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Sample records for ii oxide aerogels

  1. Aerogels: II. Applications in catalysis

    Directory of Open Access Journals (Sweden)

    Orlović Aleksandar M.

    2002-01-01

    Full Text Available Sol-gel synthesis, and the resulting materials (xerogels and aerogels are finding increasing application in the synthesis of catalysts, due to their unique characteristics. The most important features of the sol-gel process are: the ability to achieve homogeneity at the molecular level, the introduction of several species in only one step and the ability to stabilize metastable phases. The supercritical drying process produces aerogels with structural features quite different to conventional materials. Some of these characteristics of aerogels can make them very effective catalysts.

  2. Carbon aerogels by pyrolysis of TEMPO-oxidized cellulose

    Science.gov (United States)

    Zhang, Sizhao; Feng, Jian; Feng, Junzong; Jiang, Yonggang; Ding, Feng

    2018-05-01

    Although carbon aerogels derived from naturally occurring materials have been developed extensively, a reasonable synthetic approach using cellulose-resource remains unclear. Here, we report a strategy to prepare carbon aerogels originated from cellulose position-selectively oxidized by TEMPO-oxidized process. Contrary to non-TEMPO-oxidized cellulose-derived carbon aerogels (NCCA) with relative loose structure, TEMPO-oxidized cellulose-derived carbon aerogels (TCCA) with tight fibrillar-continuous network are monitored, suggesting the importance of TEMPO-oxidized modification towards creating the architecture of subsequently produced carbon aerogels. TCCA endows a higher BET area despite owning slightly dense bulk density comparing with that of NCCA. The structural texture of TCCA could be maintained in a way in comparison to TEMPO-oxidized cellulose-derived aerogel, due to the integration and aggregation effect by losing the electric double layer repulsion via ionization of the surface carboxyl groups. FTIR and XPS analyses signify the evidence of non-functionalized carbon-skeleton network formation in terms of TCCA. Further, the mechanism concerning the creation of carbon aerogels is also established. These findings not only provide new insights into the production of carbon aerogels but also open up a new opportunity in the field of functional carbon materials.

  3. Multifunctional Aerogel Thermal Protection Systems for Hypersonic Vehicles, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective of the Phase II project is to develop lightweight reinforced aerogel materials for use as the core structural insulation material in...

  4. Highly porous ceramic oxide aerogels having improved flexibility

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor); Guo, Haiquan (Inventor)

    2012-01-01

    Ceramic oxide aerogels having improved flexibility are disclosed. Preferred embodiments exhibit high modulus and other strength properties despite their improved flexibility. The gels may be polymer cross-linked via organic polymer chains to further improve strength properties, without substantially detracting from the improved flexibility. Methods of making such aerogels are also disclosed.

  5. Aerogel

    Indian Academy of Sciences (India)

    Aerogel, a material not much denser than air on a foggy morning ... between a liquid and a gas, leading to minimum effect on surface ... approached by the French Government to design a method to ... catalysts. • Aerogel dust in grain and seed stocks was found to kill insects by mere ... radiation detectors in nuclear reactors.

  6. Aerogel RICH for the Belle II forward PID

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, S., E-mail: shohei.nishida@kek.jp [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Adachi, I. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Hamada, N. [Toho University, Funabashi (Japan); Hara, K. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Iijima, T. [Nagoya University, Nagoya (Japan); Iwata, S.; Kakuno, H. [Tokyo Metropolitan University, Hachioji (Japan); Kawai, H. [Chiba University, Chiba (Japan); Korpar, S.; Krizan, P. [Jozef Stefan Institute, Ljubljana (Slovenia); Ogawa, S. [Toho University, Funabashi (Japan); Pestotnik, R.; Ŝantelj, L.; Seljak, A. [Jozef Stefan Institute, Ljubljana (Slovenia); Sumiyoshi, T. [Tokyo Metropolitan University, Hachioji (Japan); Tabata, M. [Japan Aerospace Exploration Agency (JAXA), Sagamihara (Japan); Tahirovic, E. [Jozef Stefan Institute, Ljubljana (Slovenia); Yoshida, K. [Tokyo Metropolitan University, Hachioji (Japan); Yusa, Y. [Niigata University, Niigata (Japan)

    2014-12-01

    The Belle II spectrometer, a follow up of the very successful Belle experiment, is under construction at the SuperKEKB electron–positron collider at KEK in Japan. For the PID system in the forward region of the spectrometer, a proximity focusing ring-imaging Cherenkov (RICH) counter with an aerogel radiator is being developed. The counter will provide a 4σ separation of pions and kaons up to momenta of 4 GeV/c. For the position sensitive photon sensor, a 144-channel Hybrid Avalanche Photo-Detector (HAPD) has been developed with Hamamatsu Photonics K.K. The readout electronics is based on the custom developed ASIC. The design of the components is currently being finalized and part of their mass production have already started. Herein, we report the final design of the counter and a prototype test conducted with test beams at DESY. - Highlights: • We are constructing a RICH counter with aerogel radiator for Belle II. • Beam test for the prototype Aerogel RICH shows its good performance. • The effect of the neutron irradiation of the photodetector is examined.

  7. Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

    DEFF Research Database (Denmark)

    Carpenter, E.E.; Long, J.W.; Rolison, D.R.

    2006-01-01

    A sol-gel synthesis was used to produce iron oxide aerogels. These nanocrystalline aerogels have a pore-solid structure similar to silica aerogels but are composed entirely of iron oxides. Mössbauer experiments and x-ray diffraction showed that the as-prepared aerogel is an amorphous or poorly...... crystalline iron oxide, which crystallized as a partially oxidized magnetite during heating in argon. After further heat treatment in air, the nanocrystallites are fully converted to maghemite. The particles are superparamagnetic at high temperatures, but the magnetic properties are strongly influenced...

  8. Green synthesis of hybrid graphene oxide/microcrystalline cellulose aerogels and their use as superabsorbents

    International Nuclear Information System (INIS)

    Wei, Xiao; Huang, Ting; Yang, Jing-hui; Zhang, Nan; Wang, Yong; Zhou, Zuo-wan

    2017-01-01

    Highlights: • Hybrid GO/MCC aerogels were prepared using LiBr aqueous solution as the solvent. • GO was exfoliated by MCC through the strong interaction between them. • The adsorption ability of GO per unit mass in the hybrid aerogels was greatly enhanced. - Abstract: In this work, we developed a green synthesis method to prepare the hybrid aerogels containing graphene oxide (GO) and microcrystalline cellulose (MCC) using lithium bromide (LiBr) aqueous solution as the solvent, which insured the complete dissolution of MCC. The interaction between GO and MCC was investigated through different methods The results demonstrate that there is a strong interaction between GO and MCC molecules, which promotes the exfoliation of GO in the hybrid aerogels. The hybrid GO/MCC aerogels exhibit typical three dimensional porous structure and the pore morphology can be well adjusted by changing the content of GO. The adsorption ability of the hybrid aerogels was measured using methylene blue (MB) as an adsorbate. The results show that the adsorption ability of GO per unit mass is greatly enhanced compared with the pure GO aerogel, especially at relatively low GO content the adsorption amount of GO per unit mass is enhanced up to 2630 mg/g. Further results demonstrate that the hybrid GO/MCC aerogels still obey the pseudo-second-order adsorption model, which is similar to that of the pure GO aerogel. The mechanism for the amplified adsorption ability of GO in the hybrid GO/MCC aerogels is then analyzed.

  9. Green synthesis of hybrid graphene oxide/microcrystalline cellulose aerogels and their use as superabsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xiao; Huang, Ting; Yang, Jing-hui; Zhang, Nan; Wang, Yong, E-mail: yongwang1976@163.com; Zhou, Zuo-wan

    2017-08-05

    Highlights: • Hybrid GO/MCC aerogels were prepared using LiBr aqueous solution as the solvent. • GO was exfoliated by MCC through the strong interaction between them. • The adsorption ability of GO per unit mass in the hybrid aerogels was greatly enhanced. - Abstract: In this work, we developed a green synthesis method to prepare the hybrid aerogels containing graphene oxide (GO) and microcrystalline cellulose (MCC) using lithium bromide (LiBr) aqueous solution as the solvent, which insured the complete dissolution of MCC. The interaction between GO and MCC was investigated through different methods The results demonstrate that there is a strong interaction between GO and MCC molecules, which promotes the exfoliation of GO in the hybrid aerogels. The hybrid GO/MCC aerogels exhibit typical three dimensional porous structure and the pore morphology can be well adjusted by changing the content of GO. The adsorption ability of the hybrid aerogels was measured using methylene blue (MB) as an adsorbate. The results show that the adsorption ability of GO per unit mass is greatly enhanced compared with the pure GO aerogel, especially at relatively low GO content the adsorption amount of GO per unit mass is enhanced up to 2630 mg/g. Further results demonstrate that the hybrid GO/MCC aerogels still obey the pseudo-second-order adsorption model, which is similar to that of the pure GO aerogel. The mechanism for the amplified adsorption ability of GO in the hybrid GO/MCC aerogels is then analyzed.

  10. Reduced graphene oxide aerogel networks with soft interfacial template for applications in bone tissue regeneration

    Science.gov (United States)

    Asha, S.; Ananth, A. Nimrodh; Jose, Sujin P.; Rajan, M. A. Jothi

    2018-05-01

    Reduced Graphene Oxide aerogels (A-RGO), functionalized with chitosan, were found to induce and/or accelerate the mineralization of hydroxyapatite. The functionalized chitosan acts as a soft interfacial template on the surface of A-RGO assisting the growth of hydroxyapatite particles. The mineralization on these soft aerogel networks was performed by soaking the aerogels in simulated body fluid, relative to time. Polymer-induced mineralization exhibited an ordered arrangement of hydroxyapatite particles on reduced graphene oxide aerogel networks with a higher crystalline index (IC) of 1.7, which mimics the natural bone formation indicating the importance of the polymeric interfacial template. These mineralized aerogels which mimic the structure and composition of natural bone exhibit relatively higher rate of cell proliferation, osteogenic differentiation and osteoid matrix formation proving it to be a potential scaffold for bone tissue regeneration.

  11. Graphene aerogels

    Science.gov (United States)

    Pauzauskie, Peter J; Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H; Biener, Juergen

    2015-03-31

    Graphene aerogels with high conductivity and surface areas including a method for making a graphene aerogel, including the following steps: (1) preparing a reaction mixture comprising a graphene oxide suspension and at least one catalyst; (2) curing the reaction mixture to produce a wet gel; (3) drying the wet gel to produce a dry gel; and (4) pyrolyzing the dry gel to produce a graphene aerogel. Applications include electrical energy storage including batteries and supercapacitors.

  12. Readout ASICs and Electronics for the 144-channel HAPDs for the Aerogel RICH at Belle II

    Science.gov (United States)

    Nishida, S.; Adachi, I.; Ikeda, H.; Hara, K.; Iijima, T.; Iwata, S.; Korpar, S.; Križan, P.; Kuroda, E.; Pestotnik, R.; Seljak, A.; Sumiyoshi, T.; Takagaki, H.

    The particle identification (PID) device in the endcap of the Belle detector will be upgraded to a ring imaging Cherenkov counter (RICH) using aerogel as a radiator at the Belle II experiment. We develop the electronics to read out the 70,000 channels of hit information from the 144-channel hybrid avalanche photodetectors (HAPD), of the aerogel RICH detector. A readout ASIC is developed to digitize the HAPD signals, and was used in a beam test with the prototype detector. The performance and plan of the ASIC is reported in this study. We have also designed the readout electronics for the aerogel RICH, which consist of front-end boards with the ASICs merger boards to collect data from the front-end boards. A front-end board that fits in the actual available space for the aerogel RICH electronics was produced.

  13. Oxidation-mediated chitosan as additives for creation of chitosan aerogels with diverse three-dimensional interconnected skeletons

    International Nuclear Information System (INIS)

    Zhang, Sizhao; Feng, Jian; Feng, Junzong; Jiang, Yonggang

    2017-01-01

    Highlights: • A new synthetic method for controlling morphology of chitosan aerogels is proposed. • Chitosan aerogels with nanoflake-like and nanofiber-like were prepared. • Textures of chitosan aerogels are strongly dependent upon the oxidation pattern. - Abstract: Naturally occurring polymer-based aerogels have myriad practical utilizations due to environmentally benign and fruitful resources. However, engineering morphology-controllable biomass aerogels still represents a great challenge. Here we present a facile solution to synthesize chitosan aerogels having distinguished textures by reacting oxidized chitosan with formaldehyde and chitosan sol. In more detail, chitosan was chemically oxidized using two types of oxidation agents such as ammonium persulphate (SPD) and sodium periodate (APS) to obtain corresponding oxidized chitosan, subsequently cross-linked with chitosan solution containing formaldehyde to harvest SPD-oxidized chitosan aerogels (SCAs) and APS-SPD-oxidized ones (ASCAs) after aging, solvent exchange and supercritical drying processes. We found that the morphologies of as-prepared chitosan aerogels are strongly dependent upon the oxidation pattern towards chitosan. The structural textures of SCAs and ASCAs appear nanoflake-like and nanofiber-like structures, which may be related to spatial freedom of active groups located in chitosan. Selected area electron diffraction analysis reveals that the crystalline properties of chitosan aerogels generally appear the serious deterioration comparing to raw chitosan owing to their interconnected skeletal structure formation. The occurrence of characteristic groups displays cross-linked chain construction by using chemical state measurements such as FT-IR and XPS. Further, a plausible mechanism for controlling morphology of chitosan aerogels is also established. This new family of method for creation of chitosan aerogels may open up a perspective for biomass aerogels with controllable textures.

  14. Oxidation-mediated chitosan as additives for creation of chitosan aerogels with diverse three-dimensional interconnected skeletons

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Sizhao, E-mail: bule-soul@hotmail.com; Feng, Jian, E-mail: fengj@nudt.edu.cn; Feng, Junzong; Jiang, Yonggang

    2017-02-28

    Highlights: • A new synthetic method for controlling morphology of chitosan aerogels is proposed. • Chitosan aerogels with nanoflake-like and nanofiber-like were prepared. • Textures of chitosan aerogels are strongly dependent upon the oxidation pattern. - Abstract: Naturally occurring polymer-based aerogels have myriad practical utilizations due to environmentally benign and fruitful resources. However, engineering morphology-controllable biomass aerogels still represents a great challenge. Here we present a facile solution to synthesize chitosan aerogels having distinguished textures by reacting oxidized chitosan with formaldehyde and chitosan sol. In more detail, chitosan was chemically oxidized using two types of oxidation agents such as ammonium persulphate (SPD) and sodium periodate (APS) to obtain corresponding oxidized chitosan, subsequently cross-linked with chitosan solution containing formaldehyde to harvest SPD-oxidized chitosan aerogels (SCAs) and APS-SPD-oxidized ones (ASCAs) after aging, solvent exchange and supercritical drying processes. We found that the morphologies of as-prepared chitosan aerogels are strongly dependent upon the oxidation pattern towards chitosan. The structural textures of SCAs and ASCAs appear nanoflake-like and nanofiber-like structures, which may be related to spatial freedom of active groups located in chitosan. Selected area electron diffraction analysis reveals that the crystalline properties of chitosan aerogels generally appear the serious deterioration comparing to raw chitosan owing to their interconnected skeletal structure formation. The occurrence of characteristic groups displays cross-linked chain construction by using chemical state measurements such as FT-IR and XPS. Further, a plausible mechanism for controlling morphology of chitosan aerogels is also established. This new family of method for creation of chitosan aerogels may open up a perspective for biomass aerogels with controllable textures.

  15. Cobalt sulfide aerogel prepared by anion exchange method with enhanced pseudocapacitive and water oxidation performances

    Science.gov (United States)

    Gao, Qiuyue; Shi, Zhenyu; Xue, Kaiming; Ye, Ziran; Hong, Zhanglian; Yu, Xinyao; Zhi, Mingjia

    2018-05-01

    This work introduces the anion exchange method into the sol-gel process for the first time to prepare a metal sulfide aerogel. A porous Co9S8 aerogel with a high surface area (274.2 m2 g‑1) and large pore volume (0.87 cm3 g‑1) has been successfully prepared by exchanging cobalt citrate wet gel in thioacetamide and subsequently drying in supercritical ethanol. Such a Co9S8 aerogel shows enhanced supercapacitive performance and catalytic activity toward oxygen evolution reaction (OER) compared to its oxide aerogel counterpart. High specific capacitance (950 F g‑1 at 1 A g‑1), good rate capability (74.3% capacitance retention from 1 to 20 A g‑1) and low onset overpotential for OER (220 mV) were observed. The results demonstrated here have implications in preparing various sulfide chalcogels.

  16. Method for producing metal oxide aerogels having densities less than 0. 02 g/cc

    Science.gov (United States)

    Tillotson, T.M.; Poco, J.F.; Hrubesh, L.W.; Thomas, I.M.

    1994-01-04

    A two-step method is described for making transparent aerogels which have a density of less than 0.003 g/cm[sup 3] to those with a density of more than 0.8 g/cm[sup 3], by a sol/gel process and supercritical extraction. Condensed metal oxide intermediate made with purified reagents can be diluted to produce stable aerogels with a density of less than 0.02 g/cm[sup 3]. High temperature, direct supercritical extraction of the liquid phase of the gel produces hydrophobic aerogels which are stable at atmospheric moisture conditions. Monolithic, homogeneous silica aerogels with a density of less than 0.02 to higher than 0.8 g/cm[sup 3], with high thermal insulation capacity, improved mechanical strength and good optical transparency, are described. 7 figures.

  17. Freeze-Casting Produces a Graphene Oxide Aerogel with a Radial and Centrosymmetric Structure.

    Science.gov (United States)

    Wang, Chunhui; Chen, Xiong; Wang, Bin; Huang, Ming; Wang, Bo; Jiang, Yi; Ruoff, Rodney S

    2018-05-14

    We report the assembly of graphene oxide (G-O) building blocks into a vertical and radially aligned structure by a bidirectional freeze-casting approach. The crystallization of water to ice assembles the G-O sheets into a structure, a G-O aerogel whose local structure mimics turbine blades. The centimeter-scale radiating structure in this aerogel has many channels whose width increases with distance from the center. This was achieved by controlling the formation of the ice crystals in the aqueous G-O dispersion that grew radially in the shape of lamellae during freezing. Because the shape and size of ice crystals is influenced by the G-O sheets, different additives (ethanol, cellulose nanofibers, and chitosan) that can form hydrogen bonds with H 2 O were tested and found to affect the interaction between the G-O and formation of ice crystals, producing ice crystals with different shapes. A G-O/chitosan aerogel with a spiral pattern was also obtained. After chemical reduction of G-O, our aerogel exhibited elasticity and absorption capacity superior to that of graphene aerogels with "traditional" pore structures made by conventional freeze-casting. This methodology can be expanded to many other configurations and should widen the use of G-O (and reduced G-O and "graphenic") aerogels.

  18. Construction of silica aerogel radiator system for Belle II RICH Counter

    Science.gov (United States)

    Adachi, I.; Dolenec, R.; Hataya, K.; Iori, S.; Iwata, S.; Kakuno, H.; Kataura, R.; Kawai, H.; Kindo, H.; Kobayashi, T.; Korpar, S.; Križan, P.; Kumita, T.; Mrvar, M.; Nishida, S.; Ogawa, K.; Ogawa, S.; Pestotnik, R.; Šantelj, L.; Sumiyoshi, T.; Tabata, M.; Yonenaga, M.; Yusa, Y.

    2017-12-01

    We have developed a RICH counter as a new forward particle identification device for the Belle II experiment. As a Cherenkov radiator in this counter, a dual aerogel layer combination consisting of two refractive indicies, n=1.045 and 1.055, is employed. Mass production of these aerogel tiles has been done during 2013-2014 with new method improved by Chiba group. Optical qualities for them have been examined. The refractive indices of the obtained tiles were found to be in good agreement with our expectations, and the transparencies were high enough to be used for the RICH radiator.

  19. Silica aerogel radiator for use in the A-RICH system utilized in the Belle II experiment

    Energy Technology Data Exchange (ETDEWEB)

    Tabata, Makoto, E-mail: makoto@hepburn.s.chiba-u.ac.jp [Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara (Japan); Department of Physics, Chiba University, Chiba (Japan); Adachi, Ichiro [Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Hamada, Nao [Department of Physics, Toho University, Funabashi (Japan); Hara, Koji [Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Iijima, Toru [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya (Japan); Iwata, Shuichi; Kakuno, Hidekazu [Department of Physics, Tokyo Metropolitan University, Hachioji (Japan); Kawai, Hideyuki [Department of Physics, Chiba University, Chiba (Japan); Korpar, Samo [Faculty of Chemistry and Chemical Engineering, University of Maribor, Maribor (Slovenia); Experimental High Energy Physics Department, Jožef Stefan Institute, Ljubljana (Slovenia); Križan, Peter [Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana (Slovenia); Experimental High Energy Physics Department, Jožef Stefan Institute, Ljubljana (Slovenia); Kumita, Tetsuro [Department of Physics, Tokyo Metropolitan University, Hachioji (Japan); Nishida, Shohei [Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Ogawa, Satoru [Department of Physics, Toho University, Funabashi (Japan); Pestotnik, Rok; Šantelj, Luka; Seljak, Andrej [Experimental High Energy Physics Department, Jožef Stefan Institute, Ljubljana (Slovenia); Sumiyoshi, Takayuki [Department of Physics, Tokyo Metropolitan University, Hachioji (Japan); and others

    2014-12-01

    This paper presents recent progress in the development and mass production of large-area hydrophobic silica aerogels for use as radiators in the aerogel-based ring-imaging Cherenkov (A-RICH) counter, which will be installed in the forward end cap of the Belle II detector. The proximity-focusing A-RICH system is especially designed to identify charged kaons and pions. The refractive index of the installed aerogel Cherenkov radiators is approximately 1.05, and we aim for a separation capability exceeding 4σ at momenta up to 4 GeV/c. Large-area aerogel tiles (over 18×18×2 cm{sup 3}) were first fabricated in test productions by pin drying in addition to conventional methods. We proposed to fill the large end-cap region (area 3.5 m{sup 2}) with 124 water-jet-trimmed fan-shaped dual-layer-focusing aerogel combinations of different refractive indices (1.045 and 1.055). Guided by the test production results, we decided to manufacture aerogels by the conventional method and are currently proceeding with mass production. In an electron beam test undertaken at the DESY, we confirmed that the K/π separation capability of a prototype A-RICH counter exceeded 4σ at 4 GeV/c. - Highlights: • Aerogel tiling as a RICH radiator in the end cap of Belle II detector is proposed. • Conventional method for producing real-size aerogels is established. • No crack-free, real-size aerogels attained in the test production by pin drying. • Beam test confirms the utility of real-size aerogels made by conventional method. • Mass aerogel production for an actual RICH system started by conventional method.

  20. Nanocellulose-assisted low-temperature synthesis and supercapacitor performance of reduced graphene oxide aerogels

    Science.gov (United States)

    Wang, Jie; Ran, Ran; Sunarso, Jaka; Yin, Chao; Zou, Honggang; Feng, Yi; Li, Xiaobao; Zheng, Xu; Yao, Jianfeng

    2017-04-01

    Here, we have synthesized reduced graphene oxide (rGO) aerogels using a nanocellulose-assisted low temperature (less than 500 °C) thermal treatment route where nanocelluloses promote the gelation of graphene oxide (GO) solution that benefits the fabrication of GO aerogels from low concentration dispersion (2.85 mg mL-1), and after their thermal decomposition the residual nanofibers act as spacer both prevent the re-stacking of graphene sheets and integrate with rGO sheets to give a particular kind of carbon-based aerogel along with numerous defects (holes). Thermal decomposition of nanocellulose appears to be complete beyond 350 °C thus its presence in form of amorphous carbon nanofibers in rGO sheets. The rGO aerogels synthesized at 350 °C provide the best balance in terms of wide interlayer spacing, high content of CO-type functional groups, and high defects content. This translates into a high discharge capacitance of 270 F g-1 at a current rate of 1 A g-1 for compressed rGO aerogels without any binder or conductive additive. Detailed electrochemical tests using 6 M KOH electrolyte establish the fact that pseudocapacitance component has substantial contribution towards the overall capacitance; closely approaching the contribution of the double layer capacitance that is the most dominant capacitance component.

  1. Ag2O/sodium alginate-reduced graphene oxide aerogel beads for efficient visible light driven photocatalysis

    Science.gov (United States)

    Ma, Yuhua; Wang, Jiajia; Xu, Shimei; Feng, Shun; Wang, Jide

    2018-02-01

    In this work, one facile and green method was developed to resolve the instinct defects of pure Ag2O and increase visible-light photocatalytic activity of Ag2O-based catalyst. In which, Ag2O was immobilized in sodium alginate-reduced graphene oxide (ALG-rGO) aerogel beads. The as-prepared aerogel beads showed a well-defined interconnected three-dimensional porous network and displayed the highest photocatalytic activity with a mass ratio of 40:1 (ALG:rGO). For the degradation of cationic Rhodamine B (RhB) and anionic dye Orange II (OII) dyes, rate constants were 1.95 × 10-2 min-1 and 4.13 × 10-2 min-1, which were 2.4 and 3.1 times higher than those of Ag2O/ALG aerogel beads, respectively. The further studies demonstrated that presence of rGO can effectively decrease the size of Ag2O, extend photoresponding range (UV to near-infrared light spectrum), speed-up separate photogenerated electrons and holes, retard charge recombination, and prolong electron lifetime and effective carrier diffusion length. The potential mechanism for RhB and OII degrading was expounded, and main active species in the degradation reactions of dyes were investigated by a series of trapping experiments. It offered a promising photocatalyst to purify the wastewater, and provided a sophisticated understanding of the pivotal role rGO acting in photocatalysis.

  2. Aerogel nanoscale aluminium oxides as a destructive sorbent for mustard gas

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Bakardjieva, Snejana; Maříková, Monika; Šubrt, Jan; Oplustil, F.; Olšanská, M.

    2003-01-01

    Roč. 47, č. 4 (2003), s. 175-180 ISSN 0862-5468 R&D Projects: GA MŠk LN00A028 Institutional research plan: CEZ:AV0Z4032918 Keywords : aluminium oxide * aerogels * sonogels Subject RIV: CA - Inorganic Chemistry Impact factor: 0.449, year: 2003

  3. Superior microwave absorption properties of ultralight reduced graphene oxide/black phosphorus aerogel

    Science.gov (United States)

    Hao, Chunxue; Wang, Bochong; Wen, Fusheng; Mu, Congpu; Xiang, Jianyong; Li, Lei; Liu, Zhongyuan

    2018-06-01

    Through a facile self-assembled process, an ultralight reduced graphene oxide/black phosphorus (rGO/BP) composite aerogel was successfully fabricated. The BP nanosheets were homogeneously distributed throughout the rGO 3D framework, and the interfaces between rGO and BP possessed four kinds of interconnections, such as wrapping, wearing, bridging and weak linking. As an ultralight composite, the rGO/BP aerogel could easily stand on the stamen of a flower. Compared with pure rGO aerogel, the rGO/BP composite aerogel exhibited enhanced microwave absorption ability. The minimum reflection loss value of ‑46.9 dB with a thickness of 2.53 mm was obtained, and a wide absorption band of 6.1 GHz (RL < ‑10 dB) was achieved. The superior microwave absorption property was demonstrated to stem from the interfacial polarization loss mechanism in which the multiform interface interactions between the rGO skeleton and BP nanosheets played critical roles. The rGO/BP aerogel has great potential to be used as an ultralight microwave absorber.

  4. Non-Parametric Kinetic (NPK Analysis of Thermal Oxidation of Carbon Aerogels

    Directory of Open Access Journals (Sweden)

    Azadeh Seifi

    2017-05-01

    Full Text Available In recent years, much attention has been paid to aerogel materials (especially carbon aerogels due to their potential uses in energy-related applications, such as thermal energy storage and thermal protection systems. These open cell carbon-based porous materials (carbon aerogels can strongly react with oxygen at relatively low temperatures (~ 400°C. Therefore, it is necessary to evaluate the thermal performance of carbon aerogels in view of their energy-related applications at high temperatures and under thermal oxidation conditions. The objective of this paper is to study theoretically and experimentally the oxidation reaction kinetics of carbon aerogel using the non-parametric kinetic (NPK as a powerful method. For this purpose, a non-isothermal thermogravimetric analysis, at three different heating rates, was performed on three samples each with its specific pore structure, density and specific surface area. The most significant feature of this method, in comparison with the model-free isoconversional methods, is its ability to separate the functionality of the reaction rate with the degree of conversion and temperature by the direct use of thermogravimetric data. Using this method, it was observed that the Nomen-Sempere model could provide the best fit to the data, while the temperature dependence of the rate constant was best explained by a Vogel-Fulcher relationship, where the reference temperature was the onset temperature of oxidation. Moreover, it was found from the results of this work that the assumption of the Arrhenius relation for the temperature dependence of the rate constant led to over-estimation of the apparent activation energy (up to 160 kJ/mol that was considerably different from the values (up to 3.5 kJ/mol predicted by the Vogel-Fulcher relationship in isoconversional methods

  5. Polyethyleneglycol/silver functionalized reduced graphene oxide aerogel for environmental application

    Science.gov (United States)

    Kumari, G. Vanitha; Asha, S.; Ananth, A. Nimrodh; Rajan, M. A. Jothi; Mathavan, T.

    2018-04-01

    Polyethylene glycol (PEG)/Silver (Ag) functionalized reduced graphene oxide aerogel (RGOA) was synthesized. PEG/Ag decorated reduced graphene oxide aerogel was characterized using XRD, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR). The surface morphology of PEG/Ag/RGOA was analyzed using scanning electron microscope. The non-covalent interaction between reduced graphene oxide layers and the interaction between PEG and Ag on RGOA were studied by FT-IR spectra. It was observed that the interaction between Ag and PEG could enhance the properties of RGOA. Methyl Orange (MO) dye degradation was observed from UV-Vis Spectra. The process was studied by monitoring the simultaneous decrease in the height of UV-Vis absorption peak of dye solution. The results show that PEG/RGOA and PEG/Ag/RGOA are an efficient catalyst for dye degradation.

  6. Three-dimensional barium-sulfate-impregnated reduced graphene oxide aerogel for removal of strontium from aqueous solutions

    Science.gov (United States)

    Jang, Jiseon; Lee, Dae Sung

    2018-06-01

    A three-dimensional barium-sulfate-impregnated reduced graphene oxide (BaSO4-rGO) aerogel was successfully synthesized by a facile one-step hydrothermal method and was used as an adsorbent to remove strontium from aqueous solutions. The characterized elemental composition, crystal structure, and morphology of the prepared aerogel confirmed that barium sulfate particles were firmly anchored on the surface of the rGO sheets and exhibited a porous 3D structure with a high surface area of 129.37 m2/g. The mass ratio of BaSO4 in the BaSO4-rGO aerogel substantially affected strontium adsorption, and the optimal BaSO4/rGO ratio was found to be 1:1. The synthesized BaSO4-rGO aerogel not only reached adsorption equilibrium within 1 h, but also showed much higher adsorption capacity than an rGO aerogel. The experimental data were well fitted to a pseudo-second-order kinetic model and the adsorption behavior followed the Langmuir isotherm. The adsorption capacity of strontium on BaSO4-rGO aerogels remained relatively high even under ionic competition in simulated seawater. These results showed that the BaSO4-rGO aerogel is an efficient and promising adsorbent for the treatment of strontium in aqueous solutions.

  7. Silica aerogel radiator for use in the A-RICH system utilized in the Belle II experiment

    Science.gov (United States)

    Tabata, Makoto; Adachi, Ichiro; Hamada, Nao; Hara, Koji; Iijima, Toru; Iwata, Shuichi; Kakuno, Hidekazu; Kawai, Hideyuki; Korpar, Samo; Križan, Peter; Kumita, Tetsuro; Nishida, Shohei; Ogawa, Satoru; Pestotnik, Rok; Šantelj, Luka; Seljak, Andrej; Sumiyoshi, Takayuki; Tahirović, Elvedin; Yoshida, Keisuke; Yusa, Yosuke

    2014-12-01

    This paper presents recent progress in the development and mass production of large-area hydrophobic silica aerogels for use as radiators in the aerogel-based ring-imaging Cherenkov (A-RICH) counter, which will be installed in the forward end cap of the Belle II detector. The proximity-focusing A-RICH system is especially designed to identify charged kaons and pions. The refractive index of the installed aerogel Cherenkov radiators is approximately 1.05, and we aim for a separation capability exceeding 4σ at momenta up to 4 GeV/c. Large-area aerogel tiles (over 18×18×2 cm3) were first fabricated in test productions by pin drying in addition to conventional methods. We proposed to fill the large end-cap region (area 3.5 m2) with 124 water-jet-trimmed fan-shaped dual-layer-focusing aerogel combinations of different refractive indices (1.045 and 1.055). Guided by the test production results, we decided to manufacture aerogels by the conventional method and are currently proceeding with mass production. In an electron beam test undertaken at the DESY, we confirmed that the K/π separation capability of a prototype A-RICH counter exceeded 4σ at 4 GeV/c.

  8. Aerogels Handbook

    CERN Document Server

    Aegerter, Michel A; Koebel, Matthias M

    2011-01-01

    Aerogels are the lightest solids known. Up to 1000 times lighter than glass and with a density as low as only four times that of air, they show very high thermal, electrical and acoustic insulation values and hold many entries in Guinness World Records. Originally based on silica, R&D efforts have extended this class of materials to non-silicate inorganic oxides, natural and synthetic organic polymers, carbon, metal and ceramic materials, etc. Composite systems involving polymer-crosslinked aerogels and interpenetrating hybrid networks have been developed and exhibit remarkable mechanical strength and flexibility. Even more exotic aerogels based on clays, chalcogenides, phosphides, quantum dots, and biopolymers such as chitosan are opening new applications for the construction, transportation, energy, defense and healthcare industries. Applications in electronics, chemistry, mechanics, engineering, energy production and storage, sensors, medicine, nanotechnology, military and aerospace, oil and gas recove...

  9. Insights into the Controllable Chemical Composition of Metal Oxide Nanowires and Graphene Aerogels

    Science.gov (United States)

    Goldstein, Anna Patrice

    briefly, then isolated pockets of MTiO3 are formed on the nanowire surface. This structure retains the conductive channel in the center of the nanowire, which can be useful for charge separation. Longer annealing times result in segmented nanowires; the segments formed from a Ni-coated nanowire are bounded by TiO2(01-1) twin planes and NiTiO 3{100}/TiO2{03-1} interfaces. An alternative strategy for storing solar energy takes advantage of the capacitance between a semiconductor surface and adsorbed ions in solution. This type of energy storage device is called an electric double layer capacitor (EDLC). Graphene-based aerogels, which are porous materials composed of few-layer graphitic sheets, have the potential for higher surface area and higher conductivity than standard carbon aerogels. These properties make graphene-based aerogels a good material candidate for EDLC electrodes. Graphene oxide (GO) is the precursor material for the synthesis of a graphene-based aerogel, and it has been widely studied. Yet its hydrothermal gelation is still not fully understood, due to the high pressure reaction conditions and the non-uniform nature of GO. We demonstrate a number of changes that occur to the GO sheets during gelation: wrinkling, formation of a densified monolith, deoxygenation, increasing thermal stability, and color change. Plotting the time evolution of all these properties shows that they are simultaneous and likely of common origin. Possible mechanisms for gelation are explored. Graphene aerogels are synthesized by vapor phase thermal reduction of GO aerogels at temperatures up to 1600 °C. Further deoxygenation is observed in the aerogel during thermal reduction, along with enhanced crystallinity and an associated change in the electronic structure. When graphene aerogels are exposed to high-temperature boron oxide vapor, they are converted to boron nitride (BN) aerogels. The structure of the BN aerogel is investigated and shown to be similar in nanoscale morphology

  10. The aerogel Ring Imaging Cherenkov system at the Belle II spectrometer

    Science.gov (United States)

    Pestotnik, R.; Adachi, I.; Dolenec, R.; Hataya, K.; Iori, S.; Iwata, S.; Kakuno, H.; Kataura, R.; Kawai, H.; Kindo, H.; Kobayashi, T.; Korpar, S.; Križan, P.; Kumita, T.; Mrvar, M.; Nishida, S.; Ogawa, K.; Ogawa, S.; Šantelj, L.; Sumiyoshi, T.; Tabata, M.; Yonenaga, M.; Yusa, Y.

    2017-12-01

    In the forward end-cap of the Belle II spectrometer, a proximity focusing Ring Imaging Cherenkov counter with an aerogel radiator will be installed. The detector will occupy a limited space inside solenoid magnet with longitudinal field of 1.5 T. It will consist of a double layer aerogel radiator, an expansion volume and a photon detector. 420 Hamamatsu hybrid avalanche photo sensors with 144 channels each will be used to read out single Cherenkov photons with high efficiency. More than 60,000 analog signals will be digitized and processed in the front end electronics and send to the unified experiment data acquisition system. The detector components have been successfully produced and are now being installed in the spectrometer. Tested before on the bench, they are currently being installed in the mechanical frame. Part of the detector have been commissioned and connected to the acquisition system to register the cosmic ray particles. The first preliminary results are in accordance with previous expectations. We expect an excellent performance of the device which will allow at least a 4σ separation of pions from kaons in the experiment kinematic region from 0.5 GeV/c to 4 GeV/c.

  11. Test of the HAPD light sensor for the Belle II Aerogel RICH

    Science.gov (United States)

    Yusa, Y.; Adachi, I.; Dolenec, R.; Hayata, K.; Iori, S.; Iwata, S.; Kakuno, H.; Kataura, R.; Kawai, H.; Kindo, H.; Kobayashi, T.; Korpar, S.; Krizan, P.; Kumita, T.; Mrvar, M.; Nishida, S.; Ogawa, K.; Pestotnik, R.; Santelj, L.; Sumiyoshi, T.; Tabata, M.; Yonenaga, M.

    2017-12-01

    The Aerogel Ring-Imaging Cherenkov detector (ARICH) is being installed in the endcap region of Belle II spectrometer to identify particles from B meson decays by detecting the Cherenkov ring image from aerogel radiators. To detect single photons, high-sensitive photon detector which has wide effective area (∼70 mm × 70 mm), a Hybrid Avalanche Photo Detector (HAPD), has been developed in a collaboration with Hamamatsu K.K. The HAPD consists of hybrid structure of a vacuum tube and an avalanche photodiode (APD). It can be operated in 1.5 T magnetic field of the spectrometer and withstands the radiation levels expected in the Belle II experiment. There are two steps of electric pulse amplification: acceleration of photo-electron in electric field in the vacuum tube part and electron avalanche in the APD part resulting in total gain of order 105. For the ARICH, we use 420 HAPDs in total. Before installing them, we performed quality assessment studies such as measurements of dark current, noise level, signal-to-noise ratio and two-dimensional scan with laser illumination. We also measured quantum efficiency of the photocathode. During the HAPD performance tests in the magnetic field, we observed very large signal pulses which cause long dead time of the readout electronics in some of the HAPDs. We have carried out a number of studies to understand this phenomenon, and have found a way to mitigate it and suppress the degradation of the ARICH performance. In this report, we will show a summary of the HAPD performance and quality assessment measurements including validation in the magnetic field for all of the HAPDs manufactured for the ARICH in the Belle II.

