bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of APCVD Growth Conditions on the Photocatalytic Behaviour of Titania Films
Authors: Yates Heather M. , Evans Philip , Sheel David W.
Published: September 2009

The ability of titania to photo-catalytically destroy organic pollutants has led to its use in many applications including anti-biological and self-cleaning materials. Various methods have been used to improve the efficiency of the photocatalytic process, including modifications to the sample morphology by improved crystallinity or increasing surface roughness and hence increasing the surface area and the efficiency in which the pollutant can be exposed to the active TiO2. However, this latter has to be balanced by the commercially driven need for transparent and hence thin films (< 40 nm), as generally the roughness (and photo-activity) increases with increased thickness of the deposited layer. In this paper we discuss the growth and characterisation of atmospheric pressure CVD grown colourless, transparent thin films. We propose, in particular, to show how the photocatalytic behaviour is affected by growth parameters and discuss this in relationship to factors such as morphology, roughness and crystallinity.
Dynamics of Pulsed DC Discharges Used for PACVD of a-C:H:Si
Authors: Traxler Margarethe , Puchhammer Alexander , Störi Herbert , Müller Thomas , Laimer Johann
Published: September 2009

Although a-C:H:Si is insulating, high quality a-C:H:Si coatings can be deposited by pulsed DC PACVD at moderate temperatures. In order to understand these results the discharge was investigated by different methods with microsecond resolution. It turned out that for a proper selection of the operation parameters the discharge conditions, as expressed in discharge current, total plasma light emission and discharge distribution, remain constant during most of the voltage pulse and also during an entire deposition run, thus enabling the afore mentioned good properties of a-C:H:Si coatings.
A Single-Step APCVD Route to Novel Dual Functionality: Self-Cleaning Biocidal Titania-Copper Films
Authors: Evans Philip , Ditta I. B. , Foster Howard , Sheel David W. , Steele Alex , Yates Heather M.
Published: September 2009

In this paper we report on biocidal self-cleaning coatings based on copper and titania composite films, grown in a single-step atmospheric pressure CVD process. The films were investigated to assess their potential to offer dual functionality of self-cleaning and biocidal films (under UV irradiation). The dual functionality was achieved by simultaneous delivery of the titania and copper precursors, and co-deposition in the APCVD reactor. It is shown that by careful choice of the experimental growth conditions, the composition of the films may be controlled to optimise both biocidal and 'self-clean' functionality.
Deposition of Germanium Nanowires from Digermane Precursor: Influence of the Substrate Pretreatment
Authors: Dřínek Vladislav , Fajgar Radek , Klementová Mariana , Subrt Jan
Published: September 2009

Germanium Nanowires (GeNWs) were synthesized by Low Pressure Chemical Vapor Deposition (LPCVD) of hexamethyldigermane (GeMe3)2 at temperature of 490 {degree sign}C and pressure of 90-100 Pa. GeNWs of several nanometers in diameter and a few microns in length were deposited onto various substrates - stainless steel, Fe, Mo, Ta, W, Si, and SiO2. Influence of surface pretreatment of the substrates (roughening of surface or Ge sputtering) is discussed in respect to the previously published theory of GeNW growth through the intermetallic alloy mechanism. The results conclude that another mechanism should be taken into account - the non-catalyst mechanism. Ge seeds necessary for triggering GeNW growth are formed by aggregation of Ge atoms/atom clusters/fragments which are stuck onto the substrate surface at the beginning of the process. The non-catalyst growth of GeNW triggered by such mechanism can be applied in growing GeNWs on semiconductors and insulators.
ArF Laser-induced Deposition of Carbon Encapsulated CoFe Nanoparticles
Authors: Fajgar Radek , Bastl Zdeněk , Subrt Jan , Murafa Nataliya , Maryško Miroslav
Published: September 2009

The decomposition of the gaseous acetylene - Fe(CO)5 - Co(CO)3(NO) mixtures induced by a single ArF laser pulse is a very efficient and novel method for formation of amorphous cobalt/iron alloy nanoparticles completely encapsulated in amorphous carbon shell. The properties of the CoFe(core)-carbon(shell) nanocomposites were examined by spectroscopy, microscopy and diffraction techniques. Magnetic measurements revealed the superparamagnetic behaviour of the as-prepared samples with diameter ≈ 5 nm at temperatures above 200K. The properties of the CoFe alloy nanoparticles annealed at 600, 900 and 1150oC were studied. Heating leads to structural changes in both the alloy core and the carbon shell. The cobalt/iron core crystallizes as syn-wairauite and carbon affords graphite outer part.
Memory Structures Based on the Self-organization of Cu Nanoparticles Deposited by Hot-Wire CVD on Polythiophene Layers
Authors: Dimitrakis Panagiotis , Papadimitropoulos Giorgos , Palilis Leonidas , Vasilopoulou Maria , Normand Pascal , Argitis Panagiotis , Davazoglou Dimitris
Published: September 2009

Two-terminal Al/P3HT/Cu-NPs/PMMA/Al memory structures have been fabricated on quartz substrates in cross-bar architecture. The characteristics of Cu-NPs on P3HT deposited by HW-CVD were investigated in terms of UV-VIS spectroscopy and AFM measurements. Part of these tri-layer structures exhibit unstable switching of conductivity between a high and a low resistance states, while the other exhibited significant NDR regions in the I-V characteristics of these devices at high voltages. Neither switching nor NDR phenomena were observed in samples without Cu-NPs. Further process and structure optimizations are needed for functional organic bistable memory devices.
Pulsed-Pressure MOCVD Science, Materials and Technology
Authors: Krumdieck Susan
Published: September 2009

