactions.
Metal Oxide Modified Lithium Borohydrides for Reversible Hydrogen Storage
Authors: Au Ming , Jurgensen Arthur
Published: April 2011

The lithium borohydride has been modified by ball milling with metal oxides and metal chlorides as the additives. The modified lithium borohydrides released 9 wt% hydrogen starting from 473K. The dehydrided modified lithium borohydrides absorbed 7-9 wt% hydrogen at 873K and 7 MPa. The modification with additives reduced the dehydriding starting temperature from 673K to 473K and moderated the rehydrogenation conditions from 923K/15 MPa to 873K/7 MPa. XRD and SEM analysis revealed the formation of the intermediate compound that may play a key role in changing the reaction path resulting in the lower dehydriding temperature and reversibility. The additives reduced the dehydriding temperature and improve the reversibility, but it also reduced the hydrogen storage capacity.
Development and Characterization of Novel Complex Hydrides Synthesized via Molten State Processing
Authors: Zidan Ragaiy , Shanahan Kirk L , Anton Donald L. , Jurgensen Arthur R , Pittman Jennifer
Published: April 2011

This study is aimed at developing novel hydrides for hydrogen storage through a new synthesis technique utilizing high hydrogen overpressure at elevated temperatures denoted as Molten State Processing, MSP. This synthesis technique holds the potential of fusing different known complex hydrides at elevated temperatures and pressures to form new complexes having different sorption and thermodynamic properties. Complex hydrides produced by this method (e.g. NaMgH3, K3AlH6 and Na2LiAlH6) were identified through structural determination and thermodynamic characterization.
Proton Conducting Electrolyte Membranes based on Tungsten Oxide and Sulfonated Polyether Ether Ketone Hybrid Composites
Authors: Mecheri Barbara , D'Epifanio Alessandra , Di Vona Maria Luisa , Traversa Enrico , Licoccia Silvia , Miyayama Masaru
Published: April 2011

Composite membranes, prepared by mixing sulfonated polyether ether ketone (SPEEK) and WO3·2H2O in dimethylacetamide, were characterized by Thermogravimetry, Electrochemical Impedance Spectroscopy and Water Uptake measurements to evaluate their possible performance as proton exchange membranes (PEM). The body of results indicated the existence of a coordinative interaction between the water molecules of tungsten oxide and the sulfonic acid (-SO3H) groups of SPEEK. Moreover, EIS data demonstrated that the proton conductivity of the composite membranes is higher than both that of pure SPEEK and pure tungsten oxide, suggesting the presence of ion-rich regions where the proton transfer is favored. The SO3H - H2O interaction not only lead to enhancement of the proton conductivity of the membranes but also to improvement of their heat resistance as well as to decrease their water solubility.
Understanding the Mechanism of Hydrogen Adsorption into Metal-Organic Frameworks
Authors: Lee Tae-Bum , Kim Daejin , Choi Seung-Hoon , Yoon Ji Hye , Choi Sang Beom , Kim Jaheon
Published: April 2011

Hydrogen adsorption mechanism into the porous metal-organic frameworks (MOFs) has been studied by density functional theory calculation. The selected functionals for the prediction of interaction energies between hydrogen and potential adsorption sites of MOFs were utilized after the evaluation with the various functionals for interaction energy of H2···C6H6 model system. The adsorption energy of hydrogen molecule into MOFs was investigated with the consideration of the favorable adsorption sites and the orientations. We also calculated the second favorable adsorption sites by geometry optimization using every combination of two first absorbed hydrogen molecules. Based on the calculation of first and second adsorption sites and energies, it has been suggested that the hydrogen adsorption into MOFs follows a cooperative mechanism in which the initial metal sites initiate the propagation of the hydrogen adsorption on the whole frameworks. In addition, the interaction mode between the simple benzene ring with hydrogen is significantly changed when the benzene ring has been incorporated into the framework of MOFs.
Catalytic decomposition of methane over cerium-doped Ni Catalysts
Authors: González Oscar A. , Valenzuela Miguel A. , Wang Jin-An
Published: April 2011