  12. Chitosan-graphene oxide films and CO2-dried porous aerogel microspheres: Interfacial interplay and stability.

    Science.gov (United States)

    Frindy, Sana; Primo, Ana; Ennajih, Hamid; El Kacem Qaiss, Abou; Bouhfid, Rachid; Lahcini, Mohamed; Essassi, El Mokhtar; Garcia, Hermenegildo; El Kadib, Abdelkrim

    2017-07-01

    The intimate interplay of chitosan (CS) and graphene oxide (GO) in aqueous acidic solution has been explored to design upon casting, nanostructured "brick-and-mortar" films (CS-GO-f) and by acidic-to-basic pH inversion, porous CO 2 -dried aerogel microspheres (CS-GO-m). Owing to the presence of oxygenated functional groups in GO, good-quality crack-free hybrid films were obtained. Mechanical properties were improved independently of the GO content and it was found that a 20wt% loading affords hybrid film characterized with a Young modulus three times superior to that reached with the same loading of layered clay. The presence of graphene oxide was found to be detrimental for the thermal stability of the polysaccharide at T <350°C, a fact attributed to the well-established decomposition of the oxygenated functional groups of the graphene sheets. Irrespective to the graphene oxide loading, chitosan-graphene oxide mixture preserves the gelation memory of the polysaccharide. Supercritical drying of the resulting soft hydrogels provides macroporous network with surface areas ranging from 226m 2 g -1 to 554m 2 g -1 . XPS and RAMAN analyses evidenced the selective reduction of GO sheets inside of these microspheres, affording the hitherto unknown macroporous chitosan-entangled-reduced graphene oxide (CS-rGO-m) aerogels. Improvement in both hydrothermal stability (under water reflux) and chemical stability (under acidic conditions) have been noticed for chitosan-graphene oxide microspheres with respect to non-modified chitosan and chitosan-clay bio-hybrids, a result rooted in the substantial hydrophobic character imparted by the addition of graphenic material to the polysaccharide skeleton. In essence, this contribution demonstrates that graphene oxide loading do not disturb neither the filmogenicity of chitosan nor its gelation ability and constitutes a promising route for novel chitosan-based functional hybrid materials. Copyright © 2017 Elsevier Ltd. All rights

  13. Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solid-state supercapacitors

    Science.gov (United States)

    Qifeng Zheng; Zhiyong Cai; Zhenqiang Ma; Shaoqin Gong

    2015-01-01

    A novel type of highly flexible and all-solid-state supercapacitor that uses cellulose nanofibril (CNF)/reduced graphene oxide (RGO)/carbon nanotube (CNT) hybrid aerogels as electrodes and H2SO4 poly (vinyl alcohol) PVA gel as the electrolyte was developed and is reported here. These flexible solid-state supercapacitors...

  14. Reduced graphene oxide aerogel with high-rate supercapacitive performance in aqueous electrolytes

    Science.gov (United States)

    Si, Weijiang; Wu, Xiaozhong; Zhou, Jin; Guo, Feifei; Zhuo, Shuping; Cui, Hongyou; Xing, Wei

    2013-05-01

    Reduced graphene oxide aerogel (RGOA) is synthesized successfully through a simultaneous self-assembly and reduction process using hypophosphorous acid and I2 as reductant. Nitrogen sorption analysis shows that the Brunauer-Emmett-Teller surface area of RGOA could reach as high as 830 m2 g-1, which is the largest value ever reported for graphene-based aerogels obtained through the simultaneous self-assembly and reduction strategy. The as-prepared RGOA is characterized by a variety of means such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical tests show that RGOA exhibits a high-rate supercapacitive performance in aqueous electrolytes. The specific capacitance of RGOA is calculated to be 211.8 and 278.6 F g-1 in KOH and H2SO4 electrolytes, respectively. The perfect supercapacitive performance of RGOA is ascribed to its three-dimensional structure and the existence of oxygen-containing groups.

  15. Visible photocatalytic properties of vanadium doped zinc oxide aerogel nanopowder

    Energy Technology Data Exchange (ETDEWEB)

    Slama, R. [Laboratoire de Physique des Materiaux et des Nanomateriaux appliquee a l' Environnement, Faculte des Sciences de Gabes, Universite de Gabes, Cite Erriadh Manara Zrig, 6072 Gabes (Tunisia); Unite de Recherche Environnement, Catalyse et Analyse des procedes URECAP (UR/99/11-20), Ecole Nationale d' Ingenieurs de Gabes, Universite de Gabes, Route de Medenine 6029 Gabes (Tunisia); Ghribi, F. [Laboratoire de Physique des Materiaux et des Nanomateriaux appliquee a l' Environnement, Faculte des Sciences de Gabes, Universite de Gabes, Cite Erriadh Manara Zrig, 6072 Gabes (Tunisia); Houas, A. [Unite de Recherche Environnement, Catalyse et Analyse des procedes URECAP (UR/99/11-20), Ecole Nationale d' Ingenieurs de Gabes, Universite de Gabes, Route de Medenine 6029 Gabes (Tunisia); Barthou, C. [Institut des NanoSciences de Paris (INSP), UPMC Universite Paris 6, CNRS UMR 7588, 140 rue de Lourmel, F-75015 Paris France (France); El Mir, L., E-mail: Lassaad.ElMir@fsg.rnu.tn [Laboratoire de Physique des Materiaux et des Nanomateriaux appliquee a l' Environnement, Faculte des Sciences de Gabes, Universite de Gabes, Cite Erriadh Manara Zrig, 6072 Gabes (Tunisia); College of Sciences, Department of Physics, Al-Imam Muhammad Ibn Saud University, Riyadh 11623 (Saudi Arabia)

    2011-06-30

    Vanadium-doped zinc oxide nanoparticles have been synthesized by sol-gel method. In our approach the water for hydrolysis used in the synthesis of nanopowder was slowly released followed by a thermal drying in ethyl alcohol at 250 deg. C. The obtained nanopowder was characterized by various techniques such as particle size analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). In the as-prepared state, the powder with an average particle size of 25 nm presents a strong luminescence band in the visible range. From photoluminescence excitation (PLE) the energy position of the obtained PL band depends on the excitation wavelength and this PL band can be also observed under visible excitations. This result is very promising for visible photo catalysis applications, which was confirmed by methylene blue photo-degradation using visible lamp as a light source. - Research Highlights: > We explore the impact of plot size on estimation of a small watershed outputs. > Different lengths and fixed width plots were installed on two slope aspects. > The performance of two similar sets of experimental plots was examined. > The optimal lengths for estimation of sediment and runoff were finally found.

  16. Novel antimony doped tin oxide/carbon aerogel as efficient electrocatalytic filtration membrane

    Directory of Open Access Journals (Sweden)

    Zhimeng Liu

    2016-05-01

    Full Text Available A facile method was developed to prepare antimony doped tin oxide (Sb-SnO2/carbon aerogel (CA for use as an electrocatalytic filtration membrane. The preparation process included synthesis of a precursor sol, impregnation, and thermal decomposition. The Sb-SnO2, which was tetragonal in phase with an average crystallite size of 10.8 nm, was uniformly distributed on the CA surface and firmly attached via carbon-oxygen-tin chemical bonds. Preliminary filtration tests indicated that the Sb-SnO2/CA membrane had a high rate of total organic carbon removal for aqueous tetracycline owing to its high current efficiency and electrode stability.

  17. Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solid-state supercapacitors.

    Science.gov (United States)

    Zheng, Qifeng; Cai, Zhiyong; Ma, Zhenqiang; Gong, Shaoqin

    2015-02-11

    A novel type of highly flexible and all-solid-state supercapacitor that uses cellulose nanofibril (CNF)/reduced graphene oxide (RGO)/carbon nanotube (CNT) hybrid aerogels as electrodes and H2SO4/poly(vinyl alcohol) (PVA) gel as the electrolyte was developed and is reported here. These flexible solid-state supercapacitors were fabricated without any binders, current collectors, or electroactive additives. Because of the porous structure of the CNF/RGO/CNT aerogel electrodes and the excellent electrolyte absorption properties of the CNFs present in the aerogel electrodes, the resulting flexible supercapacitors exhibited a high specific capacitance (i.e., 252 F g(-1) at a discharge current density of 0.5 A g(-1)) and a remarkable cycle stability (i.e., more than 99.5% of the capacitance was retained after 1000 charge-discharge cycles at a current density of 1 A g(-1)). Furthermore, the supercapacitors also showed extremely high areal capacitance, areal power density, and energy density (i.e., 216 mF cm(-2), 9.5 mW cm(-2), and 28.4 μWh cm(-2), respectively). In light of its excellent electrical performance, low cost, ease of large-scale manufacturing, and environmental friendliness, the CNF/RGO/CNT aerogel electrodes may have a promising application in the development of flexible energy-storage devices.

  18. Strength-controllable graphene oxide amphiprotic aerogels as highly efficient carrier for anionic and cationic azo molecules

    Science.gov (United States)

    Xiong, Jiaqing; Jiao, Chenlu; Xu, Sijun; Tao, Jin; Zhang, Desuo; Lin, Hong; Chen, Yuyue

    2015-06-01

    Ice-bath self-assembly was employed to fabricate the GO/AP-MCC/CS aerogel based on natural materials. The components are amphiprotic microcrystalline cellulose (AP-MCC), chitosan (CS), and graphene oxide (GO), which act as the main framework, auxiliary framework and adhesive, respectively. The results of characterization determines the components form the GO/AP-MCC/CS aerogel according to chemical interactions. The mechanical properties depend largely on the mass ratio of AP-MCC/CS, which can be regulated by controlling the contents of AP-MCC and CS. The resultant GO/AP-MCC/CS aerogel was observed possessing three-dimensional (3D) interpenetrating porous networks with wrinkled structure on the inner wall, which provide a good encapsulation capacity for the guest molecules. As expected, owing to the amphiprotic properties and large specific surface area, GO/AP-MCC/CS aerogel exhibits high-efficiency load capacity for both anionic (CR) and cationic azo molecules (MB), which can reach up to about 132.2 mg/g for CR and 123.2 mg/g for MB, respectively.

  19. Methanol oxidation at carbon paste electrodes modified with (Pt–Ru)/carbon aerogels nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Fort, Carmen I., E-mail: iladiu@chem.ubbcluj.ro [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania); Cotet, Liviu C. [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania); Vasiliu, Florin [The National Institute of Materials Physics, Atomistilor str. 105 bis, PO Box MG. 7, Magurele, RO 077125, Bucharest (Romania); Marginean, Petre [National Institute for Research and Development of Isotopic and Molecular Technologies, RO 400293, Cluj-Napoca (Romania); Danciu, Virginia; Popescu, Ionel C. [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania)

    2016-04-01

    Mesoporous carbon aerogels (CAs) impregnated with (Pt–Ru) nanoparticles were prepared, incorporated into carbon paste electrodes (CPEs) and investigated as electrocatalysts for CH{sub 3}OH electro-oxidation. The sol–gel method, followed by supercritical drying with liquid CO{sub 2} and thermal pyrolysis in an inert atmosphere, was used to obtain high mesoporous CAs. (Pt–Ru)/CAs nanocomposites with various (Pt–Ru) loading were prepared by using Ru(AcAc){sub 3} and H{sub 2}PtCl{sub 6} as metal precursors and the impregnation method. The morpho-structural peculiarities of the so prepared (Pt–Ru)/CAs electrocatalysts were examined by using elemental analysis, N{sub 2} adsorption-desorption isotherms, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and selected area electron diffraction (SAED). Cyclic voltammetry measurements, carried out at (Pt–Ru)/CA-CPEs incorporating nanocomposites with various Pt–Ru loading and different specific surface areas, showed that CA with the highest specific surface area (843 m{sup 2}/g) and impregnated with 6% (w/w) (Pt–Ru) nanoparticles exhibit the best CH{sub 3}OH electro-oxidation efficiency. The Michaelis–Menten formalism was used to describe the dependence of the oxidation peak current on the CH{sub 3}OH concentration, allowing the estimation of the modified electrodes sensitivities. Thus, for (Pt–Ru, 10%)/CA{sub 535}-CPE was observed the highest sensitivity (12.5 ± 0.8 mA/M) and, at the same time, the highest maximum current density ever reported (153.1 mA/cm{sup 2} for 2 M CH{sub 3}OH and an applied potential of 600 mV vs. SHE). - Highlights: • (Pt–Ru) nanoparticles were deposited on high mesoporous carbon aerogels (CAs). • (Pt–Ru)/CAs were characterized by TEM, EDX, SAED and N{sub 2} adsorption-desorption. • Carbon paste electrodes modified with (Pt–Ru)/CA were used for CH{sub 3}OH oxidation. • (Pt–Ru, 10

  20. 1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability.

    Science.gov (United States)

    Hao, Pin; Tian, Jian; Sang, Yuanhua; Tuan, Chia-Chi; Cui, Guanwei; Shi, Xifeng; Wong, C P; Tang, Bo; Liu, Hong

    2016-09-15

    The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo 2 S 4 nanotube array/carbon aerogel and NiCo 2 O 4 nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo 2 S 4 nanotube array/carbon aerogel and NiCo 2 O 4 nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg -1 and 47.5 Wh kg -1 at a power density of 400 W kg -1 , respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

  1. A binder-free sulfur/reduced graphene oxide aerogel as high performance electrode materials for lithium sulfur batteries

    Science.gov (United States)

    Nitze, Florian; Agostini, Marco; Lundin, Filippa; Palmqvist, Anders E. C.; Matic, Aleksandar

    2016-12-01

    Societies’ increasing need for energy storage makes it necessary to explore new concepts beyond the traditional lithium ion battery. A promising candidate is the lithium-sulfur technology with the potential to increase the energy density of the battery by a factor of 3-5. However, so far the many problems with the lithium-sulfur system have not been solved satisfactory. Here we report on a new approach utilizing a self-standing reduced graphene oxide based aerogel directly as electrodes, i.e. without further processing and without the addition of binder or conducting agents. We can thereby disrupt the common paradigm of “no battery without binder” and can pave the way to a lithium-sulfur battery with a high practical energy density. The aerogels are synthesized via a one-pot method and consist of more than 2/3 sulfur, contained inside a porous few-layered reduced graphene oxide matrix. By combining the graphene-based aerogel cathode with an electrolyte and a lithium metal anode, we demonstrate a lithium-sulfur cell with high areal capacity (more than 3 mAh/cm2 after 75 cycles), excellent capacity retention over 200 cycles and good sulfur utilization. Based on this performance we estimate that the energy density of this concept-cell can significantly exceed the Department of Energy (DEO) 2020-target set for transport applications.

  2. Novel synthesis of tin oxide/graphene aerogel nanocomposites as anode materials for lithium ion batteries

    International Nuclear Information System (INIS)

    Wu, Zheyu; Li, Xifei; Tai, Limin; Song, Haoze; Zhang, Yiyan; Yan, Bo; Fan, Linlin; Shan, Hui; Li, Dejun

    2015-01-01

    A novel method of mechanical exfoliation followed by hydrothermal approach was proposed to synthesize the tin oxide/graphene aerogels (SnO 2 /GAs) nanocomposites. Homogeneous distribution of SnO 2 nanocrystals on GAs was confirmed by SEM, XRD and TEM characterization. It was found that optimized exfoliation of the SnS 2 is the key factor to obtain high electrochemical lithiation/delithiation performance of the anodes. The as-prepared SnO 2 /GA nanocomposites exhibited high reversible capacity (up to 1086.7 mAh g −1 after 100 cycles) and excellent cycling stability. The improved rate capability was also obtained, for instance, the reversible capacity at a current density of 800 mA g −1 is over 447.9 mAh g −1 , and then recovered to as high as 784.4 mAh g −1 at a current density of 100 mA g −1 . - Highlights: • A novel approach was employed to synthesize the SnO 2 /GA nanocomposites. • The designed SnO 2 /GAs exhibited high reversible capacity and excellent cycling stability. • The volume change challenge of SnO 2 was markedly alleviated by the GA matrix. • The novel synthesis method can be extended for other materials in lithium ion batteries

  3. One-Step Preparation of Graphene Oxide/Cellulose Nanofibril Hybrid Aerogel for Adsorptive Removal of Four Kinds of Antibiotics

    Directory of Open Access Journals (Sweden)

    Jin Wang

    2017-01-01

    Full Text Available Via a one-step ultrasonication method, cellulose nanofibril/graphene oxide hybrid (GO-CNF aerogel was successfully prepared. The as-prepared GO-CNF possessed interconnected 3D network microstructure based on GO nanosheets grown along CNF through hydrogen bonds. The aerogel exhibited superior adsorption capacity toward four kinds of antibiotics. The removal percentages (R% of these antibiotics were 81.5%, 79.5%, 79.1%, and 73.9% for Doxycycline (DXC, Chlortetracycline (CTC, Oxytetracycline (OTC, and tetracycline (TC, respectively. Simultaneously, the adsorption isotherms were well fitted to Langmuir model and kinetics study implied that the adsorption process was attributed to pseudo-second-order model. The maximum theoretical adsorption capacities of GO-CNF were 469.7, 396.5, 386.5, and 343.8 mg·g−1 for DXC, CTC, OTC, and TC, respectively, calculated by the Langmuir isotherm models. After five cycles, importantly, the regenerated aerogels still could be used with little degradation of adsorption property. Consequently, the as-synthesized GO-CNF was a successful application of effective removal of antibiotics.

  4. Synthesis of well-dispersed magnetic CoFe2O4 nanoparticles in cellulose aerogels via a facile oxidative co-precipitation method.

    Science.gov (United States)

    Wan, Caichao; Li, Jian

    2015-12-10

    With the increasing emphasis on green chemistry, it is becoming more important to develop environmentally friendly matrix materials for the synthesis of nanocomposites. Cellulose aerogels with hierarchical micro/nano-scale three-dimensional network beneficial to control and guide the growth of nanoparticles, are suitable as a class of ideal green nanoparticles hosts to fabricate multifunctional nanocomposites. Herein, a facile oxidative co-precipitation method was carried out to disperse CoFe2O4 nanoparticles in the cellulose aerogels matrixes, and the cellulose aerogels were prepared from the native wheat straw based on a green NaOH/polyethylene glycol solution. The mean diameter of the well-dispersed CoFe2O4 nanoparticles in the hybrid aerogels is 98.5 nm. Besides, the hybrid aerogels exhibit strong magnetic responsiveness, which could be flexibly actuated by a small magnet. And this feature also makes this class of magnetic aerogels possibly useful as recyclable adsorbents and some magnetic devices. Meanwhile, the mild green preparation method could also be extended to fabricate other miscellaneous cellulose-based nanocomposites. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Mechanically Strong, Polymer Cross-linked Aerogels (X-Aerogels)

    Science.gov (United States)

    Leventis, Nicholas

    2006-01-01

    have been demonstrated with several polymers such as polyurethanes/polyureas, epoxies and polyolefins, while crosslinking of approximately 35 different oxide aerogels yields a range of dimensionally stable, porous lightweight materials with unique combinations of structural, magnetic and optical properties. The main theme in materials development for space exploration is multifunction. For example, use of one material for thermal insulation/structural component will free weight for useful payload. In that regard, X-aerogels are evaluated at NASA for cryogenic fuel storage tanks and for spacesuits. Along the same lines, major impact fro X-Aerogels is also expected in commercial applications for thermal/acoustic insulation, in catalytic reformers and converters, in filtration membranes and membranes for fuel cells, as platforms for optical, electrical and magnetic sensors, and as lightweight structural component for aircraft and satellites.

  6. Carbon aerogels

    International Nuclear Information System (INIS)

    Berthon-Fabry, S.; Achard, P.

    2003-06-01

    The carbon aerogel is a nano-porous material at open porosity, electrical conductor. The aerogels morphology is variable in function of the different synthesis parameters. This characteristic offers to the aerogels a better adaptability to many applications: electrodes (super condensers, fuel cells). The author presents the materials elaboration and their applications. It provides also the research programs: fundamental research, realization of super-condenser electrodes, fuel cells electrodes, gas storage materials and opaque materials for thermal insulation. (A.L.B.)

  7. Silica Aerogels Doped with Ru(II) Tris 1,l0-Phenanthro1ine)-Electron Acceptor Dyads: Improving the Dynamic Range, Sensitivity and Response Time of Sol-Gel Based Oxygen Sensors

    Science.gov (United States)

    Kevebtusm Bucgikas; Rawashdeh, Abdel M.; Elder, Ian A.; Yang, Jinhua; Dass, Amala; Sotiriou-Leventis, Chariklia

    2005-01-01

    Complexes 1 and 2 were characterized in fluid and frozen solution and as dopants of silica aerogels. The intramolecular quenching efficiency of pendant 4-benzoyl-N-methylpyridinium group (4BzPy) is solvent dependent: emission is quenched completely in acetonitrile but not in alcohols. On the other hand, N-benzyl-N'-methylviologen (BzMeV) quenches the emission in all solvents completely. The differences are traced electrochemically to a stronger solvation effect by the alcohol in the case of 1. In fiozen matrices or absorbed on the surfaces of silica aerogel, both 1 and 2 are photoluminescent. The lack of quenching has been traced to the environmental rigidity. When doped aerogels are cooled to 77K, the emission shifts to the blue and its intensity increases in analogy to what is observed with Ru(II) complexes in media undergoing fluid-to-rigid transition. The photoluminescence of 1 and 2 from the aerogel is quenched by oxygen diffusing through the pores. In the presence of oxygen, aerogels doped with 1 can modulate their emission over a wider dynamic range than aerogels doped with 2, and both are more sensitive than aerogels doped with Ru(II) tris(1,l0- phenanthroline). In contrast to frozen solutions, the luminescent moieties in the bulk of aerogels kept at 77K are still accessible, leading to more sensitive platforms for oxygen sensors than other ambient temperature configurations.

  8. Tin Oxide/Graphene Aerogel Nanocomposites Building Superior Rate Capability for Lithium Ion Batteries

    International Nuclear Information System (INIS)

    Fan, Linlin; Li, Xifei; Cui, Yanhua; Xu, Hui; Zhang, Xianfa; Xiong, Dongbin; Yan, Bo; Wang, Yufen; Li, Dejun

    2015-01-01

    Highlights: • The SnO 2 /GA nanocomposites were successfully synthesized via a hydrothermal method. • The performance of nanocomposite anodes highly depended on the hydrothermal time. • The 3-4 nm-sized SnO 2 /GAs showed enhanced cycling performance and rate performance. - Abstract: SnO 2 has attracted intense interest for use as an anode material for lithium ion batteries because of various advantages of the high theoretical capacity and low-cost. Unfortunately, SnO 2 anode material suffers from the huge volume change and poor electrical conductivity. In order to address these problems, in this work, SnO 2 /graphene aerogel composites have been successfully synthesized by a facile hydrothermal approach. 3-4 nm-sized SnO 2 nanoparticles are uniformly dispersed over graphene aerogels. Our results indicate that the hydrothermal reaction time highly affects the electrode performance of the anodes. The nanocomposite electrode with reaction time of 3 h shows increased electrochemical performance with high energy capacity, long cycle life, and superior rate capability. After 100 cycles, it can deliver a high discharge capacity of 662 mAh g −1 at 100 mA g −1 . At 500 mA g −1 , it can still yield a discharge capacity of 619.7 mAh g −1 after 723 cycles. The performance improvement can attribute to the graphene aerogel, which can suppress the aggregation of SnO 2 nanoparticles, enhance the conductivity of SnO 2 , and increase their structural stability during cycling. This study strongly demonstrates that the SnO 2 /graphene aerogel composite is a promising anode material building high performance lithium ion batteries

  9. A facile method of preparing LiMnPO4/reduced graphene oxide aerogel as cathodic material for aqueous lithium-ion hybrid supercapacitors

    Science.gov (United States)

    Xu, Lin; Wang, Senlin; Zhang, Xiao; He, Taobin; Lu, Fengxia; Li, Huichang; Ye, Junhui

    2018-01-01

    A facile method of preparing LiMnPO4/reduced graphene oxide aerogel (LMP/rGO) as cathodic material was reported here. LiMnPO4 nano-particles were prepared using a facile polyvinyl pyrrolidone-assisted solvothermal route. Then LMP/rGO aerogel was prepared using the accessible restacking method. The influence of the cathodic electrode composition (ratio of rGO to LiMnPO4) on the performance of the LMP/rGO was evaluated by constant-current discharge tests. When compared with 217C g-1 for the pristine LMP, the best LMP/rGO (the content of rGO is 27.3 wt%) exhibits a higher capacity of 464.5C g-1 (at 0.5 A g-1), which presenting the capacity enhance of 114%. Moreover, a lithium-ion hybrid supercapacitor (LIHS) was successfully assembled by using LMP/rGO aerogel as the cathodic electrode and rGO aerogel as the anodic electrode. The LMP/rGO//rGO device achieves excellent specific energy of 16.46 W h kg-1 at a power density of 0.38 kW kg-1, even under the higher specific power of 4.52 kW kg-1, there still holds the specific energy of 11.79 W h kg-1. The LMP/rGO//rGO device maintains 91.2% of the initial capacity after 10,000 cycles (at 2 A g-1), which displays high rate performance and long cycle life. The 3D LMP/rGO aerogel could be a promising candidate material for the lithium-ion hybrid supercapacitors.

  10. Electrospinning of polymer-aerogel composite fibres

    DEFF Research Database (Denmark)

    Christiansen, Lasse; Fojan, Peter

    En poster om produktion af polymer-aerogel kompositfibre ved hjælp af elektrospinning. Fiberne er produceret fra en opløsning af aerogel og polyethylene oxide i vand, som er elektrospundet gennem en enkeltnålsprocess....

  11. Aerogel sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Begag, Redouane; Rhine, Wendell E.; Dong, Wenting

    2018-04-03

    The current invention describes methods and compositions of various sorbents based on aerogels of various silanes and their use as sorbent for carbon dioxide. Methods further provide for optimizing the compositions to increase the stability of the sorbents for prolonged use as carbon dioxide capture matrices.

  12. Development of a 144-channel Hybrid Avalanche Photo-Detector for Belle II ring-imaging Cherenkov counter with an aerogel radiator

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, S., E-mail: shohei.nishida@kek.jp [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Adachi, I. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Hamada, N. [Toho University, Funabashi (Japan); Hara, K. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Iijima, T. [Nagoya University, Nagoya (Japan); Iwata, S.; Kakuno, H. [Tokyo Metropolitan University, Hachioji (Japan); Kawai, H. [Chiba University, Chiba (Japan); Korpar, S.; Krizan, P. [Jozef Stefan Institute, Ljubljana (Slovenia); Ogawa, S. [Toho University, Funabashi (Japan); Pestotnik, R.; Ŝantelj, L.; Seljak, A. [Jozef Stefan Institute, Ljubljana (Slovenia); Sumiyoshi, T. [Tokyo Metropolitan University, Hachioji (Japan); Tabata, M. [Chiba University, Chiba (Japan); Tahirovic, E. [Jozef Stefan Institute, Ljubljana (Slovenia); Yoshida, K. [Tokyo Metropolitan University, Hachioji (Japan); Yusa, Y. [Niigata University, Niigata (Japan)

    2015-07-01

    The Belle II detector, a follow up of the very successful Belle experiment, is under construction at the SuperKEKB electron–positron collider at KEK in Japan. For the PID system in the forward region of the spectrometer, a proximity-focusing ring-imaging Cherenkov counter with an aerogel radiator is being developed. For the position sensitive photon sensor, a 144-channel Hybrid Avalanche Photo-Detector has been developed with Hamamatsu Photonics K.K. In this report, we describe the specification of the Hybrid Avalanche Photo-Detector and the status of the mass production.

  13. Nano-Sized Structurally Disordered Metal Oxide Composite Aerogels as High-Power Anodes in Hybrid Supercapacitors.

    Science.gov (United States)

    Huang, Haijian; Wang, Xing; Tervoort, Elena; Zeng, Guobo; Liu, Tian; Chen, Xi; Sologubenko, Alla; Niederberger, Markus

    2018-03-27

    A general method for preparing nano-sized metal oxide nanoparticles with highly disordered crystal structure and their processing into stable aqueous dispersions is presented. With these nanoparticles as building blocks, a series of nanoparticles@reduced graphene oxide (rGO) composite aerogels are fabricated and directly used as high-power anodes for lithium-ion hybrid supercapacitors (Li-HSCs). To clarify the effect of the degree of disorder, control samples of crystalline nanoparticles with similar particle size are prepared. The results indicate that the structurally disordered samples show a significantly enhanced electrochemical performance compared to the crystalline counterparts. In particular, structurally disordered Ni x Fe y O z @rGO delivers a capacity of 388 mAh g -1 at 5 A g -1 , which is 6 times that of the crystalline sample. Disordered Ni x Fe y O z @rGO is taken as an example to study the reasons for the enhanced performance. Compared with the crystalline sample, density functional theory calculations reveal a smaller volume expansion during Li + insertion for the structurally disordered Ni x Fe y O z nanoparticles, and they are found to exhibit larger pseudocapacitive effects. Combined with an activated carbon (AC) cathode, full-cell tests of the lithium-ion hybrid supercapacitors are performed, demonstrating that the structurally disordered metal oxide nanoparticles@rGO||AC hybrid systems deliver high energy and power densities within the voltage range of 1.0-4.0 V. These results indicate that structurally disordered nanomaterials might be interesting candidates for exploring high-power anodes for Li-HSCs.

  14. Evacuated aerogel glazings

    DEFF Research Database (Denmark)

    Schultz, Jørgen Munthe; Jensen, Karsten Ingerslev

    2008-01-01

    This paper describes the main characteristics of monolithic silica aerogel and its application in evacuated superinsulating aerogel glazing including the evacuation and assembling process. Furthermore, the energetic benefit of aerogel glazing is quantified. In evacuated aerogel glazing the space ......) combined with a solar energy transmittance above 0.75.......This paper describes the main characteristics of monolithic silica aerogel and its application in evacuated superinsulating aerogel glazing including the evacuation and assembling process. Furthermore, the energetic benefit of aerogel glazing is quantified. In evacuated aerogel glazing the space...... between the glass panes is filled with monolithic silica aerogel evacuated to a rough vacuum of approximately 1-10 hPa. The aerogel glazing does not depend on use of low emissive coatings that have the drawback of absorbing a relatively large part of the solar radiation that otherwise could reduce...

  15. Three-Dimensional Zn0.5Cd0.5S/Reduced Graphene Oxide Hybrid Aerogel: Facile Synthesis and the Visible-Light-Driven Photocatalytic Property for Reduction of Cr(VI in Water

    Directory of Open Access Journals (Sweden)

    Wei Xiao

    2016-01-01

    Full Text Available A series of three-dimensional ZnxCd1-xS/reduced graphene oxide (ZnxCd1-xS/RGO hybrid aerogels was successfully synthesized based on a one-pot hydrothermal approach, which were subsequently used as visible-light-driven photocatalysts for photoreduction of Cr(VI in water. Over 95% of Cr(VI was photoreduced by Zn0.5Cd0.5S/RGO aerogel material within 140 min, and such photocatalytic performance was superior to that of other ZnxCd1-xS/RGO aerogel materials (x≠0.5 and bare Zn0.5Cd0.5S. It was assumed that the enhanced photocatalytic activity of Zn0.5Cd0.5S/RGO aerogel was attributed to its high specific surface area and the preferable synergetic catalytic effect between Zn0.5Cd0.5S and RGO. Besides, Zn0.5Cd0.5S/RGO aerogel materials were robust and durable enough so that they could be reused several times with merely limited loss of photocatalytic activity. The chemical composition, phase, structure, and morphology of Zn0.5Cd0.5S/RGO aerogel material were carefully examined by a number of techniques like XRD, SEM, TEM, BET, Raman characterizations, and so on. It was found that Zn0.5Cd0.5S/RGO aerogel possessed hierarchically porous architecture with the specific surface area as high as 260.8 m2 g−1. The Zn0.5Cd0.5S component incorporated in Zn0.5Cd0.5S/RGO aerogel existed in the form of solid solution nanoparticles, which were uniformly distributed in the RGO matrix.

  16. Synergetic Hybrid Aerogels of Vanadia and Graphene as Electrode Materials of Supercapacitors

    Directory of Open Access Journals (Sweden)

    Xuewei Fu

    2016-08-01

    Full Text Available The performance of synergetic hybrid aerogel materials of vanadia and graphene as electrode materials in supercapacitors was evaluated. The hybrid materials were synthesized by two methods. In Method I, premade graphene oxide (GO hydrogel was first chemically reduced by L-ascorbic acid and then soaked in vanadium triisopropoxide solution to obtain V2O5 gel in the pores of the reduced graphene oxide (rGO hydrogel. The gel was supercritically dried to obtain the hybrid aerogel. In Method II, vanadium triisopropoxide was hydrolyzed from a solution in water with GO particles uniformly dispersed to obtain the hybrid gel. The hybrid aerogel was obtained by supercritical drying of the gel followed by thermal reduction of GO. The electrode materials were prepared by mixing 80 wt % hybrid aerogel with 10 wt % carbon black and 10 wt % polyvinylidene fluoride. The hybrid materials in Method II showed higher capacitance due to better interactions between vanadia and graphene oxide particles and more uniform vanadia particle distribution.

  17. Charge storage mechanisms of manganese oxide nanosheets and N-doped reduced graphene oxide aerogel for high-performance asymmetric supercapacitors

    Science.gov (United States)

    Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Seubsai, Anusorn; Chanlek, Narong; Kidkhunthod, Pinit; Sangthong, Winyoo; Maensiri, Santi; Yimnirun, Rattikorn; Nilmoung, Sukanya; Pannopard, Panvika; Ittisanronnachai, Somlak; Kongpatpanich, Kanokwan; Limtrakul, Jumras; Sawangphruk, Montree

    2016-11-01

    Although manganese oxide- and graphene-based supercapacitors have been widely studied, their charge storage mechanisms are not yet fully investigated. In this work, we have studied the charge storage mechanisms of K-birnassite MnO2 nanosheets and N-doped reduced graphene oxide aerogel (N-rGOae) using an in situ X-ray absorption spectroscopy (XAS) and an electrochemical quart crystal microbalance (EQCM). The oxidation number of Mn at the MnO2 electrode is +3.01 at 0 V vs. SCE for the charging process and gets oxidized to +3.12 at +0.8 V vs. SCE and then reduced back to +3.01 at 0 V vs. SCE for the discharging process. The mass change of solvated ions, inserted to the layers of MnO2 during the charging process is 7.4 μg cm-2. Whilst, the mass change of the solvated ions at the N-rGOae electrode is 8.4 μg cm-2. An asymmetric supercapacitor of MnO2//N-rGOae (CR2016) provides a maximum specific capacitance of ca. 467 F g-1 at 1 A g-1, a maximum specific power of 39 kW kg-1 and a specific energy of 40 Wh kg-1 with a wide working potential of 1.6 V and 93.2% capacity retention after 7,500 cycles. The MnO2//N-rGOae supercapacitor may be practically used in high power and energy applications.

  18. Charge storage mechanisms of manganese oxide nanosheets and N-doped reduced graphene oxide aerogel for high-performance asymmetric supercapacitors

    Science.gov (United States)

    Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Seubsai, Anusorn; Chanlek, Narong; Kidkhunthod, Pinit; Sangthong, Winyoo; Maensiri, Santi; Yimnirun, Rattikorn; Nilmoung, Sukanya; Pannopard, Panvika; Ittisanronnachai, Somlak; Kongpatpanich, Kanokwan; Limtrakul, Jumras; Sawangphruk, Montree

    2016-01-01

    Although manganese oxide- and graphene-based supercapacitors have been widely studied, their charge storage mechanisms are not yet fully investigated. In this work, we have studied the charge storage mechanisms of K-birnassite MnO2 nanosheets and N-doped reduced graphene oxide aerogel (N-rGOae) using an in situ X-ray absorption spectroscopy (XAS) and an electrochemical quart crystal microbalance (EQCM). The oxidation number of Mn at the MnO2 electrode is +3.01 at 0 V vs. SCE for the charging process and gets oxidized to +3.12 at +0.8 V vs. SCE and then reduced back to +3.01 at 0 V vs. SCE for the discharging process. The mass change of solvated ions, inserted to the layers of MnO2 during the charging process is 7.4 μg cm−2. Whilst, the mass change of the solvated ions at the N-rGOae electrode is 8.4 μg cm−2. An asymmetric supercapacitor of MnO2//N-rGOae (CR2016) provides a maximum specific capacitance of ca. 467 F g−1 at 1 A g−1, a maximum specific power of 39 kW kg−1 and a specific energy of 40 Wh kg−1 with a wide working potential of 1.6 V and 93.2% capacity retention after 7,500 cycles. The MnO2//N-rGOae supercapacitor may be practically used in high power and energy applications. PMID:27857225

  19. Carbon aerogels; Les aerogels de carbone

    Energy Technology Data Exchange (ETDEWEB)

    Berthon-Fabry, S.; Achard, P

    2003-06-15

    The carbon aerogel is a nano-porous material at open porosity, electrical conductor. The aerogels morphology is variable in function of the different synthesis parameters. This characteristic offers to the aerogels a better adaptability to many applications: electrodes (super condensers, fuel cells). The author presents the materials elaboration and their applications. It provides also the research programs: fundamental research, realization of super-condenser electrodes, fuel cells electrodes, gas storage materials and opaque materials for thermal insulation. (A.L.B.)

  20. Efficient laser-induced 6-8 keV x-ray production from iron oxide aerogel and foil-lined cavity targets

    Energy Technology Data Exchange (ETDEWEB)

    Pérez, F.; Kay, J. J.; Patterson, J. R.; Kane, J.; Villette, B.; Girard, F.; Reverdin, C.; May, M.; Emig, J.; Sorce, C.; Colvin, J.; Gammon, S.; Jaquez, J.; Satcher, J. H.; Fournier, K. B.

    2012-08-01

    The performance of new iron-based laser-driven x-ray sources has been tested at the OMEGA laser facility for production of x rays in the 6.5–8.5 keV range. Two types of targets were experimentally investigated: low-density iron oxide aerogels (density 6-16 mg/cm36-16 mg/cm3) and stainless steel foil-lined cavity targets (steel thickness 1-5 μm1-5 μm). The targets were irradiated by 40 beams of the OMEGA laser (500 J/beam, 1 ns pulse, wavelength 351 nm). All targets showed good coupling with the laser, with <5%<5% of the incident laser light backscattered by the resulting plasma in all cases (typically <2.5%<2.5%). The aerogel targets produced Te=2Te=2 to 3 keV, ne=0.12-0.2ne=0.12-0.2 critical density plasmas yielding a 40%–60% laser-to-x-ray total conversion efficiency (CE) (1.2%–3% in the Fe K-shell range). The foil cavity targets produced Te~2 keV, Te~2 keV, ne~0.15ne~0.15 critical density plasmas yielding a 60%–75% conversion efficiency (1.6%–2.2% in the Fe K-shell range). Time-resolved images illustrate that the volumetric heating of low-density aerogels allow them to emit a higher K-shell x-ray yield even though they contain fewer Fe atoms. However, their challenging fabrication process leads to a larger shot-to-shot variation than cavity targets.