Pulsed pressure processing from liquid MOCVD precursors has been studied over the past ten years. Extending the capabilities of CVD to applications like thermal barrier coatings, Solid Oxide Fuel Cells, and bio-integration coatings was the motivation for the original innovative concept. The systems engineering research has focused on development of a low-cost, high throughput method capable of providing high quality, uniform ceramic films on metal, ceramic or glass Pulsed pressure processing from liquid MOCVD precursors has been studied over the past ten years. Extending the capabilities of CVD to applications like thermal barrier coatings, Solid Oxide Fuel Cells, and bio-integration coatings was the motivation for the original innovative concept. The systems engineering research has focused on development of a low-cost, high throughput method capable of providing high quality, uniform ceramic films on metal, ceramic or glass objects with complex 3-D geometry. The MOCVD research has focused on using low-cost, low-hazard precursors to deposit the desired materials with the required properties. This paper reviews the fundamentals of the PP-MOCVD approach, the experience with precursors and thin films, and the advances of the system engineering toward several commercial applications.
Combinatorial CVD: New Oxy-nitride Photocatalysts
Authors: Parkin Ivan , Kafizas Andreas , Dunnill Charles W. , Hyett Geoffrey
Published: September 2009

Combinatorial atmospheric pressure chemical vapour deposition (cAPCVD) was used to synthesise a film with mixed gradating phases from pure orthorhombic pseudo-brookite Ti3-δO4N (0.06 < δ < 0.25) to interstitial N-doped anatase TiO2 on a single film. The film was characterized via Raman mapping and X-ray photoelectron spectroscopy (XPS). Film thicknesses were determined by Swanepoel method manipulations of UV-visible reflectance spectra and side-on scanning electron microscopy (SEM). Using a novel flat-bed digital scanning technique, the photocatalytic activity of the film to dichloroindophenol (DCIP) degradation under 365 nm light was also mapped. This allowed for the systematic investigation on the effect of pseudo-brookite: interstitial N-doped anatase phase composition, indicating pseudo-brookite to be the more photocatalytically active material. Films synthesized by the cAPCVD route analysed in conjunction with mapping analysis tools is a shortcut to identifying numerous phases and compositions and their functional property relationships on a single film, offering a rapid method for analysis of phase-space.
Mass Spectrometry as a Tool to Study MOCVD Process
Authors: Turgambaeva Asiya E. , Krisyuk Vladislav , Prud'Homme Nathalie , Vahlas Constantin
Published: September 2009

Application of two mass spectrometry (MS) techniques to study CVD from organometallic precursors is described. On line MS was used to explore the gas phase upon metal film production in a cold wall CVD reactor. In situ MS, where a miniature hot wall CVD reactor built in the TOF mass analyser, ensured the fast and uninterrupted recording of temperature/time dependence of gas phase composition upon low-pressure deposition without the sampling effect and allowed to study thermal decomposition mechanism of the precursor. The illustration how the on line MS was used for the validation of temperature conditions of CVD process is given. CpCuPEt3 (Cp = η5-C5H5, Et = C2H5) was used as a model precursor in this work. It was shown that deposition rate from the precursor slows down with time. The compatibility of data on gas phase composition provided by both MS techniques is discussed.
Analysis of Dominant Parameters in Structure and Properties of Cathode Catalyst Layer on PEM Fuel Cell Performance
Authors: Tabe Yutaka , Takamatsu Hiroyuki , Chikahisa Takemi
Published: September 2009

Because electron, proton, and oxygen are necessary for the cathode reaction in polymer electrolyte membrane fuel cells, achieving the optimum structure of electrode catalyst layer and the efficient transport of the reactants is significantly effective to reduce the usage of Pt catalyst. In this study, we develop a three-phase boundary and a cathode catalyst layer models to clarify structures appropriate for Pt high utilization, and the effects of the catalyst layer structures such as the porosity and the amount of polymer electrolyte, and the properties such as the oxygen solubility in the polymer are investigated using the models. From the calculation results, suitable structures, porosity and polymer electrolyte thickness, for gas diffusion and proton conduction are clarified. Further, it is presented that the solubility of oxygen in the polymer is one of the dominant factors and increasing in the solubility is extremely effective for reduction of the Pt usage.
Estimation of Optimum Operating Profile for PEMFC
Authors: Methekar Ravi , Ramadesigan Venkatasailanathan , Boovaragavan Vijayasekaran , Subramanian Venkat R. , Rice-York Cynthia
Published: September 2009

In this paper, we present a methodology to estimate the optimum operating condition for increasing the available power density from the Proton Exchange Membrane Fuel cell (PEMFC). This is achieved by implementing an optimization procedure on a mathematical model of the PEMFC. As a first step, the input condition in steady state is optimized and dynamic optimization is implemented on the transient model. It was observed that the first-principles model requires large computational time and hence we propose to reformulate the model to increase the computational efficiency and then use the same for dynamic optimization.
Structure Phase Transition and Oxygen Reduction Activity in Acidic Medium of Carbon-Supported Cobalt Selenide Nanoparticles
Authors: Feng Yongjun , He Ting , Alonso-Vante Nicolas
Published: September 2009

