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Sample records for in-situ surface passivation

  1. Dramatic reduction of surface recombination by in situ surface passivation of silicon nanowires.

    Science.gov (United States)

    Dan, Yaping; Seo, Kwanyong; Takei, Kuniharu; Meza, Jhim H; Javey, Ali; Crozier, Kenneth B

    2011-06-08

    Nanowires have unique optical properties and are considered as important building blocks for energy harvesting applications such as solar cells. However, due to their large surface-to-volume ratios, the recombination of charge carriers through surface states reduces the carrier diffusion lengths in nanowires a few orders of magnitude, often resulting in the low efficiency (a few percent or less) of nanowire-based solar cells. Reducing the recombination by surface passivation is crucial for the realization of high-performance nanosized optoelectronic devices but remains largely unexplored. Here we show that a thin layer of amorphous silicon (a-Si) coated on a single-crystalline silicon nanowire, forming a core-shell structure in situ in the vapor-liquid-solid process, reduces the surface recombination nearly 2 orders of magnitude. Under illumination of modulated light, we measure a greater than 90-fold improvement in the photosensitivity of individual core-shell nanowires, compared to regular nanowires without shell. Simulations of the optical absorption of the nanowires indicate that the strong absorption of the a-Si shell contributes to this effect, but we conclude that the effect is mainly due to the enhanced carrier lifetime by surface passivation.

  2. Enhanced luminescence of near-surface quantum wells passivated in situ by InP

    Energy Technology Data Exchange (ETDEWEB)

    Lipsanen, H.; Sopanen, M.; Taskinen, M.; Tulkki, J. [Helsinki Univ. of Technology, Espoo (Finland). Optoelectronics Lab.; Ahopelto, J. [VTT Electronics, Espoo (Finland)

    1996-12-31

    The authors have studied the optical properties of MOVPE grown Al{sub x}Ga{sub 1{minus}x}As/GaAs structures passivated by in situ deposition of InP on the surface. One monolayer of InP was used for the passivation. The surface recombination was studied by photoluminescence measurements of near-surface Al{sub 0.22}Ga{sub 0.78}As/GaAs quantum wells. The luminescence intensity of the passivated samples increased by about five orders of magnitude for quantum wells located at less than 5 nm from the surface as compared to unpassivated samples. Furthermore, the authors observed a blueshift of 15 meV for a passivated surface quantum well. The effect of the thin InP layer on the Fermi level pinning on the surface was studied by photoreflectance of a surface-i-n{sup +} sample. The pinning position was reduced by 0.3 eV from the mid-bandgap value.

  3. In situ application of stir bar sorptive extraction as a passive sampling technique for the monitoring of agricultural pesticides in surface waters.

    Science.gov (United States)

    Assoumani, Azziz; Lissalde, Sophie; Margoum, Christelle; Mazzella, Nicolas; Coquery, Marina

    2013-10-01

    Grab sampling and automated sampling are not suitable or logistically too constraining for the monitoring of pesticides in dynamic streams located in agricultural watersheds. In this work, we applied stir bar sorptive extraction (SBSE) Twisters® directly in two small rivers of a French vineyard (herein referred to as "passive SBSE"), for periods of one or two weeks during a month, for the passive sampling of 19 agricultural pesticides. We performed qualitative and semi-quantitative comparisons of the performances of passive SBSE firstly to automated sampling coupled to analytical SBSE, and secondly to the polar organic chemical integrative sampler (POCIS), a well-known passive sampler for hydrophilic micropollutants. Applying passive SBSE in river waters allowed the quantification of more pesticides and in greater amounts than analytical SBSE as shown for samples collected concurrently. Also, passive SBSE and POCIS proved to be complementary techniques in terms of detected molecules; but only passive SBSE was able to integrate a concentration peak triggered by a quick flood event that lasted 5 h. Passive SBSE could be an interesting tool for the monitoring of moderately hydrophobic to hydrophobic organic micropollutants in changing hydrosystems. In this purpose, further studies will focus on the accumulation kinetics of target pesticides and the determination of their sampling rates. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. In-situ IR reflexion spectroscopy characterization of the passivation layer developed on the surface of lithium electrodes in organic medium; Passivation de surface: une nouvelle voie pour reduire l`autodecharge dans les batteries rechargeables a ions lithium LiMn{sub 2}O{sub 4}/Li

    Energy Technology Data Exchange (ETDEWEB)

    Barusseau, S. [Alcatel Alsthom Recherche, 91 - Marcoussis (France); Perton, F. [SAFT, Advanced and Industrial Battery Group, 86 - Poitiers (France); Rakotondrainibe, A.; Lamy, C. [Poitiers Univ., 86 (France). Laboratoire de Chimie 1, ``Electrochimie et Interactions``

    1996-12-31

    the development of lithium metal batteries is hindered by the bad reversibility of the Li{sup +}/Li pair, due to dendrites formation which limits the amount of active matter and can generate short-circuits. The chemical and electrochemical phenomena which take place at the electrode/organic electrolyte interface lead to the formation of a complex passivation film which is of prime importance for the functioning of this type of batteries. The in-situ infrared reflection spectroscopy is well adapted to the chemical study of the passivation layer. Two different techniques were used: the substraction normalized interfacial transform infrared spectroscopy (SNIFTIRS) and the electro-chemically modulated infrared reflectance spectroscopy. These methods have shown that the passivation layer that develops on the surface of the lithium electrode in contact with organic solutions (propylene carbonate, ethylene carbonate and dimethoxyethane) is mainly made of lithium alkyl carbonates (ROCO{sub 2}Li) and lithium carbonates (Li{sub 2}CO{sub 3}). (J.S.) 14 refs.

  5. Method of passivating semiconductor surfaces

    Science.gov (United States)

    Wanlass, Mark W.

    1990-01-01

    A method of passivating Group III-V or II-VI semiconductor compound surfaces. The method includes selecting a passivating material having a lattice constant substantially mismatched to the lattice constant of the semiconductor compound. The passivating material is then grown as an ultrathin layer of passivating material on the surface of the Group III-V or II-VI semiconductor compound. The passivating material is grown to a thickness sufficient to maintain a coherent interface between the ultrathin passivating material and the semiconductor compound. In addition, a device formed from such method is also disclosed.

  6. Si{sub 3}N{sub 4} layers for the in-situ passivation of GaN-based HEMT structures

    Energy Technology Data Exchange (ETDEWEB)

    Yunin, P. A., E-mail: yunin@ipmras.ru; Drozdov, Yu. N.; Drozdov, M. N.; Korolev, S. A.; Okhapkin, A. I.; Khrykin, O. I.; Shashkin, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2015-11-15

    A method for the in situ passivation of GaN-based structures with silicon nitride in the growth chamber of a metal organic vapor phase epitaxy (MOVPE) reactor is described. The structural and electrical properties of the obtained layers are investigated. The in situ and ex situ passivation of transistor structures with silicon nitride in an electron-beam-evaporation device are compared. It is shown that ex situ passivation changes neither the initial carrier concentration nor the mobility. In situ passivation makes it possible to protect the structure surface against uncontrollable degradation upon the finishing of growth and extraction to atmosphere. In the in situ passivated structure, the carrier concentration increases and the mobility decreases. This effect should be taken into account when manufacturing passivated GaN-based transistor structures.

  7. In-Situ Cleaning, Passivation, Functionalization, and Atomic Layer Deposition on Germanium and Silicon-Germanium

    Science.gov (United States)

    Kaufman-Osborn, Tobin Adar

    In recent years, germanium (Ge) and silicon-germanium (SiGe) have drawn significant interest as replacements of conventional silicon in the search for alternative materials for use in complementary metal-oxide-semiconductor (CMOS) devices due to their high electron and hole mobilities. In order to effectively implement Ge or SiGe as a replacement for silicon, two major challenges must be overcome: non-disruptive cleaning and surface passivation/functionalization. As electrical devices are increasingly scaled, it becomes especially crucial to effectively clean each unit cell on the Ge/SiGe surface without causing major disruption or damage to the surface. If air-induced defects or contaminants persist on the surface after cleaning, these defect sites may be un-reactive for functionalization and thereby will hinder device performance and/or the ability to aggressively scale device size. If a cleaning method is too aggressive leaving a rough or disordered surface, this can lower the mobility at the interface which will worsen device performance. For these reasons, it is necessary to develop a non-disruptive cleaning process that cleans each unit cell leaving a flat, ordered, and reactive surface. Once the Ge or SiGe surface is cleaned, in order to achieve a good electrical quality interface and a high nucleation density on the surface, all surface atoms must be passivated and functionalized allowing for aggressive device scaling. The interface must remain electrically passive in order to not inhibit electrical performance of the device. This study uses scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy (XPS) to develop and analyze a completely in-situ non-disruptive cleaning method of the Ge surface using H2O2(g) and atomic hydrogen. After cleaning, the Ge or SiGe surface is passivated and functionalized using H2O2(g) as a method to improve upon the conventional H2O(g) passivation method by more than

  8. Reducing the cytotoxicity of inhalable engineered nanoparticles via in situ passivation with biocompatible materials

    Energy Technology Data Exchange (ETDEWEB)

    Byeon, Jeong Hoon, E-mail: postjb@yu.ac.kr [School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Park, Jae Hong; Peters, Thomas M. [Department of Occupational and Environmental Health, University of Iowa, IA 52242 (United States); Roberts, Jeffrey T., E-mail: jtrob@purdue.edu [Department of Chemistry, Purdue University, IN 47907 (United States)

    2015-07-15

    Highlights: • The cytotoxicity of model welding particles was modulated through in situ passivation. • Model welding particles were incorporated with chitosan nanoparticles for passivation. • In vitro assay revealed that the passivated particles had a lower cytotoxicity. • Passivation with chitosan adhesive or graphite paste could also reduce cytotoxicity. • This method would be suitable for efficient reduction of inhalable toxic components. - Abstract: The cytotoxicity of model welding nanoparticles was modulated through in situ passivation with soluble biocompatible materials. A passivation process consisting of a spark discharge particle generator coupled to a collison atomizer as a co-flow or counter-flow configuration was used to incorporate the model nanoparticles with chitosan. The tested model welding nanoparticles are inhaled and that A549 cells are a human lung epithelial cell line. Measurements of in vitro cytotoxicity in A549 cells revealed that the passivated nanoparticles had a lower cytotoxicity (>65% in average cell viability, counter-flow) than the untreated model nanoparticles. Moreover, the co-flow incorporation between the nanoparticles and chitosan induced passivation of the nanoparticles, and the average cell viability increased by >80% compared to the model welding nanoparticles. As a more convenient way (additional chitosan generation and incorporation devices may not be required), other passivation strategies through a modification of the welding rod with chitosan adhesive and graphite paste did also enhance average cell viability (>58%). The approach outlined in this work is potentially generalizable as a new platform, using only biocompatible materials in situ, to treat nanoparticles before they are inhaled.

  9. In situ calibration of three passive samplers for the monitoring of steroid hormones in wastewater.

    Science.gov (United States)

    Škodová, Alena; Prokeš, Roman; Šimek, Zdeněk; Vrana, Branislav

    2016-12-01

    In situ extraction of steroid hormones from waste water using adsorption-based integrative passive samplers represents a promising approach for their monitoring in water at ultra-trace concentrations. Three passive samplers, namely a POCIS, a Chemcatcher fitted with an Empore SDB-RPS disk, and an Empore SDB-RPS disk-based sampler with enhanced water flow, were calibrated in situ in treated municipal wastewater for the purpose of monitoring five estrogens (17-β-estradiol, 17-α-estradiol, 17-α-ethinylestradiol, estrone and estriol) at sub ng per litre concentrations. Uptake of steroids to samplers during 14-day exposure in wastewater was compared with steroid concentrations in daily collected composite water samples. Sampling rates were obtained from a numerical solution of first order uptake kinetics equations describing the uptake of compounds into a passive sampler over time. Mass transfer of steroids in the Chemcatcher fitted with naked Empore disks was more than two times faster than in the POCIS sampler. The uptake capacity of the applied Empore disk was not sufficient for integrative uptake of all tested steroids during the entire 14-day exposure. Time-weighted average concentrations of steroids estimated at concentrations in units of ngL(-1) using the in situ-calibrated samplers were within a factor of two from values obtained using composite water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. In situ ellipsometry of Cu surfaces immersed in benzotriazole-hydrogen peroxide solutions

    Science.gov (United States)

    Kondoh, Eiichi; Kawakami, Tatsuya; Watanabe, Mitsuhiro; Jin, Lianhua; Hamada, Satomi; Shima, Shohei; Hiyama, Hirokuni

    2016-06-01

    In the chemical mechanical polishing (CMP) of Cu, the Cu surface is oxidized and is concurrently removed by the mechanical function of an abrasive. Surface oxidation can lead to severe surface corrosion, and to prevent this, a corrosion inhibitor is added to slurries. Accurate understanding of the competition between oxidation and passivation is essential for advanced Cu CMP technologies. In this work, layer formation on clean Cu surfaces in benzotriazole (BTA), H2O2, and BTA-H2O2 aqueous solutions was studied by in situ spectroscopic ellipsometry. Time changes of ellipsometric parameters are discussed with respect to BTA and H2O2 concentrations. It was found that the BTA adsorbs onto the Cu surface and the adsorbed BTA transforms into a Cu-BTA complex in about 3 min after the onset of adsorption. The BTA/complex layer passivates the Cu surface against oxidation by H2O2.

  11. A novel method for the in situ calibration of flow effects on a phosphate passive sampler.

    Science.gov (United States)

    Sara O'Brien, Dominique; Chiswell, Barry; Mueller, Jochen F

    2009-01-01

    Monitoring of nutrients including phosphate in the aquatic environment remains a challenge. In the last decade passive sampling techniques have been developed that facilitates the time integrated monitoring of phosphate (P) through the use of an iron hydroxide (ferrihydrite) to sequester dissolved phosphate from solution. These methods rely on established techniques to negate the effects of flow (and associated turbulence) and control the rate at which chemicals accumulate within passive samplers. In this study we present a phosphate sampler within which a suspension of ferrihydrite is contained behind a commercially available membrane. Accumulation of dissolved phosphates into the P-sampler is governed by the rate at which ions are diffusing through the membrane and the water boundary layer (WBL). As the WBL changes subject to flow we have adopted an in situ calibration technique based on the dissolution of gypsum to predict the change in the rate of uptake dependent on flow. Here we demonstrate that the loss of gypsum from the passive flow monitor (PFM) can be used to predict the sampling rate (the volume of water extracted per day) for phosphate as a function of water velocity. The outcome of this study presents a new in-field tool for more accurate prediction of the effect of flow/turbulence on the uptake kinetics into passive samplers that is controlled by the diffusion of the chemical of interest through the stagnant water boundary layer.

  12. A new application of passive samplers as indicators of in-situ biodegradation processes.

    Science.gov (United States)

    Belles, Angel; Alary, Claire; Criquet, Justine; Billon, Gabriel

    2016-12-01

    In this paper, a method for evaluating the in-situ degradation of nitro polycyclic aromatic hydrocarbons (nitro-PAH) in sediments is presented. The methodology is adapted from the passive sampler technique, which commonly uses the dissipation rate of labeled compounds loaded in passive sampler devices to sense the environmental conditions of exposure. In the present study, polymeric passive samplers (made of polyethylene strips) loaded with a set of labeled polycyclic aromatic hydrocarbons (PAH) and nitro-PAH were immersed in sediments (in field and laboratory conditions) to track the degradation processes. This approach is theoretically based on the fact that a degradation process induces a steeper concentration gradient of the labeled compounds in the surrounding sediment, thereby increasing their compound dissipation rates compared with their dissipation in abiotic conditions. Postulating that the degradation magnitude is the same for the labeled compounds loaded in polyethylene strips and for their native homologs that are potentially present in the sediment, the field degradation of 3 nitro-PAH (2-nitro-fluorene, 1-nitro-pyrene, 6-nitro-chrysene) was semi-quantitatively analyzed using the developed method.

  13. Thermal stability and in situ SiN passivation of InAlN/GaN high electron mobility heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Lugani, L.; Carlin, J.-F.; Py, M. A.; Grandjean, N. [ICMP, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2014-09-15

    We investigate the thermal stability of nearly lattice-matched InAlN layers under metal organic vapor phase epitaxy conditions for temperatures >800 °C and show that they are not fully stable. In particular, InAlN top layers undergo degradation during high temperature annealing due to a surface related process, which causes the loss of crystal quality. This strongly impacts the transport properties of InAlN/GaN HEMT heterostructures; in particular, the mobility is significantly reduced. However, we demonstrate that high thermal stability can be achieved by capping with a GaN layer as thin as 0.5 nm. Those findings enabled us to realize in situ passivated HEMT heterostructures with state of the art transport properties.

  14. In Situ Instrumentation for Sub-Surface Planetary Geochemistry

    Science.gov (United States)

    Bodnarik, J.; Evans, L.; Floyd, S.; Lim, L.; McClanahan, T.; Namkung, M.; Parsons, A.; Schweitzer, J.; Starr, R.; Trombka, J.

    2010-01-01

    Novel instrumentation is under development at NASA's Goddard Space Flight Center, building upon earth-based techniques for hostile environments, to infer geochemical processes important to formation and evolution of solid bodies in our Solar System. A prototype instrument, the Pulsed Neutron Generator Gamma Ray and Neutron Detectors (PNG-GRAND), has a 14 MeV pulsed neutron generator coupled with gamma ray and neutron detectors to measure quantitative elemental concentrations and bulk densities of a number of major, minor and trace elements at or below the surfaces with approximately a meter-sized spatial resolution down to depths of about 50 cm without the need to drill. PNG-GRAND's in situ a meter-scale measurements and adaptability to a variety of extreme space environments will complement orbital kilometer-scale and in-situ millimeter scale elemental and mineralogical measurements to provide a more complete picture of the geochemistry of planets, moons, asteroids and comets.

  15. Probing the surface of colloidal nanomaterials with potentiometry in situ.

    Science.gov (United States)

    Fedin, Igor; Talapin, Dmitri V

    2014-08-13

    Colloidal nanomaterials represent an important branch of modern chemistry. However, we have very little understanding of molecular processes that occur at the nanocrystal (NC) surface during synthesis and post-synthetic modifications. Here we show that potentiometry can be used to study the surface of colloidal NCs under realistic reaction conditions. Potentiometric titrations of CdSe and InP nanostructures provide information on the active surface area, the affinity of ligands to the NC surface, and the surface reaction kinetics. These studies can be carried out at different temperatures in polar and nonpolar media for NCs of different sizes and shapes. In situ potentiometry can provide real-time feedback during synthesis of core-shell nanostructures.

  16. Surface passivation for CdTe devices

    Energy Technology Data Exchange (ETDEWEB)

    Reese, Matthew O.; Perkins, Craig L.; Burst, James M.; Gessert, Timothy A.; Barnes, Teresa M.; Metzger, Wyatt K.

    2017-08-01

    In one embodiment, a method for surface passivation for CdTe devices is provided. The method includes adjusting a stoichiometry of a surface of a CdTe material layer such that the surface becomes at least one of stoichiometric or Cd-rich; and reconstructing a crystalline lattice at the surface of the CdTe material layer by annealing the adjusted surface.

  17. Smart, passive sun facing surfaces

    Science.gov (United States)

    Hively, Lee M.

    1996-01-01

    An article adapted for selectively utilizing solar radiation comprises an absorptive surface and a reflective surface, the absorptive surface and the reflective surface oriented to absorb solar radiation when the sun is in a relatively low position, and to reflect solar radiation when the sun is in a relatively high position.

  18. In situ ellipsometric study of surface immobilization of flagellar filaments

    Energy Technology Data Exchange (ETDEWEB)

    Kurunczi, S., E-mail: kurunczi@mfa.kfki.hu [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Nemeth, A.; Huelber, T. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Kozma, P. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Petrik, P. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Jankovics, H. [Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Sebestyen, A. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Vonderviszt, F. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Institute of Enzymology, Karolina ut 29-33, Budapest, H-1113 (Hungary); and others

    2010-10-15

    Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors. In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications. Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking. Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of 300-1500 nm bound to the surface. The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts. As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption.

  19. Superacid Passivation of Crystalline Silicon Surfaces.

    Science.gov (United States)

    Bullock, James; Kiriya, Daisuke; Grant, Nicholas; Azcatl, Angelica; Hettick, Mark; Kho, Teng; Phang, Pheng; Sio, Hang C; Yan, Di; Macdonald, Daniel; Quevedo-Lopez, Manuel A; Wallace, Robert M; Cuevas, Andres; Javey, Ali

    2016-09-14

    The reduction of parasitic recombination processes commonly occurring within the silicon crystal and at its surfaces is of primary importance in crystalline silicon devices, particularly in photovoltaics. Here we explore a simple, room temperature treatment, involving a nonaqueous solution of the superacid bis(trifluoromethane)sulfonimide, to temporarily deactivate recombination centers at the surface. We show that this treatment leads to a significant enhancement in optoelectronic properties of the silicon wafer, attaining a level of surface passivation in line with state-of-the-art dielectric passivation films. Finally, we demonstrate its advantage as a bulk lifetime and process cleanliness monitor, establishing its compatibility with large area photoluminescence imaging in the process.

  20. Development of a passive, in situ, integrative sampler for hydrophilic organic contaminants in aquatic environments

    Science.gov (United States)

    Alvarez, D.A.; Petty, J.D.; Huckins, J.N.; Jones-Lepp, T. L.; Getting, D.T.; Goddard, J.P.; Manahan, S.E.

    2004-01-01

    Increasingly it is being realized that a holistic hazard assessment of complex environmental contaminant mixtures requires data on the concentrations of hydrophilic organic contaminants including new generation pesticides, pharmaceuticals, personal care products, and many chemicals associated with household, industrial, and agricultural wastes. To address this issue, we developed a passive in situ sampling device (the polar organic chemical integrative sampler [POCIS]) that integratively concentrates trace levels of complex mixtures of hydrophilic environmental contaminants, enables the determination of their time-weighted average water concentrations, and provides a method of estimating the potential exposure of aquatic organisms to the complex mixture of waterborne contaminants. Using a prototype sampler, linear uptake of selected herbicides and pharmaceuticals with log KowS < 4.0 was observed for up to 56 d. Estimation of the ambient water concentrations of chemicals of interest is achieved by using appropriate uptake models and determination of POCIS sampling rates for appropriate exposure conditions. Use of POCIS in field validation studies targeting the herbicide diuron in the United Kingdom resulted in the detection of the chemical at estimated concentrations of 190 to 600 ng/L. These values are in agreement with reported levels found in traditional grab samples taken concurrently.

  1. Foreword: In situ gas surface interactions: approaching realistic conditions

    Science.gov (United States)

    Lundgren, Edvin; Over, Herbert

    2008-03-01

    This special issue is devoted to the application of in situ surface-sensitive techniques in the elucidation of catalysed reactions at (model) catalyst surfaces. Both reaction intermediates and the nature of the catalytically active phase are the targets of these investigations. In situ surface science techniques are also used to study the interaction of water with surfaces under realistic conditions. Since 80% of all technical chemicals are manufactured by utilizing (heterogeneous) catalysis, scientific understanding and technological development of catalysis are of central practical importance in modern society [1]. Heterogeneously catalysed reactions take place at the gas/solid interface. Therefore one of the major topics in surface chemistry and physics is closely related to heterogeneous catalysis, with the aim of developing novel catalysts and to improve catalysts' performances on the basis of atomic scale based knowledge. Despite the economical and environmental rewards—if such a goal is achieved—and despite 40 years of intensive research, practical catalysis is still safely in a black box: the reactivity and selectivity of a catalyst are commercially still optimized on a trial and error basis, applying the high throughput screening approach. The reason for this discrepancy between ambition and reality lies in the inherent complexity of the catalytic system, consisting of the working catalyst and the interaction of the catalyst with the reactant mixture. Practical (solid) catalysts consist of metal or oxide nanoparticles which are dispersed and stabilized on a support and which may be promoted by means of additives. These particles catalyse a reaction in pressures as high as 100 bar. Practical catalysis is in general considered to be far too complex for gaining atomic-scale understanding of the mechanism of the catalysed reaction of an industrial catalyst during its operation. Therefore it has been necessary to introduce idealization and simplification of

  2. In-Situ calibration of POCIS for the sampling of polar pesticides and metabolites in surface water

    OpenAIRE

    Ibrahim, Imtiaz; Togola, Anne; Gonzalez, Catherine

    2013-01-01

    on line version; International audience; Over the past years, passive sampling devices have been successfully used for the monitoring of various pollutants in water. The present work studied the uptake kinetics in surface water of ten polar pesticides and metabolites, using pharmaceutical POCIS samplers. The aim was to determine sampling rates from in-situ calibration and to compare results with those obtained earlier under laboratory conditions, with the final objective of assessing the impa...

  3. Improved in-situ methods for determining land surface emissivity

    Science.gov (United States)

    Göttsche, Frank; Olesen, Folke; Hulley, Glynn

    2014-05-01

    The accurate validation of LST satellite products, such as the operational LST retrieved by the Land Surface Analysis - Satellite Application Facility (LSA-SAF), requires accurate knowledge of emissivity for the areas observed by the ground radiometers as well as for the area observed by the satellite sensor. Especially over arid regions, the relatively high uncertainty in land surface emissivity (LSE) limits the accuracy with which land surface temperature (LST) can be retrieved from thermal infrared (TIR) radiance measurements. LSE uncertainty affects LST obtained from satellite measurements and in-situ radiance measurements alike. Furthermore, direct comparisons between satellite sensors and ground based sensors are complicated by spatial scale mismatch: ground radiometers usually observe some 10 m2, whereas satellite sensors typically observe between 1 km2 and 100 km2. Therefore, validation sites have to be carefully selected and need to be characterised on the scale of the ground radiometer as well as on the scale of the satellite pixel. The permanent stations near Gobabeb (Namibia; hyper-arid desert climate) and Dahra (Senegal; hot-arid steppe-prairie climate) are two of KIT's four dedicated LST validation stations. Gobabeb station is located on vast and flat gravel plains (several 100 km2), which are mainly covered by coarse gravel, sand, and desiccated grass. The gravel plains are highly homogeneous in space and time, which makes them ideal for validating a broad range of satellite-derived products. Dahra station is located in so called 'tiger bush' and is covered by strongly seasonal grass (95%) and sparse, evergreen trees (dominantly acacia trees) with a background of reddish sand. The strong seasonality is caused by a pronounced rainy season, during which LST retrieval is highly challenging. Outside the rainy season, both sites have relatively large fractions of bare ground and desiccated vegetation: therefore, they are particularly prone to be

  4. A novel in-situ measuring technique for aspheric surface

    Science.gov (United States)

    Zhang, Chuan; Wang, Ping; Chen, Yaolong

    2011-11-01

    In this paper, a novel in-situ surface measuring technique for optical elements with aspheric surface is presented. It is a contact type probe, and can be used for measuring ground surfaces. The theory of this technique develops from coordinate measuring machine (CMM), and the measurement accuracy of this technique is depended on the accuracy of computer numerical controlled (CNC). By installing a special equipment with high accuracy measuring head in main spindle of CNC machine, and moving the probe along the path which is described by a mathematical aspheric expression precisely, we could get relative errors of sag height of any position in this path. With this technique, the repeat positioning error caused by traditional off-line measurement will be avoided. The author also has finished a special software with VC++ 6.0. With this software, the form error of ground work piece could be corrected rapidly. This software can calculate and handle the arrangement automatically with all parameters which are required to input in operation interface. In the correction stage, the software can analyze and process error data and generate a new NC program with corrected data for next grinding stage. After 2 or 3 times measuring and correction, the surface shape error of the aspheric optical element will be less than 1μm. The finished work piece has a very good surface finish and can be polished with high quality.

  5. Nonspherical atomic effective pseudopotentials for surface passivation

    Science.gov (United States)

    Karpulevich, Anastasia; Bui, Hanh; Antonov, Denis; Han, Peng; Bester, Gabriel

    2016-11-01

    We present a method to extract accurate pseudopotentials for surface passivants, within the framework of the atomic effective pseudopotential method. We retain the imaginary part of the pseudopotential in the construction procedure. This imaginary component in reciprocal space translates into a nonspherical component in real space. This asphericity allows to model surface dipoles and their ensuing band offsets. We show that these surface effects need to be taken into account to model electronic properties of quantum dots accurately—which requires to go beyond the spherical potential approximation for the passivant/surface atoms. The good level of transferability, without additional computational costs, is demonstrated for Si, CdSe, and InP nanostructures. The results are directly compared to large-scale density functional theory calculations.

  6. Method for in-situ cleaning of carbon contaminated surfaces

    Science.gov (United States)

    Klebanoff, Leonard E.; Grunow, Philip; Graham, Jr., Samuel

    2006-12-12

    Activated gaseous species generated adjacent a carbon contaminated surface affords in-situ cleaning. A device for removing carbon contamination from a surface of the substrate includes (a) a housing defining a vacuum chamber in which the substrate is located; (b) a source of gaseous species; and (c) a source of electrons that are emitted to activate the gaseous species into activated gaseous species. The source of electrons preferably includes (i) a filament made of a material that generates thermionic electron emissions; (ii) a source of energy that is connected to the filament; and (iii) an electrode to which the emitted electrons are attracted. The device is particularly suited for photolithography systems with optic surfaces, e.g., mirrors, that are otherwise inaccessible unless the system is dismantled. A method of removing carbon contaminants from a substrate surface that is housed within a vacuum chamber is also disclosed. The method employs activated gaseous species that react with the carbon contaminants to form carbon containing gaseous byproducts.

  7. In situ measurement of PCB pore water concentration profiles in activated carbon-amended sediment using passive samplers.

    Science.gov (United States)

    Oen, Amy M P; Janssen, Elisabeth M L; Cornelissen, Gerard; Breedveld, Gijs D; Eek, Espen; Luthy, Richard G

    2011-05-01

    Vertical pore water profiles of in situ PCBs were determined in a contaminated mudflat in San Francisco Bay, CA, 30 months after treatment using an activated carbon amendment in the upper layer of the sediment. Pore water concentrations were derived from concentrations of PCBs measured in two passive samplers; polyethylene (PE, 51 μm thick) and polyoxymethylene (POM, 17 μm thick) at different sediment depths. To calculate pore water concentrations from PCB contents in the passive samplers, an equilibrium approach and a first-order uptake model were applied, using five performance reference compounds to estimate pore water sampling rates. Vertical pore water profiles showed good agreement among the measurement and calculation methods with variations within a factor of 2, which seems reasonable for in situ measurements. The close agreements of pore water estimates for the two sampler materials (PE and POM) and the two methods used to translate uptake in samplers to pore water concentrations demonstrate the robustness and suitability of the passive sampling approach. The application of passive samplers in the sediment presents a promising method for site monitoring and remedial treatment evaluation of sorbent amendment or capping techniques that result in changes of pore water concentrations in the sediment subsurface.

  8. Passive methods for quantifying the In Situ Flux of Water, Uranium, and Microbial Biomass

    Science.gov (United States)

    Newman, M. A.; Peacock, A.; Hatfield, K.; Stucker, V.; Cho, J.; Klammler, H.; Ranville, J. F.; Cabaniss, S.; Annable, M. D.; Perminova, I.

    2011-12-01

    The goal of this project was to develop a novel sensor that incorporates field-tested concepts of the passive flux meter (PFM) to provide direct in situ measures of uranium and groundwater fluxes. The sensor uses two sorbents and tracers to measure uranium flux and specific discharge directly-sensor principles and design will apply to fluxes of other radionuclides, metals, and co-contaminants. Flux measurements will assist in obtaining field-scale quantification of subsurface processes affecting uranium transport (e.g., advection) and transformation (e.g., uranium attenuation) and further advance conceptual and computational models for field scale simulations. Project efforts will expand our current understanding of how field-scale spatial variations in fluxes of uranium, groundwater and salient electron donor/acceptors are coupled to spatial variations in measured microbial biomass/community composition, effective field-scale uranium mass balances, attenuation, and stability. Field tests in the La Quinta and Super 8 galleries at the Rifle IFRC site were conducted to assess ambient groundwater, uranium, and microbial biomass fluxes. The latter were determined using a newly designed Baffled Multilevel Sampling (BMLS) device installed in typical screened monitoring wells to provide aqueous concentrations of dissolved or suspended constituents over multiple isolated vertical sections of the well. Biomass mass fluxes were calculated from the product of BMLS data for microbial cell counts from PCR analyses and PFM water fluxes collected from coincident well sections. Expected microbial discharge for Eubacteria in the La Quinta gallery was estimated to be 1.7 x 1012 cells per day. The biomass discharges for Geobacter, Methanogens, and Anaeromyxobacter remain to be determined. Expected uranium discharges predicted from stochastic simulations using PFM measures of flux over the La Quinta gallery transect and the injection-well transect of the Super 8 gallery were 26 mg

  9. Supercritical synthesis and in situ deposition of PbS nanocrystals with oleic acid passivation for quantum dot solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Tavakoli, M.M. [Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of); Simchi, A., E-mail: simchi@sharif.edu [Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of); Aashuri, H. [Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of)

    2015-04-15

    Colloidal quantum dot solar cells have recently attracted significant attention due to their low-processing cost and surging photovoltaic performance. In this paper, a novel, reproducible, and simple solution-based process based on supercritical fluid toluene is presented for in situ growth and deposition PbS nanocrystals with oleic-acid passivation. A lead precursor containing sulfur was mixed with oleic acid in toluene and processed in a supercritical fluid condition at different temperatures of 140, 270 and 330 °C for 20 min. The quantum dots were deposited on a fluorine-doped tin oxide glass substrate inside the supercritical reactor. Transmission electron microscopy, X-ray diffraction, absorption and dynamic light scattering showed that the nanocrystals processed at the supercritical condition (330 °C) are fully crystalline with a narrow size distribution of ∼3 nm with an absorption wavelength of 915 nm (bandgap of 1.3 eV). Fourier transform infrared spectroscopy indicated that the PbS quantum dots are passivated by oleic acid molecules during the growth. Photovoltaic characteristics of Schottky junction solar cells showed an improvement over devices prepared by spin-coating. - Highlights: • Supercritical fluid processing and in situ deposition of PbS QDs are presented. • The prepared nanocrystals are mono-dispersed with an optical bandgap of 1.3 eV. • Photovoltaic performance of the in situ deposited nanocrystals is reported. • An improved PV performance compared to spin coated Schottky solar cells is shown.

  10. 30 CFR 206.463 - In-situ and surface gasification and liquefaction operations.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false In-situ and surface gasification and... gasification and liquefaction operations. If an ad valorem Federal coal lease is developed by in-situ or surface gasification or liquefaction technology, the lessee shall propose the value of coal for royalty...

  11. 30 CFR 206.264 - In-situ and surface gasification and liquefaction operations.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false In-situ and surface gasification and... gasification and liquefaction operations. If an ad valorem Federal coal lease is developed by in-situ or surface gasification or liquefaction technology, the lessee shall propose the value of coal for royalty...

  12. Passive heating of the ground surface

    Science.gov (United States)

    Tyburczyk, Anna

    2016-03-01

    The phenomenon of phase change is one of the most important contemporary issues of thermal engineering. In particular, this applies to all kinds of heat exchanger systems, which should achieve the highest possible efficiency while reducing investment and operating costs. Some of these systems are heat pipes or thermosyphons, which, among others, are used for the heat transfer, temperature stabilization and the regulation of heat flux density. Additionally, they are passive systems, and therefore do not require an external power supply. Heat pipes can be used to stabilize the surface temperature of roads and driveways. Large heat tubes can be applied for heating the surface of bridges and overpasses, which become icy in unfavorable climatic conditions. The paper presents research on the test facility, whose main component is a long vertical copper fin. The temperature at the base of the fin was kept constant for a given series of measurements. Heat receiving fluid was ethanol at atmospheric pressure. The measurement methodology and the results of investigations were discussed. The surface temperature distribution was measured with the infrared camera, and on this basis the local values of heat flow and the heat transfer coefficient were determined. The results were presented as boiling curves for both the fin with the smooth surface and the one covered with a metal capillary-porous structure. The results obtained are useful in the design of heat exchangers, including passive heating of the ground.

  13. Passive heating of the ground surface

    Directory of Open Access Journals (Sweden)

    Tyburczyk Anna

    2016-01-01

    Full Text Available The phenomenon of phase change is one of the most important contemporary issues of thermal engineering. In particular, this applies to all kinds of heat exchanger systems, which should achieve the highest possible efficiency while reducing investment and operating costs. Some of these systems are heat pipes or thermosyphons, which, among others, are used for the heat transfer, temperature stabilization and the regulation of heat flux density. Additionally, they are passive systems, and therefore do not require an external power supply. Heat pipes can be used to stabilize the surface temperature of roads and driveways. Large heat tubes can be applied for heating the surface of bridges and overpasses, which become icy in unfavorable climatic conditions. The paper presents research on the test facility, whose main component is a long vertical copper fin. The temperature at the base of the fin was kept constant for a given series of measurements. Heat receiving fluid was ethanol at atmospheric pressure. The measurement methodology and the results of investigations were discussed. The surface temperature distribution was measured with the infrared camera, and on this basis the local values of heat flow and the heat transfer coefficient were determined. The results were presented as boiling curves for both the fin with the smooth surface and the one covered with a metal capillary-porous structure. The results obtained are useful in the design of heat exchangers, including passive heating of the ground.

  14. Polydimethylsiloxane Rods for the Passive Sampling of Pesticides in Surface Waters

    Directory of Open Access Journals (Sweden)

    Jérôme Randon

    2013-09-01

    Full Text Available In this work, the low cost synthesis of polydimethylsiloxane (PDMS rods is described, and the performances of this new passive sampling device (in laboratory and in situ are compared to the passive stir bar sorptive extraction (SBSE for the monitoring of pesticides from different classes (herbicides, insecticides and fungicides in surface waters. The influence of synthesis parameters of PDMS rods (i.e., heating temperature, heating time and relative amount of curing agent were assessed regarding their efficiency for the extraction of the target pesticides through a Hadamard’s experimental design. This allowed the determination of the effect of the three parameters on the sorption of pesticides within four experiments. Thus, specific conditions were selected for the synthesis of the PDMS rods (heating at 80 °C for 2 h with 10% of curing agent. Laboratory experiments led to similar to lower extraction recovery in the PDMS rods in comparison with passive SBSE, depending on the pesticide. The in situ application demonstrated the efficiency of the PDMS rods for the passive sampling of the target pesticides in river water, although lower amounts of pesticides were recovered in comparison with passive SBSE. So, these very low cost PDMS rods could be used as an alternative to passive SBSE for large-scale monitoring campaigns.

  15. A Low-Cost Energy-Efficient Cableless Geophone Unit for Passive Surface Wave Surveys

    Directory of Open Access Journals (Sweden)

    Kaoshan Dai

    2015-09-01

    Full Text Available The passive surface wave survey is a practical, non-invasive seismic exploration method that has increasingly been used in geotechnical engineering. However, in situ deployment of traditional wired geophones is labor intensive for a dense sensor array. Alternatively, stand-alone seismometers can be used, but they are bulky, heavy, and expensive because they are usually designed for long-term monitoring. To better facilitate field applications of the passive surface wave survey, a low-cost energy-efficient geophone system was developed in this study. The hardware design is presented in this paper. To validate the system’s functionality, both laboratory and field experiments were conducted. The unique feature of this newly-developed cableless geophone system allows for rapid field applications of the passive surface wave survey with dense array measurements.

  16. A Low-Cost Energy-Efficient Cableless Geophone Unit for Passive Surface Wave Surveys.

    Science.gov (United States)

    Dai, Kaoshan; Li, Xiaofeng; Lu, Chuan; You, Qingyu; Huang, Zhenhua; Wu, H Felix

    2015-09-25

    The passive surface wave survey is a practical, non-invasive seismic exploration method that has increasingly been used in geotechnical engineering. However, in situ deployment of traditional wired geophones is labor intensive for a dense sensor array. Alternatively, stand-alone seismometers can be used, but they are bulky, heavy, and expensive because they are usually designed for long-term monitoring. To better facilitate field applications of the passive surface wave survey, a low-cost energy-efficient geophone system was developed in this study. The hardware design is presented in this paper. To validate the system's functionality, both laboratory and field experiments were conducted. The unique feature of this newly-developed cableless geophone system allows for rapid field applications of the passive surface wave survey with dense array measurements.

  17. Perspectives for in situ Scanning Tunnel Microscopic Imaging of Proteins at HOPG surfaces

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Thuesen, Marianne Hallberg; Møller, Per

    1996-01-01

    potentials on in situ potentiostatic control and releases nm size HOPG scrap bits. These are clearly different in shape from the ex situ imaged molecular-size structures. Laccase could not, however, be imaged by in situ STM, most likely due to structural incompatibility between hydrophobic HOPG surface...

  18. In-situ optical emission spectroscopy diagnostic of plasma ignition impact on crystalline silicon passivation by a-Si:H films

    Science.gov (United States)

    Meddeb, Hosny; Bearda, Twan; Abdulraheem, Yaser; Dimassi, Wissem; Ezzaouia, Hatem; Gordon, Ivan; Szlufcik, Jozef; Poortmans, Jef

    2016-08-01

    The influence of the plasma ignition condition during PECVD deposition from a silane/hydrogen mixture on the amorphous silicon passivation of crystalline silicon surface is investigated. The changes in this process step mainly consist in varying the power density for very brief durations in between 1 s and 3 s. We find that the ignition phase contributes significantly in the film growth, especially in the a-Si:H/c-Si interface formation. In particular, the deposition rate increases with ignition power density. TEM cross-section inspection presents a rougher a-Si:H/c-Si interface with higher plasma power and thus, a tendency for nano-clusters formation caused by the crystalline nature of the substrate. In-situ plasma diagnostics reveal the gradual raise up of IHa*/ISiH* with the power density leading to worse SiH* abstraction to the surface. Whereas, time-resolved optical emission spectroscopy explains the possible recombination mechanism in the plasma due to higher-silane related reactive species (HSRS) formation via polymerization reactions. Our results point out that the ignition conditions with a rather low power for longer time give the best passivation, resulting an effective lifetime up to 9 ms.

  19. Nearly Monodispersion CoSm Alloy Nanoparticles Formed by an In-situ Rapid Cooling and Passivating Microfluidic Process

    Directory of Open Access Journals (Sweden)

    Henry Laurence

    2009-01-01

    Full Text Available Abstract An in siturapid cooling and passivating microfluidic processhas been developed for the synthesis of nearly monodispersed cobalt samarium nanoparticles (NPs with tunable crystal structures and surface properties. This process involves promoting the nucleation and growth of NPs at an elevated temperature and rapidly quenching the NP colloids in a solution containing a passivating reagent at a reduced temperature. We have shown that Cobalt samarium NPs having amorphous crystal structures and a thin passivating layer can be synthesized with uniform nonspherical shapes and size of about 4.8 nm. The amorphous CoSm NPs in our study have blocking temperature near 40 K and average coercivity of 225 Oe at 10 K. The NPs also exhibit high anisotropic magnetic properties with a wasp-waist hysteresis loop and a bias shift of coercivity due to the shape anisotropy and the exchange coupling between the core and the thin oxidized surface layer.

  20. Evaluation of MODIS Land Surface Temperature with In Situ Snow Surface Temperature from CREST-SAFE

    Science.gov (United States)

    Perez Diaz, C. L.; Lakhankar, T.; Romanov, P.; Munoz, J.; Khanbilvardi, R.; Yu, Y.

    2016-12-01

    This paper presents the procedure and results of a temperature-based validation approach for the Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) product provided by the National Aeronautics and Space Administration (NASA) Terra and Aqua Earth Observing System satellites using in situ LST observations recorded at the Cooperative Remote Sensing Science and Technology Center - Snow Analysis and Field Experiment (CREST-SAFE) during the years of 2013 (January-April) and 2014 (February-April). A total of 314 day and night clear-sky thermal images, acquired by the Terra and Aqua satellites, were processed and compared to ground-truth data from CREST-SAFE with a frequency of one measurement every 3 min. Additionally, this investigation incorporated supplementary analyses using meteorological CREST-SAFE in situ variables (i.e. wind speed, cloud cover, incoming solar radiation) to study their effects on in situ snow surface temperature (T-skin) and T-air. Furthermore, a single pixel (1km2) and several spatially averaged pixels were used for satellite LST validation by increasing the MODIS window size to 5x5, 9x9, and 25x25 windows for comparison. Several trends in the MODIS LST data were observed, including the underestimation of daytime values and nighttime values. Results indicate that, although all the data sets (Terra and Aqua, diurnal and nocturnal) showed high correlation with ground measurements, day values yielded slightly higher accuracy ( 1°C), both suggesting that MODIS LST retrievals are reliable for similar land cover classes and atmospheric conditions. Results from the CREST-SAFE in situ variables' analyses indicate that T-air is commonly higher than T-skin, and that a lack of cloud cover results in: lower T-skin and higher T-air minus T-skin difference (T-diff). Additionally, the study revealed that T-diff is inversely proportional to cloud cover, wind speed, and incoming solar radiation. Increasing the MODIS window size

  1. In-Situ VIS/NIR Measurements of Space Environment Effects on Spacecraft Surfaces

    Science.gov (United States)

    Bedard, D.; Seitzer, P.; Willison, A.; Somers, P.

    2016-09-01

    Laboratory material characterization experiments have shown that passive observational techniques that measure the spectral energy distribution of reflected sunlight from spacecraft and space debris could potentially be used to determine an object's surface compositional make-up and even possibly its orientation. Such techniques, if proven to be reliable and consistent, would represent non-intrusive and cost effective tools that would benefit the overall space situational awareness (SSA) mission. However, to date, observations using either colour photometry or spectrophotometry to determine surface material characteristics of such objects have not produced encouraging results. One common problem that has plagued these attempts is the lack of understanding on how the spectral reflectance of the spacecraft surfaces evolves with time. There are a number of spacecraft materials whose spectral reflectance characteristics have been studied before and after spaceflight in LEO; there are no measurements on how the space environment gradually modifies the spectral scattering characteristics of these materials as a function of time. Furthermore, there are little or no in-situ observations of environmental effects on individually identifiable materials in MEO and GEO. This complicates the task of interpreting the spectral measurements of spatially unresolved spacecraft and orbital debris. This paper presents instrument concepts whose sole purpose will be to acquire on-orbit spectral reflectance measurements, at different observational geometries, of either witness samples or materials covering the surface of the host spacecraft. Such instruments could be flown as a hosted payload on an operational GEO satellite or as a dedicated payload on a microsatellite. Measurements would be acquired over the lifetime of the satellite and would observe how the spectral reflectance characteristics evolve during its lifetime. Furthermore, installation of one of the proposed instruments on

  2. In situ mineralogical-chemical analysis of Martian materials at landing/roving sites by active and passive remote sensing methods

    Science.gov (United States)

    Neukum, G.; Lehmann, F.; Regner, P.; Jaumann, R.

    1988-01-01

    Remote sensing of the Martian surface from the ground and from orbiting spacecraft has provided some first-order insight into the mineralogical-chemical composition and the weathering state of Martian surface materials. Much more detailed information can be gathered from performing such measurements in situ at the landing sites or from a rover in combination with analogous measurements from orbit. Measurements in the wavelength range of approximately 0.3 to 12.0 micrometers appear to be suitable to characterize much of the physical, mineralogical, petrological, and chemical properties of Martian surface materials and the weathering and other alteration processes that have acted on them. It is of particular importance to carry out measurements at the same time over a broad wavelength range since the reflectance signatures are caused by different effects and hence give different and complementing information. It appears particularly useful to employ a combination of active and passive methods because the use of active laser spectroscopy allows the obtaining of specific information on thermal infrared reflectance of surface materials. It seems to be evident that a spectrometric survey of Martian materials has to be focused on the analysis of altered and fresh mafic materials and rocks, water-bearing silicates, and possibly carbonates.

  3. In situ photoelectron spectroscopy of molecular-beam-epitaxy grown surfaces

    CERN Document Server

    Oshima, M; Okabayashi, J; Ono, K

    2003-01-01

    Two in situ high-resolution synchrotron radiation photoelectron spectroscopy (SRPES) systems combined with a molecular beam epitaxy (MBE) chamber for III-V compound semiconductors and a laser MBE chamber for strongly correlated oxide films, respectively, have been designed and fabricated to analyze intrinsic and surface/interface electronic structures of these unique materials. The importance of the in situ SRPES has been demonstrated by the results of 1) Si surface nanostructures, 2) GaAs surfaces/interfaces and nanostructures, 3) MnAs magnetic nanostructures, and 4) strongly-correlated La sub 1 sub - sub x Sr sub x MnO sub 3 surfaces/interfaces and superstructures.

  4. Organic carbon amendments for passive in situ treatment of mine drainage: Field experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lindsay, Matthew B.J., E-mail: mbjlindsay@uwaterloo.ca [Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Blowes, David W.; Condon, Peter D.; Ptacek, Carol J. [Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)

    2011-07-15

    Highlights: > Organic carbon amendments can support passive treatment of mine drainage. > Decreased transport of sulfide-oxidation products under sulfate-reducing conditions. > Treatment effectiveness dependent on organic carbon source and amendment rate. - Abstract: A field-scale experiment was conducted to evaluate various organic C sources as amendments for passive treatment of tailings pore water. Varied mixtures of peat, spent-brewing grain (SBG) and municipal biosolids (MB) were assessed for the potential to promote dissimilatory sulfate reduction (DSR) and metal-sulfide precipitation. Five amended cells and one control were constructed in the vadose zone of a sulfide- and carbonate-rich tailings deposit, and the geochemistry, microbiology and mineralogy were monitored for 4 a. Increases in pore-water concentrations of dissolved organic C (DOC) and decreases in aqueous SO{sub 4} concentrations of >2500 mg L{sup -1} were observed in cells amended with peat + SBG and peat + SBG + MB. Removal of SO{sub 4} was accompanied by shifts in {delta}{sup 34}S-SO{sub 4} values of >+30 per mille, undersaturation of pore water with respect to gypsum [CaSO{sub 4}.2H{sub 2}O], and increased populations of SO{sub 4}-reducing bacteria (SRB). Decreases in aqueous concentrations of Zn, Mn, Ni, Sb and Tl were observed for these cells relative to the control. Organic C introduction also supported growth of Fe-reducing bacteria (IRB) and increases in Fe and As concentrations. Enhanced Fe and As mobility occurred in all cells; however, maximum concentrations were observed in cells amended with MB. Subsequent decreases in Fe and As concentrations were attributed to DSR and metal-sulfide precipitation. The common presence of secondary Zn-S and Fe-S phases was observed by field emission-scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDS) spectroscopy. Selective extractions indicated that large decreases in water-soluble SO{sub 4} occurred in cells that supported DSR

  5. Online, In-Situ Monitoring Combustion Turbines Using Wireless Passive Ceramic Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Xun; An, Linan; Xu, Chengying

    2013-06-30

    The overall objective of this project is to develop high-temperature wireless passive ceramic sensors for online, real-time monitoring combustion turbines. During this project period, we have successfully demonstrated temperature sensors up to 1300{degrees}C and pressure sensors up to 800oC. The temperature sensor is based on a high-Q-factor dielectric resonator and the pressure sensor utilizes the evanescent-mode cavity to realize a pressure-sensitive high-Q-factor resonator. Both sensors are efficiently integrated with a compact antenna. These sensors are wirelessly interrogated. The resonant frequency change corresponding to either temperature or pressure can be identified using a time-domain gating technique. The sensors realized in this project can survive harsh environments characterized by high temperatures (>1000{degrees}C) and corrosive gases, owing to the excellent material properties of polymer-derived ceramics (PDCs) developed at University of Central Florida. It is anticipated that this work will significantly advance the capability of high-temperature sensor technologies and be of a great benefit to turbine industry and their customers.

  6. In-situ surface hardening of cast iron by surface layer metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Sebastian F., E-mail: s.fischer@gi.rwth-aachen.de [Foundry Institute, RWTH Aachen University, Intzestraße 5, 52072 Aachen (Germany); Muschna, Stefan, E-mail: smuschna@yahoo.de [Foundry Institute, RWTH Aachen University, Intzestraße 5, 52072 Aachen (Germany); Bührig-Polaczek, Andreas, E-mail: sekretariat@gi.rwth-aachen.de [Foundry Institute, RWTH Aachen University, Intzestraße 5, 52072 Aachen (Germany); Bünck, Matthias, E-mail: m.buenck@access-techcenter.de [Access e.V., Intzestraße 5, 52072 Aachen (Germany)

    2014-10-06

    Abrasive wear is a serious problem in many cast iron castings used in industry. To minimize failure and repair of these components, different strategies exist to improve their surface microhardness thus enhancing their wear resistance. However, most of these methods lead to very brittle and/or expensive castings. In the current work a new method for surface hardening is presented which utilizes surface layer metallurgy to generate in-situ a boron-enriched white cast iron surface layer with a high microhardness on a gray cast iron casting. To do this, sand molds are coated with a ferroboron suspension and cast with a cast iron melt. After solidification, a 100–900 µm thick layer of boron-enriched ledeburite is formed on the surface of the casting which produces an increase in the average microhardness from 284 HV{sub 0.1}±52 HV{sub 0.1} to 505 HV{sub 0.1}±87 HV{sub 0.1}. Analyses of the samples' core reveal a typical cast iron microstructure which leads to the conclusion that the coating mainly affects the castings' surface. By varying the grain size of the ferroboron powder in the coatings, it is shown that a powder size ≤100 µm is most suitable to create a boron-enriched ledeburite surface layer possessing high hardness values.

  7. Using electrochemical surface plasmon resonance for in-situ kinetic investigations of solid electrolyte interphase formation in lithium ion battery

    Science.gov (United States)

    Pradanawati, Sylvia Ayu; Wang, Fu-Ming; Su, Chia-Hung

    2016-10-01

    The solid electrolyte interphase (SEI) significantly affects the energy density and safety performance of lithium ion batteries. Previous studies have shown that conventional analyses cannot characterize the real-time molecule interactions of SEI formation on the surface of an electrode. In this study, a novel in situ electrochemical-surface plasmon resonance (EC-SPR) was developed for evaluating the kinetic changes of ionic dissociation, SEI formation, and Li-Au alloying reaction. The novel EC-SPR not only indicates the rates of each reaction stage but also reveals the characteristics of the passivated layers. This research demonstrates that the dissociation rates of ionic clusters are affected by several reactions on the surface of an electrode. The rate and mass of the SEI formation from the reduction of ethylene carbonate (EC) are calculated at 0.004 ngs-1 and 5.858 ng, respectively. The EC-SPR is a powerful tool for further in situ kinetic investigations of different electrolyte and electrode systems.

  8. In-Situ Extended Lateral Range Surface Metrology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop an extended lateral range capability for a dynamic optical profiling system to enable non-contact, surface roughness measurement of large and...

  9. Development and Validation of a SPME-GC-MS Method for In situ Passive Sampling of Root Volatiles from Glasshouse-Grown Broccoli Plants Undergoing Below-Ground Herbivory by Larvae of Cabbage Root Fly, Delia radicum L.

    Science.gov (United States)

    Deasy, William; Shepherd, Tom; Alexander, Colin J; Birch, A Nicholas E; Evans, K Andrew

    2016-11-01

    Research on plant root chemical ecology has benefited greatly from recent developments in analytical chemistry. Numerous reports document techniques for sampling root volatiles, although only a limited number describe in situ collection. To demonstrate a new method for non-invasive in situ passive sampling using solid phase micro extraction (SPME), from the immediate vicinity of growing roots. SPME fibres inserted into polyfluorotetrafluoroethylene (PTFE) sampling tubes located in situ which were either perforated, covered with stainless steel mesh or with microporous PTFE tubing, were used for non-invasive sub-surface sampling of root volatiles from glasshouse-grown broccoli. Sampling methods were compared with above surface headspace collection using Tenax TA. The roots were either mechanically damaged or infested with Delia radicum larvae. Principal component analysis (PCA) was used to investigate the effect of damage on the composition of volatiles released by broccoli roots. Analyses by gas chromatography-mass spectrometry (GC-MS) with SPME and automated thermal desorption (ATD) confirmed that sulphur compounds, showing characteristic temporal emission patterns, were the principal volatiles released by roots following insect larval damage. Use of SPME with in situ perforated PTFE sampling tubes was the most robust method for out-of-lab sampling. This study describes a new method for non-invasive passive sampling of volatiles in situ from intact and insect damaged roots using SPME. The method is highly suitable for remote sampling and has potential for wide application in chemical ecology/root/soil research. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  10. Multi-Temporal Evaluation of Soil Moisture and Land Surface Temperature Dynamics Using in Situ and Satellite Observations

    Directory of Open Access Journals (Sweden)

    Miriam Pablos

    2016-07-01

    Full Text Available Soil moisture (SM is an important component of the Earth’s surface water balance and by extension the energy balance, regulating the land surface temperature (LST and evapotranspiration (ET. Nowadays, there are two missions dedicated to monitoring the Earth’s surface SM using L-band radiometers: ESA’s Soil Moisture and Ocean Salinity (SMOS and NASA’s Soil Moisture Active Passive (SMAP. LST is remotely sensed using thermal infrared (TIR sensors on-board satellites, such as NASA’s Terra/Aqua MODIS or ESA & EUMETSAT’s MSG SEVIRI. This study provides an assessment of SM and LST dynamics at daily and seasonal scales, using 4 years (2011–2014 of in situ and satellite observations over the central part of the river Duero basin in Spain. Specifically, the agreement of instantaneous SM with a variety of LST-derived parameters is analyzed to better understand the fundamental link of the SM–LST relationship through ET and thermal inertia. Ground-based SM and LST measurements from the REMEDHUS network are compared to SMOS SM and MODIS LST spaceborne observations. ET is obtained from the HidroMORE regional hydrological model. At the daily scale, a strong anticorrelation is observed between in situ SM and maximum LST (R ≈ − 0.6 to −0.8, and between SMOS SM and MODIS LST Terra/Aqua day (R ≈ − 0.7. At the seasonal scale, results show a stronger anticorrelation in autumn, spring and summer (in situ R ≈ − 0.5 to −0.7; satellite R ≈ − 0.4 to −0.7 indicating SM–LST coupling, than in winter (in situ R ≈ +0.3; satellite R ≈ − 0.3 indicating SM–LST decoupling. These different behaviors evidence changes from water-limited to energy-limited moisture flux across seasons, which are confirmed by the observed ET evolution. In water-limited periods, SM is extracted from the soil through ET until critical SM is reached. A method to estimate the soil critical SM is proposed. For REMEDHUS, the critical SM is estimated to be ∼0

  11. In situ scanning FTIR microscopy and IR imaging of Pt electrode surface towards CO adsorption

    Institute of Scientific and Technical Information of China (English)

    孙世刚; 洪双进; 陈声培; 卢国强; 戴鸿平; 肖晓银

    1999-01-01

    In situ scanning FTIR microscopy was built up for the first time in the present work, which consists of an FTIR apparatus, an IR microscope, an X-Y mapping stage, and the specially designed electrochemical IR cell and computer software. It has been demonstrated that this new space-resolvd in situ IR technique can be used to study vibration properties of micro-area, and to perform IR imaging of electrode surface. The chemical image obtained using this technique fur CO adsorption on Pt electrode illustrated, at a space-resolution of 10-2 cm, the inhomogeneity and the distribution of reactivity of micro-area of electrode surface.

  12. In situ ion gun cleaning of surface adsorbates and its effect on electrostatic forces

    Science.gov (United States)

    Schafer, Robert; Xu, Jun; Mohideen, Umar

    2016-01-01

    To obtain precise measurements of the Casimir force, it is crucial to take into account the electrostatic interactions that exist between the two boundaries. Two otherwise grounded conductors will continue to have residual electrostatic effects from patch potentials existing on the surfaces. In this paper, we look at the effect of in situ cleaning of adsorbate patches, and the resultant effect on the net electrostatic potential difference between two surfaces. We find a significant reduction in the residual potential due to in situ Ar+ cleaning for the samples used.

  13. Investigation and Application of a New Passive Sampling Technique for in Situ Monitoring of Illicit Drugs in Waste Waters and Rivers.

    Science.gov (United States)

    Guo, Changsheng; Zhang, Tingting; Hou, Song; Lv, Jiapei; Zhang, Yuan; Wu, Fengchang; Hua, Zhendong; Meng, Wei; Zhang, Hao; Xu, Jian

    2017-08-15

    Illicit drugs constitute a class of emerging contaminants that has been drawing significant concern due to its potent pharmacological and biological activities. In this study, an in situ passive sampling approach that uses diffusive gradients in thin films (DGT) was successfully tested for measuring ketamine (KET), methamphetamine (METH), and amphetamine (AMP) in water. The diffusion coefficients of KET, METH, and AMP in diffusive gel were (8.13 ± 0.12) × 10(-6), (8.55 ± 0.14) × 10(-6), and (7.72 ± 0.18) × 10(-6) cm(2) s(-1) at 22 °C, respectively. The capacities of an XAD binding gel for KET, METH, and AMP were 92, 57, and 45 μg per binding gel disc, which were suitable for long-term environmental monitoring. The DGT measurement of these drugs was not influenced by the pH (4 to 9) and the ionic strength (0.001 M - 0.1 M) and unaffected by the water flow, demonstrating the effectiveness of the XAD-based DGT for the in situ monitoring of illicit drugs. DGT samplers were deployed in a WWTP influent and natural rivers in Beijing, China. The ng L(-1) levels of the drugs were high in the wastewater influent and low in river waters, with an insignificant fluctuation during the seven-day monitoring. The DGT-measured concentrations were comparable to the average concentrations determined by SPE method, which suggested that the average data measured by DGT could be substituted for high-frequency grab sampling. This study has demonstrated systematically for the first time that DGT is effective and accurate for monitoring illicit drugs in wastewater and surface waters, and provides a powerful tool to investigating the presence, transport, and environmental behaviors of these drugs in the aquatic ecosystem.

  14. Optimized in situ construction of oligomers on an array surface

    Science.gov (United States)

    Tolonen, Andrew C.; Albeanu, Dinu F.; Corbett, Julia F.; Handley, Heather; Henson, Charlotte; Malik, Pratap

    2002-01-01

    Oligonucleotide arrays are powerful tools to study changes in gene expression for whole genomes. These arrays can be synthesized by adapting photolithographic techniques used in microelectronics. Using this method, oligonucleotides are built base by base directly on the array surface by numerous cycles of photodeprotection and nucleotide addition. In this paper we examine strategies to reduce the number of synthesis cycles required to construct oligonucleotide arrays. By computer modeling oligonucleotide synthesis, we found that the number of required synthesis cycles could be significantly reduced by focusing upon how oligonucleotides are chosen from within genes and upon the order in which nucleotides are deposited on the array. The methods described here could provide a more efficient strategy to produce oligonucleotide arrays. PMID:12384609

  15. Moessbauer In Situ Studies of the Surface of Mars

    Energy Technology Data Exchange (ETDEWEB)

    Klingelhoefer, G., E-mail: klingel@mail.uni-mainz.de [Johannes Gutenberg Universitaet, Inst. Anorganische and Analytische Chemie (Germany)

    2004-11-15

    For the first time in history, a Moessbauer spectrometer was placed on the surface of another planet. Our miniaturized Moessbauer spectrometer MIMOS II is part of the instrument payload of NASA's twin Mars Exploration Rovers (MER) 'Spirit' and 'Opportunity', which in January 2004 successfully landed at the Gusev crater and the Meridiani Planum landing sites, respectively. MIMOS II determines the Fe-bearing mineralogy of Martian soils and rocks at the Rovers' respective landing sites. The main goals of this planetary twin mission are to: (1) identify hydrologic, hydrothermal, and other processes that have operated and affected materials at the landing sites; (2) identify and investigate the rocks and soils at both landing sites, as there is a possible chance that they may preserve evidence of ancient environmental conditions and possible prebiotic or biotic activities. With MIMOS II, besides other minerals the Fe silicate olivine has been identified in both soil and rocks at both landing sites. At the Meridiani site the Fe sulfate jarosite has been identified by MIMOS II which is definitive mineralogical proof of the presence of water at this site in the past.

  16. Design and development of in situ albumin binding surfaces: Evaluation in the paradigm of blood-biomaterial compatibility

    Science.gov (United States)

    Guha Thakurta, Sanjukta

    Biocompatibility of natural and synthetic implant materials as blood contacting devices is crucial to host response. Implantation often raises complications from thrombotic and thromboembolic events. The aspect of hemocompatibility concentrates on minimizing thrombotic and thromboembolic response of foreign materials in contact with blood. The initial layer of surface adsorbed proteins plays a pivotal role in the adhesion and subsequent aggregation of platelets and in the activation of the coagulation cascade. Therefore, an improved surface architecture is required to gain control over the initial protein adsorption events, thereby extending the sustainability of an implantable device. In general, surfaces with an ability to bind endogenous albumin has been known to minimize platelet adhesion and activation. While the scope of applicability is broad, in this study silicon-based surfaces were selected as model surfaces. A densely packed uniformly distributed silane monolayer was achieved on silicon based surfaces with -- NH2 functionality, upon a careful optimization of hydroxylation and the subsequent silanization with 2 vol% of 3-Aminopropyltriethoxy Silane (APTES). Two linear peptides with affinity for albumin over other serum proteins were selected to create affinity surfaces. Silanized surfaces covalently immobilized with albumin binding peptides were evaluated in the paradigm of blood-biomaterial compatibility. When compared to control surfaces, albumin binding surfaces prepared in this study: (a) possessed 2.0 to 3.0 mug/cm2 of surface bound albumin with minimal surface adsorbed fibrinogen, (b) depicted low levels of adhered platelets and supported a rounded platelet morphology, (c) displayed delayed clotting, (d) showed reduced platelet adhesion and activation under shearing, and (f) exhibited faster adsorption kinetics. Conclusively, in-situ albumin binding surfaces selectively and specifically interacted with albumin without being severely displaced by

  17. Arctic surface temperatures from Metop AVHRR compared to in situ ocean and land data

    Directory of Open Access Journals (Sweden)

    G. Dybkjær

    2012-11-01

    Full Text Available The ice surface temperature (IST is an important boundary condition for both atmospheric and ocean and sea ice models and for coupled systems. An operational ice surface temperature product using satellite Metop AVHRR infra-red data was developed for MyOcean. The IST can be mapped in clear sky regions using a split window algorithm specially tuned for sea ice. Clear sky conditions prevail during spring in the Arctic, while persistent cloud cover limits data coverage during summer. The cloud covered regions are detected using the EUMETSAT cloud mask. The Metop IST compares to 2 m temperature at the Greenland ice cap Summit within STD error of 3.14 °C and to Arctic drifting buoy temperature data within STD error of 3.69 °C. A case study reveals that the in situ radiometer data versus satellite IST STD error can be much lower (0.73 °C and that the different in situ measurements complicate the validation. Differences and variability between Metop IST and in situ data are analysed and discussed. An inter-comparison of Metop IST, numerical weather prediction temperatures and in situ observation indicates large biases between the different quantities. Because of the scarcity of conventional surface temperature or surface air temperature data in the Arctic, the satellite IST data with its relatively good coverage can potentially add valuable information to model analysis for the Arctic atmosphere.

  18. In-situ generation of chlorine dioxide for surface decontamination of produce

    Science.gov (United States)

    Fruits and vegetables, particularly fresh-cut products, are frequently contaminated with bacterial pathogens and implicated in foodborne illnesses. The objective of this study was to develop a unique in-situ sequential surface decontamination method for produce using sodium chlorite and acid. The ...

  19. Arctic surface temperatures from Metop AVHRR compared to in situ ocean and land data

    Directory of Open Access Journals (Sweden)

    G. Dybkjær

    2012-03-01

    Full Text Available The ice surface temperature (IST is an important boundary condition for both atmospheric and ocean and sea ice models and for coupled systems. An operational ice surface temperature product using satellite Metop AVHRR infra-red data was developed for MyOcean. The IST can be mapped in clear sky regions using a split window algorithm specially tuned for sea ice. Clear sky conditions are prevailing during spring in the Arctic while persistent cloud cover limits data coverage during summer. The cloud covered regions are detected using the EUMETSAT cloud mask. The Metop IST compares to 2 m temperature at the Greenland ice cap Summit within STD error of 3.14 °C and to Arctic drifting buoy temperature data within STD error of 3.69 °C. A case study reveal that the in situ radiometer data versus satellite IST STD error can be much lower (0.73 °C and that the different in situ measures complicates the validation. Differences and variability between Metop IST and in situ data are analysed and discussed. An inter-comparison of Metop IST, numerical weather prediction temperatures and in situ observation indicates large biases between the different quantities. Because of the scarcity of conventional surface temperature or surface air temperature data in the Arctic the satellite IST data with its relatively good coverage can potentially add valuable information to model analysis for the Arctic atmosphere.