  1. Mechanical Reinforcement, Shapestabilization and Thermal Improvement of Phase-Change Energy Storage Materials Using Graphene Oxide Aerogel

    Science.gov (United States)

    Schuman, Yue Xu

    Paraffin is known as a good energy storage phase change material (PCM) because of its high energy storage capacity and low cost. However, the leakage of liquid paraffin beyond its melting point and its low thermal conductivity hinder applications of paraffin in energy storage systems. Recently, nanomaterials have been used to create PCM composites in order to enhance their thermal properties while shape stabilizing the PCMs. However, fundamental studies on the material structures and mechanical behavior of the thermally enhanced PCM composites are limited especially at the nanoscale. In this study, we developed a PCM composite using graphene oxide aerogel (GOxA) as the reinforcing 3D network. The GOxA functions thermally as a heat transfer path and mechanically as a nanofiller to reinforce the PCM matrix. We characterized the morphology, the crystal and molecular structures as well as the multiscale mechanical and thermal behavior of the GOxA-PCM composite to evaluate the role of GOxA in the PCM composite. The molecular and diffraction characterizations imply that the GOxA network may affect the paraffin's crystallization, potentially forming an interfacial phase at the surfaces of GOxA. Furthermore, the mechanical properties were studied using nanoindentation at the nano/microscale and a digital durometer at the macroscale from 25degree C to 80 degree C. The mechanical characterizations show that the GOxA-PCM composite is 3 7x harder than pure paraffin and maintains significant strength even above paraffin's melting point due to the support from the GoxA. Moreover, the composite is much less strain-rate sensitive than paraffin. The reinforcement via GOxA is much beyond the prediction by the rule of mixture, implying a strong GOxA-paraffin interfacial bonding. Finally, a thermal scanning microscopy (SThM) along with AFM was used to study the thermal properties at microscale. AFM and thermal images indicate that GOxA-PCM has a better thermal conductivity. The latent

  2. Oxidation of Fe(II) in rainwater.

    Science.gov (United States)

    Willey, J D; Whitehead, R F; Kieber, R J; Hardison, D R

    2005-04-15

    Photochemically produced Fe(II) is oxidized within hours under environmentally realistic conditions in rainwater. The diurnal variation between photochemical production and reoxidation of Fe(II) observed in our laboratory accurately mimics the behavior of ferrous iron observed in field studies where the highest concentrations of dissolved Fe(ll) occur in afternoon rain during the period of maximum sunlight intensity followed by gradually decreasing concentrations eventually returning to early morning pre-light values. The experimental work presented here, along with the results of kinetics studies done by others, suggests thatthe primary process responsible for the decline in photochemically produced Fe(II) concentrations is oxidation by hydrogen peroxide. This reaction is first order with respect to both the concentrations of Fe(II) and H2O2. The second-order rate constant determined for six different authentic rain samples varied over an order of magnitude and was always less than or equal to the rate constant determined for this reaction in simple acidic solutions. Oxidation of photochemically produced ferrous iron by other oxidants including molecular oxygen, ozone, hydroxyl radical, hydroperoxyl/superoxide radical, and hexavalent chromium were found to be insignificant under the conditions present in rainwater. This study shows that Fe(II) occurs as at least two different chemical species in rain; photochemically produced Fe(II) that is oxidized over time periods of hours, and a background Fe(II) that is protected against oxidation, perhaps by organic complexation, and is stable against oxidation for days. Because the rate of oxidation of photochemically produced Fe(II) does not increase with increasing rainwater pH, the speciation of this more labile form of Fe(II) is also not controlled by simple hydrolysis reactions.

  3. Complete oxidation of 1,2-dichlorobenzene over V{sub 2}O{sub 5}-TiO{sub 2} and MnO{sub x}-TiO{sub 2} aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jinsoon [Research Institute of Industrial Science and Technology, Pohang (Korea, Republic of); Suh, Dong Jin [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2014-10-15

    Catalytic destruction of 1,2-dichlorobenzene was carried out over two types of aerogels, vanadia-titania and manganese oxide-titania. Reactions were performed in a plug flow reactor in the range of 150-600 .deg. C. Both catalysts resulted in very high selectivity to carbon oxides and produced negligible amount of hydrocarbon byproducts. Over the vanadia-titania catalysts, the chlorinated compound was relatively more efficiently destructed at lower temperature, while selectivity towards carbon dioxide was much higher over manganese oxide-titania aerogel catalysts. Regardless of the preparation methods, showed a tendency to produce carbon monoxide with 35-45% selectivity throughout the reaction temperature range while manganese oxide-titania exhibited more than 90% CO{sub 2} selectivity at above 400 .deg. C.

  4. Ambient Dried Aerogels

    Science.gov (United States)

    Jones, Steven M.; Paik, Jong-Ah

    2013-01-01

    A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

  5. Aerogel nanocomposite materials

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, A.J.; Ayers, M.; Cao, W. [Lawrence Berkeley Laboratory, CA (United States)] [and others

    1995-05-01

    Aerogels are porous, low density, nanostructured solids with many unusual properties including very low thermal conductivity, good transparency, high surface area, catalytic activity, and low sound velocity. This research is directed toward developing new nanocomposite aerogel materials for improved thermal insulation and several other applications. A major focus of the research has been to further increase the thermal resistance of silica aerogel by introducing infrared opacification agents into the aerogel to produce a superinsulating composite material. Opacified superinsulating aerogel permit a number of industrial applications for aerogel-based insulation. The primary benefits from this recently developed superinsulating composite aerogel insulation are: to extend the range of applications to higher temperatures, to provide a more compact insulation for space sensitive-applications, and to lower costs of aerogel by as much as 30%. Superinsulating aerogels can replace existing CFC-containing polyurethane in low temperature applications to reduce heat losses in piping, improve the thermal efficiency of refrigeration systems, and reduce energy losses in a variety of industrial applications. Enhanced aerogel insulation can also replace steam and process pipe insulation in higher temperature applications to substantially reduce energy losses and provide much more compact insulation.

  6. Mechanically Strong Lightweight Materials for Aerospace Applications (x-aerogels)

    Science.gov (United States)

    Leventis, Nicholas

    2005-01-01

    The X-Aerogel is a new NASA-developed strong lightweight material made by reacting the mesoporous surfaces of 3-D networks of inorganic nanoparticles with polymeric crosslinkers. Since the relative amount of the crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by templated casting of polymeric precursors on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralightweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the thermal conductivity of styrofoam. XAerogels have been demonstrated with several polymers such as polyurethanes/polyureas, epoxies and polyolefins, while crosslinking of approximately 35 different oxide aerogels yields a wide variety of dimensionally stable, porous lightweight materials with interesting structural, magnetic and optical properties. X-Aerogels are evaluated for cryogenic rocket fuel storage tanks and for Advanced EVA suits, where they will play the dual role of the thermal insulator/structural material. Along the same lines, major impact is also expected by the use of X-Aerogels in structural components/thermal protection for small satellites, spacecrafts, planetary vehicles and habitats.

  7. Technical applications of aerogels

    International Nuclear Information System (INIS)

    Hrubesh, L.W.

    1997-01-01

    Aerogel materials posses such a wide variety of exceptional properties that a striking number of applications have developed for them. Many of the commercial applications of aerogels such as catalysts, thermal insulation, windows, and particle detectors are still under development and new application as have been publicized since the ISA4 Conference in 1994: e.g.; supercapacitors, insulation for heat storage in automobiles, electrodes for capacitive deionization, etc. More applications are evolving as the scientific and engineering community becomes familiar with the unusual and exceptional physical properties of aerogels, there are also scientific and technical application, as well. This paper discusses a variety of applications under development at Lawrence Livermore National Laboratory for which several types of aerogels are formed in custom sizes and shapes. Particular discussions will focus on the uses of aerogels for physics experiments which rely on the exceptional, sometimes unique, properties of aerogels

  8. Flexible Carbon Aerogels

    Directory of Open Access Journals (Sweden)

    Marina Schwan

    2016-09-01

    Full Text Available Carbon aerogels are highly porous materials with a large inner surface area. Due to their high electrical conductivity they are excellent electrode materials in supercapacitors. Their brittleness, however, imposes certain limitations in terms of applicability. In that context, novel carbon aerogels with varying degree of flexibility have been developed. These highly porous, light aerogels are characterized by a high surface area and possess pore structures in the micrometer range, allowing for a reversible deformation of the aerogel network. A high ratio of pore size to particle size was found to be crucial for high flexibility. For dynamic microstructural analysis, compression tests were performed in-situ within a scanning electron microscope allowing us to directly visualize the microstructural flexibility of an aerogel. The flexible carbon aerogels were found to withstand between 15% and 30% of uniaxial compression in a reversible fashion. These findings might stimulate further research and new application fields directed towards flexible supercapacitors and batteries.

  9. Polyolefin-Based Aerogels

    Science.gov (United States)

    Lee, Je Kyun; Gould, George

    2012-01-01

    An organic polybutadiene (PB) rubberbased aerogel insulation material was developed that will provide superior thermal insulation and inherent radiation protection, exhibiting the flexibility, resiliency, toughness, and durability typical of the parent polymer, yet with the low density and superior insulation properties associated with the aerogels. The rubbery behaviors of the PB rubber-based aerogels are able to overcome the weak and brittle nature of conventional inorganic and organic aerogel insulation materials. Additionally, with higher content of hydrogen in their structure, the PB rubber aerogels will also provide inherently better radiation protection than those of inorganic and carbon aerogels. Since PB rubber aerogels also exhibit good hydrophobicity due to their hydrocarbon molecular structure, they will provide better performance reliability and durability as well as simpler, more economic, and environmentally friendly production over the conventional silica or other inorganic-based aerogels, which require chemical treatment to make them hydrophobic. Inorganic aerogels such as silica aerogels demonstrate many unusual and useful properties. There are several strategies to overcoming the drawbacks associated with the weakness and brittleness of silica aerogels. Development of the flexible fiber-reinforced silica aerogel composite blanket has proven one promising approach, providing a conveniently fielded form factor that is relatively robust toward handling in industrial environments compared to silica aerogel monoliths. However, the flexible silica aerogel composites still have a brittle, dusty character that may be undesirable, or even intolerable, in certain applications. Although the cross-linked organic aerogels such as resorcinol-formaldehyde (RF), polyisocyanurate, and cellulose aerogels show very high impact strength, they are also very brittle with little elongation (i.e., less rubbery). Also, silica and carbon aerogels are less efficient

  10. High-Performance Asymmetric Supercapacitors of MnCo2O4 Nanofibers and N-Doped Reduced Graphene Oxide Aerogel.

    Science.gov (United States)

    Pettong, Tanut; Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Sukha, Phansiri; Sirisinudomkit, Pichamon; Seubsai, Anusorn; Chareonpanich, Metta; Kongkachuichay, Paisan; Limtrakul, Jumras; Sawangphruk, Montree

    2016-12-14

    The working potential of symmetric supercapacitors is not so wide because one type of material used for the supercapacitor electrodes prefers either positive or negative charge to both charges. To address this problem, a novel asymmetrical supercapacitor (ASC) of battery-type MnCo 2 O 4 nanofibers (NFs)//N-doped reduced graphene oxide aerogel (N-rGO AE ) was fabricated in this work. The MnCo 2 O 4 NFs at the positive electrode store the negative charges, i.e., solvated OH - , while the N-rGO AE at the negative electrode stores the positive charges, i.e., solvated K + . An as-fabricated aqueous-based MnCo 2 O 4 //N-rGO AE ASC device can provide a wide operating potential of 1.8 V and high energy density and power density at 54 W h kg -1 and 9851 W kg -1 , respectively, with 85.2% capacity retention over 3000 cycles. To understand the charge storage reaction mechanism of the MnCo 2 O 4 , the synchrotron-based X-ray absorption spectroscopy (XAS) technique was also used to determine the oxidation states of Co and Mn at the MnCo 2 O 4 electrode after being electrochemically tested. The oxidation number of Co is oxidized from +2.76 to +2.85 after charging and reduced back to +2.75 after discharging. On the other hand, the oxidation state of Mn is reduced from +3.62 to +3.44 after charging and oxidized to +3.58 after discharging. Understanding in the oxidation states of Co and Mn at the MnCo 2 O 4 electrode here leads to the awareness of the uncertain charge storage mechanism of the spinel-type oxide materials. High-performance ASC here in this work may be practically used in high-power applications.

  11. Self-assembled 3D ZnSnO3 hollow cubes@reduced graphene oxide aerogels as high capacity anode materials for lithium-ion batteries

    International Nuclear Information System (INIS)

    Wang, Yankun; Li, Dan; Liu, Yushan; Zhang, Jianmin

    2016-01-01

    Highlights: • 3D ZnSnO 3 hollow cubes@reducedgrapheneoxideaerogels(ZGAs) were fabricated. • The electrochemical properties of ZGAs were investigated for LIBs. • ZGAs demonstrated superior lithium storage performance. - Abstract: 3D ZnSnO 3 hollow cubes@reduced graphene oxide aerogels (ZGAs) were fabricated via a colloid electrostatic self-assembly method between the graphene oxide (GO) nanosheets and poly(diallyldimethylammonium chloride) (PDDA) modified ZnSnO 3 hollow cubes colloid, followed by hydrothermal and freeze-drying treatments. The unique porous architecture of ZnSnO 3 hollow cubes encapsulated by flexible reduced graphene oxide (rGO) sheets not only effectively retarded the huge volume expansion during repeated charge-discharge cycles, but also facilitated fast lithium ion and electron transport through 3D networks. The ZGAs exhibited significantly enhanced cycling stability (745.4 mAh g −1 after 100 cycles at a current of 100 mA g −1 ) and superior rate capability (as high as 552.6 mAh g −1 at 1200 mA g −1 ). The results indicate that the ZGAs are promising anode materials for high-performance lithium-ion batteries.

  12. Melamine-formaldehyde aerogels

    Science.gov (United States)

    Pekala, Richard Walter

    1992-01-01

    Organic aerogels that are transparent and essentially colorless are prepa from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porsity, ultrafine cell/pore sizes, and optical clarity.

  13. Aerogel / Polymer Composite Materials

    Science.gov (United States)

    Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Roberson, Luke B. (Inventor); Clayton, LaNetra M. (Inventor)

    2017-01-01

    The invention provides new composite materials containing aerogels blended with thermoplastic polymer materials at a weight ratio of aerogel to thermoplastic polymer of less than 20:100. The composite materials have improved thermal insulation ability. The composite materials also have better flexibility and less brittleness at low temperatures than the parent thermoplastic polymer materials.

  14. Performance of nitrogen-doped graphene aerogel particle electrodes for electro-catalytic oxidation of simulated Bisphenol A wastewaters

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhuang [Environmental Research Academy, North China Electric Power University, Beijing 102206 (China); Labortory of Environmental Remediation and Functional Material, Suzhou Research Academy of North China Electric Power University, Suzhou, Jiangsu, 215026 (China); Zhang, Yimei, E-mail: yimei.zhang1@gmail.com [Environmental Research Academy, North China Electric Power University, Beijing 102206 (China); Labortory of Environmental Remediation and Functional Material, Suzhou Research Academy of North China Electric Power University, Suzhou, Jiangsu, 215026 (China); Zhou, Lincheng; Zhu, Hao; Wan, Fei; Wang, Yue [Labortory of Environmental Remediation and Functional Material, Suzhou Research Academy of North China Electric Power University, Suzhou, Jiangsu, 215026 (China); Zhang, Dandan [Environmental Research Academy, North China Electric Power University, Beijing 102206 (China)

    2017-06-15

    Highlights: • The new three-dimensional electrode system with the nitrogen-doped graphene aerogels particle electrodes is developed. • The optimal technique parameters were explored. • Simulated BPA waste waters are effectively degraded. • Degradation pathway and intermediates are proposed. • Three-dimensional electrode system shows good and stable removal performance. - Abstract: The treatment of effluent containing Bisphenol A (BPA) was investigated experimentally using nitrogen-doped graphene aerogel (NGAs) as particle electrodes in a three-dimensional electrode reactor for the electrochemical treatment was studied. The effects of the cell voltage, pH, the ratio of NGAs mass to solution volume and repeated times on the removal efficiency were investigated. Compared with commercial carbon particle electrodes, the NGAs exhibited stronger activity to remove BPA simulated wastewater. For 15 mg L{sup −1} of BPA solution, the degradation rate of BPA exceeded 90% after treatment for only 30 min under the optimum conditions. The COD{sub Cr} removal rate of BPA was 85%. Moreover, in the process of reused 50 times, the degradation rate of BPA can be kept in more than 85%. The COD{sub Cr} removal rate was stable at about 73%. The intermediate products of electrochemical degradation of BPA were identified by liquid chromatography-mass spectrometry liquid chromatography (LC–MS), and a probable BPA degradation pathway was proposed. It was considered that ·OH radicals by water electrolysis could constantly attack the aromatic ring to form various intermediates such as hydroxylated-BPA, isopropylphenol, hydroquinone, phenol and butantetraol, maleic acid, oxalic acid. These compounds were eventually mineralized by electrolysis into CO{sub 2} and H{sub 2}O.

  15. Silica aerogel Cerenkov counter

    International Nuclear Information System (INIS)

    Yasumi, S.; Masaike, A.; Yamamoto, A.; Yoshimura, Y.; Kawai, H.

    1984-03-01

    In order to obtain silica aerogel radiators of good quality, the prescription used by Saclay group has been developed. We have done several experiments using beams from KEK.PS to test the performance of a Cerenkov counter with aerogel modules produced in KEK. It turned out that these modules had excellent quality. The production rate of silica aerogel in KEK is 15 -- 20 litres a week. Silica aerogel modules of 20 x 10 x 3 cm 3 having the refractive index of 1.058 are successfully being used by Kyoto University group in the KEK experiment E92 (Σ). Methodes to produce silica aerogel with higher refractive index than 1.06 has been investigated both by heating an module with the refractive index of 1.06 and by hydrolyzing tetraethyl silicate. (author)

  16. Epoxy Crosslinked Silica Aerogels (X-Aerogels)

    Science.gov (United States)

    fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

    2004-01-01

    NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

  17. Highly stretchable carbon aerogels.

    Science.gov (United States)

    Guo, Fan; Jiang, Yanqiu; Xu, Zhen; Xiao, Youhua; Fang, Bo; Liu, Yingjun; Gao, Weiwei; Zhao, Pei; Wang, Hongtao; Gao, Chao

    2018-02-28

    Carbon aerogels demonstrate wide applications for their ultralow density, rich porosity, and multifunctionalities. Their compressive elasticity has been achieved by different carbons. However, reversibly high stretchability of neat carbon aerogels is still a great challenge owing to their extremely dilute brittle interconnections and poorly ductile cells. Here we report highly stretchable neat carbon aerogels with a retractable 200% elongation through hierarchical synergistic assembly. The hierarchical buckled structures and synergistic reinforcement between graphene and carbon nanotubes enable a temperature-invariable, recoverable stretching elasticity with small energy dissipation (~0.1, 100% strain) and high fatigue resistance more than 10 6 cycles. The ultralight carbon aerogels with both stretchability and compressibility were designed as strain sensors for logic identification of sophisticated shape conversions. Our methodology paves the way to highly stretchable carbon and neat inorganic materials with extensive applications in aerospace, smart robots, and wearable devices.

  18. B1 Aerogels

    DEFF Research Database (Denmark)

    Duer, Karsten; Svendsen, Sv Aa Højgaard

    1996-01-01

    , engineering and architectural basis which will support the appropriate use of aerogels in windows, solar collectors and passive solar applications, with the aim of saving or producing thermal energy for use in buildings".This objective is in very good agreement with the general scope of task 18 but where Task...... of aerogel as a material for window applications3. Construction of an aerogel DGU and measurement of key performance parameters. The goal for the aerogel DGU was to reach a Total Solar Energy Transmittance above 0.75 and a U-value below 0.5 W/m²K. These are values that can not be simultaneously reached......The report summarizes the work that has been carried out within the project "B1 AEROGELS" as a part of the IEA SH&CP Task 18 "Advanced Glazing and Associated Materials For Solar And Building Applications".By providing at the same time thermal insulation and transparency the silica aerogel is a very...

  19. Synthesis of ZnO-CuO Nanocomposite Aerogels by the Sol-Gel Route

    Directory of Open Access Journals (Sweden)

    Rula M. Allaf

    2014-01-01

    Full Text Available The epoxide addition sol-gel method has been utilized to synthesize porous zinc-copper composite aerogels in the zinc-to-copper molar ratios of 50 : 50 to 90 : 10. A two-step mixing approach has been employed to produce aerogels composed of nano- to micrometer sized particles. The aerogels were characterized by ultrahigh resolution scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. The as-synthesized aerogels had a thin flake- or petal-like microstructure comprised of clustered flakes on two size scales; they were identified as being crystalline with the crystalline species identified as copper nitrate hydroxide, zinc hydroxide chloride hydrate, and zinc hydroxide nitrate hydrate. Annealing of the aerogel materials at a relatively low temperature (400°C resulted in a complete phase transition of the material to give highly crystalline ZnO-CuO aerogels; the aerogels consisted of networked nanoparticles in the ~25–550 nm size range with an average crystallite size of ~3 nm and average crystallinity of 98%. ZnO-CuO aerogels are of particular interest due to their particular catalytic and sensing properties. This work emphasizes the versatility of this sol-gel route in synthesizing aerogels; this method offers a possible route for the fabrication of aerogels of different metal oxides and their composites.

  20. Coated Aerogel Beads

    Science.gov (United States)

    Littman, Howard (Inventor); Plawsky, Joel L. (Inventor); Paccione, John D. (Inventor)

    2014-01-01

    Methods and apparatus for coating particulate material are provided. The apparatus includes a vessel having a top and a bottom, a vertically extending conduit having an inlet in the vessel and an outlet outside of the vessel, a first fluid inlet in the bottom of the vessel for introducing a transfer fluid, a second fluid inlet in the bottom of the vessel for introducing a coating fluid, and a fluid outlet from the vessel. The method includes steps of agitating a material, contacting the material with a coating material, and drying the coating material to produce a coated material. The invention may be adapted to coat aerogel beads, among other materials. A coated aerogel bead and an aerogel-based insulation material are also disclosed.

  1. Super insulating aerogel glazing

    DEFF Research Database (Denmark)

    Schultz, Jørgen Munthe; Jensen, Karsten Ingerslev; Kristiansen, Finn Harken

    2004-01-01

    form the weakest part of the thermal envelope with respect to heat loss coefficient, but on the other hand also play an important role for passive solar energy utilisation. For window orientations other than south, the net energy balance will be close to or below zero. However, the properties......Monolithic silica aerogel offers the possibility of combining super insulation and high solar energy transmittance, which has been the background for a previous and a current EU project on research and development of monolithic silica aerogel as transparent insulation in windows. Generally, windows...... of aerogel glazing will allow for a positive net energy gain even for north facing vertical windows in a Danish climate during the heating season. This means that high quality daylight can be obtained even with additional energy gain. On behalf of the partners of the two EU projects, results related...

  2. Aerogel for FARICH detector

    Energy Technology Data Exchange (ETDEWEB)

    Barnyakov, A.Yu. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Barnyakov, M.Yu. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, Karl Marks 20, Novosibirsk 630073 (Russian Federation); Bobrovnikov, V.S.; Buzykaev, A.R.; Gulevich, V.V. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Danilyuk, A.F. [Boreskov Institute of Catalysis, Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Kononov, S.A.; Kravchenko, E.A. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Kuyanov, I.A. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Lopatin, S.A. [Boreskov Institute of Catalysis, Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Onuchin, A.P.; Ovtin, I.V.; Podgornov, N.A. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, Karl Marks 20, Novosibirsk 630073 (Russian Federation); Porosev, V.V. [Budker Institute of Nuclear Physics, Lavrentieva 11, Novosibirsk 630090 (Russian Federation); Predein, A.Yu.; Protsenko, R.S. [Boreskov Institute of Catalysis, Lavrentieva 5, Novosibirsk 630090 (Russian Federation)

    2014-12-01

    We present our current experience in preparation of focusing aerogels for the Focusing Aerogel RICH detector. Multilayer focusing aerogel tiles have been produced in Novosibirsk by a collaboration of the Budker Institute of Nuclear Physics and Boreskov Institute of Catalysis since 2004. We have obtained 2–3–4-layer blocks with the thickness of 30–45 mm. In 2012, the first samples of focusing blocks with continuous density (refractive index) gradient along thickness were produced. This technology can significantly reduce the contribution from the geometric factor of the radiator thickness to the resolution of the measured Cherenkov angle in the FARICH detector. The special installation was used for automatic control of reagents ratio during the synthesis process. The first samples were tested using the digital radiography method and on the electron beam with the FARICH prototype.

  3. Green synthesis of amphipathic graphene aerogel constructed by using the framework of polymer-surfactant complex for water remediation

    Science.gov (United States)

    Cao, Jingjing; Wang, Ziyuan; Yang, Xianhou; Tu, Jing; Wu, Ronglan; Wang, Wei

    2018-06-01

    Graphene aerogels have been extensively studied in water treatment and oil remediation. We report a mild and green method to prepare a 3D-columnar graphene aerogel. The aerogel was synthesized by using polyvinyl alcohol (PVA) and stearic acid (SA) as crosslinking agents to construct a framework of reduced graphene oxide (RGO). The interaction between PVA, SA, and stacked RGO sheets created a mechanically very robust aerogel. The aerogel possesses ultra-light performance with the destiny ranging from 4.9 to 10 mg cm-3. The aerogel also demonstrated ultrafast oil absorption, good fire-resistance, and excellent mechanical properties. The adsorptive capacities are in the range of 105-250 times of its original weight for various organic liquids after the absorption. The aerogel also exhibited a strong durability and reusability, and after ten cycles of absorbing-squeezing, the adsorptive capacity is nearly unchanged, indicating potential application in practical oil remediation.

  4. Transparent aerogel Windows

    DEFF Research Database (Denmark)

    Jensen, Karsten Ingerslev; Schultz, Jørgen Munthe

    the supercritical washing step included in the drying phase. At the same time the production plant have been modified to recycle most of the chemicals involved in the production process. A large number of aerogel glazing prototypes have been made with partly evacuated aerogel in between two layers of low iron...... and anti reflection treated glass panes with an airtight edge seal solution based on multi-layered plastic foil developed for vacuum insulation purposes. The edge seal solution shows only a very limited thermal bridge effect. The final glazing has a total solar energy transmittance about 87% and a U...

  5. Kinetics of FeII-polyaminocarboxylate oxidation by molecular oxygen

    Science.gov (United States)

    Wilson, Jessica M.; Farley, Kevin J.; Carbonaro, Richard F.

    2018-03-01

    Complexation of iron by naturally-occurring and synthetic organic ligands has a large effect on iron oxidation and reduction rates which in turn affect the aqueous geochemistry of many other chemical constituents. In this study, the kinetics of FeII oxidation in the presence of the polyaminocarboxylate synthetic chelating agents ethylene glycol tetraacetic acid (EGTA) and trimethylenediamine-N,N,N‧,N‧-tetraacetic acid (TMDTA) was investigated over the pH range 5.50-8.53. Batch oxidation experiments in the presence of molecular oxygen were conducted using a 2:1 M concentration ratio of polyaminocarboxylate (ligand, L) to FeII. The experimental data resembled first order kinetics for the oxidation of FeII-L to FeIII-L and observed rate constants at pH 6.0 were comparable to rate constants for the oxidation of inorganic FeII. Similar to other structurally-similar FeII-polyaminocarboxylate complexes, oxidation rates of FeII-EGTA and FeII-TMDTA decrease with increasing pH, which is the opposite trend for the oxidation of FeII complexed with inorganic ligands. However, the oxidation rates of FeII complexed with EGTA and TMDTA were considerably lower (4-5 orders of magnitude) than FeII complexed to ethylenediaminetetraacetic acid (EDTA). The distinguishing feature of the slower-reacting complexes is that they have a longer backbone between diamine functional groups. An analytical equilibrium model was developed to determine the contributions of the species FeIIL2- and FeII(H)L- to the overall oxidation rate of FeII-L. Application of this model indicated that the protonated FeII(H)L species are more than three orders of magnitude more reactive than FeIIL2-. These rate constants were used in a coupled kinetic equilibrium numerical model where the ligand to iron ratio (TOTL:TOTFe) and pH were varied to evaluate the effect on the FeII oxidation rate. Overall, increasing TOTL:TOTFe for EGTA and TMDTA enhances FeII oxidation rates at lower pH and inhibits FeII oxidation

  6. Aerogels in Chemical Engineering: Strategies Toward Tailor-Made Aerogels.

    Science.gov (United States)

    Smirnova, Irina; Gurikov, Pavel

    2017-06-07

    The present review deals with recent advances in the rapidly growing field of aerogel research and technology. The major focus of the review lies in approaches that allow tailoring of aerogel properties to meet application-driven requirements. The decisive properties of aerogels are discussed with regard to existing and potential application areas. Various tailoring strategies, such as modulation of the pore structure, coating, surface modification, and post-treatment, are illustrated by results of the last decade. In view of commercialization of aerogel-based products, a panorama of current industrial aerogel suppliers is given, along with a discussion of possible alternative sources for raw materials and precursors. Finally, growing points and perspectives of the aerogel field are summarized.

  7. Optical sensing of triethylamine using CdSe aerogels

    International Nuclear Information System (INIS)

    Yao Qinghong; Brock, Stephanie L

    2010-01-01

    The photoluminescence (PL) response of highly porous CdSe aerogels to triethylamine (TEA) is investigated and compared to results from prior studies on single crystals and nanoparticle-polymer composites. As-prepared CdSe aerogels show significant and reversible enhancement of luminescence intensity upon exposure to TEA relative to the intensity in pure argon carrier gas. The enhancement in the PL response is dependent on the concentration and linear over the range of TEA concentration studied (4.7 x 10 3 -75 x 10 3 ppm). The sensing response of previously tested samples exhibits saturation behavior that is modeled using Langmuir adsorption isotherms, yielding adsorption equilibrium constants in the range 300-380 atm -1 . The response is sensitively affected by the surface characteristics of the aerogel; when the wet gels are treated with pyridine prior to aerogel formation, the response to TEA is diminished, and when as-prepared aerogels are heated in a vacuum, no subsequent response is observed. Deactivation is attributed to an increase in surface oxide (SeO 2 ) and decrease in surface Cd 2+ Lewis acid sites. Sensing runs of approximately one hour have little impact on the morphology or crystallinity of the aerogels, but do result in partial removal of residual thiolate ligands left over from the gelation process.

  8. Super insulating aerogel glazing

    DEFF Research Database (Denmark)

    Schultz, Jørgen Munthe; Jensen, Karsten Ingerslev; Kristiansen, Finn Harken

    2005-01-01

    of the glass and a heat-treatment of the aerogel increases the visible quality and the solar energy transmittance. A low-conductive rim seal solution with the required vacuum barrier properties has been developed along with a reliable assembly and evacuation process. The prototypes have a centre heat loss...

  9. Effects of Microgravity on the Formation of Aerogels

    Science.gov (United States)

    Hunt, A. J.; Ayers, M. R.; Sibille, L.; Cronise, R. J.; Noever, D. A.

    1999-01-01

    This paper describes research to investigate fundamental aspects of the effects of microgravity on the formation of the microstructure of metal oxide alcogels and aerogels. We are studying the role of gravity on pore structure and gel uniformity in collaboration with Marshall Space Flight Center (MSFC) on gelling systems under microgravity conditions. While this project was just initiated in May 1998, related research performed earlier is described along with the plans and rationale for the current microgravity investigation to provide background and describe newly developing techniques that should be useful for the current gellation studies. The role of gravity in materials processing must be investigated through the study of well-mastered systems. Sol-gel processed materials are near-perfect candidates to determine the effect of gravity on the formation and growth of random clusters from hierarchies of aggregated units. The processes of hydrolysis, condensation, aggregation and gellation in the formation of alcogels are affected by gravity and therefore provide a rich system to study under microgravity conditions. Supercritical drying of the otherwise unstable wet alcogel preserves the alcogel structure produced during sol-gel processing as aerogel. Supercritically dried aerogel provides for the study of material microstructures without interference from the effects of surface tension, evaporation, and solvent flow. Aerogels are microstructured, low density open-pore solids. They have many unusual properties including: transparency, excellent thermal resistance, high surface area, very low refractive index, a dielectric constant approaching that of air, and extremely low sound velocity. Aerogels are synthesized using sol-gel processing followed by supercritical solvent extraction that leaves the original gel structure virtually intact. These studies will elucidate the effects of microgravity on the homogeneity of the microstructure and porosity of aerogel. The

  10. Aerogels in Aerospace: An Overview

    Directory of Open Access Journals (Sweden)

    Nadiir Bheekhun

    2013-01-01

    Full Text Available Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology. Among the classes of aerogels, silica aerogel exhibits the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids. Its acoustical property is such that it can absorb the sound waves reducing speed to 100 m/s compared to 332 m/s for air. However, when it comes to commercialization, the result is not as expected. It seems that mass production, particularly in the aerospace industry, has dawdled behind. This paper highlights the evolution of aerogels in general and discusses the functions and significances of silica aerogel in previous astronautical applications. Future outer-space applications have been proposed as per the current research trend. Finally, the implementation of conventional silica aerogel in aeronautics is argued with an alternative known as Maerogel.

  11. OXIDATION OF CYCLIC AMINES BY MOLYBDENUM(II) AND ...

    African Journals Online (AJOL)

    Preferred Customer

    metal is in formal oxidation state +2. Since no reduction can take place without oxidation and vice versa, we can reasonably say the reduction of Mo(II) and W(II) species is accompanied by oxidation of the amine. At this juncture, we should point out that C=N bonds are also known to absorb IR radiation in the same spectral ...

  12. System and method for 3D printing of aerogels

    Science.gov (United States)

    Worsley, Marcus A.; Duoss, Eric; Kuntz, Joshua; Spadaccini, Christopher; Zhu, Cheng

    2016-03-08

    A method of forming an aerogel. The method may involve providing a graphene oxide powder and mixing the graphene oxide powder with a solution to form an ink. A 3D printing technique may be used to write the ink into a catalytic solution that is contained in a fluid containment member to form a wet part. The wet part may then be cured in a sealed container for a predetermined period of time at a predetermined temperature. The cured wet part may then be dried to form a finished aerogel part.

  13. Preparation and characterization of Mg-Zr mixed oxide aerogels and their application as aldol condensation catalysts.

    Science.gov (United States)

    Sádaba, Irantzu; Ojeda, Manuel; Mariscal, Rafael; Richards, Ryan; López Granados, Manuel

    2012-10-08

    A series of Mg-Zr mixed oxides with different nominal Mg/(Mg+Zr) atomic ratios, namely 0, 0.1, 0.2, 0.4, 0.85, and 1, is prepared by alcogel methodology and fundamental insights into the phases obtained and resulting active sites are studied. Characterization is performed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N(2) adsorption-desorption isotherms, and thermal and chemical analysis. Cubic Mg(x)Zr(1-x)O(2-x) solid solution, which results from the dissolution of Mg(2+) cations within the cubic ZrO(2) structure, is the main phase detected for the solids with theoretical Mg/(Mg+Zr) atomic ratio ≤0.4. In contrast, the cubic periclase (c-MgO) phase derived from hydroxynitrates or hydroxy precursors predominates in the solid with Mg/(Mg+Zr)=0.85. c-MgO is also incipiently detected in samples with Mg/(Mg+Zr)=0.2 and 0.4, but in these solids the c-MgO phase mostly arises from the segregation of Mg atoms out of the alcogel-derived c-Mg(x)Zr(1-x)O(2-x) phase during the calcination process, and therefore the species c-MgO and c-Mg(x)Zr(1-x)O(2-x) are in close contact. Regarding the intrinsic activity in furfural-acetone aldol condensation in the aqueous phase, these Mg-O-Zr sites located at the interface between c-Mg(x)Zr(1-x)O(2-x) and segregated c-MgO display a much larger intrinsic activity than the other noninterface sites that are present in these catalysts: Mg-O-Mg sites on c-MgO and Mg-O-Zr sites on c-Mg(x)Zr(1-x)O(2-x). The very active Mg-O-Zr sites rapidly deactivate in the furfural-acetone condensation due to the leaching of active phases, deposition of heavy hydrocarbonaceous compounds, and hydration of the c-MgO phase. Nonetheless, these Mg-Zr materials with very high specific surface areas would be suitable solid catalysts for other relevant reactions catalyzed by strong basic sites in nonaqueous environments. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Low-temperature Synthesis of Tin(II) Oxide From Tin(II) ketoacidoximate Precursor

    KAUST Repository

    Alshankiti, Buthainah

    2015-01-01

    Sn (II) oxide finds numerous applications in different fields such as thin film transistors1, solar cells2 and sensors.3 In this study we present the fabrication of tin monoxide SnO by using Sn (II) ketoacid oximate complexes as precursors. Tin (II

  15. Protective Skins for Aerogel Monoliths

    Science.gov (United States)

    Leventis, Nicholas; Johnston, James C.; Kuczmarski, Maria A.; Meador, Ann B.

    2007-01-01

    A method of imparting relatively hard protective outer skins to aerogel monoliths has been developed. Even more than aerogel beads, aerogel monoliths are attractive as thermal-insulation materials, but the commercial utilization of aerogel monoliths in thermal-insulation panels has been inhibited by their fragility and the consequent difficulty of handling them. Therefore, there is a need to afford sufficient protection to aerogel monoliths to facilitate handling, without compromising the attractive bulk properties (low density, high porosity, low thermal conductivity, high surface area, and low permittivity) of aerogel materials. The present method was devised to satisfy this need. The essence of the present method is to coat an aerogel monolith with an outer polymeric skin, by painting or spraying. Apparently, the reason spraying and painting were not attempted until now is that it is well known in the aerogel industry that aerogels collapse in contact with liquids. In the present method, one prevents such collapse through the proper choice of coating liquid and process conditions: In particular, one uses a viscous polymer precursor liquid and (a) carefully controls the amount of liquid applied and/or (b) causes the liquid to become cured to the desired hard polymeric layer rapidly enough that there is not sufficient time for the liquid to percolate into the aerogel bulk. The method has been demonstrated by use of isocyanates, which, upon exposure to atmospheric moisture, become cured to polyurethane/polyurea-type coats. The method has also been demonstrated by use of commercial epoxy resins. The method could also be implemented by use of a variety of other resins, including polyimide precursors (for forming high-temperature-resistant protective skins) or perfluorinated monomers (for forming coats that impart hydrophobicity and some increase in strength).

  16. Property control of graphene aerogels by in situ growth of silicone polymer

    Science.gov (United States)

    Zhou, Shuai; Zhou, Xiang; Hao, Gazi; Jiang, Wei; Wang, Tianhe

    2018-05-01

    Modulation of the density (from 3.5 to 64 mg cm-3), hydrophobicity and oil-uptake capability of graphene aerogels in extensive ranges were achieved by reacting (3-Mercaptopropyl)trimethoxysilane (MPS) with graphene oxide solutions under heating. The reaction allowed a characteristic silicone substructure to be formed on graphene and joint the graphene layers firmly together. With the increase of MPS concentrations (≤ca. 0.2 vol%), the nano silicone polymer grown on graphene functioned as a "linker" and "spacer", leading to a substantial decrease of the aerogel density. Because of the formation of silicone polymer and the characteristic nano-micro substructures on the backbones of graphene aerogels, the graphene aerogels exhibited a high hydrophobicity with the water contact angle consistently exceeding 142 degrees. Functionalized graphene aerogels with a density of 3.5 mg cm-3 were conveniently fabricated that displayed an extraordinary oil absorption capacity, 182 times for lubricating oil and 143 times for n-hexane of its own weight. Furthermore, the aerogels maintained their ultra-high absorption capability even after 20 absorption-distillation cycles, due to structural integrity held by the strong interfacial adhesion between graphene sheets and polymer chains of aerogels. This study offers a promising graphene aerogels and also provides a strategy for fabricating extra low dense functional materials.

  17. Functionalized silica aerogels for gas-phase purification, sensing, and catalysis: A review

    Energy Technology Data Exchange (ETDEWEB)

    Amonette, James E.; Matyáš, Josef

    2017-09-01

    Silica aerogels have a rich history and a unique, fascinating gas-phase chemistry that has lent them to many diverse applications. This review starts with a brief discussion of the fundamental issues driving the movement of gases in silica aerogels and then proceeds to provide an overview of the work that has been done with respect to the purification of gases, sensing of individual gases, and uses of silica aerogels as catalysts for gas-phase reactions. Salient features of the research behind these different applications are presented, and, where appropriate, critical aspects that affect the practical use of the aerogels are noted. Specific sections under the gas-purification category focus on the removal of airborne nanoparticles, carbon dioxide, volatile organic compounds, sulfur gases and radioactive iodine from gas streams. The use of silica aerogels as sensors for humidity, oxygen, hydrocarbons, volatile acids and bases, various non-ammoniacal nitrogen gases, and viral particles is discussed. With respect to catalysis, the demonstrated use of silica aerogels as supports for oxidation, Fischer-Tropsch, alkane isomerization, and hydrogenation reactions is reviewed, along with a section on untested catalytic formulations involving silica aerogels. A short section focuses on recent developments in thermomolecular Knudsen compressor pumps using silica aerogel membranes. The review continues with an overview of the production methods, locations of manufacturing facilities globally, and a brief discussion of the economics before concluding with a few remarks about the present and future trends revealed by the work presented.