In this paper, we mainly investigated carbon-supported CoSe2 nanoparticles on the structure phase conversion under nitrogen and oxygen reduction reaction activity in 0.5 M H2SO4. The results of high-temperature powder X-ray diffraction and transmission electron microscopy techniques showed the structure conversion from orthorhombic at 300oC to cubic at 400oC and the increase of particle size from 2-3 nm to 5-10 nm. The electrochemical activity towards oxygen reduction reaction was improved from the orthorhombic to the cubic CoSe2 phase, for example, 3.5 electrons were calculated for the former and 3.7 electrons for the latter based on the average Koutecky-Levich slope at 0.2 V, 0.3 V and 0.4 V vs. RHE.
Membrane Degradation Mechanisms and Accelerated Durability Testing of Proton Exchange Membrane Fuel Cells
Authors: Fenton James M. , Rodgers Marianne P. , Slattery Darlene K. , Huang Xinyu , Mittal Vishal O. , Bonville Leonard J. , Kunz Harold R.
Published: September 2009

Molecular H2 and O2 reacting on the surface of Pt catalyst to form the membrane degrading species is the dominating membrane degradation mechanism in PEMFCs; not the formation of active oxygen species from H2O2 decomposition or the direct formation of active oxygen species in the oxygen reduction reaction. The source of H2 or O2 is from the reactant crossover through the membrane. The reaction mechanism is chemical in nature and depends upon the catalyst surface properties and the relative concentrations of H2 and O2 at the catalyst. The membrane degradation rate also depends on the residence time of the species in the membrane and the volume of the membrane. The sulfonic acid groups in the Nafion side chain are key to the mechanism by which the radical species attack the polymer.
Pseudo One-Dimensional Analysis of Polymer Electrolyte Fuel Cell Cold-Start
Authors: Wang Yun , Mishler Jeff , Mukherjee Partha P. , Mukundan Rangachary , Borup Rodney
Published: September 2009

This paper investigates the electrochemical kinetics, oxygen transport, and solid water formation in polymer electrolyte fuel cell (PEFC) during cold start. Following [Y. Wang, J. Electrochem. Soc., 154 (2007) B1041-B1048.], we develop a pseudo one-dimensional analysis, which enables the evaluation of the impact of ice volume fraction and temperature variations on cell performance during cold-start. The oxygen profile, starvation ice volume fraction, and relevant overpotentials are obtained. This study is valuable for studying the characteristics of PEFC cold-start.
In Situ Polymerized Wicks for Passive Water Management and Humidification of Dry Gases
Authors: Strickland Daniel G. , Santiago Juan G.
Published: September 2009

We develop a passive water management system that employs in-situ polymerized wick structures that can be integrated with state-of-the-art flow field designs (e.g., stamped metal or injection molded). We develop a simple model to examine the feasibility of using a pre-humidifier to evaporate fuel cell product water into the cathode inlet dry-gas stream. We then demonstrate the effectiveness of this idea in a custom-fabricated integrated wick system. We also experimentally study the performance of our novel wick design for flood mitigation in a parallel flow field using fully humidified gases.
Membrane Durability and Degradation under Dry Fuel Cell Operation Conditions
Authors: Li Jing , Wang Keping , Yang Yunsong
Published: September 2009

Membranes are a critical component of the fuel cell stack and must be durable in a wide range of operating conditions. In the present study, PFSA membranes were evaluated using accelerated stress testing (AST) methods of OCV and cyclic OCV under dry conditions at 95 {degree sign}C. PFSA membrane degradation rates were determined by measuring fluorine release rate (FRR) and thickness change under different fuel cell operating conditions. The FRR was found to increase with a decrease in inlet relative humidity (RH) and an increase in stack temperature. The degradation active energy (derived from the Arrherius equation) was approximately 932.8 JK-1mol-1. A cyclic OCV test was designed to simulate membrane degradation caused by both mechanical and chemical stresses. Mechanically reinforced membranes showed much longer lifetime in the COCV test as compared to membranes without reinforcement. Under present operating conditions, membrane degradation is shown to initiate from cathode side.
Synthesis and Evaluation of Heat-treated, Cyanamide-derived Non-precious Catalysts for Oxygen Reduction
Authors: Chung Hoon T. , Johnston Christina M. , Zelenay Piotr
Published: September 2009

Metal-nitrogen-carbon type (M-N-C type) non-precious catalysts have been prepared using cyanamide as the nitrogen precursor and pyrolysis to improve the activity and stability. Good activity has been observed for the best catalyst prepared with 1050{degree sign}C pyrolysis: E1/2 = 0.77 V by RDE, and current density = 80 mA at 0.80 V in H2/O2 fuel cell testing. M-N-C catalysts prepared using cyanamide as a nitrogen source show a complex dependence of activity on pyrolysis temperature: first increasing (up to 900{degree sign}C), then decreasing (1000{degree sign}C), before increasing again (1050{degree sign}C). The reappearance of activity may relate to an increase in defects induced at higher temperature, such as a greater exposure of the edges of graphene planes. The increased hydrophilicity of the sample after pyrolysis at 1050{degree sign}C suggests this outcome. Further study will be required to confirm the hypothesis.
Dealloyed Nanoporous Metals for PEM Fuel Cell Catalysis
Authors: Erlebacher Jonah , Snyder Joshua
Published: September 2009

Although the majority of PEM fuel cell catalysts are made of nanoparticles, similar surface area/volume, specific surface area, and precious metal loading can be made by using ultrathin (~100 nm) nanoporous metal membranes. We discuss here how ultrathin porous membranes can be made using electrochemical dealloying, and how to integrate such membranes into functional fuel cells. Dealloying is the selective dissolution of one or more components from a non-porous precursor alloy. Under the right electrochemical conditions, the remaining alloy component(s) are driven to diffuse along the alloy/electrolyte interface to form a porous metal with pores even smaller than 5 nm. Nanoporous metals can be intrinsically catalytic toward oxygen reduction, or can be coated with thin catalyst layers to form low Pt core-shell catalysts. Using nanoporous metal electrodes for fuel cell catalysis may remove stability issues associated with carbon supports, and opens new avenues for catalyst design.
Thin Film Platinum Alloys for Use as Catalyst Materials in Fuel Cells
Authors: Hays Charles C. , Kulleck James , Haines Brennan , Narayanan S. R.
Published: September 2009