  20. Contact nucleation. In situ and ex situ observations of surface damaging

    NARCIS (Netherlands)

    van der Heijden, A.E.D.M.; Elwenspoek, Michael Curt

    To investigate the damaging done to a crystal surface potassium dihydrogen phosphate, KDP and potassium hydrogen phthalate, KAP) due to a crystal-rod contact, both ex situ and in situ experiments were performed and the impact sites studied either using an interference contrast microscope or a

  1. Solid oxide electrode kinetics in light of in situ surface studies

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg

    2014-01-01

    The combination of in situ and in particular in operando characterization methods such as electrochemical impedance spectroscopy (EIS) on both technical and model electrode are well known ways to gain some practical insight in electrode reaction kinetics. Yet, is has become clear that in spite...... couple of decades, but recent in situ - or even better - in operando surface measurements such as high temperature scanning probe measurements and Raman spectroscopy have proven very valuable in obtaining new data that can support the interpretation of EIS and current – voltage (i-V) measurements...

  2. Development of a Surface Acoustic Wave Sensor for In-Situ Monitoring of Volatile Organic Compounds

    Directory of Open Access Journals (Sweden)

    Jerome L. Wright

    2003-07-01

    Full Text Available This paper describes the development of a surface-acoustic-wave (SAW sensor that is designed to be operated continuously and in situ to detect volatile organic compounds. A ruggedized stainless-steel package that encases the SAW device and integrated circuit board allows the sensor to be deployed in a variety of media including air, soil, and even water. Polymers were optimized and chosen based on their response to chlorinated aliphatic hydrocarbons (e.g., trichloroethylene, which are common groundwater contaminants. Initial testing indicates that a running-average data-logging algorithm can reduce the noise and increase the sensitivity of the in-situ sensor.

  3. In-situ calibration of POCIS for the sampling of polar pesticides and metabolites in surface water.

    Science.gov (United States)

    Ibrahim, Imtiaz; Togola, Anne; Gonzalez, Catherine

    2013-11-15

    Over the past years, passive sampling devices have been successfully used for the monitoring of various pollutants in water. The present work studied the uptake kinetics in surface water of ten polar pesticides and metabolites, using pharmaceutical POCIS samplers. The aim was to determine sampling rates from in-situ calibration and to compare results with those obtained earlier under laboratory conditions, with the final objective of assessing the impact of environmental conditions on POCIS field performance. Field results showed a low efficiency of POCIS uptake capacity for moderately polar compounds, such as propiconazole (log Kow=3.72) and tebuconazole (log Kow=3.7), that were present in the aqueous phase at very low levels. The in-situ sampling rates obtained in this study ranged from 169 to 479 mL g(-1)day(-1) and differ by a factor of 3-7.5 from Rs determined under laboratory conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. PDS Lunar Data Node Restoration of Apollo In-Situ Surface Data

    Science.gov (United States)

    Williams, David R.; Hills, H. Kent; Guinness, Edward A.; Lowman, Paul D.; Taylor, Patrick T.

    2010-01-01

    The Apollo missions between 1969 and 1972 deployed scientific instruments on the Moon's surface which made in-situ measurements of the lunar environment. Apollo II had the short-term Early Apollo Surface Experiments Package (EASEP) and Apollos 12, 14, 15, 16, and 17 each set up an Apollo Lunar Surface Experiments Package (ALSEP). Each ALSEP package contained a different suite of instruments which took measurements and radioed the results back to Earth over periods from 5 to 7 years until they were turned off on 30 September 1977. To this day the ALSEP data remain the only long-term in-situ information on the Moon's surface environment. The Lunar Data Node (LDN) has been formed under the auspices of the Planetary Data System (PDS) Geosciences Node to put relevant, scientifically important Apollo data into accessible digital form for use by researchers and mission planners. We will report on progress made since last year and plans for future data restorations.

  5. A model-based framework for the quality assessment of surface albedo in situ measurement protocols

    Science.gov (United States)

    Adams, Jennifer; Gobron, Nadine; Widlowski, Jean-Luc; Mio, Corrado

    2016-09-01

    Satellite-based retrievals of land surface albedo are essential for climate and environmental modelling communities. To be of use, satellite-retrievals are required to comply to given accuracy requirements, mainly achieved through comparison with in situ measurements. Differences between in situ and satellite-based retrievals depend on their actual difference and their associated uncertainties. It is essential that these uncertainties can be computed to properly understand the differences between satellite-based and in situ measurements of albedo, however quantifying the individual contributions of uncertainty is difficult. This study introduces a model-based framework for assessing the quality of in situ albedo measurements. A 3D Monte Carlo Ray Tracing (MCRT) radiative transfer model is used to simulate field measurements of surface albedo, and is able to identify and quantify potential sources of error in the field measurement. Compliance with the World Meteorological Organisation (WMO) requirement for 3% accuracy is tested. 8 scenarios were investigated, covering a range of ecosystem types and canopy structures, seasons, illumination angles and tree heights. Results indicate that height of measurement above the canopy is the controlling factor in accuracy, with each canopy scenario reaching the WMO requirement at different heights. Increasing canopy heterogeneity and tree height noticeably reduces the accuracy, whereas changing seasonality from summer to winter in a deciduous forest increases accuracy. For canopies with a row structure, illumination angle can significantly impact accuracy as a result of shadowing effects. Tests were made on the potential use of multiple in situ measurements, indicating considerably increased accuracy if two or more in situ measurements can be made.

  6. Reducing roll motion by passive free surface tanks

    DEFF Research Database (Denmark)

    Nielsen, Ulrik Dam; Nielsen, Christian S.

    2014-01-01

    Roll stabilisation of motorised vessels plays an important part in reducing passenger discomfort and increasing safety and cargo capacity. Passive free surface tanks are considered a low-cost stabilising method, which is efficient at all speeds without increasing hull resistance. In this study......, a mathematical model for evaluating the performance of a passive free surface tank is established. This is done by coupling a roll model to a fluid flow model. As a numerical example, the seakeeping abilities of a container vessel are evaluated. The necessary methods for performing the simulation are presented...... and the design of a free surface tank is explained. The effects of the passive free surface tank are evaluated and a significant damping effect is observed, particularly in cases with resonant roll....

  7. An in situ study of amine and amide molecular interaction on Fe surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, P. [Materials innovation institute (M2i), Mekelweg 2, 2628 CD Delft (Netherlands); Delft University of Technology, Department of Materials Science and Engineering, Mekelweg 2, 2628 CD Delft (Netherlands); Terryn, H. [Delft University of Technology, Department of Materials Science and Engineering, Mekelweg 2, 2628 CD Delft (Netherlands); Vrije Universiteit Brussel, Department of Electrochemical and Surface Engineering, Pleinlaan 2, B-1050 Brussels (Belgium); Mol, J.M.C., E-mail: J.M.C.Mol@tudelft.nl [Delft University of Technology, Department of Materials Science and Engineering, Mekelweg 2, 2628 CD Delft (Netherlands)

    2015-11-01

    Highlights: • We investigated the interaction of amine and amide molecules on iron substrates. • In situ FTIR and electrochemical measurements are conducted. • Chemisorption takes place between the molecules and Fe surfaces. • Applied external potential influences adsorption properties. • Molecular functional groups influence adsorption properties. - Abstract: The interfacial bondings formed between N,N′-diethylmethylamine, N-methyldiethanolamine and N,N′-dimethylsuccinamide molecules with iron surfaces have been investigated using Fourier transform infrared spectroscopy (FTIR) and electrochemical spectroscopies. In this case, the interfacial interactions have been evaluated by analyzing ex situ FTIR peaks and probing potential variations upon molecular interactions to Fe surfaces. Moreover, integrated ATR-FTIR and chronovoltammetry analyses in Kretschmann geometry have been employed to probe the interactions between the molecules and Fe surfaces in situ. The results revealed that a charge transfer between molecules and Fe surfaces takes place indicating chemisorption of the molecules on Fe surfaces. In this case, the interaction of N,N′-diethylmethylamine and Fe surface is negligible. However, N-methyldiethanolamine molecules interact with Fe surfaces through the nitrogen atoms. Interaction of N,N′-dimethylsuccinamide molecules and Fe surface is promoted by nitrogen and carbonyl functional groups. Moreover, interactions of N-methyldiethanolamine and N,N′-dimethylsuccinamide molecules to Fe surfaces are encouraged by application of anodic potentials implying that the molecules and Fe surfaces are charged positively and negatively, respectively.

  8. Synthesis in situ of gold nanoparticles by a dialkynyl Fischer carbene complex anchored to glass surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bertolino, María Candelaria, E-mail: cbertolino@fcq.unc.edu.ar; Granados, Alejandro Manuel, E-mail: ale@fcq.unc.edu.ar

    2016-10-15

    Highlights: • Fischer carbene 1-W reacts via cycloaddition without Cu(I) with azide terminal surface. • This reaction on the surface is regioselective to internal triple bond of 1-W. • 1-W bound to glass surface produce AuNps in situ fixed to the surface. • This ability is independent of how 1-W is bonded to the surface. • This hybrid surface can be valuable as SERS substrate or in heterogeneous catalysis. - Abstract: In this work we present a detailed study of classic reactions such as “click reaction” and nucleophilic substitution reaction but on glass solid surface (slides). We used different reactive center of a dialkynylalcoxy Fischer carbene complex of tungsten(0) to be anchored to modified glass surface with amine, to obtain aminocarbene, and azide terminal groups. These cycloaddition reaction showed regioselectivity to internal triple bond of dialkynyl Fischer carbene complex without Cu(I) as catalyst. Anyway the carbene anchored was able to act as a reducing agent to produce in situ very stable gold nanoparticles fixed on surface. We showed the characterization of modified glasses by contact angle measurements and XPS. Synthesized nanoparticles were characterized by SEM, XPS, EDS and UV–vis. The modified glasses showed an important enhancement Raman-SERS. This simple, fast and robust method to create a polifunctional and hybrid surfaces can be valuable in a wide range of applications such as Raman-SERS substrates and other optical fields.

  9. Surface passivation of backside-illuminated InSb FPAs

    Science.gov (United States)

    Wei, Peng; Zheng, Kelin; Wang, Liwen; Geng, Dongfeng; Su, Xianjun

    2016-10-01

    A method of passivation of etch-thinned bulk InSb by anodic oxide grown by wet anodization and vacuum deposition of SiNx layers have been investigated Thinned bulk n-type InSb with (111) orientation forms distinctively two types of interfaces on the indium and antimony faces, respectively. The junctions are diffused on the indium face. The paper presents the process and characterization for surface passivation of the backside illuminated Sb face that absorbs the photons. The surface passivation and the interfaces are characterized with Metal-Insulator-Semiconductor (MIS) devices. The effect of anodic oxide/SiNx passivation was compared to SiNx passivation. The electrical features observed in the C-V curves of MIS structures indicate that anodic oxide grown by wet anodization has the better effect on reducing the surface states and surface recombination velocity. The low-frequency-like response in the inversion region of the C-V curves was explained in view of the oxidation states of In and Sb. Finally, by growing the 30nm anodic oxide and depositing 400nm SiNx on diode structure of InSb, the performance of FPA in this case was compared with the SiNx only method. The results showed the performance of device is better than for the SiNx only method.

  10. Surface passivation for single-molecule protein studies.

    Science.gov (United States)

    Chandradoss, Stanley D; Haagsma, Anna C; Lee, Young Kwang; Hwang, Jae-Ho; Nam, Jwa-Min; Joo, Chirlmin

    2014-04-24

    Single-molecule fluorescence spectroscopy has proven to be instrumental in understanding a wide range of biological phenomena at the nanoscale. Important examples of what this technique can yield to biological sciences are the mechanistic insights on protein-protein and protein-nucleic acid interactions. When interactions of proteins are probed at the single-molecule level, the proteins or their substrates are often immobilized on a glass surface, which allows for a long-term observation. This immobilization scheme may introduce unwanted surface artifacts. Therefore, it is essential to passivate the glass surface to make it inert. Surface coating using polyethylene glycol (PEG) stands out for its high performance in preventing proteins from non-specifically interacting with a glass surface. However, the polymer coating procedure is difficult, due to the complication arising from a series of surface treatments and the stringent requirement that a surface needs to be free of any fluorescent molecules at the end of the procedure. Here, we provide a robust protocol with step-by-step instructions. It covers surface cleaning including piranha etching, surface functionalization with amine groups, and finally PEG coating. To obtain a high density of a PEG layer, we introduce a new strategy of treating the surface with PEG molecules over two rounds, which remarkably improves the quality of passivation. We provide representative results as well as practical advice for each critical step so that anyone can achieve the high quality surface passivation.

  11. Evolution of anatase surface active sites probed by in situ sum-frequency phonon spectroscopy.

    Science.gov (United States)

    Cao, Yue; Chen, Shiyou; Li, Yadong; Gao, Yi; Yang, Deheng; Shen, Yuen Ron; Liu, Wei-Tao

    2016-09-01

    Surface active sites of crystals often govern their relevant surface chemistry, yet to monitor them in situ in real atmosphere remains a challenge. Using surface-specific sum-frequency spectroscopy, we identified the surface phonon mode associated with the active sites of undercoordinated titanium ions and conjoint oxygen vacancies, and used it to monitor them on anatase (TiO2) (101) under ambient conditions. In conjunction with theory, we determined related surface structure around the active sites and tracked the evolution of oxygen vacancies under ultraviolet irradiation. We further found that unlike in vacuum, the surface oxygen vacancies, which dominate the surface reactivity, are strongly regulated by ambient gas molecules, including methanol and water, as well as weakly associated species, such as nitrogen and hydrogen. The result revealed a rich interplay between prevailing ambient species and surface reactivity, which can be omnipresent in environmental and catalytic applications of titanium dioxides.

  12. PANIC - A surface science package for the in situ characterization of a near-Earth asteroid

    CERN Document Server

    Schindler, Karsten; Reddy, Vishnu; Weber, Andreas; Gruska, Stefan; Fasoulas, Stefanos

    2016-01-01

    This paper presents the results of a mission concept study for an autonomous micro-scale surface lander also referred to as PANIC - the Pico Autonomous Near-Earth Asteroid In Situ Characterizer. The lander is based on the shape of a regular tetrahedron with an edge length of 35 cm, has a total mass of approximately 12 kg and utilizes hopping as a locomotion mechanism in microgravity. PANIC houses four scientific instruments in its proposed baseline configuration which enable the in situ characterization of an asteroid. It is carried by an interplanetary probe to its target and released to the surface after rendezvous. Detailed estimates of all critical subsystem parameters were derived to demonstrate the feasibility of this concept. The study illustrates that a small, simple landing element is a viable alternative to complex traditional lander concepts, adding a significant science return to any near-Earth asteroid (NEA) mission while meeting tight mass budget constraints.

  13. In-situ observations of catalyst dynamics during surface-bound carbon nanotube nucleation

    DEFF Research Database (Denmark)

    Hofmann, S; Sharma, R; Du, G

    2007-01-01

    We present atomic-scale, video-rate environmental transmission electron microscopy and in situ time-resolved X-ray photoelectron spectroscopy of surface-bound catalytic chemical vapor deposition of single-walled carbon nanotubes and nanofibers. We observe that transition metal catalyst nanopartic......We present atomic-scale, video-rate environmental transmission electron microscopy and in situ time-resolved X-ray photoelectron spectroscopy of surface-bound catalytic chemical vapor deposition of single-walled carbon nanotubes and nanofibers. We observe that transition metal catalyst...... nanoparticles on SiOx support show crystalline lattice fringe contrast and high deformability before and during nanotube formation. A single-walled carbon nanotube nucleates by lift-off of a carbon cap. Cap stabilization and nanotube growth involve the dynamic reshaping of the catalyst nanocrystal itself...

  14. Potential Dependent Structural Changes of Underpotentially Deposited Copper on an Iodine Treated Platinum Surface Determined In Situ by Surface EXAFS and Its Polarization Dependence

    Science.gov (United States)

    1993-08-25

    of Underpotentially Deposited Copper on an Iodine Treated Platinum Surface Determined In Situ by Surface EXAFS and Its Polarization Dependence G.M...fiCAtson) Potential Dependent Structural Changes of Underpotentially Deposited Copper on an Irodine Treated Platinum Surface Determined In Situ by...necessary and identify by block number) An in situ structural investigation of the underpotential deposition of copper on an iodine covered platinum

  15. In situ monitoring of internal surface temperature of the historic building envelope

    Science.gov (United States)

    Labovská, Veronika; Katunský, Dušan

    2016-06-01

    Historical building envelope is characterized by a large accumulation that impact is mainly by changing the inner surface temperature over time. The minimum value of the inner surface temperature is set Code requirements. In the case of thermal technology assessment of building envelope contemplates a steady state external temperature and internal environment, thereby neglecting the heat accumulation capacity of building envelopes. Monitoring surface temperature in real terms in situ shows the real behavior of the building envelope close to reality. The recorded data can be used to create a numerical model for the simulation.

  16. Pulse Plating on Gold Surfaces Studied by In Situ Scanning Tunneling Microscopy

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Bech-Nielsen, Gregers; Møller, Per

    1994-01-01

    Deposition of bulk copper on thin film gold surfaces is carried out by computer-aided pulse plating. It is demonstrated that the morphology of the copper deposit can be studied by in situ scanning tunnelling microscopy both in potentiostatic experiments and in galvanostatic experiments. Optimized...... procedures for obtaining smooth deposits by pulse plating are explained in terms of a levelling effect. Possible non-faradaic processes observed in measurements with high frequency pulse plating are discussed....

  17. A Multivariate Regression Approach to Adjust AATSR Sea Surface Temperature to In Situ Measurements

    OpenAIRE

    TANDEO, Pierre; Autret, Emmanuelle; Piolle, Jean-francois; Tournadre, Jean; Ailliot, Pierre

    2009-01-01

    The Advanced Along-Track Scanning Radiometer (AATSR) onboard Envisat is designed to provide very accurate measurements of sea surface temperature (SST). Using colocated in situ drifting buoys, a dynamical matchup database (MDB) is used to assess the AATSR-derived SST products more precisely. SST biases are then computed. Currently, Medspiration AATSR SST biases are discrete values and can introduce artificial discontinuities in AATSR level-2 SST fields. The new AATSR SST biases presented in t...

  18. Pulse Plating on Gold Surfaces Studied by In Situ Scanning Tunneling Microscopy

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Bech-Nielsen, Gregers; Møller, Per

    1994-01-01

    Deposition of bulk copper on thin film gold surfaces is carried out by computer-aided pulse plating. It is demonstrated that the morphology of the copper deposit can be studied by in situ scanning tunnelling microscopy both in potentiostatic experiments and in galvanostatic experiments. Optimized...... procedures for obtaining smooth deposits by pulse plating are explained in terms of a levelling effect. Possible non-faradaic processes observed in measurements with high frequency pulse plating are discussed....

  19. In Situ Measurement of Surface Functional Groups on Silica Nanoparticles Using Solvent Relaxation Nuclear Magnetic Resonance.

    Science.gov (United States)

    Yuan, Li; Chen, Lan; Chen, Xiaohong; Liu, Renxiao; Ge, Guanglu

    2017-09-05

    In situ analysis and study on the surface of nanoparticles (NPs) is a key to obtain their important physicochemical properties for the subsequent applications. Of them, most works focus on the qualitative characterization whereas quantitative analysis and measurement on the NPs under their storage and usage conditions is still a challenge. In order to cope with this challenge, solvation relaxation-based nuclear magnetic resonance (NMR) technology has been applied to measure the wet specific surface area and, therefore, determine the number of the bound water molecules on the surface of silica NPs in solution and the hydrophilic groups of various types grafted on the surface of the NPs. By changing the surface functional group on silica particles, the fine distinction for the solvent-particle interaction with different surface group can be quantitatively differentiated by measuring the number of water molecules absorbed on the surface. The results show that the number of the surface hydroxyl, amine, and carboxyl group per nm(2) is 4.0, 3.7, and 2.3, respectively, for the silica particles with a diameter of 203 nm. The method reported here is the first attempt to determine in situ the number of bound solvent molecules and any solvophilic groups grafted on nanoparticles.

  20. Life cycle Greenhouse gas emissions of current Oil Sands Technologies: surface mining and in situ applications.

    Science.gov (United States)

    Bergerson, Joule A; Kofoworola, Oyeshola; Charpentier, Alex D; Sleep, Sylvia; Maclean, Heather L

    2012-07-17

    Life cycle greenhouse gas (GHG) emissions associated with two major recovery and extraction processes currently utilized in Alberta's oil sands, surface mining and in situ, are quantified. Process modules are developed and integrated into a life cycle model-GHOST (GreenHouse gas emissions of current Oil Sands Technologies) developed in prior work. Recovery and extraction of bitumen through surface mining and in situ processes result in 3-9 and 9-16 g CO(2)eq/MJ bitumen, respectively; upgrading emissions are an additional 6-17 g CO(2)eq/MJ synthetic crude oil (SCO) (all results are on a HHV basis). Although a high degree of variability exists in well-to-wheel emissions due to differences in technologies employed, operating conditions, and product characteristics, the surface mining dilbit and the in situ SCO pathways have the lowest and highest emissions, 88 and 120 g CO(2)eq/MJ reformulated gasoline. Through the use of improved data obtained from operating oil sands projects, we present ranges of emissions that overlap with emissions in literature for conventional crude oil. An increased focus is recommended in policy discussions on understanding interproject variability of emissions of both oil sands and conventional crudes, as this has not been adequately represented in previous studies.

  1. In situ probing of surface hydrides on hydrogenated amorphous silicon using attenuated total reflection infrared spectroscopy

    CERN Document Server

    Kessels, W M M; Sanden, M C M; Aydil, E S

    2002-01-01

    An in situ method based on attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is presented for detecting surface silicon hydrides on plasma deposited hydrogenated amorphous silicon (a-Si:H) films and for determining their surface concentrations. Surface silicon hydrides are desorbed by exposing the a-Si:H films to low energy ions from a low density Ar plasma and by comparing the infrared spectrum before and after this low energy ion bombardment, the absorptions by surface hydrides can sensitively be separated from absorptions by bulk hydrides incorporated into the film. An experimental comparison with other methods that utilize isotope exchange of the surface hydrogen with deuterium showed good agreement and the advantages and disadvantages of the different methods are discussed. Furthermore, the determination of the composition of the surface hydrogen bondings on the basis of the literature data on hydrogenated crystalline silicon surfaces is presented, and quantification of the h...

  2. Ice surface temperatures: seasonal cycle and daily variability from in-situ and satellite observations

    Science.gov (United States)

    Madsen, Kristine S.; Dybkjær, Gorm; Høyer, Jacob L.; Nielsen-Englyst, Pia; Rasmussen, Till A. S.; Tonboe, Rasmus T.

    2016-04-01

    Surface temperature is an important parameter for understanding the climate system, including the Polar Regions. Yet, in-situ temperature measurements over ice- and snow covered regions are sparse and unevenly distributed, and atmospheric circulation models estimating surface temperature may have large biases. To change this picture, we will analyse the seasonal cycle and daily variability of in-situ and satellite observations, and give an example of how to utilize the data in a sea ice model. We have compiled a data set of in-situ surface and 2 m air temperature observations over land ice, snow, sea ice, and from the marginal ice zone. 2523 time series of varying length from 14 data providers, with a total of more than 13 million observations, have been quality controlled and gathered in a uniform format. An overview of this data set will be presented. In addition, IST satellite observations have been processed from the Metop/AVHRR sensor and a merged analysis product has been constructed based upon the Metop/AVHRR, IASI and Modis IST observations. The satellite and in-situ observations of IST are analysed in parallel, to characterize the IST variability on diurnal and seasonal scales and its spatial patterns. The in-situ data are used to estimate sampling effects within the satellite observations and the good coverage of the satellite observations are used to complete the geographical variability. As an example of the application of satellite IST data, results will be shown from a coupled HYCOM-CICE ocean and sea ice model run, where the IST products have been ingested. The impact of using IST in models will be assessed. This work is a part of the EUSTACE project under Horizon 2020, where the ice surface temperatures form an important piece of the puzzle of creating an observationally based record of surface temperatures for all corners of the Earth, and of the ESA GlobTemperature project which aims at applying surface temperatures in models in order to

  3. In situ observation of surface structures of cardiovascular endothelial cells with atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    Tong Yin; Jin Luo; YaMin Ma; Xiao-Long Ji; Yu-Sheng Zhao; Shi-Wen Wang

    2009-01-01

    Objective To observe the surface structures of cardiovascular endothelial cells in situ with atomic force microscope (AFM). Methods Fresh aorta and aortic valve were dissected from 10 healthy male New Zealand white rabbits. Before fixed in 1% formaldehyde, the fresh tissues were washed in the buffer phosphate solution. Under general microscope, the fixed aorta or valve was spread on the double side stick tape which had already been stuck on the glass slide. The intima of aorta or the aorta side of valve was towards upside. Then the specimen was dried under 37 degrees centigrade in an attemperator and was washed with pure water. After dried again, the specimen was loaded on the platform ofNanoScope llla AFM and was scanned in tapping mode with the scanning speed of 0.5 HZ. Results The surface structures of endothelial cell on the fixed and dried tissue could be obsserved clearly in situ with AFM. Aortic endothclial cells were large, branched and arranged sparsely and parallel to the direction of blood flow, whereas endothelial cells on aorta valve surface were small, less branched and arranged intensively and vertical to the direction of blood flow. When the scanning range was dwindled, granular ultra-structures could be observed on the surface of endothelial cells, and, as the scanning range was dwindled further, fissure and convolution could be seen on the surface of granules from aortic endothelial cells. Centre cavity and surrounding swelling volcano-like structure could be seen on the surface of granules from endothelial cells of aortic valve. Conclusions It's feasible to observe the surface ultra-structures of cardiovascular endothelial cells in situ with AFM and morphological information provided by A FM might be of clinical value in future histopathological diagnosis.

  4. In situ REM and ex situ SPM studies of silicon (111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Aseev, A.L.; Kosolobov, S.S.; Latyshev, A.V. [Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Song, Se Ahn [Samsung Advanced Institute of Technology, POB 111 Suwon 440-600 (Korea); Saranin, A.A.; Zotov, A.V.; Lifshits, V.G. [The Institute of Automation and Control Processes, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok (Russian Federation)

    2005-09-01

    Combination of experimental methods, including ultrahigh vacuum in situ reflection electron microscopy, scanning tunnelling microscopy and atomic force microscopy, has been applied for analysis of surface structure and dynamic processes on silicon (111) surfaces during sublimation, rapid temperature cooling, oxygen reactions and metal-silicon surface phase formation. From analysis of triangular negative islands, 0.08 nm in depth, which were forming during quenching, it was deduced the effective activation energy of the island generation is equalled to {approx}0.35 eV and made conclusion that the (1 x 1)=>(7 x 7) phase transition on Si(111) assumes to be responsible for the negative island nucleation. On the base of the in situ REM study, the dependence of step motion, initiated by surface vacancies generation during oxygen-silicon interaction, on the terrace width was measured. Peculiarities of the initial stages of silicon surface oxidation at low pressures were considered. From precision measurements, the top silicon atom density was determined for the metal-silicon surface phase formed during Na, Ca, Mg and Ag deposition on clean silicon (111) surface. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Passive Optical Detection of a Vibrating Surface

    Science.gov (United States)

    2014-01-01

    medium from the incident side without change in frequency; reflectance is the fraction of the incident flux that is reflected.” Nicodemus defines more... differenced the images Figure 2. Bidirectional reflectance distribution function (BRDF) of spectralon (approximately Lambertian) and grass. (Reprinted...However, we have raised more questions than we have answered. For example, what fraction of the detected intensity modulation is from surface normal

  6. In-situ polymerization of polyaniline on the surface of graphene oxide for high electrochemical capacitance

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xinlu, E-mail: lixinlu@cqu.edu.cn; Zhong, Qineng; Zhang, Xinlin; Li, Tongtao; Huang, Jiamu

    2015-06-01

    Conducting polymer polyaniline (PANI) was in-situ polymerized on the surface of graphene oxide (GO) to form PANI encapsulating GO nanocomposites. The morphology and microstructure were examined by scanning electron microscopy, X-ray diffraction and N{sub 2} absorption/desorption analysis. Electrochemical properties were tested by cyclic voltammetry, galvanostatic charge/discharge cycles and electrochemical impedance spectroscopy. Experimental results showed that ethanol assisted the dispersion of GO in water and facilitated the diffusion of polymer monomers on GO. GO as a support material can provide sufficient reaction sites for the deposition of aniline to form the film-like GO/PANI composites. Capacitive performance illustrated that the in-situ polymerization of PANI on GO was effective in improving the specific capacitance and cycling stability. - Highlights: • GO/PANI nanocomposites were achieved by in-situ polymerization. • PANI was uniformly coated on the surface of GO with addition of ethanol. • GO/PANI show high specific capacitance and cycling stability.

  7. Simulated plasma facing component measurements for an in situ surface diagnostic on Alcator C-Moda)

    Science.gov (United States)

    Hartwig, Z. S.; Whyte, D. G.

    2010-10-01

    The ideal in situ plasma facing component (PFC) diagnostic for magnetic fusion devices would perform surface element and isotope composition measurements on a shot-to-shot (˜10 min) time scale with ˜1 μm depth and ˜1 cm spatial resolution over large areas of PFCs. To this end, the experimental adaptation of the customary laboratory surface diagnostic—nuclear scattering of MeV ions—to the Alcator C-Mod tokamak is being guided by ACRONYM, a Geant4 synthetic diagnostic. The diagnostic technique and ACRONYM are described, and synthetic measurements of film thickness for boron-coated PFCs are presented.

  8. In situ electrochemical scanning tunneling microscopy investigation of renewing graphite surface accompanied by electrochemical reaction

    Science.gov (United States)

    Zhang, Jingdong; Zhu, Guoyi; Wang, Erkang

    1996-08-01

    In situ electrochemical scanning tunneling microscopy (ECSTM) has been employed to follow the renewal process of a graphite electrode accompanied by flavin adenine dinucleotide (FAD) electrochemical reaction which involves adsorption of the reduced form (FADH 2) and desorption of the oxidized form (FAD). The renewal process initiates from steps or kinks on the electrode surface, which provide high active sites for adsorption. This renewal depends on the working electrode potential, especially in the range near the FAD redox potential. Our experiment suggests that delamination of the graphite surface is caused by interaction between the substrate and adsorbed molecules. A simple model is proposed to explain this phenomenon.

  9. Effets du traitement chimique de la surface d'une électrode négative en silicium amorphe pour batterie lithium-ion: étude par spectroscopie infrarouge in situ

    OpenAIRE

    Alves Dalla Corte, Daniel

    2013-01-01

    140 pages, 152 references; Silicon represents an expressive gain in energy density for negative electrodes in Li-ion batteries. Reversible cycling and long term stability of silicon electrodes are both dependent of the passivation efficiency of the solid electrolyte interface (SEI) layer formed at the electrode surface. Surface and bulk phenomena of amorphous silicon were studied by in-situ FTIR spectroscopy during electrochemical cycling. Electrodes were prepared by thin-film deposition of h...

  10. Validation of Land Surface Temperature products in arid climate regions with permanent in-situ measurements

    Science.gov (United States)

    Goettsche, F.; Olesen, F.; Trigo, I.; Hulley, G. C.

    2013-12-01

    Land Surface Temperature (LST) is operationally obtained from several space-borne sensors, e.g. from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard Meteosat Second Generation (MSG) by the Land Surface Analysis - Satellite Application Facility (LSA-SAF) and from the Moderate Resolution Imaging Spectroradiometer (MODIS) on EOS-Terra by the MODIS Land Team. The relative accuracy of LST products can be assessed by cross-validating different products. Alternatively, the so-called 'radiance based validation' can be used to compare satellite-retrieved LST with results from radiative transfer models: however, this requires precise a priori knowledge of land surface emissivity (LSE) and atmospheric conditions. Ultimately, in-situ measurements (';ground truth') are needed for validating satellite LST&E products. Therefore, the LST product derived by LSA-SAF is validated with independent in-situ measurements (';temperature based validation') at permanent validation stations located in different climate regions on the SEVIRI disk. In-situ validation is largely complicated by the spatial scale mismatch between satellite sensors and ground based sensors, i.e. areas observed by ground radiometers usually cover about 10 m2, whereas satellite measurements in the thermal infrared typically cover between 1 km2 and 100 km2. Furthermore, an accurate characterization of the surface is critical for all validation approaches, but particularly over arid regions, as shown by in-situ measurements revealing that LSE products can be wrong by more than 3% [1]. The permanent stations near Gobabeb (Namibia; hyper-arid desert climate) and Dahra (Senegal; hot-arid steppe-prairie climate) are two of KIT's four dedicated LST validation stations. Gobabeb station is located on vast and flat gravel plains (several 100 km2), which are mainly covered by coarse gravel, sand, and desiccated grass. The gravel plains are highly homogeneous in space and time, which makes them ideal for

  11. Reduction of trapped ion anomalous heating by in situ surface plasma cleaning

    CERN Document Server

    McConnell, Robert; Chiaverini, John; Sage, Jeremy

    2015-01-01

    Anomalous motional heating is a major obstacle to scalable quantum information processing with trapped ions. While the source of this heating is not yet understood, several previous studies suggest that surface contaminants may be largely responsible. We demonstrate an improvement by a factor of four in the room-temperature heating rate of a niobium surface electrode trap by in situ plasma cleaning of the trap surface. This surface treatment was performed with a simple homebuilt coil assembly and commercially-available matching network and is considerably gentler than other treatments, such as ion milling or laser cleaning, that have previously been shown to improve ion heating rates. We do not see an improvement in the heating rate when the trap is operated at cryogenic temperatures, pointing to a role of thermally-activated surface contaminants in motional heating whose activity may freeze out at low temperatures.

  12. Inter-Comparison of In-Situ Sensors for Land Surface Temperature Measurements

    Science.gov (United States)

    Krishnan, P.; Kochendorfer, J.; Meyers, T. P.; Guillevic, P. C.; Hook, S. J.

    2014-12-01

    Land Surface Temperature (LST) is a key variable in the determination of land surface processes from local to global scales. It has been identified as one of the most important environmental data records and is widely used in meteorological, climatological, hydrological, ecological, biophysical, and biochemical studies. Despite its importance, accurate in-situ measurements of LST are not yet available for the whole globe and are not routinely conducted at weather stations along with standard meteorological observations, with few exceptions including NOAA's United States Climate Reference Network. Even though satellite radiometric measurements of LST are a powerful tool, there are still large uncertainties associated with the retrieval of remotely sensed LST measurements. To improve confidence in the methods, algorithms, and parameters used to derive remotely sensed LST, validation of satellite data using high-quality ground-based measurements is required. With the objective of improving the quality of in situ measurements of LST and to evaluate the quantitative uncertainties in the ground-based measurements, intensive experiments were conducted at NOAA/ATDD in Oak ridge, TN from September 2013 to 2014. During the study period, multiple measurements of land surface skin temperature were made using infra-red temperature sensors - including the JPL radiometer, two models of Apogee infrared radiometers, and thermocouples embedded in the ground surface. In addition, aspirated air temperature and four-band net radiation measurements were also made. Overall the in situ LST measurements from the different sensors were in good agreement with each other, with a correlation coefficient of ~1 and root mean square error of <1 oC.

  13. Surface Enhanced Raman Scattering Based in Situ Hybridization Strategy for Telomere Length Assessment.

    Science.gov (United States)

    Zong, Shenfei; Chen, Chen; Wang, Zhuyuan; Zhang, Yizhi; Cui, Yiping

    2016-02-23

    Assessing telomere length is of vital importance since telomere length is closely related with several fatal diseases such as atherosclerosis and cancer. Here, we present a strategy to assess/measure telomere length, that is, surface enhanced Raman scattering (SERS) based in situ hybridization (SISH). The SISH method uses two kinds of SERS nanoprobes to hybridize in situ with telomeres and centromeres, respectively. The telomere specific SERS nanoprobe is called the Telo-probe, while the centromere specific SERS nanoprobe is called the Centro-probe. They are composed of metal nanoparticles (NPs), Raman reporter molecules and specially designed DNA strands. With longer telomeres, more Telo-probes will hybridize with them, resulting in a stronger SERS signal. To exclude possible influence of the SERS intensity by external factors (such as the nanoprobe concentration, the cell number or different batches of nanoprobes), centromeres are used as the inner control, which can be recognized by Centro-probes. Telomere length is evaluated using a redefined telomere-to-centromere ratio (T/C ratio). The calculation method for T/C ratio in SISH method is more reliable than that in fluorescent in situ hybridization (FISH). In addition, unlike FISH method, the SISH method is insensitive to autofluorescence. Moreover, SISH method can be used to analyze single telomeres. These features make SISH an excellent alternative strategy for telomere length measurement.

  14. In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces

    Science.gov (United States)

    Lupo, Fabio; Tudisco, Cristina; Bertani, Federico; Dalcanale, Enrico

    2014-01-01

    Summary Free 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100) and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring–surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm−1 due to –NH stretches. Finally, XPS results revealed that the different surface–phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process. PMID:25551050

  15. In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces

    Directory of Open Access Journals (Sweden)

    Fabio Lupo

    2014-11-01

    Full Text Available Free 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100 and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring–surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm−1 due to –NH stretches. Finally, XPS results revealed that the different surface–phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process.

  16. Bulk crystalline copper electrodeposition on polycrystalline gold surfaces observed by in-situ scanning tunneling microscopy

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Bech-Nielsen, Gregers; Møller, Per

    1994-01-01

    Bulk copper electrodeposition onto technical gold surfaces in electrolytes of 0.05 M H2SO4 and 1 mM CuSO4 was investigated by in-situ scanning tunnelling microscopy at fixed overpotentials. At potentials between -60 and -30 mV the growth of bulk copper proceeds in cycles of nucleation, agglomerat......Bulk copper electrodeposition onto technical gold surfaces in electrolytes of 0.05 M H2SO4 and 1 mM CuSO4 was investigated by in-situ scanning tunnelling microscopy at fixed overpotentials. At potentials between -60 and -30 mV the growth of bulk copper proceeds in cycles of nucleation......, agglomeration and crystallization. Crystalline copper is seen as involving an intermediate stage in the progress of growth. The final stage in the growth involves an equilibrium of copper electrochemically dissolving and precipitating. The drift velocity was measured for a gold surface subjected to flame...... annealing and subsequently installed in the cell compartment. It was found that the drift velocity decays with time in an exponential-like manner, and a 70 min waiting time before experiments with atomic resolution is recommended. Atomic resolution on Au(111) has been obtained, and an apparent surface...

  17. Does equilibrium passive sampling reflect actual in situ bioaccumulation of PAHs and petroleum hydrocarbon mixtures in aquatic worms?

    NARCIS (Netherlands)

    Muijs, B.; Jonker, M.T.O.

    2012-01-01

    Over the past couple of years, several analytical methods have been developed for assessing the bioavailability of environmental contaminants in sediments and soils. Comparison studies suggest that equilibrium passive sampling methods generally provide the better estimates of internal concentrations

  18. Laser-based mass spectrometry for in situ chemical composition analysis of planetary surfaces

    Science.gov (United States)

    Frey, Samira; Neuland, Maike B.; Grimaudo, Valentine; Moreno-García, Pavel; Riedo, Andreas; Tulej, Marek; Broekmann, Peter; Wurz, Peter

    2016-04-01

    Mass spectrometry is an important analytical technique in space research. The chemical composition of planetary surface material is a key scientific question on every space mission to a planet, moon or asteroid. Chemical composition measurements of rocky material on the surface are of great importance to understand the origin and evolution of the planetary body.[1] A miniature laser ablation/ionisation reflectron- type time-of-flight mass spectrometer (instrument name LMS) was designed and built at the University of Bern for planetary research.[2] Despite its small size and light weight, the LMS instrument still maintains the same capabilities as large laboratory systems, which makes it suitable for its application on planetary space missions.[3-5] The high dynamic range of about eight orders of magnitude, high lateral (μm-level) and vertical (sub-nm level) resolution and high detection sensitivity for almost all elements (10 ppb, atomic fraction) make LMS a versatile instrument for various applications. LMS is a suitable instrument for in situ measurements of elemental and isotope composition with high precision and accuracy. Measurements of Pb- isotope abundances can be used for dating of planetary material. Measurements of bio-relevant elements allow searching for past or present life on a planetary surface. The high spatial resolution, both in lateral and vertical direction, is of considerable interest, e.g. for analysis of inhomogeneous, extraterrestrial samples as well as weathering processes of planetary material. References [1] P. Wurz, D. Abplanalp, M. Tulej, M. Iakovleva, V.A. Fernandes, A. Chumikov, and G. Managadze, "Mass Spectrometric Analysis in Planetary Science: Investigation of the Surface and the Atmosphere", Sol. Sys. Res., 2012, 46, 408. [2] U. Rohner, J.A. Whitby, P. Wurz, "A miniature laser ablation time of flight mass spectrometer for in situ planetary exploration" Meas. Sci. Tch., 2003, 14, 2159. [3] M. Tulej, A. Riedo, M.B. Neuland, S

  19. In situ studies of complex PLD-grown films using hard X-ray surface diffraction

    Science.gov (United States)

    Willmott, P. R.; Schlepütz, C. M.; Patterson, B. D.; Herger, R.; Lange, M.; Meister, D.; Maden, D.; Brönnimann, Ch.; Eikenberry, E. F.; Hülsen, G.; Al-Adwan, A.

    2005-07-01

    A novel ultra-high vacuum chamber for growing films via pulsed laser deposition and studying the growth processes in situ using hard synchrotron radiation is presented. The chamber is mounted onto a 5-circle surface diffractometer and contains a large cylindrical-section beryllium window, which allows an extensive range of reciprocal space to be probed. The chamber is primarily used to perform surface diffraction measurements, for which much of the most valuable information derives from the weakest signals. With this in mind, we have employed a photon-counting area pixel detector system, which reduces data acquisition times by one to two orders of magnitude and concomitantly increases the potential volume of data that can be acquired for any given sample before the surface degrades due to surface contamination or radiation damage. Examples are presented of initial results obtained using this system.

  20. In situ investigation of the mobility of small gold clusters on cleaved MgO surfaces

    Science.gov (United States)

    Metois, J. J.; Heinemann, K.; Poppa, H.

    1976-01-01

    The mobility of small clusters of gold (about 10 A in diameter) on electron-beam-cleaved MgO surfaces was studied by in situ transmission electron microscopy under controlled vacuum and temperature conditions. During the first 10 min following a deposition at room temperature, over 10 per cent of the crystallites moved over short distances (about 20 A) discontinuously, with a velocity greater than 150 A/sec. Eighty per cent of the mobility events were characterized by the avoidance of proximity of other crystallites, and this was tentatively explained as the result of repulsive elastic forces between the interacting crystallites.

  1. In situ surface reduction of a NiO-YSZ-alumina composite using scanning probe microscopy

    DEFF Research Database (Denmark)

    Hansen, Karin Vels; Jacobsen, Torben; Thydén, Karl Tor Sune

    2014-01-01

    In situ surface reductions of NiO-YSZ-Al2O3 composites into Ni-YSZ-Al2O3 cermets were carried out at 312–525 °C in a controlled atmosphere high-temperature scanning probe microscope (CAHT-SPM) in dry and humidified 9 % H2 in N2. The reduction of NiO was followed by contact mode scanning...... dependent and followed the Arrhenius equation. For samples reduced in dry hydrogen, the Arrhenius plot showed two regions with different activation energies. Scanning electron microscopy confirmed a difference in microstructure between these temperature regimes. A strong retarding effect of steam (H2O...

  2. In situ monitoring of biomolecular processes in living systems using surface-enhanced Raman scattering

    Science.gov (United States)

    Altunbek, Mine; Kelestemur, Seda; Culha, Mustafa

    2015-12-01

    Surface-enhanced Raman scattering (SERS) continues to strive to gather molecular level information from dynamic biological systems. It is our ongoing effort to utilize the technique for understanding of the biomolecular processes in living systems such as eukaryotic and prokaryotic cells. In this study, the technique is investigated to identify cell death mechanisms in 2D and 3D in vitro cell culture models, which is a very important process in tissue engineering and pharmaceutical applications. Second, in situ biofilm formation monitoring is investigated to understand how microorganisms respond to the environmental stimuli, which inferred information can be used to interfere with biofilm formation and fight against their pathogenic activity.

  3. Solution-processed amorphous silicon surface passivation layers

    Energy Technology Data Exchange (ETDEWEB)

    Mews, Mathias, E-mail: mathias.mews@helmholtz-berlin.de; Sontheimer, Tobias; Korte, Lars; Rech, Bernd [Helmholtz-Zentrum Berlin, Institute of Silicon Photovoltaics, Kekuléstraße 5, D-12489 Berlin (Germany); Mader, Christoph; Traut, Stephan; Wunnicke, Odo [Evonik Industries AG, Creavis Technologies and Innovation, Paul-Baumann-Straße 1, D-45772 Marl (Germany)

    2014-09-22

    Amorphous silicon thin films, fabricated by thermal conversion of neopentasilane, were used to passivate crystalline silicon surfaces. The conversion is investigated using X-ray and constant-final-state-yield photoelectron spectroscopy, and minority charge carrier lifetime spectroscopy. Liquid processed amorphous silicon exhibits high Urbach energies from 90 to 120 meV and 200 meV lower optical band gaps than material prepared by plasma enhanced chemical vapor deposition. Applying a hydrogen plasma treatment, a minority charge carrier lifetime of 1.37 ms at an injection level of 10{sup 15}/cm{sup 3} enabling an implied open circuit voltage of 724 mV was achieved, demonstrating excellent silicon surface passivation.

  4. In situ high temperature microscopy study of the surface oxidation and phase transformations in titanium alloys.

    Science.gov (United States)

    Malinov, S; Sha, W; Voon, C S

    2002-09-01

    Two popular commercial titanium alloys, Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.08Si, were used for in situ high temperature microscopy study. The experiments were performed on an optical microscope equipped with high temperature stage using both normal and florescence lights. Two kinds of experiments were performed, at continuous heating/cooling with different rates and in isothermal conditions at different temperatures. The changes taking place on the sample surface during the experiments were monitored. The morphology of the alpha ==> beta ==> alpha phase transformation was recorded at different heat treatment conditions using the effect of thermal etching. An effect of sample surface oxidation and deoxidation was observed during continuous heating. The appearance and disappearance of ordered titanium oxides Ti3O and Ti2O are discussed based on the phase equilibrium diagram. The kinetics of the surface oxidation was monitored in both isothermal and continuous cooling conditions.

  5. In situ observation of surface morphology evolution in tungsten under focused Ga{sup +} ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ran Guang, E-mail: gran@umich.edu [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Liu Xiang; Wu Jihong [Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Li Ning [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Zu Xiaotao [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Wang Lumin, E-mail: lmwang@umich.edu [School of Energy Research, Xiamen University, Xiamen, Fujian 361005 (China); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

    2012-05-15

    The effects of energetic Ga ion bombardment on the surface morphology of mechanically polished polycrystalline tungsten are investigated by focused Ga{sup +} ion beam irradiation with in situ scanning electron microscopy, as well as ex situ atomic force microscopy. The amount of removed material from the tungsten surface increased with increasing of incident ion angle, and also increased with ion energy from 5 to 30 keV while keeping all other bombardment parameters constant. The nanoneedle-shaped morphology formed by self-assembly in the surface of tungsten under off-normal angle bombardment, the larger the incident angle, the easier for the needle formation. In contrast, only a net-like microstructure formed under normal incident angle. Moreover, more Ga{sup +} ion fluence was needed to form pores at normal incident angle comparing to that under 52 Degree-Sign incident angle.

  6. Nanoscale characterization of gold nanoparticles created by in situ reduction at a polymeric surface.

    Science.gov (United States)

    Dutta, A; Clukay, C J; Grabill, C N; Freppon, D J; Bhattacharya, A; Kuebler, S M; Heinrich, H

    2013-07-01

    Transmission Electron Microscopy is used as a quantitative method to measure the shapes, sizes and volumes of gold nanoparticles created at a polymeric surface by three different in situ synthesis methods. The atomic number contrast (Z-contrast) imaging technique reveals nanoparticles which are formed on the surface of the polymer. However, with certain reducing agents, the gold nanoparticles are additionally found up to 20 nm below the polymer surface. In addition, plan-view high-angle annular dark-field scanning transmission electron microscopy images were statistically analyzed on one sample to measure the volume, height and effective diameter of the gold nanoparticles and their size distributions. Depth analysis from high-angle annular dark-field scanning transmission electron microscopy micrographs also gives information on the dominant shape of the nanoparticles.

  7. Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ.

    Science.gov (United States)

    Barbosa, Renata Pereira de Sousa; Pereira-Cenci, Tatiana; Silva, Wagner Missio da; Coelho-de-Souza, Fabio Herrmann; Demarco, Flávio Fernando; Cenci, Maximiliano Sérgio

    2012-05-01

    The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge. In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR - Z250) or resin-modified glass ionomer (RMGI - Vitremer). Two phases of 14 days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100 μg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL). All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation=8.9 and with biofilm accumulation=25.6, CR without biofilm accumulation=14.7 and with biofilm accumulation=17.0. Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin. The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. In Situ Production of Hard Metal Matrix Composite Coating on Engineered Surfaces Using Laser Cladding Technique

    Science.gov (United States)

    Raza, Mohammad Shahid; Hussain, Manowar; Kumar, Vikash; Das, Alok Kumar

    2016-11-01

    The growing need for high wear-resistant surface with enhanced physical properties has led to extensive researches in the field of surface engineering. Laser cladding emerged to be a promising method to achieve these objectives in a cost-effective way. The present paper studies the viability of cladding of tungsten disulfide (WS2) powder by using 400 W continuous-wave fiber laser. WS2 was used as a coating material, which was decomposed at higher temperature and underwent several chemical reactions. By this process, in situ formation of metal matrix composites and hard face coating on the substrate surface were attained. The characterization of laser cladded surface was done to study its morphological, microstructural, mechanical and tribological properties. It was observed that cladding of WS2 powder on 304 SS resulted in the formation of Cr-W-C-Fe metal matrix composite having improved mechanical and tribological properties. The value of microhardness of the coated surface was found to increase three to four times in comparison with the parent material surface. Wear test results indicated a decrease in wear by 1/9th (maximum) as compared to the parent 304 SS surface. The volume fractions of tungsten particles on the cladded surface were also investigated through EDS analysis.

  9. Evaluation of surface layer flux parameterizations using in-situ observations

    Science.gov (United States)

    Katz, Jeremy; Zhu, Ping

    2017-09-01

    Appropriate calculation of surface turbulent fluxes between the atmosphere and the underlying ocean/land surface is one of the major challenges in geosciences. In practice, the surface turbulent fluxes are estimated from the mean surface meteorological variables based on the bulk transfer model combined with the Monnin-Obukhov Similarity (MOS) theory. Few studies have been done to examine the extent to which such a flux parameterization can be applied to different weather and surface conditions. A novel validation method is developed in this study to evaluate the surface flux parameterization using in-situ observations collected at a station off the coast of Gulf of Mexico. The main findings are: (a) the theoretical prediction that uses MOS theory does not match well with those directly computed from the observations. (b) The largest spread in exchange coefficients is shown in strong stable conditions with calm winds. (c) Large turbulent eddies, which depend strongly on the mean flow pattern and surface conditions, tend to break the constant flux assumption in the surface layer.

  10. In Situ Production of Hard Metal Matrix Composite Coating on Engineered Surfaces Using Laser Cladding Technique

    Science.gov (United States)

    Raza, Mohammad Shahid; Hussain, Manowar; Kumar, Vikash; Das, Alok Kumar

    2017-01-01

    The growing need for high wear-resistant surface with enhanced physical properties has led to extensive researches in the field of surface engineering. Laser cladding emerged to be a promising method to achieve these objectives in a cost-effective way. The present paper studies the viability of cladding of tungsten disulfide (WS2) powder by using 400 W continuous-wave fiber laser. WS2 was used as a coating material, which was decomposed at higher temperature and underwent several chemical reactions. By this process, in situ formation of metal matrix composites and hard face coating on the substrate surface were attained. The characterization of laser cladded surface was done to study its morphological, microstructural, mechanical and tribological properties. It was observed that cladding of WS2 powder on 304 SS resulted in the formation of Cr-W-C-Fe metal matrix composite having improved mechanical and tribological properties. The value of microhardness of the coated surface was found to increase three to four times in comparison with the parent material surface. Wear test results indicated a decrease in wear by 1/9th (maximum) as compared to the parent 304 SS surface. The volume fractions of tungsten particles on the cladded surface were also investigated through EDS analysis.

  11. In situ scanning tunneling microscopy study of the structure of the hydroxylated anodic oxide film formed on Cr(110) single-crystal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zuili, D.; Maurice, V.; Marcus, P. [Ecole Nationale Superieure de Chimie de Paris (France)

    1999-09-16

    The structure of hydroxylated oxide films (passive films) formed on Cr(110) in 0.5 M H{sub 2}SO{sub 4} at +0.35, +0.55, and +0.75 V/SHE has been investigated by in situ scanning tunneling microscopy (STM). Cathodic reduction pretreatments at {minus}0.54, {minus}0.64, and {minus}0.74 V/SHE destroy the well-defined topography of the single-crystal electrode and they have been excluded from the passivation procedure. Two different passive film structures have been observed, depending on the potential and time of passivation. At low potential (+0.35 V/SHE), the passive film, consisting mostly of chromium hydroxide, has a noncrystalline and granular structure whose roughness suggests local variations of thickness of ca. {+-} 0.5 nm. A similar structure is observed at higher potential (+0.55 V/SHE), but only for a short polarization time. For longer polarization at 0.55 V/SHE, and at higher potentials (+0.75 V/SHE), a crystalline structure is formed; the higher the potential, the faster the crystallization. It corresponds to the growth of a chromium oxide layer in the passive film. This chromium oxide layer is (0001) oriented. A structural model of the passive film is proposed, with termination of this oxide layer by a monolayer of hydroxyl groups or of chromium hydroxide in (1 {times} 1) epitaxy with the underlying oxide, and with surface steps resulting from the emergence of stacking faults of the Cr{sup 3+} planes in the oxide layer. Energy band models of the electronic structure of the semiconductive passive films show that the tunneling mechanism of the STM imaging involves empty electronic states located in the band gap of the passive film. The growth of the oxide layer in the passive film is governed by a combined reaction of dehydration of chromium hydroxide and oxidation of chromium: Cr(OH){sub 3} (film) + Cr (metal) {yields} Cr{sub 2}O{sub 3} (film) + 3 H{sup +} + 3 e{sup {minus}}.

  12. In situ bioavailability of DDT and Hg in sediments of the Toce River (Lake Maggiore basin, Northern Italy): accumulation in benthic invertebrates and passive samplers.

    Science.gov (United States)

    Pisanello, Francesca; Marziali, Laura; Rosignoli, Federica; Poma, Giulia; Roscioli, Claudio; Pozzoni, Fiorenzo; Guzzella, Licia

    2016-06-01

    DDT and mercury (Hg) contamination in the Toce River (Northern Italy) was caused by a factory producing technical DDT and using a mercury-cell chlor-alkali plant. In this study, DDT and Hg contamination and bioavailability were assessed by using different approaches: (1) direct evaluation of sediment contamination, (2) assessment of bioaccumulation in native benthic invertebrates belonging to different taxonomic/functional groups, and (3) evaluation of the in situ bioavailability of DDT and Hg using passive samplers. Sampling sites were selected upstream and downstream the industrial plant along the river axis. Benthic invertebrates (Gammaridae, Heptageniidae, and Diptera) and sediments were collected in three seasons and analyzed for DDT and Hg content and the results were used to calculate the biota sediment accumulation factor (BSAF). Polyethylene passive samplers (PEs) for DDT and diffusive gradients in thin films (DGTs) for Hg were deployed in sediments to estimate the concentration of the toxicants in pore water. Analysis for (DDx) were performed using GC-MS. Accuracy was within ±30 % of the certified values and precision was >20 % relative standard deviation (RSD). Total mercury concentrations were determined using an automated Hg mercury analyzer. Precision was >5 % and accuracy was within ±10 % of certified values. The results of all the approaches (analysis of sediment, biota, and passive samplers) showed an increasing contamination from upstream to downstream sites. BSAF values revealed the bioavailability of both contaminants in the study sites, with values up to 49 for DDx and up to 3.1 for Hg. No correlation was found between values in sediments and the organisms. Concentrations calculated using passive samplers were correlated with values in benthic invertebrates, while no correlation was found with concentrations in sediments. Thus, direct analysis of toxicant in sediments does not provide a measurement of bioavailability. On the contrary

  13. In-situ detection of multiple pathogenic bacteria on food surfaces

    Science.gov (United States)

    Chai, Yating; Horikawa, Shin; Hu, Jiajia; Chen, I.-Hsuan; Hu, Jing; Barbaree, James M.; Chin, Bryan A.

    2015-05-01

    Real-time in-situ detection of pathogenic bacteria on fresh food surfaces was accomplished with phage-based magnetoelastic (ME) biosensors. The ME biosensor is constructed of a small rectangular strip of ME material that is coated with a biomolecular recognition element (phage, antibodies or proteins, etc.) that is specific to the target pathogen. This mass-sensitive ME biosensor is wirelessly actuated into mechanical resonance by an externally applied time-varying magnetic field. When the biosensor binds with target bacteria, the mass of the sensor increases, resulting in a decrease in the sensor's resonant frequency. In order to compensate for nonspecific binding, control biosensors without phage were used in this experiment. In previous research, the biosensors were measured one by one. However, the simultaneous measurement of multiple sensors was accomplished in this research, and promises to greatly shorten the analysis time for bacterial detection. Additionally, the use of multiple biosensors enables the possibility of simultaneous detection of different pathogenic bacteria. This paper presents results of experiments in which multiple phage-based ME biosensors were simultaneously monitored. The E2 phage and JRB7 phage from a landscape phage library served as the bio-recognition element that have the capability of binding specifically with Salmonella typhimurium and B. anthracis spores, respectively. Real-time in-situ detection of Salmonella typhimurium and B. anthracis spores on food surfaces are presented.

  14. AN IN SITU SURFACE COMPOSITE AND GRADIENT MATERIALOF Al-Si ALLOY PRODUCED BY ELECTROMAGNETIC FORCE

    Institute of Scientific and Technical Information of China (English)

    Z.M. Xu; T.X. Li; Z.L. Zhu; Y.H. Zhou

    2001-01-01

    Because of the different conductivities between the primary phase (law electric conductivity) and the metal melt, electromagnetic force scarcely acts on the primary phase.Thus, an electromagnetic repulsive force applied by the metal melt exerts on the primary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this,a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-19wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.``

  15. In Situ Atomic Scale Visualization Of Surface Kinetics Driven Dynamics Of Oxide Growth On A Ni–Cr Surface

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Langli; Zou, Lianfeng; Schreiber, Daniel K.; Olszta, Matthew J.; Baer, Donald R.; Bruemmer, Stephen M.; Zhou, Guangwen; Wang, Chong M.

    2016-01-20

    We report in situ atomic-scale visualization of the dynamical three-dimensional (3D) growth of NiO during initial oxidation of Ni-10at%Cr using environmental transmission electron microscopy (ETEM). Despite the thermodynamic preference for Cr2O3 formation, cubic NiO oxides nucleated and grew epitaxially as the dominating oxide phase on the Ni-Cr (100) surface during initial oxidation. The growth of NiO islands proceeds through step-by-step adatom mechanism in 3D, which is sustained by surface diffusion of Ni and O atoms. Although the shapes of oxide islands are controlled by strain energy between oxide and alloy substrate, local surface kinetic variations can lead to the change of surface planes of oxide islands. These results demonstrate that surface diffusion dominates initial oxidation of Ni-Cr in these test conditions.

  16. Characterization, optimization and surface physics aspects of in situ plasma mirror cleaning.

    Science.gov (United States)

    Pellegrin, Eric; Sics, Igors; Reyes-Herrera, Juan; Perez Sempere, Carlos; Lopez Alcolea, Juan Josep; Langlois, Michel; Fernandez Rodriguez, Jose; Carlino, Vincent

    2014-03-01

    Although the graphitic carbon contamination of synchrotron beamline optics has been an obvious problem for several decades, the basic mechanisms underlying the contamination process as well as the cleaning/remediation strategies are not understood and the corresponding cleaning procedures are still under development. In this study an analysis of remediation strategies all based on in situ low-pressure RF plasma cleaning approaches is reported, including a quantitative determination of the optimum process parameters and their influence on the chemistry as well as the morphology of optical test surfaces. It appears that optimum results are obtained for a specific pressure range as well as for specific combinations of the plasma feedstock gases, the latter depending on the chemical aspects of the optical surfaces to be cleaned.

  17. PTCDA induced faceting of a vicinal Ag(111) surface: an in-situ LEEM study

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Thomas; Marchetto, Helder; Sala, Alessandro; Freund, Hajo [Fritz-Haber-Institut, Abt. CP, 14195 Berlin (Germany); Pollinger, Florian; Schmitt, Stefan; Maier, Florian C.; Reinert, Friedrich T. [Universitaet Wuerzburg, EP II, 97074 Wuerzburg (Germany); Umbach, Eberhard [Universitaet Wuerzburg, EP II, 97074 Wuerzburg (Germany); Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)

    2009-07-01

    Adsorption of organic molecules on vicinal metal surfaces is known to promote faceting and self-organized ordering on mesoscopic scales. In the temperature range between 400 K and 620 K the adsorption of PTCDA on a Ag(10 8 7) surface has been studied in-situ and in real-time by LEEM (low energy electron microscopy) and LEED, using the SMART microscope. The deposition of one organic layer leads to grating-like structures. The direct observation reveals a two-step process: first, facets with an angle of ca. 25 inclination are formed with (111) orientated areas in between, whereas only the facets are covered by PTCDA. In a second step the bare (111) areas are covered by PTCDA, forming a complete monolayer. The temperature dependence of the structure sizes and the influence of inhomogeneity in the initial substrate step density are discussed.

  18. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    KAUST Repository

    Cai, Mick Y.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  19. Rapid Optical Characterization Suite for in situ Target Analysis of Rock Surfaces Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ROCSTAR is an in situ instrument suite that can accomplish rapid mineral and molecular identification without sample preparation for in situ planetary exploration;...

  20. Optical properties of Si nanoclusters with passivated surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, L.N. [Univ. of California, Davis, CA (United States). Dept. of Applied Science]|[Lawrence Livermore National Lab., CA (United States). Chemistry and Materials Science Dept.; Chase, L.L.; Balooch, M.; Siekhaus, W.J. [Lawrence Livermore National Lab., CA (United States). Chemistry and Material Science Dept.; Wooten, F. [Univ. of California, Davis, CA (United States). Dept. of Applied Science

    1996-12-31

    Si nanoclusters with average size of a few nanometers have been synthesized by thermal vaporization of Si in an Ar buffer gas, and passivated with oxygen or atomic hydrogen. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) revealed that these nanoclusters were crystalline. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times form nanoseconds to microseconds depending on synthesis conditions. Absorption mainly in the Si cores was observed by photoluminescence excitation (PLE) spectroscopy. The visible components of PL spectra were noted to blue shift and broaden as the size of the Si nanocrystals (nc-Si) was reduced, and there were differences in PL spectra for hydrogen and oxygen passivated nc-Si. This data can be explained best by a model involving absorption between quantum confined states in the Si cores and emission by surface/interface states.

  1. Passive Downhole Pressure Sensor Based on Surface Acoustic Wave Technology.

    Science.gov (United States)

    Quintero, Sully M M; Figueiredo, Sávio W O; Takahashi, Victor L; Llerena, Roberth A W; Braga, Arthur M B

    2017-07-15

    A passive surface acoustic wave (SAW) pressure sensor was developed for real-time pressure monitoring in downhole application. The passive pressure sensor consists of a SAW resonator, which is attached to a circular metal diaphragm used as a pressure transducer. While the membrane deflects as a function of pressure applied, the frequency response changes due to the variation of the SAW propagation parameters. The sensitivity and linearity of the SAW pressure sensor were measured to be 8.3 kHz/bar and 0.999, respectively. The experimental results were validated with a hybrid analytical-numerical analysis. The good results combined with the robust design and packaging for harsh environment demonstrated it to be a promising sensor for industrial applications.

  2. Structure of a passivated Ge surface prepared from aqueous solution.

    Energy Technology Data Exchange (ETDEWEB)

    Lyman, P. F.; Sakata, O.; Marasco, D, L.; Lee, T.-L.; Breneman, K. D.; Keane, D. T.; Bedzyk, M. J.; Materials Science Division; Northwestern Univ.; Univ. of Wisconsin at Milwaukee

    2000-08-10

    The structure of a passivating sulfide layer on Ge(001) was studied using X-ray standing waves and X-ray fluorescence. The sulfide layer was formed by reacting clean Ge substrates in (NH{sub 4}){sub 2}S solutions of various concentrations at 80{sup o}C. For each treatment, a sulfide layer containing approximately two to three monolayers (ML) of S was formed on the surface, and an ordered structure was found at the interface that contained approximately 0.4 ML of S. Our results suggest the rapid formation of a glassy GeS{sub x} layer containing 1.5-2.5 ML S residing atop a partially ordered interfacial layer of bridge-bonded S. The passivating reaction appears to be self-limited to 2-3 ML at this reaction temperature.

  3. In situ analysis of multispecies biofilm formation on customized titanium surfaces.

    Science.gov (United States)

    Fröjd, V; Chávez de Paz, L; Andersson, M; Wennerberg, A; Davies, J R; Svensäter, G

    2011-08-01

    Many studies to identify surfaces that enhance the incorporation of dental implants into bone and soft-tissue have been undertaken previously. However, to succeed in the clinical situation, an implant surface must not support development of microbial biofilms with a pathogenic potential. As a first step in investigating this, we used two-species and three-species biofilm models with 16S ribosomal RNA fluorescence in situ hybridization and confocal laser scanning microscopy to examine the effect of surface characteristics on biofilm formation by species that can colonize titanium implants in vivo: Streptococcus sanguinis, Actinomyces naeslundii and Lactobacillus salivarius. Surfaces blasted with Al(2) O(3) (S(a) = 1.0-2.0 μm) showed a seven-fold higher bacterial adhesion after 2 h than turned surfaces (S(a) = 0.18 μm) whereas porous surfaces, generated by anodic oxidation (S(a) = 0.4 μm), showed four-fold greater adhesion than turned surfaces. Hence, increased roughness promoted adhesion, most likely through protection of bacteria from shear forces. Chemical modification of the blasted and oxidized surfaces by incorporation of Ca(2+) ions reduced adhesion compared with the corresponding non-modified surfaces. After 14 h, biofilm growth occurred in the three-species model but not in the two-species consortium (containing S. sanguinis and A. naeslundii only). The biofilm biovolume on all surfaces was similar, suggesting that the influence of surface characteristics on adhesion was compensated for by biofilm development. © 2011 John Wiley & Sons A/S.

  4. In Situ Laser Coating of Calcium Phosphate on TC4 Surface for Enhancing Bioactivity

    Institute of Scientific and Technical Information of China (English)

    DENG Chi; WANG Yong; ZHANG Ya-ping; GAO Jia-cheng

    2007-01-01

    Titanium alloy has been a successful implant material owing to its excellent ratio of strength to weight,toughness, and bio-inert oxide surface. Significant progress has been made in improving the bioactivity of titanium alloy by coating its oxide surface with calcium phosphates. In the present study, in situ coating was reported on Ti6Al4V(TC4) surface with calcium phosphate (Ca-P) bioceramics synthesized and synchronously cladded by laser beam. This coating was grown by first preplacing directly the raw powders, which contain 80% of CaHPO4 ·2H2O, 20% of CaCO3, and dram of rare earth (RE), on the TC4 surfaces, and then exposing the surfaces to the laser beam with a power density of 12. 73-15.27 MW · m-2 and a scanning velocity of 10. 5 m/s. The resultant coating was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis and Different-thermal Scanning (TG-DSC), and Energy Dispersive X-ray Detection (EDX). The results show that these laser ceramics include hydroxyapatite (HA), tricalcium phosphate (TCP), Ca2P2O7, and other Ca-P phases, and the interface between the coating and the TC4 substrate has tighter fixation, in which the chemical bonding is approved. These laser hybrid coatings are useful in enhancing the bioactivity of titanium alloy surfaces.