  18. Titania aerogel prepared by low temperature supercritical drying

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Bakardjieva, Snejana; Šubrt, Jan; Szatmáry, Lórant

    2006-01-01

    Roč. 91, 1-3 (2006), s. 1-6 ISSN 1387-1811 R&D Projects: GA MŠk(CZ) 1M0577 Institutional research plan: CEZ:AV0Z40320502 Keywords : aerogels * titanium oxide * supercritical drying Subject RIV: CA - Inorganic Chemistry Impact factor: 2.796, year: 2006

  19. Kinetics of oxidation of nickel(II) aza macrocycles by ...

    Indian Academy of Sciences (India)

    The kinetics of the oxidation of nickel (II) hexaaza and nickel (II) pentaaza macrocycles by the peroxydisulphate anion, S2O8 2-, were studied in aqueous media. Effect of H on reaction rate was also studied. The rate increases with increase of S2OO8 2- concentration. Rates are almost independent of acid between H 4 ...

  20. Oxidative Metabolites of Curcumin Poison Human Type II Topoisomerases†

    Science.gov (United States)

    Ketron, Adam C.; Gordon, Odaine N.; Schneider, Claus; Osheroff, Neil

    2013-01-01

    The polyphenol curcumin is the principal flavor and color component of the spice turmeric. Beyond its culinary uses, curcumin is believed to positively impact human health and displays antioxidant, anti-inflammatory, antibacterial, and chemopreventive properties. It also is in clinical trials as an anticancer agent. In aqueous solution at physiological pH, curcumin undergoes spontaneous autoxidation that is enhanced by oxidizing agents. The reaction proceeds through a series of quinone methide and other reactive intermediates to form a final dioxygenated bicyclopentadione product. Several naturally occurring polyphenols that can form quinones have been shown to act as topoisomerase II poisons (i.e., increase levels of topoisomerase II-mediated DNA cleavage). Because several of these compounds have chemopreventive properties, we determined the effects of curcumin, its oxidative metabolites, and structurally related degradation products (vanillin, ferulic acid, and feruloylmethane), on the DNA cleavage activities of human topoisomerase IIα and IIβ. Intermediates in the curcumin oxidation pathway increased DNA scission mediated by both enzymes ~4-5–fold. In contrast, curcumin and the bicyclopentadione, as well as vanillin, ferulic acid, and feruloylmethane, had no effect on DNA cleavage. As found for other quinone-based compounds, curcumin oxidation intermediates acted as redox-dependent (as opposed to interfacial) topoisomerase II poisons. Finally, under conditions that promote oxidation, the dietary spice turmeric enhanced topoisomerase II-mediated DNA cleavage. Thus, even within the more complex spice formulation, oxidized curcumin intermediates appear to function as topoisomerase II poisons. PMID:23253398

  1. 3D Networked Tin Oxide/Graphene Aerogel with a Hierarchically Porous Architecture for High-Rate Performance Sodium-Ion Batteries.

    Science.gov (United States)

    Xie, Xiuqiang; Chen, Shuangqiang; Sun, Bing; Wang, Chengyin; Wang, Guoxiu

    2015-09-07

    Low-cost and sustainable sodium-ion batteries are regarded as a promising technology for large-scale energy storage and conversion. The development of high-rate anode materials is highly desirable for sodium-ion batteries. The optimization of mass transport and electron transfer is crucial in the discovery of electrode materials with good high-rate performances. Herein, we report the synthesis of 3 D interconnected SnO2 /graphene aerogels with a hierarchically porous structure as anode materials for sodium-ion batteries. The unique 3 D architecture was prepared by a facile in situ process, during which cross-linked 3 D conductive graphene networks with macro-/meso-sized hierarchical pores were formed and SnO2 nanoparticles were dispersed uniformly on the graphene surface simultaneously. Such a 3 D functional architecture not only facilitates the electrode-electrolyte interaction but also provides an efficient electron pathway within the graphene networks. When applied as anode materials in sodium-ion batteries, the as-prepared SnO2 /graphene aerogel exhibited high reversible capacity, improved cycling performance compared to SnO2 , and promising high-rate capability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Plasmonic Aerogels as a Three-Dimensional Nanoscale Platform for Solar Fuel Photocatalysis.

    Science.gov (United States)

    DeSario, Paul A; Pietron, Jeremy J; Dunkelberger, Adam; Brintlinger, Todd H; Baturina, Olga; Stroud, Rhonda M; Owrutsky, Jeffrey C; Rolison, Debra R

    2017-09-19

    We use plasmonic Au-TiO 2 aerogels as a platform in which to marry synthetically thickened particle-particle junctions in TiO 2 aerogel networks to Au∥TiO 2 interfaces and then investigate their cooperative influence on photocatalytic hydrogen (H 2 ) generation under both broadband (i.e., UV + visible light) and visible-only excitation. In doing so, we elucidate the dual functions that incorporated Au can play as a water reduction cocatalyst and as a plasmonic sensitizer. We also photodeposit non-plasmonic Pt cocatalyst nanoparticles into our composite aerogels in order to leverage the catalytic water-reducing abilities of Pt. This Au-TiO 2 /Pt arrangement in three dimensions effectively utilizes conduction-band electrons injected into the TiO 2 aerogel network upon exciting the Au SPR at the Au∥TiO 2 interface. The extensive nanostructured high surface-area oxide network in the aerogel provides a matrix that spatially separates yet electrochemically connects plasmonic nanoparticle sensitizers and metal nanoparticle catalysts, further enhancing solar-fuels photochemistry. We compare the photocatalytic rates of H 2 generation with and without Pt cocatalysts added to Au-TiO 2 aerogels and demonstrate electrochemical linkage of the SPR-generated carriers at the Au∥TiO 2 interfaces to downfield Pt nanoparticle cocatalysts. Finally, we investigate visible light-stimulated generation of conduction band electrons in Au-TiO 2 and TiO 2 aerogels using ultrafast visible pump/IR probe spectroscopy. Substantially more electrons are produced at Au-TiO 2 aerogels due to the incorporated SPR-active Au nanoparticle, whereas the smaller population of electrons generated at Au-free TiO 2 aerogels likely originate at shallow traps in the high surface-area mesoporous aerogel.

  3. Dynamics of capillary condensation in aerogels.

    Science.gov (United States)

    Nomura, R; Miyashita, W; Yoneyama, K; Okuda, Y

    2006-03-01

    Dynamics of capillary condensation of liquid 4He in various density silica aerogels was investigated systematically. Interfaces were clearly visible when bulk liquid was rapidly sucked into the aerogel. Time evolution of the interface positions was consistent with the Washburn model and their effective pore radii were obtained. Condensation was a single step in a dense aerogel and two steps in a low density aerogel. Crossover between the two types of condensation was observed in an intermediate density aerogel. Variety of the dynamics may be the manifestation of the fractal nature of aerogels which had a wide range of distribution of pore radii.

  4. Enzymic oxidation of carbon monoxide. II

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, T

    1959-01-01

    An enzyme which catalyzes the oxidation of carbon monoxide into carbon dioxide was obtained in a cell free state from Desulfovibrio desulfuricans. The enzyme activity was assayed manometrically by measuring the rate of gas uptake under the atmosphere of carbon monoxide in the presence of benzyl-viologen as an oxidant. The optimum pH range was 7 to 8. The activity was slightly suppressed by illumination. The enzyme was more stable than hydrogenase or formate dehydrogenase against the heat treatment, suggesting that it is a different entity from these enzymes. In the absence of an added oxidant, the enzyme preparation produced hydrogen gas under the atmosphere of carbon monoxide. The phenomenon can be explained assuming the reductive decomposition of water. 17 references, 4 figures, 2 tables.

  5. Facile Assembly of 3D Porous Reduced Graphene Oxide/Ultrathin MnO2 Nanosheets-S Aerogels as Efficient Polysulfide Adsorption Sites for High-Performance Lithium-Sulfur Batteries.

    Science.gov (United States)

    Zhao, Xiaojun; Wang, Hui; Zhai, Gaohong; Wang, Gang

    2017-05-23

    Rechargeable lithium-sulfur (Li-S) batteries are receiving much attention due to their high specific capacity, low cost, and environmental friendliness. Nonetheless, fast capacity decay and low specific capacity still limit their practical implementation. Herein, we report a facile strategy to overcome these challenges by the design and fabrication of 3D porous reduced graphene oxide/ultrathin MnO 2 nanosheets-S aerogel (rGM-SA) composites for Li-S batteries. By a simple solvothermal reaction process, nanosized S atoms are homogeneously decorated into the 3D scaffold formed by reduced graphene oxide (rGO) and MnO 2 nanosheets, which can form the homogeneous rGM-SA composites. In this porous network architecture, rGO serves as an electron and ion transfer pathway, a physical adsorption site for polysulfides, and provides structural stability. The ultrathin MnO 2 nanosheets provide strong binding sites for trapping polysulfide intermediates. The 3D porous rGO/MnO 2 architecture enables rapid ion transport and buffers volume expansion of sulfur during discharge. The rGM-SA composites can be directly used as lithium-sulfur battery cathodes without using binder and conductive additive. As a result of this multifunctional arrangement, the rGM-SA composites exhibit high and stable-specific capacities over 200 cycles and excellent high-rate performances. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Refractive index dispersion law of silica aerogel

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Perego, D.L.; Storaci, B.

    2007-01-01

    This paper presents measurements of the refractive index of a hygroscopic silica aerogel block at several wavelengths. The measurements, performed with a monochromator, have been compared with different parameterisations for n(λ), in order to determine the best chromaticity law for the aerogel. This is an important input for design and operation of RICH detectors with silica aerogel radiator. (orig.)

  7. Polyurea-Based Aerogel Monoliths and Composites

    Science.gov (United States)

    Lee, Je Kyun

    2012-01-01

    aerogel insulation material was developed that will provide superior thermal insulation and inherent radiation protection for government and commercial applications. The rubbery polyureabased aerogel exhibits little dustiness, good flexibility and toughness, and durability typical of the parent polyurea polymer, yet with the low density and superior insulation properties associated with aerogels. The thermal conductivity values of polyurea-based aerogels at lower temperature under vacuum pressures are very low and better than that of silica aerogels. Flexible, rubbery polyurea-based aerogels are able to overcome the weak and brittle nature of conventional inorganic and organic aerogels, including polyisocyanurate aerogels, which are generally prepared with the one similar component to polyurethane rubber aerogels. Additionally, with higher content of hydrogen in their structures, the polyurea rubber-based aerogels will also provide inherently better radiation protection than those of inorganic and carbon aerogels. The aerogel materials also demonstrate good hydrophobicity due to their hydrocarbon molecular structure. There are several strategies to overcoming the drawbacks associated with the weakness and brittleness of silica aerogels. Development of the flexible fiber-reinforced silica aerogel composite blanket has proven to be one promising approach, providing a conveniently fielded form factor that is relatively robust in industrial environments compared to silica aerogel monoliths. However, the flexible, silica aerogel composites still have a brittle, dusty character that may be undesirable, or even intolerable, in certain application environments. Although the cross - linked organic aerogels, such as resorcinol- formaldehyde (RF), polyisocyanurate, and cellulose aerogels, show very high impact strength, they are also very brittle with little elongation (i.e., less rubbery). Also, silica and carbon aerogels are less efficient radiation shielding materials due

  8. Palladium(II)-catalyzed oxidation of L-tryptophan by ...

    Indian Academy of Sciences (India)

    Initial addition of the reaction product, hexacyanoferrate(II), does not affect the rate significantly. A plausible mechanistic scheme explaining all the observed kinetic results has been proposed. The final oxidation products are identified as indole-3-acetaldehyde, ammonium ion and carbon dioxide. The rate law associated ...

  9. Oxygen dependency of neutrophilic Fe(II) oxidation by Leptothrix differs from abiotic reaction

    NARCIS (Netherlands)

    Vollrath, S.; Behrends, T.; Van Cappellen, P.

    2012-01-01

    Neutrophilic Fe(II) oxidizing microorganisms are found in many natural environments. It has been hypothesized that, at low oxygen concentrations, microbial iron oxidation is favored over abiotic oxidation. Here, we compare the kinetics of abiotic Fe(II) oxidation to oxidation in the presence of

  10. Thin Aerogel as a Spacer in Multilayer Insulation

    Science.gov (United States)

    Moroz, Nancy

    2015-01-01

    Cryogenic fluid management is a critical technical area that is needed for future space exploration. A key challenge is the storability of liquid hydrogen (LH2), liquid methane (LCH4), and liquid oxygen (LOX) propellants for long-duration missions. The storage tanks must be well-insulated to prevent over-pressurization and venting, which can lead to unacceptable propellant losses for long-duration missions to Mars and beyond. Aspen Aerogels had validated the key process step to enable the fabrication of thin, low-density aerogel materials. The multilayer aerogel insulation (MLAI) system prototypes were prepared using sheets of aerogel materials with superior thermal performance exceeding current state-of-the-art insulation for space applications. The exceptional properties of this system include a new breakthrough in high-vacuum cryogenic thermal insulation, providing a durable material with excellent thermal performance at a reduced cost when compared to longstanding state-of-the-art multilayer insulation systems. During the Phase II project, further refinement and qualification/system-level testing of the MLAI system will be performed for use in cryogenic storage applications. Aspen has been in discussions with United Launch Alliance, LLC; NASA's Kennedy Space Center; and Yetispace, Inc., to test the MLAI system on rea-lworld tanks such as Vibro-Acoustic Test Article (VATA) or the Cryogenic Orbital Testbed (CRYOTE).

  11. Flexible Supercapacitors Based on Polyaniline Arrays Coated Graphene Aerogel Electrodes.

    Science.gov (United States)

    Yang, Yu; Xi, Yunlong; Li, Junzhi; Wei, Guodong; Klyui, N I; Han, Wei

    2017-12-01

    Flexible supercapacitors(SCs) made by reduced graphene oxide (rGO)-based aerogel usually suffer from the low energy density, short cycle life and bad flexibility. In this study, a new, synthetic strategy was developed for enhancing the electrochemical performances of rGO aerogel-based supercapacitor via electrodeposition polyaniline arrays on the prepared ultralight rGO aerogel. The novel hybrid composites with coated polyaniline (PANI) arrays growing on the rGO surface can take full advantage of the rich open-pore and excellent conductivity of the crosslinking framework structure of 3D rGO aerogel and high capacitance contribution from the PANI. The obtained hybrid composites exhibit excellent electrochemical performance with a specific capacitance of 432 F g -1 at the current density of 1 A g -1 , robust cycling stability to maintain 85% after 10,000 charge/discharge cycles and high energy density of 25 W h kg -1 . Furthermore, the flexible all-solid-state supercapacitor have superior flexibility and outstanding stability under different bending states from the straight state to the 90° status. The high-performance flexible all-solid-state SCs together with the lighting tests demonstrate it possible for applications in portable electronics.

  12. Ultralight Graphene/Carbon Nanotubes Aerogels with Compressibility and Oil Absorption Properties

    Directory of Open Access Journals (Sweden)

    Da Zhao

    2018-04-01

    Full Text Available Graphene aerogels have many advantages, such as low density, high elasticity and strong adsorption. They are considered to be widely applicable in many fields. At present, the most valuable research area aims to find a convenient and effective way to prepare graphene aerogels with excellent properties. In this work graphene/carbon nanotube aerogels are prepared through hydrothermal reduction, freeze-drying and high temperature heat treatment with the blending of graphene oxide and carbon nanotubes. A new reducing agent-ascorbic acid is selected to explore the best preparation process. The prepared aerogels have compression and resilience and oil absorption properties due to the addition of carbon nanotubes as designed.

  13. Silica aerogel and space astrophysics

    International Nuclear Information System (INIS)

    Koch-Miramond, L.

    1985-09-01

    Silica aerogels have been produced in large and transparent blocks for space astrophysics experiments since the beginning of the 1970's. They were used in cosmic ray experiments on board balloons by the Saclay group. A new space venture where aerogel Cerenkov radiators will play a decisive role is currently being prepared by a large collaboration of European and US Institutes. It will be part of the so-called International Solar Polar Mission (ISPM) which will explore the heliosphere over the full range of solar latitudes from the ecliptic (equatorial) plane to the magnetic poles of the sun. Comments on properties and long term behaviour of silica aerogel cerenkov radiators in space environment are given

  14. Polyimide Cellulose Nanocrystal Composite Aerogels

    Science.gov (United States)

    Nguyen, Baochau N.; Meador, Mary Ann; Rowan, Stuart; Cudjoe, Elvis; Sandberg, Anna

    2014-01-01

    Polyimide (PI) aerogels are highly porous solids having low density, high porosity and low thermal conductivity with good mechanical properties. They are ideal for various applications including use in antenna and insulation such as inflatable decelerators used in entry, decent and landing operations. Recently, attention has been focused on stimuli responsive materials such as cellulose nano crystals (CNCs). CNCs are environmentally friendly, bio-renewable, commonly found in plants and the dermis of sea tunicates, and potentially low cost. This study is to examine the effects of CNC on the polyimide aerogels. The CNC used in this project are extracted from mantle of a sea creature called tunicates. A series of polyimide cellulose nanocrystal composite aerogels has been fabricated having 0-13 wt of CNC. Results will be discussed.

  15. Preparation of lignin-based carbon aerogels as biomaterials for nano-supercapacitor

    Science.gov (United States)

    Yang, Bong Suk; Kang, Kyu-Young; Jeong, Myung-Joon

    2017-10-01

    Kraft and organosolv lignins, generally produced in chemical pulping and bio-refinery processes of lignocellulosic biomass, were used to prepare lignin-based carbon aerogels for supercapacitors as raw materials. The difference between lignins and lignin-based aerogels were compared by analyzing physical and chemical properties, including molecular weight, polydispersity, and reactivity with formaldehyde. Also, density, shrinkage, Brunauer-Emmett-Teller (BET) surface area and scanning electron microscope (SEM) images of the lignin-based aerogel were investigated. Kraft lignin consisting of coniferyl alcohol (G) and p-coumaryl alcohol (H) increased the reactivity of formaldehyde, formed a hydrogel well (porosity > 0.45), and specific surface area higher than organosolv lignin. In the case of kraft lignin, there were irregular changes such as oxidation and condensation in the pulping process. However, reaction sites with aromatic rings in lignin impacted the production of aerogel and required a long gelation period. The molecular weight of lignin influences the gelation time in producing lignin-based aerogel, and lignin composition affects the BET surface area and pore structures of the lignin-based carbon aerogels.

  16. Oxidative Ce"3"+ sequestration by fungal manganese oxides with an associated Mn(II) oxidase activity

    International Nuclear Information System (INIS)

    Zheng, Haisu; Tani, Yukinori; Naitou, Hirotaka; Miyata, Naoyuki; Tojo, Fuyumi

    2016-01-01

    Sequestration of Ce"3"+ by biogenic manganese oxides (BMOs) formed by a Mn(II)-oxidizing fungus, Acremonium strictum strain KR21-2, was examined at pH 6.0. In anaerobic Ce"3"+ solution, newly formed BMOs exhibited stoichiometric Ce"3"+ oxidation, where the molar ratio of Ce"3"+ sequestered (Ce_s_e_q) relative to Mn"2"+ released (Mn_r_e_l) was maintained at approximately two throughout the reaction. A similar Ce"3"+ sequestration trend was observed in anaerobic treatment of BMOs in which the associated Mn(II) oxidase was completely inactivated by heating at 85 °C for 1 h or by adding 50 mM NaN_3. Aerobic Ce"3"+ treatment of newly formed BMO (enzymatically active) resulted in excessive Ce"3"+ sequestration over Mn"2"+ release, yielding Ce_s_e_q/Mn_r_e_l > 200, whereas heated or poisoned BMOs released a significant amount of Mn"2"+ with lower Ce"3"+ sequestration efficiency. Consequently, self-regeneration by the Mn(II) oxidase in newly formed BMO effectively suppressed Mn"2"+ release and enhanced oxidative Ce"3"+ sequestration under aerobic conditions. Repeated treatments of heated or poisoned BMOs under aerobic conditions confirmed that oxidative Ce"3"+ sequestration continued even after most Mn oxide was released from the solid phase, indicating auto-catalytic Ce"3"+ oxidation at the solid phase produced through primary Ce"3"+ oxidation by BMO. From X-ray diffraction analysis, the resultant solid phases formed through Ce"3"+ oxidation by BMO under both aerobic and anaerobic conditions consisted of cerianite with crystal sizes of 5.00–7.23 Å. Such nano-sized CeO_2 (CeO_2_,_B_M_O) showed faster auto-catalytic Ce"3"+ oxidation than that on well-crystalized cerianite under aerobic conditions, where the normalized pseudo-first order rate constants for auto-catalytic Ce"3"+ oxidation on CeO_2_,_B_M_O was two orders of magnitude higher. Consequently, we concluded that Ce"3"+ contact with BMOs sequesters Ce"3"+ through two oxidation paths: primary Ce"3

  17. Sorption Properties of Aerogel in Liquid Nitrogen

    Science.gov (United States)

    Johnson, Wesley L.

    2006-01-01

    Aerogel products are now available as insulation materials of the future. The Cryogenics Test Laboratory at the NASA Kennedy Space Center is developing aerogel-based thermal insulation systems for space launch applications. Aerogel beads (Cabot Nanogel ) and aerogel blankets (Aspen Aerogels Spaceloft ) have outstanding ambient pressure thermal performance that makes them useful for applications where sealing is not possible. Aerogel beads are open-celled silicone dioxide and have tiny pores that run throughout the body of the bead. It has also recently been discovered that aerogel beads can be used as a filtering device for aqueous compounds at room temperature. With their hydrophobic covering, the beads absorb any non-polar substance and they can be chemically altered to absorb hot gases. The combination of the absorption and cryogenic insulating properties of aerogel beads have never been studied together. For future cryogenic insulation applications, it is crucial to know how the beads react while immersed in cryogenic liquids, most notably liquid nitrogen. Aerogel beads in loose-fill situation and aerogel blankets with composite fiber structure have been tested for absorption properties. Depending on the type of aerogel used and the preparation, preliminary results show the material can absorb up to seven times its own weight of liquid nitrogen, corresponding to a volumetric ratio of 0.70 (unit volume nitrogen per unit volume aerogel). These tests allow for an estimate on how much insulation is needed in certain situations. The theory behind the different processes of sorption is necessary for a better understanding of the preparation of the beads before they are used in an insulation system.

  18. Performance of advanced oxide fuel pins in EBR-II

    International Nuclear Information System (INIS)

    Lawrence, L.A.; Jensen, S.M.; Hales, J.W.; Karnesky, R.A.; Makenas, B.J.

    1986-05-01

    The effects of design and operating parameters on mixed-oxide fuel pin irradiation performance were established for the Hanford Engineering Development Laboratory (HEDL) advanced oxide EBR-II test series. Fourteen fuel pins breached in-reactor with reference 316 SS cladding. Seven of the breaches are attributed to FCMI. Of the remaining seven breached pins, three are attributed to local cladding over-temperatures similar to the breach mechanism for the reference oxide pins irradiated in EBR-II. FCCI was found to be a contributing factor in two high burnup, i.e., 11.7 at. % breaches. The remaining two breaches were attributed to mechanical interaction of UO 2 fuel and fission products accumulated in the lower cladding insulator gap, and a loss of cladding ductility possibly due to liquid metal embrittlement. Fuel smear density appears to have the most significant impact on lifetime. Quantitative evaluations of cladding diameter increases attributed to FCMI, established fuel smear density, burnup, and cladding thickness-to-diameter ratio as the major parameters influencing the extent of cladding strain

  19. Mercury Oxidation via Catalytic Barrier Filters Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Wayne Seames; Michael Mann; Darrin Muggli; Jason Hrdlicka; Carol Horabik

    2007-09-30

    In 2004, the Department of Energy National Energy Technology Laboratory awarded the University of North Dakota a Phase II University Coal Research grant to explore the feasibility of using barrier filters coated with a catalyst to oxidize elemental mercury in coal combustion flue gas streams. Oxidized mercury is substantially easier to remove than elemental mercury. If successful, this technique has the potential to substantially reduce mercury control costs for those installations that already utilize baghouse barrier filters for particulate removal. Completed in 2004, Phase I of this project successfully met its objectives of screening and assessing the possible feasibility of using catalyst coated barrier filters for the oxidation of vapor phase elemental mercury in coal combustion generated flue gas streams. Completed in September 2007, Phase II of this project successfully met its three objectives. First, an effective coating method for a catalytic barrier filter was found. Second, the effects of a simulated flue gas on the catalysts in a bench-scale reactor were determined. Finally, the performance of the best catalyst was assessed using real flue gas generated by a 19 kW research combustor firing each of three separate coal types.

  20. Basic science of new aerogels. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    Feasibility of making monolithic composite aerogels containing silica and natural clay minerals, synthetic clay minerals or zeolites has been demonstrated, using two different processes; up to 30 wt% of the mineral phase has been successfully added. Addition of natural and synthetic clay minerals or zeolites to silica aerosols was shown to retard densification. Composite silica aerogels showed significant surface area still present after sintering at 800 or 1000 C. For most samples, 1 wt% of the second phase is equally effective in retarding densification as 10 wt%. Composite aerogels, in general, had lower hardness values than pure silica. Hardness values were inversely proportional to aerogel pore radius.

  1. Evacuation and assembly of aerogel glazings

    DEFF Research Database (Denmark)

    Jensen, Karsten Ingerslev

    1999-01-01

    The application of monolithic silica aerogel as transparent insulation material for windows has been investigated for some years. It has been realised that a major problem of an industrial production of aerogel glazings will be the time for evacuation of the aerogel material. However, in a previous...... process, it can be considered as semi-online, and especially the capital cost is significantly lower for this method in comparison with a true online process. So hereby, a major obstacle is overcome with respect to a first industrial production of aerogel glazings.The apparatus has been constructed...

  2. Hydrogen storage property of nanoporous carbon aerogels

    International Nuclear Information System (INIS)

    Shen Jun; Liu Nianping; Ouyang Ling; Zhou Bin; Wu Guangming; Ni Xingyuan; Zhang Zhihua

    2011-01-01

    Carbon aerogels were prepared from resorcinol and formaldehyde via sol-gel process, high temperature carbonization and atmospheric pressure drying technology with solvent replacement. By changing the resorcinol-sodium carbonate molar ratio and the mass fraction of the reactants,resorcinol and formaldehyde, the pore structure of carbon aerogels can be controlled and the palladium-doped carbon aerogels were prepared.By transmission electron microscopy (TEM), X-ray diffraction (XRD) spectra, it is confirmed that the Pd exists in the skeleton structure of carbon aerogels as a form of nano simple substance pellet. The specific surface area is successfully raised by 2 times, and palladium-doped carbon aerogels with a specific surface area of 1 273 m 2 /g have been obtained by carrying out the activation process as the post-processing to the doped carbon aerogels. The hydrogen adsorption results show that the saturated hydrogen storage mass fraction of the carbon aerogels with the specific surface area of 3 212 m 2 /g is 3% in the condition of 92 K, 3.5 MPa, and 0.84% in the condition of 303 K, 3.2 MPa. In addition, the hydrogen adsorption test of palladium-doped carbon aerogels at room temperature (303 K) shows that the total hydrogen storage capacity of doped carbon aerogels is declined due to the relative small specific surface, but the hydrogen storage of unit specific surface area is enhanced. (authors)

  3. Efficient Synthesis of MCu (M = Pd, Pt, and Au) Aerogels with Accelerated Gelation Kinetics and their High Electrocatalytic Activity.

    Science.gov (United States)

    Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang; Song, Junhua; Xia, Haibing; Du, Dan; Lin, Yuehe

    2016-10-01

    To accelerate hydrogel formation and further simplify the synthetic procedure, a series of MCu (M = Pd, Pt, and Au) bimetallic aerogels is synthesized from the in situ reduction of metal precursors through enhancement of the gelation kinetics at elevated temperature. Moreover, the resultant PdCu aerogel with ultrathin nanowire networks exhibits excellent electrocatalytic performance toward ethanol oxidation, holding promise in fuel-cell applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Fungal oxidative dissolution of the Mn(II)-bearing mineral rhodochrosite and the role of metabolites in manganese oxide formation.

    Science.gov (United States)

    Tang, Yuanzhi; Zeiner, Carolyn A; Santelli, Cara M; Hansel, Colleen M

    2013-04-01

    Microbially mediated oxidation of Mn(II) to Mn(III/IV) oxides influences the cycling of metals and remineralization of carbon. Despite the prevalence of Mn(II)-bearing minerals in nature, little is known regarding the ability of microbes to oxidize mineral-hosted Mn(II). Here, we explored oxidation of the Mn(II)-bearing mineral rhodochrosite (MnCO3 ) and characteristics of ensuing Mn oxides by six Mn(II)-oxidizing Ascomycete fungi. All fungal species substantially enhanced rhodochrosite dissolution and surface modification. Mineral-hosted Mn(II) was oxidized resulting in formation of Mn(III/IV) oxides that were all similar to δ-MnO2 but varied in morphology and distribution in relation to cellular structures and the MnCO3 surface. For four fungi, Mn(II) oxidation occurred along hyphae, likely mediated by cell wall-associated proteins. For two species, Mn(II) oxidation occurred via reaction with fungal-derived superoxide produced at hyphal tips. This pathway ultimately resulted in structurally unique Mn oxide clusters formed at substantial distances from any cellular structure. Taken together, findings for these two fungi strongly point to a role for fungal-derived organic molecules in Mn(III) complexation and Mn oxide templation. Overall, this study illustrates the importance of fungi in rhodochrosite dissolution, extends the relevance of biogenic superoxide-based Mn(II) oxidation and highlights the potential role of mycogenic exudates in directing mineral precipitation. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

  5. The monolithic carbon aerogels and aerogel composites for electronics and thermal protection applications

    Science.gov (United States)

    Lu, Sheng; Guo, Hui; Zhou, Yugui; Liu, Yuanyuan; Jin, Zhaoguo; Liu, Bin; Zhao, Yingmin

    2017-09-01

    Monolithic carbon aerogels have been prepared by condensation polymerization and high temperature pyrolysis. The morphology of carbon aerogels are characterized by SEM. The pore structure is characterized by N2 adsorption-desorption technique. Monolithic carbon aerogels are mesoporous nanomaterials. Carbon fiber reinforced carbon aerogel composites are prepared by in-situ sol-gel process. Fiber reinforced carbon aerogel composites are of high mechanical strength. The thermal response of the fiber reinforced aerogel composite samples are tested in an arc plasma wind tunnel. Carbon aerogel composites show good thermal insulation capability and high temperature resistance in inert atmosphere even at ultrahigh temperature up to 1800 °C. The results show that they are suitable for applications in electrodes for supercapacitors/ Lithium-ion batteries and aerospace thermal protection area.

  6. Design and Development of Aerogel-Based Antennas for Aerospace Applications: A Final Report to the NARI Seedling

    Science.gov (United States)

    Meador, Mary Ann B.; Miranda, Felix A.

    2014-01-01

    As highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties, polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aircraft antenna systems. While they have been aggressively explored for thermal insulation, barely any effort has been made to leverage these materials for antennas or other applications that take advantage of their aforementioned attributes. In Phase I of the NARI Seedling Project, we fabricated PI aerogels with properties tailored to enable new antenna concepts with performance characteristics (wide bandwidth and high gain) and material properties (low density, environmental stability, and robustness) superior to the state of practice (SOP). We characterized electromagnetic properties, including permittivity, reflectivity, and propagation losses for the aerogels. Simple, prototype planar printed circuit patch antennas from down-selected aerogel formulations were fabricated by molding the aerogels to net shapes and by gold-metalizing the pattern onto the templates via electron beam evaporation in a clean room environment. These aerogel based antennas were benchmarked against current antenna SOP, and exhibited both broader bandwidth and comparable or higher gain performance at appreciably lower mass. Phase II focused on the success of the Phase I results pushing the PI aerogel based antenna technology further by exploring alternative antenna design (i.e., slot coupled antennas) and by examining other techniques for fabricating the antennas including ink jet printing with the goal of optimizing antenna performance and simplifying production. We also examined new aerogel formulations with better moisture and solvent resistance to survive processing conditions. In addition, we investigated more complex antenna designs including passive phased arrays such as 2x4 and 4x8 element arrays to assess the scalability of the aerogel antenna concept. Furthermore, we

  7. Monolithic Silica aerogel in superinsulating glazings

    DEFF Research Database (Denmark)

    Duer, Karsten; Svendsen, Sv Aa Højgaard

    1988-01-01

    . This phenomenon is considered being the main obstacle to incorporate the material in clear glazings but a significant improvement of the optical quality of aerogel has been observed during the last five years. A number of prototypical evacuated 500x500x28 mm aerogel double glazed units employing a new edge seal...... competetion in heating dominated climates....

  8. Wet-Spun Superelastic Graphene Aerogel Millispheres with Group Effect.

    Science.gov (United States)

    Zhao, Xiaoli; Yao, Weiquan; Gao, Weiwei; Chen, Hao; Gao, Chao

    2017-09-01

    Graphene aerogel has attracted great attention due to its unique properties, such as ultralow density, superelasticity, and high specific surface area. It shows huge potential in energy devices, high-performance pressure sensors, contaminates adsorbents, and electromagnetic wave absorbing materials. However, there still remain some challenges to further promote the development and real application of graphene aerogel including cost-effective scalable fabrication and miniaturization with group effect. This study shows millimeter-scale superelastic graphene aerogel spheres (GSs) with group effect and multifunctionality. The GSs are continuously fabricated on a large scale by wet spinning of graphene oxide liquid crystals followed by facile drying and thermal annealing. Such GS has an unusual core-shell structure with excellent elasticity and specific strength. Significantly, both horizontally and vertically grouped spheres exhibit superelasticity comparable to individual spheres, enabling it to fully recover at 95% strain, and even after 1000 compressive cycles at 70% strain, paving the way to wide applications such as pressure-elastic and adsorbing materials. The GS shows a press-fly behavior with an extremely high jump velocity up to 1.2 m s -1 . For the first time, both free and oil-adsorbed GSs are remotely manipulated on water by electrostatic charge due to their ultralow density and hydrophobic properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Development of aerogel Cherenkov detectors at Novosibirsk

    International Nuclear Information System (INIS)

    Barnyakov, A.Yu.; Barnyakov, M.Yu.; Baehr, J.; Bellunato, T.; Beloborodov, K.I.; Bobrovnikov, V.S.; Buzykaev, A.R.; Calvi, M.; Danilyuk, A.F.; Djordjadze, V.; Golubev, V.B.; Kononov, S.A.; Kravchenko, E.A.; Lipka, D.; Matteuzzi, C.; Musy, M.; Onuchin, A.P.; Perego, D.; Rodiakin, V.A.; Savinov, G.A.; Serednyakov, S.I.; Shamov, A.G.; Stephan, F.; Tayursky, V.A.; Vorobiov, A.I.

    2005-01-01

    The development of aerogel Cherenkov counters with the light collection using a wavelength shifter is described. 80 counters of this type are working in the KEDR detector. A project of similar counters for the SND detector based on 'heavy' aerogel with n=1.13 has been developed. Aerogel with a refractive index of 1.006-1.13 and dimensions of blocks up to 200x200x50mm 3 is produced by the Novosibirsk group for use in Cherenkov counters of different types. The Novosibirsk group is participating in the development of LHCb RICH as well as a beam diagnostics for a photo-injector test facility at DESY-Zeuthen. Recently we started development of RICH based on focusing aerogel (FARICH) for the endcap of the SuperBaBar. For the first time in the world the focusing aerogel with layers of different refractive indices has been produced

  10. Sorption and catalytic oxidation of Fe(II) at the surface of calcite

    NARCIS (Netherlands)

    Mettler, S.; Wolthers, M.; Charlet, L.; Von Gunten, U.

    The effect of sorption and coprecipitation of Fe(II) with calcite on the kinetics of Fe(II) oxidation was investigated. The interaction of Fe(II) with calcite was studied experimentally in the absence and presence of oxygen. The sorption of Fe(II) on calcite occurred in two distinguishable steps:

  11. Investigation of the interaction of copper(II) oxide and electron beam irradiation crosslinkable polyethylene

    International Nuclear Information System (INIS)

    Bee, Soo-Tueen; Sin, Lee Tin; Ratnam, C.T.; Haraveen, K.J.S.; Tee, Tiam-Ting; Rahmat, A.R.

    2015-01-01

    In this study, the effects of electron beam irradiation on the properties of copper(II) oxide when added to low-density polyethylene (LDPE) blends were investigated. It was found that the addition of low loading level of copper(II) oxide (⩽2 phr) to LDPE results in significantly poorer gel content and hot set results. However, the incorporation of higher loading level of copper(II) oxide (⩾3 phr) could slightly increase the degree of crosslinking in all irradiated LDPE composites. This is due to the fact that higher amounts of copper(II) oxide could slightly induce the formation of free radicals in LDPE matrix. Besides, increasing irradiation doses was also found to gradually increase the gel content of LDPE composites by generating higher amounts of free radicals. As a consequence, these higher amounts of free radicals released in the LDPE matrix could significantly increase the degree of crosslinking. The addition of copper(II) oxide could reduce the tensile strength and fracture strain (elongation at break) of LDPE composites because of poorer interfacial adhesion effect between copper(II) oxide particles and LDPE matrix. Meanwhile, increasing irradiation doses on all copper(II) oxide added LDPE composites could marginally increase the tensile strength. In addition, increasing irradiation dose could enhance the thermal stability of LDPE composites by increasing the decomposition temperature. The oxidation induction time (OIT) analysis showed that, because of the crosslinking network in the copper(II) oxide added LDPE composites, oxidation reaction is much delayed.

  12. Investigation of the interaction of copper(II) oxide and electron beam irradiation crosslinkable polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Bee, Soo-Tueen, E-mail: direct.beest@gmail.com [Department of Chemical Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Sungai Long, Bandar Sungai Long, Cheras, 43000 Kajang, Selangor (Malaysia); Sin, Lee Tin, E-mail: direct.tinsin@gmail.com [Department of Chemical Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Sungai Long, Bandar Sungai Long, Cheras, 43000 Kajang, Selangor (Malaysia); Ratnam, C.T. [Radiation Processing Technology Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Haraveen, K.J.S.; Tee, Tiam-Ting [Department of Chemical Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Sungai Long, Bandar Sungai Long, Cheras, 43000 Kajang, Selangor (Malaysia); Rahmat, A.R. [Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2015-10-01

    In this study, the effects of electron beam irradiation on the properties of copper(II) oxide when added to low-density polyethylene (LDPE) blends were investigated. It was found that the addition of low loading level of copper(II) oxide (⩽2 phr) to LDPE results in significantly poorer gel content and hot set results. However, the incorporation of higher loading level of copper(II) oxide (⩾3 phr) could slightly increase the degree of crosslinking in all irradiated LDPE composites. This is due to the fact that higher amounts of copper(II) oxide could slightly induce the formation of free radicals in LDPE matrix. Besides, increasing irradiation doses was also found to gradually increase the gel content of LDPE composites by generating higher amounts of free radicals. As a consequence, these higher amounts of free radicals released in the LDPE matrix could significantly increase the degree of crosslinking. The addition of copper(II) oxide could reduce the tensile strength and fracture strain (elongation at break) of LDPE composites because of poorer interfacial adhesion effect between copper(II) oxide particles and LDPE matrix. Meanwhile, increasing irradiation doses on all copper(II) oxide added LDPE composites could marginally increase the tensile strength. In addition, increasing irradiation dose could enhance the thermal stability of LDPE composites by increasing the decomposition temperature. The oxidation induction time (OIT) analysis showed that, because of the crosslinking network in the copper(II) oxide added LDPE composites, oxidation reaction is much delayed.