Measurements of the structural and electrochemical properties of nanostructured thin film alloys in the ternary series Pt-Co-Zr are presented. These alloys have been studied to determine the influence of early transition metal element additions on the catalytic response and chemical stability of platinum-group-metal (PGM) alloys in acid electrolytes. The thin film compositions in the Pt-Co-Zr system were prepared via co-sputtering and the films exhibit a (111) crystallographic orientation. Alloys with Pt-metal contents of less than 50 At. % are stable in 0.1 M perchloric acid electrolytes, and are electrochemically active for the oxygen reduction reaction (ORR). The ORR kinetic currents at 0.9 V are comparable to Pt. The alloys have been cycled over the range 0.0 to 1.2 V NHE, with no degradation of the electrode surface area or decrease in electrochemical performance observed. Our results suggest that Pt-Co-Zr alloys with reduced PGM contents may be competitive with Pt-catalysts.
Degradation Behavior of Membrane in PEFCs under Pressurized Condition
Authors: Asano Koichi , Mugikura Yoshihiro
Published: September 2009

In order to investigate degradation behavior of the membrane in polymer electrolyte fuel cells during the load cycling tests, their tests were carried out under different operating pressures. The amount of hydrogen that diffused across the membrane and the amount of precipitated Pt inside the membrane under high pressure were larger than those under normal pressure. There were hardly any changes in the membrane under normal pressure. On the other hand, the membrane was considerably degraded around the Pt band under high pressure. Further, under high pressure, at the initial stage of the load cycling test, an increase in the fluoride ion emission rate corresponded to a rapid decrease in the electrochemical surface area. It was inferred that the Pt band formation and the membrane degradation occurred at the initial stage of the load cycling tests. In addition, it was confirmed that membrane degradation was accelerated under high pressure.
Estimation of Water Contents of Polymer Electrolytes from 1H NMR Peak of Confined Water
Authors: Nosaka Atsuko Y. , Nosaka Yoshio
Published: September 2009

Water molecules confined in perfluorinated ionomer membranes which are widely used for polymer electrolyte fuel cells, presented apparently a single 1H NMR peak in hydrated states because of the rapid exchange among the water molecules at the distinct segments of the polymer. The peak shifts to the lower field with decreasing the water content due to the decrease of the fraction of the bulk water molecules which present a peak at higher field. The chemical shifts were found to be well correlated with the peak area. The water peak for MEA (Membrane Electrode Assembly) showed also similar behaviors to the membranes. From the relationship between the chemical shift and the peak area of the confined water peak we demonstrated the potential that the chemical shift could be utilized to estimate the water content in the hydrated membranes and MEA.
Current Distribution of a PEMFC under CO Poisoning
Authors: Murahashi Toshiaki , Mitsumoto Takumi , Nishiyama Enju
Published: September 2009

The current density distribution along the flow channel of a PEMFC was investigated under CO poisoning using a transparent cell modified with finely distributed current collectors. For a counter-flow configuration, significant movement of the current density peak towards the cathode exit was observed as the CO concentration in the anode gas increased, which clearly indicates that the current density is significantly reduced at the cathode inlet area and increased at the cathode exit. These results are consistent with previous experimental results that showed water droplet distributions on the cathode moved towards the cathode exit when CO at 10-100 ppm levels was introduced into the anode gas. Comparison of the experimental and calculated results revealed that movement of the current density peak under high CO was related to reduction of the exchange current density, which was caused by the significant loss of CO coverage on the anode catalyst surface.
Conductivity and Thermal Behaviour of Sulfonated ABS Membranes for Fuel Cell Applications
Authors: Mariano Domingues da Silva Carolina , Silva Adney Luis A. , Pacheco Robson , Rocco Ana Maria
Published: September 2009

In the present work, proton conductive membranes based on poly(acrylonitrile-co-butadiene-co-styrene) (ABS) were obtained by sulfonation. The sulfonic acid ABS (ABS-SO3H) membranes exhibited thermal stability near 370 oC, similarly to the ABS original polymer. DSC curves of the sulfonic acid membranes showed two glass transition temperatures, associated with thermal processes taking place at the polymer main chain and at the hydrophilic domains. These hydrated regions are formed by water molecules and dissociated sulfonic acid groups [-SO3-(H2O)nH+], as pointed out in other works. Electrochemical impedance spectroscopy evidenced the conductive-capacitive behaviour of ABS-SO3H membranes, which exhibited an Ahrrenius-like conductivity dependence with temperature, from 7.6×10-6 Ω-1cm-1 at 20 oC and 1.4×10-5 Ω-1cm-1 at 80 oC (ABS-SO3H 2:1).
Preparation and Characterization of Catalysts Supported on Catalytically Channeled Carbon Nanofibers for Direct Methanol Fuel Cells
Authors: Jang Jin-Sung , Lim Seongyop , Kim Sang-Kyung , Jung Doo-Hwan , Peck Dong-Hyun , Lee Young-Seak
Published: September 2009