  5. In situ emulsion cationic polymerization of isoprene onto the surface of graphite oxide sheets

    Science.gov (United States)

    Pazat, Alice; Beyou, Emmanuel; Barrès, Claire; Bruno, Florence; Janin, Claude

    2017-02-01

    Grafting of polymers onto graphite oxide sheets (GO) has been widely studied in recent years due to the numerous applications of GO-based composites. Herein, polyisoprene (PI) chains were anchored on the surface of GO by in situ cationic polymerization using a "grafting through" approach with allyltrimethoxysilane-modified GO (GO-ATMS). First, the functionalization of GO sheets through the hydrolysis-condensation of allyltrimethoxysilane (ATMS) molecules was qualitatively evidenced by infra-red spectroscopy and X-ray photoelectron spectrometry and a weight content of 4% grafted ATMS was calculated from thermogravimetric analysis. Then, isoprene was in situ polymerized through a one-pot cationic mechanism by using a highly water-dispersible Lewis acid surfactant combined catalyst. For comparison, it was shown that the cationic polymerization of isoprene in presence of un-functionalized GO sheets led to a polyisoprene weight content on the solid filler divided by 3 compared to GO-ATMS. Finally, the compounding of the modified GO/PI composites was performed at a processing temperature of 80 °C with 2 phr and 15 phr loadings and it was shown a decrease of the air permeability coefficient of 27% for the vulcanizates with 15 phr loading.

  6. In-situ surface sensitive X-ray investigations of quench condensed thin metal films

    Energy Technology Data Exchange (ETDEWEB)

    Markert, Christian; Luetzenkirchen-Hecht, Dirk; Gertz, Sascha; Frahm, Ronald [Bergische Universitaet Wuppertal, Fachbereich C / Abteilung Physik, Gaussstrasse 20, 42119 Wuppertal (Germany)

    2007-07-01

    We report of ultrahigh vacuum (UHV) experiments on ultra thin Au, Bi and Pb films (thickness less than 10 nm) deposited on atomically flat float-glass substrates which are held at cryogenic temperatures down to 10 K. For deposition temperatures below 100 K the formation of highly disordered or even amorphous metal films can be expected, because thermally activated diffusion of the ad atoms should be inhibited. An UHV chamber was constructed which is suited for grazing incidence X-ray experiments during the quench condensation of the metal films. Various X-ray methods were used for the in-situ investigation of the films growth and their structural evolution with the thickness and an subsequent annealing process. EXAFS (Extended X-ray Absorption Fine Structure) in reflection is used to study the local structure of the films. Furthermore specular and non-specular X-ray reflectivity measurements were performed to get information about the films density and surface roughness parameters (correlation length, hurst parameter etc.). In addition in situ resistivity measurements which are sensitive towards changes of the films microstructure were performed in parallel to the X-ray experiments.

  7. An Insertable Passive LC Pressure Sensor Based on an Alumina Ceramic for In Situ Pressure Sensing in High-Temperature Environments.

    Science.gov (United States)

    Xiong, Jijun; Li, Chen; Jia, Pinggang; Chen, Xiaoyong; Zhang, Wendong; Liu, Jun; Xue, Chenyang; Tan, Qiulin

    2015-08-31

    Pressure measurements in high-temperature applications, including compressors, turbines, and others, have become increasingly critical. This paper proposes an implantable passive LC pressure sensor based on an alumina ceramic material for in situ pressure sensing in high-temperature environments. The inductance and capacitance elements of the sensor were designed independently and separated by a thermally insulating material, which is conducive to reducing the influence of the temperature on the inductance element and improving the quality factor of the sensor. In addition, the sensor was fabricated using thick film integrated technology from high-temperature materials that ensure stable operation of the sensor in high-temperature environments. Experimental results showed that the sensor accurately monitored pressures from 0 bar to 2 bar at temperatures up to 800 °C. The sensitivity, linearity, repeatability error, and hysteretic error of the sensor were 0.225 MHz/bar, 95.3%, 5.5%, and 6.2%, respectively.

  8. Degradation of VX surrogate profenofos on surfaces via in situ photo-oxidation.

    Science.gov (United States)

    Petrick, Lauren M; Sabach, Sara; Dubowski, Yael

    2013-08-06

    Surface degradation of profenofos (PF), a VX nerve gas surrogate, was investigated using in situ photo-oxidation that combines simple instrumentation and ambient gases (O2 and H2O) as a function of exposure conditions ([O3], [OH], UV light λ = 185 and/or 254 nm, relative humidity) and PF film surface density (0.38-3.8 g m(-2)). PF film 0.38 g m(-2) fully degraded after 60 min of exposure to both 254 and 185 nm UV light in humidified air and high ozone. The observed pseudo-first-order surface reaction rate constant (kobs = 0.075 ± 0.004 min(-1)) and calculated hydroxyl concentration near the film surface ([OH]g = (9 ± 2) × 10(7) molecules cm(-3)) were used to determine the second-order rate constant for heterogeneous reaction of PF and OH (k(OH)PF = (5 ± 1) × 10(-12) cm(3) molec(-1) s(-1)). PF degradation in the absence of 185 nm light or without humidity was lower (70% or 90% degradation, respectively). With denser PF films ranging from 2.3 to 3.8 g m(-2), only 80% degradation was achieved until the PF droplet was redissolved in acetonitrile which allowed >95% PF degradation. Surface product analysis indicated limited formation of the nontoxic phosphoric acid ester but the formation of nonvolatile chemicals with increased hydrophilicity and addition of OH.

  9. A miniature laser ablation mass spectrometer for quantitative in situ chemical composition investigation of lunar surface

    Science.gov (United States)

    Brigitte Neuland, Maike; Grimaudo, Valentine; Mezger, Klaus; Moreno-García, Pavel; Riedo, Andreas; Tulej, Marek; Wurz, Peter

    2016-04-01

    The chemical composition of planetary bodies, moons, comets and asteroids is a key to understand their origin and evolution [Wurz,2009]. Measurements of the elemental and isotopic composition of rocks yield information about the formation of the planetary body, its evolution and following processes shaping the planetary surface. From the elemental composition, conclusions about modal mineralogy and petrology can be drawn. Isotope ratios are a sensitive indicator for past events on the planetary body and yield information about origin and transformation of the matter, back to events that occurred in the early solar system. Finally, measurements of radiogenic isotopes make it possible to carry out dating analyses. All these topics, particularly in situ dating analyses, quantitative elemental and highly accurate isotopic composition measurements, are top priority scientific questions for future lunar missions. An instrument for precise measurements of chemical composition will be a key element in scientific payloads of future landers or rovers on lunar surface. We present a miniature laser ablation mass spectrometer (LMS) designed for in situ research in planetary and space science and optimised for measurements of the chemical composition of rocks and soils on a planetary surface. By means of measurements of standard reference materials we demonstrate that LMS is a suitable instrument for in situ measurements of elemental and isotopic composition with high precision and accuracy. Measurements of soil standards are used to confirm known sensitivity coefficients of the instrument and to prove the power of LMS for quantitative elemental analyses [Neuland,2016]. For demonstration of the capability of LMS to measure the chemical composition of extraterrestrial material we use a sample of Allende meteorite [Neuland,2014]. Investigations of layered samples confirm the high spatial resolution in vertical direction of LMS [Grimaudo,2015], which allows in situ studying of past

  10. Novel application of satellite and in-situ measurements to map surface-level NO2 in the Great Lakes region

    Directory of Open Access Journals (Sweden)

    C. Mihele

    2011-11-01

    Full Text Available Ozone Monitoring Instrument (OMI tropospheric NO2 vertical column density data were used in conjunction with in-situ NO2 concentrations collected by permanently installed monitoring stations to infer 24 h surface-level NO2 concentrations at 0.1° (~11 km resolution. The region examined included rural and suburban areas, and the highly industrialised area of Windsor, Ontario, which is situated directly across the US-Canada border from Detroit, MI. Photolytic NO2 monitors were collocated with standard NO2 monitors to provide qualitative data regarding NOz interference during the campaign. The accuracy of the OMI-inferred concentrations was tested using two-week integrative NO2 measurements collected with passive monitors at 18 locations, approximating a 15 km grid across the region, for 7 consecutive two-week periods. When compared with these passive results, satellite-inferred concentrations showed an 18% positive bias. The correlation of the passive monitor and OMI-inferred concentrations (R=0.69, n=115 was stronger than that for the passive monitor concentrations and OMI column densities (R=0.52, indicating that using a sparse network of monitoring sites to estimate concentrations improves the direct utility of the OMI observations. OMI-inferred concentrations were then calculated for four years to show an overall declining trend in surface NO2 concentrations in the region. Additionally, by separating OMI-inferred surface concentrations by wind direction, clear patterns in emissions and affected down-wind regions, in particular around the US-Canada border, were revealed.

  11. In-situ observations of catalyst dynamics during surface-bound carbon nanotube nucleation

    DEFF Research Database (Denmark)

    Hofmann, S; Sharma, R; Du, G;

    2007-01-01

    We present atomic-scale, video-rate environmental transmission electron microscopy and in situ time-resolved X-ray photoelectron spectroscopy of surface-bound catalytic chemical vapor deposition of single-walled carbon nanotubes and nanofibers. We observe that transition metal catalyst...... nanoparticles on SiOx support show crystalline lattice fringe contrast and high deformability before and during nanotube formation. A single-walled carbon nanotube nucleates by lift-off of a carbon cap. Cap stabilization and nanotube growth involve the dynamic reshaping of the catalyst nanocrystal itself....... For a carbon nanofiber, the graphene layer stacking is determined by the successive elongation and contraction of the catalyst nanoparticle at its tip....

  12. Peripheral ameloblastoma in-situ: an evidential fact of surface epithelium origin.

    Science.gov (United States)

    Ide, Fumio; Mishima, Kenji; Miyazaki, Yuji; Saito, Ichiro; Kusama, Kaoru

    2009-11-01

    The proposed origin from the adult gingival epithelium for peripheral ameloblastoma is difficult to prove and still remains unresolved. This report details a small fibrous polyp on the maxillary edentulous ridge of a 73-year-old woman, in which the basal layer of covering squamous epithelium dipped down toward the lamina propria over a wide area. Basal cells of the downgrowth were ameloblastic in type, and bulbous parts assumed an appearance of the bud-shaped enamel organ. Multiple sectioning failed to detect any epithelial nests in the submucosa. In addition to the morphologic overlap, early ameloblastoma epithelia shared antigenic properties with tumor cells of representative control examples of peripheral ameloblastoma. This is the first description of an in situ lesion of peripheral ameloblastoma, to our knowledge, and its multifocal ameloblastoma changes can be accepted as a direct proof of origin from the surface epithelium.

  13. Magnetization of individual yeast cells by in situ formation of iron oxide on cell surfaces

    Science.gov (United States)

    Choi, Jinsu; Lee, Hojae; Choi, Insung S.; Yang, Sung Ho

    2017-09-01

    Magnetic functionalization of living cells has intensively been investigated with the aim of various bioapplications such as selective separation, targeting, and localization of the cells by using an external magnetic field. However, the magnetism has not been introduced to individual living cells through the in situ chemical reactions because of harsh conditions required for synthesis of magnetic materials. In this work, magnetic iron oxide was formed on the surface of living cells by optimizing reactions conditions to be mild sufficiently enough to sustain cell viability. Specifically, the reactive LbL strategy led to formation of magnetically responsive yeast cells with iron oxide shells. This facile and direct post-magnetization method would be a useful tool for remote manipulation of living cells with magnetic interactions, which is an important technique for the integration of cell-based circuits and the isolation of cell in microfluidic devices.

  14. Pesticide monitoring in surface water and groundwater using passive samplers

    Science.gov (United States)

    Kodes, V.; Grabic, R.

    2009-04-01

    Passive samplers as screening devices have been used within a czech national water quality monitoring network since 2002 (SPMD and DGT samplers for non polar substances and metals). The passive sampler monitoring of surface water was extended to polar substances, in 2005. Pesticide and pharmaceutical POCIS samplers have been exposed in surface water at 21 locations and analysed for polar pesticides, perfluorinated compounds, personal care products and pharmaceuticals. Pesticide POCIS samplers in groundwater were exposed at 5 locations and analysed for polar pesticides. The following active substances of plant protection products were analyzed in surface water and groundwater using LC/MS/MS: 2,4,5-T, 2,4-D, Acetochlor, Alachlor, Atrazine, Atrazine_desethyl, Azoxystrobin, Bentazone, Bromacil, Bromoxynil, Carbofuran, Clopyralid, Cyanazin, Desmetryn, Diazinon, Dicamba, Dichlobenil, Dichlorprop, Dimethoat, Diuron, Ethofumesate, Fenarimol, Fenhexamid, Fipronil, Fluazifop-p-butyl, Hexazinone, Chlorbromuron, Chlorotoluron, Imazethapyr, Isoproturon, Kresoxim-methyl, Linuron, MCPA, MCPP, Metalaxyl, Metamitron, Methabenzthiazuron, Methamidophos, Methidathion, Metobromuron, Metolachlor, Metoxuron, Metribuzin, Monolinuron, Nicosulfuron, Phorate, Phosalone, Phosphamidon, Prometryn, Propiconazole, Propyzamide, Pyridate, Rimsulfuron, Simazine, Tebuconazole, Terbuthylazine, Terbutryn, Thifensulfuron-methyl, Thiophanate-methyl and Tri-allate. The POCIS samplers performed very well being able to provide better picture than grab samples. The results show that polar pesticides and also perfluorinated compounds, personal care products and pharmaceuticals as well occur in hydrosphere of the Czech republic. Acknowledgment: Authors acknowledge the financial support of grant No. 2B06095 by the Ministry of Education, Youth and Sports.

  15. Surface heterogeneity, measurement uncertainty, and the implications for using in-situ observations for model validation studies

    Science.gov (United States)

    In-situ observations are critical for developing, calibrating, and validating the remote sensing-based models used to estimate and predict evapotranspiration (ET) along with the other components of the surface energy budget. Field measurements of the surface energy fluxes are collected using a varie...

  16. In-situ soil composition and moisture measurement by surface neutron activation analysis

    Science.gov (United States)

    Waring, C.; Smith, C.; Marks, A.

    2009-04-01

    Neutron activation analysis is widely known as a laboratory technique dependent upon a nuclear reactor to provide the neutron flux and capable of precise elemental analysis. Less well known in-situ geochemical analysis is possible with isotopic (252Cf & 241Am) or compact accelerator (D-T, D-D fusion reaction) neutron sources. Prompt gamma neutron activation analysis (PGNAA) geophysical borehole logging has been applied to mining issues for >15 years (CSIRO) using isotopic neutron sources and more recently to environmental and hydro-geological applications by ANSTO. Similarly, sophisticated geophysical borehole logging equipment based on inelastic neutron scattering (INS) has been applied in the oil and gas industry by large oilfield services companies to measure oil saturation indices (carbon/oxygen) using accelerator neutron sources. Recent advances in scintillation detector spectral performance has enabled improved precision and detection limits for elements likely to be present in soil profiles (H, Si, Al, Fe, Cl) and possible detection of many minor to trace elements if sufficiently abundant (Na, K, Mg, Ca, S, N, + ). To measure carbon an accelerator neutron source is required to provide fast neutrons above 4.8 MeV. CSIRO and ANSTO propose building a soil geochemical analysis system based on experience gained from building and applying PGNA borehole logging equipment. A soil geochemical analysis system could effectively map the 2D geochemical composition of the top 50cm of soil by dragging the 1D logging equipment across the ground surface. Substituting an isotopic neutron source for a D-T accelerator neutron source would enable the additional measurement of elemental carbon. Many potential ambiguities with other geophysical proxies for soil moisture may be resolved by direct geochemical measurement of H. Many other applications may be possible including time series in-situ measurements of soil moisture for differential drainage, hydrology, land surface

  17. Synthesis in situ of gold nanoparticles by a dialkynyl Fischer carbene complex anchored to glass surfaces

    Science.gov (United States)

    Bertolino, María Candelaria; Granados, Alejandro Manuel

    2016-10-01

    In this work we present a detailed study of classic reactions such as "click reaction" and nucleophilic substitution reaction but on glass solid surface (slides). We used different reactive center of a dialkynylalcoxy Fischer carbene complex of tungsten(0) to be anchored to modified glass surface with amine, to obtain aminocarbene, and azide terminal groups. These cycloaddition reaction showed regioselectivity to internal triple bond of dialkynyl Fischer carbene complex without Cu(I) as catalyst. Anyway the carbene anchored was able to act as a reducing agent to produce in situ very stable gold nanoparticles fixed on surface. We showed the characterization of modified glasses by contact angle measurements and XPS. Synthesized nanoparticles were characterized by SEM, XPS, EDS and UV-vis. The modified glasses showed an important enhancement Raman-SERS. This simple, fast and robust method to create a polifunctional and hybrid surfaces can be valuable in a wide range of applications such as Raman-SERS substrates and other optical fields.

  18. Evaluation of Select Surface Processing Techniques for In Situ Application During the Additive Manufacturing Build Process

    Science.gov (United States)

    Book, Todd A.; Sangid, Michael D.

    2016-07-01

    Although additive manufacturing offers numerous performance advantages for different applications, it is not being used for critical applications due to uncertainties in structural integrity as a result of innate process variability and defects. To minimize uncertainty, the current approach relies on the concurrent utilization of process monitoring, post-processing, and non-destructive inspection in addition to an extensive material qualification process. This paper examines an alternative approach by evaluating the application of select surface process techniques, to include sliding severe plastic deformation (SPD) and fine particle shot peening, on direct metal laser sintering-produced AlSi10Mg materials. Each surface processing technique is compared to baseline as-built and post-processed samples as a proof of concept for surface enhancement. Initial results pairing sliding SPD with the manufacture's recommended thermal stress relief cycle demonstrated uniform recrystallization of the microstructure, resulting in a more homogeneous distribution of strain among the microstructure than as-built or post-processed conditions. This result demonstrates the potential for the in situ application of various surface processing techniques during the layerwise direct metal laser sintering build process.

  19. Long Alkyl Chain Organophosphorus Coupling Agents for in Situ Surface Functionalization by Reactive Milling

    Directory of Open Access Journals (Sweden)

    Annika Betke

    2014-08-01

    Full Text Available Innovative synthetic approaches should be simple and environmentally friendly. Here, we present the surface modification of inorganic submicrometer particles with long alkyl chain organophosphorus coupling agents without the need of a solvent, which makes the technique environmentally friendly. In addition, it is of great benefit to realize two goals in one step: size reduction and, simultaneously, surface functionalization. A top-down approach for the synthesis of metal oxide particles with in situ surface functionalization is used to modify titania with long alkyl chain organophosphorus coupling agents. A high energy planetary ball mill was used to perform reactive milling using titania as inorganic pigment and long alkyl chain organophosphorus coupling agents like dodecyl and octadecyl phosphonic acid. The final products were characterized by IR, NMR and X-ray fluorescence spectroscopy, thermal and elemental analysis as well as by X-ray powder diffraction and scanning electron microscopy. The process entailed a tribochemical phase transformation from the starting material anatase to a high-pressure modification of titania and the thermodynamically more stable rutile depending on the process parameters. Furthermore, the particles show sizes between 100 nm and 300 nm and a degree of surface coverage up to 0.8 mmol phosphonate per gram.

  20. Characterization of different surface passivation routes applied to a planar HPGe detector

    Energy Technology Data Exchange (ETDEWEB)

    Maggioni, G.; Gelain, M.; Carturan, S. [University of Padova, Department of Physics and Astronomy ' ' G. Galilei' ' , Padova (Italy); Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Legnaro (Italy); Napoli, D.R. [Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Legnaro (Italy); Eberth, J. [Universitaet zu Koeln, Institut fuer Kernphysik, Koeln (Germany); Grimaldi, M.G.; Tati, S. [University of Catania, Department of Physics and Astronomy, Catania (Italy)

    2015-11-15

    The effects of different passivation methods applied to the same planar high-purity germanium gamma radiation detector have been studied. By means of the scanning with a low-energy collimated gamma source, it has been found that the surface passivation gives rise to a dead layer below the intrinsic Ge surface, whose thickness and distribution are strongly dependent on the passivation type. Measured bulk detector properties like the peak-to-Compton ratio and efficiency have shown a dependence on the passivation and an influence of the passivation type on the depletion voltage, whilst the optimal energy resolution has been the same for all the passivations. (orig.)

  1. Enhancing steel properties through in situ formation of ultrahard ceramic surface.

    Science.gov (United States)

    Pahlevani, Farshid; Kumar, Rahul; Gorjizadeh, Narjes; Hossain, Rumana; Cholake, Sagar T; Privat, Karen; Sahajwalla, Veena

    2016-12-08

    Abrasion and corrosion resistant steel has attracted considerable interest for industrial application as a means of minimising the costs associated with product/component failures and/or short replacement cycles. These classes of steels contain alloying elements that increase their resistance to abrasion and corrosion. Their benefits, however, currently come at a potentially prohibitive cost; such high performance steel products are both more technically challenging and more expensive to produce. Although these methods have proven effective in improving the performance of more expensive, high-grade steel components, they are not economically viable for relatively low cost steel products. New options are needed. In this study, a complex industrial waste stream has been transformed in situ via precisely controlled high temperature reactions to produce an ultrahard ceramic surface on steel. This innovative ultrahard ceramic surface increases both the hardness and compressive strength of the steel. Furthermore, by modifying the composition of the waste input and the processing parameters, the ceramic surface can be effectively customised to match the intended application of the steel. This economical new approach marries industry demands for more cost-effective, durable steel products with global imperatives to address resource depletion and environmental degradation through the recovery of resources from waste.

  2. Enhancing steel properties through in situ formation of ultrahard ceramic surface

    Science.gov (United States)

    Pahlevani, Farshid; Kumar, Rahul; Gorjizadeh, Narjes; Hossain, Rumana; Cholake, Sagar T.; Privat, Karen; Sahajwalla, Veena

    2016-12-01

    Abrasion and corrosion resistant steel has attracted considerable interest for industrial application as a means of minimising the costs associated with product/component failures and/or short replacement cycles. These classes of steels contain alloying elements that increase their resistance to abrasion and corrosion. Their benefits, however, currently come at a potentially prohibitive cost; such high performance steel products are both more technically challenging and more expensive to produce. Although these methods have proven effective in improving the performance of more expensive, high-grade steel components, they are not economically viable for relatively low cost steel products. New options are needed. In this study, a complex industrial waste stream has been transformed in situ via precisely controlled high temperature reactions to produce an ultrahard ceramic surface on steel. This innovative ultrahard ceramic surface increases both the hardness and compressive strength of the steel. Furthermore, by modifying the composition of the waste input and the processing parameters, the ceramic surface can be effectively customised to match the intended application of the steel. This economical new approach marries industry demands for more cost-effective, durable steel products with global imperatives to address resource depletion and environmental degradation through the recovery of resources from waste.

  3. Surface scattering and giant magnetoresistance: In-situ resistance and magnetoresistance experiments

    Science.gov (United States)

    Bailey, William Evans

    Surface scattering, particularly the enhancement of "specular" scattering, is widely believed to hold the key to yet-unattained levels of spin-valve GMR. We have developed a novel technique to measure surface scattering, the in-situ magnetoconductance measurement. By measuring resistance and GMR in real time during deposition, in ultrahigh vacuum, and in the Van der Pauw configuration, we may determine the effect on scattering of various overlayers as they are created. We have applied this technique to study claims that the specularity may be modified through deposition of metal overlayers. In conjunction with first-principles based calculations of film conductance and detailed characterization of thickness-dependent film microstructure, we have determined that the surface specularity is not modified during overlayer deposition. Effects previously attributed to specularity modulations are well interpreted through scattering mechanisms intrinsic to the system. We have also examined the dependence of GMR on bulk microstructure, as characterized ex-situ. We find that crystallographic disorder tends to decrease spin-valve GMR. This is shown experimentally through depositions of several series of samples, characterization of the relevant defects, and correlation to magnetotransport measurements. We have formed the films by sputtering and UHV ion beam deposition. Experimental techniques used to characterize microstructure are high-resolution cross-sectional transmission electron microscopy (HR-xTEM), x-ray diffraction (XRD), 59Co nuclear magnetic resonance (NMR), contributed by Ewa Jedryka at the Polish Institute of Physics in Warsaw.

  4. Mechanical Properties and Tribological Behavior of In Situ NbC/Fe Surface Composites

    Science.gov (United States)

    Cai, Xiaolong; Zhong, Lisheng; Xu, Yunhua

    2017-01-01

    The mechanical properties and tribological behavior of the niobium carbide (NbC)-reinforced gray cast iron surface composites prepared by in situ synthesis have been investigated. Composites are comprised of a thin compound layer and followed by a deep diffusion zone on the surface of gray cast iron. The graded distributions of the hardness and elastic modulus along the depth direction of the cross section of composites form in the ranges of 6.5-20.1 and 159.3-411.2 GPa, respectively. Meanwhile, dry wear tests for composites were implemented on pin-on-disk equipment at sliding speed of 14.7 × 10-2 m/s and under 5 or 20 N, respectively. The result indicates that tribological performances of composites are considerably dependent on the volume fraction and the grain size of the NbC as well as the mechanical properties of the matrices in different areas. The surface compound layer presents the lowest coefficient of friction and wear rate, and exhibits the highest wear resistance, in comparison with diffusion zone and substrate. Furthermore, the worn morphologies observed reveal the dominant wear mechanism is abrasive wear feature in compound layer and diffusion zone.

  5. Enhancing steel properties through in situ formation of ultrahard ceramic surface

    Science.gov (United States)

    Pahlevani, Farshid; Kumar, Rahul; Gorjizadeh, Narjes; Hossain, Rumana; Cholake, Sagar T; Privat, Karen; Sahajwalla, Veena

    2016-01-01

    Abrasion and corrosion resistant steel has attracted considerable interest for industrial application as a means of minimising the costs associated with product/component failures and/or short replacement cycles. These classes of steels contain alloying elements that increase their resistance to abrasion and corrosion. Their benefits, however, currently come at a potentially prohibitive cost; such high performance steel products are both more technically challenging and more expensive to produce. Although these methods have proven effective in improving the performance of more expensive, high-grade steel components, they are not economically viable for relatively low cost steel products. New options are needed. In this study, a complex industrial waste stream has been transformed in situ via precisely controlled high temperature reactions to produce an ultrahard ceramic surface on steel. This innovative ultrahard ceramic surface increases both the hardness and compressive strength of the steel. Furthermore, by modifying the composition of the waste input and the processing parameters, the ceramic surface can be effectively customised to match the intended application of the steel. This economical new approach marries industry demands for more cost-effective, durable steel products with global imperatives to address resource depletion and environmental degradation through the recovery of resources from waste. PMID:27929096

  6. Surface Characterization and in situ Protein Adsorption Studies on Carbene-Modified Polymers.

    Science.gov (United States)

    Nelson, Geoffrey W; Parker, Emily M; Singh, Kulveer; Blanford, Christopher F; Moloney, Mark G; Foord, John S

    2015-10-13

    Polystyrene thin films were functionalized using a facile two-step chemical protocol involving carbene insertion followed by azo-coupling, permitting the introduction of a range of chemical functional groups, including aniline, hexyl, amine, carboxyl, phenyl, phosphonate diester, and ethylene glycol. X-ray photoelectron spectroscopy (XPS) confirmed the success of the two-step chemical modification with a grafting density of at least 1/10th of the typical loading density (10(14)-10(15)) of a self-assembled monolayer (SAM). In situ, real-time quartz crystal microbalance with dissipation (QCM-D) studies show that the dynamics of binding of bovine serum albumin (BSA) are different at each modified surface. Mass, viscoelastic, and kinetic data were analyzed, and compared to cheminformatic descriptors (i.e., c log P, polar surface area) typically used for drug discovery. Results show that functionalities may either resist or adsorb BSA, and uniquely influence its adsorption dynamics. It is concluded that carbene-based surface modification can usefully influence BSA binding dynamics in a manner consistent with, and more robust than, traditional systems based on SAM chemistry.

  7. Mechanical Properties and Tribological Behavior of In Situ NbC/Fe Surface Composites

    Science.gov (United States)

    Cai, Xiaolong; Zhong, Lisheng; Xu, Yunhua

    2016-11-01

    The mechanical properties and tribological behavior of the niobium carbide (NbC)-reinforced gray cast iron surface composites prepared by in situ synthesis have been investigated. Composites are comprised of a thin compound layer and followed by a deep diffusion zone on the surface of gray cast iron. The graded distributions of the hardness and elastic modulus along the depth direction of the cross section of composites form in the ranges of 6.5-20.1 and 159.3-411.2 GPa, respectively. Meanwhile, dry wear tests for composites were implemented on pin-on-disk equipment at sliding speed of 14.7 × 10-2 m/s and under 5 or 20 N, respectively. The result indicates that tribological performances of composites are considerably dependent on the volume fraction and the grain size of the NbC as well as the mechanical properties of the matrices in different areas. The surface compound layer presents the lowest coefficient of friction and wear rate, and exhibits the highest wear resistance, in comparison with diffusion zone and substrate. Furthermore, the worn morphologies observed reveal the dominant wear mechanism is abrasive wear feature in compound layer and diffusion zone.

  8. Quantifying bulk and surface recombination processes in nanostructured water splitting photocatalysts via in situ ultrafast spectroscopy.

    Science.gov (United States)

    Appavoo, Kannatassen; Liu, Mingzhao; Black, Charles T; Sfeir, Matthew Y

    2015-02-11

    A quantitative description of recombination processes in nanostructured semiconductor photocatalysts-one that distinguishes between bulk (charge transport) and surface (chemical reaction) losses-is critical for advancing solar-to-fuel technologies. Here we present an in situ experimental framework that determines the bias-dependent quantum yield for ultrafast carrier transport to the reactive interface. This is achieved by simultaneously measuring the electrical characteristics and the subpicosecond charge dynamics of a heterostructured photoanode in a working photoelectrochemical cell. Together with direct measurements of the overall incident-photon-to-current efficiency, we illustrate how subtle structural modifications that are not perceivable by conventional X-ray diffraction can drastically affect the overall photocatalytic quantum yield. We reveal how charge carrier recombination losses occurring on ultrafast time scales can limit the overall efficiency even in nanostructures with dimensions smaller than the minority carrier diffusion length. This is particularly true for materials with high carrier concentration, where losses as high as 37% are observed. Our methodology provides a means of evaluating the efficacy of multifunctional designs where high overall efficiency is achieved by maximizing surface transport yield to near unity and utilizing surface layers with enhanced activity.

  9. Fourier transform infrared phase-modulated ellipsometry for in situ diagnostics of plasma-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Shirafuji, T [International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Motomura, H [Department of Electronics, Kyoto University, Nishikyo-ku, Katsura 615-8510 (Japan); Tachibana, K [Department of Electronics, Kyoto University, Nishikyo-ku, Katsura 615-8510 (Japan)

    2004-03-21

    Applicability of Fourier transform infrared (FTIR) spectroscopy to an in situ diagnostics tool of plasma-surface interactions is described. After a brief review of conventional reflection absorption spectroscopy (RAS) and phase-modulated RAS (PMRAS), our FTIR phase-modulated spectroscopic ellipsometry (PMSE) is described in detail. The FTIR PMSE is constructed by insertion of a grid polarizer as an analyser in front of an infrared detector in addition to the conventional set-up of PMRAS. This simple change brings about a higher sensitivity than that of conventional PMRAS, which enables us to detect chemical species generated on (or removed from) the top surface layer during plasma processing. This feature is demonstrated by the fact that our FTIR PMSE can be applied to surface diagnostics during reactive ion etching processes such as for Si, SiO{sub 2}/Si, SiO{sub 2}/Si{sub 3}N{sub 4}, SiO{sub 2}/photo-resist and low-dielectric-constant films. (topical review)

  10. In Situ Generation of Chlorine Dioxide for Surface Decontamination of Produce.

    Science.gov (United States)

    Hwang, Cheng-An; Huang, Lihan; Wu, Vivian Chi-Hua

    2017-04-01

    Fresh fruits and vegetables are frequently contaminated with bacterial pathogens and implicated in foodborne illnesses. The objective of this study was to develop a unique surface decontamination method for produce using sodium chlorite and an acid in a sequential treatment. The surfaces of cantaloupe rinds, peels of cucumbers, stem scars of grape tomatoes, and leaves of baby spinach were inoculated with Salmonella or Listeria monocytogenes at 5 to 6 log CFU/g, submerged in 1.6 to 4% sodium chlorite solutions for 10 or 30 min, dried for 20 min, and then soaked in 6 mM hydrogen chloride (HCl) for 10 or 30 min and dried for 20 min. Control samples were treated with deionized water, sodium chlorite, HCl, or a premixed solution of sodium chlorite and HCl for comparison. The control treatments reduced the levels of both pathogens on the samples by only 0.3 to 2.9 log CFU/g, whereas the sequential treatment caused significantly higher reductions (P < 0.05) of 5.1 to 5.6 log CFU/g, effectively eliminating the inoculated pathogens. The more effective decontamination resulting from the sequential treatment was attributed to the in situ formation of chlorine dioxide within the plant tissues under the surface by the reaction between sodium chlorite absorbed by the produce and HCl. These results suggest that the sequential use of sodium chlorite and acid is a potentially effective treatment for elimination of foodborne pathogens on produce.

  11. A Facile in Situ and UV Printing Process for Bioinspired Self-Cleaning Surfaces

    Directory of Open Access Journals (Sweden)

    Marina A. González Lazo

    2016-08-01

    Full Text Available A facile in situ and UV printing process was demonstrated to create self-cleaning synthetic replica of natural petals and leaves. The process relied on the spontaneous migration of a fluorinated acrylate surfactant (PFUA within a low-shrinkage acrylated hyperbranched polymer (HBP and its chemical immobilization at the polymer-air interface. Dilute concentrations of 1 wt. % PFUA saturated the polymer-air interface within 30 min, leading to a ten-fold increase of fluorine concentration at the surface compared with the initial bulk concentration and a water contact angle (WCA of 108°. A 200 ms flash of UV light was used to chemically crosslink the PFUA at the HBP surface prior to UV printing with a polydimethylsiloxane (PDMS negative template of red and yellow rose petals and lotus leaves. This flash immobilization hindered the reverse migration of PFUA within the bulk HBP upon contacting the PDMS template, and enabled to produce texturized surfaces with WCA well above 108°. The synthetic red rose petal was hydrophobic (WCA of 125° and exhibited the adhesive petal effect. It was not superhydrophobic due to insufficient concentration of fluorine at its surface, a result of the very large increase of the surface of the printed texture. The synthetic yellow rose petal was quasi-superhydrophobic (WCA of 143°, roll-off angle of 10° and its self-cleaning ability was not good also due to lack of fluorine. The synthetic lotus leaf did not accurately replicate the intricate nanotubular crystal structures of the plant. In spite of this, the fluorine concentration at the surface was high enough and the leaf was superhydrophobic (WCA of 151°, roll-off angle below 5° and also featured self-cleaning properties.

  12. Surface Temperature Trends in the Arctic and the Antarctic from AVHRR and In Situ Data

    Science.gov (United States)

    Perez, G. J. P.; Comiso, J. C.

    2015-12-01

    The earliest signals of a climate change are expected to be observed in the polar regions in part because of the high reflectively of snow and ice. Because of general inaccessibility, there is a paucity of in situ data and hence the need to use satellite data to observe the large-scale variability and trends in surface temperature in the two regions. The sensor with the longest satellite record on temperature has been the NOAA/Advanced Very High Resolution Radiometer (AVHRR) that has provided continuous thermal infrared data for more than 33 years. The results of analysis of the data show that there is indeed a strong signal coming from the Arctic with the trend in surface temperature (for the region > 64°N) being 0.6°C per decade which is about 3 times the global trend of 0.2°C per decade for the same period. It appeared surprising when the results from a similar region (> 64 °S) in the Antarctic show a much lower trend and comparable to the global trend. The primary source of error in the temperature data is cloud masking associated with the similar signatures of clouds and snow/ice covered surfaces. However, the derived AVHRR data show good consistency with in situ data with standard deviation less than 1°C. The AVHRR time series has also been compared and showed compatibility with data from the Aqua/Moderate Resolution Imaging Spectroradiometer (MODIS) which have been available from 2000 to the present. Some differences in the trends from the two hemispheres are expected because of very different geographical environments in the two regions. The relationships of the trend with the atmospheric global circulation in the north, as defined by the Northern Annular Mode (NAM), and that in the south, as defined by the Southern Annular Mode (SAM), have been observed to be generally weak. The occurrences of the Antarctic Circumpolar Wave (ACW) and ENSO were also studied and not considered a significant factor. It is intriguing that the observed variability in

  13. Signal enhancement of surface enhanced Raman scattering and surface enhanced resonance Raman scattering using in situ colloidal synthesis in microfluidics.

    Science.gov (United States)

    Wilson, Rab; Bowden, Stephen A; Parnell, John; Cooper, Jonathan M

    2010-03-01

    We demonstrate the enhanced analytical sensitivity of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) responses, resulting from the in situ synthesis of silver colloid in a microfluidic flow structure, where both mixing and optical interrogation were integrated on-chip. The chip-based sensor was characterized with a model Raman active label, rhodamine-6G (R6G), and had a limit of detection (LOD) of ca. 50 fM (equivalent to single molecule detection). The device was also used for the determination of the natural pigment, scytonemin, from cyanobacteria (as an analogue for extraterrestrial life existing in extreme environments). The observed LOD of approximately 10 pM (ca. microfluidic system than those measured using the same experimental parameters, with colloid synthesized off-chip, under quiescent conditions.

  14. Effect of surface charge on the brain delivery of nanostructured lipid carriers in situ gels via the nasal route.

    Science.gov (United States)

    Gabal, Yasmine M; Kamel, Amany O; Sammour, Omaima A; Elshafeey, Ahmed H

    2014-10-01

    The aim of this study was to investigate the influence of the nanocarrier surface charge on brain delivery of a model hydrophilic drug via the nasal route. Anionic and cationic nanostructured lipid carriers (NLCs) were prepared and optimized for their particle size and zeta potential. The optimum particles were incorporated in poloxamer in situ gels and their in vivo behavior was studied in the plasma and brain after administration to rats. Optimum anionic and cationic NLCs of size nasal epithelium in rats treated with the anionic NLCs (A7), and destruction of the lining mucosal nasal epithelium in rats treated with the cationic NLCs (C7L). The absolute bioavailability of both drug loaded anionic and cationic NLCs in situ gels was enhanced compared to that of the intranasal solution (IN) of the drug with values of 44% and 77.3%, respectively. Cationic NLCs in situ gel showed a non significant higher Cmax (maximum concentration) in the brain compared to the anionic NLCs in situ gel. Anionic NLCs in situ gel gave highest drug targeting efficiency in the brain (DTE%) with a value of 158.5 which is nearly 1.2 times that of the cationic NLCs in situ gel.

  15. DeepPIV: Measuring in situ Biological-Fluid Interactions from the Surface to Benthos

    Science.gov (United States)

    Katija, K.; Sherman, A.; Graves, D.; Kecy, C. D.; Klimov, D.; Robison, B. H.

    2015-12-01

    The midwater region of the ocean (below the euphotic zone and above the benthos) is one of the largest ecosystems on our planet, yet it remains one of the least explored. Little known marine organisms that inhabit midwater have developed strategies for swimming and feeding that ultimately contributes to their evolutionary success, and may inspire engineering solutions for societally relevant challenges. Fluid mechanics governs the interactions that midwater organisms have with their physical environment, but limited access to midwater depths and lack of non-invasive methods to measure in situ small-scale fluid motions prevent these interactions from being better understood. Significant advances in underwater vehicle technologies have only recently improved access to midwater. Unfortunately, in situ small-scale fluid mechanics measurement methods are still lacking in the oceanographic community. Here we present DeepPIV, an instrumentation package that can be affixed to remotely operated underwater vehicles that quantifies small-scale fluid motions from the surface of the ocean down to 4000 m depths. Utilizing ambient, suspended particulate in the coastal regions of Monterey Bay, fluid-structure interactions are evaluated on a range of marine organisms in midwater. Initial science targets include larvaceans, biological equivalents of flapping flexible foils, that create mucus houses to filter food. Little is known about the structure of these mucus houses and the function they play in selectively filtering particles, and these dynamics can serve as particle-mucus models for human health. Using DeepPIV, we reveal the complex structures and flows generated within larvacean mucus houses, and elucidate how these structures function.

  16. In Situ SIMS and IR Spectroscopy of Well-Defined Surfaces Prepared by Soft Landing of Mass-Selected Ions

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Grant E.; Gunaratne, Kalupathirannehelage Don D.; Laskin, Julia

    2014-06-16

    Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using conventional synthesis techniques. Coupling soft landing with in situ characterization using secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS) enables analysis of well-defined surfaces under clean vacuum conditions. The capabilities of three soft-landing instruments constructed in our laboratory are illustrated for the representative system of surface-bound organometallics prepared by soft landing of mass-selected ruthenium tris(bipyridine) dications, [Ru(bpy)3]2+, onto carboxylic acid terminated self-assembled monolayer surfaces on gold (COOH-SAMs). In situ time-of-flight (TOF)-SIMS provides insight into the reactivity of the soft-landed ions. In addition, the kinetics of charge reduction, neutralization and desorption occurring on the COOH-SAM both during and after ion soft landing are studied using in situ Fourier transform ion cyclotron resonance (FT-ICR)-SIMS measurements. In situ IRRAS experiments provide insight into how the structure of organic ligands surrounding metal centers is perturbed through immobilization of organometallic ions on COOH-SAM surfaces by soft landing. Collectively, the three instruments provide complementary information about the chemical composition, reactivity and structure of well-defined species supported on surfaces.

  17. Correlation between Photoluminescence and Carrier Transport and a Simple In Situ Passivation Method for High-Bandgap Hybrid Perovskites.

    Science.gov (United States)

    Stoddard, Ryan J; Eickemeyer, Felix T; Katahara, John K; Hillhouse, Hugh W

    2017-07-20

    High-bandgap mixed-halide hybrid perovskites have higher open-circuit voltage deficits and lower carrier diffusion lengths than their lower-bandgap counterparts. We have developed a ligand-assisted crystallization (LAC) technique that introduces additives in situ during the solvent wash and developed a new method to dynamically measure the absolute intensity steady-state photoluminescence and the mean carrier diffusion length simultaneously. The measurements reveal four distinct regimes of material changes and show that photoluminescence brightening often coincides with losses in carrier transport, such as in degradation or phase segregation. Further, the measurements enabled optimization of LAC on the 1.75 eV bandgap FA0.83Cs0.17Pb(I0.66Br0.34)3, resulting in an enhancement of the photoluminescence quantum yield (PLQY) of over an order of magnitude, an increase of 80 meV in the quasi-Fermi level splitting (to 1.29 eV), an increase in diffusion length by a factor of 3.5 (to over 1 μm), and enhanced open-circuit voltage and short-circuit current from photovoltaics fabricated from the LAC-treated films.

  18. In situ droplet surface tension and viscosity measurements in gas metal arc welding

    Science.gov (United States)

    Bachmann, B.; Siewert, E.; Schein, J.

    2012-05-01

    In this paper, we present an adaptation of a drop oscillation technique that enables in situ measurements of thermophysical properties of an industrial pulsed gas metal arc welding (GMAW) process. Surface tension, viscosity, density and temperature were derived expanding the portfolio of existing methods and previously published measurements of surface tension in pulsed GMAW. Natural oscillations of pure liquid iron droplets are recorded during the material transfer with a high-speed camera. Frame rates up to 30 000 fps were utilized to visualize iron droplet oscillations which were in the low kHz range. Image processing algorithms were employed for edge contour extraction of the droplets and to derive parameters such as oscillation frequencies and damping rates along different dimensions of the droplet. Accurate surface tension measurements were achieved incorporating the effect of temperature on density. These are compared with a second method that has been developed to accurately determine the mass of droplets produced during the GMAW process which enables precise surface tension measurements with accuracies up to 1% and permits the study of thermophysical properties also for metals whose density highly depends on temperature. Thermophysical properties of pure liquid iron droplets formed by a wire with 1.2 mm diameter were investigated in a pulsed GMAW process with a base current of 100 A and a pulse current of 600 A. Surface tension and viscosity of a sample droplet were 1.83 ± 0.02 N m-1 and 2.9 ± 0.3 mPa s, respectively. The corresponding droplet temperature and density are 2040 ± 50 K and 6830 ± 50 kg m-3, respectively.

  19. Invited Article: In situ comparison of passive radon-thoron discriminative monitors at subsurface workplaces in Hungary

    Science.gov (United States)

    Kávási, Norbert; Vigh, Tamás; Németh, Csaba; Ishikawa, Tetsuo; Omori, Yasutaka; Janik, Miroslaw; Yonehara, Hidenori

    2014-02-01

    During a one-year long measurement period, radon and thoron data obtained by two different passive radon-thoron discriminative monitors were compared at subsurface workplaces in Hungary, such as mines (bauxite and manganese ore) and caves (medical and touristic). These workplaces have special environmental conditions, such as, stable and high relative humidity (100%), relatively stable temperature (12°C-21°C), low or high wind speed (max. 2.4 m s-1) and low or elevated aerosol concentration (130-60 000 particles m-3). The measured radon and thoron concentrations fluctuated in a wide range among the different workplaces. The respective annual average radon concentrations and their standard deviations (in brackets) measured by the passive radon-thoron discriminative monitor with cellulose filter (CF) and the passive radon-thoron discriminative monitor with sponge filter (SF) were: 350(321) Bq m-3 and 550(497) Bq m-3 in the bauxite mine; 887(604) Bq m-3 and 1258(788) Bq m-3 in the manganese ore mine; 2510(2341) Bq m-3 and 3403(3075) Bq m-3 in the medical cave (Hospital Cave of Tapolca); and 6239(2057) Bq m-3 and 8512(1955) Bq m-3 in the touristic cave (Lake Cave of Tapolca). The respective average thoron concentrations and their standard deviation (in brackets) measured by CF and SF monitors were: 154(210) Bq m-3 and 161(148) Bq m-3 in the bauxite mine; 187(191) Bq m-3 and 117(147) Bq m-3 in the manganese-ore mine; 360(524) Bq m-3 and 371(789) Bq m-3 in the medical cave (Hospital Cave of Tapolca); and 1420(1184) Bq m-3 and 1462(3655) Bq m-3 in the touristic cave (Lake Cave of Tapolca). Under these circumstances, comparison of the radon data for the SF and CF monitors showed the former were consistently 51% higher in the bauxite mine, 38% higher in the manganese ore mine, and 34% higher in the caves. Consequently, correction is required on previously obtained radon data acquired by CF monitors at subsurface workplaces to gain comparable data for SF monitors. In the

  20. Exploring electrosorption at iron electrode with in situ surface-enhanced infrared absorption spectroscopy.

    Science.gov (United States)

    Huo, Sheng-Juan; Wang, Jin-Yi; Yao, Jian-Lin; Cai, Wen-Bin

    2010-06-15

    Surface-enhanced infrared absorption spectroscopy (SEIRAS) in attenuated total reflection (ATR) configuration has been extended to the Fe electrode/electrolyte interface in neutral and weakly acidic solutions for the first time. The SEIRA-active Fe film electrode was obtained through a potentiostatic electrodeposition of a virtually pinhole-free 40 nm-thick Fe overfilm onto a 60 nm-thick Au underfilm chemically predeposited on the reflecting plane of an ATR Si prism. The infrared absorption for CO adlayer at the Fe film electrode measured with ATR-SEIRAS was enhanced by a factor of larger than 34, as compared to that at a Fe bulk electrode with external infrared absorption spectroscopy in the literature. More importantly, the unipolar band shape enabled the reliable determination of the Stark tuning rates of CO adlayer at Fe electrode. In situ ATR-SEIRAS was also applied to study the electrosorption of a typical corrosion inhibitor benzotriazole (BTAH) on Fe electrode as a function of potential, providing additional spectral information at positive potentials in support of the formation of a polymer-like surface complex Fe(II)(m)(BTA)(n) as the corrosion-resistant layer.

  1. In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

    Science.gov (United States)

    Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

    2015-09-15

    Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Passive and active EO sensing of small surface vessels

    Science.gov (United States)

    Steinvall, Ove; Berglund, Folke; Allard, Lars; Öhgren, Johan; Larsson, Hâkan; Amselem, Elias; Gustafsson, Frank; Repasi, Endre; Lutzmann, Peter; Göhler, Benjamin; Hammer, Marcus; McEwen, Kennedy; McEwan, Ken

    2015-10-01

    The detection and classification of small surface targets at long ranges is a growing need for naval security. This paper will present an overview of a measurement campaign which took place in the Baltic Sea in November 2014. The purpose was to test active and passive EO sensors (10 different types) for the detection, tracking and identification of small sea targets. The passive sensors were covering the visual, SWIR, MWIR and LWIR regions. Active sensors operating at 1.5 μm collected data in 1D, 2D and 3D modes. Supplementary sensors included a weather station, a scintillometer, as well as sensors for positioning and attitude determination of the boats. Three boats in the class 4-9 meters were used as targets. After registration of the boats at close range they were sent out to 5-7 km distance from the sensor site. At the different ranges the target boats were directed to have different aspect angles relative to the direction of observation. Staff from IOSB Fraunhofer in Germany and from Selex (through DSTL) in UK took part in the tests beside FOI who was arranging the trials. A summary of the trial and examples of data and imagery will be presented.

  3. An in situ vapour phase hydrothermal surface doping approach for fabrication of high performance Co3O4 electrocatalysts with an exceptionally high S-doped active surface.

    Science.gov (United States)

    Tan, Zhijin; Liu, Porun; Zhang, Haimin; Wang, Yun; Al-Mamun, Mohammad; Yang, Hua Gui; Wang, Dan; Tang, Zhiyong; Zhao, Huijun

    2015-04-04

    A facile in situ vapour phase hydrothermal (VPH) surface doping approach has been developed for fabrication of high performance S-doped Co3O4 electrocatalysts with an unprecedentedly high surface S content (>47%). The demonstrated VPH doping approach could be useful for enrichment of surface active sites for other metal oxide electrocatalysts.

  4. Passive PE Sampling in Support of In Situ Remediation of Contaminated Sediments: Standard Operating Procedure for PE Analysis

    Science.gov (United States)

    2012-12-01

    biofilms and epiphytic growth on PE surfaces does not compromise their behavior in the field during deployment, these coatings can substantially...4.5 Food -grade aluminum foil 4.6 Stainless steel forceps 4.7 Single-edge razor blades 4.8 Teflon (or similar non-contaminating material) cutting...extracted using organic solvents prior to analysis by GC/MS. 7.1.1 The PE is inspected for surface biofilms , particles, mud, or oily coatings. Biofilm

  5. In Situ Control of Underwater-Pinning of Organic Droplets on a Surfactant-Doped Conjugated Polymer Surface.

    Science.gov (United States)

    Xu, Wei; Xu, Jian; Choi, Chang-Hwan; Yang, Eui-Hyeok

    2015-11-25

    Controlling the pinning of organic droplets on solid surfaces is of fundamental and practical interest in the field of material science and engineering, which has numerous applications such as surface cleaning, water treatment, and microfluidics. Here, a rapid in situ control of pinning and actuation of organic droplets is demonstrated on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) surfaces in an aqueous environment via an electrochemical redox process. A dramatic change of the pinning results from the transport of DBS(-) molecules between the PPy(DBS) surface and the aqueous environment, as well as from a simultaneous alternation of the surface oleophobicity to organic liquids during the redox process. This in situ control of the droplet pinning enables a stop-and-go droplet actuation, applicable to both polar and apolar organic droplets, at low voltages (∼0.9 V) with an extremely low roll-off angle (∼0.4°).

  6. Band-structure tailoring and surface passivation for highly efficient near-infrared responsive PbS quantum dot photovoltaics

    Science.gov (United States)

    Zhou, Ru; Niu, Haihong; Ji, Fengwei; Wan, Lei; Mao, Xiaoli; Guo, Huier; Xu, Jinzhang; Cao, Guozhong

    2016-11-01

    PbS is a promising light harvester for near-infrared (NIR) responsive quantum dot (QD) photovoltaics due to its narrow bulk band gap (0.41 eV) and large exciton Bohr radius (18 nm). However, the relatively low conduction band (CB) and high-density surface defects of PbS as two major drawbacks for its use in solar cells severely hamper the photovoltaic performance enhancement. In this work, a modified solution-based successive ionic layer adsorption and reaction (SILAR) utilizing mixed cationic precursors of Pb2+ and Cd2+ is explored, and such a scheme offers two benefits, band-structure tailoring and surface passivation. In-situ deposited CdS suppresses the excessive growth of PbS in the mesopores, thereby facilitating the favorable electron injection from PbS to TiO2 in view of the up-shifted CB level of QDs; the intimate interpenetration of two sulfides with each other leads to superior passivation of trap state defects on PbS, which suppresses the interfacial charge recombination. With the construction of photovoltaics based on such a hybrid (Pb,Cd)S/CdS configuration, impressive power conversion efficiency up to 4.08% has been reached, outperforming that of the conventional PbS/CdS pattern (2.95%). This work highlights the great importance of band-structure tailoring and surface passivation for constructing highly efficient PbS QD photovoltaics.

  7. Observations of Bathymetry-Induced Ocean Roughness Modulation in In-situ Surface Slope Measurements and Coincident Airborne SAR Images

    NARCIS (Netherlands)

    Gommenginger, C.P.; Robinson, I.S.; Willoughby, J.; Greidanus, H.S.F.; Taylor, V.

    1999-01-01

    Empirical results from a field experiment in the southern North Sea have demonstrated the possibility to detect bathymetry-induced sea surface roughness modulation in the coastal zone using high frequency in-situ slope measurements provided by the Towed Laser Slopemeter. A strong correlation between

  8. Corona field effect surface passivation of n-type IBC cells

    OpenAIRE

    Bonilla, RS; Wilshaw, PR; Reichel, C; Hermle, M.

    2016-01-01

    Passivation of silicon surfaces is an important requirement in achieving high energy conversion efficiencies in interdigitated back contact cells. Surface passivation, commonly achieved by dielectric coatings, can be greatly improved by extrinsic addition of chemical and field effect components. In particular, cell performance is strongly dependent on front surface passivation. In this work device modelling is used to show that 200% relatively better performance can be achieved using charge e...

  9. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis.

    Science.gov (United States)

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  10. In situ analysis of dynamic laminar flow extraction using surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Wang, Fei; Wang, Hua-Lin; Qiu, Yang; Chang, Yu-Long; Long, Yi-Tao

    2015-12-01

    In this study, we performed micro-scale dynamic laminar flow extraction and site-specific in situ chloride concentration measurements. Surface-enhanced Raman spectroscopy was utilized to investigate the diffusion process of chloride ions from an oil phase to a water phase under laminar flow. In contrast to common logic, we used SERS intensity gradients of Rhodamine 6G to quantitatively calculate the concentration of chloride ions at specific positions on a microfluidic chip. By varying the fluid flow rates, we achieved different extraction times and therefore different chloride concentrations at specific positions along the microchannel. SERS spectra from the water phase were recorded at these different positions, and the spatial distribution of the SERS signals was used to map the degree of nanoparticle aggregation. The concentration of chloride ions in the channel could therefore be obtained. We conclude that this method can be used to explore the extraction behaviour and efficiency of some ions or molecules that enhance the SERS intensity in water or oil by inducing nanoparticle aggregation.

  11. The gravimeter "B-grave" for the in-situ surface gravity measurements of an asteroid

    Science.gov (United States)

    van Ruymbeke, Michel; karatekin, ozgur; rasson, jean; wielant, françois; dumont, Phillipe; Ritter, Birgit; zhu, Ping

    2016-04-01

    In the context of the preliminary study phase for the CubeSats supporting ESA's Asteroid Impact Mission (AIM) to the Didymos, we investigate a miniaturized gravimeter as part of the geophysical instrument package for the Asteroid Geophysical Explorer (AGEX). AGEX intends to land a CubeSat on the secondary object in the Didymos system, Didymoon in order to characterize the asteroid surface and internal structure A 3D compact gravimeter is developed at the Royal Observatory of Belgium. Its design allows to meter a weak 50 μm/sec² gravity field corresponding to 5 ppm of Earth gravity in a harsh environment. A system with three components mounted in an orthogonal geometry allows obtaining the gravity field in amplitude and in angular position without any requirement of levelling. B-GRAVES will use a in-situ calibration and multi-parameter approach for validation of the measurements. A laboratory simulation is induced with centrifugal forces applied to the pendulum set-up in a vertical position to reject the Earth gravity field. Signal treatment and uncertainties are discussed keeping in mind questions of thermal and vibration influence. The B-GRAVES can serve as a novel and robust instrument for future lander and rover missions .

  12. Destruction of oral biofilms formed in situ on machined titanium (Ti) surfaces by cold atmospheric plasma.

    Science.gov (United States)

    Idlibi, Ahmad Nour; Al-Marrawi, Fuad; Hannig, Matthias; Lehmann, Antje; Rueppell, Andre; Schindler, Axel; Jentsch, Holger; Rupf, Stefan

    2013-01-01

    The decontamination of implant surfaces represents the basic procedure in the management of peri-implant diseases, but it is still a challenge. The study aimed to evaluate the degradation of oral biofilms grown in situ on machined titanium (Ti) discs by cold atmospheric plasma (CAP). ~200 Ti discs were exposed to the oral cavities of five healthy human volunteers for 72 h. The resulting biofilms were divided randomly between the following treatments: CAP (which varied in mean power, treatment duration, and/or the gas mixture), and untreated and treated controls (diode laser, air-abrasion, chlorhexidine). The viability, quantity, and morphology of the biofilms were determined by live/dead staining, inoculation onto blood agar, quantification of the total protein content, and scanning electron microscopy. Exposure to CAP significantly reduced the viability and quantity of biofilms compared with the positive control treatments. The efficacy of treatment with CAP correlated with the treatment duration and plasma power. No single method achieved complete biofilm removal; however, CAP may provide an effective support to established decontamination techniques for treatment of peri-implant diseases.

  13. In situ measurement of active catalyst surface area in fuel cell stacks

    Science.gov (United States)

    Brightman, E.; Hinds, G.; O'Malley, R.

    2013-11-01

    Measurement of electrochemical surface area (ECSA) of fuel cell electrodes is a key diagnostic of performance and gives a useful parameter for monitoring degradation and state of health in polymer electrolyte membrane fuel cells (PEMFCs). However, conventional methods for determining ECSA require potentiostatic control of the cell, which is impractical in a fuel cell stack. Here we demonstrate for the first time the practical application of a galvanostatic technique that enables in situ monitoring of ECSA in each cell throughout the lifetime of a stack. The concept is demonstrated at single cell level using both H adsorption and CO stripping, and the H adsorption (cathodic current) method is extended to stack testing. The undesirable effects of H2 crossover on the measurement may be minimised by appropriate selection of current density and by working with dilute H2 on the anode electrode. Good agreement is achieved with ECSA values determined using conventional single cell voltammetry across a range of MEA designs. The technique is straightforward to implement and provides an invaluable tool for state of health monitoring during PEMFC stack lifetime studies.

  14. Direct observation of the binding process between protein and quantum dots by in situ surface plasmon resonance measurements

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Qi; Zhou Bo; Tian Fangfang; Ge Yushu; Liu Xiaorong; Liu Yi [State Key Laboratory of Virology, College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072 (China); Huang Shan; Guan Hongliang; He Zhike, E-mail: prof.liuyi@263.ne [Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China)

    2009-08-12

    A layer-by-layer surface decoration technique has been developed to anchor quantum dots (QDs) onto a gold substrate and an in situ surface plasmon resonance technique has been used to study interactions between the QDs and different proteins. Direct observation of the binding of the protein onto the QDs and the kinetics of the adsorption and dissociation of different proteins on the QDs has been achieved. This would be helpful for the identification of particle-associated proteins and may offer a fundamental prerequisite for nanobiology, nanomedicine and nanotoxicology. The combination of the novel layer-by-layer surface modification method and in situ surface plasmon resonance would be powerful in studying biological systems such as DNA and cells.

  15. R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    S.-H. Kim, M.T. Crofford, M. Doleans, J.D. Mammosser, J. Saunders

    2011-03-01

    The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS.

  16. In situ transmission infrared spectroscopy of high-kappa oxide atomic layer deposition onto silicon surfaces

    Science.gov (United States)

    Ho, Ming-Tsung

    Ultra-thin aluminum oxide (Al2O3) and hafnium oxide (HfO2) layers have been grown by atomic layer deposition (ALD) using tri-methyl-aluminum (TMA) and tetrakis-ethyl-methyl-amino-hafnium (TEMAH) respectively with heavy water (D2O) as the oxidizing agent. Several different silicon surfaces were used as substrates such as hydrogen terminated silicon (H/Si), SC2 (or RCA 2) cleaned native silicon oxide (SiO 2/Si), and silicon (oxy)nitride. In-situ transmission Fourier transform infrared spectroscopy (FTIR) has been adopted for the study of the growth mechanisms during ALD of these films. The vibrational spectra of gas phase TEMAH and its reaction byproducts with oxidants have also been investigated. Density functional theory (DFT) normal mode calculations show a good agreement with the experimental data when it is combined with linear wave-number scaling method and Fermi resonance mechanism. Ether (-C-O-C-) and tertiary alkylamine (N(R1R 2R3)) compounds are the two most dominant products of TEMAH reacting with oxygen gas and water. When ozone is used as the oxidant, gas phase CH2O, CH3NO2, CH3-N=C=O and other compounds containing -(C=O)- and --C-O-C- (or --O-C-) segments are observed. With substrate temperatures less than 400°C and 300°C for TMA and TEMAH respectively, Al oxide and Hf oxide ALD can be appropriately performed on silicon surfaces. Thin silicon (oxy)nitride thermally grown in ammonia on silicon substrate can significantly reduce silicon oxide interlayer formation during ALD and post-deposition annealing. The crystallization temperature of amorphous ALD grown HfO2 on nitridized silicon is 600°C, which is 100°C higher than on the other silicon surfaces. When HfO2 is grown on H/Si(111) at 100°C deposition temperature, minimum 5--10 ALD cycles are required for the full surface coverage. The steric effect can be seen by the evolution of the H-Si stretching mode at 2083 cm-1. The observed red shift of H-Si stretching to ˜ 2060 cm-1 can be caused by Si

  17. Interactions of arsenic with calcite surfaces revealed by in situ nanoscale imaging

    Science.gov (United States)

    Renard, François; Putnis, Christine V.; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hovelmann, Jörn; Sarret, Géraldine

    2015-06-01

    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in situ study of the evolution of the (10-14) calcite cleavage surface morphology during dissolution and growth in the presence of solutions with various amounts of As(III) or As(V) at room temperature and pH range 6-11 using a flow-through cell connected to an atomic force microscope (AFM). Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  18. Interactions of arsenic with calcite surfaces revealed by in-situ nanoscale imaging

    Science.gov (United States)

    Renard, Francois; Putnis, Christine; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hövelmann, Jörn; Sarret, Géraldine

    2015-04-01

    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in-situ study of calcite dissolution and growth in the presence of solutions with various amounts of As(III) or As(V). This was performed at room temperature and pH range 6-9 using a flow through cell connected to an atomic force microscope (AFM), to study the evolution of the (10-14) calcite cleavage surface morphology. Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  19. RF Magnetron Sputtering Aluminum Oxide Film for Surface Passivation on Crystalline Silicon Wafers

    Directory of Open Access Journals (Sweden)

    Siming Chen

    2013-01-01

    Full Text Available Aluminum oxide films were deposited on crystalline silicon substrates by reactive RF magnetron sputtering. The influences of the deposition parameters on the surface passivation, surface damage, optical properties, and composition of the films have been investigated. It is found that proper sputtering power and uniform magnetic field reduced the surface damage from the high-energy ion bombardment to the silicon wafers during the process and consequently decreased the interface trap density, resulting in the good surface passivation; relatively high refractive index of aluminum oxide film is benefic to improve the surface passivation. The negative-charged aluminum oxide film was then successfully prepared. The surface passivation performance was further improved after postannealing by formation of an SiOx interfacial layer. It is demonstrated that the reactive sputtering is an effective technique of fabricating aluminum oxide surface passivation film for low-cost high-efficiency crystalline silicon solar cells.

  20. PEGylated graphene oxide elicits strong immunological responses despite surface passivation

    Science.gov (United States)

    Luo, Nana; Weber, Jeffrey K.; Wang, Shuang; Luan, Binquan; Yue, Hua; Xi, Xiaobo; Du, Jing; Yang, Zaixing; Wei, Wei; Zhou, Ruhong; Ma, Guanghui

    2017-02-01

    Engineered nanomaterials promise to transform medicine at the bio-nano interface. However, it is important to elucidate how synthetic nanomaterials interact with critical biological systems before such products can be safely utilized in humans. Past evidence suggests that polyethylene glycol-functionalized (PEGylated) nanomaterials are largely biocompatible and elicit less dramatic immune responses than their pristine counterparts. We here report results that contradict these findings. We find that PEGylated graphene oxide nanosheets (nGO-PEGs) stimulate potent cytokine responses in peritoneal macrophages, despite not being internalized. Atomistic molecular dynamics simulations support a mechanism by which nGO-PEGs preferentially adsorb onto and/or partially insert into cell membranes, thereby amplifying interactions with stimulatory surface receptors. Further experiments demonstrate that nGO-PEG indeed provokes cytokine secretion by enhancing integrin β8-related signalling pathways. The present results inform that surface passivation does not always prevent immunological reactions to 2D nanomaterials but also suggest applications for PEGylated nanomaterials wherein immune stimulation is desired.

  1. PEGylated graphene oxide elicits strong immunological responses despite surface passivation

    Science.gov (United States)

    Luo, Nana; Weber, Jeffrey K.; Wang, Shuang; Luan, Binquan; Yue, Hua; Xi, Xiaobo; Du, Jing; Yang, Zaixing; Wei, Wei; Zhou, Ruhong; Ma, Guanghui

    2017-01-01

    Engineered nanomaterials promise to transform medicine at the bio–nano interface. However, it is important to elucidate how synthetic nanomaterials interact with critical biological systems before such products can be safely utilized in humans. Past evidence suggests that polyethylene glycol-functionalized (PEGylated) nanomaterials are largely biocompatible and elicit less dramatic immune responses than their pristine counterparts. We here report results that contradict these findings. We find that PEGylated graphene oxide nanosheets (nGO-PEGs) stimulate potent cytokine responses in peritoneal macrophages, despite not being internalized. Atomistic molecular dynamics simulations support a mechanism by which nGO-PEGs preferentially adsorb onto and/or partially insert into cell membranes, thereby amplifying interactions with stimulatory surface receptors. Further experiments demonstrate that nGO-PEG indeed provokes cytokine secretion by enhancing integrin β8-related signalling pathways. The present results inform that surface passivation does not always prevent immunological reactions to 2D nanomaterials but also suggest applications for PEGylated nanomaterials wherein immune stimulation is desired. PMID:28233871

  2. Evaluation of OMI operational standard NO2 column retrievals using in situ and surface-based NO2 observations

    Directory of Open Access Journals (Sweden)

    L. N. Lamsal

    2014-06-01

    Full Text Available We assess the standard operational nitrogen dioxide (NO2 data product (OMNO2, version 2.1 retrieved from the Ozone Monitoring Instrument (OMI onboard NASA's Aura satellite using a combination of aircraft and surface in situ measurements as well as ground-based column measurements at several locations and a bottom-up NOx emission inventory over the continental US. Despite considerable sampling differences, NO2 vertical column densities from OMI are modestly correlated (r = 0.3–0.8 with in situ measurements of tropospheric NO2 from aircraft, ground-based observations of NO2 columns from MAX-DOAS and Pandora instruments, in situ surface NO2 measurements from photolytic converter instruments, and a bottom-up NOx emission inventory. Overall, OMI retrievals tend to be lower in urban regions and higher in remote areas, but generally agree with other measurements to within ± 20%. No consistent seasonal bias is evident. Contrasting results between different data sets reveal complexities behind NO2 validation. Monthly mean vertical NO2 profile shapes from the Global Modeling Initiative (GMI chemistry-transport model (CTM used in the OMI retrievals are highly consistent with in situ aircraft measurements, but these measured profiles exhibit considerable day-to-day variation, affecting the retrieved daily NO2 columns by up to 40%. This assessment of OMI tropospheric NO2 columns, together with the comparison of OMI-retrieved and model-simulated NO2 columns, could offer diagnostic evaluation of the model.