Si-Ce-O mixed solids (50, 30, 10 and 5, Si/Ce molar ratio) were prepared by using Ce(NO3)3·6H2O as cerium source, tetraethyl orthosilicate (TEOS) as Si precursor and cetyltrimethylammonium bromide (CTABr) as synthesis template. The Ni catalysts were prepared by impregnation of the supports using Ni-acetilacetonate (30 wt.% Ni) as Ni source. The samples were characterized by: X-ray diffraction, temperature-programmed reduction (TPR), and TEM. The nickel reduction degree decreased with the addition of cerium, even in low concentration. When methane was decomposed over all the catalysts only hydrogen was obtained as a gaseous product. The addition of cerium brought about a significant increase in stability compared with Ni/SiO2 catalyst. These preliminary results indicated that CeO2 addition improves the dispersion of Ni particles leading to a better distribution of deposited carbon and increasing the lifetime of Ni particles.
High Hydrogen Permeability in Nb-Ti-Ni Eutectic Alloys Containing Much Primary (Nb, Ti) Phase
Authors: Ishikawa Kazuhiro , Luo Weimin , Aoki Kiyoshi
Published: April 2011

Microstructure, crystal structure and hydrogen permeability (Φ) of Nb-Ti-Ni alloys on the straight line connecting the compositions of the eutectic and the primary (Nb, Ti) phase have been investigated to develop the alloys showing high hydrogen permeability with a scanning electron microscope (SEM), an X-ray diffractometer (XRD), and a gas permeation apparatus, respectively. These alloys consist of the B2-TiNi compound and the bcc- (Nb, Ti) solid solution and are hydrogen permeable when they contain much amount of the eutectic phase. The values of Φ for these alloys increase with increasing temperature and Nb content. The Nb68Ti17Ni15alloy shows the highest Φ of [molH2m−1s−1Pa−0.5] at 673 K, which is 3.1 times higher than that of pure Pd. The present work demonstrates that the alloys showing the high Φ values are obtained on the straight line connecting the compositions of the eutectic and the primary phase.
Silica Sol-Gel Supported Nickel Nano-Catalyst for Hydrogen Production Using Microreactors
Authors: Shetty Krithi , Zhao Shihuai , Cao Wei , Seetala Naidu V. , Kuila Debasish
Published: April 2011

The goal of this research is to investigate the activities of a non-noble nano-catalyst (Ni/SiO2) using Si-microreactors for steam reforming of methanol to produce hydrogen for fuel cells. The supported catalyst was synthesized by sol-gel method using Ni (II) salts and Si(C2H5O)4 as starting materials. EDX results indicate that the actual loading of Ni (5-6%) is lower than the intended loading of 12 %. The specific surface area of the silica sol-gel encapsulated Ni nano-catalyst is 452 m2/g with an average pore size of ∼ 3 nm. Steam reforming reactions have been carried out in a microreactor with 50 µm channels in the temperature range of 180-240 °C and atmospheric pressure. Results show 53% conversion of methanol with a selectivity of 74 % to hydrogen at 5 l/min and 200 °C. The magnetic properties of the catalysts were performed using a Vibrating Sample Magnetometer (VSM) to study the activity of the catalysts before and after the steam reforming reactions. The VSM results indicate much higher activity in the microreactor compared to macro-reactor and Ni forms non-ferromagnetic species faster in the microreactor.
Oxygen flux and process analysis of hydrogen separation from water through mixed conducting membrane
Authors: Karthikeyan Annamalai , Cui Hengdong , Gopalan Srikanth , Pal Uday B.
Published: April 2011