Particularly channeled carbon nanofibers (CNF) were applied to the catalyst support for preparation of electrode catalysts for DMFC. Porous CNFs were prepared through selective gasification of CNF with nano-sized catalyst particles such as Ru under prescribed conditions. The channel width, length, and channeling direction were dependent on the catalyst nature and preparation conditions. The channeled CNFs-supported PtRu catalysts were tested in methanol oxidation and DMFC single cells.
Complex Capacitance Analysis of Ionic Resistance and Interfacial Capacitance within Cathode Layers of PEMFC and DMFC Electrodes
Authors: Jang Jong Hyun , Jeon S. , Kim S.-K. , Lee S.-Y. , Cho Eun Ae , Kim Hyoung Juhn , Han J. , Lim Tae Hoon
Published: September 2009

For PEMFC and DMFC catalyst layers, a complex capacitance analysis of impedance data was developed to evaluate the catalyst/ionomer interfacial capacitance and ionic resistance of ionomer networks, without non-linear data fitting. Assuming no Faradaic reactions, equivalent circuits for the catalyst layers were suggested, and it was confirmed that the plots of the real and imaginary parts as a function of ac frequency are determined by the catalyst/ionomer interfacial capacitances and RC time constants, which are important characteristics for high fuel cell performances. By performing a complex capacitance analysis, the interfacial capacitances and ionic resistances of PEMFC MEAs can be experimentally obtained at various relative humidities, proving that the catalytic activity in fuel cell operation depends on ionic resistances as well as on the catalyst/ionomer interfacial area. In addition, the effects of various MEA preparation methods on the ionomer distributions and DMFC performances were analyzed by a complex capacitance analysis.
Polysiloxane Based Membranes for High Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFC)
Authors: Harms Corinna , Wilhelm Michaela , Grathwohl Georg
Published: September 2009

Membranes with benzimidazole as proton conducting group and siloxanes as backbone were prepared by cross-linking siloxane monomers. The influence of additional amounts of silanol terminated linear polydimethylsiloxane (PDMS) on glass transition temperature and proton conductivity under anhydrous conditions were investigated. The new membrane materials possess high thermal stabilities up to 286{degree sign}C and exhibit proton conductivities up to 2 x 10-4 S/cm at 160{degree sign}C.
Influence of Operating Parameters on Start/Stop Induced Degradation in Polymer Electrolyte Fuel Cells
Authors: Linse Nicolas , Aellig Christof , Wokaun Alexander , Scherer Guenther G. , Gubler Lorenz
Published: September 2009

In order to investigate the influence of temperature, reactant gas humidification and the application of an auxiliary load on start/stop induced fuel cell degradation under application relevant conditions, alternating purging of the anode electrode with hydrogen and air was used to shut-down and start-up the fuel cell. It was found that loss of active catalyst surface area only significantly influences fuel cell performance at low temperatures and reactant gas humidifications. Under harsh conditions, performance decrease is dominated by mass transport losses which are caused by carbon corrosion induced changes in the structure of the catalyst layer. Measurements of the CO2 content in the cathode exhaust gas showed that corrosion rate depends linearly on water vapor partial pressure for temperatures up to 80{degree sign}C. Due to a strongly increased driving voltage and the longer duration of the detrimental potential, performance loss was dramatically increased for the cell cycled without auxiliary load.
Electrochemical Filter Design for the Removal of CO Contaminant in Reformate Hydrogen
Authors: Balasubramanian Sivagaminathan , Holland Charles E. , Weidner John W.
Published: September 2009

Carbon monoxide contamination in reformate hydrogen decreases the performance of the proton exchange membrane (PEM) fuel cells significantly through anode poisoning. The cost, in terms of parasitic power losses and reactor volume for decreasing the CO concentration to a tolerable level, can be high. Here, we demonstrate a PEM-based twin-cell electrochemical filter that offers the possibility of a compact and efficient device to reduce the CO concentration to 10 ppm or lower. The potential and flow are switched between the two filter cells so that alternative CO adsorption and oxidation occur in each cell, while providing a continuous flow of H2 to a fuel cell. The effects of filter switching time and applied potential on CO concentration of gas exiting the filter are presented for a 1,000 ppm CO in nitrogen anode stream and a 4% H2/N2 cathode stream flowing at 100 and 40 cc/min, respectively.
HiL - A Tool for Development and Validation of Fuel Cell Stack Models and Prototypes
Authors: Randolf Guenter
Published: September 2009

Modeling, HiL-simulation and dynamic prototype validation becomes more demanded as the diversity and complexity of fuel cell applications increases. Particularly the high dynamics of automotive employment and a reduced time-to-market are fertile ground for dynamic models. The testing and simulation system introduced in this paper is a tool that supports every step of fuel cell stack development from modeling in the early design phase to end-of-line testing. As traditional testing methodology does not account for high system dynamics, transient analysis and deterministic simulation, a new concept was designed from scratch. Based on self-contained, inherently safe real-time controller and a high speed cell diagnosis system, this tool helps to derive model parameters from dynamic measurements, co-simulates the model with the physical unit, easily adapts to different testing scenarios and allows conceiving end-of-line product validation.
Preparation of Ultra-Thin Catalyst Layers by Piezo-electric Printer for PEMFCs Applications
Authors: Saha Madhu S. , Paul Devproshad , Malevich Dzmitry , Peppley Brant , Karan Kunal
Published: September 2009

An improved catalyst deposition methodology, based on a piezoelectric printing technique, for fabricating catalyst coated membrane (CCM) with thin catalyst layers (1−5 μm) and corresponding ultra-low Pt loadings (0.02−0.10 mg/cm2) has been developed. The performance of these CCMs was examined in proton exchange membrane fuel cells (PEMFCs). Neglecting the anode contributions, the mass activity, i.e. current density per unit mass of Pt, at 900 mV for the printed CCM is nearly 120 mA/mgPt which is 2.5 times higher than that for CCM fabricated by conventional spraying method (47.5 mA/mgPt).
Search for Phosphors for use in Displays and Lightings using Heuristics-based Combinatorial Materials Science
Authors: Kumar Sharma Asish , Sohn Kee-Sun
Published: September 2009