  3. Novel in situ mechanical testers to enable integrated metal surface micro-machines.

    Energy Technology Data Exchange (ETDEWEB)

    Follstaedt, David Martin; de Boer, Maarten Pieter; Kotula, Paul Gabriel; Hearne, Sean Joseph; Foiles, Stephen Martin; Buchheit, Thomas Edward; Dyck, Christopher William

    2005-10-01

    The ability to integrate metal and semiconductor micro-systems to perform highly complex functions, such as RF-MEMS, will depend on developing freestanding metal structures that offer improved conductivity, reflectivity, and mechanical properties. Three issues have prevented the proliferation of these systems: (1) warpage of active components due to through-thickness stress gradients, (2) limited component lifetimes due to fatigue, and (3) low yield strength. To address these issues, we focus on developing and implementing techniques to enable the direct study of the stress and microstructural evolution during electrodeposition and mechanical loading. The study of stress during electrodeposition of metal thin films is being accomplished by integrating a multi-beam optical stress sensor into an electrodeposition chamber. By coupling the in-situ stress information with ex-situ microstructural analysis, a scientific understanding of the sources of stress during electrodeposition will be obtained. These results are providing a foundation upon which to develop a stress-gradient-free thin film directly applicable to the production of freestanding metal structures. The issues of fatigue and yield strength are being addressed by developing novel surface micromachined tensile and bend testers, by interferometry, and by TEM analysis. The MEMS tensile tester has a ''Bosch'' etched hole to allow for direct viewing of the microstructure in a TEM before, during, and after loading. This approach allows for the quantitative measurements of stress-strain relations while imaging dislocation motion, and determination of fracture nucleation in samples with well-known fatigue/strain histories. This technique facilitates the determination of the limits for classical deformation mechanisms and helps to formulate a new understanding of the mechanical response as the grain sizes are refined to a nanometer scale. Together, these studies will result in a science

  4. Chlorine and Sulfur Volatiles from in Situ Measurements of Martian Surface Materials

    Science.gov (United States)

    Clark, B. C.

    2014-12-01

    A sentinel discovery by the first in situ measurements on Mars was the high sulfur and chlorine content of global-wide soils. A variety of circumstantial evidence led to the conclusion that soil S is in the form of sulfate, and the Cl is probably chloride. An early hypothesis states that these volatiles are emitted as gases from magmas, and quickly react with dust, soil, and exposed rocks. Subsequent determination that SNC meteorites are also samples of the martian crust revealed a significantly higher S content, as sulfide, than terrestrial igneous rocks but substantially less than in soils. The ensuing wet chemical analyses by the high-latitude Phoenix mission discovered not only chloride but also perchlorate and possibly chlorate. MSL data now also implicate perchlorate at low latitudes. Gaseous interactions may have produced amorphous material on grain surfaces without forming stoichiometric salts. Yet, when exposed to liquid water, Phoenix samples released electrolytes, indicating that the soils have not been leached by rain or fresh groundwater. Sulfate occurrences at many locations on Mars, as well as some chloride enrichments, have now been discovered by remote sensing, Landed missions have discovered Cl-enrichments and ferric, Mg, Ca and more complex sulfates as duricrust, subsurface soil horizons, sandstone evaporites, and rock coatings - most of which cannot be detected from orbit. Salt-forming volatiles affect habitability wherever they are in physical contact: physicochemical parameters (ionic strength, freezing point, water activity); S is an essential element for terrestrial organisms; perchlorate is an oxidant which can degrade some organics but also can be utilized as an energy source; the entire valence range of S-compounds has been exploited by diverse microbiota on Earth. Whether such salt-induced conditions are "extremes" of habitability depends on the relative abundance of liquid H2O.

  5. Surface-Satellite Measurements for Atmospheric Radiative Transfer (SMART)and Chemical, Optical and Microphysical Measurements of In-Situ Troposphere (COMMIT) Research Activities

    Science.gov (United States)

    Tsay, Si-Chee

    2004-01-01

    The GSFC SMART consists of a suite of remote sensing instruments, including many commercially available radiometers, spectrometer, interferometer, and three in-house developed inskuments: micro-pulse lidar (MPL), scanning microwave radiometer (SMiR), and sun-sky-surface photometer (S(sup 3)). SMART cover the spectral range from UV to microwave, and passive to active remote sensing. This is to enrich the EOS-like research activities (i.e., EOS validation, innovative investigations, and long-term local environmental observations). During past years, SMART has been deployed in many NASA supported field campaigns to collocate with satellite nadir overpass for intercomparisons, and for initializing model simulations. Built on the successful experience of SMART, we are currently developing a new ground-based in-situ sampling package, COMMIT, including measurements of trace gases (CO, SO2, NOx, and O3,) concentrations, fine/coarse particle sizers and chemical composition, single- and three-wavelength nephelometers, and surface meteorological probes. COMMIT is built for seeking a relationship between surface in-situ measurements and boundary layer characteristics. This is to enrich EOS-like research on removing boundary layer signal from the entire column from space observation - to deduce the stable (less variability) free-troposphere observations. The COMMIT will try its best to link the chemical, microphysical, and optical properties of the boundary layer with radiation. The next major activities for SMART-COMMIT are scheduled for 2004-2006 in BASE-ASIA and EAST-AIRE. The expected close collaboration of BASE-ASIA with various research projects in Asia (i.e., ABC in South Asia, led by Ramanathan et al.; EAST-AIRE in East Asia, led by Li et al.; and APEX in Northeast Asia, led by Nakajima et al.) will definitely provide a better understanding of the impact of the biomass burning and air pollutants on regional-to-global climate, hydrological and carbon cycles, and

  6. High quality crystalline silicon surface passivation by combined intrinsic and n-type hydrogenated amorphous silicon

    NARCIS (Netherlands)

    Schuttauf, J.A.; van der Werf, C.H.M.; Kielen, I.M.; van Sark, W.G.J.H.M.; Rath, J.K.

    2011-01-01

    We investigate the influence of thermal annealing on the passivation quality of crystalline silicon (c-Si) surfaces by intrinsic and n-type hydrogenated amorphous silicon (a-Si:H) films. For temperatures up to 255 C, we find an increase in surface passivation quality, corresponding to a decreased da

  7. Enhanced Interfacial Adhesion in HDPE/HA Composites by Surface Modification of HA Particles via in situ Polymerization and Copolymerization

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Hydroxyapatite ( HA )-reinforced high density polyethylene (HDPE) was developed as a bone replacement material. In order to enhance the interfacial bondiag between HA and polyethylene and improve the mechanical properties of HDPE/ HA composites, the surface of the micron-sized HA particles was modified by in situ polymerization of butyl acrylate ( BA ) and in situ copolynerization of vinyl triethoxyl silane (VTES) and BA ,then the modified HA particles were compounded with HDPE. The effects of the surface modification of HA on morphology and mechanical properties of HDPE/ HA composites were investigated. The experimental results show that the presence of HA particles does not inhibit the polymerization of BA . The poly( butyl acrylate) ( PBA ) segments on the HA surface enhance the compatibility between HA and HDPE, improve the dispersion of HA particles in HDPE matrix, and enhance the interfacial ndhesion between HA and matrix. Surface modifications, especially by in situ copolymerization of VTES and BA , significantly increase notch impact strengths and marginal stiffness and tensile strengths of HDPE/ HA composites. And it is found that there is a critical thickness of PBA coating on HA particles for optimum mechanical properties of HDPE / HA composites.

  8. Effects of surface passivation on gliding motility assays.

    Directory of Open Access Journals (Sweden)

    Andy Maloney

    Full Text Available In this study, we report differences in the observed gliding speed of microtubules dependent on the choice of bovine casein used as a surface passivator. We observed differences in both speed and support of microtubules in each of the assays. Whole casein, comprised of α(s1, α(s2, β, and κ casein, supported motility and averaged speeds of 966±7 nm/s. Alpha casein can be purchased as a combination of α(s1 and α(s2 and supported gliding motility and average speeds of 949±4 nm/s. Beta casein did not support motility very well and averaged speeds of 870±30 nm/s. Kappa casein supported motility very poorly and we were unable to obtain an average speed. Finally, we observed that mixing alpha, beta, and kappa casein with the proportions found in bovine whole casein supported motility and averaged speeds of 966±6 nm/s.

  9. Multimodal and In-Situ Chemical Imaging of Critical Surfaces and Interfaces in Li Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chong-Min; Zhu, Zihua; Engelhard, Mark H.; Devaraj, Arun; Baer, Donald R.

    2016-03-01

    This article describes ways that a range of microscopy, spectroscopy, and spectrometry tools are being used to address important challenges associated with energy storage science and technology, in particular the development of advanced batteries for transportation, consumer use, and renewable storage. In this article in situ transmission electron microscopy, in situ secondary ion mass spectrometry, and XPS have been used to examine the formation and properties of the solid-electrolyte interphase (SEI) layer. Also TEM, atom probe tomography (APT), and nanoSIMS have been used to optimize the structure and processing of a lithium transition metal oxide cathode.

  10. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    Science.gov (United States)

    Bertram, F.; Zhang, F.; Evertsson, J.; Carlà, F.; Pan, J.; Messing, M. E.; Mikkelsen, A.; Nilsson, J.-O.; Lundgren, E.

    2014-07-01

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  11. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bertram, F., E-mail: florian.bertram@sljus.lu.se; Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E. [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Zhang, F.; Pan, J. [KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, Drottning Kristinas väg 51, 10044 Stockholm (Sweden); Carlà, F. [ESRF, B. P. 220, 38043 Grenoble (France); Nilsson, J.-O. [Sapa Technology, Kanalgatan 1, 612 31 Finspång (Sweden)

    2014-07-21

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  12. Dynamic observation of surface reactions of lithium foils immersed in diethyl carbonate electrolytes by using in-situ FTIR measurement

    Energy Technology Data Exchange (ETDEWEB)

    Kanamura, K.; Takezawa, H. [Kyoto Univ., Kyoto (Japan). Graduate School; Shiraishi, S.; Takehara, Z. [Gunma Univ., Maebashi (Japan). Faculty of Engineering

    1998-03-05

    Rechargeable lithium batteries with lithium metal anodes are very attractive for various applications, however, they have not been applied to practical batteries, due to low cycleability and safety of lithium metal anodes. This problem may be related to the surface state of lithium metal immersed in nonaqueous electrolytes. Several fundamental studies have been carried out, however, the high reactivity of diethyl carbonate with lithium metal has not been clarified yet. In this study, the dynamic behavior of diethyl carbonate containing 1.0 mol dm{sup -3} LiAsF6, LiBF4 and LiCF3SO3 at the interface on lithium foils was observed by using in-situ FTIR spectroscopy. The in-situ FTIR spectra indicated that these diethyl carbonate electrolytes can easily penetrate into the surface film on the lithium foil and directly touch to lithium metal. 28 refs., 8 figs.

  13. Surface passivation of aluminum alloy 6061 with gaseous trichlorosilane: A surface investigation

    Energy Technology Data Exchange (ETDEWEB)

    Ngongang, Rickielle, E-mail: rickielle.ngongang@airliquide.com [Centre de Recherche Claude Delorme, Air Liquide, 1 Chemin de la Porte des Loges Les-Loges en Josas, 78350 Jouy-en-Josas (France); Laboratoire de Réactivité de Surface, UMR CNRS 7197, UPMC (Université Pierre et Marie Curie-Paris 6), site d’Ivry, 3 rue Galilée, 94200 Ivry-sur-Seine (France); Marceau, Eric; Carrier, Xavier; Pradier, Claire-Marie; Methivier, Christophe [Laboratoire de Réactivité de Surface, UMR CNRS 7197, UPMC (Université Pierre et Marie Curie-Paris 6), site d’Ivry, 3 rue Galilée, 94200 Ivry-sur-Seine (France); Blanc, Jean-Luc; Carre, Martine [Centre de Recherche Claude Delorme, Air Liquide, 1 Chemin de la Porte des Loges Les-Loges en Josas, 78350 Jouy-en-Josas (France)

    2014-02-15

    A molecular-scale investigation of the interaction at room temperature between gaseous trichlorosilane (HSiCl{sub 3}), used as a passivating agent, and surfaces of aluminum alloy AA6061 in a polished or hydroxylated state is conducted. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) provide information on the topography and morphology of AA6061 before and after hydroxylation and surface passivation, while surface chemistry has been investigated by Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) and X-ray photoelectron spectroscopy (XPS). Oxidation and hydroxylation of the polished alloy surface in boiling water strongly modifies the roughness of the surface, with formation of platelets and needles of oxyhydroxide AlOOH. PM-IRRAS and XPS reveal that, upon adsorption, HSiCl{sub 3} dissociates and mainly forms HSiOH{sub n}(OAl){sub 3−n}, HSi(OSi){sub n}(OAl){sub 3−n} and condensed HSiO{sub x} species, by reaction with -OH groups from the AlOOH surface phase. The amount of deposited Si-containing species is larger on the rough surface of the hydroxylated alloy and this deposit is accompanied by a decrease of the amount of free -OH groups evidenced by PM-IRRAS. These results can find applications in the field of functionalization of aluminum alloys. It is suggested that a homogeneous oxidation of the alloy surface prior to exposure to gaseous HSiCl{sub 3} may enhance the adsorption of the passivating agent.

  14. Micro-four-point probes in a UHV scanning electron microscope for in-situ surface-conductivity measurements

    DEFF Research Database (Denmark)

    Shiraki, I.; Nagao, T.; Hasegawa, S.;

    2000-01-01

    For in-situ measurements of surface conductivity in ultrahigh vacuum (UHV), we have installed micro-four-point probes (probe spacings down to 4 mum) in a UHV scanning electron microscope (SEM) combined with scanning reflection-high-energy electron diffraction (RHEED). With the aid of piezoactuators...... for precise positioning of the probes, local conductivity of selected surface domains of well-defined superstructures could be measured during SEM and RHEED observations. It was found that the surface sensitivity of the conductivity measurements was enhanced by reducing the probe spacing, enabling...

  15. Application of in-situ passive samplers for the investigation of the impacts of vegetated river beds on mineral N concentration gradients in the hyporheic zone

    Science.gov (United States)

    Ullah, S.; Zhang, H.; Heathwaite, L.; Lansdown, K.; Heppell, K.; Binley, A.; Trimmer, M.; Keenan, P.

    2010-12-01

    Conventional pore water sampling techniques have only a limitated capability to provide fine scale (cm or mm) depth resolution of chemical species associated with a ‘hotspot’ or a ‘hot event' in riverine hyporheic zones. To overcome this limitation, in-situ passive samplers (diffusive equilibrium in thin films-DET) were deployed in hyporheic sediments (0-30 cm depth) both under vegetated beds (dominated by Phragmites, spp.) and non-vegetated beds of a groundwater-fed river in Cumbria, UK. The riverbed environment consisted of coarse gravels and sandstone, requiring development of a new methodology for inserting the DET probes. The objectives were two-fold; 1) to explore the feasibility of DET deployment in hyporheic sediments dominated by gravels, and 2) to assess the impacts of vegetated beds on mineral N concentration gradients (cm scale resolution) to those under non-vegetated beds of the riverbed. The challenge of deploying DET in gravel bed sediments was met. Resulting information on fine scale gradients of mineral N and other redox sensitive species can improve our understanding of the dynamics of hyporheic mineral N species. According to the results, hyporheic sediments under vegetation exhibited significantly lower nitrate concentration gradients compared to non-vegetated hyporheic sediments. A dense piezometer network installed at the site showed that both locations possessed an upwelling potential at the time of DET deployment, and the amount of dissolved organic C was high in the hyporheic under reeds relative to the non-vegetated zones. These preliminary results suggest that vegetated beds in rivers could be effective in removing NO3 through denitrification and plant uptake besides rendering other ecosystem services such as habitat provision.

  16. Solid oxide electrode kinetics in light of in situ surface studies

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg

    2014-01-01

    The combination of in situ and in particular in operando characterization methods such as electrochemical impedance spectroscopy (EIS) on both technical and model electrode are well known ways to gain some practical insight in electrode reaction kinetics. Yet, is has become clear that in spite...

  17. Application of PECVD for bulk and surface passivation of high efficiency silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Krygowski, T.; Doshi, P.; Cai, L.; Doolittle, A.; Rohatgi, A. [Georgia Inst. of Technology, Atlanta, GA (United States)

    1995-08-01

    Plasma enhanced chemical vapor deposition (PECVD) passivation of bulk and surface defects has been shown to be an important technique to improve the performance of multicrystalline silicon (mc-Si) and single crystalline silicon solar cells. In this paper, we report the status of our on-going investigation into the bulk and surface passivation properties of PECVD insulators for photovoltaic applications. The objective of this paper is to demonstrate the ability of PECVD films to passivate the front (emitter) surface, bulk, and back surface by proper tailoring of deposition and post-PECVD annealing conditions.

  18. Ambient plasma treatment of silicon wafers for surface passivation recovery

    Science.gov (United States)

    Ge, Jia; Prinz, Markus; Markert, Thomas; Aberle, Armin G.; Mueller, Thomas

    2017-08-01

    In this work, the effect of an ambient plasma treatment powered by compressed dry air on the passivation quality of silicon wafers coated with intrinsic amorphous silicon sub-oxide is investigated. While long-time storage deteriorates the effective lifetime of all samples, a short ambient plasma treatment improves their passivation qualities. By studying the influence of the plasma treatment parameters on the passivation layers, an optimized process condition was identified which even boosted the passivation quality beyond its original value obtained immediately after deposition. On the other hand, the absence of stringent requirement on gas precursors, vacuum condition and longtime processing makes the ambient plasma treatment an excellent candidate to replace conventional thermal annealing in industrial heterojunction solar cell production.

  19. Osteogenic potential of in situ TiO{sub 2} nanowire surfaces formed by thermal oxidation of titanium alloy substrate

    Energy Technology Data Exchange (ETDEWEB)

    Tan, A.W. [Department of Biomedical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ismail, R.; Chua, K.H. [Department of Physiology, Faculty of Medicine, National University of Malaysia, 50300 Kuala Lumpur (Malaysia); Ahmad, R. [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Akbar, S.A. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210 (United States); Pingguan-Murphy, B., E-mail: bpingguan@um.edu.my [Department of Biomedical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-11-30

    Highlights: • In situ titanium dioxide (TiO{sub 2}) nanowire surface structures were fabricated on Ti-6Al-4V substrate using thermal oxidation. • Initial cell adhesion, cell proliferation, cell differentiation, cell mineralization, and osteogenic related gene expression of primary human osteoblasts were examined on the TiO{sub 2} nanowire surfaces. • TiO{sub 2} nanowire surfaces showed enhanced osteogenic potential as compared to the planar surface. - Abstract: Titanium dioxide (TiO{sub 2}) nanowire surface structures were fabricated in situ by a thermal oxidation process, and their ability to enhance the osteogenic potential of primary osteoblasts was investigated. Human osteoblasts were isolated from nasal bone and cultured on a TiO{sub 2} nanowires coated substrate to assess its in vitro cellular interaction. Bare featureless Ti-6Al-4V substrate was used as a control surface. Initial cell adhesion, cell proliferation, cell differentiation, cell mineralization, and osteogenic related gene expression were examined on the TiO{sub 2} nanowire surfaces as compared to the control surfaces after 2 weeks of culturing. Cell adhesion and cell proliferation were assayed by field emission scanning electron microscope (FESEM) and Alamar Blue reduction assay, respectively. The nanowire surfaces promoted better cell adhesion and spreading than the control surface, as well as leading to higher cell proliferation. Our results showed that osteoblasts grown onto the TiO{sub 2} nanowire surfaces displayed significantly higher production levels of alkaline phosphatase (ALP), extracellular (ECM) mineralization and genes expression of runt-related transcription factor (Runx2), bone sialoprotein (BSP), ostoepontin (OPN) and osteocalcin (OCN) compared to the control surfaces. This suggests the potential use of such surface modification on Ti-6Al-4V substrates as a promising means to improve the osteointegration of titanium based implants.

  20. Optimisation of surface passivation for highly reliable angular AMR sensors

    Energy Technology Data Exchange (ETDEWEB)

    Isler, M.; Christoffer, B.; Schoer, G.; Philippsen, B.; Mahnke, M.; Thorns, A.; Riethmueller, W.; Matz, H.; Tobescu, C. [NXP Semiconductors, Stresemannallee 101, 22529 Hamburg (Germany); Vanhelmont, F.; Wolters, R. [NXP Semiconductors, High Tech Campus 4, 5656 AE Eindhoven (Netherlands); Engelen, R.; Opran, A. [Philips Applied Technologies, High Tech Campus 7, 5656 AE Eindhoven (Netherlands); Stolk, P. [NXP Semiconductors, Gerstweg 2, 6534 AE Nijmegen (Netherlands)

    2010-02-15

    For state-of-the-art angular sensors based on the anisotropic magnetoresistive (AMR) effect in NiFe layers, the angular accuracy over time is limited by a drift of the offset voltage of the Wheatstone bridge configuration. It is shown that the interaction of the passivation layer and the magnetic permalloy is crucial for the drift of the offset voltage. By investigating the time and temperature dependence, the offset drift is attributed to stress relief of the PECVD passivation layer due to microstructural changes. Hydrogen outdiffusion from the passivation layer is involved in the observed stress evolution. It is demonstrated that optimising the passivation layer composition as well as the time of the subsequent annealing is beneficial for stress stabilisation of the permalloy-passivation layer system. With this optimised passivation layer a significant offset drift reduction of the NiFe Wheatstone bridge has been achieved resulting in highly accurate and long-term stable angular AMR sensors. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. In-situ electrochemically active surface area evaluation of an open-cathode polymer electrolyte membrane fuel cell stack

    Science.gov (United States)

    Torija, Sergio; Prieto-Sanchez, Laura; Ashton, Sean J.

    2016-09-01

    The ability to evaluate the electrochemically active surface area (ECSA) of fuel cell electrodes is crucial toward characterising designs and component suites in-situ, particularly when evaluating component durability in endurance testing, since it is a measure of the electrode area available to take part in the fuel cell reactions. Conventional methods to obtain the ECSA using cyclic voltammetry, however, rely on potentiostats that cannot be easily scaled to simultaneously evaluate all cells in a fuel cell stack of practical size, which is desirable in fuel cell development. In-situ diagnostics of an open-cathode fuel cell stack are furthermore challenging because the cells do not each possess an enclosed cathode compartment; instead, the cathodes are rather open to the environment. Here we report on a diagnostic setup that allows the electrochemically active surface area of each cell anode or cathode in an open-cathode fuel cell stack to be evaluated in-situ and simultaneously, with high resolution and reproducibility, using an easily scalable chronopotentiometry methodology and a gas-tight stack enclosure.

  2. Landscape preservation under ice? In-situ 10Be and 26Al from summit surfaces along Sognefjord, Norway

    DEFF Research Database (Denmark)

    Andersen, Jane Lund; Egholm, David Lundbek; Knudsen, Mads Faurschou

    et al. Landscape preservation under Fennoscandian ice sheets determined from in situ produced 10 Be and 26 Al. Earth and Planetary Science Letters 201(2), 397-406, 2002. Gjermundsen et al. Minimal erosion of Arctic alpine topography during late Quaternary glaciation. Nature Geoscience 8(10), 789......In-situ cosmogenic nuclides demonstrate existence of landforms preserved under glacial ice in regions such as Northern Sweden (Fabel, 2002), Svalbard (Gjermundsen, 2015) and New England (Bierman, 2015). Elsewhere, the existence of relict landforms is inferred from landscape morphology. Low......-792, 2015. Nesje & Whillans. Erosion of Sognefjord, Norway. Geomorphology 9(1), 33-45, 1994. Steer et al. Bimodal Plio-Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia. Nature Geoscience 5(9), 635-639, 2012....

  3. Evaluation of OMI operational standard NO2 column retrievals using in situ and surface-based NO2 observations

    Directory of Open Access Journals (Sweden)

    L. N. Lamsal

    2014-11-01

    Full Text Available We assess the standard operational nitrogen dioxide (NO2 data product (OMNO2, version 2.1 retrieved from the Ozone Monitoring Instrument (OMI onboard NASA's Aura satellite using a combination of aircraft and surface in~situ measurements as well as ground-based column measurements at several locations and a bottom-up NOx emission inventory over the continental US. Despite considerable sampling differences, NO2 vertical column densities from OMI are modestly correlated (r = 0.3–0.8 with in situ measurements of tropospheric NO2 from aircraft, ground-based observations of NO2 columns from MAX-DOAS and Pandora instruments, in situ surface NO2 measurements from photolytic converter instruments, and a bottom-up NOx emission inventory. Overall, OMI retrievals tend to be lower in urban regions and higher in remote areas, but generally agree with other measurements to within ± 20%. No consistent seasonal bias is evident. Contrasting results between different data sets reveal complexities behind NO2 validation. Since validation data sets are scarce and are limited in space and time, validation of the global product is still limited in scope by spatial and temporal coverage and retrieval conditions. Monthly mean vertical NO2 profile shapes from the Global Modeling Initiative (GMI chemistry-transport model (CTM used in the OMI retrievals are highly consistent with in situ aircraft measurements, but these measured profiles exhibit considerable day-to-day variation, affecting the retrieved daily NO2 columns by up to 40%. This assessment of OMI tropospheric NO2 columns, together with the comparison of OMI-retrieved and model-simulated NO2 columns, could offer diagnostic evaluation of the model.

  4. DME Dissociation Reaction on Platinum Electrode Surface : A Quantitative Kinetic Analysis by In Situ IR Spectroscopy

    OpenAIRE

    Zhang, Yi; Tong, Yujin; Lu, Leilei; Osawa, Masatoshi; Ye, Shen

    2010-01-01

    The kinetics of electrocatalytic dissociation reaction of dimethyl ether (DME) on a platinum (Pt) polycrystalline electrode in an acidic solution yielding carbon monoxide (CO) has been quantitatively analyzed by in situ IR spectroscopy in the potential region between 100 and 500 mV (vs reversible hydrogen electrode). A two-step consecutive reaction model, an initial dehydrogenation step followed by a CO formation step, is proposed for the dissociation process of the DME molecule. The mechanis...

  5. In Situ Surface X-Ray Scattering of Metal Monolayers Adsorbed at Solid-Liquid Interfaces

    Science.gov (United States)

    1991-11-09

    important experimental aspects of’ these in-situ experiments are described, and after this, we explain underpotential electrochemical deposition (MPI...subtracted from the data in the calculation Of Qad" 3. UNDERPOTENTIAL DEPOSITION The electrochemical deposition of metal layers onto a foreign netal...for bulk deposition .1 5. 16 This process is termed underpotential deposition (UiPl)), and on single crystals, these initial deposits have been

  6. Laser direct writing of oxide structures on hydrogen-passivated silicon surfaces

    DEFF Research Database (Denmark)

    Müllenborn, Matthias; Birkelund, Karen; Grey, Francois;

    1996-01-01

    A focused laser beam has been used to induce oxidation of hydrogen-passivated silicon. The scanning laser beam removes the hydrogen passivation locally from the silicon surface, which immediately oxidizes in air. The process has been studied as a function of power density and excitation wavelengt...

  7. Effective passivation of Si surfaces by plasma deposited SiOx/a-SiNx:H stacks

    Science.gov (United States)

    Dingemans, G.; Mandoc, M. M.; Bordihn, S.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2011-05-01

    Very low surface recombination velocities field-effect passivation was absent for a reference stack comprising thermally grown SiO2. The results indicate that hydrogenation of interface states played a key role in the passivation and remained effective up to annealing temperatures >800 °C.

  8. Silicon surface and bulk defect passivation by low temperature PECVD oxides and nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z.; Rohatgi, A. [Georgia Institute of Technology, Atlanta, GA (United States). Univ. Center of Excellence for Photovoltaics Research and Education; Ruby, D. [Sandia National Labs., Albuquerque, NM (United States)

    1995-01-01

    The effectiveness of PECVD passivation of surface and bulk defects in Si, as well as phosphorous diffused emitters, Is investigated and quantified. Significant hydrogen incorporation coupled with high positive charge density in the PECVD SiN layer is found to play an important role in bulk and surface passivation. It is shown that photo-assisted anneal in a forming gas ambient after PECVD depositions significantly improves the passivation of emitter and bulk defects. PECVD passivation of phosphorous doped emitters and boron doped bare Si surfaces is found to be a strong function of doping concentration. Surface recombination velocity of less than 200 cm/s for 0.2 Ohm-cm and less than 1 cm/s for high resistivity substrates ({approximately} Ohm-cm) were achieved. PECVD passivation improved bulk lifetime in the range of 30% to 70% in multicrystalline Si materials. However, the degree of the passivation was found to be highly material specific. Depending upon the passivation scheme, emitter saturation current density (J{sub oe}) can be reduced by a factor of 3 to 9. Finally, the stability of PECVD oxide/nitride passivation under prolonged UV exposure is established.

  9. Dispersion analysis of passive surface-wave noise generated during hydraulic-fracturing operations

    Science.gov (United States)

    Forghani-Arani, Farnoush; Willis, Mark; Snieder, Roel; Haines, Seth S.; Behura, Jyoti; Batzle, Mike; Davidson, Michael

    2014-01-01

    Surface-wave dispersion analysis is useful for estimating near-surface shear-wave velocity models, designing receiver arrays, and suppressing surface waves. Here, we analyze whether passive seismic noise generated during hydraulic-fracturing operations can be used to extract surface-wave dispersion characteristics. Applying seismic interferometry to noise measurements, we extract surface waves by cross-correlating several minutes of passive records; this approach is distinct from previous studies that used hours or days of passive records for cross-correlation. For comparison, we also perform dispersion analysis for an active-source array that has some receivers in common with the passive array. The active and passive data show good agreement in the dispersive character of the fundamental-mode surface-waves. For the higher mode surface waves, however, active and passive data resolve the dispersive properties at different frequency ranges. To demonstrate an application of dispersion analysis, we invert the observed surface-wave dispersion characteristics to determine the near-surface, one-dimensional shear-wave velocity.

  10. Dependence of LTX plasma performance on surface conditions as determined by in situ analysis of plasma facing components

    Energy Technology Data Exchange (ETDEWEB)

    Lucia, M., E-mail: mlucia@pppl.gov [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ 08543 (United States); Kaita, R.; Majeski, R. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ 08543 (United States); Bedoya, F.; Allain, J.P. [University of Illinois at Urbana-Champaign (UIUC), Urbana, IL 61801 (United States); Abrams, T.; Bell, R.E.; Boyle, D.P.; Jaworski, M.A.; Schmitt, J.C. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ 08543 (United States)

    2015-08-15

    The Materials Analysis and Particle Probe (MAPP) diagnostic has been implemented on the Lithium Tokamak Experiment (LTX) at PPPL, providing the first in situ X-ray photoelectron spectroscopy (XPS) surface characterization of tokamak plasma facing components (PFCs). MAPP samples were exposed to argon glow discharge conditioning (GDC), lithium evaporations, and hydrogen tokamak discharges inside LTX. Samples were analyzed with XPS, and alterations to surface conditions were correlated against observed LTX plasma performance changes. Argon GDC caused the accumulation of nm-scale metal oxide layers on the PFC surface, which appeared to bury surface carbon and oxygen contamination and thus improve plasma performance. Lithium evaporation led to the rapid formation of a lithium oxide (Li{sub 2}O) surface; plasma performance was strongly improved for sufficiently thick evaporative coatings. Results indicate that a 5 h argon GDC or a 50 nm evaporative lithium coating will both significantly improve LTX plasma performance.

  11. Snowmelt and Surface Freeze/Thaw Timings over Alaska derived from Passive Microwave Observations using a Wavelet Classifier

    Science.gov (United States)

    Steiner, N.; McDonald, K. C.; Dinardo, S. J.; Miller, C. E.

    2015-12-01

    Arctic permafrost soils contain a vast amount of organic carbon that will be released into the atmosphere as carbon dioxide or methane when thawed. Surface to air greenhouse gas fluxes are largely dependent on such surface controls as the frozen/thawed state of the snow and soil. Satellite remote sensing is an important means to create continuous mapping of surface properties. Advances in the ability to determine soil and snow freeze/thaw timings from microwave frequency observations improves upon our ability to predict the response of carbon gas emission to warming through synthesis with in-situ observation, such as the 2012-2015 Carbon in Arctic Reservoir Vulnerability Experiment (CARVE). Surface freeze/thaw or snowmelt timings are often derived using a constant or spatially/temporally variable threshold applied to time-series observations. Alternately, time-series singularity classifiers aim to detect discontinuous changes, or "edges", in time-series data similar to those that occur from the large contrast in dielectric constant during the freezing or thaw of soil or snow. We use multi-scale analysis of continuous wavelet transform spectral gradient brightness temperatures from various channel combinations of passive microwave radiometers, Advanced Microwave Scanning Radiometer (AMSR-E, AMSR2) and Special Sensor Microwave Imager (SSM/I F17) gridded at a 10 km posting with resolution proportional to the observational footprint. Channel combinations presented here aim to illustrate and differentiate timings of "edges" from transitions in surface water related to various landscape components (e.g. snow-melt, soil-thaw). To support an understanding of the physical basis of observed "edges" we compare satellite measurements with simple radiative transfer microwave-emission modeling of the snow, soil and vegetation using in-situ observations from the SNOw TELemetry (SNOTEL) automated weather stations. Results of freeze/thaw and snow-melt timings and trends are

  12. SEM in-situ investigation on fatigue cracking behavior of P/M Rene95 alloy with surface inclusions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The low-cycle fatigue behavior of powder metallurgy Rene95 alloy containing surface inclusions was investigated by in-situ observation with scanning electron microscopy (SEM). The process of fatigue crack initiation and early stage of propagation behavior indicates that fatigue crack mainly occurs at the interface between the inclusion and the matrix. The effect of inclusion on the fatigue crack initiation and the early stage of crack growth was very obvious. The fatigue crack growth path in the matrix is similar to the shape of inclusion made on the basis of fatigue fracture image analysis. The empiric relation between the surface and inside crack growth length, near a surface inclusion, can be expressed. Therefore, the fatigue crack growth rate or life of P/M Rene95 alloy including the inclusions can be evaluated on the basis of the measurable surface crack length parameter. In addition, the effect of two inclusions on the fatigue crack initiation behavior was investigated by the in-situ observation with SEM.

  13. In situ delipidation of low-density lipoproteins in capillary electrochromatography yields apolipoprotein B-100-coated surfaces for interaction studies.

    Science.gov (United States)

    D'Ulivo, Lucia; Chen, Jie; Meinander, Kristoffer; Oörni, Katariina; Kovanen, Petri T; Riekkola, Marja-Liisa

    2008-12-01

    An electrochromatographic method was developed for the in situ delipidation of intact low-density lipoprotein (LDL) particles immobilized on the inner wall of a 50-microm inner diameter silica capillary. In this method, the immobilized LDL particles were delipidated with nonionic surfactant Nonidet P-40 at pH 7.4 and 25 degrees C, resulting in an apolipoprotein B-100 (apoB-100)-coated capillary surface. The mobility of the electroosmotic flow marker dimethyl sulfoxide gave information about the surface charge, and the retention factors of beta-estradiol, testosterone, and progesterone were informative of the surface hydrophobicity. The calculated distribution coefficients of the steroids produced specific information about the affinity interactions of the steroids, with capillary surfaces coated either with intact LDL particles or with apoB-100. Delipidation with Nonidet P-40 resulted in a strong decrease in the hydrophobicity of the LDL coating. Atomic force microscopy images confirmed the loss of lipids from the LDL particles and the presence of apoB-100 protein coating. The in situ delipidation of LDL particles in capillaries represents a novel approach for the isolation of immobilized apoB-100 and for the determination of its pI value. The technique requires extremely low quantities of LDL particles, and it is simple and fast.

  14. Retrieval of Sea Surface Salinity and Wind from The NASA Soil Moisture Active Passive Mission Data

    Science.gov (United States)

    Yueh, S. H.; Fore, A.; Tang, W.; Hayashi, A.

    2015-12-01

    NASA's Soil Moisture Active Passive (SMAP) mission, the first Earth Science Decadal Survey mission, was launched January 31, 2015 to provide high-resolution, frequent-revisit global mapping of soil moisture. SMAP has two instruments, a polarimetric radiometer and a multi-polarization synthetic aperture radar. Both instruments operate at L-band frequencies (~ 1GHz) and share a single 6-m rotating mesh antenna, producing a fixed incidence angle conical scan at 40⁰ across a 1000-km swath and a 2-3 day global revisit. The SMAP SSS and ocean surface wind retrieval algorithm developed at the Jet Propulsion Laboratory leverages the QuikSCAT and Aquarius algorithms to account for the two-look geometry (fore and aft looks from the conical scan) and dual-polarization observations for simultaneous retrieval of SSS and wind speed. The retrieval algorithm has been applied to more than three months of SMAP radiometer data. Comparison with the European Center for Medium-Range Weather Forecasting (ECMWF) wind speed suggests that the SMAP wind speed reaches an accuracy of about 0.7 ms-1. The preliminary assessment of the SMAP SSS products gridded at 50 km spatial resolution and weekly intervals is promising. The spatial patterns of the SSS agree well with climatological distributions, but exhibit several unique spatial and temporal features. The temporal evolutions of freshwater plumes from several major rivers, such as the Amazon, Niger, Congo, Ganges, and Mississippi, are all consistent with the timing of rainy and dry seasons, indicated in the SMAP's soil moisture products. Rigorous accuracy assessment will be performed by comparison with in situ SSS data from buoys and ARGO floats. The SMAP evaluation products will be released to the public prior to November 2015.

  15. NCEI-TSG: A Global in situ Sea-surface Salinity and Temperature Database of Thermosalinograph (TSG) Observations

    Science.gov (United States)

    Zhang, H. M.; Wang, Z.; Boyer, T.; Bayler, E. J.; Biddle, M.; Baker-Yeboah, S.; Zhang, Y.

    2016-12-01

    The NOAA National Centers for Environmental Information (NCEI) has constructed a Global Thermosalinograph Database (NCEI-TSG) to facilitate access to these in situ sea-surface salinity and temperature measurements. This database provides a comprehensive set of quality-controlled in situ sea-surface salinity (SSS) and temperature (SST) measurements collected from over 200 vessels during the period 1989 to the present. Compared to other TSG datasets, these data have several advantages. 1) The NCEI-TSG is the world's most complete TSG dataset, containing all data from the different TSG data assembly centers, e.g. Shipboard Automated Meteorological and Oceanographic System (SAMOS), Global Ocean Surface Underway Data (GOSUD) and Atlantic Oceanographic and Meteorological Laboratory (AOML), with more historical data from NCEI's archive to be added. 2) When different versions of a dataset are available, the dataset with the highest resolution is always chosen. 3) All data are converted to a common NetCDF format, employing enhanced metadata, following Attribute Convention for Dataset Discovery (ACDD) and Climate and Forecast (CF) conventions, to increase the overall quality and searchability of both the data and metadata. 4) All data are processed using the same 11-step quality control procedures and criteria and flagged using a two-level flag system to provide a well-organized, uniformly quality-controlled TSG dataset for the user community. The NCEI-TSG, a unique dataset for in situ sea-surface observations, serves as a significant resource for establishing match-ups with satellite SST and SSS observations for validation and comparisons. The NCEI-TSG database will significantly contribute to the in situ component of the NOAA Satellite SSS Quality Monitor (4SQM) project (under development). This dataset facilitates assessments of global SST and SSS variability and the analysis of patterns and trends at various regional and temporal scales, enabling new insights in climate

  16. Ordered arrays of semi-crown ligands on an Au(111) electrode surface:in situ STM study

    Institute of Scientific and Technical Information of China (English)

    PAN Gebo; LI Huijing; YUAN Qunhui; CHEN Yongjun; WAN Lijun; BAI Chunli

    2004-01-01

    In situ scanning tunneling microscopy (STM) and cyclic voltammetry were employed to investigate the adsorption structures of three semi-crown ligands on an Au(111) surface under the potential control. It is found that all the molecules formed ordered arrays in 0.1 mol/L HCIO4solution, although their geometric structures are complex and asymmetric. The driving force was supposed to come from the balance between intermolecular and molecule-substrate interactions.High resolution STM images revealed internal molecular structures, orientations and packing arrangements in the ordered adlayers. The results are useful for preparing ordered arrays of transition metal-mediated nanostructures.

  17. In situ structural study on underpotential deposition of Ag on Au(111) electrode using surface X-ray scattering technique

    OpenAIRE

    KONDO, Toshihiro; Morita, Jun; Okamura, Masayuki; Saito, Toshiya; Uosaki, Kohei

    2002-01-01

    In situ surface X-ray scattering (SXS) measurements were carried out to study the structure of a Ag layer on a Au(111) electrode formed by underpotential deposition (upd) in sulfuric acid solution. Specular rod profiles showed that a monolayer of Ag was formed at a potential between the second and third upd peaks, and a bilayer of Ag was formed at a potential between the third upd peak and bulk deposition. Non-specular rod profiles demonstrated that electrochemically deposited Ag atoms both i...

  18. Ambient pressure oxidation of Ag(111) surfaces : an in-situ X-ray study

    OpenAIRE

    Reicho, Alexander

    2008-01-01

    The oxidation of metals plays an outstanding role in everyday life. Typical phenomena are the formation of rust on steel or oxide scales on copper, showing up as a green patina. The formation of metal oxides is not always an unwanted process. The functionality of many materials is directly related to their controlled oxidation. The most prominent examples are passivating oxide layers on stainless steel. Relevant for this thesis are industrially applied heterogeneous catalytic reactions for th...

  19. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy.

    Science.gov (United States)

    Lee, J H; Tung, I C; Chang, S-H; Bhattacharya, A; Fong, D D; Freeland, J W; Hong, Hawoong

    2016-01-01

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  20. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. H.; Freeland, J. W.; Hong, Hawoong, E-mail: hhong@aps.anl.gov [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Tung, I. C. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Chang, S.-H.; Bhattacharya, A.; Fong, D. D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2016-01-15

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  1. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. H. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA; Tung, I. C. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA; Chang, S. -H. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Bhattacharya, A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Fong, D. D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Freeland, J. W. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA; Hong, Hawoong [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

    2016-01-01

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  2. In situ surface-enhanced Raman spectroscopic study of formic acid electrooxidation on spontaneously deposited platinum on gold.

    Science.gov (United States)

    Muralidharan, Ranjani; McIntosh, Michael; Li, Xiao

    2013-06-28

    Present formic acid fuel cell efficiency is limited by low kinetics at the anode, indicating the need for effective catalysts to improve the formic acid oxidation. As a prerequisite, the nature of adsorbed species and specifically the reaction intermediates formed in this process needs to be examined. This work focuses on the electrooxidation of formic acid and the nature of the intermediates at a platinum-modified gold surface prepared through spontaneous deposition using a combination of electrochemistry and in situ surface enhanced Raman spectroscopy (SERS). This Pt-modified gold electrode surface assists in oxidizing formic acid at potentials as low as 0.0 V vs. Ag/AgCl which is 0.15 V more negative than a bare Pt surface. The oxidation current obtained on the Pt-modified gold electrode is 72 times higher than on a bare Au surface and 5 times higher than on a bare Pt surface at the same potential. In situ SERS has revealed the involvement of formate at a low frequency as the primary intermediate in this electrooxidation process. While previous studies mainly focused on the formate mode at ca. 1322 cm(-1), it is the first time that a formate peak at ca. 300 cm(-1) was observed on a Pt or Pt-associated surface. A unique relationship has been observed between the formic acid oxidation currents and the SERS intensity of this formate adsorbate. Furthermore, the characteristic Stark effect of the formate proves the strong interaction between the adsorbate and the catalyst. Both electrochemical and spectroscopic results suggest that the formic acid electrooxidation takes place by the dehydrogenation pathway involving a low frequency formate intermediate on the Pt-modified gold electrode catalyst.

  3. Fine-scale features on the sea surface in SAR satellite imagery – Part 1: Simultaneous in-situ measurements

    Directory of Open Access Journals (Sweden)

    S. Brusch

    2012-09-01

    Full Text Available This work is aimed at identifying the origin of fine-scale features on the sea surface in synthetic aperture radar (SAR imagery with the help of in-situ measurements as well as numerical models (presented in a companion paper. We are interested in natural and artificial features starting from the horizontal scale of the upper ocean mixed layer, around 30–50 m. These features are often associated with three-dimensional upper ocean dynamics. We have conducted a number of studies involving in-situ observations in the Straits of Florida during SAR satellite overpass. The data include examples of sharp frontal interfaces, wakes of surface ships, internal wave signatures, as well as slicks of artificial and natural origin. Atmospheric processes, such as squall lines and rain cells, produced prominent signatures on the sea surface. This data has allowed us to test an approach for distinguishing between natural and artificial features and atmospheric influences in SAR images that is based on a co-polarized phase difference filter.

  4. Electrical properties of GaAs metal-oxide-semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal-organic vapor deposition/atomic layer deposition hybrid system

    Science.gov (United States)

    Aoki, Takeshi; Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2015-08-01

    This paper presents a compressive study on the fabrication and optimization of GaAs metal-oxide-semiconductor (MOS) structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD), with an AlN interfacial passivation layer prepared in situ via metal-organic chemical vapor deposition (MOCVD). The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA) conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance-voltage (C-V) characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit) near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm-2 eV-1. Using a (111)A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  5. Electrical properties of GaAs metal–oxide–semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal–organic vapor deposition/atomic layer deposition hybrid system

    Directory of Open Access Journals (Sweden)

    Takeshi Aoki

    2015-08-01

    Full Text Available This paper presents a compressive study on the fabrication and optimization of GaAs metal–oxide–semiconductor (MOS structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD, with an AlN interfacial passivation layer prepared in situ via metal–organic chemical vapor deposition (MOCVD. The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance–voltage (C–V characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm−2 eV−1. Using a (111A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  6. Osteogenic potential of in situ TiO2 nanowire surfaces formed by thermal oxidation of titanium alloy substrate

    Science.gov (United States)

    Tan, A. W.; Ismail, R.; Chua, K. H.; Ahmad, R.; Akbar, S. A.; Pingguan-Murphy, B.

    2014-11-01

    Titanium dioxide (TiO2) nanowire surface structures were fabricated in situ by a thermal oxidation process, and their ability to enhance the osteogenic potential of primary osteoblasts was investigated. Human osteoblasts were isolated from nasal bone and cultured on a TiO2 nanowires coated substrate to assess its in vitro cellular interaction. Bare featureless Ti-6Al-4V substrate was used as a control surface. Initial cell adhesion, cell proliferation, cell differentiation, cell mineralization, and osteogenic related gene expression were examined on the TiO2 nanowire surfaces as compared to the control surfaces after 2 weeks of culturing. Cell adhesion and cell proliferation were assayed by field emission scanning electron microscope (FESEM) and Alamar Blue reduction assay, respectively. The nanowire surfaces promoted better cell adhesion and spreading than the control surface, as well as leading to higher cell proliferation. Our results showed that osteoblasts grown onto the TiO2 nanowire surfaces displayed significantly higher production levels of alkaline phosphatase (ALP), extracellular (ECM) mineralization and genes expression of runt-related transcription factor (Runx2), bone sialoprotein (BSP), ostoepontin (OPN) and osteocalcin (OCN) compared to the control surfaces. This suggests the potential use of such surface modification on Ti-6Al-4V substrates as a promising means to improve the osteointegration of titanium based implants.

  7. In situ synchrotron IR study relating temperature and heating rate to surface functional group changes in biomass.

    Science.gov (United States)

    Kirtania, Kawnish; Tanner, Joanne; Kabir, Kazi Bayzid; Rajendran, Sharmen; Bhattacharya, Sankar

    2014-01-01

    Three types of woody biomass were investigated under pyrolysis condition to observe the change in the surface functional groups by Fourier transform infrared (FTIR) technique with increasing temperature under two different (5 and 150°C/min) heating rates. The experiments were carried out in situ in the infrared microscopy beamline (IRM) of the Australian Synchrotron. The capability of the beamline made it possible to focus on single particles to obtain low noise measurements without mixing with KBr. At lower heating rate, the surface functional groups were completely removed by 550°C. In case of higher heating rate, a delay was observed in losing the functional groups. Even at a high temperature, significant number of functional groups was retained after the higher heating rate experiments. This implies that at considerably high heating rates typical of industrial reactors, more functional groups will remain on the surface.

  8. Ex situ and in situ characterization of patterned photoreactive thin organic surface layers using friction force microscopy.

    Science.gov (United States)

    Shen, Quan; Edler, Matthias; Griesser, Thomas; Knall, Astrid-Caroline; Trimmel, Gregor; Kern, Wolfgang; Teichert, Christian

    2014-01-01

    Photolithographic methods allow an easy lateral top-down patterning and tuning of surface properties with photoreactive molecules and polymers. Employing friction force microscopy (FFM), we present here different FFM-based methods that enable the characterization of several photoreactive thin organic surface layers. First, three ex situ methods have been evaluated for the identification of irradiated and non-irradiated zones on the same organosilane sample by irradiation through different types of masks. These approaches are further extended to a time dependent ex situ FFM measurement, which allows to study the irradiation time dependent evolution of the resulting friction forces by sequential irradiation through differently sized masks in crossed geometry. Finally, a newly designed in situ FFM measurement, which uses a commercial bar-shaped cantilever itself as a noncontact shadow mask, enables the determination of time dependent effects on the surface modification during the photoreaction.

  9. Silicon surface passivation using thin HfO2 films by atomic layer deposition

    Science.gov (United States)

    Gope, Jhuma; Vandana; Batra, Neha; Panigrahi, Jagannath; Singh, Rajbir; Maurya, K. K.; Srivastava, Ritu; Singh, P. K.

    2015-12-01

    Hafnium oxide (HfO2) is a potential material for equivalent oxide thickness (EOT) scaling in microelectronics; however, its surface passivation properties particularly on silicon are not well explored. This paper reports investigation on passivation properties of thermally deposited thin HfO2 films by atomic layer deposition system (ALD) on silicon surface. As-deposited pristine film (∼8 nm) shows better passivation with <100 cm/s surface recombination velocity (SRV) vis-à-vis thicker films. Further improvement in passivation quality is achieved with annealing at 400 °C for 10 min where the SRV reduces to ∼20 cm/s. Conductance measurements show that the interface defect density (Dit) increases with film thickness whereas its value decreases after annealing. XRR data corroborate with the observations made by FTIR and SRV data.

  10. In Situ Thermal Imagery of Antarctic Meteorites and Their Stability on the Ice Surface

    Science.gov (United States)

    Harvey, R. P.; Righter, M.; Karner, J. M.; Hyneck, B.; Keller, L.; Meshik, A.; Mittlefehldt, D.; Radebaugh, J.; Rougeux, B.; Schutt, J.

    2017-01-01

    The mechanisms behind Antarctic meteorite concentrations remain enigmatic nearly 5 decades after the first recoveries, and much of the research in this direction has been based on anedcotal evidence. While these observations suggest many plausible processes that help explain Antarctic meteorite concentrations, the relative importance of these various processes (which can result in either an increase or decrease of specimens) is a critical component of any more robust model of how these concentrations form. During the 2016-2017 field season of the US Antarctic Search for Meteorites program we aquired in situ thermal imagery of meteorites specimens that provide semi-quantitative assesment of the relative temperature of these specimens and the ice. These provide insight into one hypothesized loss mechanism, the downward thermal tunnelling of meteorites warmed in the sun.

  11. In situ surface and interface study of crystalline (3×1)-O on InAs

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Xiaoye, E-mail: xxq102020@utdallas.edu; Wallace, Robert M., E-mail: rmwallace@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Wang, Wei-E.; Rodder, Mark S. [Advanced Logic Lab, Samsung Semiconductor, Inc., Austin, Texas 78754 (United States)

    2016-07-25

    The oxidation behavior of de-capped InAs (100) exposed to O{sub 2} gas at different temperatures is investigated in situ with high resolution of monochromatic x-ray photoelectron spectroscopy and low energy electron diffraction. The oxide chemical states and structure change dramatically with the substrate temperature. A (3 × 1) crystalline oxide layer on InAs is generated in a temperature range of 290–330 °C with a coexistence of In{sub 2}O and As{sub 2}O{sub 3}. The stability of the crystalline oxide upon the atomic layer deposition (ALD) of HfO{sub 2} is studied as well. It is found that the generated (3 × 1) crystalline oxide is stable upon ALD HfO{sub 2} growth at 100 °C.

  12. DOTS: A High Resolution Orbitrap Mass Spectrometer for In Situ Analysis of the surface samples of Airless Planetary Bodies

    Science.gov (United States)

    Briois, Christelle; Thissen, Roland; Engrand, Cécile; Altwegg, Kathrin; Bouabdellah, Abdel; Boukrara, Amirouche; Carrasco, Nathalie; Chapuis, Claude; Cottin, Hervé; Grün, Eberhard; Grand, Noel; Henkel, Hartmut; Kempf, Sascha; Lebreton, Jean-Pierre; Makarov, Alexander A.; Postber, Frank; Srama, Ralf; Schmidt, Jürgen; Szopa, Cyril; Thirkell, Laurent; Tobie, Gabriel; Wurz, Peter; Zolotov, Mikhail Yu

    2013-04-01

    The dust detectors on board the Ulysses and Galileo spacecraft have shown that the Galilean satellites are surrounded by clouds of sub-micrometer size grains generated by impacts of interplanetary (micro-) meteoroids [1, 2]. In situ chemical analysis from orbit of these ballistic grains ejected from the surface of airless bodies provides a unique opportunity to remotely access the chemical composition of the Jovian moons' surface and subsurface. For Saturn, in situ identification by the Cassini Dust Analyzer (CDA) of sodium in icy grains in the E-Ring and in Enceladus plumes have proven a subsurface liquid water reservoir inside Enceladus [3, 4]. Noticeably, this was not accessible to other in situ or traditional remote sensing techniques. In situ measurements, either during a flyby or from orbit, of grains ejected from the surface, or emerging from the subsurface, of an airless body is a powerful tool to remotely study its surface composition and the nature of its geological activity. Crucial constraints on habitability can thus be determined. Our consortium of laboratories, in collaboration with Thermo Fischer Scientific [5, 6], is currently developing a high mass resolution Fourier Transform (FT) Orbitrap-based mass spectrometer optimized for in situ analysis of dust and icy grains in the environment of Solar System airless bodies. This new generation of dust mass spectrometer was studied in the framework of the Europa Jupiter System Mission (EJSM) instrument study in 2010-2012 and proposed in response to ESA's AO for the JUpiter ICy moons Explorer (JUICE) mission [7]. This mass analyser can provide very high mass resolution analysis (M/ΔM reaching 50 000 at m/z 50 Da). DOTS would allow identification of elemental and molecular species with excellent accuracy, in the 20-1000 Da mass range. In the context of the JUICE mission, DOTS would provide decisive information on the surface composition and on the putative liquid oceans in the subsurface of Ganymede

  13. Mobile Geochemistry Instrument Package Facility (MGIPF) for In Situ Mineralogical and Chemical Analysis of Planetary Surface Material

    Science.gov (United States)

    Klingelhöfer, G.; Romstedt, J.; Henkel, H.; Michaelis, H.; Brückner, J.; D'Uston, C.

    A first order requirement for any spacecraft mission to land on a solid planetary or moon surface is instrumentation for in-situ mineralogical and chemical analysis 2 Such analysis provide data needed for primary classification and characterization of surface materials present We will discuss a mobile instrument package we have developed for in-situ investigations under harsh environmental conditions like on Mercury or Mars This Geochemistry Instrument Package Facility is a compact box also called payload cab containing three small advanced geochemistry mineralogy instruments the chemical spectrometer APXS the mineralogical M o ssbauer spectrometer MIMOS II 3 and a textural imager close-up camera The payload cab is equipped with two actuating arms with two degrees of freedom permitting precision placement of all instruments at a chosen sample This payload cab is the central part of the small rover Nanokhod which has the size of a shoebox 1 The Nanokhod rover is a tethered system with a typical operational range of sim 100 m Of course the payload cab itself can be attached by means of its arms to any deployment device of any other rover or deployment device 1 Andre Schiele Jens Romstedt Chris Lee Sabine Klinkner Rudi Rieder Ralf Gellert G o star Klingelh o fer Bodo Bernhardt Harald Michaelis The new NANOKHOD Engineeering model for extreme cold environments 8th International symposium on Artificial Intelligence Robotics and Automation in Space 5 - 9 September 2005

  14. Covalently-layers of PVA and PAA and in situ formed Ag nanoparticles as versatile antimicrobial surfaces.

    Science.gov (United States)

    Fragal, Vanessa H; Cellet, Thelma S P; Pereira, Guilherme M; Fragal, Elizângela H; Costa, Marco Antonio; Nakamura, Celso Vataru; Asefa, Tewodros; Rubira, Adley F; Silva, Rafael

    2016-10-01

    The in situ synthesis of silver nanoparticles (AgNPs) within covalently-modified poly(ethylene terephthalate) (PET) films possessing ultra-thin layer of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) is successfully demonstrated. The resulting polymeric films are shown to exhibit antimicrobial activities toward Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and fungus (Candida albicans). To make the films, first PET surfaces were subject to photo-oxidation and subsequent solid-state grafting to attach a PVA layer, followed by a PAA layer. To synthesize the AgNPs inside the films, the PVA and PAA-modified PET was soaked in AgNO3 solution and the polymeric film was modified with the Ag(+) ions via Ag(+)-carboxylate interaction, and then the Ag(+) ions-containing polymer film was subject to either photo-reduction or thermal reduction processes. The PVA and PAA thin layers attached by covalent bonds to the PET surface uniquely promoted not only the in situ synthesis but also the stabilization of AgNPs. The formation of the AgNPs was confirmed by UV-vis spectroscopy or by monitoring the surface plasmon resonance (SPR) peak associated with AgNPs. The resulting PVA and PAA ultrathin layers modified and AgNPs containing PET served as bactericide and fungicide, inhibiting the growth of bacteria and fungi on the surfaces. Given PET's versatility and common use in many commercial processes, the method can be used for producing plastic surfaces with versatile antimicrobial and antibacterial properties.

  15. Mesoscale Elucidation of Surface Passivation in the Li-Sulfur Battery Cathode.

    Science.gov (United States)

    Liu, Zhixiao; Mukherjee, Partha P

    2017-02-15

    The cathode surface passivation caused by Li2S precipitation adversely affects the performance of lithium-sulfur (Li-S) batteries. Li2S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li2S film on carbon cathode surface. Li2S film growth experiences nucleation, isolated Li2S island growth and island coalescence. The slow adsorption rate at small S(2-) concentration inhibits the formation of nucleation seeds and the lateral growth of Li2S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li2S nucleation seeds form in such an operating temperature range, thereby facilitating heterogeneous growth and potentially inhibiting the lateral growth of the Li2S film, which may ultimately result in reduced surface passivation. The high specific surface area of the cathode microstructure is expected to mitigate the surface passivation.

  16. Analysis of CO2 convection mechanisms associated to surface heating, by combining remote sensing data and in situ measurements

    Science.gov (United States)

    Tello, Marivi; Curcoll, Roger; Font, Anna; Morgu, Josep Anton; Rod, Xavier

    Assessing the mechanisms involved in the variability of carbon fluxes is crucial for the under-standing of the changing earth dynamics. In that sense, the aim of this work is to analyze CO2 convection mechanisms at a regional scale in the boundary layer and the lower troposphere by means of cross correlation of land surface temperature data, radio-soundings, wind speeds and in situ measurements of CO2 atmospheric mixing ratios. Since data is easier to acquire, ground level horizontal CO2 fluxes have been widely studied. In the contrary, vertical ones are still subject to uncertainties, even if they are necessary to understand 3D CO2 variability in the atmosphere. In particular, this paper focuses on the relationship between surface heating, convection and CO2 concentrations at different heights and, more generally, on the energy transfer between the surface and the air. The monitored area corresponds to a region on the North Eastern Iberian Peninsula, mainly devoted to agricultural activities. Different types of land covers are observed. On the one hand, in situ data has been collected by several flights during 2007 along the parallel 42o N following the "Crown" aircraft sampling approach [1] that integrates CO2 data obtained through horizontal transects and vertical profiles. This particular configuration is especially well suited for the evaluation of both horizontal and vertical CO2 fluxes. On the other hand, the radiometric land surface temperatures are obtained from the MODIS instrument onboard the Terra and the Aqua satellites. Besides, a flight campaign with an airborne sensor along the same transect in the parallel 42o N has been proposed in the scope of the MIDAS-6 project recently submitted. This project plans to improve soil moisture and ocean salinity products of the SMOS sensor recently launched and to demonstrate its applications. This will allow the study of moisture patterns in the monitored area at two different scales: that of the data collected

  17. The Regional Surface Heating Field over the Heterogeneous Landscape of the Tibetan Plateau Using MODIS and In-Situ Data

    Institute of Scientific and Technical Information of China (English)

    MA Yaoming; WANG Binbin; ZHONG Lei; MA Weiqiang

    2012-01-01

    In this study,a parameterization scheme based on Moderate Resolution Imaging Spectroradiometer (MODIS) data and in-situ data was tested for deriving the regional surface heating field over a heterogeneous landscape.As a case study,the methodology was applied to the whole Tibetan Plateau (TP) area.Four images of MODIS data (i.e.,30 January 2007,15 April 2007,1 August 2007,and 25 October 2007) were used in this study for comparison among winter,spring,summer,and autumn.The results were validated using the observations measured at the stations of the Tibetan Observation and Research Platform (TORP).The results show the following:(1) The derived surface heating field for the TP area was in good accord with the land-surface status,showing a wide range of values due to the strong contrast of surface features in the area.(2) The derived surface heating field for the TP was very close to the field measurements (observations).The APD (absolute percent difference) between the derived results and the field observations was <10%.(3) The mean surface heating field over the TP increased from January to April to August,and decreased in October.Therefore,the reasonable regional distribution of the surface heating field over a heterogeneous landscape can be obtained using this methodology.The limitations and further improvement of this method are also discussed.

  18. Fate of the herbicides 2,4,5-T, atrazine, and DNOC in a shallow, anaerobic aquifer investigated by in situ passive diffusive emitters and laboratory batch experiments

    DEFF Research Database (Denmark)

    Arildskov, N.P.; Pedersen, Philip Grinder; Albrechtsen, Hans-Jørgen

    2001-01-01

    The fate of the three herbicides 2,4,5-T (2,4,5-trichlorophenoxyacetic acid), atrazine (6-chloro-N-ethyl-N'-[1-methyl-ethyl]-1,3,5-triazine-2,4-diamine), and DNOC (4,6-dinitro-2-methylphenol) in an anaerobic sandy aquifer was investigated. In the field, each of the herbicides was released...... simultaneously with tritiated water (HTO) as tracer in the depth interval 3 to 4 rubs (meters below surface) by use of passive diffusive emitters. Atrazine and 2,4,5-T were persistent during the approximately 18 days residence time in the aquifer. In contrast, DNOC was rapidly removed from the water phase....... In the other 2,4,5-T incubations and all the atrazine incubations, concentrations decreased linearly, but less than 25% was removed within 200 to 250 days. No degradation products could be detected, and slow sorption was the likely explanation. In all the laboratory incubations DNOC was degraded, following...

  19. Surface effects after a combination of dental bleaching and enamel microabrasion: An in vitro and in situ study.

    Science.gov (United States)

    Franco, Laura Molinar; Machado, Lucas Silveira; Salomão, Fabio Martins; Dos Santos, Paulo Henrique; Briso, André Luiz Fraga; Sundfeld, Renato Herman

    2016-01-01

    This study evaluated the effects of combining enamel microabrasion and dental bleaching on the physical properties of enamel, using in vitro and in situ conditions and evaluating surface roughness, enamel microhardness and scanning electron microscopy images. One hundred sound bovine teeth were sectioned and cut into discs and randomly divided into 10 study groups (n=10). The results were submitted to Analysis of Variance (ANOVA) for repeated measures, followed by the Tukey test, with significance at 5%. Enamel surface roughness was significantly influenced by microabrasion, regardless of being combined with dental bleaching, for both HS (Human Saliva) or AS (Artificial Saliva) condition. Enamel microhardness was significantly decreased in the groups in which enamel microabrasion was performed, regardless its combination with dental bleaching; although storage in HS reestablished the initial enamel microhardness. It was concluded that dental bleaching does not cause major damage to microabraided enamel, and that only human saliva recovered the initial enamel microhardness.

  20. In situ surface treatment of nanocrystalline MFe2O4 (M = Co, Mg, Mn, Ni) spinel ferrites using linseed oil

    Science.gov (United States)

    Gherca, Daniel; Cornei, Nicoleta; Mentré, Olivier; Kabbour, Houria; Daviero-Minaud, Sylvie; Pui, Aurel

    2013-12-01

    This paper reports the synthesis by coprecipitation method of MFe2O4 nanoparticles using linseed oil as the in-situ surfactant. The decomposition process of the precursors and the formation process of MFe2O4 were investigated by thermogravimetric analysis and differential thermal analysis (TG-DTA). The crystal structure and surface morphology were examined by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis. The results demonstrate that the surface of MFe2O4 with a diameter in the range 5-13 nm, is activated with hydrophilic groups of the surfactant which coat them and enhance the stability. Magnetic properties are discussed.

  1. Facile in situ characterization of gold nanoparticles on electrode surfaces by electrochemical techniques: average size, number density and morphology determination.

    Science.gov (United States)

    Wang, Ying; Laborda, Eduardo; Salter, Chris; Crossley, Alison; Compton, Richard G

    2012-10-21

    A fast and cheap in situ approach is presented for the characterization of gold nanoparticles from electrochemical experiments. The average size and number of nanoparticles deposited on a glassy carbon electrode are determined from the values of the total surface area and amount of gold obtained by lead underpotential deposition and by stripping of gold in hydrochloric acid solution, respectively. The morphology of the nanoparticle surface can also be analyzed from the "fingerprint" in lead deposition/stripping experiments. The method is tested through the study of gold nanoparticles deposited on a glassy carbon substrate by seed-mediated growth method which enables an easy control of the nanoparticle size. The procedure is also applied to the characterization of supplied gold nanoparticles. The results are in satisfactory agreement with those obtained via scanning electron microscopy.

  2. Integrated in situ characterization of molten salt catalyst surface: Evidence of sodium peroxide and OH radical formation

    KAUST Repository

    Takanabe, Kazuhiro

    2017-06-26

    Na-based catalysts (i.e., Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces due to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometer, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, has been identified on the outer surfaces at temperatures ≥800°C, and these species are useful for various gas-phase hydrocarbon reactions including the selective transformation of methane to ethane.

  3. Comparison of seasonal variability of Aquarius sea surface salinity time series with in situ observations in the Karimata Strait, Indonesia

    Science.gov (United States)

    Susanto, R. D.; Setiawan, A.; Zheng, Q.; Sulistyo, B.; Adi, T. R.; Agustiadi, T.; Trenggono, M.; Triyono, T.; Kuswardani, A.

    2016-12-01

    The seasonal variability of a full lifetime of Aquarius sea surface salinity time series from August 25, 2011 to June 7, 2015 is compared to salinity time series obtained from in situ observations in the Karimata Strait. The Karimata Strait plays dual roles in water exchange between the Pacific and the Indian Ocean. The salinity in the Karimata Strait is strongly affected by seasonal monsoon winds. During the boreal winter monsoon, northwesterly winds draws low salinity water from the South China Sea into the Java Sea and at the same time, the Java Sea receives an influx of the Indian Ocean water via the Sunda Strait. The Java Sea water will reduce the main Indonesian throughflow in the Makassar Strait. Conditions are reversed during the summer monsoon. Low salinity water from the South China Sea also controls the vertical structure of water properties in the upper layer of the Makassar Strait and the Lombok Strait. As a part of the South China Sea and Indonesian Seas Transport/Exchange (SITE) program, trawl resistance bottom mounted CTD was deployed in the Karimata Strait in mid-2010 to mid-2016 at water depth of 40 m. CTD casts during the mooring recoveries and deployments are used to compare the bottom salinity data. This in situ salinity time series is compared with various Aquarius NASA salinity products (the level 2, level 3 ascending and descending tracks and the seven-days rolling averaged) to check the consistency, correlation and statistical analysis. The preliminary results show that the seasonal variability of Aquarius salinity time series has larger amplitude variability compared to that of in situ data.