  13. Monolithic lithium-based aerogels via dispersed inorganic sol-gel method

    International Nuclear Information System (INIS)

    Xiao Shufang; Zhou Bin; Du Ai; Xu Xiang; Yang Xiaoyun; Shen Jun; Wu Guangming; Zhang Zhihua; Wan Huijun

    2008-01-01

    Monolithic lithium-based aerogels were prepared by poly acrylic acid (PAA) and propylene oxide (PO) via the dispersed inorganic sol-gel method and drying with CO 2 supercritical fluid dry process. The density of the prepared sample is about 150 g/m 3 . The microstructure of the lithium-based aerogels was characterized by TEM, IR, XPS and BET. The results show that the material mainly contains Li, C and O element s. BET surface area is up to 18.9 m 2 /g. (authors)

  14. Aerogel Projects Ongoing in MSFC's Engineering Directorate

    Science.gov (United States)

    Shular, David A.; Smithers, Gweneth A.; Plawsky, Joel L.; Whitaker, Ann F. (Technical Monitor)

    2000-01-01

    When we speak of an aerogel material, we are referring more to process and structure am to a specific substance. Aerogel, considered the lightest solid material, has been made from silica for seventy years. Resorcinol-formaldehyde, organic aerogels have been developed more recently. However, aerogel can be made from almost any type of substance, even lead. Because an aerogel is mostly air (about 99 %), the solid substance used will affect the weight very little. The term "aerogel" connotes the sol-gel process used to manufacture the material. The aerogel begins as a liquid "sol," becomes a solid "alcogel," and is then dried to become an "aerogel." The final product has a unique structure, useful for exploitation. It is an "open pore" system with nano-sized particles and pores, has very high surface area, and is highly interconnected. Besides low weight, aerogels have ultimate (lowest) values in other properties: thermal conductivity, refractive index, sound speed, and dielectric constant. Aerogels were first prepared in 1931 by Steven Kistler, who used a supercritical drying step to replace the liquid in a gel with air, preserving the structure (1). Kistler's procedure involved a water-to-alcohol exchange step; in the 1970's, this step was eliminated when a French investigator introduced the use of tetramethylorthosilicate. Still, alcohol drying involved dangerously high temperatures and pressures. In the 1980's, the Microstructured Materials Group at Berkeley Laboratory found that the alcohol in the gel could be replaced with liquid carbon dioxide before supercritical drying, which greatly improved safety (2). 'Me most recent major contribution has been that of Deshpande, Smith and Brinker in New Mexico, who are working to eliminate the supercritical drying step (3). When aerogels were first being developed, they were evaporatively dried. However, the wet gel, when dried, underwent severe shrinkage and cracking; this product was termed "xerogel." When the

  15. The effects of iron(II) on the kinetics of arsenic oxidation and sorption on manganese oxides.

    Science.gov (United States)

    Wu, Yun; Li, Wei; Sparks, Donald L

    2015-11-01

    In this study, As(III) oxidation kinetics by a poorly-crystalline phyllomanganate (δ-MnO2) in the presence and absence of dissolved Fe(II) was investigated using stirred-flow and batch experiments. Chemically synthetic δ-MnO2 was reacted with four influent solutions, containing the same As(III) concentration but different Fe(II) concentrations, at pH 6. The results show an initial rapid As(III) oxidation by δ-MnO2, which is followed by an appreciably slow reaction after 8h. In the presence of Fe(II), As(III) oxidation is inhibited due to the competitive oxidation of Fe(II) as well as the formation of Fe(III)-(hydr)oxides on the δ-MnO2 surface. However, the sorption of As(III), As(V) and Mn(II) are increased, for the newly formed Fe(III)-(hydr)oxides provide additional sorption sites. This study suggests that the competitive oxidation of Fe(II) and consequently the precipitation of Fe(III) compounds on the δ-MnO2 surface play an important role in As(III) oxidation and As sequestration. Understanding these processes would be helpful in developing in situ strategies for remediation of As-contaminated waters and soils. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Secretome-based Manganese(II) Oxidation by Filamentous Ascomycete Fungi

    Science.gov (United States)

    Zeiner, C. A.; Purvine, S.; Zink, E.; Paša-Tolić, L.; Chaput, D.; Wu, S.; Santelli, C. M.; Hansel, C. M.

    2017-12-01

    Manganese (Mn) oxides are among the strongest oxidants in the environment, and Mn(II) oxidation to Mn(III/IV) (hydr)oxides includes both abiotic and microbially-mediated processes. While white-rot Basidiomycete fungi oxidize Mn(II) using laccases and Mn peroxidases in association with lignocellulose degradation, the mechanisms by which filamentous Ascomycete fungi oxidize Mn(II) and a physiological role for Mn(II) oxidation in these organisms remain poorly understood. Through a combination of chemical and in-gel assays, bulk mass spectrometry, and iTRAQ proteomics, we demonstrate enzymatic Mn(II) oxidation in the secretomes of three phylogenetically diverse Ascomycetes that were isolated from Mn-laden sediments. Candidate Mn(II)-oxidizing enzymes were species-specific and included bilirubin oxidase and tyrosinase in Stagonospora sp. SRC1lsM3a, GMC oxidoreductase in Paraconiothyrium sporulosum AP3s5-JAC2a, and FAD-binding oxidoreductases in Pyrenochaeta sp. DS3sAY3a. These findings were supported by full proteomic characterization of the secretomes, which revealed a lack of Mn, lignin, and versatile peroxidases in these Ascomycetes but a substantially higher proportion of LMCOs and GMC oxidoreductases compared to wood-rot Basidiomycetes. We also identified the potential for indirect enzymatic Mn(II) oxidation by hydroxyl radical, as the secretomes were rich in diverse lignocellulose-degrading enzymes that could participate in Fenton chemistry. A link between Mn(II) oxidation and carbon oxidation analogous to white-rot Basidiomycetes remains unknown in these Ascomycetes. Interestingly, growth rates on rich medium were unaffected by the presence of Mn(II), and the production of Mn(II)-oxidizing proteins in the secretome was constitutive and not inducible by Mn(II). Thus, no physiological benefit of Mn(II) oxidation in these Ascomycetes has yet been identified, and Mn(II) oxidation appears to be a side reaction. Future work will explore the lignin-degrading capacity of

  17. Aerogels from Chitosan Solutions in Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Gonzalo Santos-López

    2017-12-01

    Full Text Available Chitosan aerogels conjugates the characteristics of nanostructured porous materials, i.e., extended specific surface area and nano scale porosity, with the remarkable functional properties of chitosan. Aerogels were obtained from solutions of chitosan in ionic liquids (ILs, 1-butyl-3-methylimidazolium acetate (BMIMAc, and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc, in order to observe the effect of the solvent in the structural characteristics of this type of materials. The process of elaboration of aerogels comprised the formation of physical gels through anti-solvent vapor diffusion, liquid phase exchange, and supercritical CO2 drying. The aerogels maintained the chemical identity of chitosan according to Fourier transform infrared spectrophotometer (FT-IR spectroscopy, indicating the presence of their characteristic functional groups. The internal structure of the obtained aerogels appears as porous aggregated networks in microscopy images. The obtained materials have specific surface areas over 350 m2/g and can be considered mesoporous. According to swelling experiments, the chitosan aerogels could absorb between three and six times their weight of water. However, the swelling and diffusion coefficient decreased at higher temperatures. The structural characteristics of chitosan aerogels that are obtained from ionic liquids are distinctive and could be related to solvation dynamic at the initial state.

  18. Development of aerogel Cherenkov counters at Novosibirsk

    International Nuclear Information System (INIS)

    Barnyakov, A.Yu.; Barnyakov, M.Yu.; Baehr, J.; Bellunato, T.; Beloborodov, K.I.; Bobrovnikov, V.S.; Buzykaev, A.R.; Calvi, M.; Danilyuk, A.F.; Djordjadze, V.; Golubev, V.B.; Kononov, S.A.; Kravchenko, E.A.; Lipka, D.; Matteuzzi, C.; Musy, M.; Onuchin, A.P.; Perego, D.; Rodiakin, V.A.; Savinov, G.A.; Serednyakov, S.I.; Shamov, A.G.; Stephan, F.; Tayursky, V.A.; Vorobiov, A.I.

    2006-01-01

    The work on aerogel Cherenkov counters was started in Novosibirsk in 1986. Production of aerogels with refractive indices of 1.006-1.13 and thicknesses of blocks up to 50mm was developed. The light absorption length at 400nm is 5-7m, the scattering length is 4-5cm. By these parameters, the Novosibirsk aerogel is one of the best in the world. The ASHIPH Cherenkov counters with light collection on wavelength shifters have been developed. The ASHIPH system of the KEDR detector contains 1000l of aerogel. The π/K separation is 4.5σ. A project of ASHIPH counters for the SND detector has been developed. Aerogel RICH for LHCb gives a possibility to identify hadrons in the momentum range of 2-10GeV/c. The Novosibirsk group is developing an aerogel RICH for the endcap for the SuperBaBar project. Calculations performed by a group of physicists from Novosibirsk and DESY-Zeuthen have shown that aerogel radiators enable to achieve time resolution up to 20fs

  19. Thermodynamic controls on the kinetics of microbial low-pH Fe(II) oxidation.

    Science.gov (United States)

    Larson, Lance N; Sánchez-España, Javier; Kaley, Bradley; Sheng, Yizhi; Bibby, Kyle; Burgos, William D

    2014-08-19

    Acid mine drainage (AMD) is a major worldwide environmental threat to surface and groundwater quality. Microbial low-pH Fe(II) oxidation could be exploited for cost-effective AMD treatment; however, its use is limited because of uncertainties associated with its rate and ability to remove Fe from solution. We developed a thermodynamic-based framework to evaluate the kinetics of low-pH Fe(II) oxidation. We measured the kinetics of low-pH Fe(II) oxidation at five sites in the Appalachian Coal Basin in the US and three sites in the Iberian Pyrite Belt in Spain and found that the fastest rates of Fe(II) oxidation occurred at the sites with the lowest pH values. Thermodynamic calculations showed that the Gibbs free energy of Fe(II) oxidation (ΔG(oxidation)) was also most negative at the sites with the lowest pH values. We then conducted two series of microbial Fe(II) oxidation experiments in laboratory-scale chemostatic bioreactors operated through a series of pH values (2.1-4.2) and found the same relationships between Fe(II) oxidation kinetics, ΔG(oxidation), and pH. Conditions that favored the fastest rates of Fe(II) oxidation coincided with higher Fe(III) solubility. The solubility of Fe(III) minerals, thus plays an important role on Fe(II) oxidation kinetics. Methods to incorporate microbial low-pH Fe(II) oxidation into active and passive AMD treatment systems are discussed in the context of these findings. This study presents a simplified model that describes the relationship between free energy and microbial kinetics and should be broadly applicable to many biogeochemical systems.

  20. Low-temperature Synthesis of Tin(II) Oxide From Tin(II) ketoacidoximate Precursor

    KAUST Repository

    Alshankiti, Buthainah

    2015-04-01

    Sn (II) oxide finds numerous applications in different fields such as thin film transistors1, solar cells2 and sensors.3 In this study we present the fabrication of tin monoxide SnO by using Sn (II) ketoacid oximate complexes as precursors. Tin (II) ketoacidoximates of the type [HON=CRCOO]2Sn where R= Me 1, R= CH2Ph 2, and [(MeON=CMeCOO)3Sn]- NH4 +.2H2O 3 were synthesized by in situ formation of the ketoacid oximate ligand. The crystal structures were determined via single crystal X- ray diffraction of the complexes 1-3 revealed square planar and square pyramidal coordination environments for the Sn atom. Intramolecular hydrogen bonding is observed in all the complexes. Furthermore, the complexes were characterized by Infrared (IR), Nuclear Magnetic Resonance (NMR) and elemental analysis. From thermogravimetric analysis of 1-3, it was found that the complexes decomposed in the range of 160 – 165 oC. Analysis of the gases evolved during decomposition indicated complete loss of the oximato ligand in one step and the formation of SnO. Spin coating of 1 on silicon or glass substrate show uniform coating of SnO. Band gaps of SnO films were measured and found to be in the range of 3.0 – 3.3 eV by UV-Vis spectroscopy. X-ray photoelectron spectroscopy indicated surface oxidation of the SnO film. Heating 1 above 140 oC in air gives SnO of size ranging from 10 – 500 nm and is spherical in shape. The SnO nanomaterial is characterized by powder X-ray diffraction(XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM).

  1. Carbon aerogel electrodes for direct energy conversion

    Science.gov (United States)

    Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

    1997-01-01

    A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome.

  2. Preparation and Characterization of a Calcium Carbonate Aerogel

    Directory of Open Access Journals (Sweden)

    Johann Plank

    2009-01-01

    Full Text Available We report on a facile method for the preparation of a calcium carbonate aerogel consisting of aggregated secondary vaterite particles with an approximate average diameter of 50 nm. It was synthesized via a sol-gel process by reacting calcium oxide with carbon dioxide in methanol and subsequent supercritical drying of the alcogel with carbon dioxide. The resulting monolith was opaque, brittle and had overall dimensions of 6×2×1 cm. It was characterized by X-ray powder diffraction, nitrogen adsorption method (BET, and scanning electron microscopy.

  3. Biological iron(II) oxidation as pre-treatment to limestone neutralisation of acid water

    CSIR Research Space (South Africa)

    Maree

    1998-01-01

    Full Text Available at investigating the effect of surface area of the medium that supports bacterial growth on the rate of biological iron (II) oxidation. The study showed that the biological iron (II) oxidation rate is directly proportional to the square root of the medium specific...

  4. Microbial Fe(II) oxidation at circumneutral pH: Reaction kinetics, mineral products, and distribution of neutrophilic iron oxidizers in wetland soils

    NARCIS (Netherlands)

    Vollrath, S.

    2012-01-01

    Multiple studies have shown that neutrophilic Fe(II) oxidizers can conserve energy from Fe(II) oxidation, however, it is still unclear how they can compete against the fast abiotic reaction at neutral pH, or to which extent these bacteria increase the overall Fe(II) oxidation rate. Similar to

  5. Fibrous-Ceramic/Aerogel Composite Insulating Tiles

    Science.gov (United States)

    White, Susan M.; Rasky, Daniel J.

    2004-01-01

    Fibrous-ceramic/aerogel composite tiles have been invented to afford combinations of thermal-insulation and mechanical properties superior to those attainable by making tiles of fibrous ceramics alone or aerogels alone. These lightweight tiles can be tailored to a variety of applications that range from insulating cryogenic tanks to protecting spacecraft against re-entry heating. The advantages and disadvantages of fibrous ceramics and aerogels can be summarized as follows: Tiles made of ceramic fibers are known for mechanical strength, toughness, and machinability. Fibrous ceramic tiles are highly effective as thermal insulators in a vacuum. However, undesirably, the porosity of these materials makes them permeable by gases, so that in the presence of air or other gases, convection and gas-phase conduction contribute to the effective thermal conductivity of the tiles. Other disadvantages of the porosity and permeability of fibrous ceramic tiles arise because gases (e.g., water vapor or cryogenic gases) can condense in pores. This condensation contributes to weight, and in the case of cryogenic systems, the heat of condensation undesirably adds to the heat flowing to the objects that one seeks to keep cold. Moreover, there is a risk of explosion associated with vaporization of previously condensed gas upon reheating. Aerogels offer low permeability, low density, and low thermal conductivity, but are mechanically fragile. The basic idea of the present invention is to exploit the best features of fibrous ceramic tiles and aerogels. In a composite tile according to the invention, the fibrous ceramic serves as a matrix that mechanically supports the aerogel, while the aerogel serves as a low-conductivity, low-permeability filling that closes what would otherwise be the open pores of the fibrous ceramic. Because the aerogel eliminates or at least suppresses permeation by gas, gas-phase conduction, and convection, the thermal conductivity of such a composite even at

  6. A saxs study of silica aerogels

    International Nuclear Information System (INIS)

    Craievich, A.F.

    1986-01-01

    Aerogels produced by hypercritical drying of gels from hydrolysis of TMOS (Tetramethoxysilane) in various pH conditions and subjected to a densification process were studied by SAXS using LURE synchrotron facility. The evaluation of scattering data combined with BET measurements leads to a model of aerogels consisting of a light density matrix in which meso-and macro-pores are embedded. (Author) [pt

  7. Study of ageing effects in aerogel

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Coluzza, C.; Longo, G.; Matteuzzi, C.; Musy, M.; Negri, P.; Perego, D.L.

    2004-01-01

    Ageing effects on aerogel due to irradiation and absorption of humidity have been investigated. Aerogel tiles have been exposed to γ radiation from a 60 Co source and to proton and neutron high intensity beams. The transmittance has been monitored in the wavelength range between 200 and 800 nm, determining the clarity factor C as a function of the increasing dose of irradiation. The index of refraction n was also measured

  8. Study of ageing effects in aerogel

    CERN Document Server

    Bellunato, T F; Coluzza, C; Longo, G; Matteuzzi, C; Musy, M; Negri, P; Perego, D L

    2004-01-01

    Ageing effects on aerogel due to irradiation and absorption of humidity have been investigated. Aerogel tiles have been exposed to gamma radiation from a 60-Co source and to proton and neutron high intensity beams. The transmittance has been monitored in the wavelength range between 200 nm and 800 nm, determining the clarity factor C as a function of the increasing dose of irradiation. The index of refraction n was also measured.

  9. Preparation, Characterization and Activity of a Peptide-Cellulosic Aerogel Protease Sensor from Cotton

    Directory of Open Access Journals (Sweden)

    J. Vincent Edwards

    2016-10-01

    Full Text Available Nanocellulosic aerogels (NA provide a lightweight biocompatible material with structural properties, like interconnected high porosity and specific surface area, suitable for biosensor design. We report here the preparation, characterization and activity of peptide-nanocellulose aerogels (PepNA made from unprocessed cotton and designed with protease detection activity. Low-density cellulosic aerogels were prepared from greige cotton by employing calcium thiocyanate octahydrate/lithium chloride as a direct cellulose dissolving medium. Subsequent casting, coagulation, solvent exchange and supercritical carbon dioxide drying afforded homogeneous cellulose II aerogels of fibrous morphology. The cotton-based aerogel had a porosity of 99% largely dominated by mesopores (2–50 nm and an internal surface of 163 m2·g−1. A fluorescent tripeptide-substrate (succinyl-alanine-proline-alanine-4-amino-7-methyl-coumarin was tethered to NA by (1 esterification of cellulose C6 surface hydroxyl groups with glycidyl-fluorenylmethyloxycarbonyl (FMOC, (2 deprotection and (3 coupling of the immobilized glycine with the tripeptide. Characterization of the NA and PepNA included techniques, such as elemental analysis, mass spectral analysis, attenuated total reflectance infrared imaging, nitrogen adsorption, scanning electron microscopy and bioactivity studies. The degree of substitution of the peptide analog attached to the anhydroglucose units of PepNA was 0.015. The findings from mass spectral analysis and attenuated total reflectance infrared imaging indicated that the peptide substrate was immobilized on to the surface of the NA. Nitrogen adsorption revealed a high specific surface area and a highly porous system, which supports the open porous structure observed from scanning electron microscopy images. Bioactivity studies of PepNA revealed a detection sensitivity of 0.13 units/milliliter for human neutrophil elastase, a diagnostic biomarker for inflammatory

  10. Tin( ii ) ketoacidoximates: synthesis, X-ray structures and processing to tin( ii ) oxide

    KAUST Repository

    Khanderi, Jayaprakash

    2015-10-21

    Tin(ii) ketoacidoximates of the type [HONCRCOO]Sn (R = Me 1, CHPh 2) and (MeONCMeCOO)Sn] NH·2HO 3 were synthesized by reacting pyruvate- and hydroxyl- or methoxylamine RONH (R = H, Me) with tin(ii) chloride dihydrate SnCl·2HO. The single crystal X-ray structure reveals that the geometry at the Sn atom is trigonal bipyramidal in 1, 2 and trigonal pyramidal in 3. Inter- or intramolecular hydrogen bonding is observed in 1-3. Thermogravimetric (TG) analysis shows that the decomposition of 1-3 to SnO occurs at ca. 160 °C. The evolved gas analysis during TG indicates complete loss of the oximato ligand in one step for 1 whereas a small organic residue is additionally removed at temperatures >400 °C for 2. Above 140 °C, [HONC(Me)COO]Sn (1) decomposes in air to spherical SnO particles of size 10-500 nm. Spin coating of 1 on Si or a glass substrate followed by heating at 200 °C results in a uniform film of SnO. The band gap of the produced SnO film and nanomaterial was determined by diffuse reflectance spectroscopy to be in the range of 3.0-3.3 eV. X-ray photoelectron spectroscopy indicates surface oxidation of the SnO film to SnO in ambient atmosphere.

  11. Aerogels Materials as Space Debris Collectors

    Directory of Open Access Journals (Sweden)

    Thierry Woignier

    2013-01-01

    Full Text Available Material degradation due to the specific space environment becomes a key parameter for space missions. The use of large surface of brittle materials on satellites can produce, if impacted by hypervelocity particles, ejected volumes of mater 100 times higher than the impacting one. The presented work is devoted to the use of silica aerogels as passive detectors. Aerogels have been exposed to the low earth orbit of the ISS for 18 months. The study describes the aerogels process and the choice of synthesis parameters in such a way to get expected features in terms of porosity, mechanical properties, internal stresses, and transparency. Low-density aerogels (0.09 g·cm−3 have been prepared. The control of transparency necessary to see and identify particles and fragments collected is obtained using a base catalysis during gel synthesis. After return to earth, the aerogels samples have been observed using optical microscopy to detect and quantify craters on the exposed surface. First results obtained on a small part of the aerogels indicate a large number of debris collected in the materials.

  12. Influence of Aerogel Morphology and Reinforcement Architecture on Gas Convection in Aerogel Composites

    Science.gov (United States)

    Hurwitz, Frances I.; Meyer, Matthew; Guo, Haiquan; Rogers, Richard B.; DeMange, Jeffrey J.; Richardson, Hayley

    2016-01-01

    A variety of thermal protection applications require lightweight insulation capable of withstanding temperatures well above 900 C. Aerogels offer extremely low-density thermal insulation due to their mesoporous structure, which inhibits both gas convection and solid conduction. Silica aerogel systems are limited to use temperatures of 600-700 C, above which they sinter. Alumina aerogels maintain a porous structure to higher temperatures than silica, before transforming to -alumina and densifying. We have synthesized aluminosilicate aerogels capable of maintaining higher surface areas at temperatures above 1100 C than an all-alumina aerogel using -Boehmite as the aluminum source and tetraethoxysilane (TEOS) as the silicon source. The pore structure of these aerogels varies with thermal exposure temperature and time, as the aluminosilicate undergoes a variety of phase changes to form transition aluminas. Transformation to -alumina is inhibited by incorporation of silica into the alumina lattice. The aerogels are fragile, but can be reinforced using a large variety of ceramic papers, felts or fabrics. The objective of the current study is to characterize the influence of choice of reinforcement and architecture on gas permeability of the aerogel composites in both the as fabricated condition and following thermal exposure, as well as understand the effects of incorporating hydrophobic treatments in the composites.

  13. Adsorption behavior of multiwall carbon nanotube/iron oxide magnetic composites for Ni(II) and Sr(II)

    International Nuclear Information System (INIS)

    Chen Changlun; Hu Jun; Shao Dadong; Li Jiaxing; Wang Xiangke

    2009-01-01

    Multiwall carbon nanotube (MWCNT)/iron oxide magnetic composites were prepared, and were characterized by scan electron microscopy using a field emission scanning electron microscope, X-ray diffraction and vibrating sample magnetometer. The adsorptions of Ni(II) and Sr(II) onto MWCNT/iron oxide magnetic composites were studied as a function of pH and ionic strength. The results show that the adsorptions of Ni(II) and Sr(II) on the magnetic composites is strongly dependent on pH and ionic strength. The adsorption capacity of the magnetic composites is much higher than that of MWCNTs and iron oxides. The solid magnetic composites can be separated from the solution by a magnetic process. The Langmuir model fits the adsorption isotherm data of Ni(II) better than the Freundlich model. Results of desorption study shows that Ni(II) adsorbed onto the magnetic composites can be easily desorbed at pH < 2.0. MWCNT/iron oxide magnetic composites may be a promising candidate for pre-concentration and solidification of heavy metal ions and radionuclides from large volumes of aqueous solution, as required for remediation purposes.

  14. Cellulose aerogels functionalized with polypyrrole and silver nanoparticles: In-situ synthesis, characterization and antibacterial activity.

    Science.gov (United States)

    Wan, Caichao; Li, Jian

    2016-08-01

    Green porous and lightweight cellulose aerogels have been considered as promising candidates to substitute some petrochemical host materials to support various nanomaterials. In this work, waste wheat straw was collected as feedstock to fabricate cellulose hydrogels, and a green inexpensive NaOH/polyethylene glycol solution was used as cellulose solvent. Prior to freeze-drying treatment, the cellulose hydrogels were integrated with polypyrrole and silver nanoparticles by easily-operated in-situ oxidative polymerization of pyrrole using silver ions as oxidizing agent. The tri-component hybrid aerogels were characterized by scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, and X-ray diffraction. Moreover, the antibacterial activity of the hybrid aerogels against Escherichia coli (Gram-negative), Staphylococcus aureus (Gram-positive) and Listeria monocytogenes (intracellular bacteria) was qualitatively and quantitatively investigated by parallel streak method and determination of minimal inhibitory concentration, respectively. This work provides an example of combining cellulose aerogels with nanomaterials, and helps to develop novel forms of cellulose-based functional materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Synthesis and characterization of a nanocrystalline diamond aerogel

    Energy Technology Data Exchange (ETDEWEB)

    Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.; Laurence, Ted A.; Kilcoyne, A. L. David; Wang, Yinmin; Willey, Trevor M.; Visbeck, Kenneth S.; Fakra, Sirine C.; Evans, William J.; Zaug, Joseph M.; Satcher, Jr., Joe H.

    2011-07-06

    Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel's void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material reveal the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel.

  16. Durable polymer-aerogel based superhydrophobic coatings, a composite material

    Science.gov (United States)

    Kissel, David J; Brinker, Charles Jeffrey

    2014-03-04

    Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

  17. Durable polymer-aerogel based superhydrophobic coatings: a composite material

    Science.gov (United States)

    Kissel, David J.; Brinker, Charles Jeffrey

    2016-02-02

    Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

  18. Aerogels: transparent and super-insulating materials; Les aerogels: isolants transparent-super isolants

    Energy Technology Data Exchange (ETDEWEB)

    Melka, S.; Rigacci, A.; Achard, P.; Bezian, J.J. [Ecole des Mines de Paris, 06 - Sophia-Antipolis (France); Sallee, H.; Chevalier, B. [Centre des Sciences et Techniques du Batiment, 38 - Saint-Martin-d`Heres (France)

    1996-12-31

    Recent studies have demonstrated the super-insulating properties of silica aerogel in its monolithic or finely divided state. In its monolithic state, this material conciliates excellent thermal insulation performances, a good transmission of visible light and interesting acoustic properties. Also its amazing structural characteristics (lightness, high global porosity, small diameter of pores) are particularly interesting for its use in double glazing windows as transparent insulating spacer. The aim of the work carried out by the Energetic Centre of the Ecole des Mines of Paris is to understand the thermal transfer phenomena in all forms of silica aerogel. In this paper, the main steps of the synthesis process of monolithic silica aerogel is presented with the thermal conductivities obtained. Then, a model is built to describe the thermal transfer mechanisms in finely divided aerogel beds. Finally, the hot wire thermal characterization method is presented and the results obtained on silica aerogels are discussed. (J.S.) 16 refs.

  19. Formation of iron (hydr)oxides during the abiotic oxidation of Fe(II) in the presence of arsenate.

    Science.gov (United States)

    Song, Jia; Jia, Shao-Yi; Yu, Bo; Wu, Song-Hai; Han, Xu

    2015-08-30

    Abiotic oxidation of Fe(II) is a common pathway in the formation of Fe (hydr)oxides under natural conditions, however, little is known regarding the presence of arsenate on this process. In hence, the effect of arsenate on the precipitation of Fe (hydr)oxides during the oxidation of Fe(II) is investigated. Formation of arsenic-containing Fe (hydr)oxides is constrained by pH and molar ratios of As:Fe during the oxidation Fe(II). At pH 6.0, arsenate inhibits the formation of lepidocrocite and goethite, while favors the formation of ferric arsenate with the increasing As:Fe ratio. At pH 7.0, arsenate promotes the formation of hollow-structured Fe (hydr)oxides containing arsenate, as the As:Fe ratio reaches 0.07. Arsenate effectively inhibits the formation of magnetite at pH 8.0 even at As:Fe ratio of 0.01, while favors the formation of lepidocrocite and green rust, which can be latterly degenerated and replaced by ferric arsenate with the increasing As:Fe ratio. This study indicates that arsenate and low pH value favor the slow growth of dense-structured Fe (hydr)oxides like spherical ferric arsenate. With the rapid oxidation rate of Fe(II) at high pH, ferric (hydr)oxides prefer to precipitate in the formation of loose-structured Fe (hydr)oxides like lepidocrocite and green rust. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. The Adsorption of Cd(II on Manganese Oxide Investigated by Batch and Modeling Techniques

    Directory of Open Access Journals (Sweden)

    Xiaoming Huang

    2017-09-01

    Full Text Available Manganese (Mn oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999. The adsorption of Cd(II on Mn oxide significantly decreased with increasing ionic strength at pH < 5.0, whereas Cd(II adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II on Mn oxide at pH < 5.0 and pH > 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd at low pH and inner-sphere surface complexation sites (SOCd+ and (SO2CdOH− species at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface.

  1. Properties of aerogels in glazings

    DEFF Research Database (Denmark)

    Schultz, Jørgen Munthe

    1998-01-01

    This report describes the final tests carried out on an advanced apparatus for measurement of thermal conductivity of materials at atmospheric pressure and different levels of evacuation. The apparatus was designed and constructed in the phase 1 of the project. Difficulties with the control system...... have been solved and measurements have been carried out on common polystyrene foam insulation at atmospheric pressure. The measurements have been compared with results from reference measurements and a difference of only 0.3% was found in measured thermal conductivity. Measurements on monolithic silica...... aerogel were performed at 5 different pressure levels in the range 0.2 - 1000 hPa. The measured equivalent thermal conductivity is in the range 8.9 - 16.4 mW/(m K) which corresponds very well with results obtained by institutes in Germany and France....

  2. Da-KGM based GO-reinforced FMBO-loaded aerogels for efficient arsenic removal in aqueous solution.

    Science.gov (United States)

    Ye, Shuxin; Jin, Weiping; Huang, Qing; Hu, Ying; Li, Yan; Li, Jing; Li, Bin

    2017-01-01

    Composites based on deacetylated konjac glucomannan (Da-KGM) and graphene oxide (GO) aerogels with iron and manganese oxides (FMBO) for effective removal of arsenic from contaminated water. Da-KGM, which was used as supporting composite matrix here, were firstly treated with GO and loaded FMBO. The obtained Da-KGM/GO/FMBO composite aerogels were characterized by compression test, thermo gravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The characteristic results showed that addition of GO exhibited enhanced mechanical properties towards Da-KGM aerogels. What's more, results of FTIR indicated the strong intermolecular hydrogen bond interaction between KGM and GO. Batch adsorption tests were used to evaluate arsenic removal capacity. Da-KGM/GO loaded FMBO composite aerogels exhibited high adsorption ability for arsenite [As(III)] and arsenate [As(V)]. The adsorption results showed that the arsenic for both arsenite [As(III)] and arsenate [As(V)] removal process followed a pseudo-second-order rate equation and Langmuir monolayer adsorption. The maximum As(III) and As(V) uptake capacity of Da-KGM/GO(10%)/FMBO composite aerogels reached 30.21mgg -1 and 12.08mgg -1 respectively according to Langmuir isotherm at pH 7 and 323K. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Bluedec in product design : Isolatiemateriaal op basis van aerogel

    NARCIS (Netherlands)

    Beurden, van K.M.M. (Karin); Goselink, E.A. (Erik)

    2014-01-01

    Aerogel is een zeer kostbaar voor de ruimtevaart ontwikkeld basismateriaal. Bluedec is een isolatiemateriaal bestaande uit een non woven kunststof dat met deze aerogel geïmpregneerd is. Hierdoor ontstaat een zeer goed isolerend materiaal dat goedkoper is dan aerogel. De

  4. Hydrolysis of bis(dimethylamido)tin to tin (II) oxyhydroxide and its selective transformation into tin (II) or tin (IV) oxide

    KAUST Repository

    Khanderi, Jayaprakash; Shi, Lei; Rothenberger, Alexander

    2015-01-01

    Sn6O4(OH)4, a hydrolysis product of Sn(NMe2)2, is transformed to tin (II) or tin (IV) oxide by solid and solution phase processing. Tin (II) oxide is formed by heating Sn6O4(OH)4 at ≤200 °C in air or under inert atmosphere. Tin (IV) oxide

  5. The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques.

    Science.gov (United States)

    Huang, Xiaoming; Chen, Tianhu; Zou, Xuehua; Zhu, Mulan; Chen, Dong; Pan, Min

    2017-09-28

    Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R² > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X₂Cd) at low pH and inner-sphere surface complexation sites (SOCd⁺ and (SO)₂CdOH - species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water-mineral interface.

  6. The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques

    Science.gov (United States)

    Huang, Xiaoming; Chen, Tianhu; Zou, Xuehua; Zhu, Mulan; Chen, Dong

    2017-01-01

    Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd) at low pH and inner-sphere surface complexation sites (SOCd+ and (SO)2CdOH− species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface. PMID:28956849

  7. Oxidative C-C bond cleavage of 1,2-diols by silver(II)

    International Nuclear Information System (INIS)

    Kumar, A.

    1981-01-01

    Oxidation of ethylene glycol and related compounds by Ag(II) has been investigated. Complexation of these substrates by Ag(II) precedes their oxidation. Oxidation occurs through electron transfer from an OH group to the Ag(II) within the complex resulting in the formation of alkoxyl-type radicals. The radicals thus formed undergo β-scission to give cleavage products. For ethylene glycol a complexation rate 1.3 x 10 6 M -1 s -1 and oxidation rate approx. 3 x 10 3 s -1 were observed. A general trend for the type of the substrates which would undergo C-C bond scission by Ag(II) is discussed

  8. Plasmonic enhancement of visible-light water splitting with Au-TiO2 composite aerogels

    Science.gov (United States)

    Desario, Paul A.; Pietron, Jeremy J.; Devantier, Devyn E.; Brintlinger, Todd H.; Stroud, Rhonda M.; Rolison, Debra R.

    2013-08-01

    We demonstrate plasmonic enhancement of visible-light-driven splitting of water at three-dimensionally (3D) networked gold-titania (Au-TiO2) aerogels. The sol-gel-derived ultraporous composite nanoarchitecture, which contains 1 to 8.5 wt% Au nanoparticles and titania in the anatase form, retains the high surface area and mesoporosity of unmodified TiO2 aerogels and maintains stable dispersion of the ~5 nm Au guests. A broad surface plasmon resonance (SPR) feature centered at ~550 nm is present for the Au-TiO2 aerogels, but not Au-free TiO2 aerogels, and spans a wide range of the visible spectrum. Gold-derived SPR in Au-TiO2 aerogels cast as films on transparent electrodes drives photoelectrochemical oxidation of aqueous hydroxide and extends the photocatalytic activity of TiO2 from the ultraviolet region to visible wavelengths exceeding 700 nm. Films of Au-TiO2 aerogels in which Au nanoparticles are deposited on pre-formed TiO2 aerogels by a deposition-precipitation method (DP Au/TiO2) also photoelectrochemically oxidize aqueous hydroxide, but less efficiently than 3D Au-TiO2, despite having an essentially identical Au nanoparticle weight fraction and size distribution. For example, 3D Au-TiO2 containing 1 wt% Au is as active as DP Au/TiO2 with 4 wt% Au. The higher photocatalytic activity of 3D Au-TiO2 derives only in part from its ability to retain the surface area and porosity of unmodified TiO2 aerogel. The magnitude of improvement indicates that in the 3D arrangement either a more accessible photoelectrochemical reaction interphase (three-phase boundary) exists or more efficient conversion of excited surface plasmons into charge carriers occurs, thereby amplifying reactivity over DP Au/TiO2. The difference in photocatalytic efficiency between the two forms of Au-TiO2 demonstrates the importance of defining the structure of Au||TiO2 interfaces within catalytic Au-TiO2 nanoarchitectures.We demonstrate plasmonic enhancement of visible-light-driven splitting of

  9. Preparation and characterization of phloroglucinol-formaldehyde aerogel

    International Nuclear Information System (INIS)

    Huang Changgang; China Academy of Engineering Physics, Mianyang; Tang Yongjian; Wang Chaoyang; Yan Hongmei

    2006-01-01

    Phloroglucinol-formaldehyde (PF) aerogels and carbonized PF (CPF) aerogels were prepared from Phloroglucinol (P) and Formaldehyde (F) by sol-gel, solvent exchanging, supercritical drying and carbonization processes. The aerogel has a large specific surface area, continuous nano-network and porous structure. The density and mean porosity radius will enlarge after being carbonized, while the specific surface area will be influenced little. The micro-structure and density of aerogel are controlled by concentration of total reactants and catalyzer, respectively. Aerogels with different micro-structure and different density fit for ICF targets can be prepared by optimizing synthesis conditions. (authors)

  10. Phototrophic Fe(II-oxidation in the chemocline of a ferruginous meromictic lake

    Directory of Open Access Journals (Sweden)

    Xavier Alexis eWalter

    2014-12-01

    Full Text Available Precambrian Banded Iron Formation (BIF deposition was conventionally attributed to the precipitation of iron-oxides resulting from the abiotic reaction of ferrous iron (Fe(II with photosynthetically-produced oxygen. Earliest traces of oxygen date from 2.7 Ga, thus raising questions as to what may have caused BIF precipitation before oxygenic photosynthesis evolved. The discovery of anoxygenic phototrophic bacteria thriving through the oxidation of Fe(II has provided support for a biological origin for some BIFs, but despite reports suggesting that anoxygenic phototrophs may oxidize Fe(II in the environment, a model ecosystem of an ancient ocean where they are demonstrably active was lacking. Here we show that anoxygenic phototrophic bacteria contribute to Fe(II oxidation in the water column of the ferruginous sulfate-poor, meromictic lake La Cruz (Spain. We observed in-situ photoferrotrophic activity through stimulation of phototrophic carbon uptake in the presence of Fe(II, and determined light-dependent Fe(II-oxidation by the natural chemocline microbiota. Moreover, a photoferrotrophic bacterium most closely related to Chlorobium ferrooxidans was enriched from the ferruginous water column. Our study for the first time demonstrates a direct link between anoxygenic photoferrotrophy and the anoxic precipitation of Fe(III-oxides in a ferruginous water column, providing a plausible mechanism for the bacterial origin of BIF’s before the advent of free oxygen.

  11. Immobilization of radionuclides and heavy metals through anaerobic bio-oxidation of Fe(II)

    International Nuclear Information System (INIS)

    Lack, J.G.; Chaudhuri, S.K.; Kelly, S.D.; Kemner, K.M.; O'Connor, S.M.; Coates, J.D.