Multi objective genetic algorithm assisted combinatorial material search (MOGACMS) strategies have been applied to multi-compositional inorganic oxide systems to search for new green phosphors as a cold cathode fluorescent lamp (CCFL) for a back light unit (BLU) in liquid crystal display (LCD) applications. In addition, we especially emphasized on a troublesome, complex problem of high throughput experimentation (HTE), the inconsistency, which is frequently faced by combinatorial materials scientist. For this study, experimental inconsistency and material property were selected as dual objective functions that were simultaneously optimized. Specifically, in an attempt to search for promising phosphors with high reproducibility, photoluminescence (PL) intensity was maximized and experimental inconsistency was minimized by the MOGACMS strategy.
Investigation of Electronic Excitations of Pure and Ce Doped 12CaO•7Al2O3 Using Luminescence Spectroscopy
Authors: Kirm Marco , Avarmaa Tea , Denks Viktor , Feldbach Eduard , Kunnus Kristjan , Maaroos Aarne , Tõldsepp Eliko , Liblik Peeter
Published: September 2009

Pure and Ce doped nanoporous 12CaO•7Al2O3 (C12A7) oxides were synthesized using self-propagating combustion method and solid state reaction. Time-resolved photoluminescence method at low temperatures was applied in studies of powder samples and ceramics, which were obtained in a melt-solidification process partly replacing encaged oxygen ions with electrons. In pure C12A7 with the encaged electrons broad luminescence bands peaked at 3.3 and 5.0 eV were revealed. The first one corresponds to the luminescence due to the encaged oxygen ions and latter one is assigned to the recombination of electrons and holes localized on the framework oxygen ions. Ce doping introduces emission band at 3.0 eV due to 5d-4f transitions with several decay components in nanosecond range. The Ce 5d-4f luminescence is efficiently excited through Ce intra-center absorption as well as through energy transfer processes in the intrinsic absorption region of C12A7 above energy gap at 7.0 eV.
Synthesis and Characterization of Zn2SiO4:Mn2+ Nanophosphors Prepared from Different Zn Source in Liquid Precursor by Flame Spray Pyrolysis
Authors: Lee Jae Seok , Khanna Aniruddh , Oh Myounghwan , Ranade Madhav B. , Singh Rajiv K.
Published: September 2009

Zn2SiO4:Mn2+ nanophosphors were synthesized by flame spray pyrolysis (FSP) from different liquid precursors. Luminescence and crystalline properties were investigated as different Zn-source materials in aqueous precursor. Mn-doped zinc silicate (Zn2SiO4:Mn2+) crystalline structures were annealed low temperature of 1000° for 1hr. The emission peak was found at 525 nm for green emitting phosphor. The influence of different experimental conditions such as liquid precursor from different Zn-source and annealing temperature on both crystallinity and the luminescence properties of Zn2SiO4:Mn2+ nanophosphors were investigated.
Optical Properties of Cr(III) doped YAG Nanoceramics
Authors: Gluchowski P. , Hreniak D. , Lojkowski Witold , Strek Wieslaw
Published: September 2009

The Cr3+ doped Y3Al5O12 ceramics composed of nanosized grains were fabricated by the low temperature high pressure sintering technique. The photo - and cathodoluminescence spectra of Cr3+:Y3Al5O12 nanoceramics were measured. The effect of applied pressure on luminescence properties of Cr3+ doped Y3Al5O12 nanoceramics was investigated.
The Photoluminescence Properties of Nano-phosphors Modified by Planetary Ball Mill
Authors: Shin Jung-Hoo , Choi Sung-Woo , Hong Seong-Hyeon , Kwon Soon-Jae , Seo Soo-Yeon , Kim Hyun-Sik
Published: September 2009

Y(P,V)O4:Eu phosphor prepared by liquid phase precursor(LPP) method was modified by planetary ball milling and nano-sized powder with spherical shape was successfully obtained. A post-annealing was conducted at 1100 ° for 1 h to enhance the crystallinity and photoluminescence property.
Breast Cancer Cell Imaging using Semiconductor Quantum Dots
Authors: Xu Hengyi , Aguilar Zoraida P. , Su Huaipeng , Dixon John , Wei Hua , Wang Andrew
Published: September 2009

We report the development of early stage detection of breast cancer cells using quantum dots (QDs) as fluorescent signal generator for detection. The QDs based imaging of breast cancer cells involved two kinds of antibodies: the first was for labeling the cells and the second was for imaging the breast cancer cells. Anti-Her2/neu (10Ab) was used for labeling the captured SK-BR3 cells. The second antibody against anti-Her2/neu (20Ab) that was conjugated to QDs (20Ab~QDs) forms the complete assay, SK-BR3 + 10Ab + 20Ab~QDs, to generate the fluorescent cells for imaging. Fluorescent images of the complete assay for SK-BR3 cells were evaluated under a microscope with a UV light source. The preliminary results showed that the breast cancer cell SK-BR3 in the complete assay were successfully observed as fluorescent cells that had brighter signals compared with those labeled with organic dye using similar parameters and the same number of cells.
Characteristics of Silicon Nanocrystals Embedded in the Amorphous-Silicon Carbide Films Deposited by Cat-CVD at Low Temperature for Optoelectronics Applications
Authors: Hwang Jae-Dam , Lee Kyoung-Min , Lee Youn-Jin , Jang Seunghun , Han Moonsup , Won Sunghwan , Sok Junghyun , Park Kyoungwan , Hong Wan-Shick
Published: September 2009