  4. In Situ Studies of Surface Mobility on Noble Metal Model Catalysts Using STM and XPS at Ambient Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Butcher, Derek Robert [Univ. of California, Berkeley, CA (United States)

    2010-06-01

    are present on the Pt(100) hex reconstructed phase, but not the (100)-(1x1) surface. The increase in ethylene pressure caused the adsorbate interactions to dominate the crystal morphology and imposed a surface layer structure that matched the ethylidyne binding geometry. The STM results also showed that the surface was reversibly deformed during imaging due to increases in Pt mobility at high pressure. The size dependence on the activity and surface chemistry of Rh nanoparticles was studied using AP-XPS. The activity was found to increase with particle size. The XPS spectra show that in reaction conditions the particle surface has an oxide layer which is chemically distinct from the surface structure formed by heating in oxygen alone. This surface oxide which is stabilized in the catalytically active CO oxidation conditions was found to be more prevalent on the smaller nanoparticles. The reaction-induced surface segregation behavior of bimetallic noble metal nanoparticles was observed with APXPS. Monodisperse 15 nm RhPd and PdPt nanoparticles were synthesized with well controlled Rh/Pd and Pd/Pt compositions. In-situ XPS studies showed that at 300 C in the presence of an oxidizing environment (100 mTorr NO or O2) the surface concentration of the more easily oxidized element (Rh in RhPd and Pd in PdPt) was increased. Switching the gas environment to more reducing conditions (100 mTorr NO and 100 mTorr CO) caused the surface enrichment of the element with the lowest surface energy in its metallic state. Using in-situ characterization, the redox chemistry and the surface composition of bimetallic nanoparticle samples were monitored in reactive conditions. The particle surfaces were shown to reversibly restructure in response to the gas environment at high temperature. The oxidation behavior of the Pt(110) surface was studied using surface sensitive in-situ characterization by APXPS and STM. In the presence of 500 mTorr O2 and temperatures between 25

  5. In-situ Observation of Boiling Dynamics on Fuel Cladding Surface in Non-pressurized Water Using Acoustic Emission Method

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Kaige; Baek, Seung Heon; Shim, Hee-Sang; Hur, Do Haeng; Lee, Deok Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    In the PWR primary coolant system, a phenomenon of axial offset anomaly (AOA) can be caused due to accumulated boron hide out in porous CRUD deposition on the fuel cladding surface. Up to now, the CRUD deposition has been well known to be driven by subcooled nucleate boiling (SNB) on the cladding surface based on large scale experimental work. Therefore, monitoring and evaluation of the SNB-phenomenon is an important approach to study the CRUD deposition. Many attempts have been made to study the SNB and CRUD deposition using thermal hydraulic or model calculation. However, a comprehensive understanding of the SNB during CRUD deposition is still far from being realized. Acoustic emission (AE) technique, as an in-situ nondestructive evaluation (NDE) method, has been widely used to monitor the boiling activity in containers and pipes. Accordingly, this work aimed to investigate the exact AE characteristics of SNB-phenomenon on the fuel cladding surface at atmospheric pressure, with the purpose of providing an experimental groundwork for the AE investigation on SNB in high-temperature pressurized coolant system. In this study, we conducted an in-situ experimental observation of the bubble dynamic of SNB in non-pressurized water at atmospheric pressure using AE method. The AE of heater noise was confirmed to cluster between 8 and 26 khz. Three AE groups were detected during the boiling process in the Snob zones. AE group 1 and 3 seemed to be the results of bubble growth and collapse, while bubble departure from the cladding surface was reasonably associated with an isolated AE group 2.

  6. Performance of a Microfluidic Device for In Situ ToF-SIMS Analysis of Selected Organic Molecules at Aqueous Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Li; Zhu, Zihua; Yu, Xiao-Ying; Thevuthasan, Suntharampillai; Cowin, James P.

    2013-04-03

    Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a unique surface analysis technique because it can provide molecular recognition for organic and biological molecules. However, analyzing aqueous solution surfaces by ToF-SIMS is difficult, because ToF-SIMS is a high-vacuum technique, while the vapor pressure of water is about 2.3 kPa at room temperature (20 C). We designed and fabricated a self-contained microfluidic device, enabling in situ analysis of aqueous surfaces by scanning electron microscope (SEM) and ToF-SIMS, which has been briefly reported.1,2 In this study, we report more performance data, focusing on the performance of this device for in situ analysis of organic molecules at aqueous surfaces using ToF-SIMS. Three representative organic compounds (formic acid, glycerol, and glutamic acid) were tested, and their molecular signals were successfully observed. The device can be self-running in vacuum for 8 hours, and SIMS measurements are feasible at any time in this time range. The stability of this device under primary ion beam bombardment is also impressive. High fluence (6 × 1012 ions cm-2 s-1) measurements can be operated continuously for up to 30 minutes without any significant damage to the aperture. However, extra-high fluence measurements (>1 × 1014 ions cm-2 s-1) may lead to liquid bumping in the aperture, and the aqueous solutions may spread out quickly. Signal reproducibility is reasonably good, and relative standard deviation (RSD) for molecular ion signals can be controlled to be smaller than ±15% for consecutive measurements. Measurements at long time intervals (e.g., 60 min) show RSDs of ±40-50%. In addition, the detection limits of formic acid, glycerol, and glutamic acid are estimated to be 0.04%, 0.008%, and 0.002% (weight ratio), respectively.

  7. In-situ surface wettability parameters of submerged in brackish water surfaces derived from captive bubble contact angle studies as indicators of surface condition level

    Science.gov (United States)

    Pogorzelski, S. J.; Mazurek, A. Z.; Szczepanska, A.

    2013-06-01

    The characterization of wetting properties (by contact angles) of several undersea artificial (glass plates,) and natural (stones, sand layers, soft-bottom structures, aquatic macrophytes, sediments, and seafloor communities) solid substrata in the Baltic Sea brackish water (Gulf of Gdansk). The studies were performed under laboratory and field conditions using a novel captive bubble air-pipette computer microscope system. A set of the surface wettability parameters: the apparent surface free energy γSV, adhesive layer film pressure Π, work of adhesion WA, and work of spreading WS were determined to quantify the wetting properties of model substrata using the contact angle hysteresis (CAH) approach. The useful technique to measure in situ the contact angle giving reproducible and accurate values of CA turned out to be a captive bubble method, for fully hydrated interfacial layers of highly hydrophilic and porous nature met at seabed (Rodrigues-Valverde et al., 2002). CA measurements revealed mostly hydrophilic nature of the studied solid material (CA oil film covering lead to surface hydrophobization (CA↑, γSV ↓,WA↓, WS more negative). The adhesion of biofouling was correlated both with CAH and the dispersive interaction term γSVd of the total γSV. Monitoring of the artificial substrata of the hydrophilic nature with a CA technique can be used to observe the development of the organisms community i.e., microfouling, and to carry out a comprehensive study of surfaces of the submerged macrophytes (Potamogeton lucens in particular). Since aquatic macrophytes can act as bio-indicators of water chemistry their surface wettability may reflect plant surface erosion and organic matter accumulation state being of particular value in biological assessment of ecosystems status.

  8. Effects of molybdenum on the composition and nanoscale morphology of passivated austenitic stainless steel surfaces.

    Science.gov (United States)

    Maurice, Vincent; Peng, Hao; Klein, Lorena H; Seyeux, Antoine; Zanna, Sandrine; Marcus, Philippe

    2015-01-01

    Surface analysis by time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and scanning tunnelling microscopy has been applied to provide new insight on Mo effects on the composition and nanostructure of the passive films grown in sulfuric acid on well-controlled Fe-17Cr-14.5Ni-2.3Mo(100) austenitic stainless steel single crystal surfaces. A duplex hydroxylated oxide matrix, 1.8-1.9 nm thick, is formed with a strong partition between Cr(iii) and Fe(iii) in the inner and outer layers, respectively. Cr(iii) is increasingly enriched by preferential iron oxide dissolution upon passivation and ageing. Ni, only present as oxide traces in the film, is enriched in the alloy underneath. Mo, mostly present as Mo(iv) in the Cr-rich inner layer prior to anodic polarisation, becomes increasingly enriched (up to 16% of cations) mostly as Mo(vi) in the Fe-rich outer layer of the passive film, with ageing promoting this effect. Metallic Mo is not significantly enriched below the passive film produced from the native oxide covered surface. Mo does not markedly impact the nanogranular morphology of the native oxide film nor its local thickness variations assigned to substrate site effects on Cr(iii) enrichment. Site specific preferential passivation still takes place at the (native) oxide-covered step edges of the alloy surface, and transient dissolution remains preferentially located on the terraces. Nanostructures, possibly Mo-containing, and healing local depressions formed by transient dissolution during passivation, appear as a specific effect of the Mo presence. Another Mo effect, observed even after 20 h of passivation, is to prevent crystallisation at least in the Fe-rich outer part of the passive film where it is concentrated mostly as Mo(vi) (i.e. molybdate) species.

  9. Induction heating to trigger the nickel surface modification by in situ generated 4-carboxybenzene diazonium

    Science.gov (United States)

    Arrotin, Bastien; Jacques, Amory; Devillers, Sébastien; Delhalle, Joseph; Mekhalif, Zineb

    2016-05-01

    Nickel is commonly used in numerous applications and is one of the few materials that present strong ferromagnetic properties. These make it a suitable material for induction heating which can be used to activate the grafting of organic species such as diazonium salts onto the material. Diazonium compounds are often used for the modification of metals and alloys thanks to their easy chemical reduction onto the substrates and the possibility to apply a one-step in situ generation process of the diazonium species. This work focuses on the grafting of 4-aminocarboxybenzene on nickel substrates in the context of a spontaneous grafting conducted either at room temperature or by thermal assistance through conventional heating and induction heating. These modifications are also carried out with the goal of maintaining the oxides layer as much as possible unaffected. The benefits of using induction heating with respect to conventional heating are an increase of the grafting rate, a better control of the reaction and a slighter impact on the oxides layer.

  10. Fast in situ phase and stress analysis during laser surface treatment: a synchrotron x-ray diffraction approach.

    Science.gov (United States)

    Kostov, V; Gibmeier, J; Wilde, F; Staron, P; Rössler, R; Wanner, A

    2012-11-01

    An in situ stress analysis by means of synchrotron x-ray diffraction was carried out during laser surface hardening of steel. A single exposure set-up that based on a special arrangement of two fast silicon strip line detectors was established, allowing for fast stress analysis according to the sin(2)ψ x-ray analysis method. For the in situ experiments a process chamber was designed and manufactured, which is described in detail. First measurements were carried out at the HZG undulator imaging beamline (IBL, beamline P05) at the synchrotron storage ring PETRA III, DESY, Hamburg (Germany). The laser processing was carried out using a 6 kW high power diode laser system. Two different laser optics were compared, a Gaussian optic with a focus spot of ø 3 mm and a homogenizing optic with a rectangular spot dimension of 8 × 8 mm(2). The laser processing was carried out using spot hardening at a heating-/cooling rate of 1000 K/s and was controlled via pyrometric temperature measurement using a control temperature of 1150 °C. The set-up being established during the measuring campaign allowed for this first realization data collection rates of 10Hz. The data evaluation procedure applied enables the separation of thermal from elastic strains and gains unprecedented insight into the laser hardening process.

  11. Planetary Entry Probes and Mass Spectroscopy: Tools and Science Results from In Situ Studies of Planetary Atmospheres and Surfaces

    Science.gov (United States)

    Niemann, Hasso B.

    2007-01-01

    Probing the atmospheres and surfaces of the planets and their moons with fast moving entry probes has been a very useful and essential technique to obtain in situ or quasi in situ scientific data (ground truth) which could not otherwise be obtained from fly by or orbiter only missions and where balloon, aircraft or lander missions are too complex and costly. Planetary entry probe missions have been conducted successfully on Venus, Mars, Jupiter and Titan after having been first demonstrated in the Earth's atmosphere. Future missions will hopefully also include more entry probe missions back to Venus and to the outer planets. 1 he success of and science returns from past missions, the need for more and better data, and a continuously advancing technology generate confidence that future missions will be even more successful with respect to science return and technical performance. I'he pioneering and tireless work of Al Seiff and his collaborators at the NASA Ames Research Center had provided convincing evidence of the value of entry probe science and how to practically implement flight missions. Even in the most recent missions involving entry probes i.e. Galileo and Cassini/Huygens A1 contributed uniquely to the science results on atmospheric structure, turbulence and temperature on Jupiter and Titan.

  12. In-situ test methods for assessment of surface pH of corroding sewer pipes

    DEFF Research Database (Denmark)

    Nielsen, Asbjørn Haaning; Vollertsen, Jes

    A method for measuring the surface pH of corroding concrete was developed in the lab and tested in the field. The method is based on direct application of pH indicator solution on the corroding surfaces. Comparison against point measurements using a flat surface pH electrode (flatrode) confirmed...... the accuracy of the method. Blind testing of concrete specimens exposed to different acid concentrations demonstrated that it was possible to determine the surface pH within ±0.5 pH units in the pH range of one to five. The developed method provides a simple and reliable estimate on the extent of concrete...

  13. Comparison of Satellite-Derived and In-Situ Observations of Ice and Snow Surface Temperatures over Greenland

    Science.gov (United States)

    Hall, Dorothy K.; Box, Jason E.; Casey, Kimberly A.; Hook, Simon J.; Shuman, Christopher A.; Steffen, Konrad

    2008-01-01

    The most practical way to get a spatially broad and continuous measurements of the surface temperature in the data-sparse cryosphere is by satellite remote sensing. The uncertainties in satellite-derived LSTs must be understood to develop internally-consistent decade-scale land-surface temperature (LST) records needed for climate studies. In this work we assess satellite-derived "clear-sky" LST products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and LSTs derived from the Enhanced Thematic Mapper Plus (ETM+) over snow and ice on Greenland. When possible, we compare satellite-derived LSTs with in-situ air-temperature observations from Greenland Climate Network (GC-Net) automatic-weather stations (AWS). We find that MODIS, ASTER and ETM+ provide reliable and consistent LSTs under clear-sky conditions and relatively-flat terrain over snow and ice targets over a range of temperatures from -40 to 0 C. The satellite-derived LSTs agree within a relative RMS uncertainty of approx.0.5 C. The good agreement among the LSTs derived from the various satellite instruments is especially notable since different spectral channels and different retrieval algorithms are used to calculate LST from the raw satellite data. The AWS record in-situ data at a "point" while the satellite instruments record data over an area varying in size from: 57 X 57 m (ETM+), 90 X 90 m (ASTER), or to 1 X 1 km (MODIS). Surface topography and other factors contribute to variability of LST within a pixel, thus the AWS measurements may not be representative of the LST of the pixel. Without more information on the local spatial patterns of LST, the AWS LST cannot be considered valid ground truth for the satellite measurements, with RMS uncertainty approx.2 C. Despite the relatively large AWS-derived uncertainty, we find LST data are characterized by high accuracy but have uncertain absolute precision.

  14. Determination of surface concentrations of individual molecule-layers used in nanoscale biosensors by in situ ATR-FTIR spectroscopy

    KAUST Repository

    Punzet, Manuel

    2012-01-01

    For the development of nanowire sensors for chemical and medical detection purposes, the optimal functionalization of the surface is a mandatory component. Quantitative ATR-FTIR spectroscopy was used in situ to investigate the step-by-step layer formation of typical functionalization protocols and to determine the respective molecule surface concentrations. BSA, anti-TNF-α and anti-PSA antibodies were bound via 3-(trimethoxy)butylsilyl aldehyde linkers to silicon-oxide surfaces in order to investigate surface functionalization of nanowires. Maximum determined surface concentrations were 7.17 × 10 -13 mol cm -2 for BSA, 1.7 × 10 -13 mol cm -2 for anti-TNF-α antibody, 6.1 × 10 -13 mol cm -2 for anti-PSA antibody, 3.88 × 10 -13 mol cm -2 for TNF-α and 7.0 × 10 -13 mol cm -2 for PSA. Furthermore we performed antibody-antigen binding experiments and determined the specific binding ratios. The maximum possible ratio of 2 was obtained at bulk concentrations of the antigen in the μg ml -1 range for TNF-α and PSA. © 2012 The Royal Society of Chemistry.

  15. In situ plasma fabrication of ceramic-like structure on polymeric implant with enhanced surface hardness, cytocompatibility and antibacterial capability.

    Science.gov (United States)

    Liu, Jun; Zhang, Wei; Shi, Haigang; Yang, Kun; Wang, Gexia; Wang, Pingli; Ji, Junhui; Chu, Paul K

    2016-05-01

    Polymeric materials are commonly found in orthopedic implants due to their unique mechanical properties and biocompatibility but the poor surface hardness and bacterial infection hamper many biomedical applications. In this study, a ceramic-like surface structure doped with silver is produced by successive plasma implantation of silicon (Si) and silver (Ag) into the polyamine 66 (PA66) substrate. Not only the surface hardness and elastic modulus are greatly enhanced due to the partial surface carbonization and the ceramic-like structure produced by the reaction between energetic Si and the carbon chain of PA66, but also the antibacterial activity is improved because of the combined effects rendered by Ag and SiC structure. Furthermore, the modified materials which exhibit good cytocompatibility upregulate bone-related genes and proteins expressions of the contacted bone mesenchymal stem cells (BMSCs). For the first time, it explores out that BMSCs osteogenesis on the antibacterial ceramic-like structure is mediated via the iNOS and nNOS signal pathways. The results reveal that in situ plasma fabrication of an antibacterial ceramic-like structure can endow PA66 with excellent surface hardness, cytocompatibility, as well as antibacterial capability.

  16. In Situ Synthesis of Nanocrystalline Intermetallic Compound Layer during Surface Mechanical Attrition Treatment of Zirconium

    Institute of Scientific and Technical Information of China (English)

    SUNCai-yun; XIEJi-jia; WUXiao-lei; HONGYou-shi; LIUGang; LUJian; LUKe

    2004-01-01

    The surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanocrystalline (NC) layer on the surface of metallic materials for upgrading their overall properties and performance. In this paper, by means of SMAT to a pure zirconium plate at the room temperature, repetitive multidirectional peening of steel shots (composition (wt%): 1C, 1.5Cr, base Fe) severely deformed the surface layer. A NC surface layer consisting of the intermetallic compound FeCr was fabricated on the surface of the zirconium. The microstructure characterization of the surface layer was performed by using X-ray diffraction analysis, optical microscopy, scanning and transmission electron microscopy observations. The NC surface layer was about 25μm thick and consisted of the intermetallic compound FeCr with an average grain size of 25+10 nm. The deformation-induced fast diffusion of Fe and Cr from the steel shots into Zr occurred during SMAT, leading to the formation of intermetallic compound. In addition, the NC surface layer exhibited an ultrahigh nanohardness of 10.2 GPa.

  17. The In situ growth of Nanostructures on Surfaces (INS) endstation of the ESRF BM32 beamline: a combined UHV-CVD and MBE reactor for in situ X-ray scattering investigations of growing nanoparticles and semiconductor nanowires.

    Science.gov (United States)

    Cantelli, V; Geaymond, O; Ulrich, O; Zhou, T; Blanc, N; Renaud, G

    2015-05-01

    This paper presents the upgraded `In situ growth of Nanoscructures on Surfaces' (INS) endstation of the InterFace beamline IF-BM32 at the European Synchrotron Radiation Facility (ESRF). This instrument, originally designed to investigate the structure of clean surfaces/interfaces/thin-films by surface X-ray diffraction, has been further developed to investigate the formation and evolution of nanostructures by combining small- and wide-angle X-ray scattering methodologies, i.e. grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence X-ray diffraction (GIXD). It consists of a UHV chamber mounted on a z-axis type goniometer, equipped with residual gas analysis, reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) to complete the X-ray scattering investigations. The chamber has been developed so as up to eight sources of molecular beam epitaxy (MBE) can be simultaneously mounted to elaborate the nanostructures. A chemical vapor deposition (CVD) set-up has been added to expand the range of growing possibilities, in particular to investigate in situ the growth of semiconductor nanowires. This setup is presented in some detail, as well as the first in situ X-ray scattering measurements during the growth of silicon nanowires.

  18. In situ Raman spectroscopic analysis of surface oxide films on Ni-base alloy/low alloy steel dissimilar metal weld interfaces in high-temperature water

    Science.gov (United States)

    Kim, Jongjin; Choi, Kyung Joon; Bahn, Chi Bum; Kim, Ji Hyun

    2014-06-01

    In situ Raman spectroscopy has been applied to analyze the surface oxide films formed on dissimilar metal weld (DMW) interfaces of nickel-base alloy/low alloy steel under hydrogenated high-temperature water condition. For the analysis of the oxide films under high temperature/pressure aqueous conditions, an in situ Raman spectroscopy system was developed by constructing a hydrothermal cell where the entire optics including the excitation laser and the Raman light collection system were located at the nearest position to the specimen by means of immersion optics. In situ Raman spectra of the DMW interfaces were collected in hydrogenated water condition at different temperatures up to 300 °C. The measured in situ Raman spectra showed peaks of Cr2O3, NiCr2O4 and Fe3O4 at the DMW interface. It is considered that differences in the oxide chemistry originated from the chemical element distribution inside of the DMW interface region.

  19. Comparison between remotely-sensed sea-surface temperature (AVHRR and in situ records in San Matías Gulf (Patagonia, Argentina

    Directory of Open Access Journals (Sweden)

    Gabriela N Williams

    2014-03-01

    Full Text Available In situ records of sea surface temperature collected between 2005 and 2009 were used to compare, for the first time, the temperature estimated by the Multichannel algorithms (MCSST of the Advanced Very High Resolution Radiometer (AVHRR sensors in San Matías Gulf, in the north of the Argentinean Patagonian Continental Shelf (between 40°47'-42°13'S. Match-ups between in situ records and satellite sea surface temperature (SST were analyzed. In situ records came from fixed stations and oceanographic cruises, while satellite data came from different NOAA satellites. The fitting of temperature data to a Standard Major Axis (SMA type II regression model indicated that a high proportion of the total variance (0.53< r² <0.99 was explained by this model showing a high correlation between in situ data and satellite estimations. The mean differences between satellite and in situ data for the full data set were 1.64 ± 1.49°C. Looking separately into in situ data from different sources and day and night estimates from different NOAA satellites, the differences were between 0.30 ± 0.60°C and 2.60 ± 1.50°C. In this paper we discuss possible reasons for the above-mentioned performance of the MCSST algorithms in the study area.

  20. In-situ investigation of laser surface modifications of WC-Co hard metals inside a scanning electron microscope

    Science.gov (United States)

    Mueller, H.; Wetzig, K.; Schultrich, B.; Pompe, Wolfgang; Chapliev, N. I.; Konov, Vitaly I.; Pimenov, S. M.; Prokhorov, Alexander M.

    1989-05-01

    The investigation of laser interaction with solid surfaces and of the resulting mechanism of surface modification are of technical interest to optimize technological processes, and they are also of fundamental scientific importance. Most instructive indormation is available with the ail of the in-situ techniques. For instance, measuring of the photon emission of the irradiated surface ane the plasma torch (if it is produced) simultaneously to laser action, makes it possible to gain a global characterization of the laser-solid interaction. In order to obtain additional information about surface and structure modifications in microscopic detail , a laser and scanning electron microscope were combined in to a tandem equipment (LASEM). Inside this eqiipment the microscopic observation is carried out directly at the laser irradiated area without any displacement of the sample. In this way, the stepwise development of surface modification during multipulse irradiation is visible in microscopic details and much more reliable information about the surface modification process is obtainable in comparison to an external laser irradiation. Such kind of equipments were realized simultaneously and independently in the Institut of General Physics (Moscow) and the Central Institute of Solid State Physics and Material Research (Dresden) using a CO2 and a LTd-glass-laser, respectively. In the following the advantages and possibilities of a LASEM shall be demonstrated by some selected investigations of WC-CO hardmeta. The results were obtained in collaboration by both groups with the aid of the pulsed CO2-laser. The TEA CO2 laser was transmitted through a ZnSe-window into the sample chamber of the SEM and focused ofAo tfte sample surface. It was operated in TEM - oo mode with a repetition rate of about 1 pulse per second. A peak power density of about 160 MW/cm2 was achieved in front of the sample surface.

  1. Direct passivation of hydride-terminated silicon (100) surfaces by free-radically tethered polymer brushes.

    Science.gov (United States)

    Moran, Isaac W; Carter, Kenneth R

    2009-08-18

    A simple and effective means for passivating crystalline silicon is reported by the use of free-radical polymerization (FRP) to directly graft polymer chains to a hydride-terminated surface (Si-H). Complete surface coverage and passivation was achieved in approximately 24 h at 60 degrees C or 30 min at 90 degrees C. Mechanistic studies determined that chain attachment followed a hydride-transfer-based grafting-to mechanism. The grafting process is compatible with a variety of monomers and was used to assemble polymer brush layers (2-12 nm thick), with grafting densities ranging from 0.02 to 0.65 chains/nm2 rivaling densities typically obtained by grafting-from scenarios. This new passivation route provides a uniquely accessible means to covalently anchor dense polymer brushes to silicon surfaces without the need for functionalization of the polymer chain ends or the substrate.

  2. Simultaneous dopant diffusion and surface passivation in a single rapid thermal cycle

    Energy Technology Data Exchange (ETDEWEB)

    Lachiq, A.; Slaoui, A.; Georgopoulos, L.; Ventura, L.; Monna, R.; Muller, J.C. [Laboratoire PHASE, 67 - Strasbourg (France)

    1996-09-01

    Results on simultaneous formation of emitter/back-surface field or emitter/surface passivation in a single rapid thermal cycle are presented. We have investigated the diffusion kinetics of dopant elements like phosphorus, boron (from a doped spin-on glass (SOD) film), aluminium (from evaporated films) or aluminium-boron (from an Al-B SOD film). In particular, we have shown that rapid thermal co-diffusion of P and Al (or Al-B) leads to low sheet resistances, optical emitter profiles and a high gettering effect. Furthermore, the possibility of using the remaining SOD films as a surface passivation layer was investigated. Dark saturation current measurements as deduced from the photoconductivity decay technique demonstrate the passivation effect of the remaining SOD film. The highest efficiency of 12.8% obtained was achieved on SOD oxide-coated solar cells. (author)

  3. Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping.

    Science.gov (United States)

    van der Krogt, Marjolein M; de Graaf, Wendy W; Farley, Claire T; Moritz, Chet T; Richard Casius, L J; Bobbert, Maarten F

    2009-09-01

    When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length, while the prescribed increase in active state and resulting muscle force remained nearly constant in time. Opposite effects were found on the unexpected soft surface, demonstrating the bidirectional stabilizing properties of passive dynamics. These passive adaptations to unexpected surfaces may be critical when negotiating disturbances during locomotion across variable terrain.

  4. In-Situ Ultrasonic Characterization of Patterns of Sediment Surface Roughness and Subsurface Volume Inhomogeneities

    Science.gov (United States)

    2016-06-07

    successfully images surface and sub-surface biogenic structure non-invasively in the laboratory (ultrasound) and convert the technology for use in...5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) University of Rhode Island,Graduate School of Oceanography,Narragansett...RI,02882 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11

  5. Airborne, In Situ and Laboratory Measurements of the Optical and Photochemical Properties of Surface Marine Waters

    Science.gov (United States)

    2016-06-07

    matter (CDOM) in marine and estuarine waters, 2) to determine the impact of CDOM on the aquatic light field and remotely- sensed optical signals, 3) to...below-surface upwelling radiance using the Satlantic surface reference (Ajit Subramaniam); 9) backscattering coefficients employing a Hydroscat 6...respectively, in collaboration with Dr. Ajit Subramaniam. REFERENCES Degrandpre, M.D., A. Vodacek, R.K. Nelson, E.J. Bruce and N.V. Blough (1996). Seasonal

  6. In Situ Measurement of Airway Surface Liquid [K+] Using a Ratioable K+-sensitive Fluorescent Dye*

    OpenAIRE

    Namkung, Wan; Song, Yuanlin; Mills, Aaron D.; Padmawar, Prashant; Finkbeiner, Walter E.; Verkman, A. S.

    2009-01-01

    The airway surface liquid (ASL) is the thin fluid layer lining airway surface epithelial cells, whose volume and composition are tightly regulated and may be abnormal in cystic fibrosis (CF). We synthesized a two-color fluorescent dextran to measure ASL [K+], TAC-Lime-dextran-TMR, consisting of a green-fluorescing triazacryptand K+ ionophore-Bodipy conjugate, coupled to dextran, together with a red fluorescing tetramethylrhodamine reference chromophore. TAC-Lime-dextran-TMR fluorescence was K...

  7. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Veer Dhaka

    2016-01-01

    Full Text Available Low temperature (∼200 °C grown atomic layer deposition (ALD films of AlN, TiN, Al2O3, GaN, and TiO2 were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP nanowires (NWs, and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL at low temperatures (15K, and the best passivation was achieved with a few monolayer thick (2Å film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL was achieved with a capping of 2nm thick Al2O3. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al2O3 layer increased the carrier decay time from 251 ps (as-etched nanopillars to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  8. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dhaka, Veer, E-mail: veer.dhaka@aalto.fi; Perros, Alexander; Kakko, Joona-Pekko; Haggren, Tuomas; Lipsanen, Harri [Department of Micro- and Nanosciences, Micronova, Aalto University, P.O. Box 13500, FI-00076 (Finland); Naureen, Shagufta; Shahid, Naeem [Research School of Physics & Engineering, Department of Electronic Materials Engineering, Australian National University, Canberra ACT 2601 (Australia); Jiang, Hua; Kauppinen, Esko [Department of Applied Physics and Nanomicroscopy Center, Aalto University, P.O. Box 15100, FI-00076 (Finland); Srinivasan, Anand [School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, S-164 40 Kista (Sweden)

    2016-01-15

    Low temperature (∼200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al{sub 2}O{sub 3}, GaN, and TiO{sub 2} were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2Å) film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al{sub 2}O{sub 3}. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al{sub 2}O{sub 3} layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al{sub 2}O{sub 3} provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  9. Characterization of boron carbide particulate reinforced in situ copper surface composites synthesized using friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Sathiskumar, R., E-mail: sathiscit2011@gmail.com [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Murugan, N., E-mail: murugan@cit.edu.in [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Dinaharan, I., E-mail: dinaweld2009@gmail.com [Department of Mechanical Engineering, V V College of Engineering, Tisaiyanvilai, 627 657 Tamil Nadu (India); Vijay, S.J., E-mail: vijayjoseph@karunya.edu [Centre for Research in Metallurgy (CRM), School of Mechanical Sciences, Karunya University, Coimbatore, 641 114 Tamil Nadu (India)

    2013-10-15

    Friction stir processing has evolved as a novel solid state technique to fabricate surface composites. The objective of this work is to apply the friction stir processing technique to fabricate boron carbide particulate reinforced copper surface composites and investigate the effect of B{sub 4}C particles and its volume fraction on microstructure and sliding wear behavior of the same. A groove was prepared on 6 mm thick copper plates and packed with B{sub 4}C particles. The dimensions of the groove was varied to result in five different volume fractions of B{sub 4}C particles (0, 6, 12, 18 and 24 vol.%). A single pass friction stir processing was done using a tool rotational speed of 1000 rpm, travel speed of 40 mm/min and an axial force of 10 kN. Metallurgical characterization of the Cu/B{sub 4}C surface composites was carried out using optical microscope and scanning electron microscope. The sliding wear behavior was evaluated using a pin-on-disk apparatus. Results indicated that the B{sub 4}C particles significantly influenced the area, dispersion, grain size, microhardness and sliding wear behavior of the Cu/B{sub 4}C surface composites. When the volume fraction of B{sub 4}C was increased, the wear mode changed from microcutting to abrasive wear and wear debris was found to be finer. Highlights: • Fabrication of Cu/B{sub 4}C surface composite by friction stir processing • Analyzing the effect of B{sub 4}C particles on the properties of Cu/B4C surface composite • Increased volume fraction of B{sub 4}C particles reduced the area of surface composite. • Increased volume fraction of B{sub 4}C particles enhanced the microhardness and wear rate. • B{sub 4}C particles altered the wear mode from microcutting to abrasive.

  10. In Situ X-Ray Diffraction Study on Surface Melting of Bi Nanoparticles Embedded in a SiO2 Matrix

    Science.gov (United States)

    Chen, Xiao-Ming; Huo, Kai-Tuo; Liu, Peng

    2014-01-01

    Bi nanoparticles embedded in a SiO2 matrix were prepared via the high energy ball milling method. The melting behavior of Bi nanoparticles was studied by means of differential scanning calorimetry (DSC) and high-temperature in situ X-ray diffraction (XRD). DSC cannot distinguish the surface melting from ‘bulk’ melting of the Bi nanoparticles. The XRD intensity of the Bi nanoparticles decreases progressively during the in situ heating process. The variation in the normalized integrated XRD intensity versus temperature is related to the average grain size of Bi nanoparticles. Considering the effects of temperature on Debye—Waller factor and Lorentz-polarization factor, we discuss the XRD results in accordance with surface melting. Our results show that the in situ XRD technique is effective to explore the surface melting of nanoparticles.

  11. Role of surface fixed charge in the surface passivation of thermal atomic layer deposited Al2O3 on crystalline-Si

    Science.gov (United States)

    Dou, Y. N.; He, Y.; Huang, C. Y.; Zhou, C. L.; Ma, X. G.; Chen, R.; Chu, J. H.

    2012-11-01

    In this work, surface passivation of thermal atomic layer deposited (ALD) Al2O3 films on Si has been investigated. A quantitative analysis shows that field-effect passivation based on surface fixed charge combined with chemical passivation is assumed to contribute to the passivation performance and that a low defect density is critical to passivation quality. The surface fixed negative charge, which is exponentially modulated from ˜0 cm-2 to -2×1012 cm-2 by annealing, is proposed to have arisen from the reconstruction of the interfacial SiO x layer.

  12. Comparison of evaporative fluxes from porous surfaces resolved by remotely sensed and in-situ temperature and soil moisture data

    Science.gov (United States)

    Wallen, B.; Trautz, A.; Smits, K. M.

    2014-12-01

    The estimation of evaporation has important implications in modeling climate at the regional and global scale, the hydrological cycle and estimating environmental stress on agricultural systems. In field and laboratory studies, remote sensing and in-situ techniques are used to collect thermal and soil moisture data of the soil surface and subsurface which is then used to estimate evaporative fluxes, oftentimes using the sensible heat balance method. Nonetheless, few studies exist that compare the methods due to limited data availability and the complexity of many of the techniques, making it difficult to understand flux estimates. This work compares different methods used to quantify evaporative flux based on remotely sensed and in-situ temperature and soil moisture data. A series of four laboratory experiments were performed under ambient and elevated air temperature conditions with homogeneous and heterogeneous soil configurations in a small two-dimensional soil tank interfaced with a small wind tunnel apparatus. The soil tank and wind tunnel were outfitted with a suite of sensors that measured soil temperature (surface and subsurface), air temperature, soil moisture, and tank weight. Air and soil temperature measurements were obtained using infrared thermography, heat pulse sensors and thermistors. Spatial and temporal thermal data were numerically inverted to obtain the evaporative flux. These values were then compared with rates of mass loss from direct weighing of the samples. Results demonstrate the applicability of different methods under different surface boundary conditions; no one method was deemed most applicable under every condition. Infrared thermography combined with the sensible heat balance method was best able to determine evaporative fluxes under stage 1 conditions while distributed temperature sensing combined with the sensible heat balance method best determined stage 2 evaporation. The approaches that appear most promising for determining the

  13. Very low surface recombination velocity in n-type c-Si using extrinsic field effect passivation

    Science.gov (United States)

    Bonilla, Ruy S.; Woodcock, Frederick; Wilshaw, Peter R.

    2014-08-01

    In this article, field-effect surface passivation is characterised as either intrinsic or extrinsic, depending on the origin of the charges present in passivation dielectric layers. The surface recombination velocity of float zone, 1 Ω cm, n-type silicon was reduced to 0.15 cm/s, the lowest ever observed for a passivating double layer consisting of thermally grown silicon dioxide and plasma enhanced chemical vapour deposited silicon nitride. This result was obtained by enhancing the intrinsic chemical and field-effect passivation of the dielectric layers with uniform, extrinsic field-effect passivation induced by corona discharge. The position and stability of charges, both intrinsic and extrinsic, were characterised and their passivation effect was seen stable for two months with surface recombination velocity field-effect passivation provided a further decrease by a factor of 3.

  14. Apparatuses for prestressing rod-type specimens in torsion for in-situ passive fracture toughness testing in an extremely high-pressure environment of hydrogen

    Science.gov (United States)

    Wang, Jy-an [Oak Ridge, TN; Liu, Ken C [Oak Ridge, TN; Feng, Zhili [Knoxville, TN

    2012-05-15

    An in-situ specimen fixture particularly adapted for prestressing rod-type SNTT-type specimens comprising a tube and end cap wherein the specimen is secured at one end to the tube, and at the opposite end to the end cap. The end cap is rotatable relative to the tube, and may be fixedly secured for creating a torsional force prestressing the specimen enclosed within the tube.

  15. Effect of Swim Cap Surface Roughness on Passive Drag.

    Science.gov (United States)

    Gatta, Giorgio; Cortesi, Matteo; Zamparo, Paola

    2015-11-01

    In the last decade, great attention has been given to the improvements in swimming performance that can be obtained by wearing "technical swimsuits"; the technological evolution of these materials only marginally involved swim caps production, even if several studies have pointed out the important role of the head (as main impact point with the fluid) on hydrodynamics. The aim of this study was to compare the effects on passive drag (Dp) of 3 swim cap models: a smooth silicon helmet cap (usually used during swimming competitions), a silicon helmet cap with "dimples," and a silicon helmet cap with "wrinkles." Experiments were performed on 10 swimmers who were towed underwater (at a depth of 60 cm) at 3 speeds (1.5, 1.7, and 1.9 m·s) and in 2 body positions: LA (arms above the swimmer's head) and SA (arms alongside the body). The Dp values obtained in each trial were divided by the square of the corresponding speed to obtain the speed-specific drag (the k coefficient = Dp/v). No differences in k were observed among swim caps in the LA position. No differences in k were observed between the smooth and dimpled helmets also in the SA position; however, the wrinkled swim cap helmet showed a significant larger k (4.4%) in comparison with the model with dimples, when the swimmers kept their arms alongside the body (in the SA position). These data suggest that wearing a wrinkled swim cap helmet can be detrimental to performance at least in this specific position.

  16. In-Situ Observation of Surface Phenomena During Sr(NO3)2 Crystal Growth

    Institute of Scientific and Technical Information of China (English)

    陈万春; 李宝霞; 李超荣

    2003-01-01

    The reflected differential interference phase contrast microscope is used to study a growing crystal surface. The surface phenomena on the {111} and {100} faces of Sr(NO3)2, such as the propagation of steps, the bunches of surface steps, the impurity stopper and the growth hillocks, have been observed during the crystal growth. It was found that: (1) The macrosteps velocity is from 0.86μm/s to 9.8 × 10-2 μm/s on the {111} face at σ = 5.33 × 10-3 to 2.13 × 10-3. (2) If the propagating directions of the steps are in opposition, the velocity of the macrosteps will be increased after they bunched. These phenomena first provide the evidence for the existence of the mutual acceleration effect of macroscopic steps. (3) The growth hillocks include a concentric step which evidently results from successive acts of a two-dimension nucleation on surface.

  17. Dopamine Surface Modification of Trititanate Nanotubes: Proposed In-Situ Structure Models.

    Science.gov (United States)

    Liu, Ruochen; Fu, Xuejian; Wang, Congyi; Dawson, Graham

    2016-04-18

    Two models for self-assembled dopamine on the surface of trititanate nanotubes are proposed: individual monomer units linked by π-π stacking of the aromatic regions and mono-attached units interacting through hydrogen bonds. This was investigated with solid state NMR spectroscopy studies and powder X-ray diffraction.

  18. Cytochrome C Dynamics at Gold and Glassy Carbon Surfaces Monitored by in Situ Scanning Tunnel Microscopy

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Møller, Per; Pedersen, Marianne Vind;

    1995-01-01

    composite structures of about 50 nm lateral extension at gold surfaces. The aggregates evolve in time, and structures resembling individual cyt c molecules can be distinguished in the space between the 50 nm structures. Cyt c aggregates also form at glassy carbon but have a different, unbroken character...

  19. Rapid synthesis of water-glass based aerogels by in situ surface modification of the hydrogels

    Science.gov (United States)

    Bhagat, Sharad D.; Kim, Yong-Ha; Ahn, Young-Soo; Yeo, Jeong-Gu

    2007-01-01

    The objective of the present research was to reduce the processing time of water-glass based aerogels synthesized via an ambient pressure drying. For this purpose we employed a co-precursor method for the surface modification in hydrogels using trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS). The surface modification resulted in the displacement of pore water from the hydrogels and thereby absolutely avoiding the time-consuming solvent exchange step. The attachment of trymethylsilyl ( sbnd Si(CH 3) 3) groups to the silica surface was confirmed by the presence of Si sbnd CH 3 peaks at 2900, 1400, 1255 and 845 cm -1 in the Fourier Transform Infrared (FTIR) spectra. The differential thermal analysis (DTA) revealed that the aerogels maintain their hydrophobic behavior up to a maximum temperature of 500 °C above which they become hydrophilic. The physical and textural properties of the silica aerogels have been reported and the results have been discussed by taking into account the surface modification and the amounts of the pore water displaced out from the hydrogels.

  20. Satellite‐derived surface temperature and in situ measurement at Solfatara of Pozzuoli (Naples, Italy)

    National Research Council Canada - National Science Library

    Silvestri, M; Cardellini, C; Chiodini, G; Buongiorno, M. F

    2016-01-01

    ... and their spatial distribution, providing insights into a particular volcano's activity status, impending changes in activity, and subsurface processes generating thermal anomalies. In this framework, satellite‐based TIR remote sensing provides a very powerful tool with which to study surface temperature, providing global coverage and a suitable data frequency (...

  1. Decoupling Bulk and Surface Contributions in Water- Splitting Photocatalysts by In Situ Ultrafast Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Appavoo, Kannatassen [Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials; Mingzhao, Liu [Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials; Black, Charles T. [Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials; Sfeir, Matthew Y. [Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials

    2015-05-10

    By performing ultrafast emission spectroscopy in an operating, bias-controlled photoelectrochemical cell, we distinguish between bulk (charge transport) and surface (chemical reaction) recombination processes in a nanostructured photocatalyst and correlate its electronic properties directly with its incident-photon-to-current efficiency.

  2. In situ monitoring of corrosion mechanisms and phosphate inhibitor surface deposition during corrosion of zinc-magnesium-aluminium (ZMA) alloys using novel time-lapse microscopy.

    Science.gov (United States)

    Sullivan, James; Cooze, Nathan; Gallagher, Callum; Lewis, Tom; Prosek, Tomas; Thierry, Dominique

    2015-01-01

    In situ time-lapse optical microscopy was used to examine the microstructural corrosion mechanisms in three zinc-magnesium-aluminium (ZMA) alloy coated steels immersed in 1% NaCl pH 7. Preferential corrosion of MgZn(2) lamellae within the eutectic phases was observed in all the ZMA alloys followed by subsequent dissolution of Zn rich phases. The total extent and rate of corrosion, measured using time-lapse image analysis and scanning vibrating electrode technique (SVET) estimated mass loss, decreased as Mg and Al alloying additions were increased up to a level of 3 wt% Mg and 3.7 wt% Al. This was probably due to the increased presence of MgO and Al(2)O(3) at the alloy surface retarding the kinetics of cathodic oxygen reduction. The addition of 1 × 10(-2) mol dm(-3) Na(3)PO(4) to 1% NaCl pH 7 had a dramatic influence on the corrosion mechanism for a ZMA with passivation of anodic sites through phosphate precipitation observed using time-lapse image analysis. Intriguing rapid precipitation of filamentous phosphate was also observed and it is postulated that these filaments nucleate and grow due to super saturation effects. Polarisation experiments showed that the addition of 1 × 10(-2) mol dm(-3) Na(3)PO(4) to the 1% NaCl electrolyte promoted an anodic shift of 50 mV in open circuit potential for the ZMA alloy with a reduction in anodic current of 2.5 orders of magnitude suggesting that it was acting primarily as an anodic inhibitor supporting the inferences from the time-lapse investigations. These phosphate additions resulted in a 98% reduction in estimated mass loss as measured by SVET demonstrating the effectiveness of phosphate inhibitors for this alloy system.

  3. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy of Cobalt Perovskite Surfaces under Cathodic Polarization at High Temperatures

    KAUST Repository

    Crumlin, Ethan J.

    2013-08-08

    Heterostructured oxide interfaces have demonstrated enhanced oxygen reduction reaction rates at elevated temperatures (∼500-800 C); however, the physical origin underlying this enhancement is not well understood. By using synchrotron-based in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we focus on understanding the surface electronic structure, elemental composition, and chemical nature of epitaxial La0.8Sr 0.2CoO3-δ (LSC113), (La 0.5Sr0.5)2CoO4±δ (LSC214), and LSC214-decorated LSC113 (LSC 113/214) thin films as a function of applied electrical potentials (0 to -800 mV) at 520 C and p(O2) of 1 × 10-3 atm. Shifts in the top of the valence band binding energy and changes in the Sr 3d and O 1s spectral components under applied bias reveal key differences among the film chemistries, most notably in the degree of Sr segregation to the surface and quantity of active oxygen sites in the perovskite termination layer. These differences help to identify important factors governing the enhanced activity of oxygen electrocatalysis observed for the LSC113/214 heterostructured surface. © 2013 American Chemical Society.

  4. Spatial and Temporal Variations of Surface Temperature Over Greenland As Observed In AIRS, MODIS and In-Situ Measurements

    Science.gov (United States)

    Lee, J. N.; Susskind, J.; Wu, D. L.; Nowicki, S.; Hall, D. K.; Iredell, L. F.

    2015-12-01

    This paper compares the temporal and spatial characteristics of the AIRS and MODIS surface temperatures over Greenland. To estimate uncertainties in space-based temperature measurements, we reprojected the MODIS Ice Surface Temperature (IST) into 0.5 by 0.5 degree spatial resolution. We also re-gridded AIRS Skin Temperature (Ts) with same spatial resolution but classified with different cloud conditions and surface types. These co-located data sets make intercomparison between the two instruments relatively straightforward. By this approach, the spatial comparison between AIRS Ts and MODIS IST monthly mean is in good agreement with RMS less than 2K during May 2012. This approach also allows the detection of any long-term calibration drift and the careful examination of calibration consistency in MODIS and AIRS temperature data record. The temporal correlations between temperature data are also compared with those from in-situ measurements from GC-Net and NOAA stations. The most significant diurnal difference is found during spring season (April and May) in high altitude regions, when interannual variability is relatively smaller than summer and winter.

  5. In Situ Determination of the Transport Properties of Near-Surface Concrete Using AC Impedance Spectroscopy Techniques

    Directory of Open Access Journals (Sweden)

    Lipeng Wu

    2016-01-01

    Full Text Available The durability of existing concrete structures has increasingly attracted widespread attention in recent years. The phenomenon of performance degradation is often associated with the intrusion of hazardous ions from outside. As the first barrier to external substances intrusion, the near-surface concrete plays an important role in durability. So the performance of in-service concrete structures often depends on the transport properties of the near-surface concrete. Accordingly, information on service conditions and life prediction can be obtained by testing these transport properties. In this paper, an in situ method for chloride ion diffusion coefficient determination is proposed based on the relationship between the alternating current impedance spectroscopy parameters and the chloride ion diffusion coefficient. By a rational design, the new method can synthetically reflect the transport properties of near-surface concrete and is not affected by the presence of the reinforcing bar. In addition, the experimental results show that the method is in good agreement with “PERMIT” migration test which has been widely used. The proposed method is less time consuming and nondestructive and has good reproducibility.

  6. DEBIE - first standard in-situ debris monitoring instrument

    Science.gov (United States)

    Kuitunen, J.; Drolshagen, G.; McDonnell, J. A. M.; Svedhem, H.; Leese, M.; Mannermaa, H.; Kaipiainen, M.; Sipinen, V.

    2001-10-01

    Objects larger than a few centimetres can be tracked with radar or with optical telescopes. The population of smaller particles can only be investigated by the analysis of retrieved spacecraft and passive detectors or by in-situ monitors in orbit. Patria Finavitec together with UniSpace Kent have developed the DEBIE (DEBris In-orbit Evaluator) instrument to determine the parameters of sub-millimetre sized space debris and micrometeoroids in-situ by their impact with a detecting surface. The main goal has been to develop an economical and low-resource instrument, easy to integrate into any spacecraft, while providing reliable real-time data for space debris modelling.

  7. GaAs Surface Passivation for Device Applications.

    Science.gov (United States)

    1981-12-01

    Physics Letters 38, 167 (1981). 10. A Ga203 surface layer with the low band bending may also be pro- duced by heating the initial etched surface to... Physics of MOS Insulators, Edited by G. Lucovsky, S.T. Pantelides, and F.L. Galeener -Pergamon Press, New York, 1980) p. 202. 7. E.A. Kraut, R.W...E. Luscher , W. S. Knodle, and Y. Chai, Electronics 53, (19), 160 (1980). 2. J. P. Hobson and E. V. Kornelsen, J. Vac. Sci. Technol. 16, 701(1979). 3

  8. Efficient wetland surface water detection and monitoring via Landsat: Comparison with in situ data from the Everglades Depth Estimation Network

    Science.gov (United States)

    Jones, John W.

    2015-01-01

    The U.S. Geological Survey is developing new Landsat science products. One, named Dynamic Surface Water Extent (DSWE), is focused on the representation of ground surface inundation as detected in cloud-/shadow-/snow-free pixels for scenes collected over the U.S. and its territories. Characterization of DSWE uncertainty to facilitate its appropriate use in science and resource management is a primary objective. A unique evaluation dataset developed from data made publicly available through the Everglades Depth Estimation Network (EDEN) was used to evaluate one candidate DSWE algorithm that is relatively simple, requires no scene-based calibration data, and is intended to detect inundation in the presence of marshland vegetation. A conceptual model of expected algorithm performance in vegetated wetland environments was postulated, tested and revised. Agreement scores were calculated at the level of scenes and vegetation communities, vegetation index classes, water depths, and individual EDEN gage sites for a variety of temporal aggregations. Landsat Archive cloud cover attribution errors were documented. Cloud cover had some effect on model performance. Error rates increased with vegetation cover. Relatively low error rates for locations of little/no vegetation were unexpectedly dominated by omission errors due to variable substrates and mixed pixel effects. Examined discrepancies between satellite and in situ modeled inundation demonstrated the utility of such comparisons for EDEN database improvement. Importantly, there seems no trend or bias in candidate algorithm performance as a function of time or general hydrologic conditions, an important finding for long-term monitoring. The developed database and knowledge gained from this analysis will be used for improved evaluation of candidate DSWE algorithms as well as other measurements made on Everglades surface inundation, surface water heights and vegetation using radar, lidar and hyperspectral instruments

  9. High temperature in operando and in situ spectroscopy on electrified surfaces and interfaces

    DEFF Research Database (Denmark)

    Chatzichristodoulou, Christodoulos; Hansen, Karin Vels; Holtappels, Peter

    Electrochemical cells, such as fuel cells, electrolyzers and batteries are considered as important technologies for storing electricity from renewable sources and also provide an efficient way of converting chemical energy into electricity. The processes in the electrodes are strongly influenced...... are particularly attractive since hydrocarbon fuels in principle can be directly converted into electricity and vice versa with high efficiency. However, several side effects such as coking and poisoning with impurities e.g. sulfur on the fuel electrode, but also indication of changes in surface chemistry of oxide...... by the surface electrocatalytic properties, especially if instead of (or in addition to) hydrogen more complex reactants such hydrocarbons in form of alcohols, methane or higher hydro carbons are used as reactants. High temperature, solid state electrochemical cells based on an oxide ion conducting electrolyte...

  10. In Situ Radiometric and Exposure Age Dating of the Martian Surface

    Science.gov (United States)

    Farley, K. A.; Malespin, C.; Mahaffy, P.; Grotzinger, J. P.; Vasconcelos, P. M.; Milliken, R. E.; Malin, M.; Edgett, K. S.; Pavlov, A. A.; Hurowitz, J. A.; Grant, J. A.; Miller, H. B.; Arvidson, R.; Beegle, L.; Calef, F.; Conrad, P. G.; Dietrich, W. E.; Eigenbrode, J.; Gellert, R.; Gupta, S.; Hamilton, V.; Hassler, D. M.; Lewis, K. W.; McLennan, S. M.; Ming, D. M.; Navarro-Gonzalez, R.; Schwenzer, S. P.; Steele, A.; Stolper, E. M.; Sumner, D. Y.; Vaniman, D.; Vasavada, A.; Williford, K.; Wimmer-Schweingruber, R. F.

    2014-01-01

    We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 +/- 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced 3He, 21Ne, and 36Ar yield concordant surface exposure ages of 78 T 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.

  11. Fate of the herbicides 2,4,5-T, atrazine, and DNOC in a shallow, anaerobic aquifer investigated by in situ passive diffusive emitters and laboratory batch experiments.

    Science.gov (United States)

    Arildskov, N P; Pedersen, P G; Albrechtsen, H J

    2001-01-01

    The fate of the three herbicides 2,4,5-T (2,4,5-trichlorophenoxyacetic acid), atrazine (6-chloro-N-ethyl-N'-[1-methyl-ethyl]-1,3,5-triazine-2,4-diamine), and DNOC (4,6-dinitro-2-methylphenol) in an anaerobic sandy aquifer was investigated. In the field, each of the herbicides was released simultaneously with tritiated water (HTO) as tracer in the depth interval 3 to 4 mbs (meters below surface) by use of passive diffusive emitters. Atrazine and 2,4,5-T were persistent during the approximately 18 days residence time in the aquifer. In contrast, DNOC was rapidly removed from the water phase following first-order kinetics. The removal mechanism was likely an abiotic reduction. At day 25, the first-order rate constant was 1.47 d(-1), but it decreased with time and seemed to stabilize at 0.35 d(-1) after 150 to 200 days. In the laboratory, batch experiments were conducted with sediments from 3 to 4 mbs and from 8 to 9 mbs. In these incubations, formation of Fe2+ and depletion of sulfate showed iron and sulfate reduction in sediment from 3 to 3.5 mbs and sulfate reduction in 3.5 to 4 mbs sediment. In sediment from 8 to 9 mbs, the dominant redox process was methane formation. In sediment from 3 to 3.5 mbs, only 27% to 52% of the 2,4,5-T remained after 196 days. 2,4,5-trichlorophenol was identified as the major metabolite. A lag period of at least 50 days was observed, and no degradation occurred in HgCl2 amended controls, verifying that the process was microbially mediated. In the other 2,4,5-T incubations and all the atrazine incubations, concentrations decreased linearly, but less than 25% was removed within 200 to 250 days. No degradation products could be detected, and slow sorption was the likely explanation. In all the laboratory incubations DNOC was degraded, following first-order kinetics, and when normalized to the sediment/water-ratio, the field and laboratory derived rate constants compared well. The DNOC degradation in the methanogenic incubations (8 to 9 mbs

  12. Variation of surface water spectral response as a function of in situ sampling technique

    Science.gov (United States)

    Davis, Bruce A.; Hodgson, Michael E.

    1988-01-01

    Tests were carried out to determine the spectral variation contributed by a particular sampling technique. A portable radiometer was used to measure the surface water spectral response. Variation due to the reflectance of objects near the radiometer (i.e., the boat side) during data acquisition was studied. Consideration was also given to the variation due to the temporal nature of the phenomena (i.e., wave activity).

  13. A charge transport study in diamond, surface passivated by high-k dielectric oxides

    Energy Technology Data Exchange (ETDEWEB)

    Kovi, Kiran Kumar, E-mail: KiranKumar.Kovi@angstrom.uu.se; Majdi, Saman; Gabrysch, Markus; Isberg, Jan [Division for Electricity, Department of Engineering Sciences, Box 534, Uppsala University, Uppsala SE-751 21 (Sweden)

    2014-11-17

    The recent progress in the growth of high-quality single-crystalline diamond films has sparked interest in the realization of efficient diamond power electronic devices. However, finding a suitable passivation is essential to improve the reliability and electrical performance of devices. In the current work, high-k dielectric materials such as aluminum oxide and hafnium oxide were deposited by atomic layer deposition on intrinsic diamond as a surface passivation layer. The hole transport properties in the diamond films were evaluated and compared to unpassivated films using the lateral time-of-flight technique. An enhancement of the near surface hole mobility in diamond films of up to 27% is observed when using aluminum oxide passivation.

  14. In situ laser measurements of CO and CH4 close to the surface of a burning single fuel particle

    Science.gov (United States)

    Lackner, M.; Totschnig, G.; Winter, F.; Maiorov, M. A.; Garbuzov, D. Z.; Connolly, J. C.

    2002-10-01

    The combustion behaviour of three different fuels, bituminous coal, beech wood and fir wood, was investigated by monitoring the concentrations of CO, CH4, CO2 and O2 during devolatilization and char combustion. Single fuel particles (4-6 mm diameter, 55 mm in length) were positioned in the freeboard of a laboratory-scale fluidized bed combustor. The superficial velocity was 0.3 m s-1. Tunable diode laser absorption spectroscopy was used to investigate in situ the concentration histories of the evolving species CO and CH4. An InGaAsSb/AlGaAsSb diode laser was frequency tuned around 2.3 µm at 300 Hz and traversed the reactor directly above the particle. This enabled for the first time, to the knowledge of the authors, the accurate measurement of species concentrations close to the surface of a burning particle. The influence of the oxygen partial pressure (5, 10, 15, 21 kPa), the bed temperature (700, 800, 900̂C), the distance of the laser beam from the particle (4, 10, 21, 31 mm) and hence the residence time (12, 30, 60, 90 ms), the particle size (4, 6 mm diameter) and the fuel type were investigated by independently changing these governing parameters. Conventional methods were deployed to determine CO, CO2 and O2 in the exhaust gas. The evolving CO could be tracked down to 12 ms after its generation. Biomass was found to produce four times as much CO as coal. The CO/CO2 ratio was found to be about five times higher for beech wood (a typical hardwood) than for fir wood (a typical softwood). The comparison of the in situ results with conventionally measured concentrations showed that the CO is normally underestimated during devolatilization and overestimated during char combustion. The discrepancy was attributed to more efficient degradation mechanisms for CO during devolatilization.

  15. The intensity dependence of surface recombination in high concentration solar cells with charge induced passivation

    Science.gov (United States)

    Gray, J. L.; Schwartz, R. J.; Lundstrom, M. S.; Nasby, R. D.

    High intensity solar cells which are designed to minimize series resistance and shadowing losses, frequently employ an illuminated surface which is relatively far removed from the collecting junctions. This requires that the surface be well passivated to minimize surface recombination. One technique frequently employed to minimize surface recombination is to incorporate a fixed charge in the passivating oxide. This work shows that at sufficiently high intensities the surface recombination can increase dramatically. This results in a reduction in the high intensity collection efficiency. A comparison of the collection efficiency of interdigitated back contact cells and etched multiple vertical junction cells is given which shows that EMVJ cells are less sensitive to this effect than IBC cells.

  16. Adherence of platelets to in situ albumin-binding surfaces under flow conditions: role of surface-adsorbed albumin.

    Science.gov (United States)

    Guha Thakurta, Sanjukta; Miller, Robert; Subramanian, Anuradha

    2012-08-01

    Surfaces that preferentially bind human serum albumin (HSA) were generated by grafting albumin-binding linear peptide (LP1) onto silicon surfaces. The research aim was to evaluate the adsorption pattern of proteins and the adhesion of platelets from platelet-poor plasma and platelet-rich plasma, respectively, by albumin-binding surfaces under physiological shear rate (96 and 319 s(-1)) conditions. Bound proteins were quantified using enzyme-linked immunosorbent assays (ELISAs) and two-dimensional gel electrophoresis. A ratio of ∼1000:100:1 of adsorbed HSA, human immunoglobulin (HIgG) and human fibrinogen (HFib) was noted, respectively, on LP1-functionalized surfaces, and a ratio of ∼5:2:1 of the same was noted on control surfaces, as confirmed by ELISAs. The surface-adsorbed von Willebrand factor was undetectable by sensitive ELISAs. The amount of adhered platelets correlated with the ratio of adsorbed HSA/HFib. Platelet morphology was more rounded on LP1-functionalized surfaces when compared to control surfaces. The platelet adhesion response on albumin-binding surfaces can be explained by the reduction in the co-adsorption of other plasma proteins in a surface environment where there is an excess of albumin molecules, coupled with restrictions in the conformational transitions of other surface-adsorbed proteins into hemostatically active forms.

  17. Passivation of the surface of rear contact solar cells by porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Nichiporuk, O. [Radiophysics Department, Taras Shevchenko National University, 64 Vladimirskaya, 01033, Kiev (Ukraine) and Laboratoire de Physique de la Matiere, UMR 5511, INSA de Lyon, Bat. Blaise Pascal, 7 avenue Jean Capelle, 69621 Villeurbanne Cedex (France)]. E-mail: oleksiy.nichiporuk@insa-lyon.fr; Kaminski, A. [Laboratoire de Physique de la Matiere, UMR 5511, INSA de Lyon, Bat. Blaise Pascal, 7 avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Lemiti, M. [Laboratoire de Physique de la Matiere, UMR 5511, INSA de Lyon, Bat. Blaise Pascal, 7 avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Fave, A. [Laboratoire de Physique de la Matiere, UMR 5511, INSA de Lyon, Bat. Blaise Pascal, 7 avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Litvinenko, S. [Radiophysics Department, Taras Shevchenko National University, 64 Vladimirskaya, 01033, Kiev (Ukraine); Skryshevsky, V. [Radiophysics Department, Taras Shevchenko National University, 64 Vladimirskaya, 01033, Kiev (Ukraine)

    2006-07-26

    In this paper we analyse the passivation of the front surface of p-Si interdigitated rear contacts solar cell (IBC) by a thin porous silicon (PS) layer. Effectively, an efficiency improvement of 87% in relative was observed after porous silicon layer formation on the front surface of the IBC cell. The origin of surface passivation by the PS layer was studied by Laser Beam Induced Current (LBIC) method. The front surface of rear contacts cell with thin porous silicon layer was scanned by a modulated red laser beam in presence of a permanent light with different wavelengths and intensities. It was shown that without permanent illumination, the photocurrent of the cell with PS layer is very low, even lower than for a cell with unpassivated surface. However with short permanent wavelength illumination a strong increase of photocurrent was observed (8-10 times{exclamation_point}). The light-dependent porous silicon passivation phenomenon is explained by a significant negative charge accumulation at the PS/p-Si interface traps under illumination. This leads to the formation of a hi-low (p{sup +}/p) junction at the front surface of the cell and to the reduction of the front surface recombination rate, like in Front Surface Field Solar Cell.

  18. X-ray in-situ study of copper electrodeposition on UHV prepared GaAs(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gruender, Yvonne

    2008-06-02

    For this work a unique setup for in-situ electrochemical studies was employed and improved. This setup permits UHV preparation of the GaAs(001) surface with a defined surface termination (arsenic-rich or gallium-rich) and its characterization by SXRD in UHV, under ambient pressure in inert gas and in electrolyte under potential control without passing through air. The GaAs(001) surfaces were capped by amorphous arsenic. This permitted to ship them through ambient air. Afterwards smooth well defined GaAs(001) surfaces could be recovered by thermal annealing in UHV. A first investigation of the arsenic capped sample was done by atomic force microscopy (AFM) and Surface X-Ray Diffraction (SXRD). The non bulk like termination of the arsenic buried GaAs(001) surface was revealed. For the electrochemical metal deposition, arsenic terminated (2 x 4) reconstructed and gallium terminated (4 x 2) reconstructed GaAs(001) surfaces were employed. These surfaces were characterized by STM, LEED and a first time by SXRD. The surfaces are smooth, however, a higher degree of disorder than for MBE prepared reconstructed GaAs(001) is found. After exposure of the sample to nitrogen, the surfaces were then again studied by SXRD. These two steps characterizing the bare GaAs(001) surfaces permitted us to get a better knowledge of the starting surface and its influence on the later electrodeposited copper. At ambient pressure both reconstructions are lifted, but the surface is not bulk-like terminated as can be deduced from the crystal truncation rods. Epitaxial copper clusters grow upon electrodeposition on the UHV prepared GaAs(001) surface. The copper lattice is rotated and inclined with respect to the GaAs substrate lattice, leading to eight symmetry equivalent domains. The influence of the surface termination as well as the nucleation potential on the structure of the electrodeposited copper were investigated. The tilt and rotation angles do not depend on the deposition potential but

  19. Calcium Pyroxenes at Mercurian Surface Temperatures: Investigation of In-Situ Emissivity Spectra.

    Science.gov (United States)

    Ferrari, Sabrina; Maturilli, Alessandro; Helbert, Jörn; Rossi, Manuela; Nestola, Fabrizio; D'Amore, Mario; Hiesinger, Harald

    2014-05-01

    Several observations point to the possibility that Ca-rich (and low-Fe) clinopyroxenes could be common constituent minerals of the surface of Mercury. The upcoming ESA-JAXA BepiColombo mission to Mercury will carry on board the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) that will provide surface emissivity spectra in the wavelength range from 7-14 μm. This spectral range is very useful to identify the fine-scale structural properties of several silicates including pyroxenes. The extreme daily surface temperature range of Mercury (70 to 725 K) that significantly affects the spectral signature of minerals will make the interpretation of MERTIS observations challenging. It has been shown that spectra of clinopyroxenes with similar calcium content display a deepening of the main absorption bands, and a shift of the band minima toward higher wavelengths with increasing temperatures. Similar shifts can also be observed at constant temperature with increasing iron content in the M2 site. Therefore, the thermal expansion induced by the increasing temperature simulates the presence of a larger cation (e.g., iron vs. magnesium) within the mineral structure. Interestingly, each band shifts by a different amount, representing a marker for the real chemistry of the sample. A detailed study of the described mineral behavior is fundamental to localize those spectral bands sensitive to the daily temperature range of the Mercury surface. In combination with the temperature measurements obtained independently by the radiometer channel of MERTIS this will help to further constrain the mineralogical interpretation of the MERTIS spectral data. Here we present high-temperature (up to 750 K) laboratory emissivity spectra of several augitic pyroxenes with different calcium contents and very different magnesium to iron ratios. The spectra were derived from individual well-preserved natural crystals of several pyroxenes of less than 125 ?m in size, which approaches the

  20. Evaluation of OSCAR ocean surface current product in the tropical Indian Ocean using in situ data

    Indian Academy of Sciences (India)

    Rajesh Sikhakolli; Rashmi Sharma; Sujit Basu; B S Gohil; Abhijit Sarkar; K V S R Prasad

    2013-02-01

    The OSCAR (ocean surface current analysis real-time),which is a product derived from various satellite observations,has been evaluated in the tropical Indian Ocean (TIO)in two di fferent ways.First,the OSCAR-derived monthly climatology has been compared with available drifter-derived climatology in the TIO.From the comparison of the two climatologies,one can infer that OSCAR product is able to capture the variabilities of the well-known surface current systems in the TIO reasonably well.Fourier analysis of the major current systems,as reproduced by OSCAR,shows that the dominant annual and semiannual periodicities,known to exist in these systems,have been faithfully picked up by OSCAR. Next,the evaluation has been carried out by comparing the OSCAR currents with currents measured by moored buoys.The zonal component of OSCAR-current is in good agreement with corresponding component of buoy-observed current with a correlation exceeding 0.7,while the match between the meridional components is poorer.The locations of the peaks of the mean and eddy kinetic energies are matching in both the climatologies,although the peak in the drifter climatology is stronger than the same in the OSCAR product.Finally,an important feature of Indian Ocean circulation,namely the reverse Wyrtki jet,occurring during anomalous dipole years,has been well-reproduced by OSCAR currents.

  1. Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

    Directory of Open Access Journals (Sweden)

    Jia Ge

    2014-01-01

    Full Text Available We present an alternative method of depositing a high-quality passivation film for heterojunction silicon wafer solar cells, in this paper. The deposition of hydrogenated intrinsic amorphous silicon suboxide is accomplished by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma platform. Through the investigation on CO2 partial pressure and process temperature, excellent surface passivation quality and optical properties are achieved. It is found that the hydrogen content in the film is much higher than what is commonly reported in intrinsic amorphous silicon due to oxygen incorporation. The observed slow depletion of hydrogen with increasing temperature greatly enhances its process window as well. The effective lifetime of symmetrically passivated samples under the optimal condition exceeds 4.7 ms on planar n-type Czochralski silicon wafers with a resistivity of 1 Ωcm, which is equivalent to an effective surface recombination velocity of less than 1.7 cms−1 and an implied open-circuit voltage (Voc of 741 mV. A comparison with several high quality passivation schemes for solar cells reveals that the developed inductively coupled plasma deposited films show excellent passivation quality. The excellent optical property and resistance to degradation make it an excellent substitute for industrial heterojunction silicon solar cell production.

  2. Surface passivation of efficient nanotextured black silicon solar cells using thermal atomic layer deposition.

    Science.gov (United States)

    Wang, Wei-Cheng; Lin, Che-Wei; Chen, Hsin-Jui; Chang, Che-Wei; Huang, Jhih-Jie; Yang, Ming-Jui; Tjahjono, Budi; Huang, Jian-Jia; Hsu, Wen-Ching; Chen, Miin-Jang

    2013-10-09

    Efficient nanotextured black silicon solar cells passivated by an Al2O3 layer are demonstrated. The broadband antireflection of the nanotextured black silicon solar cells was provided by fabricating vertically aligned silicon nanowire (SiNW) arrays on the n(+) emitter. A highly conformal Al2O3 layer was deposited upon the SiNW arrays by the thermal atomic layer deposition (ALD) based on the multiple pulses scheme. The nanotextured black silicon wafer covered with the Al2O3 layer exhibited a low total reflectance of ∼1.5% in a broad spectrum from 400 to 800 nm. The Al2O3 passivation layer also contributes to the suppressed surface recombination, which was explored in terms of the chemical and field-effect passivation effects. An 8% increment of short-circuit current density and 10.3% enhancement of efficiency were achieved due to the ALD Al2O3 surface passivation and forming gas annealing. A high efficiency up to 18.2% was realized in the ALD Al2O3-passivated nanotextured black silicon solar cells.