Hydrogen synthesis and segregation from water splitting with simultaneous partial oxidation of methane can be achieved using MIEC membranes that conduct oxygen ions and electrons. The process offers hydrocarbon free hydrogen production on the feed side of the membrane (steam side) and syn-gas on the permeate side (methane side). A composite MIECs system comprising GdxCe1−xO2−x/2 (GDC) and GdxSr1−xTi1−yAlyO3 (GSTA) has been used and the hydrogen flux has been estimated. The oxygen diffusion coeffcient for oxygen transport through the bulk of the membrane and surface exchange coefficient of oxygen at the solid/gas interface were obtained using electrical conductivity relaxation (ECR) experiments and the hydrogen generation flux was measured for membranes of different thicknesses, with and without surface exchange catalysts for various experimental conditions.
Cobaltites as perspective thermoelectrics
Authors: Hejtmánek Jiri , Veverka Miroslav , Knižek Karel , Fujishiro Hiroyuki , Hebert Sylvie , Klein Yannick , Maignan Antoine , Bellouard Christine , Lenoir Bertrand
Published: April 2011

The recent material research of mixed cobalt oxides is strongly motivated by the potential of some of them to be used as chemically stable high temperature thermoelectric material. This fact together with both the theoretical and experimental ambitions to fulfill the severe criteria needed for efficient thermoelectric conversion intensified both their theoretical and experimental research. Nonetheless, despite the investigations of the prototype materials represented by 3D perovskites Ln1−xAxCoO3 (Ln = La, Y, rare-earth, A = alkaline-earth) and 2D cobaltites of NaxCoO2 type, the concise physical background of their transport and magnetic properties remain still a matter of debate. This is likely due to a fact that cobalt ions can be stabilized either in low-spin state (diamagnetic for “pure” Co3+), with filled t2g levels and empty eg states, or magnetic ones, with filled eg states. As the energy difference between respective states is due to comparable strength of crystal field and Hund's energies rather small, the thermodynamically most stable ground-state, with eventually different character of charge carriers, can be critically influenced by an interplay of additional degrees of freedom - orbital and charge. The challenge for unequivocal theoretical model represents the thermoelectric power of mixed cobaltites where, up to now, somewhat ambiguous models based either on “classical” approach, associated with diffusion of itinerant charge carriers, or more exotic - based on configurational entropy of quasi-itinerant carriers - are often used for similar materials. Simultaneously, the open question remains the assessment of the dominant mechanism of phonon scattering in 2D cobaltites.
Electronic Structure of AgPbmSbTem+2 Compounds – Implications on Thermoelectric Properties
Authors: Hoang Khang , Mahanti S. D. , Androulakis J. , Kanatzidis M. G.
Published: April 2011

Novel quaternary compounds AgPbmSbTem+2 (LAST-m) with different m values have been synthesized recently and some of these compounds show promising thermoelectric properties at high temperatures. The two end members of the series, PbTe (m=∞) and AgSbTe2 (m=0), are also known to be good thermoelectrics. In this paper, we discuss the results of ab initio electronic structure calculations for these two end members and for LAST-2 and LAST-14 to see how the electronic structure near the chemical potential μ evolves with m. Whereas PbTe and LAST-14 are narrow band gap semiconductors, the other two compounds show pseudo-gap structure. Even in the absence of a true gap, the rapidly varying density of states (DOS) near μ may be conducive to large Seebeck coefficient in LAST-2 and AgSbTe2.
Rhenium silicide as a new class of thermoelectric material
Authors: Inui Haruyuki
Published: April 2011

The microstructure, defect structure and thermoelectric properties of binary and some ternary Re silicide have been investigated as a new class if thermoelectric material. Binary Re silicide is identified to contain many Si vacancies, which are arranged in an ordered manner in the underlying tetragonal C11b structure so that the silicide is formulated to be ReSi1.75 with a monoclinic unit cell and contains four differently oriented domains accompanied by the twinned microstructure. The density and arrangement of Si vacancies can be controlled by ternary alloying. When the number of valence electrons of a ternary element is smaller than that for Re, the density of Si vacancies decreases with ternary additions, whereas the density of Si vacancies increases with ternary additions when the number of valence electrons of a ternary element is larger than that for Re. For both cases, the variation of the density of Si vacancies upon ternary alloying is accompanied by the introduction of the so-called shear structure.Binary ReSi1.75 exhibits nice thermoelectric properties as exemplified by the high value of dimensionless figure of merit (ZT) of 0.70 at 800 °C when measured along [001], although the ZT value along [100] is just moderately high. The ZT value is further increased to 0.8 with a small amount (2% substitution for Re) of Mo addition, by which an incommensurate microstructure is formed as result of extensive shear operation on the nano-scale.
Thermoelectric Properties of Tl2Te-Sb2Te3 Pseudo-Binary System
Authors: Kurisaki Ken , Goto Keita , Kosuga Atsuko , Muta Hiroaki , Yamanaka Shinsuke
Published: April 2011