    2002-01-01

    Adsorption of heavy metals and radionuclides (HMR) onto iron and manganese oxides has long been recognized as an important reaction for the immobilization of these compounds. However, in environments containing elevated concentrations of these HMR the adsorptive capacity of the iron and manganese oxides may well be exceeded, and the HMR can migrate as soluble compounds in aqueous systems. Here we demonstrate the potential of a bioremediative strategy for HMR stabilization in reducing environments based on the recently described anaerobic nitrate-dependent Fe(II) oxidation by Dechlorosoma species. Bio-oxidation of 10 mM Fe(II) and precipitation of Fe(III) oxides by these organisms resulted in rapid adsorption and removal of 55 μM uranium and 81 μM cobalt from solution. The adsorptive capacity of the biogenic Fe(III) oxides was lower than that of abiotically produced Fe(III) oxides (100 μM for both metals), which may have been a result of steric hindrance by the microbial cells on the iron oxide surfaces. The binding capacity of the biogenic oxides for different heavy metals was indirectly correlated to the atomic radius of the bound element. X-ray absorption spectroscopy indicated that the uranium was bound to the biogenically produced Fe(III) oxides as U(VI) and that the U(VI) formed bidentate and tridentate inner-sphere complexes with the Fe(III) oxide surfaces. Dechlorosoma suillum oxidation was specific for Fe(II), and the organism did not enzymatically oxidize U(IV) or Co(II). Small amounts (less than 2.5 μM) of Cr(III) were reoxidized by D. suillum; however, this appeared to be inversely dependent on the initial concentration of the Cr(III). The results of this study demonstrate the potential of this novel approach for stabilization and immobilization of HMR in the environment.

  12. Mn(II) oxidation by an ascomycete fungus is linked to superoxide production during asexual reproduction.

    Science.gov (United States)

    Hansel, Colleen M; Zeiner, Carolyn A; Santelli, Cara M; Webb, Samuel M

    2012-07-31

    Manganese (Mn) oxides are among the most reactive minerals within the environment, where they control the bioavailability of carbon, nutrients, and numerous metals. Although the ability of microorganisms to oxidize Mn(II) to Mn(III/IV) oxides is scattered throughout the bacterial and fungal domains of life, the mechanism and physiological basis for Mn(II) oxidation remains an enigma. Here, we use a combination of compound-specific chemical assays, microspectroscopy, and electron microscopy to show that a common Ascomycete filamentous fungus, Stilbella aciculosa, oxidizes Mn(II) to Mn oxides by producing extracellular superoxide during cell differentiation. The reactive Mn oxide phase birnessite and the reactive oxygen species superoxide and hydrogen peroxide are colocalized at the base of asexual reproductive structures. Mn oxide formation is not observed in the presence of superoxide scavengers (e.g., Cu) and inhibitors of NADPH oxidases (e.g., diphenylene iodonium chloride), enzymes responsible for superoxide production and cell differentiation in fungi. Considering the recent identification of Mn(II) oxidation by NADH oxidase-based superoxide production by a common marine bacterium (Roseobacter sp.), these results introduce a surprising homology between some prokaryotic and eukaryotic organisms in the mechanisms responsible for Mn(II) oxidation, where oxidation appears to be a side reaction of extracellular superoxide production. Given the versatility of superoxide as a redox reactant and the widespread ability of fungi to produce superoxide, this microbial extracellular superoxide production may play a central role in the cycling and bioavailability of metals (e.g., Hg, Fe, Mn) and carbon in natural systems.

  13. Wet Oxidation of Maleic Acid by a Pumice Supported Copper (II ...

    African Journals Online (AJOL)

    Pumice supported Cu (II) Schiff base catalysts were prepared by surface chemical modification followed by complexation with Cu (II) acetate. The resulting materials were characterised by Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS) to confirm the modification. The materials were tested in a wet oxidation ...

  14. Palladium(II)-catalyzed oxidation of L-tryptophan by ...

    Indian Academy of Sciences (India)

    dium(II)] were obtained. The reaction exhibits fractional-second order kinetics with respect to [H ... compounds. Its use- fulness may be due to its unequivocal stability, water. ∗ ... metals are known to catalyze many oxidation–reduction reactions because they ... prepared by dissolving potassium hexacyanoferrate(II). (SD Fine ...

  15. High strength air-dried aerogels

    Science.gov (United States)

    Coronado, Paul R.; Satcher, Jr., Joe H.

    2012-11-06

    A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

  16. Iron(II) porphyrins induced conversion of nitrite into nitric oxide: A computational study.

    Science.gov (United States)

    Zhang, Ting Ting; Liu, Yong Dong; Zhong, Ru Gang

    2015-09-01

    Nitrite reduction to nitric oxide by heme proteins was reported as a protective mechanism to hypoxic injury in mammalian physiology. In this study, the pathways of nitrite reduction to nitric oxide mediated by iron(II) porphyrin (P) complexes, which were generally recognized as models for heme proteins, were investigated by using density functional theory (DFT). In view of two type isomers of combination of nitrite and Fe(II)(P), N-nitro- and O-nitrito-Fe(II)-porphyrin complexes, and two binding sites of proton to the different O atoms of nitrite moiety, four main pathways for the conversion of nitrite into nitric oxide mediated by iron(II) porphyrins were proposed. The results indicate that the pathway of N-bound Fe(II)(P)(NO2) isomer into Fe(III)(P)(NO) and water is similar to that of O-bound isomer into nitric oxide and Fe(III)(P)(OH) in both thermodynamical and dynamical aspects. Based on the initial computational studies of five-coordinate nitrite complexes, the conversion of nitrite into NO mediated by Fe(II)(P)(L) complexes with 14 kinds of proximal ligands was also investigated. Generally, the same conclusion that the pathways of N-bound isomers are similar to those of O-bound isomer was obtained for iron(II) porphyrin with ligands. Different effects of ligands on the reduction reactions were also found. It is notable that the negative proximal ligands can improve reactive abilities of N-nitro-iron(II) porphyrins in the conversion of nitrite into nitric oxide compared to neutral ligands. The findings will be helpful to expand our understanding of the mechanism of nitrite reduction to nitric oxide by iron(II) porphyrins. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Effect of the oxidation rate and Fe(II) state on microbial nitrate-dependent Fe(III) mineral formation

    Science.gov (United States)

    Senko, John M.; Dewers , Thomas A.; Krumholz, Lee R.

    2005-01-01

    A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems.

  18. Surface Mn(II) oxidation actuated by a multicopper oxidase in a soil bacterium leads to the formation of manganese oxide minerals.

    Science.gov (United States)

    Zhang, Zhen; Zhang, Zhongming; Chen, Hong; Liu, Jin; Liu, Chang; Ni, Hong; Zhao, Changsong; Ali, Muhammad; Liu, Fan; Li, Lin

    2015-06-03

    In this manuscript, we report that a bacterial multicopper oxidase (MCO266) catalyzes Mn(II) oxidation on the cell surface, resulting in the surface deposition of Mn(III) and Mn(IV) oxides and the gradual formation of bulky oxide aggregates. These aggregates serve as nucleation centers for the formation of Mn oxide micronodules and Mn-rich sediments. A soil-borne Escherichia coli with high Mn(II)-oxidizing activity formed Mn(III)/Mn(IV) oxide deposit layers and aggregates under laboratory culture conditions. We engineered MCO266 onto the cell surfaces of both an activity-negative recipient and wild-type strains. The results confirmed that MCO266 governs Mn(II) oxidation and initiates the formation of deposits and aggregates. By contrast, a cell-free substrate, heat-killed strains, and intracellularly expressed or purified MCO266 failed to catalyze Mn(II) oxidation. However, purified MCO266 exhibited Mn(II)-oxidizing activity when combined with cell outer membrane component (COMC) fractions in vitro. We demonstrated that Mn(II) oxidation and aggregate formation occurred through an oxygen-dependent biotic transformation process that requires a certain minimum Mn(II) concentration. We propose an approximate electron transfer pathway in which MCO266 transfers only one electron to convert Mn(II) to Mn(III) and then cooperates with other COMC electron transporters to transfer the other electron required to oxidize Mn(III) to Mn(IV).

  19. Aerogel Cerenkov counters at DESY

    International Nuclear Information System (INIS)

    Poelz, G.

    1984-11-01

    In high energy physics it is common to identify a charged particle and its kinematical parameters by the measurement of its momentum and its velocity. Cerenkov detectors have developed into a standard tool because they operate in the γ = (1-β 2 )sup(-1/2) range from about 1 to 100 which is not easily accessible by other devices. Pions, kaons and protons in present high energy experiments reach energies of several GeV. Threshold Cerenkov detectors for these particles need indices of refraction below 1.1 which are often produced with gases under high pressure. The design for chambers operating in this region was drasticly simplified when porous materials serving as Cerenkov radiators were invented. These chambers complement the time-of-flight counters, which cover the low energy region. Aerogel of silica is up to now the only porous substance with sufficient optical transparency. Its quality has been improved substantially in recent times so that large size detectors can be constructed. (orig.)

  20. Effect of Dunaliella tertiolecta organic exudates on the Fe(II) oxidation kinetics in seawater.

    Science.gov (United States)

    González, A G; Santana-Casiano, J M; González-Dávila, M; Pérez-Almeida, N; Suárez de Tangil, M

    2014-07-15

    The role played by the natural organic ligands excreted by the green algae Dunaliella tertiolecta on the Fe(II) oxidation rate constants was studied at different stages of growth. The concentration of dissolved organic carbon increased from 2.1 to 7.1 mg L(-1) over time of culture. The oxidation kinetics of Fe(II) was studied at nanomolar levels and under different physicochemical conditions of pH (7.2-8.2), temperature (5-35 °C), salinity (10-37), and dissolved organic carbon produced by cells (2.1-7.1 mg L(-1)). The experimental rate always decreased in the presence of organic exudates with respect to that in the control seawater. The Fe(II) oxidation rate constant was also studied in the context of Marcus theory, where ΔG° was 39.31-51.48 kJ mol(-1). A kinetic modeling approach was applied for computing the equilibrium and rate constants for Fe(II) and exudates present in solution, the Fe(II) speciation, and the contribution of each Fe(II) species to the overall oxidation rate constant. The best fit model took into account two acidity equilibrium constants for the Fe(II) complexing ligands with pKa,1=9.45 and pKa,2=4.9. The Fe(II) complexing constants were KFe(II)-LH=3×10(10) and KFe(II)-L=10(7), and the corresponding computed oxidation rates were 68±2 and 36±8 M(-1) min(-1), respectively.

  1. Refractive index inhomogeneity within an aerogel block

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Da Silva Costa, C.F.; Matteuzzi, C.; Musy, M.; Perego, D.L.

    2006-01-01

    Evaluating local inhomogeneities of the refractive index inside aerogel blocks to be used as Cherenkov radiator is important for a high energy physics experiment where angular resolution is crucial. Two approaches are described and compared. The first one is based on the bending of a laser beam induced by refractive index gradients along directions normal to the unperturbed optical path. The second method exploits the Cherenkov effect itself by shooting an ultra-relativistic collimated electron beam through different points of the aerogel surface. Local refractive index variations result in sizable differences in the Cherenkov photons distribution

  2. Performance of aerogel as Cherenkov radiator

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Negri, P.; Braem, A.; Chesi, E.; Hansen, C.; Liko, D.; Joram, C.; Neufeld, N.; Seguinot, J.; Weilhammer, P.; Buzykaev, A.R.; Kravchenko, E.A.; Onuchin, A.P.; Danilyuk, A.F.; Easo, S.; Wotton, S.; Jolly, S.

    2004-01-01

    Aerogel with index of refraction around 1.03 has been studied as Cherenkov radiator in a test at CERN PS using a π - and a mixed π + /p beam of momenta between 6 and 10 GeV/c. The Cherenkov photons were detected by means of four large HPD tubes designed and constructed at CERN. Results on the photoelectron yield, the Cherenkov angle and its resolution, and the π/p separation are obtained. The performances measured demonstrate that a RICH with aerogel is a viable detector for experiments with high multiplicity of particles in the final state

  3. Test of aerogel as Cherenkov radiator

    CERN Document Server

    Alemi, M; Calvi, M; Matteuzzi, C; Negri, P; Paganoni, M; Liko, D; Neufeld, N; Chesi, Enrico Guido; Joram, C; Séguinot, Jacques; Ypsilantis, Thomas

    2001-01-01

    Two different stacks of aerogel were tested in a pion/proton beam of momentum between 3 and 10 GeV/c. The optical characteristics of the aerogel samples were different: one sample was hygroscopic while the other was hydrophobic. Two HPD tubes were used as photodetectors, and different thicknesses of the stacks were used, in order to determine the photoelectron yield, the Cherenkov angle and its precision. Pion/proton separation has been demonstrated at momenta up to 10 GeV/c.

  4. Zeolite-encapsulated Co(II), Mn(II), Cu(II) and Cr(III) salen complexes as catalysts for efficient selective oxidation of benzyl alcohol

    Science.gov (United States)

    Li, F. H.; Bi, H.; Huang, D. X.; Zhang, M.; Song, Y. B.

    2018-01-01

    Co(II), Mn(II), Cu(II) and Cr(III) salen type complexes were synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. Data of characterization indicates the formation of metal salen complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activity results show that Cosalcyen Y exhibited higher catalytic activity in the water phase selective oxidation of benzyl alcohol, which could be attributed to their geometry and the steric environment of the metal actives sites.

  5. Protection against inhaled oxidants through scavenging of oxidized lipids by macrophage receptors MARCO and SR-AI/II

    DEFF Research Database (Denmark)

    Dahl, Morten; Bauer, Alison K; Arredouani, Mohamed

    2007-01-01

    Alveolar macrophages (AMs) express the class A scavenger receptors (SRAs) macrophage receptor with collagenous structure (MARCO) and scavenger receptor AI/II (SRA-I/II), which recognize oxidized lipids and provide innate defense against inhaled pathogens and particles. Increased MARCO expression...... in lungs of ozone-resistant mice suggested an additional role protecting against inhaled oxidants. After ozone exposure, MARCO-/- mice showed greater lung injury than did MARCO+/+ mice. Ozone is known to generate oxidized, proinflammatory lipids in lung lining fluid, such as 5beta,6beta......-epoxycholesterol (beta-epoxide) and 1-palmitoyl-2-(9'-oxo-nonanoyl)-glycerophosphocholine (PON-GPC). Intratracheal instillation of either lipid caused substantial neutrophil influx in MARCO-/- mice, but had no effect in MARCO+/+ mice. Normal AMs showed greater uptake in vitro of beta-epoxide compared with MARCO-/- AMs...

  6. An emerging platform for drug delivery: aerogel based systems.

    Science.gov (United States)

    Ulker, Zeynep; Erkey, Can

    2014-03-10

    Over the past few decades, advances in "aerogel science" have provoked an increasing interest for these materials in pharmaceutical sciences for drug delivery applications. Because of their high surface areas, high porosities and open pore structures which can be tuned and controlled by manipulation of synthesis conditions, nanostructured aerogels represent a promising class of materials for delivery of various drugs as well as enzymes and proteins. Along with biocompatible inorganic aerogels and biodegradable organic aerogels, more complex systems such as surface functionalized aerogels, composite aerogels and layered aerogels have also been under development and possess huge potential. Emphasis is given to the details of the aerogel synthesis and drug loading methods as well as the influence of synthesis parameters and loading methods on the adsorption and release of the drugs. Owing to their ability to increase the bioavailability of low solubility drugs, to improve both their stability and their release kinetics, there are an increasing number of research articles concerning aerogels in different drug delivery applications. This review presents an up to date overview of the advances in all kinds of aerogel based drug delivery systems which are currently under investigation. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Rate law of Fe(II) oxidation under low O2 conditions

    Science.gov (United States)

    Kanzaki, Yoshiki; Murakami, Takashi

    2013-12-01

    Despite intensive studies on Fe(II) oxidation kinetics, the oxidation rate law has not been established under low O2 conditions. The importance of Fe(II) oxidation under low O2 conditions has been recently recognized; for instance, the Fe(II)/Fe(III) compositions of paleosols, ancient soils formed by weathering, can produce a quantitative pattern of the atmospheric oxygen increase during the Paleoproterozoic. The effects of partial pressure of atmospheric oxygen (PO2) on the Fe(II) oxidation rate were investigated to establish the Fe(II) oxidation rate - PO2 relationships under low O2 conditions. All oxidation experiments were carried out in a glove box by introducing Ar gas at ∼10-5-∼10-4 atm of PO2, pH 7.57-8.09 and 22 °C. Luminol chemiluminescence was adopted to measure low Fe(II) concentrations (down to ∼2 nM). Combining previous data under higher PO2 conditions (10-3-0.2 atm) with the present data, the rate law for Fe(II) oxidation over a wide range of PO2 (10-5-0.2 atm) was found to be written as: d[Fe(II)]/dt=-k[Fe(II)][[]2 where the exponent of [O2], x, and the rate constant, k, change from x = 0.98 (±0.04) and log k = 15.46 (±0.06) at ∼6 × 10-3-0.2 atm of PO2 to x = 0.58 (±0.02) and log k = 13.41 (±0.03) at 10-5-∼6 × 10-3 atm of PO2. The most plausible mechanism that explains the change in x under low O2 conditions is that, instead of O2, oxygen-derived oxidants, H2O2 and to some extent, O2rad -, dominate the oxidation reactions at PO2. The rate law found in the present study requires us to reconsider distributions of Fe redox species at low PO2 in natural environments, especially in paleoweathering profiles, and may provide a deeper understanding of the evolution of atmospheric oxygen in the Precambrian.

  8. Carbonate-mediated Fe(II) oxidation in the air-cathode fuel cell: a kinetic model in terms of Fe(II) speciation.

    Science.gov (United States)

    Song, Wei; Zhai, Lin-Feng; Cui, Yu-Zhi; Sun, Min; Jiang, Yuan

    2013-06-06

    Due to the high redox activity of Fe(II) and its abundance in natural waters, the electro-oxidation of Fe(II) can be found in many air-cathode fuel cell systems, such as acid mine drainage fuel cells and sediment microbial fuel cells. To deeply understand these iron-related systems, it is essential to elucidate the kinetics and mechanisms involved in the electro-oxidation of Fe(II). This work aims to develop a kinetic model that adequately describes the electro-oxidation process of Fe(II) in air-cathode fuel cells. The speciation of Fe(II) is incorporated into the model, and contributions of individual Fe(II) species to the overall Fe(II) oxidation rate are quantitatively evaluated. The results show that the kinetic model can accurately predict the electro-oxidation rate of Fe(II) in air-cathode fuel cells. FeCO3, Fe(OH)2, and Fe(CO3)2(2-) are the most important species determining the electro-oxidation kinetics of Fe(II). The Fe(II) oxidation rate is primarily controlled by the oxidation of FeCO3 species at low pH, whereas at high pH Fe(OH)2 and Fe(CO3)2(2-) are the dominant species. Solution pH, carbonate concentration, and solution salinity are able to influence the electro-oxidation kinetics of Fe(II) through changing both distribution and kinetic activity of Fe(II) species.

  9. Aerogel as Cherenkov radiator for RICH detectors

    International Nuclear Information System (INIS)

    Bellunato, T.; Braem, A.; Buzykaev, A.R.; Calvi, M.; Chesi, E.; Danilyuk, A.F.; Easo, S.; Hansen, C.; Jolly, S.; Joram, C.; Kravchenko, E.A.; Liko, D.; Matteuzzi, C.; Musy, M.; Negri, P.; Neufeld, N.; Onuchin, A.P.; Seguinot, J.; Weilhammer, P.; Wotton, S.

    2003-01-01

    We present here the results obtained using silica aerogel as Cherenkov radiator for the separation and identification of particles in the momentum range from 6 to 10 GeV/c. Photoelectron yield and Cherenkov ring resolution were studied under different experimental conditions and compared to the simulation

  10. Constraining the role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in deposition of BIFs

    Science.gov (United States)

    Kappler, A.; Posth, N. R.; Hegler, F.; Wartha, E.; Huelin, S.

    2007-12-01

    Banded Iron Formations (BIFs) are Precambrian sedimentary deposits of alternating iron oxide and silica mineral layers. Their presence in the rock record ca.3.8-2.2 Ga makes them particularly intriguing formations for the debate over when oxygen became dominant on Earth. The mechanism(s) of BIF deposition is still unclear; suggestions including both abiotic and biotic processes. We are interested in constraining one of these proposed mechanisms; the direct biological oxidation of Fe(II) via anoxygenic Fe(II)-oxidizing autophototrophs. In order to find the limitations of photoferrotrophic BIF deposition, we take a holistic approach, investigating the oxidation of Fe(II) by modern Fe(II)-oxidizing phototrophs, the precipitation of Fe(III) (hydr)oxides, and the fate of the cell-mineral aggregates in the water column and at the basin floor. Specifically, physiology experiments with Fe(II)-oxidizing phototrophs under various conditions of light intensity, pH, Fe(II) concentration and temperature allow us to determine the environmental limits of such organisms. We carry out precipitation experiments to characterize the sedimentation rates, aggregate size and composition in order to resolve the effect of reactions in the water column. Finally, we simulate the diagenetic fate of these aggregates on the basin floor by placing them in gold capsules under T and P conditions relevant for the Transvaal Supergroup BIFs of South Africa. Recently, we have developed a tank simulating the Archean ocean in which the strains grow in continuous culture and collect the aggregates formed under various geochemical conditions. We aim to model the extent of and limitations to photoferrotrophs in BIF deposition. This information will help constrain whether biotic processes were dominant in the Archean ocean and will offer insight to the evolution of the early biogeosphere.

  11. Faraday rotation measurements in maghemite-silica aerogels

    International Nuclear Information System (INIS)

    Taboada, E.; Real, R.P. del; Gich, M.; Roig, A.; Molins, E.

    2006-01-01

    Faraday rotation measurements have been performed on γ-Fe 2 O 3 /SiO 2 nanocomposite aerogels which are light, porous and transparent magnetic materials. The materials have been prepared by sol-gel polymerization of a silicon alkoxide, impregnation of the intermediate silica gel with a ferrous salt and supercritical drying of the gels. During supercritical evacuation of the solvent, spherical nanoparticles of iron oxide, with a mean particle diameter of 8.1±2.0 nm, are formed and are found to be homogenously distributed within the silica matrix. The specific Faraday rotation of the composite was measured at 0.6 T using polarized light of 810 nm, being 29.6 deg./cm. The changes in the plane of polarization of the transmitted light and the magnetization of the material present similar magnetic field dependencies and are characteristic of a superparamagnetic system

  12. Preparation and characterization of zinc and cobalt (II, III) oxides ...

    Indian Academy of Sciences (India)

    1Laboratório de Processos de Oxidação Avançados, Departamento de Química, Caixa Postal 10011, ... gated through the heterogeneous photocatalysis mediated by zinc oxide, n-type semiconductor .... 3.2 Band gap energy determination.

  13. Kinetic studies of electrochemical generation of Ag(II) ion and catalytic oxidation of selected organics

    International Nuclear Information System (INIS)

    Zawodzinski, C.; Smith, W.H.; Martinez, K.R.

    1993-01-01

    The goal of this research is to develop a method to treat mixed hazardous wastes containing selected organic compounds and heavy metals, including actinide elements. One approach is to destroy the organic via electrochemical oxidation to carbon dioxide, then recover the metal contaminants through normally accepted procedures such as ion exchange, precipitation, etc. The authors have chosen to study the electrochemical oxidation of a simple alcohol, iso-propanol. Much of the recent work reported involved the use of an electron transfer mediator, usually the silver(I)/(II) redox couple. This involved direct electrochemical generation of the mediator at the anode of a divided cell followed by homogeneous reaction of the mediator with the organic compound. In this study the authors have sought to compare the mediated reaction with direct electrochemical oxidation of the organic. In addition to silver(I)/(II) they also looked at the cobalt(II)/(III) redox coupled. In the higher oxidation state both of these metal ions readily hydrolyze in aqueous solution to ultimately form insoluble oxide. The study concluded that in a 6M nitric acid solution at room temperature iso-propanol can be oxidized to carbon dioxide and acetic acid. Acetic acid is a stable intermediate and resists further oxidation. The presence of Co(III) enhances the rate or efficiency of the reaction

  14. Novel bioactive materials: silica aerogel and hybrid silica aerogel/pseudowollastonite

    Directory of Open Access Journals (Sweden)

    Reséndiz-Hernández, P. J.

    2014-10-01

    Full Text Available Silica aerogel and hybrid silica aerogel/pseudowollastonite materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS using also methanol (MeOH and pseudowollastonite particles. The gels obtained were dried using a novel process based on an ambient pressure drying. Hexane and hexamethyl-disilazane (HMDZ were the solvents used to chemically modify the surface. In order to assess bioactivity, aerogels, without and with pseudowollastonite particles, were immersed in simulated body fluid (SBF for 7 and 14 days. The hybrid silica aerogel/pseudowollastonite showed a higher bioactivity than that observed for the single silica aerogel. However, as in both cases a lower bioactivity was observed, a biomimetic method was also used to improve it. In this particular method, samples of both materials were immersed in SBF for 7 days followed by their immersion in a more concentrated solution (1.5 SBF for 14 days. A thick and homogeneous bonelike apatite layer was formed on the biomimetically treated materials. Thus, bioactivity was successfully improved even on the aerogel with no pseudowollastonite particles. As expected, the hybrid silica aerogel/pseudowollastonite particles showed a higher bioactivity.Se sintetizaron aerogel de sílice y aerogel híbrido de sílice/partículas de pseudowollastonita por hidrólisis controlada de tetraetoxisilano (TEOS usando metanol (MeOH y partículas de pseudowollastonita. Los geles obtenidos se secaron utilizando un novedoso proceso basado en una presión de secado ambiental. Hexano y hexametil-disilazano fueron los solventes usados para modificar químicamente la superficie. Para evaluar la bioactividad, los aerogeles con y sin partículas de pseudowollastonita se sumergieron en un fluido fisiológico simulado (SBF por 7 y 14 días. El aerogel híbrido de sílice/partículas de pseudowollastonita mostró más alta bioactividad que la observada por el aerogel solo. Sin embargo, en ambos casos, se

  15. Cu(II)-catalyzed oxidation of dopamine in aqueous solutions: mechanism and kinetics.

    Science.gov (United States)

    Pham, A Ninh; Waite, T David

    2014-08-01

    Spontaneous oxidation of dopamine (DA) and the resultant formation of free radical species within dopamine neurons of the substantia nigra (SN) is thought to bestow a considerable oxidative load upon these neurons and may contribute to their vulnerability to degeneration in Parkinson's disease (PD). An understanding of DA oxidation under physiological conditions is thus critical to understanding the relatively selective vulnerability of these dopaminergic neurons in PD and may support the development of novel neuro-protective approaches for this disorder. In this study, the oxidation of dopamine (0.2-10μM) was investigated both in the absence and the presence of copper (0.01-0.4μM), a redox active metal that is present at considerable concentrations in the SN, over a range of background chloride concentrations (0.01-0.7M), different oxygen concentrations and at physiological pH7.4. DA was observed to oxidize extremely slowly in the absence of copper and at moderate rates only in the presence of copper but without chloride. The oxidation of DA however was significantly enhanced in the presence of both copper and chloride with the rate of DA oxidation greatest at intermediate chloride concentrations (0.05-0.2M). The variability of the catalytic effect of Cu(II) on DA oxidation at different chloride concentrations can be explained and successfully modeled by appropriate consideration of the reaction of Cu(II) species with DA and the conversion of Cu(I) to Cu(II) through oxygenation. This model suggests that the speciation of Cu(II) and Cu(I) is critically important to the kinetics of DA oxidation and thus the vulnerability to degradation of dopaminergic neuron in the brain milieu. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Impact of polishing on the light scattering at aerogel surface

    International Nuclear Information System (INIS)

    Barnyakov, A.Yu.; Barnyakov, M.Yu.; Bobrovnikov, V.S.; Buzykaev, A.R.; Danilyuk, A.F.; Katcin, A.A.; Kononov, S.A.; Kirilenko, P.S.; Kravchenko, E.A.; Kuyanov, I.A.; Onuchin, A.P.; Ovtin, I.V.; Predein, A.Yu.; Protsenko, R.S.

    2016-01-01

    Particle identification power of modern aerogel RICH detectors strongly depends on optical quality of radiators. It was shown that wavelength dependence of aerogel tile transparency after polishing cannot be described by the standard Hunt formula. The Hunt formula has been modified to describe scattering in a thin layer of silica dust on the surface of aerogel tile. Several procedures of polishing of aerogel tile have been tested. The best result has been achieved while using natural silk tissue. The resulting block has optical smooth surfaces. The measured decrease of aerogel transparency due to surface scattering is about few percent. This result could be used for production of radiators for the Focusing Aerogel RICH detectors.

  17. Flexible aerogel composite for mechanical stability and process of fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Coronado, P.R.; Poco, J.F.

    1999-10-26

    A flexible aerogel and process of fabrication are disclosed. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4--5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  18. Flexible aerogel composite for mechanical stability and process of fabrication

    Science.gov (United States)

    Coronado, Paul R.; Poco, John F.

    1999-01-01

    A flexible aerogel and process of fabrication. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4-5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  19. Flexible aerogel composite for mechanical stability and process of fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Coronado, P.R.; Poco, J.F.

    2000-07-11

    A flexible aerogel and process of fabrication are disclosed. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4--5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  20. One-Pot Synthesis of Cu(II Complex with Partially Oxidized TTF Moieties

    Directory of Open Access Journals (Sweden)

    Hiroki Oshio

    2012-07-01

    Full Text Available The one-pot synthesis of a Cu(II complex with partially oxidized tetrathiafulvalene (TTF moieties in its capping MT-Hsae-TTF ligands, [CuII(MT-sae-TTF2] [CuICl2] was realized by the simultaneous occurrence of Cu(II complexation and CuIICl2 mediated oxidation of TTF moieties. The crystal structure was composed of one-dimensional columns formed by partially oxidized TTF moieties and thus the cation radical salt showed relatively high electrical conductivity. Tight binding band structure calculations indicated the existence of a Peierls gap due to the tetramerization of the TTF moieties in the one-dimensional stacking column at room temperature, which is consistent with the semiconducting behavior of this salt.

  1. Angiotensin II stimulates superoxide production by nitric oxide synthase in thick ascending limbs.

    Science.gov (United States)

    Gonzalez-Vicente, Agustin; Saikumar, Jagannath H; Massey, Katherine J; Hong, Nancy J; Dominici, Fernando P; Carretero, Oscar A; Garvin, Jeffrey L

    2016-02-01

    Angiotensin II (Ang II) causes nitric oxide synthase (NOS) to become a source of superoxide (O2 (-)) via a protein kinase C (PKC)-dependent process in endothelial cells. Ang II stimulates both NO and O2 (-) production in thick ascending limbs. We hypothesized that Ang II causes O2 (-) production by NOS in thick ascending limbs via a PKC-dependent mechanism. NO production was measured in isolated rat thick ascending limbs using DAF-FM, whereas O2 (-) was measured in thick ascending limb suspensions using the lucigenin assay. Consistent stimulation of NO was observed with 1 nmol/L Ang II (P thick ascending limbs via a PKC- and NADPH oxidase-dependent process; and (2) the effect of Ang II is not due to limited substrate. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  2. Controlling the oxidation of bis-tridentate cobalt(ii) complexes having bis(2-pyridylalkyl)amines: ligand vs. metal oxidation.

    Science.gov (United States)

    Anjana, S; Donring, S; Sanjib, P; Varghese, B; Murthy, Narasimha N

    2017-08-22

    Two bis-tridentate chelated cobalt(ii) complexes, which differ in the ligand structure by a methylene group, activate molecular oxygen (O 2 ), and give different oxidation products. The O 2 reaction of [Co II (pepma) 2 ] 2+ (1) with unsymmetrical 2-(2-pyridyl)-N-(2-pyridylmethyl)ethanamine (pepma) results in ligand oxidation, to the corresponding Co(ii) imine complex [Co II (pepmi) 2 ] 2+ (2). Contrastingly, the Co(ii) complex [Co II (bpma) 2 ] 2+ (3) of similar symmetrical bis(2-pyridylmethyl)amine (bpma), undergoes metal oxidation, yielding a cobalt(iii) complex, [Co III (bpma) 2 ] 2+ (4). The reversibility of the amine to imine conversion and the stability of the Co(ii) imine complex (2) are investigated. Furthermore, the solution dynamics of Co(ii) complexes are highlighted with the help of paramagnetic 1 H-NMR spectroscopy.

  3. Oxidation of manganese(II) with ferrate: Stoichiometry, kinetics, products and impact of organic carbon.

    Science.gov (United States)

    Goodwill, Joseph E; Mai, Xuyen; Jiang, Yanjun; Reckhow, David A; Tobiason, John E

    2016-09-01

    Manganese is a contaminant of concern for many drinking water utilities, and future regulation may be pending. An analysis of soluble manganese (Mn(II)) oxidation by ferrate (Fe(VI)) was executed at the bench-scale, in a laboratory matrix, both with and without the presence of natural organic matter (NOM) and at two different pH values, 6.2 and 7.5. In the matrix without NOM, the oxidation of Mn(II) by Fe(VI) followed a stoichiometry of 2 mol Fe(VI) to 3 mol Mn(II). The presence of NOM did not significantly affect the stoichiometry of the oxidation reaction, indicating relative selectivity of Fe(VI) for Mn(II). The size distribution of resulting particles included significant amounts of nanoparticles. Resulting manganese oxide particles were confirmed to be MnO2 via X-ray photoelectron spectroscopy. The rate of the Mn(II) oxidation reaction was fast relative to typical time scales in drinking water treatment, with an estimated second order rate constant of approximately 1 × 10(4) M(-1) s(-1) at pH 9.2 and > 9 × 10(4) M(-1) s(-1) at pH 6.2. In general, ferrate is a potential option for Mn(II) oxidation in water treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Supercritical water oxidation data acquisition testing. Final report, Volume II

    International Nuclear Information System (INIS)

    1996-11-01

    Supercritical Water Oxidation (SCWO) technology holds great promise for treating mixed wastes, in an environmentally safe and efficient manner. In the spring of 1994 the US Department of Energy (DOE), Idaho Operations Office awarded Stone ampersand Webster Engineering Corporation, of Boston Massachusetts and its sub-contractor MODAR, Inc. of Natick Massachusetts a Supercritical Water Oxidation Data Acquisition Testing (SCWODAT) program. The SCWODAT program was contracted through a Cooperative Agreement that was co-funded by the US Department of Energy and the Strategic Environmental Research and Development Program. The SCWODAT testing scope outlined by the DOE in the original Cooperative Agreement and amendments thereto was initiated in June 1994 and successfully completed in December 1995. The SCWODAT program provided further information and operational data on the effectiveness of treating both simulated mixed waste and typical Navy hazardous waste using the MODAR SCWO technology

  5. Bluedec in product design: Isolatiemateriaal op basis van aerogel

    OpenAIRE

    Beurden, van, K.M.M. (Karin); Goselink, E.A. (Erik)

    2014-01-01

    Aerogel is een zeer kostbaar voor de ruimtevaart ontwikkeld basismateriaal. Bluedec is een isolatiemateriaal bestaande uit een non woven kunststof dat met deze aerogel geïmpregneerd is. Hierdoor ontstaat een zeer goed isolerend materiaal dat goedkoper is dan aerogel. De warmtegeleidingscoëfficiënt van Bluedec in de basisuitvoering is 0,0135 W/m*K . Dat is lager dan conventionele isolatiematerialen, zie ook pagina 4. Voordeel hiervan is dat vergelijkbare of betere warmte-isolati...

  6. Synthesis of aerogel tiles with high light scattering length

    CERN Document Server

    Danilyuk, A F; Okunev, A G; Onuchin, A P; Shaurman, S A

    1999-01-01

    The possibility of aerogel tiles production for RICH detectors is described. Monolithic blocks of silica aerogel were synthesized by two-step sol-gel processing of tetraethoxysilane Si(OEt) sub 4 followed by high temperature supercritical drying with organic solvent. The important characteristic of aerogel is the light scattering length. In the wide range of refraction indexes the light scattering length exceeds 4 cm at 400 nm.

  7. Ni(OH)2 Aerogels Incorporated with Polypyrrole as Electrodes for Supercapacitors

    Science.gov (United States)

    Scarabelot, Letícia T.; Muller, Daliana; de Souza, Luciana V.; Hotza, Dachamir; Rambo, Carlos R.

    2017-08-01

    This work reports the synthesis of Ni(OH)2 aerogels incorporated in situ with polypyrrole (PPy) for application as electrodes in high-capacity energy storage devices. Ni(OH)2 gels were prepared by the sol-gel method from NiCl2 as precursor and propylene oxide as gelling agent in ethanol. Pyrrole monomer was added prior to gelling of the sol and in situ polymerized using ammonium persulfate as oxidant agent. After solvent exchanges from ethanol to acetone, the gels were dried in a CO2 supercritical point drier. Powdered aerogels were deposited onto both sides of a poly(vinyl alcohol)/H3PO4 film (electrolyte/separator) and the contacts were closed with copper foils, resulting in a complete device. Through cyclic voltammetry and charge/discharge curves, the performance of the supercapacitors was evaluated by the specific capacitance, power and energy densities and series resistance. The specific capacitance was increased by 43% with the incorporation of 0.2 mol/L PPy (276 F/g) and the series resistance obtained decreased by 79% (46.5 Ω/cm2), which reflects the enhanced performance and electrochemical properties of Ni(OH)2 aerogel- based devices incorporated with PPy.

  8. Pd nanoparticles supported on three-dimensional graphene aerogels as highly efficient catalysts for methanol electrooxidation

    International Nuclear Information System (INIS)

    Liu, Mingrui; Peng, Cheng; Yang, Wenke; Guo, Jiaojiao; Zheng, Yixiong; Chen, Peiqin; Huang, Tingting; Xu, Jing

    2015-01-01

    Well-dispersed Pd nanoparticles supported on three-dimensional graphene aerogels (Pd/3DGA) were successfully prepared via a facile and efficient hydrothermal method without surfactant and template. The morphology and structure of the as-prepared Pd/3DGA nanocomposites were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM showed that the Pd nanoparticles with a small average diameter and narrow size distribution were uniformly deposited on the surface of the self-assembled three-dimensional graphene aerogels. Raman spectra revealed the surface properties of 3DGA and its interaction with metallic nanoparticles. Cyclic voltammetric (CV) and chronoamperometric (CA) experiments further exhibited its superior catalytic activity and stability for the electro-oxidation of methanol in alkaline media, making it a promising anodic catalyst for direct alkaline alcohol fuel cells (DAAFCs).

  9. Nitrogen-doped carbon aerogels for electrical energy storage

    Science.gov (United States)

    Campbell, Patrick; Montalvo, Elizabeth; Baumann, Theodore F.; Biener, Juergen; Merrill, Matthew; Reed, Eric W.; Worsley, Marcus A.

    2017-10-03

    Disclosed here is a method for making a nitrogen-doped carbon aerogel, comprising: preparing a reaction mixture comprising formaldehyde, at least one nitrogen-containing resorcinol analog, at least one catalyst, and at least one solvent; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel; and thermally annealing the dry gel to produce the nitrogen-doped carbon aerogel. Also disclosed is a nitrogen-doped carbon aerogel obtained according to the method and a supercapacitor comprising the nitrogen-doped carbon aerogel.

  10. Carbon Papers and Aerogels Based on Graphene Layers and Chitosan: Direct Preparation from High Surface Area Graphite.