  3. Electrical and optical characterization of surface passivation in GaAs nanowires.

    Science.gov (United States)

    Chang, Chia-Chi; Chi, Chun-Yung; Yao, Maoqing; Huang, Ningfeng; Chen, Chun-Chung; Theiss, Jesse; Bushmaker, Adam W; Lalumondiere, Stephen; Yeh, Ting-Wei; Povinelli, Michelle L; Zhou, Chongwu; Dapkus, P Daniel; Cronin, Stephen B

    2012-09-12

    We report a systematic study of carrier dynamics in Al(x)Ga(1-x)As-passivated GaAs nanowires. With passivation, the minority carrier diffusion length (L(diff)) increases from 30 to 180 nm, as measured by electron beam induced current (EBIC) mapping, and the photoluminescence (PL) lifetime increases from sub-60 ps to 1.3 ns. A 48-fold enhancement in the continuous-wave PL intensity is observed on the same individual nanowire with and without the Al(x)Ga(1-x)As passivation layer, indicating a significant reduction in surface recombination. These results indicate that, in passivated nanowires, the minority carrier lifetime is not limited by twin stacking faults. From the PL lifetime and minority carrier diffusion length, we estimate the surface recombination velocity (SRV) to range from 1.7 × 10(3) to 1.1 × 10(4) cm·s(-1), and the minority carrier mobility μ is estimated to lie in the range from 10.3 to 67.5 cm(2) V(-1) s(-1) for the passivated nanowires.

  4. Excellent c-Si surface passivation by low-temperature atomic layer deposited titanium oxide

    Science.gov (United States)

    Liao, Baochen; Hoex, Bram; Aberle, Armin G.; Chi, Dongzhi; Bhatia, Charanjit S.

    2014-06-01

    In this work, we demonstrate that thermal atomic layer deposited (ALD) titanium oxide (TiOx) films are able to provide a—up to now unprecedented—level of surface passivation on undiffused low-resistivity crystalline silicon (c-Si). The surface passivation provided by the ALD TiOx films is activated by a post-deposition anneal and subsequent light soaking treatment. Ultralow effective surface recombination velocities down to 2.8 cm/s and 8.3 cm/s, respectively, are achieved on n-type and p-type float-zone c-Si wafers. Detailed analysis confirms that the TiOx films are nearly stoichiometric, have no significant level of contaminants, and are of amorphous nature. The passivation is found to be stable after storage in the dark for eight months. These results demonstrate that TiOx films are also capable of providing excellent passivation of undiffused c-Si surfaces on a comparable level to thermal silicon oxide, silicon nitride, and aluminum oxide. In addition, it is well known that TiOx has an optimal refractive index of 2.4 in the visible range for glass encapsulated solar cells, as well as a low extinction coefficient. Thus, the results presented in this work could facilitate the re-emergence of TiOx in the field of high-efficiency silicon wafer solar cells.

  5. Enhanced photoelectrochemical water splitting performance of anodic TiO(2) nanotube arrays by surface passivation.

    Science.gov (United States)

    Gui, Qunfang; Xu, Zhen; Zhang, Haifeng; Cheng, Chuanwei; Zhu, Xufei; Yin, Min; Song, Ye; Lu, Linfeng; Chen, Xiaoyuan; Li, Dongdong

    2014-10-08

    One-dimensional anodic titanium oxide nanotube (TONT) arrays provide a direct pathway for charge transport, and thus hold great potential as working electrodes for electrochemical energy conversion and storage devices. However, the prominent surface recombination due to the large amount surface defects hinders the performance improvement. In this work, the surface states of TONTs were passivated by conformal coating of high-quality Al2O3 onto the tubular structures using atomic layer deposition (ALD). The modified TONT films were subsequently employed as anodes for photoelectrochemical (PEC) water splitting. The photocurrent (0.5 V vs Ag/AgCl) recorded under air mass 1.5 global illumination presented 0.8 times enhancement on the electrode with passivation coating. The reduction of surface recombination rate is responsible for the substantially improved performance, which is proposed to have originated from a decreased interface defect density in combination with a field-effect passivation induced by a negative fixed charge in the Al2O3 shells. These results not only provide a physical insight into the passivation effect, but also can be utilized as a guideline to design other energy conversion devices.

  6. Optical near-field lithography on hydrogen-passivated silicon surfaces

    DEFF Research Database (Denmark)

    Madsen, Steen; Müllenborn, Matthias; Birkelund, Karen

    1996-01-01

    We report on a novel lithography technique for patterning of hydrogen-passivated amorphous silicon surfaces. A reflection mode scanning near-field optical microscope with uncoated fiber probes has been used to locally oxidize a thin amorphous silicon layer. Lines of 110 nm in width, induced...

  7. Excellent c-Si surface passivation by low-temperature atomic layer deposited titanium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Baochen, E-mail: liaobaochen@nus.edu.sg [Solar Energy Research Institute of Singapore, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); A*STAR Institute of Materials Research and Engineering (IMRE), 3 Research Link, Singapore 117602 (Singapore); Hoex, Bram [Solar Energy Research Institute of Singapore, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 (Singapore); Aberle, Armin G.; Bhatia, Charanjit S., E-mail: elebcs@nus.edu.sg [Solar Energy Research Institute of Singapore, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Chi, Dongzhi [A*STAR Institute of Materials Research and Engineering (IMRE), 3 Research Link, Singapore 117602 (Singapore)

    2014-06-23

    In this work, we demonstrate that thermal atomic layer deposited (ALD) titanium oxide (TiO{sub x}) films are able to provide a—up to now unprecedented—level of surface passivation on undiffused low-resistivity crystalline silicon (c-Si). The surface passivation provided by the ALD TiO{sub x} films is activated by a post-deposition anneal and subsequent light soaking treatment. Ultralow effective surface recombination velocities down to 2.8 cm/s and 8.3 cm/s, respectively, are achieved on n-type and p-type float-zone c-Si wafers. Detailed analysis confirms that the TiO{sub x} films are nearly stoichiometric, have no significant level of contaminants, and are of amorphous nature. The passivation is found to be stable after storage in the dark for eight months. These results demonstrate that TiO{sub x} films are also capable of providing excellent passivation of undiffused c-Si surfaces on a comparable level to thermal silicon oxide, silicon nitride, and aluminum oxide. In addition, it is well known that TiO{sub x} has an optimal refractive index of 2.4 in the visible range for glass encapsulated solar cells, as well as a low extinction coefficient. Thus, the results presented in this work could facilitate the re-emergence of TiO{sub x} in the field of high-efficiency silicon wafer solar cells.

  8. In situ surface monitoring system for synchrotron mirrors under high heat load.

    Science.gov (United States)

    Mui, P H; Srajer, G; Mills, D M

    1997-08-01

    A portable electro-optical system capable of real-time measurements of surface slope distortions down to 0.5 murad is described; the system is limited primarily by its short-term stability. The system employs an angle measurement technique that, in combination with the least-squares signal extraction method, reduces system fluctuations. In addition, a multireflection technique is used to enhance the detectable resolution. Although designed for use with mirrors for synchrotron radiation sources, this system has the flexibility to be applied to other optical components. The prototype system has been tested on a sample mirror piece, and preliminary results are presented. A brief discussion about the extension of this metrology unit to adaptive optics is also given.

  9. Constraining surface carbon fluxes using in situ measurements of carbonyl sulfide and carbon dioxide

    Science.gov (United States)

    Berkelhammer, M.; Asaf, D.; Still, C.; Montzka, S.; Noone, D.; Gupta, M.; Provencal, R.; Chen, H.; Yakir, D.

    2014-02-01

    Understanding the processes that control the terrestrial exchange of carbon is critical for assessing atmospheric CO2 budgets. Carbonyl sulfide (COS) is taken up by vegetation during photosynthesis following a pathway that mirrors CO2 but has a small or nonexistent emission component, providing a possible tracer for gross primary production. Field measurements of COS and CO2 mixing ratios were made in forest, senescent grassland, and riparian ecosystems using a laser absorption spectrometer installed in a mobile trailer. Measurements of leaf fluxes with a branch-bag gas-exchange system were made across species from 10 genera of trees, and soil fluxes were measured with a flow-through chamber. These data show (1) the existence of a narrow normalized daytime uptake ratio of COS to CO2 across vascular plant species of 1.7, providing critical information for the application of COS to estimate photosynthetic CO2 fluxes and (2) a temperature-dependent normalized uptake ratio of COS to CO2 from soils. Significant nighttime uptake of COS was observed in broad-leafed species and revealed active stomatal opening prior to sunrise. Continuous high-resolution joint measurements of COS and CO2 concentrations in the boundary layer are used here alongside the flux measurements to partition the influence that leaf and soil fluxes and entrainment of air from above have on the surface carbon budget. The results provide a number of critical constraints on the processes that control surface COS exchange, which can be used to diagnose the robustness of global models that are beginning to use COS to constrain terrestrial carbon exchange.

  10. In situ measurement of airway surface liquid [K+] using a ratioable K+-sensitive fluorescent dye.

    Science.gov (United States)

    Namkung, Wan; Song, Yuanlin; Mills, Aaron D; Padmawar, Prashant; Finkbeiner, Walter E; Verkman, A S

    2009-06-05

    The airway surface liquid (ASL) is the thin fluid layer lining airway surface epithelial cells, whose volume and composition are tightly regulated and may be abnormal in cystic fibrosis (CF). We synthesized a two-color fluorescent dextran to measure ASL [K(+)], TAC-Lime-dextran-TMR, consisting of a green-fluorescing triazacryptand K(+) ionophore-Bodipy conjugate, coupled to dextran, together with a red fluorescing tetramethylrhodamine reference chromophore. TAC-Lime-dextran-TMR fluorescence was K(+)-selective, increasing >4-fold with increasing [K(+)] from 0 to 40 mm. In well differentiated human airway epithelial cells, ASL [K(+)] was 20.8 +/- 0.3 mm and decreased by inhibition of the Na(+)/K(+) pump (ouabain), ENaC (amiloride), CF transmembrane conductance regulator (CFTR(inh)-172), or K(+) channels (TEA or XE991). ASL [K(+)] was increased by forskolin but not affected by Na(+)/K(+)/2Cl(-) cotransporter inhibition (bumetanide). Functional and expression studies indicated the involvement of [K(+)] channels KCNQ1, KCNQ3, and KCNQ5 as determinants of ASL [K(+)]. [K(+)] in CF cultures was similar to that in non-CF cultures, suggesting that abnormal ASL [K(+)] is not a factor in CF lung disease. In intact airways, ASL [K(+)] was also well above extracellular [K(+)]: 22 +/- 1 mm in pig trachea ex vivo and 16 +/- 1 mm in mouse trachea in vivo. Our results provide the first noninvasive measurements of [K(+)] in the ASL and indicate the involvement of apical and basolateral membrane ion transporters in maintaining a high ASL [K(+)].

  11. Intermatrix Synthesis as a rapid, inexpensive and reproducible methodology for the in situ functionalization of nanostructured surfaces with quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Bastos-Arrieta, Julio, E-mail: julio.bastos@upc.edu [Department of Chemical Engineering, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Muñoz, Jose, E-mail: josemaria.munoz@uab.cat [Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Stenbock-Fermor, Anja, E-mail: stenbock@dwi.rwth-aachen.de [DWI – Leibniz-Institut für Interaktive Materialien, Aachen 52056 (Germany); Muñoz, Maria, E-mail: Maria.Munoz@uab.cat [Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Muraviev, Dmitri N., E-mail: Dimitri.Muraviev@uab.es [Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Céspedes, Francisco, E-mail: francisco.cespedes@uab.cat [Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Tsarkova, Larisa A., E-mail: tsarkova@dwi.rwth-aachen.de [DWI – Leibniz-Institut für Interaktive Materialien, Aachen 52056 (Germany); Baeza, Mireia, E-mail: MariaDelMar.Baeza@uab.cat [Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain)

    2016-04-15

    Graphical abstract: - Highlights: • Nanodiamond functionalization with CdS quantum dots. • Approach for carbon nanotube detection in water samples. • Simple functionalization of thin polymeric nanolayers with quantum dots. - Abstract: Intermatrix Synthesis (IMS) technique has proven to be a valid methodology for the in situ incorporation of quantum dots (QDs) in a wide range of nanostructured surfaces for the preparation of advanced hybrid-nanomaterials. In this sense, this communication reports the recent advances in the application of IMS for the synthesis of CdS-QDs with favourable distribution on sulfonated polyetherether ketone (SPEEK) membrane thin films (TFs), multiwall carbon nanotubes (MWCNTs) and nanodiamonds (NDs). The synthetic route takes advantage of the ion exchange functionality of the reactive surfaces for the loading of the QDs precursor and consequent QDs appearance by precipitation. The benefits of such modified nanomaterials were studied using CdS-QDs@MWCNTs hybrid-nanomaterials. CdS-QDs@MWCNTs has been used as conducting filler for the preparation of electrochemical nanocomposite sensors, which present electrocatalytic properties. Finally, the optical properties of the QDs contained on MWCNTs could allow a new procedure for the analytical detection of nanostructured carbon allotropes in water.

  12. Intermatrix Synthesis as a rapid, inexpensive and reproducible methodology for the in situ functionalization of nanostructured surfaces with quantum dots

    Science.gov (United States)

    Bastos-Arrieta, Julio; Muñoz, Jose; Stenbock-Fermor, Anja; Muñoz, Maria; Muraviev, Dmitri N.; Céspedes, Francisco; Tsarkova, Larisa A.; Baeza, Mireia

    2016-04-01

    Intermatrix Synthesis (IMS) technique has proven to be a valid methodology for the in situ incorporation of quantum dots (QDs) in a wide range of nanostructured surfaces for the preparation of advanced hybrid-nanomaterials. In this sense, this communication reports the recent advances in the application of IMS for the synthesis of CdS-QDs with favourable distribution on sulfonated polyetherether ketone (SPEEK) membrane thin films (TFs), multiwall carbon nanotubes (MWCNTs) and nanodiamonds (NDs). The synthetic route takes advantage of the ion exchange functionality of the reactive surfaces for the loading of the QDs precursor and consequent QDs appearance by precipitation. The benefits of such modified nanomaterials were studied using CdS-QDs@MWCNTs hybrid-nanomaterials. CdS-QDs@MWCNTs has been used as conducting filler for the preparation of electrochemical nanocomposite sensors, which present electrocatalytic properties. Finally, the optical properties of the QDs contained on MWCNTs could allow a new procedure for the analytical detection of nanostructured carbon allotropes in water.

  13. Influence of microleakage, surface roughness and biofilm control on secondary caries formation around composite resin restorations: an in situ evaluation

    Directory of Open Access Journals (Sweden)

    Fábio Garcia Lima

    2009-02-01

    Full Text Available This study was carried out to evaluate in situ the influence of microleakage, surface roughness and biofilm control on caries formation around composite resin restorations. During 28 days, 12 volunteers wore palatal devices containing bovine enamel slabs restored with composite resin. Restorations were made without leakage, when the adhesive system was applied, or with leakage, when adhesive system was omitted. Half of the restorations in each group were finished and the remaining were finished and polished. In one side of the palatal device, biofilm was left to accumulate over the restored slabs, and in the other side dental slabs were brushed, to allow biofilm removal. There was an extraoral application of 20% sucrose solution (8x/day over the enamel slabs. The formation of caries lesions (white spots was evaluated by visual inspection under stereomicroscopy. Additionally, the dental slabs were sectioned and observed under polarized light microscopy. Data were submitted to Kruskal-Wallis test and Spearman's correlation test at 5% significance level. Polishing and bonding were not significant factors regarding white spot formation (p>0.05. Biofilm control (brushing was associated with reduction of caries formation close to the restorations (p<0.01. Polarized light microscopy confirmed the visual inspection findings. These results suggest that while microleakage and surface roughness did not influence caries lesion formation, biofilm control may prevent the enamel demineralization.

  14. Influence of microleakage, surface roughness and biofilm control on secondary caries formation around composite resin restorations: an in situ evaluation.

    Science.gov (United States)

    Lima, Fábio Garcia; Romano, Ana Regina; Correa, Marcos Britto; Demarco, Flávio Fernando

    2009-01-01

    This study was carried out to evaluate in situ the influence of microleakage, surface roughness and biofilm control on caries formation around composite resin restorations. During 28 days, 12 volunteers wore palatal devices containing bovine enamel slabs restored with composite resin. Restorations were made without leakage, when the adhesive system was applied, or with leakage, when adhesive system was omitted. Half of the restorations in each group were finished and the remaining were finished and polished. In one side of the palatal device, biofilm was left to accumulate over the restored slabs, and in the other side dental slabs were brushed, to allow biofilm removal. There was an extraoral application of 20% sucrose solution (8x/day) over the enamel slabs. The formation of caries lesions (white spots) was evaluated by visual inspection under stereomicroscopy. Additionally, the dental slabs were sectioned and observed under polarized light microscopy. Data were submitted to Kruskal-Wallis test and Spearman's correlation test at 5% significance level. Polishing and bonding were not significant factors regarding white spot formation (p>0.05). Biofilm control (brushing) was associated with reduction of caries formation close to the restorations (p<0.01). Polarized light microscopy confirmed the visual inspection findings. These results suggest that while microleakage and surface roughness did not influence caries lesion formation, biofilm control may prevent the enamel demineralization.

  15. In situ Surface Tailoring with Zwitterionic Carboxybetaine Moieties on Self-Assembled Thin Film for Antifouling Biointerfaces

    Directory of Open Access Journals (Sweden)

    Chun-Jen Huang

    2013-12-01

    Full Text Available A novel biointerface bearing zwitterionic carboxybetaine moieties was developed for effective resistance to nonspecific adsorption of proteins and blood cells. Self-assembled thin films (SAFs of (N,N-dimethylaminopropyl trimethoxysilane were formed as mattress layers by either vapor or solution deposition. Subsequently, the tertiary amine head groups on SAFs were reacted with β-propiolactone to give zwitterionic carboxybetaine moieties via in situ synthesis. The optimal reaction time of 8 h for both preparation methods was verified by static contact angle measurements. According to the X-ray photoelectron spectroscopy, 67.3% of amine groups on SAFs prepared from the vapor deposition was converted to the zwitterionic structures after reaction of β-propiolactone. The antifouling properties of the zwitterionic biointerfaces were quantitatively evaluated in the presence of protein solutions using a quartz crystal microbalance with dissipation, showing a great improvement by factors of 6.5 and 20.2 from tertiary amine SAFs and bare SiO2 surfaces, respectively. More importantly, the zwitterionic SAFs were brought to contact with undiluted human blood in chaotic-mixer microfluidic systems; the results present their capability to effectively repel blood cell adhesion. Accordingly, in this work, development of carboxybetaine SAFs offers a facile yet effective strategy to fabricate biocompatible biointerfaces for a variety of potential applications in surface coatings for medical devices.

  16. In situ surface-enhanced Raman spectroscopy effect in zeolite due to Ag2Se quantum dots

    Science.gov (United States)

    Martinez-Nuñez, C. E.; Cortez-Valadez, M.; Delgado-Beleño, Y.; Flores-López, N. S.; Román-Zamorano, J. F.; Flores-Valenzuela, J.; Flores-Acosta, M.

    2017-02-01

    This study shows the presence of surface-enhanced Raman spectroscopy (SERS) effect caused by Ag2Se quantum dots embedded in the zeolite matrix. The quantum dots that were synthesised and stabilised in the matrix of F9-NaX zeolite show a size of 5 nm and a quasi-spherical morphology. The calculated interplanar distances confirm the presence of quantum dots in cubic phase Im-m. We suppose that the in situ SERS effect in the material is caused by chemical-enhancement mechanism (CEM). The density functional theory (DFT) is undertaken to corroborate our hypothesis. The structure H8Si8Al8O12 represents the zeolite cavity unit, and small clusters of (Ag2Se) n represent the quantum dots. Both structures interact in the cavity to obtain the local minimum of the potential energy surface, leading to new molecular orbitals. After the analysis of the predicted Raman spectrum, the Raman bands increase significantly, agreeing with the experimental results at low wavenumbers in F9-NaX zeolite.

  17. Dynamic stability of passive dynamic walking on an irregular surface.

    Science.gov (United States)

    Su, Jimmy Li-Shin; Dingwell, Jonathan B

    2007-12-01

    Falls that occur during walking are a significant health problem. One of the greatest impediments to solve this problem is that there is no single obviously "correct" way to quantify walking stability. While many people use variability as a proxy for stability, measures of variability do not quantify how the locomotor system responds to perturbations. The purpose of this study was to determine how changes in walking surface variability affect changes in both locomotor variability and stability. We modified an irreducibly simple model of walking to apply random perturbations that simulated walking over an irregular surface. Because the model's global basin of attraction remained fixed, increasing the amplitude of the applied perturbations directly increased the risk of falling in the model. We generated ten simulations of 300 consecutive strides of walking at each of six perturbation amplitudes ranging from zero (i.e., a smooth continuous surface) up to the maximum level the model could tolerate without falling over. Orbital stability defines how a system responds to small (i.e., "local") perturbations from one cycle to the next and was quantified by calculating the maximum Floquet multipliers for the model. Local stability defines how a system responds to similar perturbations in real time and was quantified by calculating short-term and long-term local exponential rates of divergence for the model. As perturbation amplitudes increased, no changes were seen in orbital stability (r(2)=2.43%; p=0.280) or long-term local instability (r(2)=1.0%; p=0.441). These measures essentially reflected the fact that the model never actually "fell" during any of our simulations. Conversely, the variability of the walker's kinematics increased exponentially (r(2)>or=99.6%; pwalking stability are related to each other and to risk of falling.

  18. Estimation of surface heat and moisture fluxes over a prairie grassland. I - In situ energy budget measurements incorporating a cooled mirror dew point hygrometer

    Science.gov (United States)

    Smith, Eric A.; Crosson, William L.; Tanner, Bertrand D.

    1992-01-01

    Attention is focused on in situ measurements taken during FIFE required to support the development and validation of a biosphere model. Seasonal time series of surface flux measurements obtained from two surface radiation and energy budget stations utilized to support the FIFE surface flux measurement subprogram are examined. Data collection and processing procedures are discussed along with the measurement analysis for the complete 1987 test period.

  19. Development of an FTIR in situ reactor for real time study of surface reactions in photocatalysis

    Science.gov (United States)

    Hauchecorne, Birger

    For many years, photocatalysis has been proposed as one of the promising techniques to abate environmental pollutants. To improve the catalytic efficiency, it is vital to know the reaction mechanisms of the photocatalytic degradation. Different methods are therefore described in literature to study these mechanisms at the gaseous phase/photocatalyst interface with Fourier transform infrared (FTIR) spectroscopy as a commonly used method. The reactors described in literature and/or available on the market experience some technical and scientific difficulties. Generally, the catalyst can only be investigated after the reactions have occurred, or it is only possible to look at the changes in the gas phase concentrations while the reactions are taking place. It is thus a major challenge to develop a reactor which makes it possible to detect changes on the catalyst surface at the moment the reactions are happening. In this work, a new reactor is developed that makes it possible to study the catalytic surface at the moment the reactions occur, by means of transmission-absorption FTIR spectroscopy. Moreover, by using UV LEDs, it was possible to install the UV light inside the reactor area, so that no harmful UV light can leave the reactor, inherently making it a safer method. It was also opted to construct the reactor in a modular way, so that every part was interchangeable and could easily be replaced according to the needs of the researcher. A special screw cap is designed to hold the UV LEDs on a printed circuit board and to fit in every standard FTIR spectrometer. This study provides exciting new insights in the photocatalytic degradation mechanism of ethylene and acetaldehyde. It is for instance found that OH radicals are used as the oxidising agents to abate these pollutants. For ethylene it was proven that the molecular orbitals play an important role, resulting in the formation of both formaldehyde and formic acid as intermediates before complete mineralisation

  20. Microstructure, microhardness and wear resistance of VC{sub p}/Fe surface composites fabricated in situ

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Fangxia [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Institute of Wear Resistant Materials, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Hojamberdiev, Mirabbos [Institute of Wear Resistant Materials, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Xu, Yunhua, E-mail: yunhuaxu@yahoo.com.cn [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Institute of Wear Resistant Materials, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Zhong, Lisheng [Institute of Wear Resistant Materials, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Zhao, Nana [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Li, Yaping [Institute of Wear Resistant Materials, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Huang, Xing [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China)

    2013-09-01

    Graphical The vanadium carbide particles (VC{sub p})/Fe surface composites were in situ fabricated by a technique combining infiltration casting with subsequent heat treatment. The effects of different heat treatment times on the phase evolution, microstructure, microhardness and wear resistance of the composite were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness tester and wear resistance testing instrument, respectively. The results show that only graphite, α-Fe and V{sub 8}C{sub 7} phases dominate in the composite after being heat treated at 1164 °C for 3 h. The amount of V{sub 8}C{sub 7} decreases gradually from the top surface of the composite to the matrix mainly composed of gray cast iron. The average microhardness of the VC{sub p}/Fe surface composites varies according to the different reaction zones as follows: 505 HV{sub 0.1} (vanadium plate), 1096 HV{sub 0.1} (composite region), and 235 HV{sub 0.1} (iron matrix). The microhardness of the composite region is four times higher than that of the iron matrix and two times higher than that of the vanadium plate. This is attributed to the formation of vanadium carbide (V{sub 2}C and V{sub 8}C{sub 7}) crystallites as reinforcement phases within the iron matrix. The VC{sub p}/Fe surface composites exhibit a good wear resistance under two-body abrasive wear test.

  1. Using in situ X-ray reflectivity to study protein adsorption on hydrophilic and hydrophobic surfaces: benefits and limitations.

    Science.gov (United States)

    Richter, Andrew G; Kuzmenko, Ivan

    2013-04-30

    We have employed in situ X-ray reflectivity (IXRR) to study the adsorption of a variety of proteins (lysozyme, cytochrome c, myoglobin, hemoglobin, serum albumin, and immunoglobulin G) on model hydrophilic (silicon oxide) and hydrophobic surfaces (octadecyltrichlorosilane self-assembled monolayers), evaluating this recently developed technique for its applicability in the area of biomolecular studies. We report herein the highest resolution depiction of adsorbed protein films, greatly improving on the precision of previous neutron reflectivity (NR) results and previous IXRR studies. We were able to perform complete scans in 5 min or less with the maximum momentum transfer of at least 0.52 Å(-1), allowing for some time-resolved information about the evolution of the protein film structure. The three smallest proteins (lysozyme, cytochrome c, and myoglobin) were seen to deposit as fully hydrated, nondenatured molecules onto hydrophilic surfaces, with indications of particular preferential orientations. Time evolution was observed for both lysozyme and myoglobin films. The larger proteins were not observed to deposit on the hydrophilic substrates, perhaps because of contrast limitations. On hydrophobic surfaces, all proteins were seen to denature extensively in a qualitatively similar way but with a rough trend that the larger proteins resulted in lower coverage. We have generated high-resolution electron density profiles of these denatured films, including capturing the growth of a lysozyme film. Because the solution interface of these denatured films is diffuse, IXRR cannot unambiguously determine the film extent and coverage, a drawback compared to NR. X-ray radiation damage was systematically evaluated, including the controlled exposure of protein films to high-intensity X-rays and exposure of the hydrophobic surface to X-rays before adsorption. Our analysis showed that standard measuring procedures used for XRR studies may lead to altered protein films

  2. Confronting AeroCom models with particle size distribution data from surface in situ stations

    Science.gov (United States)

    Platt, Stephen; Fiebig, Markus; Mann, Graham; Schulz, Michael

    2016-04-01

    The size distribution is the most important property for describing any interaction of an aerosol particle population with its surroundings. In first order, it determines both, the aerosol optical properties quantifying the direct aerosol climate effect, and the fraction of aerosol particles acting as cloud condensation nuclei quantifying the indirect aerosol climate effect. Aerosol schemes of modern climate models resolve the aerosol particle size distribution (APSD) explicitly. In improving the skill of climate models, it is therefore highly useful to confront these models with precision APSD data observed at surface stations. Corresponding previous work focussed on comparing size integrated, seasonal particle concentrations at selected sites with ensemble model averages to assess overall model skill. Building on this work, this project intends to refine the approach by comparing median particle size and integral concentration of fitted modal size distributions. It will also look at skill differences between models in order to find reasons for matches and discrepancies. The presentation will outline the project, and will elaborate on input requested from modelling groups to participate in the exercise.

  3. Optical antenna arrays on a fiber facet for in situ surface-enhanced Raman scattering detection.

    Science.gov (United States)

    Smythe, Elizabeth J; Dickey, Michael D; Bao, Jiming; Whitesides, George M; Capasso, Federico

    2009-03-01

    This paper reports a bidirectional fiber optic probe for the detection of surface-enhanced Raman scattering (SERS). One facet of the probe features an array of gold optical antennas designed to enhance Raman signals, while the other facet of the fiber is used for the input and collection of light. Simultaneous detection of benzenethiol and 2-[(E)-2-pyridin-4-ylethenyl]pyridine is demonstrated through a 35 cm long fiber. The array of nanoscale optical antennas was first defined by electron-beam lithography on a silicon wafer. The array was subsequently stripped from the wafer and then transferred to the facet of a fiber. Lithographic definition of the antennas provides a method for producing two-dimensional arrays with well-defined geometry, which allows (i) the optical response of the probe to be tuned and (ii) the density of "hot spots" generating the enhanced Raman signal to be controlled. It is difficult to determine the Raman signal enhancement factor (EF) of most fiber optic Raman sensors featuring hot spots because the geometry of the Raman enhancing nanostructures is poorly defined. The ability to control the size and spacing of the antennas enables the EF of the transferred array to be estimated. EF values estimated after focusing a laser directly onto the transferred array ranged from 2.6 x 10(5) to 5.1 x 10(5).

  4. In situ characterisation of a microorganism surface by Raman microspectroscopy: the shell of Ascaris eggs.

    Science.gov (United States)

    Quilès, Fabienne; Balandier, Jean-Yves; Capizzi-Banas, Sandrine

    2006-09-01

    Intestinal nematodes are very common human parasites and a single species, Ascaris lumbricoïdes, is estimated to infect a quarter of the world's population. A sticky external layer covers their eggs. This work shows that Raman vibrational confocal spectroscopy is able to give information on the biochemical composition of the shell of Ascaris eggs. The biochemical localised characterisation of Ascaris eggs was performed directly on the eggs in their aqueous environment. The studied parasites came from two origins: dissections of adult females and extractions from biosolid sludges. The presence of mucopolysaccharides, proteins and chitin in the shell was demonstrated. The presence of ascaroside compounds was shown particularly via the narrow and intense bands from the organised long CH2 chains. To the best of our knowledge, this is the first time that the latter have been observed in Raman vibrational spectra of microorganisms. Hydration of the shell was different depending on the intensity of the colour of the sludge eggs. Knowledge of the biochemical structural properties of egg surfaces would be useful to understand the egg adhesion phenomena on vegetables contaminated by reused wastewater.

  5. In situ surface hydrogenation synthesis of Ti3+ self-doped TiO2 with enhanced visible light photoactivity

    Science.gov (United States)

    Huo, Junchao; Hu, Yanjie; Jiang, Hao; Li, Chunzhong

    2014-07-01

    A novel one-step, vapor-fed aerosol flame synthetic process (VAFS) has been developed to prepare Ti3+ self-doped titanium dioxide (TiO2). The freshly formed TiO2 was in situ surface hydrogenated during the condensation stage by introducing H2 above the flame, and Ti3+ ions were created near the surface of TiO2. The relative content of Ti3+ ions near the surface of TiO2 is estimated to be 8%. Because of the high absorption of visible light and suppression of charge recombination, the photocurrent density and decomposition of MB under visible light irradiation were remarkably enhanced. This study demonstrates a simple, potential method to produce Ti3+ self-doped TiO2 with effective photoactivity in visible light.A novel one-step, vapor-fed aerosol flame synthetic process (VAFS) has been developed to prepare Ti3+ self-doped titanium dioxide (TiO2). The freshly formed TiO2 was in situ surface hydrogenated during the condensation stage by introducing H2 above the flame, and Ti3+ ions were created near the surface of TiO2. The relative content of Ti3+ ions near the surface of TiO2 is estimated to be 8%. Because of the high absorption of visible light and suppression of charge recombination, the photocurrent density and decomposition of MB under visible light irradiation were remarkably enhanced. This study demonstrates a simple, potential method to produce Ti3+ self-doped TiO2 with effective photoactivity in visible light. Electronic supplementary information (ESI) available: Schematic setup for Ti3+ self-doped TiO2 nanoparticles is shown in Fig. S1. The BET specific surface and pore-size distribution of Ti3+ self-doped TiO2 is shown in Fig. S2. XRD patterns of pristine TiO2 and Ti3+ self-doped TiO2 are shown in Fig. S3. HRTEM image of Ti3+ self-doped TiO2 with mixture phase is shown in Fig. S4. The photographs of different colors of Ti3+ self-doped TiO2 with different flow rates of hydrogen are shown in Fig. S5. TEM images of Ti3+ self-doped TiO2 samples with different

  6. Analysis of selected surface characteristics and latent heat storage for passive solar space heating

    Energy Technology Data Exchange (ETDEWEB)

    Fthenakis, V.; Leigh, R.

    1981-12-01

    Results are presented of an analysis of the value of various technical improvements in the solar collector and thermal storage subsystems of passive solar residential, agricultural, and industrial systems for two regions of the country. The evaluated improvements are: decreased emissivity and increased absorptivity of absorbing surfaces, decreased reflectivity, and decreased emissivity of glazing surface, and the substitution of sensible heat storage media with phase change materials. The value of each improvement is estimated by the additional energy savings resulting from the improvement.

  7. In situ monitoring of laser-induced periodic surface structures formation on polymer films by grazing incidence small-angle X-ray scattering

    NARCIS (Netherlands)

    Rebollar, Esther; Rueda, Daniel R; Martín-Fabiani, Ignacio; Rodríguez-Rodríguez, Álvaro; García-Gutiérrez, Mari-Cruz; Portale, Giuseppe; Castillejo, Marta; Ezquerra, Tiberio A

    2015-01-01

    The formation of laser-induced periodic surface structures (LIPSS) on model spin-coated polymer films has been followed in situ by grazing incidence small-angle X-ray scattering (GISAXS) using synchrotron radiation. The samples were irradiated at different repetition rates ranging from 1 up to 10 Hz

  8. In situ surface X-ray diffraction studies of the copper-electrolyte interface. Atomic structure and homoepitaxial grwoth

    Energy Technology Data Exchange (ETDEWEB)

    Golks, Frederik

    2011-05-19

    Copper electrodeposition is the predominantly used technique for on-chip wiring in the fabrication of ultra-large scale integrated (ULSI) microchips. In this 'damascene copper electroplating' process, multicomponent electrolytes containing organic additives realize void-free filling of trenches with high aspect ratio ('superconformal deposition'). Despite manifold studies, motivated by the continuous trend to shrink wiring dimensions and thus the demand of optimized plating baths, detailed knowledge on the growth mechanism - in presence and absence of additives - is still lacking. Using a recently developed hanging meniscus X-ray transmission cell, brilliant synchrotron x-rays and a fast, one-dimensional detector system, unique real-time in situ surface X-ray diffraction studies of copper electrodeposition were performed under realistic reaction conditions, approaching rates of technological relevance. Preparatory measurements of the electrochemical dissolution of Au(001) in chloride-containing electrolyte demonstrated the capability of this powerful technique, specifically the possibility to follow atomic-scale deposition or dissolution processes with a time resolution down to five milliseconds. The electrochemical as well as structural characterization of the Cu(001)- and Cu(111)-electrolyte interfaces provided detailed insight into the complex atomic-scale structures in presence of specifically adsorbed chloride on these surfaces. The interface of Cu(001) in chloride-containing electrolyte exhibits a continuous surface phase transition of a disordered Cl adlayer to a c(2 x 2) Cl adlayer with increasing potential. The latter was found to induce a small vertical corrugation of substrate atoms, which can be ascribed to lattice relaxations induced by the presence of coadsorbed water molecules and cations in the outer part of the electrochemical double layer. The study of the specific adsorption of chloride on Cu(111) from acidic aqueous

  9. Miniaturized Laser-Induced Breakdown Spectroscopy for the in-situ analysis of the Martian surface: Calibration and quantification

    Energy Technology Data Exchange (ETDEWEB)

    Rauschenbach, I., E-mail: irausch@uni-muenster.d [Institut fuer Planetologie, Westfaelische Wilhelms-Universitaet, Wilhelm-Klemm-Strasse 10, 48149 Muenster (Germany); Jessberger, E.K. [Institut fuer Planetologie, Westfaelische Wilhelms-Universitaet, Wilhelm-Klemm-Strasse 10, 48149 Muenster (Germany); Pavlov, S.G. [Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin (Germany); Huebers, H.-W. [Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin (Germany); Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

    2010-08-15

    We report on our ongoing studies to develop Laser-Induced Breakdown Spectroscopy (LIBS) for planetary surface missions to Mars and other planets and moons, like Jupiter's moon Europa or the Earth's moon. Since instruments for space missions are severely mass restricted, we are developing a light-weight miniaturized close-up LIBS instrument to be installed on a lander or rover for the in-situ geochemical analysis of planetary surface rocks and coarse fines. The total mass of the instrument will be {approx} 1 kg in flight configuration. Here we report on a systematic performance study of a LIBS instrument equipped with a prototype laser of 216 g total mass and an energy of 1.8 mJ. The LIBS measurements with the prototype laser and the comparative measurements with a regular 40 mJ laboratory laser were both performed under Martian atmospheric conditions. We calibrated 14 major and minor elements by analyzing 18 natural samples of certified composition. The calibration curves define the limits of detection that are > 5 ppm for the lab laser and > 400 ppm for the prototype laser, reflecting the different analyzed sample masses of {approx} 20 {mu}g and {approx} 2 {mu}g, respectively. To test the accuracy we compared the LIBS compositions, determined with both lasers, of Mars analogue rocks with certified or independently measured compositions and found agreements typically within 10-20%. In addition we verified that dust coverage is effectively removed from rock surfaces by the laser blast. Our study clearly demonstrates that a close-up LIBS instrument (spot size {approx} 50 {mu}m) will decisively enhance the scientific output of planetary lander missions by providing a very large number of microscopic elemental analyses.

  10. In-situ buildup of cosmogenic isotopes at the earth`s surface: measurement of erosion rates and exposure times

    Energy Technology Data Exchange (ETDEWEB)

    Fifield, L.K.; Allan, G.L.; Stone, J.O.H.; Evans, J.M.; Cresswell, R.G.; Ophel, T.R. [Australian National Univ., Canberra, ACT (Australia)

    1993-12-31

    Cosmic rays produce a number of nuclides in rocks that can be used to determine the geomorphic history of surfaces. The most useful are the radioactive isotopes {sup 10}Be (t{sub 1/2} = 1.5Ma), {sup 26}Al (0.7Ma) and {sup 36}Cl (0.3Ma). Within the top 2m of the surface, these are produced principally by fast neutrons. At greater depths, production is dominated by the capture of negative muons. Measurements of a single nuclide produced in situ can be used to determine total exposure times or erosion rates. The use of multiple nuclides with different half-lives makes it possible to determine more complex histories, such as exposures interrupted by periods of burial. At the ANU, all three of the isotopes above are being used to study a variety of problems in geomorphology and paleoclimatology, although to date, most of the work has concentrated on {sup 36}Cl. The accumulation of cosmogenic {sup 36}Cl in calcite (CaCO{sub 3}) provides a means of measuring erosion rates on limestone surfaces. Sensitivity is achieved over a wide range of erosion rates due to the high production rate of {sup 36}Cl in calcite (typically greater than 30 atoms/g/yr) and a detection limit of ca. 5000 atoms/g attainable with the ANU AMS system. The method is simplified by the predominance of Ca reactions (principally spallation) over other sources of {sup 36}Cl in calcite, and the ease of sample preparation. This presentation discuss the results of measurements of {sup 36}Cl in calcite from limestone samples from Australia and Papua New Guinea. Erosion rates derived from these measurements range from 3 microns per year (Australia) to over 200 microns per year in the New Guinea highlands. 3 refs.

  11. Advances in Raman spectroscopy for In Situ Identification of Minerals and Organics on Diverse Planetary Surfaces: from Mars to Titan

    Science.gov (United States)

    Blacksberg, J.; Alerstam, E.; Maruyama, Y.; Cochrane, C.; Rossman, G. R.

    2015-12-01

    We present recent developments in time-resolved Raman spectroscopy for in situ planetary surface exploration, aimed at identification of both minerals and organics. Raman is a non-destructive surface technique that requires no sample preparation. Raman spectra are highly material specific and can be used for identification of a wide range of unknown samples. In combination with micro-scale imaging and point mapping, Raman spectroscopy can be used to directly interrogate rocks and regolith materials, while placing compositional analyses within a microtextural context, essential for understanding surface evolutionary pathways. Due to these unique capabilities, Raman spectroscopy is of great interest for the exploration of all rocky and icy bodies, for example Mars, Venus, the Moon, Mars' moons, asteroids, comets, Europa, and Titan. In this work, we focus on overcoming one of the most difficult challenges faced in Raman spectroscopy: interference from background fluorescence of the very minerals and organics that we wish to characterize. To tackle this problem we use time-resolved Raman spectroscopy, which separates the Raman from background processes in the time domain. This same technique also enables operation in daylight without the need for light shielding. Two key components are essential for the success of this technique: a fast solid-state detector and a short-pulse laser. Our detector is a custom developed Single Photon Avalanche Diode (SPAD) array, capable of sub-ns time-gating. Our pulsed lasers are solid-state miniature pulsed microchip lasers. We discuss optimization of laser and detector parameters for our application. We then present Raman spectra of particularly challenging planetary analog samples to demonstrate the unique capabilities of this time-resolved Raman instrument, for example, Mars-analog clays and Titan-analog organics. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a

  12. Organic and inorganic surface passivations of TiO2 nanotube arrays for dye-sensitized photoelectrodes

    Science.gov (United States)

    Park, Hun; Yang, Changduk; Choi, Won-Youl

    2012-10-01

    Surface passivation of photoelectrodes is widely used to improve the performance of dye-sensitized solar cells (DSCs). We use the organic and inorganic materials as a surface-passivating layer of photoelectrodes and introduce the effect of surface passivation on the power conversion efficiency of DSCs. TiO2 nanotube arrays are fabricated by anodic oxidation of Ti foil for photoelectrodes of DSCs. Surface passivating layers are conducted by immersing photoelectrode in various precursor solutions. MgO and WO3 are selected for inorganic passivation. PC61BM is used for organic passivation. In case of inorganic passivation, a basic material (MgO) which has a high isoelectric point (pI >7) shows higher power conversion efficiency of 2.63% by increasing of open circuit voltage (Voc) to 0.74 V than bare sample of 2.55%. But, an acidic material (WO3) shifts Voc to low potential resulting in a worse efficiency of DSCs. In case of organic passivation, PC61BM enhances photocurrents and decreases Voc value compared to bare sample. The power conversion efficiency of PC61BM-coated DSCs is overall improved due to enhanced photocurrents despite of Voc offset to low potential. Back-transfer electron blocking, dye adsorption, TiO2 conduction band shifting, and additional charge generation by surface passivation are discussed.

  13. Electrochemistry and in situ scanning tunnelling microscopy of pure and redox-marked DNA- and UNA-based oligonucleotides on Au(111)-electrode surfaces

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Salvatore, Princia; Karlsen, K.

    2013-01-01

    We have studied adsorption and electrochemical electron transfer of several 13- and 15-base DNA and UNA (unlocked nucleic acids) oligonucleotides (ONs) linked to Au(111)-electrode surfaces via a 50-C6-SH group using cyclic voltammetry (CV) and scanning tunnelling microscopy in aqueous buffer under...... electrochemical potential control (in situ STM). 2,20,60,200-Terpyridine (terpy) onto which the transition metal ions Fe2+/3+, Os2+/3+ and Ru2+/3+ could be coordinated after UNA monolayer formation was attached to UNA via a flexible linker. The metal centres offer CV probes and in situ STM contrast markers...

  14. Early Career. Harnessing nanotechnology for fusion plasma-material interface research in an in-situ particle-surface interaction facility

    Energy Technology Data Exchange (ETDEWEB)

    Allain, Jean Paul [Univ. of Illinois, Champaign, IL (United States)

    2014-08-08

    This project consisted of fundamental and applied research of advanced in-situ particle-beam interactions with surfaces/interfaces to discover novel materials able to tolerate intense conditions at the plasma-material interface (PMI) in future fusion burning plasma devices. The project established a novel facility that is capable of not only characterizing new fusion nanomaterials but, more importantly probing and manipulating materials at the nanoscale while performing subsequent single-effect in-situ testing of their performance under simulated environments in fusion PMI.

  15. Surface Passivation and Antireflection Behavior of ALD on n-Type Silicon for Solar Cells

    Directory of Open Access Journals (Sweden)

    Ing-Song Yu

    2013-01-01

    Full Text Available Atomic layer deposition, a method of excellent step coverage and conformal deposition, was used to deposit TiO2 thin films for the surface passivation and antireflection coating of silicon solar cells. TiO2 thin films deposited at different temperatures (200°C, 300°C, 400°C, and 500°C on FZ n-type silicon wafers are in the thickness of 66.4 nm ± 1.1 nm and in the form of self-limiting growth. For the properties of surface passivation, Si surface is effectively passivated by the 200°C deposition TiO2 thin film. Its effective minority carrier lifetime, measured by the photoconductance decay method, is improved 133% at the injection level of  cm−3. Depending on different deposition parameters and annealing processes, we can control the crystallinity of TiO2 and find low-temperature TiO2 phase (anatase better passivation performance than the high-temperature one (rutile, which is consistent with the results of work function measured by Kelvin probe. In addition, TiO2 thin films on polished Si wafer serve as good ARC layers with refractive index between 2.13 and 2.44 at 632.8 nm. Weighted average reflectance at AM1.5G reduces more than half after the deposition of TiO2. Finally, surface passivation and antireflection properties of TiO2 are stable after the cofire process of conventional crystalline Si solar cells.

  16. Passive remote sensing of large-scale methane emissions from Oil Fields in California's San Joaquin Valley and validation by airborne in-situ measurements - Results from COMEX

    Science.gov (United States)

    Gerilowski, Konstantin; Krautwurst, Sven; Thompson, David R.; Thorpe, Andrew K.; Kolyer, Richard W.; Jonsson, Haflidi; Krings, Thomas; Frankenberg, Christian; Horstjann, Markus; Leifer, Ira; Eastwood, Michael; Green, Robert O.; Vigil, Sam; Fladeland, Matthew; Schüttemeyer, Dirk; Burrows, John P.; Bovensmann, Heinrich

    2016-04-01

    The CO2 and MEthane EXperiment (COMEX) was a NASA and ESA funded campaign in support of the HyspIRI and CarbonSat mission definition activities. As a part of this effort, seven flights were performed between June 3 and September 4, 2014 with the Methane Airborne MAPper (MAMAP) remote sensing instrument (operated by the University of Bremen in cooperation with the German Research Centre for Geosciences - GFZ) over the Kern River, Kern Front, and Poso Creek Oil Fields located in California's San Joaquin Valley. MAMAP was installed for the flights aboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft, together with: a Picarro fast in-situ greenhouse gas (GHG) analyzer operated by the NASA Ames Research Center, ARC; a 5-hole turbulence probe; and an atmospheric measurement package operated by CIRPAS measuring aerosols, temperature, dew-point, and other atmospheric parameters. Three of the flights were accompanied by the Next Generation Airborne Visual InfraRed Imaging Spectrometer (AVIRIS-NG), operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology, installed aboard a second Twin Otter aircraft. Large-scale, high-concentration CH4 plumes were detected by the MAMAP instrument over the fields and tracked over several kilometers. The spatial distribution of the MAMAP observed plumes was compared to high spatial resolution CH4 anomaly maps derived by AVIRIS-NG imaging spectroscopy data. Remote sensing data collected by MAMAP was used to infer CH4 emission rates and their distributions over the three fields. Aggregated emission estimates for the three fields were compared to aggregated emissions inferred by subsequent airborne in-situ validation measurements collected by the Picarro instrument. Comparison of remote sensing and in-situ flux estimates will be presented, demonstrating the ability of airborne remote sensing data to provide accurate emission estimates for concentrations above the

  17. The Reduction of Aqueous Metal Species on the Surfaces of Fe(II)-Containing Oxides: The Role of Surface Passivation

    Science.gov (United States)

    White, A.F.; Peterson, M.L.

    1998-01-01

    The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The rates of metal reduction on natural oxides is strongly dependent on the extent of surface passivation and redox conditions in the weathering environment. Synchrotron studies show that surface oxidation of Fe(II)-containing oxide minerals decreases their capacity for Cr(VI) reduction at hazardous waste disposal sites.

  18. In situ study of electrochemical activation and surface segregation of the SOFC electrode material La0.75Sr0.25Cr0.5Mn0.5O(3±δ).

    Science.gov (United States)

    Huber, Anne-Katrin; Falk, Mareike; Rohnke, Marcus; Luerssen, Bjoern; Gregoratti, Luca; Amati, Matteo; Janek, Jürgen

    2012-01-14

    Mixed-conducting perovskite-type electrodes which are used as cathodes in solid oxide fuel cells (SOFCs) exhibit pronounced performance improvement after cathodic polarization. The current in situ study addresses the mechanism of this activation process which is still unknown. We chose the new perovskite-type material La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±δ) which is a potential candidate for use in symmetrical solid oxide fuel cells (SFCs). We prepared La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±δ) thin film model electrodes on YSZ (111) single crystals by pulsed laser deposition (PLD). Impedance spectroscopy (EIS) measurements show that the kinetics of these electrodes can be drastically improved by applying a cathodic potential. To understand the origin of the enhanced electrocatalytic activity the surfaces of operating LSCrM electrodes were studied in situ (at low pressure) with spatially resolving X-ray photoelectron spectroscopy (μ-ESCA, SPEM) and quasi static secondary ion mass spectrometry (ToF-SIMS) after applying different electrical potentials in the SIMS chamber. We observed that the electrode surfaces which were annealed at 600 °C are enriched significantly in strontium. Subsequent cathodic polarization decreases the strontium surface concentration while anodic polarization increases the strontium accumulation at the electrode surface. We propose a mechanism based on the reversible incorporation of a passivating SrO surface phase into the LSCrM lattice to explain the observed activation/deactivation process.

  19. In Situ Analysis of a Silver Nanoparticle-Precipitating Shewanella Biofilm by Surface Enhanced Confocal Raman Microscopy.

    Directory of Open Access Journals (Sweden)

    Gal Schkolnik

    Full Text Available Shewanella oneidensis MR-1 is an electroactive bacterium, capable of reducing extracellular insoluble electron acceptors, making it important for both nutrient cycling in nature and microbial electrochemical technologies, such as microbial fuel cells and microbial electrosynthesis. When allowed to anaerobically colonize an Ag/AgCl solid interface, S. oneidensis has precipitated silver nanoparticles (AgNp, thus providing the means for a surface enhanced confocal Raman microscopy (SECRaM investigation of its biofilm. The result is the in-situ chemical mapping of the biofilm as it developed over time, where the distribution of cytochromes, reduced and oxidized flavins, polysaccharides and phosphate in the undisturbed biofilm is monitored. Utilizing AgNp bio-produced by the bacteria colonizing the Ag/AgCl interface, we could perform SECRaM while avoiding the use of a patterned or roughened support or the introduction of noble metal salts and reducing agents. This new method will allow a spatially and temporally resolved chemical investigation not only of Shewanella biofilms at an insoluble electron acceptor, but also of other noble metal nanoparticle-precipitating bacteria in laboratory cultures or in complex microbial communities in their natural habitats.

  20. A surface plasmon resonance sensing method for determining captopril based on in situ formation of silver nanoparticles using ascorbic acid

    Science.gov (United States)

    Rastegarzadeh, Saadat; Hashemi, Fatemeh

    2014-03-01

    A new method has been proposed to sensitive detection of captopril based on surface plasmon resonance band of silver nanoparticles (AgNPs). The stable and well-dispersed AgNPs with strong plasmon resonance signal were synthesized in situ using a simple and rapid procedure by applying ascorbic acid as reducer and sodium dodecyl sulfate as stabilizer, at room temperature. It was found that, the decreasing of AgNPs plasmon absorbance is proportional to the concentration of captopril which allows the spectrophotometric sensing of this compound. The presented method is capable of determining captopril over a range of 0.20-2.75 μmol L-1 with a limit of detection 0.07 μmol L-1. The relative standard deviation for eight replicate measurements of 1.00 and 2.50 μmol L-1 of captopril was 2.37% and 1.02%, respectively. The method was applied to the determination of captopril in pharmaceutical formulations with satisfactory results, which were in agreement with those of the official method.

  1. Surface-enhanced in-situ Raman-sensor applied in the arctic area for analyses of water and sediment

    Science.gov (United States)

    Kolomijeca, Anna; Kwon, Yong-Hyok; Kronfeldt, Heinz-Detlef

    2012-06-01

    Investigations on the seafloor in the arctic area are of great scientific interest as well as of progressive economic importance. Therefore, measurements in the water column and of sediments were carried out by applying different analytical methods. In JCR 253 arctic cruise a microsystem diode laser with reflection Bragg grating emitting at 671 nm was introduced and integrated into an optode housing which was laboratory pressure tested up to 200 bar. The connection to the mobile spectrometer is realized through an optical fiber. All performed measurements were carried out on the James-Clark-Ross research vessel during a three week experiment in August 2011. Conventional Raman spectra and SERS spectra of arctic surface water and sediment acquired from locations around 78° N and 9° E will be presented. Selected SERS substrates developed for SERS measurements in sea-water were tested for their capability to detect different substances in the water down to very small (pmol/l) concentrations. Additionally, the applicability of shifted excitation Raman difference spectroscopy (SERDS) and a combination of SERS with SERDS for analytical applications during sea-trials for in-situ analyses of sea-water and sediments will be discussed.

  2. Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

    KAUST Repository

    Chroneos, Alexander I.

    2012-01-26

    In recent years germanium has been emerging as a mainstream material that could have important applications in the microelectronics industry. The principle aim of this study is to review investigations of the diffusion of technologically important p- and n-type dopants as well as surface and interface passivation issues in germanium. The diffusion of impurities in germanium is interrelated to the formation of clusters whenever possible, and possibilities for point defect engineering are discussed in view of recent results. The importance of electrically active defects on the Ge surface and interfaces is addressed considering strategies to suppress them and to passivate the surfaces/interfaces, bearing in mind their importance for advanced devices. © 2012 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Botswana water and surface energy balance research program. Part 2: Large scale moisture and passive microwaves

    Science.gov (United States)

    Vandegriend, A. A.; Owe, M.; Chang, A. T. C.

    1992-01-01

    The Botswana water and surface energy balance research program was developed to study and evaluate the integrated use of multispectral satellite remote sensing for monitoring the hydrological status of the Earth's surface. The research program consisted of two major, mutually related components: a surface energy balance modeling component, built around an extensive field campaign; and a passive microwave research component which consisted of a retrospective study of large scale moisture conditions and Nimbus scanning multichannel microwave radiometer microwave signatures. The integrated approach of both components are explained in general and activities performed within the passive microwave research component are summarized. The microwave theory is discussed taking into account: soil dielectric constant, emissivity, soil roughness effects, vegetation effects, optical depth, single scattering albedo, and wavelength effects. The study site is described. The soil moisture data and its processing are considered. The relation between observed large scale soil moisture and normalized brightness temperatures is discussed. Vegetation characteristics and inverse modeling of soil emissivity is considered.

  4. Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

    Energy Technology Data Exchange (ETDEWEB)

    Chroneos, A.; Dimoulas, A. [MBE Laboratory, Institute of Materials Science, NCSR Demokritos, Athens (Greece); Schwingenschloegl, U. [PSE Division, KAUST, Thuwal (Saudi Arabia)

    2012-04-02

    In recent years germanium has been emerging as a mainstream material that could have important applications in the microelectronics industry. The principle aim of this study is to review investigations of the diffusion of technologically important p- and n-type dopants as well as surface and interface passivation issues in germanium. The diffusion of impurities in germanium is interrelated to the formation of clusters whenever possible, and possibilities for point defect engineering are discussed in view of recent results. The importance of electrically active defects on the Ge surface and interfaces is addressed considering strategies to suppress them and to passivate the surfaces/interfaces, bearing in mind their importance for advanced devices. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Al2O3 Passivation on c-si Surfaces for Low Temperature Solar Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Saynova, D.S.; Janssen, G.J.M.; Burgers, A.R.; Mewe, A.A. [ECN Solar Energy, Westerduinweg 3, NL-1755 LE Petten (Netherlands); Cianci, E.; Seguini, G.; Perego, M. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2,I-20864 Agrate Brianza MB (Italy)

    2013-07-01

    Functional passivation of high resistivity p-type c-Si wafer surfaces was achieved using 10 nm Al2O3 layers and low temperatures for both the thermal ALD process and post-deposition anneal. Effective lifetime values higher than 1 ms were measured at excess carrier density {delta}n=1015 cm{sup -3}. This result was reached in combination with temperatures of 100C and 200C for the Al2O3 layer deposition and anneal, respectively. The Al2O3/c-Si interface was characterized using conductance-voltage and capacitance-voltage measurements. In particular, significantly reduced interface density of the electrically active defects Dit {approx} 2x1010 eV{sup -1}cm{sup -2} was detected, which enabled excellent chemical passivation. The measured density of fixed charges at the interface, Qf, after anneal were in the range +1x10{sup 12} to -1x10{sup 12} cm{sup -2} indicating that both inversion and accumulation conditions result in relevant field-effect passivation using Al2O3 layers and low temperature processes. Numerical simulations on representative test structures show that the uniform Qf effect can be understood in terms of a surface damage region (SDR) present near the interface in combination with asymmetry in the lifetime of holes and electrons in the SDR. The combination of low processing temperatures, thin layers and good passivation properties facilitate a technology for future low temperature solar cell applications.

  6. Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

    Science.gov (United States)

    Yueh, Simon H.; Chaubell, Mario J.

    2012-01-01

    Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed

  7. In situ observation of biotite (001) surface dissolution at pH 1 and 9.5 by advanced optical microscopy

    OpenAIRE

    Chiara Cappelli; Daniel Lamarca-Irisarri; Jordi Camas; F. Javier Huertas; van Driessche, Alexander E.S.

    2015-01-01

    Laser confocal differential interference contrast microscopy (LCM-DIM) allows for the study of the reactivity of surface minerals with slow dissolution rates (e.g., phyllosilicates). With this technique, it is possible to carry out in situ inspection of the reacting surface in a broad range of pH, ionic strength and temperature providing useful information to help unravel the dissolution mechanisms of phyllosilicates. In this work, LCM-DIM was used to study the mechanisms controlling the biot...

  8. Perturbation of xenobiotic metabolism in Dreissena polymorpha model exposed in situ to surface water (Lake Trasimene) purified with various disinfectants.

    Science.gov (United States)

    Sapone, Andrea; Canistro, Donatella; Vivarelli, Fabio; Paolini, Moreno

    2016-02-01

    Sanitation is of crucial importance for the microbiological safety of drinking water. However, chlorination of water rich in organic material produces disinfection by-products (DBPs), many of which have been reported to be mutagenic and/or carcinogenic compounds such as haloacetic acids and trihalomethanes. Epidemiological studies have suggested a link between drinking water consumption and cancer. We previously observed that Cyprinus carpio fish exposed to DBPs, may be subject to epigenetic effects such as those referable to the up-regulation of cytochrome P450 (CYP) superfamily (ex. co-mutagenesis/co-carcinogenesis and oxidative stress) that has been associated to non-genotoxic carcinogenesis. Our goal was to study the xenobiotic metabolism in mollusks exposed in situ to surface water of Lake Trasimene (Central Italy) treated with several disinfectants such as the traditional chlorine dioxide (ClO2), sodium hypochlorite (NaClO) or the relatively new one peracetic acid (PAA). The freshwater bivalves (Dreissena polymorpha) being selected as biomarker, have the unique ability to accumulate pollutants. Freshwater bivalves were maintained in surface water containing each disinfectant individually (1-2 mg/L). Following an exposure period up to 20 days during the fall period, microsomes were collected from the mussels, then tested for various monooxygenases. Strong CYP inductions were observed. These data indicate that drinking water disinfection generates harmful DBP mixtures capable of determining a marked perturbation of CYP-supported reactions. This phenomenon, being associated to an increased pro-carcinogen bioactivation and persistent oxidative stress, could provide an explanation for the observational studies connecting the regular consumption of drinking water to increased risk of various cancers in humans.

  9. In situ determination of multiple polycyclic aromatic hydrocarbons uptake by crop leaf surfaces using multi-way models.

    Science.gov (United States)

    Sun, Haifeng; Guo, Shuai; Zhu, Na; Sang, Nan; Chen, Zhang

    2016-11-01

    Polycyclic aromatic hydrocarbons (PAHs) in the atmosphere can partition into agricultural crops, which poses a potential risk to human health through the food chain. In this study, controlled chamber experiments were conducted to investigate the kinetic uptake of anthracene (Ant), phenanthrene (Phe), fluoranthene (Fla) and pyrene (Pyr), individually or as a mixture, by the leaf surfaces of living soybean and corn seedlings using the excitation-emission matrix (EEM) coupled with three-way parallel factor analysis (PARAFAC) and n-way partial least squares (n-PLS). The four selected PAHs achieved equilibrium between the air and the two living crop leaf surfaces over the 15-day monitoring period. Inter-species and inter-chemical variability existed in terms of the time required to achieve equilibrium, mass transfer coefficients (kAL) and the equilibrated adsorption capacity (EAC), which was mainly attributed to the different lg KOA values among the four PAHs and the variable leaf-wax content between the soybean and corn species. Compared with when the PAHs existed singly, the time required to achieve adsorption equilibrium was longer while the EAC was reduced for each of the four PAHs in a mixture, which was attributed to competitive adsorption among the coexisting components. These findings prove that the novel analytical method provides a novel platform for the in situ characterization of the environmental behaviors of multiple PAHs, with their spectra overlapping, between the air and plant skin. The coexistence of multiple PAHs in the air inhibits their individual uptake capacity by crop leaf skin, but increases the total adsorption of PAHs, potentially reducing crop security and increasing human health risk via the terrestrial food web. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Effective surface treatment for GaN metal-insulator-semiconductor high-electron-mobility transistors using HF plus N2 plasma prior to SiN passivation

    Science.gov (United States)

    Liu, Shih-Chien; Trinh, Hai-Dang; Dai, Gu-Ming; Huang, Chung-Kai; Dee, Chang-Fu; Yeop Majlis, Burhanuddin; Biswas, Dhrubes; Chang, Edward Yi

    2016-01-01

    An effective surface cleaning technique is demonstrated for the GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) passivation process. In this study, dilute HF solution and in situ N2 plasma treatments were adopted to remove the native oxide and recover the nitrogen-vacancy defects at the GaN surface before device passivation. To investigate the correlation between the properties of the SiN/GaN interface and the device performance, the GaN MIS-HEMTs were characterized using current-voltage (I-V) measurement, capacitance-voltage (C-V) measurement, and X-ray photoelectron spectroscopy (XPS) analysis. With the application of this surface treatment technique, the device exhibits improved I-V characteristics with low leakage current, low dynamic ON-resistance, and good C-V response with a steep slope. Overall, the results reveal that the oxide-related bonds and nitrogen-vacancy defects at the SiN/GaN interface are the root cause of the GaN MIS-HEMTs performance degradation.

  11. An investigation of current and future satellite and in-situ data for the remote sensing of the land surface energy balance

    Science.gov (United States)

    Diak, George R.

    1994-01-01

    This final report from the University of Wisconsin-Madison Cooperative Institute for Meteorological Satellite Studies (CIMSS) summarizes a research program designed to improve our knowledge of the water and energy balance of the land surface through the application of remote sensing and in-situ data sources. The remote sensing data source investigations to be detailed involve surface radiometric ('skin') temperatures and also high-spectral-resolution infrared radiance data from atmospheric sounding instruments projected to be available at the end of the decade, which have shown promising results for evaluating the land-surface water and energy budget. The in-situ data types to be discussed are measurements of the temporal changes of the height of the planetary boundary layer and measurements of air temperature within the planetary boundary layer. Physical models of the land surface, planetary boundary layer and free atmosphere have been used as important tools to interpret the in-situ and remote sensing signals of the surface energy balance. A prototype 'optimal' system for combining multiple data sources into a three-dimensional estimate of the surface energy balance was developed and first results from this system will be detailed. Potential new sources of data for this system and suggested continuation research will also be discussed.

  12. Passivation of c-Si surfaces by sub-nm amorphous silicon capped with silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Yimao, E-mail: yimao.wan@anu.edu.au; Yan, Di; Bullock, James; Zhang, Xinyu; Cuevas, Andres [Research School of Engineering, The Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

    2015-12-07

    A sub-nm hydrogenated amorphous silicon (a-Si:H) film capped with silicon nitride (SiN{sub x}) is shown to provide a high level passivation to crystalline silicon (c-Si) surfaces. When passivated by a 0.8 nm a-Si:H/75 nm SiN{sub x} stack, recombination current density J{sub 0} values of 9, 11, 47, and 87 fA/cm{sup 2} are obtained on 10 Ω·cm n-type, 0.8 Ω·cm p-type, 160 Ω/sq phosphorus-diffused, and 120 Ω/sq boron-diffused silicon surfaces, respectively. The J{sub 0} on n-type 10 Ω·cm wafers is further reduced to 2.5 ± 0.5 fA/cm{sup 2} when the a-Si:H film thickness exceeds 2.5 nm. The passivation by the sub-nm a-Si:H/SiN{sub x} stack is thermally stable at 400 °C in N{sub 2} for 60 min on all four c-Si surfaces. Capacitance–voltage measurements reveal a reduction in interface defect density and film charge density with an increase in a-Si:H thickness. The nearly transparent sub-nm a-Si:H/SiN{sub x} stack is thus demonstrated to be a promising surface passivation and antireflection coating suitable for all types of surfaces encountered in high efficiency c-Si solar cells.

  13. Application and comparison of band gap narrowing models for passivated phosphorus doped silicon surfaces

    Science.gov (United States)

    Kimmerle, Achim; Greulich, Johannes; Haug, Halvard; Wolf, Andreas

    2016-01-01

    In this work, the recently proposed band-gap narrowing model by Yan and Cuevas [J. Appl. Phys. 114, 044508 (2013)] is evaluated by simulations of the recombination pre-factor J0 of highly phosphorus doped, passivated crystalline silicon surfaces, which are particularly relevant for solar cell applications. The results were fitted to experimental J0 data measured on a large range of samples exhibiting different dopant profiles and passivation coatings, both for planar and textured surfaces. For each sample, the surface recombination velocity parameter Sp was extracted by fitting the simulation results to the experimental data. We show that the Yan and Cuevas' model developed for Fermi-Dirac statistics leads to a smooth and monotonically increasing curve for Sp as a function of the surface dopant concentration Nsurf, for both investigated passivation layers. We provide a parameterization for this relation and compare the findings with those obtained with the widely used model by Schenk [J. Appl. Phys. 84, 3684 (1998)]. On the other hand, we show that the apparent band gap narrowing of Yan and Cuevas developed for use with Boltzmann statistics cannot be used to describe the experimental data, requiring unphysical negative Sp values for high Nsurf.

  14. Surface Passivation of GaN Nanowires for Enhanced Photoelectrochemical Water-Splitting

    KAUST Repository

    Varadhan, Purushothaman

    2017-02-08

    Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of −31 mA/cm at −0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only <4 h of photoelectrochemical stability. These findings shed new light on the importance of surface passivation of nanostructured photoelectrodes for photoelectrochemical applications.

  15. Surface Passivation of GaN Nanowires for Enhanced Photoelectrochemical Water-Splitting.

    Science.gov (United States)

    Varadhan, Purushothaman; Fu, Hui-Chun; Priante, Davide; Retamal, Jose Ramon Duran; Zhao, Chao; Ebaid, Mohamed; Ng, Tien Khee; Ajia, Idirs; Mitra, Somak; Roqan, Iman S; Ooi, Boon S; He, Jr-Hau

    2017-03-08

    Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of -31 mA/cm(2) at -0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only surface passivation of nanostructured photoelectrodes for photoelectrochemical applications.