Polycrystalline-sintered samples of thallium based substances, (Tl2Te)100−x(Sb2Te3)x (x= 0, 1, 5, 10), were prepared by melting Tl2Te and Sb2Te3 ingots followed by annealing in sealed quartz ampoules. The thermoelectric properties were measured from room temperature to around 600 K. The values of the Seebeck coefficient of all samples are positive, indicating a p-type conduction characteristic. The maximum value of the power factor is 6.53×10−4 Wm−1K−2 at 591 K obtained for x= 10 (Tl9SbTe6), which is about one order lower than those of state-of-the-art thermoelectric materials. All samples indicate an extremely low thermal conductivity, for example that of Tl2Te is approximately 0.35 Wm−1K−1 from room temperature to around 600 K. Although the electrical performance of the samples is not so good, the ZT value is relatively high due to the extremely low thermal conductivity. The maximum ZT value is 0.42 at 591 K obtained for Tl9SbTe6.
Extremely Low Thermal Conductivity Substances as Novel Thermoelectric Materials
Authors: Yamanaka Shinsuke , Kurosaki Ken , Kosuga Atsuko , Goto Keita , Muta Hiroaki
Published: April 2011

We have prepared polycrystalline bulk samples of various thallium compounds and measured their thermoelectric properties. The most remarkable point of the thermoelectric properties of the thallium compounds is the extremely low thermal conductivity. The state-of-the-art thermoelectric materials such as Bi2Te3 and TAGS materials indicate relatively low the thermal conductivity, around 1.5 W/m/K. However, the thermal conductivity of the thallium compounds is below 0.5 W/m/K; especially that of silver thallium tellurides is around 0.25 W/m/K at room temperature. This extremely low thermal conductivity leads a great advantage for an enhancement of the thermoelectric performance. In this paper, we report on the properties of some thallium compounds selected for study as novel thermoelectric materials. One of these compounds seems to have a thermoelectric figure of merit comparable to those of state-of-the-art materials.
Mechanism And Characterization Studies on Boron Carbides Deposited by Chemical Vapor Deposition Technique
Authors: Karaman Mustafa , Özbelge Hilmi Önder , Sezgi Naime Asli , Doğu Timur
Published: April 2011

Boron carbide was produced in an impinging jet CVD reactor from a gas mixture of BCl3, CH4 and H2. The mass transfer limitations on the reaction kinetics were minimised by the jet impingement on the substrate surface. XPS characterization of the produced deposits revealed a nearly pure boron carbide phase containing small amounts of oxy-boron and oxy-carbon species. After a detailed kinetic study, a reaction model was proposed to predict the rates of boron carbide and dichloroborane formation reactions. In this model, boron trichloride is adsorbed on the surface non-dissociatively, whereas hydrogen and methane are adsorbed dissociatively. BC is formed on the solid surface through the reaction of adsorbed boron trichloride with adsorbed methane in the form of CH3(s) (adsorbed CH3 on the surface). Produced BC is reacted in successive series reactions including adsorbed boron trichloride and adsorbed hydrogen. In the proposed mechanism, dichloroborane is produced only through the gas phase reaction between boron trichloride and hydrogen. The simultaneous fit of the experimental data to the model expression gave good fits for the boron carbide and dichloroborane formation reactions with the high correlation coefficient values.