    Science.gov (United States)

    Barbera, Vincenzina; Guerra, Silvia; Brambilla, Luigi; Maggio, Mario; Serafini, Andrea; Conzatti, Lucia; Vitale, Alessandra; Galimberti, Maurizio

    2017-12-11

    In this work, carbon papers and aerogels based on graphene layers and chitosan were prepared. They were obtained by mixing chitosan (CS) and a high surface area nanosized graphite (HSAG) in water in the presence of acetic acid. HSAG/CS water dispersions were stable for months. High resolution transmission electron microscopy revealed the presence of few graphene layers in water suspensions. Casting or lyophilization of such suspensions led to the preparation of carbon paper and aerogel, respectively. In X-ray spectra of both aerogels and carbon paper, peaks due to regular stacks of graphene layers were not detected: graphene with unaltered sp 2 structure was obtained directly from graphite without the use of any chemical reaction. The composites were demonstrated to be electrically conductive thanks to the graphene. Chitosan thus makes it possible to obtain monolithic carbon aerogels and flexible and free-standing graphene papers directly from a nanosized graphite by avoiding oxidation to graphite oxide and successive reduction. Strong interaction between polycationic chitosan and the aromatic substrate appears to be at the origin of the stability of HSAG/CS adducts. Cation-π interaction is hypothesized, also on the basis of X-ray photoelectron spectroscopy findings. This work paves the way for the easy large-scale preparation of carbon papers through a method that has a low environmental impact and is based on a biosourced polymer, graphene, and water.

  11. Modeling of Cd(II) sorption on mixed oxide

    International Nuclear Information System (INIS)

    Waseem, M.; Mustafa, S.; Naeem, A.; Shah, K.H.; Hussain, S.Y.; Safdar, M.

    2011-01-01

    Mixed oxide of iron and silicon (0.75 M Fe(OH)3:0.25 M SiO/sub 2/) was synthesized and characterized by various techniques like surface area analysis, point of zero charge (PZC), energy dispersive X-rays (EDX) spectroscopy, Thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR) and X-rays diffraction (XRD) analysis. The uptake of Cd/sup 2+/ ions on mixed oxide increased with pH, temperature and metal ion concentration. Sorption data have been interpreted in terms of both Langmuir and Freundlich models. The Xm values at pH 7 are found to be almost twice as compared to pH 5. The values of both DH and DS were found to be positive indicating that the sorption process was endothermic and accompanied by the dehydration of Cd/sup 2+/. Further, the negative value of DG confirms the spontaneity of the reaction. The ion exchange mechanism was suggested to take place for each Cd/sup 2+/ ions at pH 5, whereas ion exchange was found coupled with non specific adsorption of metal cations at pH 7. (author)

  12. Mycogenic Mn(II) oxidation promotes remediation of acid mine drainage and other anthropogenically impacted environments

    Science.gov (United States)

    Santelli, C. M.; Chaput, D.; Hansel, C. M.; Burgos, W. D.

    2014-12-01

    Manganese is a pollutant in worldwide environments contaminated with metals and organics, such as acid mine drainage (AMD), freshwater ponds, and agricultural waste storage sites. Microorganisms contribute to the removal of dissolved Mn compounds in the environment by promoting Mn(II) oxidation reactions. The oxidation of Mn(II) results in the precipitation of sparingly soluble Mn(IV) oxide minerals, effectively removing the metal from the aqueous milieu (e.g., groundwater or wastewater streams). In recent years, our research has identified a diversity of Mn(II)-oxidizing fungi inhabiting these polluted environments, however their overall contribution to the remediation process in situ remains poorly understood. Here we present results of culture-based and Next Generation Sequencing (NGS) studies in AMD treatment systems actively remediating Mn and other metals where we profile the bacterial, fungal, algal and archaeal communities to determine the overall community diversity and to establish the relative abundance of known Mn(II) oxidizers. A variety of treatment systems with varying Mn-removal efficiencies were sampled to understand the relationship between remediation efficiency and microbial community composition and activity. Targeted-amplicon sequencing of DNA and RNA of the 16S rRNA genes (bacteria and archaea), 23S rRNA genes (algae) and ITS region (fungi) was performed using both 454 pyrosequencing and Illumina platforms. Results showed that only the fungal taxonomic profiles significantly differed between sites that removed the majority of influent Mn and those that did not. Specifically, Ascomycota (which include known Mn(II) oxidizers isolated from these treatment systems) dominated greater efficiency systems whereas less efficient systems were dominated by Basidiomycota. Furthermore, known Mn(II) oxidizers accounted for only a minor proportion of bacterial sequences but a far greater proportion of fungal sequences. These culture-independent studies lend

  13. Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

    Science.gov (United States)

    Klueglein, Nicole; Zeitvogel, Fabian; Stierhof, York-Dieter; Floetenmeyer, Matthias; Konhauser, Kurt O.; Obst, Martin

    2014-01-01

    Microorganisms have been observed to oxidize Fe(II) at neutral pH under anoxic and microoxic conditions. While most of the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria become encrusted with Fe(III)-rich minerals, photoautotrophic and microaerophilic Fe(II) oxidizers avoid cell encrustation. The Fe(II) oxidation mechanisms and the reasons for encrustation remain largely unresolved. Here we used cultivation-based methods and electron microscopy to compare two previously described nitrate-reducing Fe(II) oxidizers ( Acidovorax sp. strain BoFeN1 and Pseudogulbenkiania sp. strain 2002) and two heterotrophic nitrate reducers (Paracoccus denitrificans ATCC 19367 and P. denitrificans Pd 1222). All four strains oxidized ∼8 mM Fe(II) within 5 days in the presence of 5 mM acetate and accumulated nitrite (maximum concentrations of 0.8 to 1.0 mM) in the culture media. Iron(III) minerals, mainly goethite, formed and precipitated extracellularly in close proximity to the cell surface. Interestingly, mineral formation was also observed within the periplasm and cytoplasm; intracellular mineralization is expected to be physiologically disadvantageous, yet acetate consumption continued to be observed even at an advanced stage of Fe(II) oxidation. Extracellular polymeric substances (EPS) were detected by lectin staining with fluorescence microscopy, particularly in the presence of Fe(II), suggesting that EPS production is a response to Fe(II) toxicity or a strategy to decrease encrustation. Based on the data presented here, we propose a nitrite-driven, indirect mechanism of cell encrustation whereby nitrite forms during heterotrophic denitrification and abiotically oxidizes Fe(II). This work adds to the known assemblage of Fe(II)-oxidizing bacteria in nature and complicates our ability to delineate microbial Fe(II) oxidation in ancient microbes preserved as fossils in the geological record. PMID:24271182

  14. Cobalamin Protection against Oxidative Stress in the Acidophilic Iron-oxidizing Bacterium Leptospirillum group II CF-1

    Directory of Open Access Journals (Sweden)

    Gloria Paz Levicán

    2016-05-01

    Full Text Available Members of the genus Leptospirillum are aerobic iron-oxidizing bacteria belonging to the phylum Nitrospira. They are important members of microbial communities that catalyze the biomining of sulfidic ores, thereby solubilizing metal ions. These microorganisms live under extremely acidic and metal-loaded environments and thus must tolerate high concentrations of reactive oxygen species. Cobalamin (vitamin B12 is a cobalt-containing tetrapyrrole cofactor involved in intramolecular rearrangement reactions and has recently been suggested to be an intracellular antioxidant. In this work, we investigated the effect of the exogenous addition of cobalamin on oxidative stress parameters in Leptospirillum group II strain CF-1. Our results revealed that the external supplementation of cobalamin reduces the levels of intracellular reactive oxygen species and the damage to biomolecules, and also stimulates the growth and survival of cells exposed to oxidative stress exerted by ferric ion, hydrogen peroxide, chromate and diamide. Furthermore, exposure of strain CF-1 to oxidative stress elicitors resulted in the transcriptional activation of the cbiA gene encoding CbiA of the cobalamin biosynthetic pathway. Altogether, these data suggest that cobalamin plays an important role in redox protection of Leptospirillum strain CF-1, supporting survival of this microorganism under extremely oxidative environmental conditions. Understanding the mechanisms underlying the protective effect of cobalamin against oxidative stress may help to develop strategies to make biomining processes more effective.

  15. Aerogel-Based Multilayer Insulation with Micrometeoroid Protection

    Science.gov (United States)

    Begag, Redouane; White, Shannon

    2013-01-01

    Ultra-low-density, highly hydrophobic, fiber-reinforced aerogel material integrated with MLI (aluminized Mylar reflectors and B4A Dacron separators) offers a highly effective insulation package by providing unsurpassed thermal performance and significant robustness, delivering substantial MMOD protection via the addition of a novel, durable, external aerogel layer. The hydrophobic nature of the aerogel is an important property for maintaining thermal performance if the material is exposed to the environment (i.e. rain, snow, etc.) during ground installations. The hybrid aerogel/MLI/MMOD solution affords an attractive alternative because it will perform thermally in the same range as MLI at all vacuum levels (including high vacuum), and offers significant protection from micrometeoroid damage. During this effort, the required low-density and resilient aerogel materials have been developed that are needed to optimize the thermal performance for space (high vacuum) cryotank applications. The proposed insulation/MMOD package is composed of two sections: a stack of interleaved aerogel layers and MLI intended for cryotank thermal insulation, and a 1.5- to 1-in. (.2.5- to 3.8- cm) thick aerogel layer (on top of the insulation portion) for MMOD protection. Learning that low-density aerogel cannot withstand the hypervelocity impact test conditions, the innovators decided during the course of the program to fabricate a high-density and strong material based on a cross-linked aerogel (X-aerogel; developed elsewhere by the innovators) for MMOD protection. This system has shown a very high compressive strength that is capable of withstanding high-impact tests if a proper configuration of the MMOD aerogel layer is used. It was learned that by stacking two X-aerogel layers [1.5-in. (.3.8-cm) thick] separated by an air gap, the system would be able to hold the threat at a speed of 5 km/s and gpass h the test. The first aerogel panel stopped the projectile from damaging the second

  16. Novel and facile method, dynamic self-assemble, to prepare SnO₂/rGO droplet aerogel with complex morphologies and their application in supercapacitors.

    Science.gov (United States)

    Chen, Mingxi; Wang, Huan; Li, Lingzhi; Zhang, Zhe; Wang, Cong; Liu, Yu; Wang, Wei; Gao, Jianping

    2014-08-27

    A facile and novel method to prepare SnO2/reduced graphene oxide (rGO) droplet aerogels with complex morphologies had been developed. This method has been named dynamic self-assemble. Aerogels with both "egg-tart" and "mushroom" shapes were obtained by this method. The changes in the graphene oxide (GO) droplet morphologies during the dynamic process of a GO droplet falling into a SnCl2 target solution were monitored using a high speed camera. The formed SnO2/rGO aerogels were then characterized by Raman spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The microstructures of the SnO2/rGO aerogels were observed with scanning electron microscopy and transmission electron microscopy. Finally, the SnO2/rGO droplet aerogels were used as the electrode material in a symmetrical two-electrode supercapacitor and the electrochemical performance of the supercapacitor was investigated using cyclic voltammetry and galvanostatic charge/discharge methods. The SnO2/rGO electrodes demonstrated excellent electrochemical performance and stability. At a scan rate of 5 mV/s, their highest gravimetric and volumetric specific capacitances were 310 F/g and 180 F/cm(3), respectively, and their energy and power densities were as high as 30 Wh·kg(-1) and 8.3 kW·kg(-1), respectively.

  17. Copper(II)–imida‐salen Complexes Encapsulated into NaY Zeolite for Oxidations Reactions

    DEFF Research Database (Denmark)

    Kuźniarska‐Biernacka, Iwona; Carvalho, M. Alice; Rasmussen, Søren Birk

    2013-01-01

    The oxidation of phenol, cychohexanol and hydroquinone has been screened in the presence of copper(II) complexes with the Schiff‐base salen ligand, 1,5‐bis[(E)‐5‐chloro‐2‐hydroxybenzylideneamino]‐1H‐imidazole‐4‐carbonitrile, and encapsulated into NaY zeolite by using two different methods. The new...

  18. Integrated iron(II) oxidation and limestone neutralisation of acid mine water

    CSIR Research Space (South Africa)

    Maree, JP

    1999-01-01

    Full Text Available dependent on the surface area exposed to the liquid (RSA) and the OH-, oxygen, CaCO3, suspended solids and iron (II) concentrations, and less dependent on specific surface area (SSA) and pressure in the pH range 5 to 6, The chemical oxidation rate (p...

  19. Fe(II) oxidation kinetics and Fe hydroxyphosphate precipitation upon aeration of anaerobic (ground)water

    NARCIS (Netherlands)

    van der Grift, B.; Griffioen, J.; Behrends, T.; Wassen, M.J.; Schot, P.P.; Osté, Leonard

    2015-01-01

    Exfiltration of anaerobic Fe-rich groundwater into surface water plays an important role in controlling the transport of phosphate (P) from agricultural areas to the sea. Previous laboratory and field studies showed that Fe(II) oxidation upon aeration leads to effective immobilization of dissolved P

  20. Study of the emission oxidative reactions of ruthenium (II) complex by cationic compounds in anionic micelles

    International Nuclear Information System (INIS)

    Bonilha, J.B.S.

    1985-01-01

    The oxidative quenching of the emission of the tetraanionic complex tris (4,4' dicarboxylate - 2,2' - bipyridine ruthenium (II) in aqueous solution, by both organic and inorganic compounds in presence of anionic detergents, above and below the critical micelle concentration is studied. The organic cations, the inorganic ion and detergents used are shown. (M.J.C.) [pt

  1. Preparation of silica aerogel for Cerenkov counters

    International Nuclear Information System (INIS)

    Poelz, G.; Riethmueller, R.

    1981-09-01

    Aerogel of silica was produced with an index of refraction of n = 1.024 to equip the TASSO Cerenkov detector with 1700 litres of this radiator medium. In the production process, which is described in detail, different parameters were varied to determine their influence on the shape and the optical quality of the aerogel samples. With the present equipment samples with a size of 17 x 17 x 2.3 cm 3 were manufactured at a rate of 144 pieces per week. A production efficiency of about 90% was obtained. The index of refraction for all samples around n = 1.024 is distributed with sigmasub(n) = 1.3 x 10 -3 . They have an optical transmission length of Λ = 2.64 cm at a wavelength lambda = 438 nm with sigmasub(Λ) = 0.22 cm. For samples with n = 1.017, Λ is found to be about 30% higher. (orig.) [de

  2. Bioinspired Synthesis of Monolithic and Layered Aerogels.

    Science.gov (United States)

    Han, Xiao; Hassan, Khalil T; Harvey, Alan; Kulijer, Dejan; Oila, Adrian; Hunt, Michael R C; Šiller, Lidija

    2018-04-25

    Aerogels are the least dense and most porous materials known to man, with potential applications from lightweight superinsulators to smart energy materials. To date their use has been seriously hampered by their synthesis methods, which are laborious and expensive. Taking inspiration from the life cycle of the damselfly, a novel ambient pressure-drying approach is demonstrated in which instead of employing low-surface-tension organic solvents to prevent pore collapse during drying, sodium bicarbonate solution is used to generate pore-supporting carbon dioxide in situ, significantly reducing energy, time, and cost in aerogel production. The generic applicability of this readily scalable new approach is demonstrated through the production of granules, monoliths, and layered solids with a number of precursor materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Mn(II) oxidation in Fenton and Fenton type systems : Identification of Reaction Efficiency and Reaction Products

    NARCIS (Netherlands)

    van Genuchten, C.M.; Peña, Jasquelin

    2017-01-01

    Efficient and low-cost methods of removing aqueous Mn(II) are required to improve the quality of impacted groundwater supplies. In this work, we show that Fe(0) electrocoagulation (EC) permits the oxidative removal of Mn(II) from solution by reaction with the reactive oxidant species produced

  4. Particle identification system based on dense aerogel

    Energy Technology Data Exchange (ETDEWEB)

    Barnyakov, A.Yu. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Barnyakov, M.Yu. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, 20, Karl Marx prospect, Novosibirsk, 630092 (Russian Federation); Beloborodov, K.I., E-mail: K.I.Beloborodov@inp.nsk.su [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2, Pirogova Street, Novosibirsk 630090 (Russian Federation); Bobrovnikov, V.S.; Buzykaev, A.R. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Danilyuk, A.F. [Boreskov Institute of Catalysis, 5, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Golubev, V.B. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2, Pirogova Street, Novosibirsk 630090 (Russian Federation); Gulevich, V.V. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Kononov, S.A.; Kravchenko, E.A. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2, Pirogova Street, Novosibirsk 630090 (Russian Federation); Onuchin, A.P.; Martin, K.A. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, 20, Karl Marx prospect, Novosibirsk, 630092 (Russian Federation); Serednyakov, S.I. [Budker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2, Pirogova Street, Novosibirsk 630090 (Russian Federation); and others

    2013-12-21

    A threshold Cherenkov counter based on dense aerogel with refraction index n=1.13 is described. This counter is used for kaon identification at momenta below 1 GeV/c in the SND detector, which takes data at the VEPP-2000 e{sup +}e{sup −} collider. The results of measurements of the counter efficiency using electrons, muons, pions, and kaons produced in e{sup +}e{sup −} annihilation are presented.

  5. Modeling Degradation in Solid Oxide Electrolysis Cells - Volume II

    Energy Technology Data Exchange (ETDEWEB)

    Manohar Motwani

    2011-09-01

    Idaho National Laboratory has an ongoing project to generate hydrogen from steam using solid oxide electrolysis cells (SOECs). To accomplish this, technical and degradation issues associated with the SOECs will need to be addressed. This report covers various approaches being pursued to model degradation issues in SOECs. An electrochemical model for degradation of SOECs is presented. The model is based on concepts in local thermodynamic equilibrium in systems otherwise in global thermodynamic non-equilibrium. It is shown that electronic conduction through the electrolyte, however small, must be taken into account for determining local oxygen chemical potential,, within the electrolyte. The within the electrolyte may lie out of bounds in relation to values at the electrodes in the electrolyzer mode. Under certain conditions, high pressures can develop in the electrolyte just near the oxygen electrode/electrolyte interface, leading to oxygen electrode delamination. These predictions are in accordance with the reported literature on the subject. Development of high pressures may be avoided by introducing some electronic conduction in the electrolyte. By combining equilibrium thermodynamics, non-equilibrium (diffusion) modeling, and first-principles, atomic scale calculations were performed to understand the degradation mechanisms and provide practical recommendations on how to inhibit and/or completely mitigate them.

  6. Aerogel and xerogel composites for use as carbon anodes

    Science.gov (United States)

    Cooper, John F [Oakland, CA; Tillotson, Thomas M [Tracy, CA; Hrubesh, Lawrence W [Pleasanton, CA

    2008-08-12

    Disclosed herein are aerogel and xerogel composite materials suitable for use as anodes in fuel cells and batteries. Precursors to the aerogel and xerogel compounds are infused with inorganic polymeric materials or carbon particles and then gelled. The gels are then pyrolyzed to form composites with internal structural support.

  7. The RICH with Aerogel for the LHCb Experiment

    CERN Document Server

    Bellunato, T; Matteuzzi, C; Musy, M; Negri, P; Perego, D L

    2006-01-01

    We report on the status of the art of the aerogel project for LHCb, from the production, in terms of specifications and achieved quality, to the optical and beam tests performed to qualify the material as a Cherenkov radiator. A brief summary of the ageing and radiation tolerance tests performed on some aerogel tiles is also given.

  8. The RICH with Aerogel for the LHCb Experiment

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Negri, P.; Perego, D.L.

    2006-01-01

    We report on the status of the art of the aerogel project for LHCb, from the production, in terms of specifications and achieved quality, to the optical and beam tests performed to qualify the material as a Cherenkov radiator. A brief summary of the ageing and radiation tolerance tests performed on some aerogel tiles is also given

  9. Chemical modification of graphene aerogels for electrochemical capacitor applications.

    Science.gov (United States)

    Hong, Jin-Yong; Wie, Jeong Jae; Xu, Yu; Park, Ho Seok

    2015-12-14

    Graphene aerogel is a relatively new type of aerogel that is ideal for energy storage applications because of its large surface area, high electrical conductivity and good chemical stability. Also, three dimensional interconnected macropores offer many advantages such as low density, fast ion and mass transfer, and easy access to storage sites. Such features allow graphene aerogels to be intensively applied for electrochemical capacitor applications. Despite the growing interest in graphene aerogel-based electrochemical capacitors, however, the graphene aerogels still suffer from their low capacitive performances and high fragility. Both relatively low capacitance and brittleness of physically crosslinked graphene aerogels remain a critical challenge. Until now, a number of alternative attempts have been devoted to overcome these shortcomings. In this perspective, we summarize the recent research progress towards the development of advanced graphene aerogel-based electrochemical capacitors according to the different approaches (e.g. porosity, composition and structure controls). Then, the recently proposed chemical strategies to improve the capacitive performances and mechanical durability of graphene aerogels for practical applications are highlighted. Finally, the current challenges and perspectives in this emerging material are also discussed.

  10. Boosting Bifunctional Oxygen Electrocatalysis with 3D Graphene Aerogel-Supported Ni/MnO Particles.

    Science.gov (United States)

    Fu, Gengtao; Yan, Xiaoxiao; Chen, Yifan; Xu, Lin; Sun, Dongmei; Lee, Jong-Min; Tang, Yawen

    2018-02-01

    Electrocatalysts for oxygen-reduction and oxygen-evolution reactions (ORR and OER) are crucial for metal-air batteries, where more costly Pt- and Ir/Ru-based materials are the benchmark catalysts for ORR and OER, respectively. Herein, for the first time Ni is combined with MnO species, and a 3D porous graphene aerogel-supported Ni/MnO (Ni-MnO/rGO aerogel) bifunctional catalyst is prepared via a facile and scalable hydrogel route. The synthetic strategy depends on the formation of a graphene oxide (GO) crosslinked poly(vinyl alcohol) hydrogel that allows for the efficient capture of highly active Ni/MnO particles after pyrolysis. Remarkably, the resulting Ni-MnO/rGO aerogels exhibit superior bifunctional catalytic performance for both ORR and OER in an alkaline electrolyte, which can compete with the previously reported bifunctional electrocatalysts. The MnO mainly contributes to the high activity for the ORR, while metallic Ni is responsible for the excellent OER activity. Moreover, such bifunctional catalyst can endow the homemade Zn-air battery with better power density, specific capacity, and cycling stability than mixed Pt/C + RuO 2 catalysts, demonstrating its potential feasibility in practical application of rechargeable metal-air batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Novel sound phenomena in superfluid helium in aerogel and other impure superfluids

    International Nuclear Information System (INIS)

    Brusov, Peter; Brusov, Paul; Lawes, Gavin; Lee, Chong; Matsubara, Akira; Ishikawa, Osamu; Majumdar, Pinaki

    2003-01-01

    During the last decade new techniques for producing impure superfluids with unique properties have been developed. This new class of systems includes superfluid helium confined to aerogel, HeII with different impurities (D 2 , N 2 , Ne, Kr), superfluids in Vycor glasses, and watergel. These systems exhibit very unusual properties including unexpected acoustic features. We discuss the sound properties of these systems and show that sound phenomena in impure superfluids are modified from those in pure superfluids. We calculate the coupling between temperature and pressure oscillations for impure superfluids and for superfluid He in aerogel. We show that the coupling between these two sound modes is governed either by c∂ρ/∂c or σρ a ρ s (for aerogel) rather than thermal expansion coefficient ∂ρ/∂T, which is enormously small in pure superfluids. This replacement plays a fundamental role in all sound phenomena in impure superfluids. It enhances the coupling between the two sound modes that leads to the existence of such phenomena as the slow mode and heat pulse propagation with the velocity of first sound observed in superfluids in aerogel. This means that it is possible to observe in impure superfluids such unusual sound phenomena as slow pressure (density) waves and fast temperature (entropy) waves. The enhancement of the coupling between the two sound modes decreases the threshold values for nonlinear processes as compared to pure superfluids. Sound conversion, which has been observed in pure superfluids only by shock waves should be observed at moderate sound amplitude in impure superfluids. Cerenkov emission of second sound by first sound (which never been observed in pure superfluids) could be observed in impure superfluids

  12. Quantitative analysis of silica aerogel-based thermal insulation coatings

    DEFF Research Database (Denmark)

    Kiil, Søren

    2015-01-01

    containing intact hollow glass or polymer spheres showed that silica aerogel particles are more efficient in an insulation coating than hollow spheres. In a practical (non-ideal) comparison, the ranking most likely cannot be generalized. A parameter study demonstrates how the model can be used, qualitatively......A mathematical heat transfer model for a silica aerogel-based thermal insulation coating was developed. The model can estimate the thermal conductivity of a two-component (binder-aerogel) coating with potential binder intrusion into the nano-porous aerogel structure. The latter is modelled using...... a so-called core–shell structure representation. Data from several previous experimental investigations with silica aerogels in various binder matrices were used for model validation. For some relevant cases with binder intrusion, it was possible to obtain a very good agreement between simulations...

  13. Monolithic silica aerogel - material design on the nano-scale

    DEFF Research Database (Denmark)

    Jensen, Karsten Ingerslev; Schultz, Jørgen Munthe; Kristiansen, Finn Harken

    structure of aerogel could be used for gas filters in the 20 to 100 nm region. - The sound velocity within aerogel is in the range of 100 to 300 m/s, which should be one of lowest for an inorganic material. Due to the low density, low acoustic impedance of aerogel could help boost the efficiency...... of piezoelectric transducers. - Other applications could be; waste encapsulation, spacers for vacuum insulation panels, membranes, etc. Department of Civil Engineering is co-ordinator of a current EU FP5 research project1, which deals with the application of aerogel as transparent insulation materials in windows....... Due to the excellent optical and thermal properties of aerogel, it is possible to develop windows with both high insulation and high transmittance, which is impossible applying the conventional window techniques, i.e. extra layers of glass, low-e coatings and gas fillings. It can be shown...

  14. A three-dimensional BiOBr/RGO heterostructural aerogel with enhanced and selective photocatalytic properties under visible light

    International Nuclear Information System (INIS)

    Yu, Xue; Shi, Junjie; Feng, Lijuan; Li, Chunhu; Wang, Liang

    2017-01-01

    Highlights: • A BiOBr/RGO aerogel photocatalyst was synthesized using dopamine as reducing agent. • BiOBr/RGO aerogel can be easily controlled morphology by a simple two-step method. • BiOBr/RGO aerogel photocatalyst exhibited superior performance in MO decoloration. - Abstract: A series of BiOBr/reduced graphene oxide (RGO) aerogel was fabricated using a two steps hydrothermal method. Various methods such as SEM, TEM, DRS and Raman spectroscopy were employed to fully characterize the as-obtained BiOBr/RGO. Their photocatalytic degradation of methyl orange (MO) were studied under visible light irradiation. The combination of BiOBr and RGO result in an improved activity. The sample with 10 wt% RGO abbreviated as BiOBr-G10 shows the highest activity. Moreover, this sample exhibits a selective visible-light photocatalytic behavior as the degradation rate over MO (80%) is much higher than that over Rhodamin B (50%) and phenol (35%) in 60 min. The XRD and photoluminescence emission spectroscopy characterization of the BiOBr-G10 samples indicates an increased crystallization of BiOBr and efficient quenching of photo-excited electrons and holes contributes to the improved photocatalytic activities.

  15. A three-dimensional BiOBr/RGO heterostructural aerogel with enhanced and selective photocatalytic properties under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Xue [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qing dao 266100 (China); Shi, Junjie, E-mail: junjieshiding@gmail.com [Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Str. UFT, 28359 Bremen (Germany); Feng, Lijuan; Li, Chunhu [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qing dao 266100 (China); Wang, Liang, E-mail: wangliangouc@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qing dao 266100 (China)

    2017-02-28

    Highlights: • A BiOBr/RGO aerogel photocatalyst was synthesized using dopamine as reducing agent. • BiOBr/RGO aerogel can be easily controlled morphology by a simple two-step method. • BiOBr/RGO aerogel photocatalyst exhibited superior performance in MO decoloration. - Abstract: A series of BiOBr/reduced graphene oxide (RGO) aerogel was fabricated using a two steps hydrothermal method. Various methods such as SEM, TEM, DRS and Raman spectroscopy were employed to fully characterize the as-obtained BiOBr/RGO. Their photocatalytic degradation of methyl orange (MO) were studied under visible light irradiation. The combination of BiOBr and RGO result in an improved activity. The sample with 10 wt% RGO abbreviated as BiOBr-G10 shows the highest activity. Moreover, this sample exhibits a selective visible-light photocatalytic behavior as the degradation rate over MO (80%) is much higher than that over Rhodamin B (50%) and phenol (35%) in 60 min. The XRD and photoluminescence emission spectroscopy characterization of the BiOBr-G10 samples indicates an increased crystallization of BiOBr and efficient quenching of photo-excited electrons and holes contributes to the improved photocatalytic activities.

  16. Three dimensional nitrogen-doped graphene aerogels functionalized with melamine for multifunctional applications in supercapacitors and adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Ling-Bao; Hou, Shu-Fen; Zhou, Jin; Zhang, Jing-Li; Si, Weijiang; Dong, Yunhui, E-mail: hgxydyh@sdut.edu.cn; Zhuo, Shuping, E-mail: zhuosp_academic@yahoo.com

    2015-10-15

    In present work, we demonstrate an efficient and facile strategy to fabricate three-dimensional (3D) nitrogen-doped graphene aerogels (NGAs) based on melamine, which serves as reducing and functionalizing agent of graphene oxide (GO) in an aqueous medium with ammonia. Benefiting from well-defined and cross-linked 3D porous network architectures, the supercapacitor based on the NGAs exhibited a high specific capacitance of 170.5 F g{sup −1} at 0.2 A g{sup −1}, and this capacitance also showed good electrochemical stability and a high degree of reversibility in the repetitive charge/discharge cycling test. More interestingly, the prepared NGAs further exhibited high adsorption capacities and high recycling performance toward several metal ions such as Pb{sup 2+}, Cu{sup 2+} and Cd{sup 2+}. Moreover, the hydrophobic carbonized nitrogen-doped graphene aerogels (CNGAs) showed outstanding adsorption and recycling performance for the removal of various oils and organic solvents. - Graphical abstract: Three-dimensional nitrogen-doped graphene aerogels were prepared by using melamine as reducing and functionalizing agent in an aqueous medium with ammonia, which showed multifunctional applications in supercapacitors and adsorption. - Highlights: • Three-dimensional nitrogen-doped graphene aerogels (NGAs) were prepared. • Melamine was used as reducing and functionalizing agent. • NGAs exhibited relatively good electrochemical properties in supercapacitor. • NGAs exhibited high adsorption performance toward several metal ions. • CNGAs showed outstanding adsorption capacities for various oils and solvents.

  17. Single-Site Palladium(II) Catalyst for Oxidative Heck Reaction: Catalytic Performance and Kinetic Investigations

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Hui; Li, Mengyang; Zhang, Guanghui; Gallagher, James R.; Huang, Zhiliang; Sun, Yu; Luo, Zhong; Chen, Hongzhong; Miller, Jeffrey T.; Zou, Ruqiang; Lei, Aiwen; Zhao, Yanli

    2015-01-01

    ABSTRACT: The development of organometallic single-site catalysts (SSCs) has inspired the designs of new heterogeneous catalysts with high efficiency. Nevertheless, the application of SSCs in certain modern organic reactions, such as C-C bond formation reactions, has still been less investigated. In this study, a single-site Pd(II) catalyst was developed, where 2,2'-bipyridine-grafted periodic mesoporous organosilica (PMO) was employed as the support of a Pd(II) complex. The overall performance of the single-site Pd(II) catalyst in the oxidative Heck reaction was then investigated. The investigation results show that the catalyst displays over 99% selectivity for the product formation with high reaction yield. Kinetic profiles further confirm its high catalytic efficiency, showing that the rate constant is nearly 40 times higher than that for the free Pd(II) salt. X-ray absorption spectroscopy reveals that the catalyst has remarkable lifetime and recyclability.

  18. Decoupling photochemical Fe(II) oxidation from shallow-water BIF deposition

    DEFF Research Database (Denmark)

    Konhauser, Kurt; Amskold, Larry; Lalonde, Stefan

    2007-01-01

    to the rise of atmospheric oxygen and the development of a protective ozone layer, the Earth's surface was subjected to high levels of ultraviolet radiation. Bulk ocean waters that were anoxic at this time could have supported high concentrations of dissolved Fe(II). Under such conditions, dissolved ferrous...... for biology [Fran??ois, L.M., 1986, Extensive deposition of banded iron formations was possible without photosynthesis. Nature 320, 352-354]. Here, we evaluate the potential importance of photochemical oxidation using a combination of experiments and thermodynamic models. The experiments simulate......-type systems, then we are driven to conclude that oxide-facies BIF are the product of a rapid, non-photochemical oxidative process, the most likely candidates being direct or indirect biological oxidation, and that a significant fraction of BIF could have initially been deposited as ferrous minerals. ?? 2007...

  19. Silver-Loaded Aluminosilicate Aerogels As Iodine Sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Kroll, Jared O. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Peterson, Jacob A. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Matyáš, Josef [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Olszta, Matthew J. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Li, Xiaohong [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Vienna, John D. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States

    2017-09-14

    This paper discusses the development of aluminosilicates aerogels as scaffolds for Ag0 nanoparticles used for chemisorption of I2(g). The starting materials for these scaffolds included both Na-Al-Si-O and Al-Si-O aerogels, both synthesized from metal alkoxides. The Ag0 particles are added by soaking the aerogels in AgNO3 followed by drying and flowing under H2/Ar to reduce Ag+ → Ag0. In some cases, samples were soaked in 3-(mercaptopropyl)trimethoxysilane under supercritical CO2 to add –SH tethers to the aerogel surfaces for more effective binding of Ag+. During the Ag+-impregnation steps, for the Na-Al-Si-O aerogels, Na was replaced with Ag, and for the Al-Si-O aerogel, Si was replaced with Ag. The Ag-loading of thiolated versus non-thiolated Na-Al-Si-O aerogels was comparable at ~35 at% whereas the Ag-loading in unthiolated Al-Si-O aerogels was significantly lower at ~ 7 at% after identical treatment. Iodine loadings in both thiolated and unthiolated Ag0-functionalized Na-Al-Si-O aerogels were > 0.5 g g-1 showing almost complete utilization of the Ag through chemisorption to form AgI. Iodine loading in the thiolated Al-Si-O aerogel was 0.31 g g-1. The control of Ag uptake over solution residence time and [AgNO3] demonstrates the ability to customize the Ag-loading in the base sorbent to regulate the capacity of iodine chemisorption. Consolidation experimental results are also presented.

  20. Steam assisted oxide growth on aluminium alloys using oxidative chemistries: Part II corrosion performance

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Jellesen, Morten Stendahl; Ambat, Rajan

    2015-01-01

    the protection provided by steam treatment with HNO3was a function of the concentration of NO3−ions. The coating generated by inclusion of KMnO4showed highest resistance to filiform corrosion. Overall, the performance of the steam treated surfaces under filiform corrosion and AASS test was a result of the local......Surface treatment of aluminium alloys using steam with oxidative chemistries, namely KMnO4 and HNO3 resulted in accelerated growth of oxide on aluminium alloys. Detailed investigation of the corrosion performance of the treated surfaces was carried out using potentiodynamic polarisation...

  1. Acclimation of a marine microbial consortium for efficient Mn(II) oxidation and manganese containing particle production

    International Nuclear Information System (INIS)

    Zhou, Hao; Pan, Haixia; Xu, Jianqiang; Xu, Weiping; Liu, Lifen

    2016-01-01

    Highlights: • An efficient Mn(II) oxidation marine sediments microbial community was obtained. • High-throughput sequencing indicated new Mn(II) oxidation associated genus. • Na_3MnPO_4CO_3 and MnCO_3 were synthesized by the consortium. • Consortium exhibited Mn(II) oxidation performance over a range of harsh conditions. - Abstract: Sediment contamination with metals is a widespread concern in the marine environment. Manganese oxidizing bacteria (MOB) are extensively distributed in various environments, but a marine microbial community containing MOB is rarely reported. In this study, a consortium of marine metal-contaminated sediments was acclimated using Mn(II). The shift in community structure was determined through high-throughput sequencing. In addition, the consortium resisted several harsh conditions, such as toxic metals (1 mM Cu(II) and Fe(III)), and exhibited high Mn(II) oxidation capacities even the Mn(II) concentration was up to 5 mM. Meanwhile, biogenic Mn containing particles were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and N_2 adsorption/desorption. Dye removal performance of the Mn containing particles was assayed using methylene blue, and 20.8 mg g"−"1 adsorption capacity was obtained. Overall, this study revealed several new genera associated with Mn(II) oxidation and rare biogenic Na_3MnPO_4CO_3_. Results suggested the complexity of natural microbe-mediated Mn transformation.

  2. Linking Mn(II)-oxidizing bacteria to natural attenuation at a former U mining site

    Science.gov (United States)

    Akob, D.; Bohu, T.; Beyer, A.; Schäffner, F.; Händel, M.; Johnson, C.; Merten, D.; Büchel, G.; Totsche, K.; Küsel, K.

    2012-04-01

    Uranium mining near Ronneburg, Germany resulted in widespread environmental contamination with acid mine drainage (AMD) and high concentrations of heavy metals and radionuclides. Despite physical remediation of the area, groundwater is still a source of heavy metal contaminants, e.g., Cd, Ni, Co, Cu and Zn, to nearby ecosystems. However, natural attenuation of heavy metals is occurring in Mn oxide rich soils and sediments ranging in pH from 5 to 7. While microorganisms readily oxidize Mn(II) and precipitate Mn oxides at pH ~7 under oxic conditions, few studies describe Mn(II)-oxidizing bacteria (MOB) at pH ~5 and/or in the presence of heavy metals. In this study we (1) isolated MOB from the contaminated Ronneburg area at pH 5.5 and 7 and (2) evaluated the biological formation of Mn oxides. We isolated nine MOB strains at pH 7 (members of the Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes phyla) and a single isolate at pH 5.5 (Oxalobacteraceae isolate AB_14, within the β-Proteobacteria). LA-ICP-MS showed that all isolates accumulated Mn and Fe in their biomass. However, the Oxalobacteraceae isolate AB_14 oxidizes more Mn without additional Fe in the medium. Preliminary FTIR analysis indicated that all isolates formed precipitates, which showed absorption bands that were characteristic for birnessite. High resolution TEM showed variable morphology of precipitates and EDS confirmed the presence of Mn oxides. Isolate AB_14 was not surrounded with precipitates whereas our Actinobacteria isolate AB_18 was encrusted with Mn oxides. Electron diffraction is currently being used to confirm the presence of birnessite and other Mn oxide phases. This, the first known report of any organism capable of Mn oxidation at low pH, demonstrated that MOB can be involved in the natural attenuation of both moderately acidic and neutral pH soils and sediments via the formation of biogenic Mn oxides. Future work will fully evaluate the minerals formed in this process as well

  3. Dichloroacetate Decreases Cell Health and Activates Oxidative Stress Defense Pathways in Rat Alveolar Type II Pneumocytes

    Directory of Open Access Journals (Sweden)

    Alexis Valauri-Orton

    2015-01-01

    Full Text Available Dichloroacetate (DCA is a water purification byproduct that is known to be hepatotoxic and hepatocarcinogenic and to induce peripheral neuropathy and damage macrophages. This study characterizes the effects of the haloacetate on lung cells by exposing rat alveolar type II (L2 cells to 0–24 mM DCA for 6–24 hours. Increasing DCA concentration and the combination of increasing DCA concentration plus longer exposures decrease measures of cellular health. Length of exposure has no effect on oxidative stress biomarkers, glutathione, SOD, or CAT. Increasing DCA concentration alone does not affect total glutathione or its redox ratio but does increase activity in the SOD/CAT oxidative stress defense pathway. These data suggest that alveolar type II cells rely on SOD and CAT more than glutathione to combat DCA-induced stress.