  16. Integer quantum Hall effect on a six-valley hydrogen-passivated silicon (111) surface.

    Science.gov (United States)

    Eng, K; McFarland, R N; Kane, B E

    2007-07-01

    We report magnetotransport studies of a two-dimensional electron system formed in an inversion layer at the interface between a hydrogen-passivated Si(111) surface and vacuum. Measurements in the integer quantum Hall regime demonstrate that the expected sixfold valley degeneracy for these surfaces is broken, resulting in an unequal occupation of the six valleys and anisotropy in the resistance. We hypothesize the misorientation of Si surface breaks the valley states into three unequally spaced pairs, but the observation of odd filling factors is difficult to reconcile with noninteracting electron theory.

  17. Passivation layer effect on surface integrity induced by Cu-CMP

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Wei-En [Center for Measurement Standards, Industrial Technology Research Institute, 195 Chung Hsing Rd., Sec.4 Chu Tung, Hsin Chu 310, Taiwan (China); Chen, Chao-Chang A., E-mail: artchen@mail.ntust.edu.tw [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec.4 Keelung Rd., Taipei 106, Taiwan (China); Lin, Yan-De [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec.4 Keelung Rd., Taipei 106, Taiwan (China); Chang, Yong-Qing [Center for Measurement Standards, Industrial Technology Research Institute, 195 Chung Hsing Rd., Sec.4 Chu Tung, Hsin Chu 310, Taiwan (China); Huang, Yao-Hong [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec.4 Keelung Rd., Taipei 106, Taiwan (China)

    2011-05-31

    To achieve efficient Cu-Chemical-Mechanical Polishing planarization at miniaturized device dimensions, there is a need for a better understanding of the surface integrity induced by the process. Surface quality and stresses are the two selected indices in this article to evaluate the Cu-CMP process induced surface integrity. The thickness of the passivation layer and the penetration depth of abrasives are considered as the main effects for the generations of surface qualities and residual stress. Experimental validation on copper films on silicon wafer was performed by CMP with different pads and slurries to generate varied residual stresses and surface qualities. Depth of scratches and surface roughness were measured by the atomic force microscope. The stress measurements of the thin films were performed by a Grazing Incident X-ray diffraction instrument with its principles based upon modified sin{sup 2}{Psi} method. Accordingly, the surface roughness and stress were related to the thickness of the passivation layer and the CMP process conditions. When the penetration depth is larger than the passivation layer thickness, the roughness values are mainly decided by the selection of pads and the resultant penetration depth. In addition, the residual stress profiles are dependent on the CMP process conditions which include the slurries and pad parameters. The stress profile obtained for the slurry SDK with soft pad Politex composed smallest maximum tensile stress below the surface and a steady transition of stress profile compared to the stress profile obtained at the initial condition. At the condition for the same slurry SDK, but with a hard pad of IC1000, the CMP process induced larger maximum stress and sharper profile transition.

  18. Scale-up considerations for surface collecting agent assisted in-situ burn crude oil spill response experiments in the Arctic: Laboratory to field-scale investigations.

    Science.gov (United States)

    Bullock, Robin J; Aggarwal, Srijan; Perkins, Robert A; Schnabel, William

    2017-04-01

    In the event of a marine oil spill in the Arctic, government agencies, industry, and the public have a stake in the successful implementation of oil spill response. Because large spills are rare events, oil spill response techniques are often evaluated with laboratory and meso-scale experiments. The experiments must yield scalable information sufficient to understand the operability and effectiveness of a response technique under actual field conditions. Since in-situ burning augmented with surface collecting agents ("herders") is one of the few viable response options in ice infested waters, a series of oil spill response experiments were conducted in Fairbanks, Alaska, in 2014 and 2015 to evaluate the use of herders to assist in-situ burning and the role of experimental scale. This study compares burn efficiency and herder application for three experimental designs for in-situ burning of Alaska North Slope crude oil in cold, fresh waters with ∼10% ice cover. The experiments were conducted in three project-specific constructed venues with varying scales (surface areas of approximately 0.09 square meters, 9 square meters and 8100 square meters). The results from the herder assisted in-situ burn experiments performed at these three different scales showed good experimental scale correlation and no negative impact due to the presence of ice cover on burn efficiency. Experimental conclusions are predominantly associated with application of the herder material and usability for a given experiment scale to make response decisions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Crystalline silicon surface passivation by thermal ALD deposited Al doped ZnO thin films

    Directory of Open Access Journals (Sweden)

    Jagannath Panigrahi

    2017-03-01

    Full Text Available The evidence of good quality silicon surface passivation using thermal ALD deposited Al doped zinc oxide (AZO thin films is demonstrated. AZO films are prepared by introducing aluminium precursor in between zinc and oxygen precursors during the deposition. The formation of AZO is confirmed by ellipsometry, XRD and Hall measurements. Effective minority carrier lifetime (τeff greater than 1.5ms at intermediate bulk injection levels is realized for symmetrically passivated p-type silicon surfaces under optimised annealing conditions of temperature and time in hydrogen ambient. The best results are realised at 450°C annealing for >15min. Such a layer may lead to implied open circuit voltage gain of 80mV.

  20. In situ calibration of a passive sampling device for selected illicit drugs and their metabolites in wastewater, and subsequent year-long assessment of community drug usage.

    Science.gov (United States)

    Harman, Christopher; Reid, Malcolm; Thomas, Kevin V

    2011-07-01

    Polar organic chemical integrative samplers (POCIS) were calibrated in situ for selected illicit drugs and their metabolites at a sewage treatment works. Eleven out of 13 target compounds were detected and eight of those exhibited linear uptake kinetics with sampling rates between 0.035 and 0.150 L d(-1). Subsequently POCIS were deployed for 2 week periods over the course of a whole year, in order to examine trends in drug usage. Amphetamine and methamphetamine showed several similar peaks in concentration during the course of the year as did cocaine and two of its metabolites. Low levels of ecstasy were observed, with a prominent peak in May and a steady increase toward the end of the year. The antihistamine Cetirizine showed a clear increase in use during the summer months as expected and back calculation of the yearly dosage from POCIS accumulations yielded very similar results to that registered in the Norwegian prescription database. Estimations of cocaine usage using the parent compound averaged between 0.31 and 2.8 g d(-1) per 1000 inhabitants. POCIS is a cost-effective technique for the long-term monitoring of drug usage of a defined population and may overcome the difficulties of representative sampling associated with autosampling equipment.

  1. Fabrication and surface passivation of porous 6H-SiC by atomic layer deposited films

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Petersen, Paul Michael

    2016-01-01

    photoluminescence was observed and the etching process was optimized in terms of etching time and thickness. Enormous enhancement as well as redshift and broadening of photoluminescence spectra were observed after the passivation by atomic layer deposited Al2O3 and TiO2 films. No obvious luminescence was observed...... above the 6H-SiC crystal band gap, which suggests that the strong photoluminescence is ascribed to surface state produced during the anodic etching....

  2. Multi-channel analysis of passive surface waves based on cross-correlations

    Science.gov (United States)

    Cheng, F.; Xia, J.; Xu, Z.; Hu, Y.

    2015-12-01

    Traditional active seismic survey can no longer be properly applied in highly populated urban areas due to restrictions in modern civilian life styles. Passive seismic methods, however, have gained much more attention from the engineering geophysics community because of their environmental friendly and deeper investigation depth. Due to extracting signal from noise has never been as comfortable as that in active seismic survey, how to make it more efficiently and accurately has been emphasized. We propose a multi-channel analysis of passive surface waves (MAPW) based on long noise sequences cross-correlations to meet the demand for increasing investigation depth by acquiring surface-wave data at a relative low-frequency range (1 Hz ≤ f ≤ 10 Hz) in urban areas. We utilize seismic interferometry to produce common virtual source gathers from one-hour-long noise records and do dispersion measurements by using the classic passive multi-channel analysis of surface waves (PMASW). We used synthetic tests to demonstrate the advantages of MAPW for various noise distributions. Results show that our method has the superiority of maximizing the analysis accuracy. Finally, we used two field data applications to demonstrate the advantages of our MAPW over the classic PMASW on isolating azimuth of the predominant noise sources and the effectivity of combined survey of active multi-channel analysis of surface waves (MASW) and MAPW. We suggest, for the field operation using MAPW, that a parallel receiver line which is close to a main road or river, if any, with one or two hours noise observation will be an effective means for an unbiased dispersion image. Keywords: passive seismic method, MAPW, MASW, cross-correlation, directional noise source, spatial-aliasing effects, inversion

  3. Characterization of a complex near-surface structure using well logging and passive seismic measurements

    Science.gov (United States)

    Benjumea, Beatriz; Macau, Albert; Gabàs, Anna; Figueras, Sara

    2016-04-01

    We combine geophysical well logging and passive seismic measurements to characterize the near-surface geology of an area located in Hontomin, Burgos (Spain). This area has some near-surface challenges for a geophysical study. The irregular topography is characterized by limestone outcrops and unconsolidated sediments areas. Additionally, the near-surface geology includes an upper layer of pure limestones overlying marly limestones and marls (Upper Cretaceous). These materials lie on top of Low Cretaceous siliciclastic sediments (sandstones, clays, gravels). In any case, a layer with reduced velocity is expected. The geophysical data sets used in this study include sonic and gamma-ray logs at two boreholes and passive seismic measurements: three arrays and 224 seismic stations for applying the horizontal-to-vertical amplitude spectra ratio method (H/V). Well-logging data define two significant changes in the P-wave-velocity log within the Upper Cretaceous layer and one more at the Upper to Lower Cretaceous contact. This technique has also been used for refining the geological interpretation. The passive seismic measurements provide a map of sediment thickness with a maximum of around 40 m and shear-wave velocity profiles from the array technique. A comparison between seismic velocity coming from well logging and array measurements defines the resolution limits of the passive seismic techniques and helps it to be interpreted. This study shows how these low-cost techniques can provide useful information about near-surface complexity that could be used for designing a geophysical field survey or for seismic processing steps such as statics or imaging.

  4. High-performance silicon nanowire array photoelectrochemical solar cells through surface passivation and modification.

    Science.gov (United States)

    Wang, Xin; Peng, Kui-Qing; Pan, Xiao-Jun; Chen, Xue; Yang, Yang; Li, Li; Meng, Xiang-Min; Zhang, Wen-Jun; Lee, Shuit-Tong

    2011-10-10

    Nanowire solar cells: Pt nanoparticle (PtNP) decorated C/Si core/shell nanowire photoelectrochemical solar cells show high conversion efficiency of 10.86 % and excellent stability in aggressive electrolytes under 1-sun AM 1.5 G illumination. Superior device performance is achieved by improved surface passivation of the nanowires by carbon coating and enhanced interfacial charge transfer by PtNPs.

  5. Impacts of Aerosol, Surface and Meteorological Conditions on Polar Cloud Properties: Use of In-Situ Cloud Probe Data

    Science.gov (United States)

    McFarquhar, Greg; Wu, Wei; Maahn, Maximilian

    2017-04-01

    Over the Southern Oceans, models from the Coupled Model Intercomparison Project 5 (CMIP5) almost universally underestimate sunlight reflected by near surface cloud in the Austral summer compared to Clouds and the Earth's Radiant Energy System (CERES) data. These and other biases in radiative fluxes over the Arctic are believed to be associated with the poorly modeled properties of low-level clouds that are frequently composed of supercooled water. Because changes in cloud macrophysical (heights, coverage) and microphysical (sizes, shapes and phases of particles) can alter the radiative impact of clouds, it is important to understand the processes that control cloud properties. In this presentation, in-situ microphysical observations obtained in prior arctic field campaigns (e.g., the Indirect and Semi-Direct Aerosol Campaign ISDAC, the Mixed-Phase Arctic Cloud Experiment M-PACE, and the Atmospheric Radiation Measurement Carbon Measurements Program-V ACME-V) are discussed. Strategies for comparing data collected in campaigns with different probes and processed with varying algorithms are introduced, along with procedures for using cloud probe data to refine assumptions about cloud properties in model schemes (e.g., size distributions, mass-dimension, and velocity-dimension relations) that affect rates at which mass and number are transferred between hydrometeor categories and hence estimates of latent and radiative heating, which feeds back on dynamics and hence cloud properties. Such observations from past arctic field experiments have enhanced our understanding of aerosol-cloud interactions acting in single-layer mixed phase clouds that are ubiquitous in the Arctic. But, it is still unknown what controls the amount of supercooled water in polar clouds (especially in frequently occurring complex multi-layer clouds), how probability distributions of cloud properties vary with aerosol loading and composition in different surface and meteorological conditions, and how

  6. Si surface passivation by Al2O3 thin films deposited using a low thermal budget atomic layer deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Seguini, G.; Cianci, E.; Wiemer, C.; Perego, M. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza MB (Italy); Saynova, D.; Van Roosmalen, J.A.M. [ECN Solar Energy, Westerduinweg 3, NL-1755 ZG Petten (Netherlands)

    2013-04-05

    High-quality surface passivation of crystalline Si is achieved using 10 nm thick Al2O3 films fabricated by thermal atomic layer deposition at 100C. After a 5 min post deposition annealing at 200C, the effective carrier lifetime is 1 ms, indicating a functional level of surface passivation. The interplay between the chemical and the field effect passivation is investigated monitoring the density of interface traps and the amount of fixed charges with conductance-voltage and capacitance-voltage techniques. The physical mechanisms underlying the surface passivation are described. The combination of low processing temperatures, thin layers, and good passivation properties facilitate a technology for low-temperature solar cells.

  7. Active Sampling Device for Determining Pollutants in Surface and Pore Water - the In Situ Sampler for Biphasic Water Monitoring

    Science.gov (United States)

    Supowit, Samuel D.; Roll, Isaac B.; Dang, Viet D.; Kroll, Kevin J.; Denslow, Nancy D.; Halden, Rolf U.

    2016-02-01

    We designed and evaluated an active sampling device, using as analytical targets a family of pesticides purported to contribute to honeybee colony collapse disorder. Simultaneous sampling of bulk water and pore water was accomplished using a low-flow, multi-channel pump to deliver water to an array of solid-phase extraction cartridges. Analytes were separated using either liquid or gas chromatography, and analysis was performed using tandem mass spectrometry (MS/MS). Achieved recoveries of fipronil and degradates in water spiked to nominal concentrations of 0.1, 1, and 10 ng/L ranged from 77 ± 12 to 110 ± 18%. Method detection limits (MDLs) were as low as 0.040-0.8 ng/L. Extraction and quantitation of total fiproles at a wastewater-receiving wetland yielded concentrations in surface water and pore water ranging from 9.9 ± 4.6 to 18.1 ± 4.6 ng/L and 9.1 ± 3.0 to 12.6 ± 2.1 ng/L, respectively. Detected concentrations were statistically indistinguishable from those determined by conventional, more laborious techniques (p > 0.2 for the three most abundant fiproles). Aside from offering time-averaged sampling capabilities for two phases simultaneously with picogram-per-liter MDLs, the novel methodology eliminates the need for water and sediment transport via in situ solid phase extraction.

  8. Chemical and toxicologic assessment of organic contaminants in surface water using passive samplers

    Science.gov (United States)

    Alvarez, D.A.; Cranor, W.L.; Perkins, S.D.; Clark, R.C.; Smith, S.B.

    2008-01-01

    Passive sampling methodologies were used to conduct a chemical and toxicologic assessment of organic contaminants in the surface waters of three geographically distinct agricultural watersheds. A selection of current-use agrochemicals and persistent organic pollutants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides, were targeted using the polar organic chemical integrative sampler (POCIS) and the semipermeable membrane device passive samplers. In addition to the chemical analysis, the Microtox assay for acute toxicity and the yeast estrogen screen (YES) were conducted as potential assessment tools in combination with the passive samplers. During the spring of 2004, the passive samplers were deployed for 29 to 65 d at Leary Weber Ditch, IN; Morgan Creek, MD; and DR2 Drain, WA. Chemical analysis of the sampler extracts identified the agrochemicals predominantly used in those areas, including atrazine, simazine, acetochlor, and metolachlor. Other chemicals identified included deethylatrazine and deisopropylatrazine, trifluralin, fluoranthene, pyrene, cis- and trans-nonachlor, and pentachloroanisole. Screening using Microtox resulted in no acutely toxic samples. POCIS samples screened by the YES assay failed to elicit a positive estrogenic response. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  9. Influence of deposition temperature of thermal ALD deposited Al2O3 films on silicon surface passivation

    Science.gov (United States)

    Batra, Neha; Gope, Jhuma; Vandana, Panigrahi, Jagannath; Singh, Rajbir; Singh, P. K.

    2015-06-01

    The effect of deposition temperature (Tdep) and subsequent annealing time (tanl) of atomic layer deposited aluminum oxide (Al2O3) films on silicon surface passivation (in terms of surface recombination velocity, SRV) is investigated. The pristine samples (as-deposited) show presence of positive fixed charges, QF. The interface defect density (Dit) decreases with increase in Tdep which further decreases with tanl up to 100s. An effective surface passivation (SRV<8 cm/s) is realized for Tdep ≥ 200 °C. The present investigation suggests that low thermal budget processing provides the same quality of passivation as realized by high thermal budget process (tanl between 10 to 30 min).

  10. In-situ reflection-XANES study of ZDDP and MoDTC lubricant films formed on steel and diamond like carbon (DLC) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Morina, Ardian, E-mail: A.Morina@leeds.ac.uk [Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Zhao, Hongyuan [Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Mosselmans, J. Fred W. [Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

    2014-04-01

    Highlights: • S, P, Zn and Mo species formed in lubricant films can be characterised in-situ and in-lubro by using the reflection mode XAS technique. • Heating the lubricated steel and DLC samples affects the chemical reaction between the adsorbed species and the surface, resulting in different chemical composition of the ZDDP + MoDTC thermal film formed on steel or DLC. • There is a greater effect of temperature on S species than P species formed on ZDDP thermal films. - Abstract: Chemical characterisation of boundary lubricated interfaces is essential for developing mechanistic models that describe lubricant additive interactions with the surface and their effect on tribological performance. In this study the potential for using the synchrotron-based reflection mode X-ray absorption spectroscopy (XAS) technique for in-situ chemical characterisation of lubricant films has been studied. Thermal films formed from zinc dialkyl dithio phosphate (ZDDP) and molybdenum dialkyl dithio carbamate (MoDTC) lubricant additives have been formed and analysed in-situ using the X-ray absorption near edge structure (XANES) spectroscopy technique. The surface sensitivity of this approach was improved by doing the analysis in reflection mode, enabling analysis of only top layer (up to around 10 nm) of the solid surface. In addition, in-lubro analysis of pre-formed tribofilms from the same additives was done using non-vacuum conditions. The results are discussed in conjunction with XANES and X-ray photoelectron spectroscopy (XPS) analysis of similar additives published in the literature. The results obtained are consistent with the existing ZDDP and MoDTC literature and provide some new insight into intermediate species not reported before. The advantages and disadvantages of the developed XANES methodology for in-situ surface chemical analysis of lubricated conditions are discussed.

  11. An autonomous multisensor in situ metrology system for enabling high dynamic range measurement of 3D surfaces on precision machine tools

    Science.gov (United States)

    Liu, Samuel M. Y.; Cheung, Benny C. F.; Whitehouse, David; Cheng, Ching-Hsiang

    2016-11-01

    An in situ measurement is of prime importance when trying to maintain the position of the workpiece for further compensation processes in order to improve the accuracy and efficiency of the precision machining of three dimensional (3D) surfaces. However, the coordinates of most of the machine tools with closed machine interfaces and control system are not accessible for users, which make it difficult to use the motion axes of the machine tool for in situ measurements. This paper presents an autonomous multisensor in situ metrology system for enabling high dynamic range measurement of 3D surfaces on precision machine tools. It makes use of a designed tool path and an additional motion sensor to assist the registration of time-space data for the position estimation of a 2D laser scanner which measures the surface with a high lateral resolution and large area without the need to interface with the machine tool system. A prototype system was built and integrated into an ultra-precision polishing machine. Experimental results show that it measures the 3D surfaces with high resolution, high repeatability, and large measurement range. The system not only improves the efficiency and accuracy of the precision machining process but also extends the capability of machine tools.

  12. The binding of phosphonic acids at aluminium oxide surfaces and correlation with passivation of aluminium flake.

    Science.gov (United States)

    Cooper, Rachel J; Camp, Philip J; Henderson, David K; Lovatt, Paul A; Nation, David A; Richards, Stuart; Tasker, Peter A

    2007-04-07

    Measurements of adsorption isotherms of a series of thirteen mono- and di-phosphonic acids have shown that these bind strongly to the surface of high surface area aluminium trihydroxide. The incorporation of such phosphonates into a suspension of aluminium flake in an aqueous medium, modelling the continuous phase of a water-based paint, greatly suppresses the evolution of hydrogen. Whilst strong binding of the phosphonate to aluminium oxides is an essential criterion for good passivation, other factors such as the hydrophobicity of the ligand are also important in suppressing hydrogen-evolution.

  13. Bridging the pressure gap: In situ atomic-level investigations of model platinum catalyst surfaces under reaction conditions by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, B.J.

    1994-05-01

    Results of this thesis show that STM measurements can provide information about the surfaces and their adsorbates. Stability of Pt(110) under high pressures of H2, O2, and CO was studied (Chap. 4). In situ UHV and high vacuum experiments were carried out for sulfur on Pt(111) (Chap.5). STM studies of CO/S/Pt(111) in high CO pressures showed that the Pt substrate undergoes a stacking-fault-domain reconstruction involving periodic transitions from fcc to hcp stacking of top-layer atoms (Chap.6). In Chap.7, the stability of propylene on Pt(111) and the decomposition products were studied in situ with the HPSTM. Finally, in Chap.8, results are presented which show how the Pt tip of the HPSTM was used to locally rehydrogenate and oxidize carbonaceous clusters deposited on the Pt(111) surface; the Pt tip acted as a catalyst after activation by short voltage pulses.

  14. In situ Raman spectroscopic analysis of surface oxide films on Ni-base alloy/low alloy steel dissimilar metal weld interfaces in high-temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jongjin; Choi, Kyung Joon [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Bahn, Chi Bum [School of Mechanical Engineering, Pusan National University 2, 63-gil, Geumjeong-Gu, Pusan 609-735 (Korea, Republic of); Kim, Ji Hyun, E-mail: kimjh@unist.ac.kr [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of)

    2014-06-01

    In situ Raman spectroscopy has been applied to analyze the surface oxide films formed on dissimilar metal weld (DMW) interfaces of nickel-base alloy/low alloy steel under hydrogenated high-temperature water condition. For the analysis of the oxide films under high temperature/pressure aqueous conditions, an in situ Raman spectroscopy system was developed by constructing a hydrothermal cell where the entire optics including the excitation laser and the Raman light collection system were located at the nearest position to the specimen by means of immersion optics. In situ Raman spectra of the DMW interfaces were collected in hydrogenated water condition at different temperatures up to 300 °C. The measured in situ Raman spectra showed peaks of Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and Fe{sub 3}O{sub 4} at the DMW interface. It is considered that differences in the oxide chemistry originated from the chemical element distribution inside of the DMW interface region.

  15. An In-Situ Root-Imaging System in the Context of Surface Detection of CO2

    Science.gov (United States)

    Apple, M. E.; Prince, J. B.; Bradley, A. R.; Zhou, X.; Lakkaraju, V. R.; Male, E. J.; Pickles, W.; Thordsen, J. J.; Dobeck, L.; Cunningham, A.; Spangler, L.

    2009-12-01

    Carbon sequestration is a valuable method of spatially confining CO2 belowground. The Zero Emissions Research Technology, (ZERT), site is an experimental facility in a former agricultural field on the Montana State University campus in Bozeman, Montana, where CO2 was experimentally released at a rate of 200kg/day in 2009 into a 100 meter underground injection well running parallel to the ground surface. This injection well, or pipe, has deliberate leaks at intervals, and CO2 travels from these leaks upward to the surface of the ground. The ZERT site is a model system designed with the purpose of testing methods of surface detection of CO2. One important aspect of surface detection is the determination of the effects of CO2 on the above and belowground portions of plants growing above sequestration fields. At ZERT, these plants consist of a pre-existing mixture of herbaceous species present at the agricultural field. Species growing at the ZERT site include several grasses, Dactylis glomerata (Orchard Grass), Poa pratensis (Kentucky Bluegrass), and Bromus japonicus (Japanese Brome); the nitrogen-fixing legumes Medicago sativa, (Alfalfa), and Lotus corniculatus, (Birdsfoot trefoil); and an abundance of Taraxacum officinale, (Dandelion). Although the aboveground parts of the plants at high CO2 are stressed, as indicated by changes in hyperspectral plant signatures, leaf fluorescence and leaf chlorophyll content, we are interested in determining whether the roots are also stressed. To do so, we are combining measurements of soil conductivity and soil moisture with root imaging. We are using an in-situ root-imaging system manufactured by CID, Inc. (Camas, WA), along with image analysis software (Image-J) to analyze morphometric parameters in the images and to determine what effects, if any, the presence of leaking and subsequently upwelling CO2 has on the phenology of root growth, growth and turnover of individual fine and coarse roots, branching patterns, and root

  16. Breakdown study based on direct in situ observation of inner surfaces of an rf accelerating cavity during a high-gradient test

    Science.gov (United States)

    Abe, Tetsuo; Kageyama, Tatsuya; Sakai, Hiroshi; Takeuchi, Yasunao; Yoshino, Kazuo

    2016-10-01

    We have developed normal-conducting accelerating single-cell cavities with a complete higher-order-mode (HOM) heavily damped structure, into which we feed a 508.9-MHz continuous wave. During a high-gradient test of the second production version of the cavity, we performed a breakdown study based on direct in situ observation of the inner surfaces of the cavity. This paper presents our experimental findings obtained from this observation.

  17. In Situ Structural Studies of the Underpotential Deposition of Copper onto an Iodine Covered Platinum Surface Using X-Ray Standing Waves

    Science.gov (United States)

    1991-01-01

    ABSTRAc C We present initial results of an in situ structural investigation of the underpotential deposition of copper on an iodine covered platinum...compare the result of surface coverage isotherms derived from both electrochemical and x-ray measurements. 1. INTRODUCIION The underpotential deposition ...the underpotential deposition of copper on an iodine covered platinum/carbon layered synthetic microstructure. 2 THEORETICAL BACKGROUND X-ray standing

  18. Behind the Nature of Titanium Oxide Excellent Surface Passivation and Carrier Selectivity of c-Si

    DEFF Research Database (Denmark)

    Plakhotnyuk, Maksym; Crovetto, Andrea; Hansen, Ole

    We present an expanded study of the passivation properties of titanium dioxide (TiO2) on p-type crystalline silicon (c-Si). We report a low surface recombination velocity (16 cm/s) for TiO2 passivation layers with a thin tunnelling oxide interlayer (SiO2 or Al2O3) on p-type crystalline silicon (c......-Si). The TiO2 films were deposited by thermal atomic layer deposition (ALD) at temperatures in the range of 80-300  ̊C using titanium tetrachloride (TiCl4) as Ti precursor and water as the oxidant. The influence of TiO2 thickness (5, 10, 20 nm), presence of additional tunneling interlayer (SiO2 or Al2O3...

  19. Metastability of a-SiOx:H thin films for c-Si surface passivation

    Science.gov (United States)

    Serenelli, L.; Martini, L.; Imbimbo, L.; Asquini, R.; Menchini, F.; Izzi, M.; Tucci, M.

    2017-01-01

    The adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Sisbnd H and Sisbnd O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiOx:H/c-Si/a-SiOx:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, was furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after a-SiOx:H coating by PECVD and after a thermal annealing treatment at 300 °C for 30 min, having selected these conditions on the basis of the study of the effect due to different temperatures and durations. We correlated the lifetime evolution and the metastability effect of thermal annealing to the a-SiOx:H/c-Si interface considering the evolution

  20. Facile in Situ Synthesis of Silver Nanoparticles on the Surface of Metal-Organic Framework for Ultrasensitive Surface-Enhanced Raman Scattering Detection of Dopamine.

    Science.gov (United States)

    Jiang, Zhongwei; Gao, Pengfei; Yang, Lin; Huang, Chengzhi; Li, Yuanfang

    2015-12-15

    Surface-enhanced Raman scattering (SERS) signals are intensively dominated by the Raman hot spots and distance between analyte molecules and metallic nanostructures. Herein, an efficient SERS substrate was developed by in situ synthesis of silver nanoparticles (AgNPs) on the surface of MIL-101 (Fe), a typical metal-organic framework (MOF). The as-prepared SERS substrate combines the numerous Raman hot spots between the high-density Ag NPs and the excellent adsorption performance of MOFs, making it an excellent SERS substrate for highly sensitive SERS detection by effectively concentrating analytes in close proximity to the Raman hot spots domains between the adjacent AgNPs. The resulting hybrid material was used for ultrasensitive SERS detection of dopamine based on the peroxidase-like activity of MIL-101 (Fe) by utilizing the enzyme-linked immunosorbent assay (ELISA) colorimetric substrate, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) as a SERS marker. This new developed method showed good linearity in the range from 1.054 pM to 210.8 nM for dopamine with the correlation coefficient of 0.992, detection limit of approximately 0.32 pM [signal-to-noise ratio (S/N) = 3], and acceptable recoveries ranging from 99.8% to 108.0% in human urine. These results predict that the proposed SERS system may open up a new opportunity for chemical and biological assay applications.

  1. Analysis of Wetting Characteristics on Microstructured Hydrophobic Surfaces for the Passive Containment Cooling System

    Directory of Open Access Journals (Sweden)

    Wei Zhao

    2015-01-01

    Full Text Available As the heat transfer surface in the passive containment cooling system, the anticorrosion coating (AC of steel containment vessel (CV must meet the requirements on heat transfer performance. One of the wall surface ACs with simple structure, high mechanical strength, and well hydrophobic characteristics, which is conductive to form dropwise condensation, is significant for the heat removal of the CV. In this paper, the grooved structures on silicon wafers by lithographic methods are systematically prepared to investigate the effects of microstructures on the hydrophobic property of the surfaces. The results show that the hydrophobicity is dramatically improved in comparison with the conventional Wenzel and Cassie-Baxter model. In addition, the experimental results are successfully explained by the interface state effect. As a consequence, it is indicated that favorable hydrophobicity can be obtained even if the surface is with lower roughness and without any chemical modifications, which provides feasible solutions for improving the heat transfer performance of CV.

  2. Plasma synthesis and liquid-phase surface passivation of brightly luminescent Si nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Mangolini, L. [Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, MN 55455 (United States); Jurbergs, D. [InnovaLight, Inc., 3303 Octavius Dr., Suite 104, Santa Clara, CA 95054 (United States); Rogojina, E. [InnovaLight, Inc., 3303 Octavius Dr., Suite 104, Santa Clara, CA 95054 (United States); Kortshagen, U. [Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, MN 55455 (United States)]. E-mail: uk@me.umn.edu

    2006-12-15

    While silicon's optical properties are improved at the nanoscale, they also become highly sensitive to the properties of the surfaces and interfaces of silicon nanostructures. For instance, while reported quantum yields for photoluminescence of silicon quantum dots covered by a native oxide are often in the few percent range, quantum yields as high as 30% have been found in quantum dots whose surfaces were passivated by covalently bonded organic molecules. In this paper, we describe an approach that is based on the gas phase synthesis of silicon quantum dots in a nonthermal plasma, and the subsequent organic surface passivation in the liquid phase. Nanocrystals are formed within a few milliseconds with a high mass yield in a nonthermal plasma. Various organic ligands such as octadecene, dodecence, and styrene are grafted onto the nanocrystal surfaces in a reaction known as hydrosilylation. Materials are characterized through transmission electron microscopy, atomic force microscopy, and fluorescence measurements. The particle size distributions are found to be relatively monodisperse and are well controllable through the plasma process parameters. Photoluminescence quantum yields as high as 60-70% have been achieved for particles luminescing in the red range of the visible spectrum.

  3. Surface passivation effects on the electronic and optical properties of 3C-SiC nanocrystals

    Science.gov (United States)

    Javan, Masoud Bezi

    2015-01-01

    Using time-dependent density functional theory the optical absorption spectrum of SiC nanocrystals was studied with changes in their surface structures as they are passivated with some functional groups such as amine (-NH2), amide (-CONH2), hydroxyl (-OH), carboxylic acid (-CO2H) and thiol (-SH) groups. The variations of some quantities such as formation energy, optical gap, single particle energy gap and lowest exciton binding energy of SiC nanocrystals are discussed with changes in their surface structure. Results indicate that in all cases the silicon dangling bonds on the surface of SiC nanocrystals are favorable for constructing stable structures with attached functional groups as in some cases their stability is more than pure hydrogenated SiC nanocrystal as an ideal structure. Also the functional groups attached to the surface of SiC nanocrystals change the optical properties of the SiC nanocrystals as the changes are remarkable for amide and thiol passivated nanocrystals.

  4. Surface passivation effects on the electronic and optical properties of 3C-SiC nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Javan, Masoud Bezi, E-mail: javan.masood@gmail.com

    2015-01-01

    Using time-dependent density functional theory the optical absorption spectrum of SiC nanocrystals was studied with changes in their surface structures as they are passivated with some functional groups such as amine (–NH{sub 2}), amide (–CONH{sub 2}), hydroxyl (–OH), carboxylic acid (–CO{sub 2}H) and thiol (–SH) groups. The variations of some quantities such as formation energy, optical gap, single particle energy gap and lowest exciton binding energy of SiC nanocrystals are discussed with changes in their surface structure. Results indicate that in all cases the silicon dangling bonds on the surface of SiC nanocrystals are favorable for constructing stable structures with attached functional groups as in some cases their stability is more than pure hydrogenated SiC nanocrystal as an ideal structure. Also the functional groups attached to the surface of SiC nanocrystals change the optical properties of the SiC nanocrystals as the changes are remarkable for amide and thiol passivated nanocrystals.

  5. Tuning luminescent properties of CdSe nanoclusters by phosphine surface passivation

    Science.gov (United States)

    Lysova, Iryna; Anton, Halina; Dmitruk, Igor; Mely, Yves

    2016-12-01

    Appropriate surface ligands are required for tuning the physicochemical and photophysical properties of nanoclusters (NCs). These surface ligands are especially critical for passivating the small (CdSe)33,34 NCs where the majority of atoms are at the NC surface. In this study, triphenylphosphine (TPP), trioctylphosphine (TOP) and tris(pentafluorophenyl)phosphine (TPFP) have been tested as capping agents for alkylamine-coated CdSe NCs. TPP and TOP compounds are found to increase the quantum yield of photoluminescence (PL) from 0.15% to 0.6% and 0.53%, respectively, and to preserve this increased PL with time, probably by preventing charge leakage as a result of their binding to Se atoms. Since no dramatic change in the shape of NCs’ PL spectrum occurs after surface treatment, both the exciton band and the low-energy broad band in magic NCs are thought to describe the intrinsic luminescence properties of the NCs. As a result, the PL increase due to Se passivation is thought to be mainly caused by a decrease in the efficiency of the NC nonradiative pathways.

  6. Mapping surface soil moisture using an aircraft-based passive microwave instrument: algorithm and example

    Science.gov (United States)

    Jackson, T. J.; Le Vine, David E.

    1996-10-01

    Microwave remote sensing at L-band (21 cm wavelength) can provide a direct measurement of the surface soil moisture for a range of cover conditions and within reasonable error bounds. Surface soil moisture observations are rare and, therefore, the use of these data in hydrology and other disciplines has not been fully explored or developed. Without satellite-based observing systems, the only way to collect these data in large-scale studies is with an aircraft platform. Recently, aircraft systems such as the push broom microwave radiometer (PBMR) and the electronically scanned thinned array radiometer (ESTAR) have been developed to facilitate such investigations. In addition, field experiments have attempted to collect the passive microwave data as part of an integrated set of hydrologic data. One of the most ambitious of these investigations was the Washita'92 experiment. Preliminary analysis of these data has shown that the microwave observations are indicative of deterministic spatial and temporal variations in the surface soil moisture. Users of these data should be aware of a number of issues related to using aircraft-based systems and practical approaches to applying soil moisture estimation algorithms to large data sets. This paper outlines the process of mapping surface soil moisture from an aircraft-based passive microwave radiometer system for the Washita'92 experiment.

  7. Morphotectonic evolution of passive margins undergoing active surface processes: large-scale experiments using numerical models.

    Science.gov (United States)

    Beucher, Romain; Huismans, Ritske S.

    2016-04-01

    Extension of the continental lithosphere can lead to the formation of a wide range of rifted margins styles with contrasting tectonic and geomorphological characteristics. It is now understood that many of these characteristics depend on the manner extension is distributed depending on (among others factors) rheology, structural inheritance, thermal structure and surface processes. The relative importance and the possible interactions of these controlling factors is still largely unknown. Here we investigate the feedbacks between tectonics and the transfers of material at the surface resulting from erosion, transport, and sedimentation. We use large-scale (1200 x 600 km) and high-resolution (~1km) numerical experiments coupling a 2D upper-mantle-scale thermo-mechanical model with a plan-form 2D surface processes model (SPM). We test the sensitivity of the coupled models to varying crust-lithosphere rheology and erosional efficiency ranging from no-erosion to very efficient erosion. We discuss how fast, when and how the topography of the continents evolves and how it can be compared to actual passive margins escarpment morphologies. We show that although tectonics is the main factor controlling the rift geometry, transfers of masses at the surface affect the timing of faulting and the initiation of sea-floor spreading. We discuss how such models may help to understand the evolution of high-elevated passive margins around the world.

  8. Tropospheric CH4 signals as observed by NDACC FTIR at globally distributed sites and comparison to GAW surface in situ measurements

    Directory of Open Access Journals (Sweden)

    E. Sepúlveda

    2014-07-01

    Full Text Available We present lower/middle tropospheric column-averaged CH4 mole fraction time series measured by nine globally distributed ground-based FTIR (Fourier transform infrared remote sensing experiments of the Network for the Detection of Atmospheric Composition Change (NDACC. We show that these data are well representative of the tropospheric regional-scale CH4 signal, largely independent of the local surface small-scale signals, and only weakly dependent on upper tropospheric/lower stratospheric (UTLS CH4 variations. In order to achieve the weak dependency on the UTLS, we use an a posteriori correction method. We estimate a typical precision for daily mean values of about 0.5% and a systematic error of about 2.5%. The theoretical assessments are complemented by an extensive empirical study. For this purpose, we use surface in situ CH4 measurements made within the Global Atmosphere Watch (GAW network and compare them to the remote sensing data. We briefly discuss different filter methods for removing the local small-scale signals from the surface in situ data sets in order to obtain the in situ regional-scale signals. We find good agreement between the filtered in situ and the remote sensing data. The agreement is consistent for a variety of timescales that are interesting for CH4 source/sink research: day-to-day, monthly, and inter-annual. The comparison study confirms our theoretical estimations and proves that the NDACC FTIR measurements can provide valuable data for investigating the cycle of CH4.

  9. Improving the performance of amorphous and crystalline silicon heterojunction solar cells by monitoring surface passivation

    Energy Technology Data Exchange (ETDEWEB)

    Schuettauf, J.W.A.; Van der Werf, C.H.M.; Kielen, I.M.; Van Sark, W.G.J.H.M.; Rath, J.K.; Schropp, R.E.I. [Utrecht University, Debye Institute for Nanomaterials Science, Nanophotonics, Physics of Devices, Princetonplein 5, 3584 CC Utrecht (Netherlands)

    2012-09-15

    The influence of thermal annealing on the crystalline silicon surface passivating properties of selected amorphous silicon containing layer stacks (including intrinsic and doped films), as well as the correlation with silicon heterojunction solar cell performance has been investigated. All samples have been isochronally annealed for 1 h in an N{sub 2} ambient at temperatures between 150C and 300C in incremental steps of 15C. For intrinsic films and intrinsic/n-type stacks, an improvement in passivation quality is observed up to 255C and 270C, respectively, and a deterioration at higher temperatures. For intrinsic/n-type a-Si:H layer stacks, a maximum minority carrier lifetime of 13.3 ms at an injection level of 10{sup 15} cm{sup -3} has been measured. In contrast, for intrinsic/p-type a-Si:H layer stacks, a deterioration in passivation is observed upon annealing over the whole temperature range. Comparing the lifetime values and trends for the different layer stacks to the performance of the corresponding cells, it is inferred that the intrinsic/p-layer stack is limiting device performance. Furthermore, thermal annealing of p-type layers should be avoided entirely. We therefore propose an adapted processing sequence, leading to a substantial improvement in efficiency to 16.7%, well above the efficiency of 15.8% obtained with the 'standard' processing sequence.

  10. Passivation of silicon surfaces by heat treatment in liquid water at 110 °C

    Science.gov (United States)

    Nakamura, Tomohiko; Sameshima, Toshiyuki; Hasumi, Masahiko; Mizuno, Tomohisa

    2015-10-01

    We report the effective passivation of silicon surfaces by heating single-crystalline silicon substrates in liquid water at 110 °C for 1 h. High photo-induced effective minority carrier lifetimes τeff were obtained ranging from 8.3 × 10-4 to 3.1 × 10-3 s and from 1.2 × 10-4 to 6.0 × 10-4 s for the n- and p-type samples, respectively, under 635 nm light illumination, while the τeff values of the initial bare samples were lower than 1.2 × 10-5 s. The heat treatment in liquid water at 110 °C for 1 h resulted in low surface recombination velocities ranging from 7 to 34 cm/s and from 49 to 250 cm/s for the n- and p-type samples, respectively. The photo-conductivity of the n-type sample was increased from 3.8 × 10-3 (initial) to 1.4 × 10-1 S/cm by the present heat treatment under air-mass (AM) 1.5 light illumination at 100 mW/cm2. The thickness of the passivation layer was estimated to be only approximately 0.7 nm. Metal-insulator-semiconductor-type solar cells were demonstrated with Al and Au metal formation on the passivated surface. Rectified current voltage and solar cell characteristics were observed. The open circuit voltages were obtained to be 0.52 and 0.49 V under AM 1.5 light illumination at 100 mW/cm2 for the n- and p-type samples, respectively.

  11. Chemcatcher and DGT passive sampling devices for regulatory monitoring of trace metals in surface water.

    Science.gov (United States)

    Allan, Ian J; Knutsson, Jesper; Guigues, Nathalie; Mills, Graham A; Fouillac, Anne-Marie; Greenwood, Richard

    2008-07-01

    This work aimed to evaluate whether the performance of passive sampling devices in measuring time-weighted average (TWA) concentrations supports their application in regulatory monitoring of trace metals in surface waters, such as for the European Union's Water Framework Directive (WFD). The ability of the Chemcatcher and the diffusive gradient in thin film (DGT) device sampler to provide comparable TWA concentrations of Cd, Cu, Ni, Pb and Zn was tested through consecutive and overlapping deployments (7-28 days) in the River Meuse (The Netherlands). In order to evaluate the consistency of these TWA labile metal concentrations, these were assessed against total and filtered concentrations measured at relatively high frequencies by two teams using standard monitoring procedures, and metal species predicted by equilibrium speciation modeling using Visual MINTEQ. For Cd and Zn, the concentrations obtained with filtered water samples and the passive sampling devices were generally similar. The samplers consistently underestimated filtered concentrations of Cu and Ni, in agreement with their respective predicted speciation. For Pb, a small labile fraction was mainly responsible for low sampler accumulation and hence high measurement uncertainty. While only the high frequency of spot sampling procedures enabled the observation of higher Cd concentrations during the first 14 days, consecutive DGT deployments were able to detect it and provide a reasonable estimate of ambient concentrations. The range of concentrations measured by spot and passive sampling, for exposures up to 28 days, demonstrated that both modes of monitoring were equally reliable. Passive sampling provides information that cannot be obtained by a realistic spot sampling frequency and this may impact on the ability to detect trends and assess monitoring data against environmental quality standards when concentrations fluctuate.

  12. Effects of surface passivation by lithium on the mechanical and electronic properties of silicon nanowires

    Science.gov (United States)

    Salazar, F.; Pérez, L. A.; Cruz-Irisson, M.

    2016-12-01

    In this work, we present a density functional theory study of the mechanical and electronic properties of silicon nanowires (SiNWs) grown along the [111] crystallographic direction with a diamond structure and surface passivated with hydrogen (H) and lithium (Li) atoms. The study is performed within the local density approximation by applying the supercell method. The results indicate that the energy gap is a function of the Li concentration and the nanowire diameter. Furthermore, the Young's modulus (Y) increases as the nanowire diameter increases, consistent with experimental reports. The increase in the Li concentration at the surface leads to a larger Y value compared to the Y value of the completely H-passivated SiNWs, except for the thinner nanowires. Moreover, the structure of the latter nanowires experiences important changes when the Li concentration increases up to the maximum Li atoms per cell. These results demonstrate that it is possible to simultaneously control the energy gap and the Young's modulus by tuning the Li concentration on the surface of the SiNWs and could help to understand the structural changes that the silicon nanowire arrays experience during the lithiation process in Li batteries.

  13. A new passive seismic method based on seismic interferometry and multichannel analysis of surface waves

    Science.gov (United States)

    Cheng, Feng; Xia, Jianghai; Xu, Yixian; Xu, Zongbo; Pan, Yudi

    2015-06-01

    We proposed a new passive seismic method (PSM) based on seismic interferometry and multichannel analysis of surface waves (MASW) to meet the demand for increasing investigation depth by acquiring surface-wave data at a low-frequency range (1 Hz ≤ f ≤ 10 Hz). We utilize seismic interferometry to sort common virtual source gathers (CVSGs) from ambient noise and analyze obtained CVSGs to construct 2D shear-wave velocity (Vs) map using the MASW. Standard ambient noise processing procedures were applied to the computation of cross-correlations. To enhance signal to noise ratio (SNR) of the empirical Green's functions, a new weighted stacking method was implemented. In addition, we proposed a bidirectional shot mode based on the virtual source method to sort CVSGs repeatedly. The PSM was applied to two field data examples. For the test along Han River levee, the results of PSM were compared with the improved roadside passive MASW and spatial autocorrelation method (SPAC). For test in the Western Junggar Basin, PSM was applied to a 70 km long linear survey array with a prominent directional urban noise source and a 60 km-long Vs profile with 1.5 km in depth was mapped. Further, a comparison about the dispersion measurements was made between PSM and frequency-time analysis (FTAN) technique to assess the accuracy of PSM. These examples and comparisons demonstrated that this new method is efficient, flexible, and capable to study near-surface velocity structures based on seismic ambient noise.

  14. Interdigitated back contact silicon heterojunction solar cell and the effect of front surface passivation

    Science.gov (United States)

    Lu, Meijun; Bowden, Stuart; Das, Ujjwal; Birkmire, Robert

    2007-08-01

    This letter reports interdigitated back contact silicon heterojunction (IBC-SHJ) solar cells which combine the performance benefits of both back contact and heterojunction technologies while reducing their limitations. Low temperature (interdigitated heteroemitter and contacts in the rear preserves substrate lifetime while minimizes optical losses in the front. The IBC-SHJ structure is ideal for diagnosing surface passivation quality, which is analyzed and measured by internal quantum efficiency and minority carrier lifetime measurements. Initial cells have independently confirmed efficiency of 11.8% under AM1.5 illumination. Simulations indicate efficiencies greater than 20% after optimization.

  15. On-site solid-phase extraction and application to in situ preconcentration of heavy metals in surface water.

    Science.gov (United States)

    Jiao, Fang; Gao, Hong-Wen

    2013-01-01

    An on-site solid-phase extraction, consisting of the sorption, the separation and the elution function units, was designed for in situ preconcentration of heavy metals ions. The D401 resin powder was employed as sorbent to capture Pb(2+), Cu(2+), Zn(2+), Cd(2+), Co(2+), and Ni(2+), and then they desorbed with 2 mol/L nitric acid as eluent. Under the optimized conditions, these heavy metals ions in West Lake, Taihu Lake, and Yangtze River of China were captured and then determined by ICP-OES with the recovery of 92.5% to 111.5%. The on-site solid-phase extraction achieved a quick preconcentration of heavy metals to avoid the transport and storage of a large volume water sample. It is suitable for in situ monitoring of water quality in mountains, tablelands or other remote areas.

  16. 3D numerical simulation analysis of passive drag near free surface in swimming

    Science.gov (United States)

    Zhan, Jie-min; Li, Tian-zeng; Chen, Xue-bin; Li, Yok-sheung; Wai, Wing-hong Onyx

    2015-04-01

    The aim of this work is to build a 3D numerical model to study the characteristics of passive drag on competitive swimmers taking into account the impact of the free surface. This model solves the 3D incompressible Navier-Stokes equations using RNG k- ɛ turbulence closure. The volume of fluid (VOF) method is used to locate the free surface. The 3D virtual model is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. Firstly, a specific posture of swimming is studied. The simulation results are in good agreement with the data from mannequin towing experiments. The effects of a swimmer's arms and legs positions on swimming performance are then studied. Finally, it is demonstrated that the present method is capable of simulating gliding near the free surface.

  17. 3D Numerical Simulation Analysis of Passive Drag near Free Surface in Swimming

    Institute of Scientific and Technical Information of China (English)

    詹杰民; 李天赠; 陈学彬; 李毓湘; 韦永康

    2015-01-01

    The aim of this work is to build a 3D numerical model to study the characteristics of passive drag on competitive swimmers taking into account the impact of the free surface. This model solves the 3D incompressible Navier-Stokes equations using RNG k-εturbulence closure. The volume of fluid (VOF) method is used to locate the free surface. The 3D virtual model is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. Firstly, a specific posture of swimming is studied. The simulation results are in good agreement with the data from mannequin towing experiments. The effects of a swimmer’s arms and legs positions on swimming performance are then studied. Finally, it is demonstrated that the present method is capable of simulating gliding near the free surface.

  18. Temporal observations of surface soil moisture using a passive microwave sensor

    Science.gov (United States)

    Jackson, T. J.; O'Neill, P.

    1987-01-01

    A series of 10 aircraft flights was conducted over agricultural fields to evaluate relationships between observed surface soil moisture and soil moisture predicted using passive microwave sensor observations. An a priori approach was used to predict values of surface soil moisture for three types of fields: tilled corn, no-till corn with soybean stubble, and idle fields with corn stubble. Acceptable predictions were obtained for the tilled corn fields, while poor results were obtained for the others. The source of error is suspected to be the density and orientation of the surface stubble layer; however, further research is needed to verify this explanation. Temporal comparisons between observed, microwave predicted, and soil water-simulated moisture values showed similar patterns for tilled well-drained fields. Divergences between the observed and simulated measurements were apparent on poorly drained fields. This result may be of value in locating and mapping hydrologic contributing areas.

  19. Tropospheric CH4 signals as observed by NDACC FTIR at globally distributed sites and comparison to GAW surface in-situ measurements

    Directory of Open Access Journals (Sweden)

    E. Sepúlveda

    2014-01-01

    Full Text Available We present lower/middle tropospheric column-averaged CH4 mole fraction time series measured by nine globally distributed ground-based FTIR (Fourier Transform InfraRed remote sensing experiments of the Network for the Detection of Atmospheric Composition Change (NDACC. We show that these data are well representative of the tropospheric regional-scale CH4 signal, largely independent of the local small-scale signals of the boundary layer, and only weakly dependent on upper tropospheric/lower stratospheric (UTLS CH4 variations. In order to achieve the weak dependency on the UTLS, we use an a posteriori correction method. We estimate a typical precision for daily mean values of about 0.5% and a systematic error of about 2.5%. The theoretical assessments are complemented by an extensive empirical study. For this purpose, we use surface in-situ CH4 measurements made within the Global Atmosphere Watch (GAW network and compare them to the remote sensing data. We briefly discuss different filter methods for removing the local small-scale signals from the surface in-situ datasets in order to obtain the in-situ regional-scale signals. We find good agreement between the filtered in-situ and the remote sensing data. The agreement is consistent for a variety of time scales that are interesting for CH4 source/sink research: day-to-day, monthly, and inter-annual. The comparison study confirms our theoretical estimations and proves that the NDACC FTIR measurements can provide valuable data for investigating the cycle of CH4.

  20. Surface exposure history using in-situ cosmogenic {sup 10}Be, {sup 26}Al and {sup 36}Cl - applications to the Australian environment

    Energy Technology Data Exchange (ETDEWEB)

    Fink, D. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia). Physics Division

    1999-11-01

    Production of the long-lived cosmogenic radionuclides, {sup 10}Be (T{sub 1/2}=1.5Ma), {sup 26}Al (0.7Ma) and {sup 36}Cl (0.3Ma), is dominated by the interaction of cosmic-rays with the upper atmosphere. They are also produced in exposed surface rocks and within the first meter or so of the Earth`s crust. This is called in-situ production and although only a million atoms or so of {sup 10}Be are produced within a ten thousand year exposure period per gram of surface rock, the technique of Accelerator Mass Spectrometry (AMS) can be applied to measure this tell-tale signal. The build-up over time of these radionuclides can be utilised as radiometric clocks to elucidate the exposure history of geomorphic formations and surfaces that have experienced some event or process that delivers previously unexposed material to cosmic-ray irradiation. Hence the reconstruction of glacial chronologies (ie time a bedrock surface was uncovered by ice retreat, or deposition age of glacial moraines), development of raised river terraces and paleo-beach ridges, age of meteorite impact craters and volcanic eruptions have been addressed with the in-situ method. Moreover, geomorphological processes of landscape evolution such as surface erosion rates, continental weathering, sediment transport and deposition, uplift rates can also be studied. The in-situ method is described along with examples of cosmogenic dating projects at ANSTO. It is estimated that it works best over the time period from 5 ka to 5 Ma and can identify erosion rates ranging from 0.1 to 10 mm/ka 20 refs., 4 figs.

  1. Viral capsomere structure, surface processes and growth kinetics in the crystallization of macromolecular crystals visualized by in situ atomic force microscopy

    Science.gov (United States)

    Malkin, A. J.; Kuznetsov, Yu. G.; McPherson, A.

    2001-11-01

    In situ atomic force microscopy (AFM) was used to investigate surface evolution during the growth of single crystals of turnip yellow mosaic virus (TYMV), cucumber mosaic virus (CMV) and glucose isomerase. Growth of these crystals proceeded by two-dimensional (2D) nucleation. For glucose isomerase, from supersaturation dependencies of tangential step rates and critical step length, the kinetic coefficients of the steps and the surface free energy of the step edge were calculated for different crystallographic directions. The molecular structure of the step edges, the adsorption of individual virus particles and their aggregates, and the initial stages of formation of 2D nuclei on the surfaces of TYMV and CMV crystals were recorded. The surfaces of individual TYMV virions within crystals were visualized, and hexameric and pentameric capsomers of the T=3 capsids were clearly resolved. This, so far as we are aware, is the first direct visualization of the capsomere structure of a virus by AFM. In the course of recording the in situ development of the TYMV crystals, a profound restructuring of the surface arrangement was observed. This transformation was highly cooperative in nature, but the transitions were unambiguous and readily explicable in terms of an organized loss of classes of virus particles from specific lattice positions.

  2. Immobilization of serum albumin and peptide aptamer for EPC on polydopamine coated titanium surface for enhanced in-situ self-endothelialization

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhuoyue, E-mail: 362947953@qq.com [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu, 610031 (China); RegeMed Lab of Tissue Engineering, Faculty of Life Science, Northwest University, Xi' an, 710069 (China); Li, Quanli [College of Stomology, Anhui Medical University, Hefei, 230032 (China); Chen, Jialong [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu, 610031 (China); College of Stomology, Anhui Medical University, Hefei, 230032 (China); Luo, Rifang [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu, 610031 (China); Maitz, Manfred F. [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu, 610031 (China); Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Dresden (Germany); Huang, Nan, E-mail: huangnan1956@163.com [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu, 610031 (China)

    2016-03-01

    Restenosis and thrombosis are two major complications associated with vascular stents and grafts. The homing of circulating endothelial progenitor cells (EPCs) onto implant surfaces brings a new strategy to solve these problems by accelerating self -endothelialization in situ. Peptide aptamers with high affinity and specific recognition of EPCs can be immobilized to capture EPCs from the circulating blood. In this study, a biotinylated peptide aptamer (TPSLEQRTVYAK-GGGC-K-Biotin) for EPC, and bovine serum albumin (BSA) were co-immobilized onto titanium surface through avidin–biotin recognition to endow the surface with specific affinity for EPC and anti-platelet adhesion properties. Quartz crystal microbalance with dissipation (QCM-D), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and water contact angle measuring were adopted for coating characterization. EPC affinity and hemocompatibility of the coating were also investigated in vitro. The results demonstrated that aptamer and BSA co-immobilized surface significantly reduced platelet adhesion and fibrinogen adsorption/activation. Besides, such functional surface could remarkably enhance EPC adhesion, without affecting the behavior of endothelial cells (ECs) and smooth muscle cells (SMCs) obviously. The result shows the possibility of utilizing such a multifunctional surface in cardiovascular implants. - Highlights: • We construct a multifunctional surface based on immobilization of BSA and aptamer. • It can significantly reduce platelet adhesion and fibrinogen adsorption/activation. • Such functional surface could remarkably enhance EPC adhesion in vitro. • It can induce rapid self-endothelialization of the implant surface in situ in vivo. • It is possible to use such a multifunctional surface in cardiovascular implants.

  3. On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3

    Science.gov (United States)

    Hoex, B.; Gielis, J. J. H.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2008-12-01

    Al2O3 is a versatile high-κ dielectric that has excellent surface passivation properties on crystalline Si (c-Si), which are of vital importance for devices such as light emitting diodes and high-efficiency solar cells. We demonstrate both experimentally and by simulations that the surface passivation can be related to a satisfactory low interface defect density in combination with a strong field-effect passivation induced by a negative fixed charge density Qf of up to 1013 cm-2 present in the Al2O3 film at the interface with the underlying Si substrate. The negative polarity of Qf in Al2O3 is especially beneficial for the passivation of p-type c-Si as the bulk minority carriers are shielded from the c-Si surface. As the level of field-effect passivation is shown to scale with Qf2, the high Qf in Al2O3 tolerates a higher interface defect density on c-Si compared to alternative surface passivation schemes.

  4. Comparison of surface NMR with non-invasive and in-situ measurements of soil water content at a floodplain field site

    Science.gov (United States)

    Werban, Ulrike; Schrön, Martin; Dietrich, Peter; Walsh, David; Grunewald, Elliot; Pohle, Marco; Kathage, Susanne

    2016-04-01

    Quantification of soil water content is a very relevant issue in soil and environmental studies. There is a broad spectrum of methods applied for measuring soil water content in the field either deployed in situ or non-invasively from the surface. For many reasons the latter is preferred in field studies. Nuclear Magnetic Resonance (NMR) is one of the rare methods that measure the water content directly. Whereas others, e.g. geophysical methods, make use of proximal relationships for determination of soil water content. We applied a new single-sided NMR sensor to non-invasively measure in-situ soil moisture profiles at several points along two transects in a floodplain. The field site exhibits variations in soil water content due to morphology, e.g. flood channels and alluvial fan structures. Furthermore we applied at the same transects (1) in situ methods: soil sampling for gravimetrical analysis and TDR and (2) non-invasive methods: electromagnetical induction, mobile cosmic-ray neutron sensing with a rover and gamma-ray spectrometry. We will present results that confirm agreement of NMR and gravimetrical analysis from soil sampling and discuss issues that arise when using non-unique proxy methods and relationships for determination of soil water content.

  5. Passive monitoring for near surface void detection using traffic as a seismic source

    Science.gov (United States)

    Zhao, Y.; Kuzma, H. A.; Rector, J.; Nazari, S.

    2009-12-01

    In this poster we present preliminary results based on our several field experiments in which we study seismic detection of voids using a passive array of surface geophones. The source of seismic excitation is vehicle traffic on nearby roads, which we model as a continuous line source of seismic energy. Our passive seismic technique is based on cross-correlation of surface wave fields and studying the resulting power spectra, looking for "shadows" caused by the scattering effect of a void. High frequency noise masks this effect in the time domain, so it is difficult to see on conventional traces. Our technique does not rely on phase distortions caused by small voids because they are generally too tiny to measure. Unlike traditional impulsive seismic sources which generate highly coherent broadband signals, perfect for resolving phase but too weak for resolving amplitude, vehicle traffic affords a high power signal a frequency range which is optimal for finding shallow structures. Our technique results in clear detections of an abandoned railroad tunnel and a septic tank. The ultimate goal of this project is to develop a technology for the simultaneous imaging of shallow underground structures and traffic monitoring near these structures.

  6. In situ fabrication of silver nanoparticle-filled hydrogen titanate nanotube layer on metallic titanium surface for bacteriostatic and biocompatible implantation.

    Science.gov (United States)

    Wang, Zheng; Sun, Yan; Wang, Dongzhou; Liu, Hong; Boughton, Robert I

    2013-01-01

    A silver nanoparticle (AgNP)-filled hydrogen titanate nanotube layer was synthesized in situ on a metallic titanium substrate. In the synthesis approach, a layer of sodium titanate nanotubes is first prepared on the titanium surface by using a hydrothermal method. Silver nitrate solution is absorbed into the nanotube channels by immersing a dried nanotube layer in silver nitrate solution. Finally, silver ions are reduced by glucose, leading to the in situ growth of AgNPs in the hydrogen titanate nanotube channels. Long-term silver release and bactericidal experiments demonstrated that the effective silver release and effective antibacterial period of the titanium foil with a AgNP-filled hydrogen titanate nanotube layer on the surface can extend to more than 15 days. This steady and prolonged release characteristic is helpful to promote a long-lasting antibacterial capability for the prevention of severe infection after surgery. A series of antimicrobial and biocompatible tests have shown that the sandwich nanostructure with a low level of silver loading exhibits a bacteriostatic rate as high as 99.99%, while retaining low toxicity for cells and possessing high osteogenic potential. Titanium foil with a AgNP-filled hydrogen titanate nanotube layer on the surface that is fabricated with low-cost surface modification methods is a promising implantable material that will find applications in artificial bones, joints, and dental implants.

  7. Use of In Situ Cloud Condensation Nuclei, Extinction, and Aerosol Size Distribution Measurements to Test a Method for Retrieving Cloud Condensation Nuclei Profiles From Surface Measurements

    Science.gov (United States)

    Ghan, Stephen J.; Rissman, Tracey A.; Ellman, Robert; Ferrare, Richard A.; Turner, David; Flynn, Connor; Wang, Jian; Ogren, John; Hudson, James; Jonsson, Haflidi H.; VanReken, Timothy; Flagan, Richard C.; Seinfeld, John H.

    2006-01-01

    If the aerosol composition and size distribution below cloud are uniform, the vertical profile of cloud condensation nuclei (CCN) concentration can be retrieved entirely from surface measurements of CCN concentration and particle humidification function and surface-based retrievals of relative humidity and aerosol extinction or backscatter. This provides the potential for long-term measurements of CCN concentrations near cloud base. We have used a combination of aircraft, surface in situ, and surface remote sensing measurements to test various aspects of the retrieval scheme. Our analysis leads us to the following conclusions. The retrieval works better for supersaturations of 0.1% than for 1% because CCN concentrations at 0.1% are controlled by the same particles that control extinction and backscatter. If in situ measurements of extinction are used, the retrieval explains a majority of the CCN variance at high supersaturation for at least two and perhaps five of the eight flights examined. The retrieval of the vertical profile of the humidification factor is not the major limitation of the CCN retrieval scheme. Vertical structure in the aerosol size distribution and composition is the dominant source of error in the CCN retrieval, but this vertical structure is difficult to measure from remote sensing at visible wavelengths.

  8. Precise parameterization of the recombination velocity at passivated phosphorus doped surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kimmerle, Achim, E-mail: achim-kimmerle@gmx.de; Momtazur Rahman, Md.; Werner, Sabrina; Mack, Sebastian; Wolf, Andreas; Richter, Armin [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstraße 2, 79110 Freiburg (Germany); Haug, Halvard [Institute for Energy Technology, Instituttveien 18, 2007 Kjeller (Norway)

    2016-01-14

    We investigate the surface recombination velocity S{sub p} at the silicon-dielectric interface of phosphorus-doped surfaces for two industrially relevant passivation schemes for crystalline silicon solar cells. A broad range of surface dopant concentrations together with a high accuracy of evaluating the latter is achieved by incremental back-etching of the surface. The analysis of lifetime measurements and the simulation of the surface recombination consistently apply a set of well accepted models, namely, the Auger recombination by Richter et al. [Phys. Rev. B 86, 1–14 (2012)], the carrier mobility by Klaassen [Solid-State Electron. 35, 953–959 (1992); 35, 961–967 (1992)], the intrinsic carrier concentration for undoped silicon by Altermatt et al. [J. Appl. Phys. 93, 1598–1604 (2003)], and the band-gap narrowing by Schenk [J. Appl. Phys. 84, 3684–3695 (1998)]. The results show an increased S{sub p} at textured in respect to planar surfaces. The obtained parameterizations are applicable in modern simulation tools such as EDNA [K. R. McIntosh and P. P. Altermatt, in Proceedings of the 35th IEEE Photovoltaic Specialists Conference, Honolulu, Hawaii, USA (2010), pp. 1–6], PC1Dmod [Haug et al., Sol. Energy Mater. Sol. Cells 131, 30–36 (2014)], and Sentaurus Device [Synopsys, Sentaurus TCAD, Zürich, Switzerland] as well as in the analytical solution under the assumption of local charge neutrality by Cuevas et al. [IEEE Trans. Electron Devices 40, 1181–1183 (1993)].

  9. Precise parameterization of the recombination velocity at passivated phosphorus doped surfaces

    Science.gov (United States)

    Kimmerle, Achim; Momtazur Rahman, Md.; Werner, Sabrina; Mack, Sebastian; Wolf, Andreas; Richter, Armin; Haug, Halvard

    2016-01-01

    We investigate the surface recombination velocity Sp at the silicon-dielectric interface of phosphorus-doped surfaces for two industrially relevant passivation schemes for crystalline silicon solar cells. A broad range of surface dopant concentrations together with a high accuracy of evaluating the latter is achieved by incremental back-etching of the surface. The analysis of lifetime measurements and the simulation of the surface recombination consistently apply a set of well accepted models, namely, the Auger recombination by Richter et al. [Phys. Rev. B 86, 1-14 (2012)], the carrier mobility by Klaassen [Solid-State Electron. 35, 953-959 (1992); 35, 961-967 (1992)], the intrinsic carrier concentration for undoped silicon by Altermatt et al. [J. Appl. Phys. 93, 1598-1604 (2003)], and the band-gap narrowing by Schenk [J. Appl. Phys. 84, 3684-3695 (1998)]. The results show an increased Sp at textured in respect to planar surfaces. The obtained parameterizations are applicable in modern simulation tools such as EDNA [K. R. McIntosh and P. P. Altermatt, in Proceedings of the 35th IEEE Photovoltaic Specialists Conference, Honolulu, Hawaii, USA (2010), pp. 1-6], PC1Dmod [Haug et al., Sol. Energy Mater. Sol. Cells 131, 30-36 (2014)], and Sentaurus Device [Synopsys, Sentaurus TCAD, Zürich, Switzerland] as well as in the analytical solution under the assumption of local charge neutrality by Cuevas et al. [IEEE Trans. Electron Devices 40, 1181-1183 (1993)].

  10. High efficiency photoluminescence from silicon nanocrystals prepared by plasma synthesis and organic surface passivation

    Energy Technology Data Exchange (ETDEWEB)

    Mangolini, L.; Kortshagen, U. [Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Jurbergs, D.; Rogojina, E. [Innovalight Inc., 3303 Octavius Drive Suite 104, Santa Clara, CA 95054 (United States)

    2006-07-01

    An efficient synthesis route for highly luminescent silicon quantum dots is presented. Silicon nanocrystals were synthesized in the gas phase using an argon-silane non-thermal plasma in a continuous flow reactor. Liquid phase surface passivation was used to improve the optical properties and avoid surface oxidation of the silicon quantum dots. Various alkenes, such as octadecene, dodecene and styrene, were covalently bonded to the plasma-produced particles, while strictly avoiding exposure of the raw powder to oxidizing agents. Stable colloidal solutions of silicon quantum dots with ensemble quantum yields between 60% and 70% were achieved. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

    Science.gov (United States)

    Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

    2015-07-29

    The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a

  12. Passivating surface states on water splitting hematite photoanodes with alumina overlayers

    KAUST Repository

    Le Formal, Florian

    2011-01-24

    Hematite is a promising material for inexpensive solar energy conversion via water splitting but has been limited by the large overpotential (0.5-0.6 V) that must be applied to afford high water oxidation photocurrent. This has conventionally been addressed by coating it with a catalyst to increase the kinetics of the oxygen evolution reaction. However, surface recombination at trapping states is also thought to be an important factor for the overpotential, and herein we investigate a strategy to passivate trapping states using conformal overlayers applied by atomic layer deposition. While TiO2 overlayers show no beneficial effect, we find that an ultra-thin coating of Al2O3 reduces the overpotential required with state-of-the-art nano-structured photo-anodes by as much as 100 mV and increases the photocurrent by a factor of 3.5 (from 0.24 mA cm-2 to 0.85 mA cm-2) at +1.0 V vs. the reversible hydrogen electrode (RHE) under standard illumination conditions. The subsequent addition of Co2+ ions as a catalyst further decreases the overpotential and leads to a record photocurrent density at 0.9 V vs. RHE (0.42 mA cm-2). A detailed investigation into the effect of the Al2O3 overlayer by electrochemical impedance and photoluminescence spectroscopy reveals a significant change in the surface capacitance and radiative recombination, respectively, which distinguishes the observed overpotential reduction from a catalytic effect and confirms the passivation of surface states. Importantly, this work clearly demonstrates that two distinct loss processes are occurring on the surface of high-performance hematite and suggests a viable route to individually address them. © The Royal Society of Chemistry 2011.