Si/SiC composite films, namely, Si nanocrystals in a-SiC matrix material, were deposited by using Cat-CVD. Photoluminescence characteristics of a-SiC thin films prepared with various gas ratio R=[CH4]/[SiH4] were investigated. Fourier-transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) measurements composition ratio of a-SiC films. It shows different composition ratio between R > 10 and R < 10. Photoluminescence (PL) intensity was changed before and after thermal annealing at various temperatures. The PL intensity was increased after annealing peak position was shift short wavelength range.
Manufacturing of a Nanocrystal-based LED by Layer-by-Layer Deposition
Authors: Eychmüller Alexander , Otto Tobias , Mundra Paul , Schelter Matthias , Gaponik Nikolai
Published: September 2009

The manufacturing of nanocrystal based LEDs with the aid of the layer-by-layer deposition technique is presented and discussed. The technique is generally applicable for the fabrication of LEDs efficiently emitting in the wide spectral region from the UV-blue to the Near-Infrared.
Characterizations of Sidewall Reflected GaN-based LEDs using Self-aligned Nanorod Arrays as Localized Photonic Crystals
Authors: Cheng Yun-Wei , Pan Kun-Mao , Chen Liang-Yi , Ke Min-Yung , Chen Cheng-Pin , Huang JianJang
Published: September 2009

GaN-based light emitting diodes encompassed with self-aligned nanorod arrays of three distribution densities were designed and fabricated. Light diffraction behaviors are characterized by considering the radiation profiles as well as the angular spectra of those nanorod structures. We demonstrate that the device with the less regular and less dense nanorod (with a fill factor 0.19) distribution has the highest enhancement factor. As we regard the nanorod arrays as localized photonic crystals, the enhancement is due to a large varying lattice constant as well as the leaky mode operation when the emission wavelength falls within the photonic band-gap. Meanwhile the light emission directionality is more obvious when the guided modes are phase matched to the radiation modes that lie above the cut-off frequency of the Brillouin zone boundaries.
Effect of Doping on the Optical and Structural Properties of ZnO Thin Films Prepared by RF Diode Sputtering
Authors: Shtereva Krasimira , Tvarozek Vladimir , Netrvalova Marie , Sutta Pavol , Novotny Ivan , Pullmannova Andrea
Published: September 2009

Nitrogen-doped zinc oxide thin films (ZnO:N), and aluminum-nitrogen co-doped zinc oxide thin films (ZnO:Al:N), were deposited on Corning glass substrates by RF diode sputtering. The nitrogen (N2) content in the working gas varied from 0 to 100 %. XRD patterns revealed improving of the crystalline structure and stronger expressed c-axis preferential orientation of the aluminum-nitrogen co-doped films compared to nitrogen-doped films. The estimated crystallite size varied from 140 to 8 nm, depending on the N2 content. The transmittance spectra of ZnO:N and ZnO:Al:N films were acquired over the wavelength range of 200 < λ < 1000 nm. All nitrogen-doped and Al-N2 co-doped films were colored as a result of the increase absorption near the band edge. Optical band gap (Eg) of the ZnO:N and ZnO:Al:N thin films decreases with increase of the N2 content in the working gas.
Hypocretin/orexin increases the expression of steroidogenic enzymes in human adrenocortical NCI H295R cells
Authors: Wenzel Jan , Grabinski Nicole , Knopp Cordula A. , Dendorfer Andreas , Ramanjaneya Manjunath , Randeva Harpal S. , Ehrhart-Bornstein Monika , Dominiak Peter , Jöhren Olaf
Published: September 2009

Hypocretins/orexins act through two receptor subtypes: OX1 and OX2. Outside the brain, orexin receptors are expressed in adrenal glands, where orexins stimulate the release of glucocorticoids. To further address the regulation of steroidogenesis, we analyzed the effect of orexins on the expression of steroidogenic enzymes in human adrenocortical National Cancer Institute (NCI) H295R cells by qPCR. In NCI H295R cells, OX2 receptors were highly expressed, as they were in human adrenal glands. After treatment of NCI H295R cells with orexin A for 12–24 h, the cortisol synthesis rate was significantly increased, whereas 30 min of treatment showed no effect. While CYP11B1 and CYP11B2 mRNA levels were increased already at earlier time points, the expression of HSD3B2 and CYP21 mRNA was significantly up-regulated after treatment with orexin A for 12 h. Likewise, orexin B increased CYP21 and HSD3B2 mRNA levels showing, however, a lower potency compared with orexin A. The mRNA levels of CYP11A and CYP17 were unaffected by orexin A. OX2 receptor mRNA levels were down-regulated after 12 and 24 h of orexin A treatment. Orexin A increased intracellular Ca2+ but not cAMP concentrations in NCI H295R cells. Furthermore, inhibition of PKC and MAPK kinase/ERK kinase (MEK1/2) prevented the increase of HSD3B2 expression by orexin A. Accordingly, orexin A treatment of NCI H295R cells markedly enhanced ERK1/2 phosphorylation that was prevented by PKC and, in part, PKA inhibition. In conclusion, orexins may influence adrenal steroidogenesis by differential regulation of the expression of steroidogenic enzymes involving Ca2+, as well as PKC-ERK1/2 signaling.
Expression of Insulin Receptor Isoform A and Insulin-like Growth Factor-1 Receptor in Human Acute Myelogenous Leukemia: Effect of the Dual-Receptor Inhibitor BMS-536924 In vitro
Authors: Wahner Hendrickson Andrea E. , Haluska Paul , Schneider Paula A. , Loegering David A. , Peterson Kevin L. , Attar Ricardo , Smith B. Douglas , Erlichman Charles , Gottardis Marco , Karp Judith E. , Carboni Joan M. , Kaufmann Scott H.
Published: September 2009

The insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R) are receptor tyrosine kinases that participate in mitogenic and antiapoptotic signaling in normal and neoplastic epithelia. In the present study, immunoblotting and reverse transcription-PCR demonstrated expression of IGF1R and IR isoform A in acute myelogenous leukemia (AML) cell lines as well as in >80% of clinical AML isolates. Treatment with insulin enhanced signaling through the Akt and MEK1/2 pathways as well as survival of serum-starved AML cell lines. Conversely, treatment with BMS-536924, a dual IGF1R/IR kinase inhibitor that is undergoing preclinical testing, inhibited constitutive receptor phosphorylation as well as downstream signaling through MEK1/2 and Akt. These changes inhibited proliferation and, in some AML cell lines, induced apoptosis at submicromolar concentrations. Likewise, BMS-536924 inhibited leukemic colony formation in CD34+ clinical AML samples in vitro. Collectively, these results not only indicate that expression of IGF1R and IR isoform A is common in AML but also show that interruption of signaling from these receptors inhibits proliferation in clinical AML isolates. Accordingly, further investigation of IGF1R/IR axis as a potential therapeutic target in AML appears warranted. [Cancer Res 2009;69(19):7635–43]
An A13 Repeat within the 3′-Untranslated Region of Epidermal Growth Factor Receptor (EGFR) Is Frequently Mutated in Microsatellite Instability Colon Cancers and Is Associated with Increased EGFR Expression
Authors: Yuan Ziqiang , Shin Joongho , Wilson Andrew , Goel Sanjay , Ling Yi-He , Ahmed Naseem , Dopeso Higinio , Jhawer Minaxi , Nasser Shannon , Montagna Cristina , Fordyce Kenneth , Augenlicht Leonard H. , Aaltonen Lauri A. , Arango Diego , Weber Thomas K. , Mariadason John M.
Published: September 2009

Colorectal cancers (CRC) with microsatellite instability (MSI) have clinical, pathologic, genetic, and epigenetic features distinct from microsatellite-stable CRC. Examination of epidermal growth factor receptor (EGFR) mRNA and protein expression levels in a panel of colon cancer cell lines identified strong expression of EGFR in multiple cell lines with MSI. Although no relationship between EGFR overexpression and the length of a CA dinucleotide repeat in intron 1 was observed, a variant A13/A14 repeat sequence within the 3′-untranslated region (3′-UTR) of the EGFR gene was identified, which was mutated by either mononucleotide or dinucleotide adenosine deletions in 64% of MSI cell lines and 69% of MSI colon tumors. Using a Tet-Off system, we show that this mutation increases EGFR mRNA stability in colon cancer cells, providing a mechanistic basis for EGFR overexpression in MSI colon cancer cell lines. To determine whether this mutation is a driver or a bystander event in MSI colon cancer, we examined the effect of pharmacologic and molecular inhibition of EGFR in EGFR 3′-UTR mutant MSI cell lines. Cell lines with an EGFR 3′-UTR mutation and that were wild-type (WT) for downstream signaling mediators in the Ras/BRAF and PIK3CA/PTEN pathways were sensitive to EGFR inhibition, whereas those harboring mutations in these signaling mediators were not. Furthermore, in cell lines WT for downstream signaling mediators, those with EGFR 3′-UTR mutations were more sensitive to EGFR inhibition than EGFR 3′-UTR WT cells, suggesting that this mutation provides a growth advantage to this subset of MSI colon tumors. [Cancer Res 2009;69(19):7811–8]
Role of SV40 Integration Site at Chromosomal Interval 1q21.1 in Immortalized CRL2504 Cells
Authors: Liu Jinglan , Kaur Gurpreet , Zhawar Vikramjit K. , Zimonjic Drazen B. , Popescu Nicholas C. , Kandpal Raj P. , Athwal Raghbir S.
Published: September 2009

We have applied a functional gene transfer strategy to show the importance of viral integration site in cellular immortalization. The large tumor antigen of SV40 is capable of extending the cellular life span by sequestering tumor suppressor proteins pRB and p53 in virus-transformed human cells. Although SV40 large T antigen is essential, it is not sufficient for cellular immortalization, suggesting that additional alterations in cellular genes are required to attain infinite proliferation. We show here that the disruption of human chromosomal interval at 1q21.1 by SV40 integration can be an essential step for cellular immortalization. The transfer of a 150-kb bacterial artificial chromosome (BAC) clone, RP364B14, corresponding to viral integration site in CRL2504 cells, reverted their immortal phenotype. Interestingly, the BAC transfer clones of CRL2504 cells displayed characteristics of either senescence as shown by β-galactosidase activity or apoptosis as revealed by positive staining with M30 CytoDEATH antibody. The SV40 integration at 1q21.1, in the vicinity of epidermal differentiation complex (EDC) genes, resulted in the down-regulation of the filaggrin (FLG) gene that is part of the EDC. FLG gene expression was increased in BAC transfer senescent and apoptotic clones. Our results suggest that the disruption of native genomic sequence by SV40 may alter expression of genes involved in senescence and apoptosis by modulating chromatin structure. These studies imply that identification of genes located in the vicinity of viral integration sites in human cancers may be helpful in developing new diagnostic and therapeutic strategies. [Cancer Res 2009;69(19):7819–25]