bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACTThe 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

ABSTRACTFabrication 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

ABSTRACTMost 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

ABSTRACTDielectric 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

ABSTRACTAt 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

ABSTRACTThe 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

ABSTRACTHeteropoly 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

ABSTRACTSulfonated 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

ABSTRACTThis 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

AbstractThe 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

ABSTRACTThis 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

ABSTRACTComposite 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

ABSTRACTHydrogen 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

ABSTRACTSi-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

ABSTRACTMicrostructure, 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

ABSTRACTThe 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

ABSTRACTHydrogen 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

AbstractThe 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

ABSTRACTNovel 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.