  13. Stabilization and acidic dissolution mechanism of single-crystalline ZnO(0001) surfaces in electrolytes studied by in-situ AFM imaging and ex-situ LEED.

    Science.gov (United States)

    Valtiner, Markus; Borodin, Sergiy; Grundmeier, Guido

    2008-05-20

    A combined approach of pH-dependent in-situ AFM topography and ex-situ LEED studies of the stability and dissolution of single-crystalline ZnO(0001)-Zn surfaces in aqueous media is presented. Hydroxide-stabilized and single-crystalline ZnO(0001)-Zn surfaces turned out to be stable within a wide pH range between 11 and 4 around the point of zero charge of pH PZC = 8.7 +/- 0.2. Hydroxide stabilization turned out to be a very effective stabilization mechanism for polar oxide surfaces in electrolyte solutions. The dissolution of the oxide surface started at an acidic pH level of 5.5 and occurred selectively at the pre-existing step edges, which consist of nonpolar surfaces. In comparison, the oxide dissolution along the ZnO(0001) direction proved to be effectively inhibited above a pH value of 3.8. On the basis of these microscopic observations, the mechanistic understanding of the acidic dissolution process of ZnO could be supported. Moreover, both the in-situ AFM and the ex-situ LEED studies showed that the stabilization mechanism of the ZnO(0001) surfaces changes in acidic electrolytes. At pH values below 3.8, the hydroxide-stabilized surface is destabilized by dissolution of the well-ordered radical3. radical3. R30 hydroxide ad-layer as proven by LEED. Restabilization occurs and leads to the formation of triangular nanoterraces with a specific edge termination. However, below pH 4 the surface structure of the crystal itself is ill-defined on the macroscopic scale because preferable etching along crystal defects as dislocations into the bulk oxide results in very deep hexagonal etching pits.

  14. Active and Passive Remote Sensing Data Time Series for Flood Detection and Surface Water Mapping

    Science.gov (United States)

    Bioresita, Filsa; Puissant, Anne; Stumpf, André; Malet, Jean-Philippe

    2017-04-01

    As a consequence of environmental changes surface waters are undergoing changes in time and space. A better knowledge of the spatial and temporal distribution of surface waters resources becomes essential to support sustainable policies and development activities. Especially because surface waters, are not only a vital sweet water resource, but can also pose hazards to human settlements and infrastructures through flooding. Floods are a highly frequent disaster in the world and can caused huge material losses. Detecting and mapping their spatial distribution is fundamental to ascertain damages and for relief efforts. Spaceborne Synthetic Aperture Radar (SAR) is an effective way to monitor surface waters bodies over large areas since it provides excellent temporal coverage and, all-weather day-and-night imaging capabilities. However, emergent vegetation, trees, wind or flow turbulence can increase radar back-scatter returns and pose problems for the delineation of inundated areas. In such areas, passive remote sensing data can be used to identify vegetated areas and support the interpretation of SAR data. The availability of new Earth Observation products, for example Sentinel-1 (active) and Sentinel-2 (passive) imageries, with both high spatial and temporal resolution, have the potential to facilitate flood detection and monitoring of surface waters changes which are very dynamic in space and time. In this context, the research consists of two parts. In the first part, the objective is to propose generic and reproducible methodologies for the analysis of Sentinel-1 time series data for floods detection and surface waters mapping. The processing chain comprises a series of pre-processing steps and the statistical modeling of the pixel value distribution to produce probabilistic maps for the presence of surface waters. Images pre-processing for all Sentinel-1 images comprise the reduction SAR effect like orbit errors, speckle noise, and geometric effects. A modified

  15. In Situ Immobilization on the Silica Gel Surface and Adsorption Capacity of Poly[ N-(4-carboxyphenyl)methacrylamide] on Toxic Metal Ions

    Science.gov (United States)

    Yanovska, Elina; Savchenko, Irina; Sternik, Dariusz; Kychkiruk, Olga; Ol'khovik, Lidiya; Buriachenko, Iana

    2017-04-01

    In situ immobilization of poly[ N-(4-carboxyphenyl)methacrylamide] has been performed on silica gel surface. Infrared (IR) and mass spectroscopies as well as thermogravimetry (TG) analysis have been used to elucidate the structure of immobilized polymer. An adsorption capacity of the synthesized composite towards Cu(II), Pb(II), Mn(II), Fe(III), Co(II), and Ni(II) ions has been estimated. Adsorption activity to microquantities of Pb(II), Cu(II), and Ni(II) in a neutral aqueous medium has been observed.

  16. A climatology of Brazilian surface wind speed trends using in-situ and climate reanalysis datasets from 1980-2014

    Science.gov (United States)

    Gilliland, J. M.; Keim, B. D.

    2015-12-01

    Wind speed trends have been extensively researched for the Northern Hemisphere and Australia. The general consensus among scientists is that wind speeds have declined over the past century. However, a minimal amount of research has focused on understanding how wind speeds changed across Brazil based on temporal and geographical perspectives. Therefore, this study provides a climatological assessment of wind speed trends across Brazil using in-situ and climatic model datasets from 1980-2014. Seasonal and annual trends are determined across the study area using linear and quantile regression. Geographical Information Systems is used to interpret and understand how wind speed trends have changed across Brazil. Preliminary results show two distinct wind speed trend patterns exist across Brazil. The largest wind speed magnitude increases occurred along northeastern and coastal Brazil, where as decreasing wind speeds have been observed for central and southeastern Brazil. Furthermore, quantile regression also shows the largest seasonal and annual wind trend fluctuations occur at lower (5%) and upper percentiles (95%) for both in-situ and climate model datasets. As a result, these findings indicate possible alterations in atmospheric and oceanic circulations could be affecting wind speed trends across Brazil and warrants further investigation and research.

  17. Carbon nanotube surface modification with polyelectrolyte brushes endowed with quantum dots and metal oxide nanoparticles through in situ synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Llarena, Irantzu; Romero, Gabriela; Moya, Sergio E [CIC biomaGUNE Paseo Miramon, 182 Edificio Empresarial C, E-20009 San Sebastian, Gipuzkoa (Spain); Ziolo, Ronald F, E-mail: smoya@cicbiomagune.es [Centro de Investigacion en Quimica Aplicada, Blv. Enrique Reyna No. 140, Saltillo, Coahuila 25253 (Mexico)

    2010-02-05

    Carbon nanotubes (CNTs) have been successfully coated with a covalently bonded polymer brush of negatively charged poly(3-sulfopropylamino methacrylate) (PSPM) by in situ polymerization employing atomic transfer radical polymerization (ATRP) from initiating silanes attached to the CNTs before the polymerization. The CNT-bonded brush forms a polymer layer or shell-like structure around the CNTs and provides colloidal stabilization for the CNTs in aqueous media. In situ syntheses of nanocrystalline CdS and magnetic iron oxide in the polymer brushes lead to the formation of hybrid nanocomposites consisting of nanoparticle-containing PSPM-coated CNTs that remain readily dispersible and stable in aqueous media. The hybrid nanostructures are synthesized by ion exchange with the cations of the sulfonate groups of the PSPM followed by precipitation and were followed by stepwise zeta potential measurements and TEM. Such structures could have applications in the design of more complex structures and devices. The general synthetic scheme can be extended to include other nanoparticles as brush cargo to broaden the utility or functionality of the CNTs. TEM data shows nanocrystalline CdS in the range of 5-8 nm embedded in the PSPM brush and nanocrystalline iron oxide with a size between 2 and 4 nm, with the former consistent with UV-vis spectroscopy and fluorescence measurements.

  18. Portable Sequentially Shifted Excitation Raman spectroscopy as an innovative tool for in situ chemical interrogation of painted surfaces.

    Science.gov (United States)

    Conti, Claudia; Botteon, Alessandra; Bertasa, Moira; Colombo, Chiara; Realini, Marco; Sali, Diego

    2016-08-07

    We present the first validation and application of portable Sequentially Shifted Excitation (SSE) Raman spectroscopy for the survey of painted layers in art. The method enables the acquisition of shifted Raman spectra and the recovery of the spectral data through the application of a suitable reconstruction algorithm. The technique has a great potentiality in art where commonly a strong fluorescence obscures the Raman signal of the target, especially when conventional portable Raman spectrometers are used for in situ analyses. Firstly, the analytical capability of portable SSE Raman spectroscopy is critically discussed using reference materials and laboratory specimens, comparing its results with other conventional high performance laboratory instruments (benchtop FT-Raman and dispersive Raman spectrometers with an external fiber optic probe); secondly, it is applied directly in situ to study the complex polychromy of Italian prestigious terracotta sculptures of the 16(th) century. Portable SSE Raman spectroscopy represents a new investigation modality in art, expanding the portfolio of non-invasive, chemically specific analytical tools.

  19. Ab initio study of subsurface diffusion of Cu on the H-passivated Si(001) surface

    Science.gov (United States)

    Rodriguez-Prieto, A.; Bowler, D. R.

    2009-10-01

    In this paper we use density-functional theory calculations to analyze both the stability and diffusion of Cu adatoms near and on the H-passivated Si(001) surface. Two different Cu sources are considered: depositing Cu from vacuum, and contaminating Cu outdiffusing from bulk Si. Deposited Cu from vacuum quickly moves subsurface to an interstitial site in the third Si layer (T2). Once there, Cu adatoms enter a subsurface zigzag migration route between T2 and another subsurface site, T2→HSL→T2 , along the dimer row direction. Contaminating Cu outdiffusing from bulk is found to be a fast diffuser along both parallel and perpendicular directions to the dimer row when far from the surface. It is attracted to the layers close to the surface and becomes trapped at an interstitial site located at the sixth Si layer (T3). As the outdiffusing Cu atoms get closer to the surface, a channeling zigzag diffusion along the dimer row direction, similar to that one followed by deposited Cu from vacuum, is favoured over diffusion along the perpendicular direction. These results are consistent with previous experimental work done on similar systems and will motivate further experiments on the interesting interaction between Cu and Si surfaces.

  20. Fabrication of Co/Si nanowires by ultrahigh-vacuum scanning tunneling microscopy on hydrogen-passivated Si(100) surfaces

    NARCIS (Netherlands)

    Palasantzas, G; Ilge, B; De Nijs, J

    1999-01-01

    We have fabricated nanometer width Co/Si metal lines on Si(100) surfaces by ultrahigh-vacuum scanning tunneling microscopy (UHVSTM) based nanolithography on the hydrogen-passivated surface, combined with vapor deposition of Co at room temperature and subsequent annealing. The STM tip was used to def

  1. In situ Fourier transform-infrared internal reflection spectroscopic analysis of hydrocarbon chain ordering of surfactants adsorbed at mineral oxide surfaces

    Science.gov (United States)

    Cross, William Murray

    The adsorption of surfactants at mineral oxide surfaces was investigated by in situ Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS), and contact angle goniometry. FT-IR/IRS was used to determine both adsorption isotherms and the enthalpy of adsorption. Furthermore, the conformation and orientation of the hydrocarbon chain of SDS adsorbed at a sapphire internal reflection element (IRE) were determined. Contact angle goniometry was used to measure the effect of the surface phase of the surfactant on the hydrophobic character of sapphire surfaces in aqueous solutions. For SDS adsorbed by sapphire, in situ FT-IR/IRS experiments indicate that a surface phase transition occurs at an adsorption density of 2 to 3 x 10-10 mol/cm2 for both pD 2.9 and 6.9. This transition is characterized by a two to four wavenumber shift in the position of the asymmetric -CH2 stretching band. Based on solution spectroscopy studies, the surface phase was found to be similar to solution phase micelles and liquid crystals for adsorption densities less than the adsorption density of the surface phase transition. Whereas for adsorption densities in excess of the adsorption density of the surface phase transition, the surface phase resembled a solution phase coagel species. It was also found that the contact angle of an air bubble at the sapphire surface exhibited a sharp decrease at the adsorption density corresponding to the surface phase transition The effect of temperature on adsorption and phase behavior of SDS at the sapphire IRE surface was also determined. It was shown that a surface phase transition similar to that discussed occurred at approximately 298 K. The adsorption reaction was found to be exothermic, with a heat of adsorption of --1.3 kcal/mole for adsorption densities less than the adsorption density of the surface phase transition at 298 K and --4.1 kcal/mole for adsorption densities greater than the adsorption density of the surface phase transition

  2. Characterizing Greenland ice sheet surface mass balance via assimilation of spaceborne surface temperature, albedo, and passive microwave data into a physically-based model

    Science.gov (United States)

    Navari, M.; Bateni, S.; Margulis, S. A.; Alexander, P. M.; Tedesco, M.

    2012-12-01

    The Greenland ice sheet (GrIS) has been the focus of climate studies due to its significant impact on sea level rise and Arctic climate. Accurate estimates of space-time maps of surface mass balance (SMB) components including precipitation, runoff, and evaporation over the GrIS would contribute to understanding the cause of its recent unprecedented changes (e.g., increase in melt amount and duration, thickening of ice sheet interior, and thinning at the margins) and forecasting its changes in the future. In situ measurement of the SMB components across the GrIS is difficult and costly, and thus there are only a limited number of sparse measurements. Remote sensing retrievals are capable of providing some estimates of SMB terms and/or SMB indicators (i.e. melt onset), but generally provide an incomplete picture of the SMB. Additional efforts have focused on the use of regional climate models coupled to surface models in an effort to obtain spatially and temporally continuous estimates of the SMB. However, these estimates are prone to model errors and are generally unconstrained by the remote sensing record. To overcome these uncertainties and consequently improve estimates of the GrIS SMB, an ensemble data assimilation approach is developed for characterizing the SMB and its uncertainty. The EnBS consists of two steps: forecast and update. In the forecast step, an unconditional estimate of SMB using the MAR regional climate model and an ensemble implementation of the CROCUS snow is obtained that includes appropriate uncertainty in key SMB forcings. In the update step, the estimate is conditioned on remotely sensed land surface temperature (LST), albedo, and passive microwave (1.4, 6.9, 18.7, 36.5, and 89 GHz) measurements to provide a posterior estimate of the GrIS SMB components. The end result is an estimate that benefits from the regional atmospheric and snow models, but is also constrained by remote sensing data streams. The assimilation approach is tested for

  3. Passive in-situ chemical sensor

    Science.gov (United States)

    Morrell, Jonathan S.; Ripley, Edward B.

    2012-02-14

    A chemical sensor for assessing a chemical of interest. In typical embodiments the chemical sensor includes a first thermocouple and second thermocouple. A reactive component is typically disposed proximal to the second thermal couple, and is selected to react with the chemical of interest and generate a temperature variation that may be detected by a comparison of a temperature sensed by the second thermocouple compared with a concurrent temperature detected by the first thermocouple. Further disclosed is a method for assessing a chemical of interest and a method for identifying a reaction temperature for a chemical of interest in a system.

  4. Surface passivity largely governs the bioaccessibility of nickel-based powder particles at human exposure conditions.

    Science.gov (United States)

    Hedberg, Yolanda S; Herting, Gunilla; Latvala, Siiri; Elihn, Karine; Karlsson, Hanna L; Odnevall Wallinder, Inger

    2016-11-01

    The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, are identified and proven safe for humans and the environment. Therefore, differences in bioaccessibility in terms of released metals in synthetic biological fluids (different pH (1.5-7.4) and composition) that are relevant for different human exposure routes (inhalation, ingestion, and dermal contact) have been assessed for powder particles of an alloy containing high levels of nickel (Inconel 718, 57 wt% nickel). This powder is compared with the bioaccessibility of two nickel-containing stainless steel powders (AISI 316L, 10-12% nickel) and with powders representing their main pure alloy constituents: two nickel metal powders (100% nickel), two iron metal powders and two chromium metal powders. X-ray photoelectron spectroscopy, microscopy, light scattering, and nitrogen absorption were employed for the particle and surface oxide characterization. Atomic absorption spectroscopy was used to quantify released amounts of metals in solution. Cytotoxicity (Alamar blue assay) and DNA damage (comet assay) of the Inconel powder were assessed following exposure of the human lung cell line A549, as well as its ability to generate reactive oxygen species (DCFH-DA assay). Despite its high nickel content, the Inconel alloy powder did not release any significant amounts of metals and did not induce any toxic response. It is concluded, that this is related to the high surface passivity of the Inconel powder governed by its chromium-rich surface oxide. Read-across from the pure metal constituents is hence not recommended either for this or any other passive alloy.

  5. Surface Passivation of ZrO2 Artificial Dentures by Magnetized Coaxial Plasma deposition

    Science.gov (United States)

    Arai, Soya; Kurumi, Satoshi; Matsuda, Ken-Ichi; Suzuki, Kaoru; Hara, Katsuya; Kato, Tatsuya; Asai, Tomohiko; Hirose, Hideharu; Masutani, Shigeyuki; Nihon University Team

    2015-09-01

    Recent growth and fabrication technologies for functional materials have been greatly contributed to drastic development of oral surgery field. Zirconia based ceramics is expected to utilize artificial dentures because these ceramics have good biocompatibility, high hardness and aesthetic attractively. However, to apply these ceramics to artificial dentures, this denture is removed from a dental plate because of weakly bond. For improving this problem, synthesis an Al passivation-layer on the ceramics for bonding with these dental items is suitable. In order to deposit the passivation layer, we focused on a magnetized coaxial plasma deposition (MCPD). The greatest characteristic of MCPD is that high-melting point metal can be deposited on various substrates. Additionally, adhesion force between substrate and films deposited by the MCPD is superior to it of general deposition methods. In this study, we have reported on the growth techniques of Al films on ZrO2 for contributing to oral surgery by the MCPD. Surface of deposited films shows there were some droplets and thickness of it is about 200 nm. Thickness is increased to 500 nm with increasing applied voltage.

  6. A wireless demodulation system for passive surface acoustic wave torque sensor

    Science.gov (United States)

    Ji, Xiaojun; Fan, Yanping; Qi, Hongli; Chen, Jing; Han, Tao; Cai, Ping

    2014-12-01

    Surface acoustic wave (SAW) resonators are utilized as torque sensors for their passive and wireless features. However, the response of a SAW torque sensor is difficult to detect because of the transient response duration and interruption of channel noise, which limit the application of SAW torque sensors. The sensitive mechanism and response function of a passive wireless SAW torque sensor are analyzed in this study. A novel demodulation system involving both hardware and software is developed for the SAW torque sensor. A clipping amplifier is utilized in the hardware to widen the dynamic response range and increase the length of the valid signal. Correlation extension and centroid algorithms are designed to lengthen the received signal and improve the estimation accuracy of the center frequency of the response signal, respectively. Meanwhile, a fast binary search algorithm is proposed to accelerate the scanning cycle according to the developed response function. Finally, the SAW torque sensor demodulation system is set up and SAW resonators with high sensitivity are fabricated on a quartz substrate. The presented demodulation system is tested, and a standard deviation of 0.28 kHz is achieved. This value is much smaller than that of classic and modern spectrum estimation methods. The sensitivity of resonance frequency shift versus torque on the shaft of the assembled senor is 2.03 kHz/Nm; the coefficient of determination is 0.999, and the linearity is 0.87%. Experimental results verify the validity and feasibility of the proposed SAW torque sensor demodulation system.

  7. In Situ Mapping of the Molecular Arrangement of Amphiphilic Dye Molecules at the TiO 2 Surface of Dye-Sensitized Solar Cells

    KAUST Repository

    Voïtchovsky, Kislon

    2015-05-27

    © 2015 American Chemical Society. Amphiphilic sensitizers are central to the function of dye-sensitized solar cells. It is known that the cell\\'s performance depends on the molecular arrangement and the density of the dye on the semiconductor surface, but a molecular-level picture of the cell-electrolyte interface is still lacking. Here, we present subnanometer in situ atomic force microscopy images of the Z907 dye at the surface of TiO2 in a relevant liquid. Our results reveal changes in the conformation and the lateral arrangement of the dye molecules, depending on their average packing density on the surface. Complementary quantitative measurements on the ensemble of the film are obtained by the quartz-crystal microbalance with dissipation technique. An atomistic picture of the dye coverage-dependent packing, the effectiveness of the hydrophobic alkyl chains as blocking layer, and the solvent accessibility is obtained from molecular dynamics simulations. (Figure Presented).

  8. Surface corrosion enhancement of passive films on NiTi shape memory alloy in different solutions.

    Science.gov (United States)

    Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Limin, Dong

    2016-06-01

    The corrosion behaviors of NiTi shape memory alloy in NaCl solution, H2SO4 solution and borate buffer solution were investigated. It was found that TiO2 in passive film improved the corrosion resistance of NiTi shape memory. However, low corrosion resistance of passive film was observed in low pH value acidic solution due to TiO2 dissolution. Moreover, the corrosion resistance of NiTi shape memory alloy decreased with the increasing of passivated potential in the three solutions. The donor density in passive film increased with the increasing of passivated potential. Different solutions affect the semiconductor characteristics of the passive film. The reducing in the corrosion resistance was attributed to the more donor concentrations in passive film and thinner thickness of the passive film.

  9. Surface passivation of GaInAsSb photodiodes with thioacetamide

    Energy Technology Data Exchange (ETDEWEB)

    Salesse, A.; Joullie, A.; Chevrier, F.; Cuminal, Y.; Ferblantier, G.; Christol, P. [Institut d' Electronique du Sud (IES-CEM2), UMR CNRS 5507, Case 067, Universite Montpellier 2, 34 095 Montpellier Cedex 05 (France); Calas, P. [UMR CNRS 5073 CHIMIE, Case 017, Universite Montpellier 2, 34 095 Montpellier Cedex 05 (France); Nieto, J. [Instituto de Investigacion en Comunicacion Optica (IICO), Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico)

    2007-04-15

    AlGaAsSb/GaInAsSb heterojunction mesa photodiodes having 2.2 {mu}m cutoff wavelength, grown by MBE on (p) GaSb substrates, have been passivated using thioacetamide CH{sub 4}CSNH{sub 2} and ammonium sulphide (NH{sub 4}){sub 2}S. Superior characteristics were obtained from devices processed with thioacetamide in acid medium (pH=2.4). At room temperature the surface leakage currents were suppressed, and the photodiodes showed R{sub 0}A product as high as 16 {omega}cm{sup 2} and detectivity D{sup *}(2 {mu}m,0 V){proportional_to}10{sup 10} cmHz{sup 1/2}W{sup -1}. A model explaining sulfuration mechanisms with thioacetamide and (NH{sub 4}){sub 2}S is proposed. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Remote vibration measurement: a wireless passive surface acoustic wave resonator fast probing strategy.

    Science.gov (United States)

    Friedt, J-M; Droit, C; Ballandras, S; Alzuaga, S; Martin, G; Sandoz, P

    2012-05-01

    Surface acoustic wave (SAW) resonators can advantageously operate as passive sensors which can be interrogated through a wireless link. Amongst the practical applications of such devices, structural health monitoring through stress measurement and more generally vibration characteristics of mechanical structures benefit from the ability to bury such sensors within the considered structure (wireless and battery-less). However, measurement bandwidth becomes a significant challenge when measuring wideband vibration characteristics of mechanical structures. A fast SAW resonator measurement scheme is demonstrated here. The measurement bandwidth is limited by the physical settling time of the resonator (Q/π periods), requiring only two probe pulses through a monostatic RADAR-like electronic setup to identify the sensor resonance frequency and hence stress on a resonator acting as a strain gauge. A measurement update rate of 4800 Hz using a high quality factor SAW resonator operating in the 434 MHz Industrial, Scientific and Medical band is experimentally demonstrated.

  11. Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

    Institute of Scientific and Technical Information of China (English)

    Da-wen Zeng

    2015-01-01

    In this work, an in situ synthesized TiC-reinforced metal matrix composite (MMC) coating of approximately 350–400μm thick-ness was fabricated on a gray cast iron (GCI) substrate by plasma transferred arc (PTA) surface alloying of Ti–Fe alloy powder. Microhard-ness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy (SEM) and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual austenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures (473 K and 623 K), and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the sam-ples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstruc-ture and to the presence of TiC particles.

  12. Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

    Science.gov (United States)

    Zhao, Hang; Li, Jian-jun; Zheng, Zhi-zhen; Wang, Ai-hua; Huang, Qi-wen; Zeng, Da-wen

    2015-12-01

    In this work, an in situ synthesized TiC-reinforced metal matrix composite (MMC) coating of approximately 350-400 µm thickness was fabricated on a gray cast iron (GCI) substrate by plasma transferred arc (PTA) surface alloying of Ti-Fe alloy powder. Microhardness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy (SEM) and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual austenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures (473 K and 623 K), and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the samples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstructure and to the presence of TiC particles.

  13. Transparent, flexible surface enhanced Raman scattering substrates based on Ag-coated structured PET (polyethylene terephthalate) for in-situ detection

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Zewen, E-mail: zuozewen@mail.ahnu.edu.cn; Zhu, Kai; Gu, Chuan; Wen, Yibing; Cui, Guanglei; Qu, Jun

    2016-08-30

    Highlights: • Transparent, flexible SERS substrates were prepared using techniques compatible with well-established silicon device technologies. • The SERS substrates exhibit high sensitivity and good reproducibility. • The high performance is related with the quasi-three-dimensional structure of the PET. • In-situ detection of analyte on irregular objects was achieved by this SERS substrate. - Abstract: Transparent, flexible surface-enhanced Raman scattering (SERS) substrates were fabricated by metalization of structured polyethylene terephthalate (PET) sheets. The resultant Ag-coated structured PET SERS substrates were revealed to be highly sensitive with good reproducibility and stability, an enhancement factor of 3 × 10{sup 6} was acquired, which can be attributed mainly to the presence of plentiful multiple-type hot spots within the quasi-three-dimensional surface of the structured PET obtained by oxygen plasma etching. In addition, detections of model molecules on fruit skin were also carried out, demonstrating the great potential of the Ag-coated structured PET in in-situ detection of analyte on irregular objects. Importantly, the technique used for the preparation of such substrate is completely compatible with well-established silicon device technologies, and large-area fabrication with low cost can be readily realized.

  14. Polymer Nanocomposite Film with Metal Rich Surface Prepared by In Situ Single-Step Formation of Palladium Nanoparticles: An Interesting Way to Combine Specific Functional Properties

    Directory of Open Access Journals (Sweden)

    David Thompson

    2016-10-01

    Full Text Available This paper presents a continuous single-step route that permits preparation of a thermostable polymer/metal nanocomposite film and to combine different functional properties in a unique material. More precisely, palladium nanoparticles are in situ generated in a polyimide matrix thanks to a designed curing cycle which is applied to a polyamic acid/metal precursor solution cast on a glass plate. A metal-rich surface layer which is strongly bonded to the bulk film is formed in addition to homogeneously dispersed metal nanoparticles. This specific morphology leads to obtaining an optically reflective film. The metal nanoparticles act as gas diffusion barriers for helium, oxygen, and carbon dioxide; they induce a tortuosity effect which allows dividing the gas permeation coefficients by a factor near to 2 with respect to the neat polyimide matrix. Moreover, the ability of the in situ synthesized palladium nanoparticles to entrap hydrogen is evidenced. The nanocomposite film properties can be modulated as a function of the location of the film metal-rich surface with respect to the hydrogen feed. The synthesized nanocomposite could represent a major interest for a wide variety of applications, from specific coatings for aerospace or automotive industry, to catalysis applications or sensors.

  15. Spatially-Dependent Measurements of Surface and Near-Surface Radioactive Material Using In situ Gamma Ray Spectrometry (ISGRS) For Final Status Surveys

    Energy Technology Data Exchange (ETDEWEB)

    J. A. Chapman, A. J. Boerner, E. W. Abelquist

    2006-11-15

    In-situ, high-resolution gamma-ray spectrometry (ISGRS) measurements were conducted at the Oak Ridge Institute for Science and Education (ORISE) field laboratory in Oak Ridge, Tennessee. The purpose of these tests was to provide analytical data for assessing how “fit for use” this technology is for detecting discrete particles in soil.

  16. In situ deposition of graphene nanosheets on wood surface by one-pot hydrothermal method for enhanced UV-resistant ability

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Caichao, E-mail: wancaichaojy@163.com; Jiao, Yue, E-mail: yjiao123@126.com; Li, Jian, E-mail: lijiangroup@tom.com

    2015-08-30

    Graphical abstract: - Highlights: • The graphene/wood nanocomposites were fabricated via a mild fast one-pot hydrothermal method. • Graphene nanosheets were in situ deposited on the surface of the wood matrix. • The incorporation of graphene nanosheets results in the improvement in the thermal stability of the graphene/wood. • The graphene/wood exhibits superior UV resistance performance. - Abstract: Graphene nanosheets were successfully in situ deposited on the surface of the wood matrix via a mild fast one-pot hydrothermal method, and the resulting hybrid graphene/wood (GW) were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and thermogravimetric analysis (TGA). According to the results, the wood matrix was evenly coated by dense uninterrupted multilayer graphene membrane structure, which was formed by layer-by-layer self-assembly of graphene nanosheets. Meanwhile, the graphene coating also induced significant improvement in the thermal stability of GW in comparison with that of the original wood (OW). Accelerated weathering tests were employed to measure and determine the UV-resistant ability of OW and GW. After about six hundred hours of experiments, the surface color change of GW was much less than that of OW; besides, the Fourier transform infrared spectroscopy (FTIR) analysis also proved the less significant changes in surface chemical compositions of GW. The results both indicated that the graphene coating effectively protected wood surface from UV damage. Therefore, this class of GW composite might be expected to be served as high-performance wooden building material for outdoor or some particular harsh environments like strong UV radiation regions use.

  17. In situ reactivity and TOF-SIMS analysis of surfaces prepared by soft and reactive landing of mass-selected ions.

    Science.gov (United States)

    Johnson, Grant E; Lysonski, Michael; Laskin, Julia

    2010-07-01

    An instrument has been designed and constructed that enables in situ reactivity and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis of surfaces prepared or modified through soft and reactive landing of mass-selected polyatomic cations and anions. The apparatus employs an electrospray ion source coupled to a high transmission electrodynamic ion funnel, two focusing collision quadrupoles, a large 19 mm diameter quadrupole mass filter, and a quadrupole bender that deflects the ion beam, thereby preventing neutral contaminants from impinging on the deposition surface. The ion soft landing apparatus is coupled to a commercial TOF-SIMS instrument permitting the introduction of surfaces into vacuum and SIMS analysis before and after ion deposition without breaking vacuum. To facilitate a comparison of the current TOF-SIMS instrument with the in situ Fourier transform ion cyclotron resonance (FTICR-SIMS) deposition apparatus constructed previously, dications of the cyclic peptide Gramicidin S (GS) and the photoactive organonometallic complex ruthenium tris-bipyridine (Ru(bpy)(3)) were soft-landed onto fluorinated self-assembled monolayer (FSAM) on gold surfaces. In both cases, similarities and differences were observed in the secondary ion mass spectra, with the TOF-SIMS results, in general, characterized by greater sensitivity, larger dynamic range, less fragmentation, and fewer in-plume reactions than the corresponding FTICR-SIMS spectra. The charge reduction kinetics of both the doubly and singly protonated GS cations on the FSAM surface were also examined as was the influence of the primary gallium ion (Ga(+)) flux on the efficiency of these processes. In addition, we demonstrate that the new instrument enables detailed studies of the reactivity of catalytically active species immobilized by soft and reactive landing toward gaseous reagents.

  18. Highly reflective rear surface passivation design for ultra-thin Cu(In,Ga) Se-2 solar cells

    OpenAIRE

    Vermang, Bart; Timo Watjen, Jorn; Fjallstrom, Viktor; Rostvall, Fredrik; Edoff, Marika; Gunnarsson, Rickard; Pilch, Iris; Helmersson, Ulf; Kotipalli, Ratan; Henry, Frederic; Flandre, Denis

    2015-01-01

    Al2O3 rear surface passivated ultra-thin Cu(In,Ga)Se-2 (CIGS) solar cells with Mo nano-particles (NPs) as local rear contacts are developed to demonstrate their potential to improve optical confinement in ultra-thin CIGS solar cells. The CIGS absorber layer is 380 nm thick and the Mo NPs are deposited uniformly by an up-scalable technique and have typical diameters of 150 to 200 nm. The Al2O3 layer passivates the CIGS rear surface between the Mo NPs, while the rear CIGS interface in contact w...

  19. Characterization of Al2O3 as CIGS surface passivation layer in high-efficiency CIGS solar cells

    OpenAIRE

    Joel, Jonathan

    2014-01-01

    In this thesis, a novel method of reducing the rear surface recombination in copper indium gallium (di) selenide (CIGS) thin film solar cells, using atomic layer deposited (ALD) Al2O3, has been evaluated via qualitative opto-electrical characterization. The idea stems from the silicon (Si) industry, where rear surface passivation layers are used to boost the open-circuit voltage and, hence, the cell efficiency. To enable a qualitative assessment of the passivation effect, Al/Al2O3/CIGS metal-...

  20. Dual passivation of GaAs (110) surfaces using O{sub 2}/H{sub 2}O and trimethylaluminum

    Energy Technology Data Exchange (ETDEWEB)

    Kent, Tyler J.; Edmonds, Mary [Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093 (United States); Chagarov, Evgueni [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States); Droopad, Ravi [Department of Physics, Texas State University, San Marcos, Texas 78666 (United States); Kummel, Andrew C. [Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093 (United States); Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States)

    2013-12-28

    The nucleation and passivation of oxide deposition was studied on defect-free GaAs (110) surfaces to understand passivation of surfaces containing only III-V heterobonds. The passivation process on GaAs (110) was studied at the atomic level using scanning tunneling microscopy while the electronic structure was determined by scanning tunneling spectroscopy (STS). The bonding of the oxidant and reductant were modeled with density functional theory. To avoid Fermi level pinning during gate oxide atomic layer deposition, a dual passivation procedure was required using both a reductant, trimethylaluminum (TMA), and an oxidant, O{sub 2} or H{sub 2}O. Dosing GaAs (110) with TMA resulted in the formation of an ordered complete monolayer of dimethylaluminum which passivates the group V dangling bonds but also forms metal-metal bonds with conduction band edge states. These edge states were suppressed by dosing the surface with oxidants O{sub 2} or H{sub 2}O which selectively react with group III-aluminum bonds. The presence of an ordered Al monolayer with a high nucleation density was indirectly confirmed by XPS and STS.

  1. A spectroscopic method for the evaluation of surface passivation treatments on metal–oxide–semiconductor structures

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, Lee A., E-mail: lee.walsh36@mail.dcu.ie [School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland); Hurley, Paul K.; Lin, Jun [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Cockayne, Eric [National Institute of Standards and Technology, Gaithesburg, MD 20899 (United States); O’Regan, T.P. [U.S. Army Research Laboratory, Adelphi, MD 20783 (United States); Woicik, Joseph C. [National Institute of Standards and Technology, Gaithesburg, MD 20899 (United States); Hughes, Greg [School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland)

    2014-05-01

    Highlights: • Surface potential changes can be detected from HAXPES measurements. • Flat band voltage shifts can be detected from HAXPES measurements. • Agreement between HAXPES and C–V measurements in Si based MOS structures. • Agreement between HAXPES and C–V measurements in GaAs based MOS structures. - Abstract: Combined hard x-ray photoelectron spectroscopy (HAXPES) and electrical characterisation measurements have been shown to provide complementary information on the electrical performance of Si and GaAs based metal–oxide–semiconductor (MOS) structures. The results obtained indicate that surface potential changes at the semiconductor/dielectric interface due to the presence of different work function metals can be detected from HAXPES measurements. Changes in the semiconductor band bending at zero gate voltage and the flat band voltage values derived from C–V measurements are in agreement with the semiconductor core level shifts measured from the HAXPES spectra. These results highlight the potential application of this measurement approach in the evaluation of the efficacy of surface passivation treatments: HAXPES—hard x-ray photoelectron spectroscopy; C–V—capacitance voltage; D{sub it}—interface state density; BE—binding energy, at reducing defect states densities in MOS structures.

  2. Passivation of the surface of aluminum nanopowders by protective coatings of the different chemical origin

    Science.gov (United States)

    Kwon, Young-Soon; Gromov, Alexander A.; Strokova, Julia I.

    2007-04-01

    The results of investigation and analysis of electro-exploded aluminum nanopowders, whose surface were passivated with the following substances: liquids - nitrocellulose (NC), oleic acid (C 17H 33COOH) and stearic acid (C 17H 35COOH), suspended in kerosene and ethanol, fluoropolymer; solids - boron and nickel; gases - N 2, CO 2 and air (for a comparison) are discussed. The surface protection for the aluminum nanopowders by coatings of different chemical origins leads to the some advantages of the powders properties for an application in energetic systems, e.g. solid propellants and "green" propellants (Al-H 2O). Aluminum nanopowders with a protected surface showed the increased stability to oxidation in air during the storage period and higher reactivity by heating. The TEM-visual diagram of the formation and stabilization of the coatings on the particles has been proposed on the basis of experimental results. The kinetics of the interaction of aluminum nanopowders with air has been discussed. The recommendations concerning an efficiency of the protective "non-Al 2O 3" layers on aluminum nanoparticles were proposed.

  3. Colossal positive magnetoresistance in surface-passivated oxygen-deficient strontium titanite

    KAUST Repository

    David, Adrian

    2015-05-15

    Modulation of resistance by an external magnetic field, i.e. magnetoresistance effect, has been a long-lived theme of research due to both fundamental science and device applications. Here we report colossal positive magnetoresistance (CPMR) (>30,000% at a temperature of 2 K and a magnetic field of 9 T) discovered in degenerate semiconducting strontium titanite (SrTiO3) single crystals capped with ultrathin SrTiO3/LaAlO3 bilayers. The low-pressure high-temperature homoepitaxial growth of several unit cells of SrTiO3 introduces oxygen vacancies and high-mobility carriers in the bulk SrTiO3, and the three-unit-cell LaAlO3 capping layer passivates the surface and improves carrier mobility by suppressing surface-defect-related scattering. The coexistence of multiple types of carriers and inhomogeneous transport lead to the emergence of CPMR. This unit-cell-level surface engineering approach is promising to be generalized to others oxides, and to realize devices with high-mobility carriers and interesting magnetoelectronic properties.

  4. In situ surface treatment of nanocrystalline MFe{sub 2}O{sub 4} (M = Co, Mg, Mn, Ni) spinel ferrites using linseed oil

    Energy Technology Data Exchange (ETDEWEB)

    Gherca, Daniel, E-mail: daniel_gherca@yahoo.com [Faculty of Chemistry, “Alexandru Ioan Cuza” University from Iasi, Bd. Carol I nr 11, Iasi 700506 (Romania); Cornei, Nicoleta [Faculty of Chemistry, “Alexandru Ioan Cuza” University from Iasi, Bd. Carol I nr 11, Iasi 700506 (Romania); Mentré, Olivier; Kabbour, Houria; Daviero-Minaud, Sylvie [Université Lille Nord de France, CNRS UMR8181, Unité de Catalyse et de Chimie du Solide, UCCS ENSCL/USTL, F-59655 Villeneuve d’Ascq (France); Pui, Aurel, E-mail: aurel@uaic.ro [Faculty of Chemistry, “Alexandru Ioan Cuza” University from Iasi, Bd. Carol I nr 11, Iasi 700506 (Romania)

    2013-12-15

    This paper reports the synthesis by coprecipitation method of MFe{sub 2}O{sub 4} nanoparticles using linseed oil as the in-situ surfactant. The decomposition process of the precursors and the formation process of MFe{sub 2}O{sub 4} were investigated by thermogravimetric analysis and differential thermal analysis (TG-DTA). The crystal structure and surface morphology were examined by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis. The results demonstrate that the surface of MFe{sub 2}O{sub 4} with a diameter in the range 5–13 nm, is activated with hydrophilic groups of the surfactant which coat them and enhance the stability. Magnetic properties are discussed.

  5. A suitable for large scale production, flexible and transparent surface-enhanced Raman scattering substrate for in situ ultrasensitive analysis of chemistry reagents

    Science.gov (United States)

    Chen, P. X.; Shang, S. B.; Hu, L. T.; Liu, X. Y.; Qiu, H. W.; Li, C. H.; Huo, Y. Y.; Jiang, S. Z.; Yang, C.

    2016-09-01

    In this paper, a high cost-performance surface-enhanced Raman scattering (SERS) flexible substrate is demonstrated, which endowed with excellent optical transparency, high SERS activity and large scale. This SERS flexible substrate of Ag/Cu/Polyethylene Terephthalate (PET) was prepared by replacing Cu atoms with Ag atoms in situ on Cu nano-film. The Ag/Cu/PET flexible substrate shows high sensitivity in SERS detection and the minimum detected concentration of R6G can reach 10-10 M. In addition, the residual methylene blue (MB) on a fish surface was selected as the analyte, the results no doubt shows the potential of SERS technology application in food detection.

  6. Research and development of photovoltaic power system. Research on surface passivation for high-efficiency silicon solar cells; Taiyoko hatsuden system no kenkyu kaihatsu. Hyomen passivation no kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Saito, T. [Tokyo Univ. of Agriculture and Technology, Tokyo (Japan). Faculty of Technology

    1994-12-01

    This paper reports the result obtained during fiscal 1994 on research on surface passivation of high-efficiency silicon solar cells. In research on carrier recombination on SiO2/doped silicon interface, measurements were carried out on minority carrier life with respect to p-type silicon substrates with which phosphorus with high and low concentrations are diffused uniformly on the surface and non-uniformly on the back and then oxidized. The measurements were performed for the purpose of evaluating the carrier recombination at p-n junctions. Effective life time of oxidized test samples increased longer than that of prior to the oxidization as a result of effect of surface passivation contributing remarkably. In research on reduction in carrier recombination on SiO2/Si interface by using H radical annealing, experiments were conducted by using a method that uses more active H-atoms. As a result, it was revealed that the reduction effect is recognized at as low temperature as 200{degree}C, and photo-bias effect is also noticeable. Other research activities included analytic research on minority carrier recombination on micro crystalline silicon/crystalline silicon interface, and experimental research on evaluation of minority carrier life of poly-crystalline silicon wafers. 6 figs.

  7. A synergetic effect of surface texture and field-effect passivations on improving Si solar cell performance

    Science.gov (United States)

    Qiu, Ying; Wang, Liangxing; Hao, Hongchen; Shi, Wei; Lu, Ming

    2015-07-01

    P-type Si substrate based solar cells were prepared with indium-tin-oxide thin films as the front top electrodes and Al layers as the rear ones. A synergetic effect of surface texture and field-effect passivations on improving Si solar cell performance was investigated. The surface texture was conducted by NaOH etching of Si, and field-effect passivations were performed by introducing SiO2 and Al2O3 thin film layers at the front and rear sides of the Si solar cell, respectively. The surface texture treatment makes the Si solar cell efficiency increase from 9.81% to 11.08%. After the synergetic treatments of surface texture and field-effect passivations, the efficiency further increased to 15.04%, that is, a more than 50% relative efficiency enhancement was obtained. This work demonstrates the significant effectiveness and facile applicability of the synergetic effect of surface texture and field-effect passivations on improving Si solar cell performance.

  8. Improved discharge capacity and suppressed surface passivation of zinc anode in dilute alkaline solution using surfactant additives

    Science.gov (United States)

    Yang, Hanxi; Cao, Yuliang; Ai, Xinping; Xiao, Lifen

    The capacity utilization of zinc anode is usually very low in dilute alkaline solution or at high rate discharge because of the passivation of zinc surface. This problem can be considerably overcome by use of surfactant additive in electrolyte. In this work, it is found that with addition of 2% sodium dodecyl benzene sulfonate (SDBS) in 20% KOH solution, the discharge capacity of zinc anode increases from 360 to 490 mAh/g at moderate discharge rate of 40 mA/g, corresponding to a 35% increase in the capacity utilization. Based on the electrochemical and morphological observation of the anodic passivation behaviors of zinc electrode, this effect is revealed that due to the SDBS adsorption, the passive layer formed on the zinc surface has a loose and porous structure rather than a dense and compact film. This type of surface layer facilitates the diffusive exchange of the solution reactant and discharged product through the surface deposit layer and therefore effectively suppresses the surface passivation of zinc anode.

  9. Surface and Atmospheric Contributions to Passive Microwave Brightness Temperatures for Falling Snow Events

    Science.gov (United States)

    Skofronick-Jackson, Gail; Johnson, Benjamin T.

    2011-01-01

    Physically based passive microwave precipitation retrieval algorithms require a set of relationships between satellite -observed brightness temperatures (TBs) and the physical state of the underlying atmosphere and surface. These relationships are nonlinear, such that inversions are ill ]posed especially over variable land surfaces. In order to elucidate these relationships, this work presents a theoretical analysis using TB weighting functions to quantify the percentage influence of the TB resulting from absorption, emission, and/or reflection from the surface, as well as from frozen hydrometeors in clouds, from atmospheric water vapor, and from other contributors. The percentage analysis was also compared to Jacobians. The results are presented for frequencies from 10 to 874 GHz, for individual snow profiles, and for averages over three cloud-resolving model simulations of falling snow. The bulk structure (e.g., ice water path and cloud depth) of the underlying cloud scene was found to affect the resultant TB and percentages, producing different values for blizzard, lake effect, and synoptic snow events. The slant path at a 53 viewing angle increases the hydrometeor contributions relative to nadir viewing channels. Jacobians provide the magnitude and direction of change in the TB values due to a change in the underlying scene; however, the percentage analysis provides detailed information on how that change affected contributions to the TB from the surface, hydrometeors, and water vapor. The TB percentage information presented in this paper provides information about the relative contributions to the TB and supplies key pieces of information required to develop and improve precipitation retrievals over land surfaces.

  10. Bayesian modeling of perceived surface slant from actively-generated and passively-observed optic flow.

    Directory of Open Access Journals (Sweden)

    Corrado Caudek

    Full Text Available We measured perceived depth from the optic flow (a when showing a stationary physical or virtual object to observers who moved their head at a normal or slower speed, and (b when simulating the same optic flow on a computer and presenting it to stationary observers. Our results show that perceived surface slant is systematically distorted, for both the active and the passive viewing of physical or virtual surfaces. These distortions are modulated by head translation speed, with perceived slant increasing directly with the local velocity gradient of the optic flow. This empirical result allows us to determine the relative merits of two alternative approaches aimed at explaining perceived surface slant in active vision: an "inverse optics" model that takes head motion information into account, and a probabilistic model that ignores extra-retinal signals. We compare these two approaches within the framework of the bayesian theory. The "inverse optics" bayesian model produces veridical slant estimates if the optic flow and the head translation velocity are measured with no error; because of the influence of a "prior" for flatness, the slant estimates become systematically biased as the measurement errors increase. The bayesian model, which ignores the observer's motion, always produces distorted estimates of surface slant. Interestingly, the predictions of this second model, not those of the first one, are consistent with our empirical findings. The present results suggest that (a in active vision perceived surface slant may be the product of probabilistic processes which do not guarantee the correct solution, and (b extra-retinal signals may be mainly used for a better measurement of retinal information.

  11. Effect of surface passivation on corrosion resistance and antibacterial properties of Cu-bearing 316L stainless steel

    Science.gov (United States)

    Zhao, Jinlong; Xu, Dake; Shahzad, M. Babar; Kang, Qiang; Sun, Ying; Sun, Ziqing; Zhang, Shuyuan; Ren, Ling; Yang, Chunguang; Yang, Ke

    2016-11-01

    The resistance for pitting corrosion, passive film stability and antibacterial performance of 316L-Cu SS passivated by nitric acid solution containing certain concentration of copper sulfate, were studied by electrochemical cyclic polarization, electrochemical impedance spectroscopy (EIS) and co-culture with bacteria. Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the Cu2+ ions release from 316L-Cu SS surface. XPS analysis proved that the enrichment of CuO, Cr2O3 and Cr(OH)3 on the surface of specimen could simultaneously guarantee a better corrosion resistance and stable antibacterial properties. The biocompatibility evaluation determined by RTCA assay also indicated that the 316L-Cu SS after antibacterial passivation was completely biocompatible.

  12. Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

    2016-01-01

    Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface...... for TiO2 deposition, a three-step cleaning procedure was introduced after RIE etching. The morphology of anatase TiO2 indicates that the nano-textured substrate has a much higher surface nucleated grain density than a flat substrate at the beginning of the deposition process. The corresponding...... reflectance increases with TiO2 thickness due to increased surface diffuse reflection. The passivation effect of ALD TiO2 thin film on the nano-textured fluorescent 6H-SiC sample was also investigated and a PL intensity improvement of 8.05% was obtained due to the surface passivation....

  13. Influence of different light-curing units on the surface roughness of restorative materials: in situ study

    Directory of Open Access Journals (Sweden)

    Juliane Cristina Ciccone-Nogueira

    2007-09-01

    Full Text Available The aim of this study was to evaluate the influence of different light sources (LED and Halogen lamp on the roughness (superficial of composite resin (Filtek Z250, Filtek P60, Charisma and Durafill varying post-irradiation times, in an in situ experiment. For this purpose, 80 specimens were made in polyurethane moulds. Ten volunteers without medicament use and good oral condition were selected and from them study moulds were obtained. A palatal intra-oral acrylic resin appliance was made for each of the subjects of the experiment. In each appliance, two specimens of each material were fixed (LED/Halogen lamp - control group. Roughness tests were performed immediately and 30 days after initial light-curing. Statistical analysis was performed using ANOVA. Statistically significant difference was observed only between post-irradiation times, where the 30th day showed the highest roughness values. It be concluded that roughness was influenced only by post-irradiation times, presenting the 30- days period inferior behavior.

  14. In-Situ ATR-FTIR and Surface Complexation Modeling Study of the Adsorption of Dimethylarsenic Acid and p-Arsanilic Acid on Iron Oxides

    Science.gov (United States)

    Goldberg, S. R.; Al-Abadleh, H.; Mitchell, W.

    2010-12-01

    Arsenic is an element that exists naturally in many rocks and minerals around the world, accumulates in petroleum, shale, and coal deposits as a result of biogeochemical processes, and is found in fly ash from fuel combustion. Arsenic compounds in their organic and inorganic forms pose both health and environmental risks. The environmental fate of arsenic compounds is controlled to a large extent by their surface interactions with inorganic and organic surfaces. We report results from applying the triple layer surface complexation model to adsorption isotherm and pH-envelope experimental data of dimethylarsenic acid, DMA, and p-arsanilic acid, p-AsA on the iron oxides, hematite and goethite. Ligand exchange reactions were based on the interpretation of ATR-FTIR spectra of DMA and p-AsA surface complexes. Surface coverage of the organoarsenicals was quantified in-situ from the spectral component at 840 cm-1. The best model fit to the DMA adsorption data was obtained using an outer-sphere complex, whereas for p-AsA, best model fit was obtained using two monodentate inner-sphere surface complexes. The significance of the results is discussed in relation to improving modeling tools used by environmental regulators. Accurate predictive modeling tools are needed for effective design of arsenic removal technologies using iron oxide minerals.

  15. Incorporation of low energy activated nitrogen onto HOPG surface: Chemical states and thermal stability studies by in-situ XPS and Raman spectroscopy

    Science.gov (United States)

    Chandran, Maneesh; Shasha, Michal; Michaelson, Shaul; Hoffman, Alon

    2016-09-01

    In this paper we report the chemical states analysis of activated nitrogen incorporated highly oriented pyrolytic graphite (HOPG) surface under well-controlled conditions. Nitrogen incorporation is carried out by two different processes: an indirect RF nitrogen plasma and low energy (1 keV) N2+ implantation. Bonding configuration, concentration and thermal stability of the incorporated nitrogen species by aforesaid processes are systematically compared by in-situ X-ray photoelectron spectroscopy (XPS). Relatively large concentration of nitrogen is incorporated onto RF nitride HOPG surface (16.2 at.%), compared to N2+ implanted HOPG surface (7.7 at.%). The evolution of N 1s components (N1, N2, N3) with annealing temperature is comprehensively discussed, which indicates that the formation and reorganization of local chemical bonding states are determined by the process of nitridation and not by the prior chemical conditioning (i.e., amorphization or hydrogenation) of the HOPG surface. A combined XPS and Raman spectroscopy studies revealed that N2+ implantation process resulted in a high level of defects to the HOPG surface, which cannot be annealed-out by heat treatment up to 1000 °C. On the other hand, the RF nitrogen plasma process did not produce a high level of surface defects, while incorporating nearly the same amount of stable nitrogen species.

  16. Immobilization of serum albumin and peptide aptamer for EPC on polydopamine coated titanium surface for enhanced in-situ self-endothelialization.

    Science.gov (United States)

    Chen, Zhuoyue; Li, Quanli; Chen, Jialong; Luo, Rifang; Maitz, Manfred F; Huang, Nan

    2016-03-01

    Restenosis and thrombosis are two major complications associated with vascular stents and grafts. The homing of circulating endothelial progenitor cells (EPCs) onto implant surfaces brings a new strategy to solve these problems by accelerating self -endothelialization in situ. Peptide aptamers with high affinity and specific recognition of EPCs can be immobilized to capture EPCs from the circulating blood. In this study, a biotinylated peptide aptamer (TPSLEQRTVYAK-GGGC-K-Biotin) for EPC, and bovine serum albumin (BSA) were co-immobilized onto titanium surface through avidin-biotin recognition to endow the surface with specific affinity for EPC and anti-platelet adhesion properties. Quartz crystal microbalance with dissipation (QCM-D), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and water contact angle measuring were adopted for coating characterization. EPC affinity and hemocompatibility of the coating were also investigated in vitro. The results demonstrated that aptamer and BSA co-immobilized surface significantly reduced platelet adhesion and fibrinogen adsorption/activation. Besides, such functional surface could remarkably enhance EPC adhesion, without affecting the behavior of endothelial cells (ECs) and smooth muscle cells (SMCs) obviously. The result shows the possibility of utilizing such a multifunctional surface in cardiovascular implants. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Effect of ozone concentration on silicon surface passivation by atomic layer deposited Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Gastrow, Guillaume von, E-mail: guillaume.von.gastrow@aalto.fi [Aalto University, Department of Micro- and Nanosciences, Tietotie 3, 02150 Espoo (Finland); Li, Shuo [Aalto University, Department of Micro- and Nanosciences, Tietotie 3, 02150 Espoo (Finland); Putkonen, Matti [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Espoo (Finland); Aalto University School of Chemical Technology, Laboratory of Inorganic Chemistry, FI-00076 Aalto, Espoo (Finland); Laitinen, Mikko; Sajavaara, Timo [University of Jyvaskyla, Department of Physics, FIN-40014 University of Jyvaskyla (Finland); Savin, Hele [Aalto University, Department of Micro- and Nanosciences, Tietotie 3, 02150 Espoo (Finland)

    2015-12-01

    Highlights: • The ALD Al{sub 2}O{sub 3} passivation quality can be controlled by the ozone concentration. • Ozone concentration affects the Si/Al{sub 2}O{sub 3} interface charge and defect density. • A surface recombination velocity of 7 cm/s is reached combining ozone and water ALD. • Carbon and hydrogen concentrations correlate with the surface passivation quality. - Abstract: We study the impact of ozone-based Al{sub 2}O{sub 3} Atomic Layer Deposition (ALD) on the surface passivation quality of crystalline silicon. We show that the passivation quality strongly depends on the ozone concentration: the higher ozone concentration results in lower interface defect density and thereby improved passivation. In contrast to previous studies, our results reveal that too high interface hydrogen content can be detrimental to the passivation. The interface hydrogen concentration can be optimized by the ozone-based process; however, the use of pure ozone increases the harmful carbon concentration in the film. Here we demonstrate that low carbon and optimal hydrogen concentration can be achieved by a single process combining the water- and ozone-based reactions. This process results in an interface defect density of 2 × 10{sup 11} eV{sup −1} cm{sup −2}, and maximum surface recombination velocities of 7.1 cm/s and 10 cm/s, after annealing and after an additional firing at 800 °C, respectively. In addition, our results suggest that the effective oxide charge density can be optimized in a simple way by varying the ozone concentration and by injecting water to the ozone process.

  18. Surface Engineering for Bone Implants: A Trend from Passive to Active Surfaces

    Directory of Open Access Journals (Sweden)

    John Jansen

    2012-07-01

    Full Text Available The mechanical and biological properties of bone implants need to be optimal to form a quick and firm connection with the surrounding environment in load bearing applications. Bone is a connective tissue composed of an organic collagenous matrix, a fine dispersion of reinforcing inorganic (calcium phosphate nanocrystals, and bone-forming and -degrading cells. These different components have a synergistic and hierarchical structure that renders bone tissue properties unique in terms of hardness, flexibility and regenerative capacity. Metallic and polymeric materials offer mechanical strength and/or resilience that are required to simulate bone tissue in load-bearing applications in terms of maximum load, bending and fatigue strength. Nevertheless, the interaction between devices and the surrounding tissue at the implant interface is essential for success or failure of implants. In that respect, coatings can be applied to facilitate the process of bone healing and obtain a continuous transition from living tissue to the synthetic implant. Compounds that are inspired by inorganic (e.g., hydroxyapatite crystals or organic (e.g., collagen, extracellular matrix components, enzymes components of bone tissue, are the most obvious candidates for application as implant coating to improve the performance of bone implants. This review provides an overview of recent trends and strategies in surface engineering that are currently investigated to improve the biological performance of bone implants in terms of functionality and biological efficacy.

  19. The Ehrlich-Schwoebel barrier on an oxide surface: a combined Monte-Carlo and in situ scanning tunneling microscopy approach

    Science.gov (United States)

    Gianfrancesco, Anthony G.; Tselev, Alexander; Baddorf, Arthur P.; Kalinin, Sergei V.; Vasudevan, Rama K.

    2015-11-01

    The controlled growth of epitaxial films of complex oxides requires an atomistic understanding of key parameters determining final film morphology, such as termination dependence on adatom diffusion, and height of the Ehrlich-Schwoebel (ES) barrier. Here, through an in situ scanning tunneling microscopy study of mixed-terminated La5/8Ca3/8MnO3 (LCMO) films, we image adatoms and observe pile-up at island edges. Image analysis allows determination of the population of adatoms at the edge of islands and fractions on A-site and B-site terminations. A simple Monte-Carlo model, simulating the random walk of adatoms on a sinusoidal potential landscape using Boltzmann statistics is used to reproduce the experimental data, and provides an estimate of the ES barrier as ˜0.18 ± 0.04 eV at T = 1023 K, similar to those of metal adatoms on metallic surfaces. These studies highlight the utility of in situ imaging, in combination with basic Monte-Carlo methods, in elucidating the factors which control the final film growth in complex oxides.

  20. Phosphate adsorption onto hematite: an in situ ATR-FTIR investigation of the effects of pH and loading level on the mode of phosphate surface complexation.

    Science.gov (United States)

    Elzinga, Evert J; Sparks, Donald L

    2007-04-01

    Phosphate adsorption on hematite was characterized as a function of pH (3.5-8.9) and phosphate concentration (5-500 microM) by in situ ATR-FTIR spectroscopy. Under most conditions a mixture of different (inner-sphere) phosphate complexes existed at the hematite surface, with the relative importance of these complexes varying with pH and surface coverage. Experiments using D(2)O and H(2)O indicated the presence of two protonated phosphate surface complexes at pH/pD=3.5-7.0. Comparison to spectra of protonated aqueous phosphate species suggested that these surface complexes are monoprotonated. The difference in the IR spectra of these complexes is tentatively interpreted to result from a different surface coordination, with one surface complex coordinated in a monodentate binuclear (bridging) fashion, and the second as a monodentate mononuclear complex. Alternatively, the bridging complex may be a (protonated) monodentate mononuclear complex exhibiting strong hydrogen bonding to an adjacent surface site, and the second species a monodentate complex exhibiting limited hydrogen bonding. Formation of the bridging complex is favored at lower pH values and higher surface loadings in the 3.5-7.0 pH range. At the highest pH values studied (8.5-9.0) a third complex, interpreted to be a nonprotonated monodentate mononuclear complex, is present along with the monodentate monoprotonated surface species. The importance of the nonprotonated monodentate complex increases with increasing surface coverage at these high pH values.

  1. Antibacterial performance of polydopamine-modified polymer surfaces containing passive and active components.

    Science.gov (United States)

    Sileika, Tadas S; Kim, Hyung-Do; Maniak, Piotr; Messersmith, Phillip B

    2011-12-01

    A growing number of device-related nosocomial infections, elevated hospitalization costs, and patient morbidity necessitate the development of novel antibacterial strategies for clinical devices. We have previously demonstrated a simple, aqueous polydopamine dip-coating method to functionalize surfaces for a wide variety of uses. Here, we extend this strategy with the goal of imparting antifouling and antimicrobial properties to substrates, exploiting the ability of polydopamine to immobilize polymers and induce metal nanoparticle formation. Polydopamine was deposited as a thin adherent film of 4 nm thickness from alkaline aqueous solution onto polycarbonate substrates, followed by grafting of antifouling polymer polyethylene glycol and in situ deposition of silver nanoparticles onto the polydopamine coated polycarbonate substrates. Elemental and morphological surface analyses confirmed successful grafting of polyethylene glycol brushes onto polydopamine-coated substrates, as well as spontaneous silver nanoparticle formation for polydopamine-coated substrates incubated in silver-nitrate solutions. Sustained silver release was observed over at least 7 days from silver-coated substrates, and the release kinetics could be modulated via additional polydopamine overlayers. In vitro functional assays employing gram negative and positive strains demonstrated dual fouling resistance and antibacterial properties of the coatings due to the fouling resistance of grafted polyethylene glycol and antibacterial effect of silver, respectively. Polycarbonate substrates coated only with silver using a method similar to existing commercial coatings provided an antibacterial effect but failed to inhibit bacterial attachment. Taking into account the previously demonstrated substrate versatility of polydopamine coatings, our findings suggest that this strategy could be implemented on a variety of substrate materials to simultaneously improve antifouling and antimicrobial performance.

  2. In situ STM imaging and direct electrochemistry of Pyrococcus furiosus ferredoxin assembled on thiolate-modified Au(111) surfaces

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Christensen, Hans Erik Mølager; Ooi, Bee Lean

    2004-01-01

    We have addressed here electron transfer (ET) of Pyrococcus furiosus ferredoxin (PfFd, 7.5 kDa) in both homogeneous solution using edge plane graphite (EPG) electrodes and in the adsorbed state by electrochemistry on surface-modified single-crystal Au(111) electrodes, This has been supported...... surface modified by the same functional group monolayer and to address diffusionless direct electrochemistry, as well as surface microstructures of the protein monolayer. PfFd molecules were found to assemble on either mercaptopropionic acid (MPA) or cysteine-modified Au(111) surfaces in stable monolayers...

  3. Preparation, characterization and dissolution of passive oxide film on the 400 series stainless steel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sathyaseelan, V.S.; Rufus, A.L.; Chandramohan, P.; Subramanian, H.; Velmurugan, S., E-mail: svelu@igcar.gov.in

    2015-12-15

    Full system decontamination of Primary Heat Transport (PHT) system of Pressurised Heavy Water Reactors (PHWRs) resulted in low decontamination factors (DF) on stainless steel (SS) surfaces. Hence, studies were carried out with 403 SS and 410 SS that are the material of construction of “End-Fitting body” and “End-Fitting Liner tubes”. Three formulations were evaluated for the dissolution of passive films formed over these alloys viz., i) Two-step process consisting of oxidation and reduction reactions, ii) Dilute Chemical Decontamination (DCD) and iii) High Temperature Process. The two-step and high temperature processes could dissolve the oxide completely while the DCD process could remove only 60%. Various techniques like XRD, Raman spectroscopy and SEM-EDX were used for assessing the dissolution process. The two-step process is time consuming, laborious while the high temperature process is less time consuming and is recommended for SS decontamination. - Graphical abstract: SEM micrograph of the oxide film formed in an autoclave over the 403 SS and 410 SS surfaces, the “End-Fitting Body and End-Fitting Liner” materials of Pressurized Heavy Water Reactor (PHWR). - Highlights: • The oxides formed over 403 and 410 SS are spinels similar to magnetite. • Oxide is duplex in nature with chromium rich inner layer. • Dilute Chemical Decontamination process could dissolve only 60% of the oxide. • Oxidation-Reduction process dissolves 100% oxide layer but time consuming. • High Temperature process is 100% efficient and less time consuming.

  4. Surface Passivation of Ti/4H-SiC Schottky Barrier Diode

    Institute of Scientific and Technical Information of China (English)

    Muhammad Khalid; Saira Riaz; Shahzad Naseem

    2012-01-01

    Surface properties of SiC power devices mostly depend on the passivation layer (PL).This layer has direct influence on electrical characteristics of devices.2D numerical simulation of forward and reverse characteristics with and without different (PLs) (SiO2,HfO2 and Si3N4) has been performed.Simulation results show that the breakdown voltage increases with increasing PL thickness,and there is a lesser significant effect on forward characteristics.The maximum breakdown voltage with and without SiO2 PL is 1240 V and 276 V,respectively.SiO2 PL has compatibility with SiC surface providing high breakdown voltage,6 and 8% higher than that of HfO2 and Si3N4 respectively.Low leakage current is observed which then further decreases on reducing the thickness of PL.Furthermore,variation of forward current with dielectric constant and thickness of PLs was observed.Finally,it is suggested that matches of our results with published experimental results indicate that the Sentaurus TCAD simulator is a predictive tool for the SiC Schottky barrier diode simulation.

  5. Passive wireless surface acoustic wave sensors for monitoring sequestration sites CO2 emission

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yizhong [Univ. of Pittsburgh, PA (United States); Chyu, Minking [Univ. of Pittsburgh, PA (United States); Wang, Qing-Ming [Univ. of Pittsburgh, PA (United States)

    2013-02-14

    University of Pittsburgh’s Transducer lab has teamed with the U.S. Department of Energy’s National Energy Technology Laboratory (DOE NETL) to conduct a comprehensive study to develop/evaluate low-cost, efficient CO2 measuring technologies for geological sequestration sites leakage monitoring. A passive wireless CO2 sensing system based on surface acoustic wave technology and carbon nanotube nanocomposite was developed. Surface acoustic wave device was studied to determine the optimum parameters. Delay line structure was adopted as basic sensor structure. CNT polymer nanocomposite was fabricated and tested under different temperature and strain condition for natural environment impact evaluation. Nanocomposite resistance increased for 5 times under pure strain, while the temperature dependence of resistance for CNT solely was -1375ppm/°C. The overall effect of temperature on nanocomposite resistance was -1000ppm/°C. The gas response of the nanocomposite was about 10% resistance increase under pure CO2 . The sensor frequency change was around 300ppm for pure CO2 . With paralyne packaging, the sensor frequency change from relative humidity of 0% to 100% at room temperature decreased from over 1000ppm to less than 100ppm. The lowest detection limit of the sensor is 1% gas concentration, with 36ppm frequency change. Wireless module was tested and showed over one foot transmission distance at preferred parallel orientation.

  6. High reduction of interfacial charge recombination in colloidal quantum dot solar cells by metal oxide surface passivation.

    Science.gov (United States)

    Chang, Jin; Kuga, Yuki; Mora-Seró, Iván; Toyoda, Taro; Ogomi, Yuhei; Hayase, Shuzi; Bisquert, Juan; Shen, Qing

    2015-03-12

    Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar cells (CQDSCs). By coating thin TiO2 layers onto ZnO-NW surfaces, the open-circuit voltage and power conversion efficiency have been improved by over 40% in PbS CQDSCs. Characterization by transient photovoltage decay and impedance spectroscopy indicated that the interfacial recombination was significantly reduced by the surface passivation strategy. An efficiency as high as 6.13% was achieved through the passivation approach and optimization for the length of the ZnO-NW arrays (device active area: 16 mm2). All solar cells were tested in air, and exhibited excellent air storage stability (without any performance decline over more than 130 days). This work highlights the significance of metal oxide passivation in achieving high performance BHJ solar cells. The charge recombination mechanism uncovered in this work could shed light on the further improvement of PbS CQDSCs and/or other types of solar cells.

  7. Spatial and Temporal Variations of Surface Characteristics on the Greenland Ice Sheet as Derived from Passive Microwave Observations

    Science.gov (United States)

    Anderson, Mark; Rowe, Clinton; Kuivinen, Karl; Mote, Thomas

    1996-01-01

    The primary goals of this research were to