  4. Assembly of phosphide nanocrystals into porous networks: formation of InP gels and aerogels.

    Science.gov (United States)

    Hitihami-Mudiyanselage, Asha; Senevirathne, Keerthi; Brock, Stephanie L

    2013-02-26

    The applicability of sol-gel nanoparticle assembly routes, previously employed for metal chalcogenides, to phosphides is reported for the case of InP. Two different sizes (3.5 and 6.0 nm) of InP nanoparticles were synthesized by solution-phase arrested precipitation, capped with thiolate ligands, and oxidized with H₂O₂ or O₂/light to induce gel formation. The gels were aged, solvent-exchanged, and then supercritically dried to obtain aerogels with both meso- (2-50 nm) and macropores (>50 nm) and accessible surface areas of ∼200 m²/g. Aerogels showed higher band gap values relative to precursor nanoparticles, suggesting that during the process of assembling nanoparticles into 3D architectures, particle size reduction may have taken place. In contrast to metal chalcogenide gelation, InP gels did not form using tetranitromethane, a non-oxygen-transferring oxidant. The requirement of an oxygen-transferring oxidant, combined with X-ray photoelectron spectroscopy data showing oxidized phosphorus, suggests gelation is occurring due to condensation of phosphorus oxoanionic moieties generated at the interfaces. The ability to link discrete InP nanoparticles into a 3D porous network while maintaining quantum confinement is expected to facilitate exploitation of nanostructured InP in solid-state devices.

  5. Uranium Immobilization through Fe(II) bio-oxidation: A Column study

    Energy Technology Data Exchange (ETDEWEB)

    Coates, John D.

    2009-09-14

    Current research on the bioremediation of heavy metals and radionuclides is focused on the ability of reducing organisms to use these metals as alternative electron acceptors in the absence of oxygen and thus precipitate them out of solution. However, many aspects of this proposed scheme need to be resolved, not the least of which is the time frame of the treatment process. Once treatment is complete and the electron donor addition is halted, the system will ultimately revert back to an oxic state and potentially result in the abiotic reoxidation and remobilization of the immobilized metals. In addition, the possibility exists that the presence of more electropositive electron acceptors such as nitrate or oxygen will also stimulate the biological oxidation and remobilization of these contaminants. The selective nitrate-dependent biooxidation of added Fe(II) may offer an effective means of “capping off” and completing the attenuation of these contaminants in a reducing environment making the contaminants less accessible to abiotic and biotic reactions and allowing the system to naturally revert to an oxic state. Our previous DOE-NABIR funded studies demonstrated that radionuclides such as uranium and cobalt are rapidly removed from solution during the biogenic formation of Fe(III)-oxides. In the case of uranium, X-ray spectroscopy analysis indicated that the uranium was in the hexavalent form (normally soluble) and was bound to the precipitated Fe(III)-oxides thus demonstrating the bioremediative potential of this process. We also demonstrated that nitrate-dependent Fe(II)- oxidizing bacteria are prevalent in the sediment and groundwater samples collected from sites 1 and 2 and the background site of the NABIR FRC in Oakridge, TN. However, all of these studies were performed in batch experiments in the laboratory with pure cultures and although a significant amount was learned about the microbiology of nitrate-dependent bio-oxidation of Fe(II), the effects of

  6. Kinetic Investigations on Pd(II) Catalyzed Oxidation of Some Amino ...

    African Journals Online (AJOL)

    Kinetic investigations on Pd(II) catalyzed oxidation of dl-serine and dl-threonine by acidic solution of potassium bromate in the presence of mercuric acetate, as a scavenger have been made in the temperature range of 30–45°C. The rate shows zero order kinetics in bromate [BrO3‾] and order of reaction is one with respect ...

  7. Novel polybenzoxazine-based carbon aerogel electrode for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Katanyoota, Porawee [Petroleum and Petrochemical College and National Center of Excellence for Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand); Chaisuwan, Thayanlak, E-mail: thanyalak.c@hotmail.co [Petroleum and Petrochemical College and National Center of Excellence for Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand); Wongchaisuwat, Atchana [Department of Chemistry, Kasetsart University, Bangkok 10900 (Thailand); Wongkasemjit, Sujitra, E-mail: dsujitra@chula.ac.t [Petroleum and Petrochemical College and National Center of Excellence for Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand)

    2010-02-25

    In this study, polybenzoxazine, a new high performance thermosetting resin, was used to prepare carbon aerogels used as an electrode for supercapacitors. Two types of polybenzoxazines, derived from two different amines, aniline and triethylenetetramine, and denoted as BA-a and BA-teta, respectively, were chosen as the reactants for the organic precursor preparation. The surface area of carbon aerogels from both BA-a and BA-teta was 391 and 368 m{sup 2}/g, respectively. The pore size of each carbon aerogel was in the range of 2-5 nm, which is a suitable pore size for use as electrodes in electrochemical applications. The electrochemical properties of the obtained carbon aerogels showed good performance for supercapacitor applications with a specific capacitance of 55.78 and 20.53 F/g for BA-teta and BA-a, respectively. At low voltage scanning, 1 and 5 mV/s, the cyclic voltammogram of the carbon aerogel derived from BA-teta gave a better rectangular shape than that of the other carbon aerogel. The impedance spectra of both carbon aerogels confirmed the results of the capacitance and the cyclic voltammogram analyses.

  8. Novel polybenzoxazine-based carbon aerogel electrode for supercapacitors

    International Nuclear Information System (INIS)

    Katanyoota, Porawee; Chaisuwan, Thayanlak; Wongchaisuwat, Atchana; Wongkasemjit, Sujitra

    2010-01-01

    In this study, polybenzoxazine, a new high performance thermosetting resin, was used to prepare carbon aerogels used as an electrode for supercapacitors. Two types of polybenzoxazines, derived from two different amines, aniline and triethylenetetramine, and denoted as BA-a and BA-teta, respectively, were chosen as the reactants for the organic precursor preparation. The surface area of carbon aerogels from both BA-a and BA-teta was 391 and 368 m 2 /g, respectively. The pore size of each carbon aerogel was in the range of 2-5 nm, which is a suitable pore size for use as electrodes in electrochemical applications. The electrochemical properties of the obtained carbon aerogels showed good performance for supercapacitor applications with a specific capacitance of 55.78 and 20.53 F/g for BA-teta and BA-a, respectively. At low voltage scanning, 1 and 5 mV/s, the cyclic voltammogram of the carbon aerogel derived from BA-teta gave a better rectangular shape than that of the other carbon aerogel. The impedance spectra of both carbon aerogels confirmed the results of the capacitance and the cyclic voltammogram analyses.

  9. MOLECULAR DESCRIPTION OF ELECTROLYTE SOLUTION IN A CARBON AEROGEL ELECTRODE

    Directory of Open Access Journals (Sweden)

    A.Kovalenko

    2003-01-01

    Full Text Available We develop a molecular theory of aqueous electrolyte solution sorbed in a nanoporous carbon aerogel electrode, based on the replica reference interaction site model (replica RISM for realistic molecular quenched-annealed systems. We also briefly review applications of carbon aerogels for supercapacitor and electrochemical separation devices, as well as theoretical and computer modelling of disordered porous materials. The replica RISM integral equation theory yields the microscopic properties of the electrochemical double layer formed at the surface of carbon aerogel nanopores, with due account of chemical specificities of both sorbed electrolyte and carbon aerogel material. The theory allows for spatial disorder of aerogel pores in the range from micro- to macroscopic size scale. We considered ambient aqueous solution of 1 M sodium chloride sorbed in two model nanoporous carbon aerogels with carbon nanoparticles either arranged into branched chains or randomly distributed. The long-range correlations of the carbon aerogel nanostructure substantially affect the properties of the electrochemical double layer formed by the solution sorbed in nanopores.

  10. Biochemistry and Ecology of Novel Cytochromes Catalyzing Fe(II) Oxidation by an Acidophilic Microbial Community

    Science.gov (United States)

    Singer, S. W.; Jeans, C. J.; Thelen, M. P.; Verberkmoes, N. C.; Hettich, R. C.; Chan, C. S.; Banfield, J. F.

    2007-12-01

    An acidophilic microbial community found in the Richmond Mine at Iron Mountain, CA forms abundant biofilms in extremely acidic (pHindicated that several variants of Cyt579 were present in Leptospirillum strains. Intact protein MS analysis identified the dominant variants in each biofilm and documented multiple N-terminal cleavage sites for Cyt579. By combining biochemical, geochemical and microbiological data, we established that the sequence variation and N-terminal processing of Cyt579 are selected by ecological conditions. In addition to the soluble Cyt579, the second cytochrome appears as a much larger protein complex of ~210 kDa predominant in the biofilm membrane fraction, and has an alpha-band absorption at 572 nm. The 60 kDa cytochrome subunit, Cyt572, resides in the outer membrane of LeptoII, and readily oxidizes Fe(II) at low pH (0.95 - 3.0). Several genes encoding Cyt572 were localized within a recombination hotspot between two strains of LeptoII, causing a large range of variation in the sequences. Genomic sequencing and MS proteomic studies established that the variants were also selected by ecological conditions. A general mechanistic model for Fe(II) oxidation has been developed from these studies. Initial Fe(II) oxidation by Cyt572 occurs at the outer membrane. Cyt572 then transfers electrons to Cyt579, perhaps representing an initial step in energy flow to the biofilm community. Amino acid variations and post-translational modifications of these unique cytochromes may represent fine-tuning of function in response to local environmental conditions.

  11. Reactive Transport Modeling of Microbe-mediated Fe (II) Oxidation for Enhanced Oil Recovery

    Science.gov (United States)

    Surasani, V.; Li, L.

    2011-12-01

    Microbially Enhanced Oil Recovery (MEOR) aims to improve the recovery of entrapped heavy oil in depleted reservoirs using microbe-based technology. Reservoir ecosystems often contain diverse microbial communities those can interact with subsurface fluids and minerals through a network of nutrients and energy fluxes. Microbe-mediated reactions products include gases, biosurfactants, biopolymers those can alter the properties of oil and interfacial interactions between oil, brine, and rocks. In addition, the produced biomass and mineral precipitates can change the reservoir permeability profile and increase sweeping efficiency. Under subsurface conditions, the injection of nitrate and Fe (II) as the electron acceptor and donor allows bacteria to grow. The reaction products include minerals such as Fe(OH)3 and nitrogen containing gases. These reaction products can have large impact on oil and reservoir properties and can enhance the recovery of trapped oil. This work aims to understand the Fe(II) oxidation by nitrate under conditions relevant to MEOR. Reactive transport modeling is used to simulate the fluid flow, transport, and reactions involved in this process. Here we developed a complex reactive network for microbial mediated nitrate-dependent Fe (II) oxidation that involves both thermodynamic controlled aqueous reactions and kinetic controlled Fe (II) mineral reaction. Reactive transport modeling is used to understand and quantify the coupling between flow, transport, and reaction processes. Our results identify key parameter controls those are important for the alteration of permeability profile under field conditions.

  12. Oxidation of Dodecanoate Intercalated Iron(II)–Iron(III) Layered Double Hydroxide to Form 2D Iron(III) (Hydr)oxide Layers

    DEFF Research Database (Denmark)

    Huang, Li‐Zhi; Ayala‐Luis, Karina B.; Fang, Liping

    2013-01-01

    hydroxide planar layer were preserved during the oxidation, as shown by FTIR spectroscopy. The high positive charge in the hydroxide layer produced by the oxidation of iron(II) to iron(III) is partially compensated by the deprotonation of hydroxy groups, as shown by X‐ray photoelectron spectroscopy...... between the alkyl chains of the intercalated dodecanoate anions play a crucial role in stabilizing the structure and hindering the collapse of the iron(II)–iron(III) (hydr)oxide structure during oxidation. This is the first report describing the formation of a stable planar layered octahedral iron......(III) (hydr)oxide. oxGRC12 shows promise as a sorbent and host for hydrophobic reagents, and as a possible source of single planar layers of iron(III) (hydr)oxide....

  13. Synthesis and Characterization Carbon Nanotubes Doped Carbon Aerogels

    Science.gov (United States)

    Xu, Yuelong; Yan, Meifang; Liu, Zhenfa

    2017-12-01

    Polycondensation of phloroglucinol, resorcinol and formaldehyde with carbon nanotube (CNT) as the additives, using sodium carbonate as the catalyst, leads to the formation of CNT - doped carbon aerogels. The structure of carbon aerogels (CAs) with carbon nanotubes (CNTs) were characterized by X-ray diffraction and scanning electron microscopy. The specific surface area, pore size distribution and pore volume were measured by surface area analyzer. The results show that when the optimum doping dosage is 5%, the specific surface area of CNT - doped carbon aerogel is up to 665 m2 g-1 and exhibit plentiful mesoporous.

  14. Cucumis sativus Aqueous Fraction Inhibits Angiotensin II-Induced Inflammation and Oxidative Stress In Vitro

    Directory of Open Access Journals (Sweden)

    Celeste Trejo-Moreno

    2018-02-01

    Full Text Available Inflammation and oxidative stress play major roles in endothelial dysfunction, and are key factors in the progression of cardiovascular diseases. The aim of this study was to evaluate in vitro the effect of three subfractions (SFs from the Cucumis sativus aqueous fraction to reduce inflammatory factors and oxidative stress induced by angiotensin II (Ang II in human microvascular endothelial cells-1 (HMEC-1 cells. The cells were cultured with different concentrations of Ang II and 0.08 or 10 μg/mL of SF1, SF2, or SF3, or 10 μmol of losartan as a control. IL-6 (Interleukin 6 concentration was quantified. To identify the most effective SF combinations, HMEC-1 cells were cultured as described above in the presence of four combinations of SF1 and SF3. Then, the effects of the most effective combination on the expression of adhesion molecules, the production of reactive oxygen species (ROS, and the bioavailability of nitric oxide (NO were evaluated. Finally, a mass spectrometry analysis was performed. Both SF1 and SF3 subfractions decreased the induction of IL-6 by Ang II, and C4 (SF1 and SF3, 10 μg/mL each was the most effective combination to inhibit the production of IL-6. Additionally, C4 prevented the expression of adhesion molecules, reduced the production of ROS, and increased the bioavailability of NO. Glycine, arginine, asparagine, lysine, and aspartic acid were the main components of both subfractions. These results demonstrate that C4 has anti-inflammatory and antioxidant effects.

  15. A fluorescent DNA based probe for Hg(II) based on thymine-Hg(II)-thymine interaction and enrichment via magnetized graphene oxide.

    Science.gov (United States)

    Li, Meng-Ke; Hu, Liu-Yin; Niu, Cheng-Gang; Huang, Da-Wei; Zeng, Guang-Ming

    2018-03-03

    The authors describe a fluorometric assay for the determination of Hg(II). A naphthalimide derivative is used as a label for a thymine (T) rich ssDNA, and graphene oxide magnetized with Fe 3 O 4 nanoparticles acts as a quencher and preconcentrators. In the absence of Hg(II), the labeled ssDNA does not separate from the magnetized graphene oxide. As a result, fluorescence is fully quenched. In the presence of Hg(II), a T-Hg(II)-T link is formed dues to the highly affinity between T and Hg(II). Hence, fluorescence is restored. The assay has a linear response in the 1.0 to 10.0 nM Hg(II) concentration range, and a 0.65 nM detection limit. The method is selective and sensitive. It was applied to the analysis of spiked environmental water samples, and data agreed well with those obtained by atomic fluorescence spectrometry. Graphical abstract Strategy of a fluorescent probe for detecting Hg(II). The method has a 0.65 nM detection limit and is selective. MGO: magnetized graphene oxide, AHN: a fluorescent derivative of naphthalimide.

  16. Oxidized calmodulin kinase II regulates conduction following myocardial infarction: a computational analysis.

    Directory of Open Access Journals (Sweden)

    Matthew D Christensen

    2009-12-01

    Full Text Available Calmodulin kinase II (CaMKII mediates critical signaling pathways responsible for divergent functions in the heart including calcium cycling, hypertrophy and apoptosis. Dysfunction in the CaMKII signaling pathway occurs in heart disease and is associated with increased susceptibility to life-threatening arrhythmia. Furthermore, CaMKII inhibition prevents cardiac arrhythmia and improves heart function following myocardial infarction. Recently, a novel mechanism for oxidative CaMKII activation was discovered in the heart. Here, we provide the first report of CaMKII oxidation state in a well-validated, large-animal model of heart disease. Specifically, we observe increased levels of oxidized CaMKII in the infarct border zone (BZ. These unexpected new data identify an alternative activation pathway for CaMKII in common cardiovascular disease. To study the role of oxidation-dependent CaMKII activation in creating a pro-arrhythmia substrate following myocardial infarction, we developed a new mathematical model of CaMKII activity including both oxidative and autophosphorylation activation pathways. Computer simulations using a multicellular mathematical model of the cardiac fiber demonstrate that enhanced CaMKII activity in the infarct BZ, due primarily to increased oxidation, is associated with reduced conduction velocity, increased effective refractory period, and increased susceptibility to formation of conduction block at the BZ margin, a prerequisite for reentry. Furthermore, our model predicts that CaMKII inhibition improves conduction and reduces refractoriness in the BZ, thereby reducing vulnerability to conduction block and reentry. These results identify a novel oxidation-dependent pathway for CaMKII activation in the infarct BZ that may be an effective therapeutic target for improving conduction and reducing heterogeneity in the infarcted heart.

  17. Electromagnetic interference shielding properties and mechanisms of chemically reduced graphene aerogels

    International Nuclear Information System (INIS)

    Bi, Shuguang; Zhang, Liying; Mu, Chenzhong; Liu, Ming; Hu, Xiao

    2017-01-01

    Graphical abstract: The electromagnetic interference shielding behavior and proposed mechanisms of ultralight free-standing 3D graphene aerogels. - Highlights: • The electromagnetic interference (EMI) shielding properties and mechanisms of ultralight 3D graphene aerogels (GAs) were systematically studied with respect to both the unique porous network and the intrinsic properties of the graphene sheets. • Thickness of the shielding material played a critical role on EMI SE. • By compressing the porous GAs into compact film didnt increase the EMI SE despite the increased electrical conductivity and connectivity. EMI SE is highly dependent on the effective amounts of the materials response to the EM waves. - Abstract: Graphene was recently demonstrated to exhibit excellent electromagnetic interference (EMI) shielding performance. In this work, ultralight (∼5.5 mg/cm"3) graphene aerogels (GAs) were fabricated through assembling graphene oxide (GO) using freeze-drying followed by a chemical reduction method. The EMI shielding properties and mechanisms of GAs were systematically studied with respect to the intrinsic properties of the reduced graphene oxide (rGO) sheets and the unique porous network. The EMI shielding effectiveness (SE) of GAs was increased from 20.4 to 27.6 dB when the GO was reduced by high concentration of hydrazine vapor. The presence of more sp"2 graphitic lattice and free electrons from nitrogen atoms resulted in the enhanced EMI SE. Absorption was the dominant shielding mechanism of GAs. Compressing the highly porous GAs into compact thin films did not change the EMI SE, but shifted the dominant shielding mechanism from absorption to reflection.

  18. Electromagnetic interference shielding properties and mechanisms of chemically reduced graphene aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Bi, Shuguang [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, 637553 (Singapore); Zhang, Liying, E-mail: LY.Zhang@ntu.edu.sg [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, 637553 (Singapore); Mu, Chenzhong [School of Material Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Liu, Ming, E-mail: LIUMING@ntu.edu.sg [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, 637553 (Singapore); Hu, Xiao [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, 637553 (Singapore); School of Material Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

    2017-08-01

    Graphical abstract: The electromagnetic interference shielding behavior and proposed mechanisms of ultralight free-standing 3D graphene aerogels. - Highlights: • The electromagnetic interference (EMI) shielding properties and mechanisms of ultralight 3D graphene aerogels (GAs) were systematically studied with respect to both the unique porous network and the intrinsic properties of the graphene sheets. • Thickness of the shielding material played a critical role on EMI SE. • By compressing the porous GAs into compact film didnt increase the EMI SE despite the increased electrical conductivity and connectivity. EMI SE is highly dependent on the effective amounts of the materials response to the EM waves. - Abstract: Graphene was recently demonstrated to exhibit excellent electromagnetic interference (EMI) shielding performance. In this work, ultralight (∼5.5 mg/cm{sup 3}) graphene aerogels (GAs) were fabricated through assembling graphene oxide (GO) using freeze-drying followed by a chemical reduction method. The EMI shielding properties and mechanisms of GAs were systematically studied with respect to the intrinsic properties of the reduced graphene oxide (rGO) sheets and the unique porous network. The EMI shielding effectiveness (SE) of GAs was increased from 20.4 to 27.6 dB when the GO was reduced by high concentration of hydrazine vapor. The presence of more sp{sup 2} graphitic lattice and free electrons from nitrogen atoms resulted in the enhanced EMI SE. Absorption was the dominant shielding mechanism of GAs. Compressing the highly porous GAs into compact thin films did not change the EMI SE, but shifted the dominant shielding mechanism from absorption to reflection.

  19. Nonlinear hydrodynamic equations for superfluid helium in aerogel

    International Nuclear Information System (INIS)

    Brusov, Peter N.; Brusov, Paul P.

    2003-01-01

    Aerogel in superfluids is studied very intensively during last decade. The importance of these systems is connected to the fact that this allows to investigate the influence of impurities on superfluidity. We have derived for the first time nonlinear hydrodynamic equations for superfluid helium in aerogel. These equations are generalization of McKenna et al. equations for nonlinear hydrodynamics case and could be used to study sound propagation phenomena in aerogel-superfluid system, in particular--to study sound conversion phenomena. We have obtained two alternative sets of equations, one of which is a generalization of a traditional set of nonlinear hydrodynamics equations for the case of an aerogel-superfluid system and, the other one represents a la Putterman equations (equation for v→ s is replaced by equation for A→=((ρ n )/(ρσ))w→, where w→=v→ n -v→ s )

  20. Hexadecane trapped in nano-pores of silica-aerogel

    International Nuclear Information System (INIS)

    Slavikova, B.; Jesenak, K.; Iskrova, M.; Majernik, V.; Sausa, O.; Kristiak, J.

    2009-01-01

    Ways of filling of the high-porous silica-aerogel with hydrocarbon C 16 H 34 and its efficient removal from the pores by physical method of the Positron Annihilation Spectroscopy were studied. As the most effective way to fill the SiO 2 aerogel appears through the implementation of a liquid phase, while the most appropriate way of removing of hexadecane is firing at an elevated temperature. Molecular system of hexadecane closed in nano-pores of silica-aerogel behaves otherwise than volume system of the same molecules. In the case of pure hexadecane phase transition was observed at 291 K, while solidification process is gradual with decrease of temperature in cetane trapped in pores of silica-aerogel. The results of the periods of life of o-Ps indicate greater turbidity in the pores of the molecular system compared to the volume sample of hexadecane.

  1. Refractive index of silica aerogel: Uniformity and dispersion law

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Perego, D.L.; Storaci, B.

    2008-01-01

    Two methods for the measurement of the uniformity of the refractive index n within a single block of silica aerogel are described. One is based on the deflection of a laser beam induced by transverse index gradients. The second exploits the Cherenkov effect, measuring the emission angle of photons radiated by 500 MeV electrons traversing the aerogel. The beam can scan the full aerogel surface providing information on point to point variations of n. The measurement of the dispersion law n(λ) is also reported. An Xe lamp coupled to a diffraction grating provides the monochromatic source. The index for each λ is measured by the prism method at a corner of an aerogel sample. A Sellmeier functional form for n(λ) is assumed, and the parameters best fitting the experimental data are given

  2. Aerogel Antennas Communications Study Using Error Vector Magnitude Measurements

    Science.gov (United States)

    Miranda, Felix A.; Mueller, Carl H.; Meador, Mary Ann B.

    2014-01-01

    This presentation discusses an aerogel antennas communication study using error vector magnitude (EVM) measurements. The study was performed using 2x4 element polyimide (PI) aerogel-based phased arrays designed for operation at 5 GHz as transmit (Tx) and receive (Rx) antennas separated by a line of sight (LOS) distance of 8.5 meters. The results of the EVM measurements demonstrate that polyimide aerogel antennas work appropriately to support digital communication links with typically used modulation schemes such as QPSK and 4 DQPSK. As such, PI aerogel antennas with higher gain, larger bandwidth and lower mass than typically used microwave laminates could be suitable to enable aerospace-to- ground communication links with enough channel capacity to support voice, data and video links from CubeSats, unmanned air vehicles (UAV), and commercial aircraft.

  3. Aerogel Antennas Communications Study Using Error Vector Magnitude Measurements

    Science.gov (United States)

    Miranda, Felix A.; Mueller, Carl H.; Meador, Mary Ann B.

    2014-01-01

    This paper discusses an aerogel antennas communication study using error vector magnitude (EVM) measurements. The study was performed using 4x2 element polyimide (PI) aerogel-based phased arrays designed for operation at 5 GHz as transmit (Tx) and receive (Rx) antennas separated by a line of sight (LOS) distance of 8.5 meters. The results of the EVM measurements demonstrate that polyimide aerogel antennas work appropriately to support digital communication links with typically used modulation schemes such as QPSK and pi/4 DQPSK. As such, PI aerogel antennas with higher gain, larger bandwidth and lower mass than typically used microwave laminates could be suitable to enable aerospace-to-ground communication links with enough channel capacity to support voice, data and video links from cubesats, unmanned air vehicles (UAV), and commercial aircraft.

  4. Resolving Iron(II) Sorption and Oxidative Growth on Hematite (001) Using Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Sandra D. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Liu, Jia [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Arey, Bruce W. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Schreiber, Daniel K. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Perea, Daniel E. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Rosso, Kevin M. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States

    2018-02-13

    The distribution of iron resulting from the autocatalytic interaction of aqueous Fe(II) with the hematite (001) surface was directly mapped in three dimensions (3D) for the first time, using iron isotopic labelling and atom probe tomography (APT). Analyses of the mass spectrum showed that natural abundance ratios in 56Fe-dominant hematite are recovered at depth with good accuracy, whereas at the relict interface with 57Fe(II) solution evidence for hematite growth by oxidative adsorption of Fe(II) was found. 3D reconstructions of the isotope positions along the surface normal direction showed a zone enriched in 57Fe, which was consistent with an average net adsorption of 3.2 – 4.3 57Fe atoms nm–2. Statistical analyses utilizing grid-based frequency distribution analyses show a heterogeneous, non-random distribution of oxidized Fe on the (001) surface, consistent with Volmer-Weber-like island growth. The unique 3D nature of the APT data provides an unprecedented means to quantify the atomic-scale distribution of sorbed 57Fe atoms and the extent of segregation on the hematite surface. This new ability to spatially map growth on single crystal faces at the atomic scale will enable resolution to long-standing unanswered questions about the underlying mechanisms for electron and atom exchange involved in a wide variety of redox-catalyzed processes at this archetypal and broadly relevant interface.

  5. Pyoverdine synthesis by the Mn(II-oxidizing bacterium Pseudomonas putida GB-1

    Directory of Open Access Journals (Sweden)

    Dorothy Lundquist Parker

    2014-05-01

    Full Text Available When iron-starved, the Mn(II-oxidizing bacteria Pseudomonas putida strains GB-1 and MnB1 produce pyoverdines (PVDGB-1 and PVDMnB1, siderophores that both influence iron uptake and inhibit manganese(II oxidation by these strains. To explore the properties and genetics of a PVD that can affect manganese oxidation, LC-MS/MS and various siderotyping techniques were used to identify the peptides of PVDGB-1 and PVDMnB1 as being (for both PVDs: chromophore-Asp-Lys-OHAsp-Ser-Gly-aThr-Lys-cOHOrn, resembling a structure previously reported for P. putida CFML 90-51, which does not oxidize Mn. All three strains also produced an azotobactin and a sulfonated PVD, each with the peptide sequence above, but with unknown regulatory or metabolic effects. Bioinformatic analysis of the sequenced genome of P. putida GB-1 suggested that a particular non-ribosomal peptide synthetase, coded by the operon PputGB1_4083-4086, could produce the peptide backbone of PVDGB-1. To verify this prediction, plasmid integration disruption of PputGB1_4083 was performed and the resulting mutant failed to produce detectable PVD. In silico analysis of the modules in PputGB1_4083-4086 predicted a peptide sequence of Asp-Lys-Asp-Ser-Ala-Thr-Lsy-Orn, which closely matches the peptide determined by MS/MS. To extend these studies to other organisms, various Mn(II-oxidizing and non-oxidizing isolates of P. putida, P. fluorescens, P. marincola, P. fluorescens-syringae group, P. mendocina-resinovorans group and P. stutzerii group were screened for PVD synthesis. The PVD producers (12 out of 16 tested strains were siderotyped and placed into four sets of differing PVD structures, some corresponding to previously characterized PVDs and some to novel PVDs. These results combined with previous studies suggested that the presence of OHAsp or the flexibility of the pyoverdine polypeptide may enable efficient binding of Mn(III.

  6. Pyoverdine synthesis by the Mn(II)-oxidizing bacterium Pseudomonas putida GB-1

    Science.gov (United States)

    Parker, Dorothy L.; Lee, Sung-Woo; Geszvain, Kati; Davis, Richard E.; Gruffaz, Christelle; Meyer, Jean-Marie; Torpey, Justin W.; Tebo, Bradley M.

    2014-01-01

    When iron-starved, the Mn(II)-oxidizing bacteria Pseudomonas putida strains GB-1 and MnB1 produce pyoverdines (PVDGB-1 and PVDMnB1), siderophores that both influence iron uptake and inhibit manganese(II) oxidation by these strains. To explore the properties and genetics of a PVD that can affect manganese oxidation, LC-MS/MS, and various siderotyping techniques were used to identify the peptides of PVDGB-1 and PVDMnB1 as being (for both PVDs): chromophore-Asp-Lys-OHAsp-Ser-Gly-aThr-Lys-cOHOrn, resembling a structure previously reported for P. putida CFML 90-51, which does not oxidize Mn. All three strains also produced an azotobactin and a sulfonated PVD, each with the peptide sequence above, but with unknown regulatory or metabolic effects. Bioinformatic analysis of the sequenced genome of P. putida GB-1 suggested that a particular non-ribosomal peptide synthetase (NRPS), coded by the operon PputGB1_4083-4086, could produce the peptide backbone of PVDGB-1. To verify this prediction, plasmid integration disruption of PputGB1_4083 was performed and the resulting mutant failed to produce detectable PVD. In silico analysis of the modules in PputGB1_4083-4086 predicted a peptide sequence of Asp-Lys-Asp-Ser-Ala-Thr-Lsy-Orn, which closely matches the peptide determined by MS/MS. To extend these studies to other organisms, various Mn(II)-oxidizing and non-oxidizing isolates of P. putida, P. fluorescens, P. marincola, P. fluorescens-syringae group, P. mendocina-resinovorans group, and P. stutzerii group were screened for PVD synthesis. The PVD producers (12 out of 16 tested strains) were siderotyped and placed into four sets of differing PVD structures, some corresponding to previously characterized PVDs and some to novel PVDs. These results combined with previous studies suggested that the presence of OHAsp or the flexibility of the pyoverdine polypeptide may enable efficient binding of Mn(III). PMID:24847318

  7. Metallothionein-I plus II and receptor megalin are altered in relation to oxidative stress in cerebral lymphomas

    DEFF Research Database (Denmark)

    Pedersen, M.O.; Hansen, P.B.; Nielsen, Signe Ledou

    2010-01-01

    . This article characterizes the histopathology and expression profiles of metallothionein-I + II (MT-I + II) and their receptor megalin along with proliferation, oxidative stress, and apoptosis in PCNSL and in central nervous system (CNS) lymphomas due to relapse from DLBCL (collectively referred to as CNS...

  8. Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II precursor

    Directory of Open Access Journals (Sweden)

    N.V. Nikolenko

    2018-03-01

    Full Text Available It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II as a precursor instead of Fe(III. This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III oxide impurities which are detrimental for the process selectivity. The system containing Fe(II and Mo(VI species in aqueous solution was investigated using UV–Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II–Mo(VI system: (i formation of complexes between Fe(II and molybdate(VI ions, (ii inner sphere oxidation of coordinated Fe(II by Mo(VI and (iii decomposition of the Fe–Mo complexes to form scarcely soluble Fe(III molybdate, Mo(VI hydrous trioxide and molybdenum blue. Solid molybdoferrate(II prepared by interaction of Fe(II and Mo(VI in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II precursor was tested in methanol-to-formaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III.

  9. A RICH with aerogel: a study of refractive index uniformity

    CERN Document Server

    Alemi, M; Calvi, M; Matteuzzi, C; Musy, M; Perego, D L; Easo, S

    2004-01-01

    The use of aerogel as a radiator in the RICH detectors of LHCb is a challenge due to the hot environment of the hadron collider LHC. Large size tiles of silica aerogel were recently produced with unprecedented optical quality for such dimensions. Results of laboratory measurements and beam tests are briefly reported. A description of a method to measure the uniformity of the index of refraction within the tile is given.

  10. Polyimide-Foam/Aerogel Composites for Thermal Insulation

    Science.gov (United States)

    Williams, Martha; Fesmire, James; Sass, Jared; Smith, Trent; Weoser. Erol

    2009-01-01

    Composites of specific types of polymer foams and aerogel particles or blankets have been proposed to obtain thermal insulation performance superior to those of the neat polyimide foams. These composites have potential to also provide enhanced properties for vibration dampening or acoustic attenuation. The specific type of polymer foam is denoted "TEEK-H", signifying a series, denoted H, within a family of polyimide foams that were developed at NASA s Langley Research Center and are collectively denoted TEEK (an acronym of the inventors names). The specific types of aerogels include Nanogel aerogel particles from Cabot Corporation in Billerica, MA. and of Spaceloft aerogel blanket from Aspen Aerogels in Northborough, MA. The composites are inherently flame-retardant and exceptionally thermally stable. There are numerous potential uses for these composites, at temperatures from cryogenic to high temperatures, in diverse applications that include aerospace vehicles, aircraft, ocean vessels, buildings, and industrial process equipment. Some low-temperature applications, for example, include cryogenic storage and transfer or the transport of foods, medicines, and chemicals. Because of thermal cycling, aging, and weathering most polymer foams do not perform well at cryogenic temperatures and will undergo further cracking over time. The TEEK polyimides are among the few exceptions to this pattern, and the proposed composites are intended to have all the desirable properties of TEEK-H foams, plus improved thermal performance along with enhanced vibration or acoustic-attenuation performance. A composite panel as proposed would be fabricated by adding an appropriate amount of TEEK friable balloons into a mold to form a bottom layer. A piece of flexible aerogel blanket material, cut to the desired size and shape, would then be placed on the bottom TEEK layer and sandwiched between another top layer of polyimide friable balloons so that the aerogel blanket would become

  11. Biological low pH Mn(II) oxidation in a manganese deposit influenced by metal-rich groundwater

    Science.gov (United States)

    Bohu, Tsing; Akob, Denise M.; Abratis, Michael; Lazar, Cassandre S.; Küsel, Kirsten

    2016-01-01

    The mechanisms, key organisms, and geochemical significance of biological low-pH Mn(II) oxidation are largely unexplored. Here, we investigated the structure of indigenous Mn(II)-oxidizing microbial communities in a secondary subsurface Mn oxide deposit influenced by acidic (pH 4.8) metal-rich groundwater in a former uranium mining area. Microbial diversity was highest in the Mn deposit compared to the adjacent soil layers and included the majority of known Mn(II)-oxidizing bacteria (MOB) and two genera of known Mn(II)-oxidizing fungi (MOF). Electron X-ray microanalysis showed that romanechite [(Ba,H2O)2(Mn4+,Mn3+)5O10] was conspicuously enriched in the deposit. Canonical correspondence analysis revealed that certain fungal, bacterial, and archaeal groups were firmly associated with the autochthonous Mn oxides. Eight MOB within the Proteobacteria, Actinobacteria, and Bacteroidetes and one MOF strain belonging to Ascomycota were isolated at pH 5.5 or 7.2 from the acidic Mn deposit. Soil-groundwater microcosms demonstrated 2.5-fold-faster Mn(II) depletion in the Mn deposit than adjacent soil layers. No depletion was observed in the abiotic controls, suggesting that biological contribution is the main driver for Mn(II) oxidation at low pH. The composition and species specificity of the native low-pH Mn(II) oxidizers were highly adapted to in situ conditions, and these organisms may play a central role in the fundamental biogeochemical processes (e.g., metal natural attenuation) occurring in the acidic, oligotrophic, and metalliferous subsoil ecosystems.

  12. Modeling silica aerogel optical performance by determining its radiative properties

    Science.gov (United States)

    Zhao, Lin; Yang, Sungwoo; Bhatia, Bikram; Strobach, Elise; Wang, Evelyn N.

    2016-02-01

    Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM). Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation). To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm) of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE). The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel's microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain.

  13. Three dimensional nitrogen-doped graphene aerogels functionalized with melamine for multifunctional applications in supercapacitors and adsorption

    Science.gov (United States)

    Xing, Ling-Bao; Hou, Shu-Fen; Zhou, Jin; Zhang, Jing-Li; Si, Weijiang; Dong, Yunhui; Zhuo, Shuping

    2015-10-01

    In present work, we demonstrate an efficient and facile strategy to fabricate three-dimensional (3D) nitrogen-doped graphene aerogels (NGAs) based on melamine, which serves as reducing and functionalizing agent of graphene oxide (GO) in an aqueous medium with ammonia. Benefiting from well-defined and cross-linked 3D porous network architectures, the supercapacitor based on the NGAs exhibited a high specific capacitance of 170.5 F g-1 at 0.2 A g-1, and this capacitance also showed good electrochemical stability and a high degree of reversibility in the repetitive charge/discharge cycling test. More interestingly, the prepared NGAs further exhibited high adsorption capacities and high recycling performance toward several metal ions such as Pb2+, Cu2+ and Cd2+. Moreover, the hydrophobic carbonized nitrogen-doped graphene aerogels (CNGAs) showed outstanding adsorption and recycling performance for the removal of various oils and organic solvents.

  14. 3D nitrogen-doped graphene aerogel nanomesh: Facile synthesis and electrochemical properties as the electrode materials for supercapacitors

    Science.gov (United States)

    Su, Xiao-Li; Fu, Lin; Cheng, Ming-Yu; Yang, Jing-He; Guan, Xin-Xin; Zheng, Xiu-Cheng

    2017-12-01

    Nitrogen-doped graphene aerogel nanomesh (N-GANM) has been hydrothermally prepared from graphene oxide and ammonium hydroxide using iron nitrate as the etching agent. The results showed that N-GANM with an interesting nanomesh structure on the graphene sheets maintained the 3D architecture of graphene aerogel (GA). Furthermore, it exhibited excellent electrochemical capacitive behavior and the specific capacitance value (290.0 F g-1 at 1 A g-1) remained approximately 90.3% after 2000 cycles in the three-electrode system. In addition, N-GANM displayed an energy density of 30.9 Wh kg-1 at the power density of 450.3 W kg-1 and excellent cycling stability retention (98%) after 10,000 cycles in the two-electrode symmetric device. The resulting N-GANM was expected to be a much favorable supercapacitor electrode material due to the heteroatom-doping and its unique porous structure.

  15. Fluorescence-based detection of nitric oxide in aqueous and methanol media using a copper(II) complex.

    Science.gov (United States)

    Mondal, Biplab; Kumar, Pankaj; Ghosh, Pokhraj; Kalita, Apurba

    2011-03-14

    The quenched fluorescent intensity of a copper(II) complex, 1, of a fluorescent ligand, in degassed methanol or aqueous (buffered at pH 7.2) solution, was found to reappear on exposure to nitric oxide. Thus, it can function as a fluorescence based nitric oxide sensor. It has been found that the present complex can be used to sense nanomolar quantities of nitric oxide in both methanol and pH 7.2 buffered-water medium.

  16. Aerogels of 1D Coordination Polymers: From a Non-Porous Metal-Organic Crystal Structure to a Highly Porous Material

    Directory of Open Access Journals (Sweden)

    Adrián Angulo-Ibáñez

    2016-01-01

    Full Text Available The processing of an originally non-porous 1D coordination polymer as monolithic gel, xerogel and aerogel is reported as an alternative method to obtain novel metal-organic porous materials, conceptually different to conventional crystalline porous coordination polymer (PCPs or metal-organic frameworks (MOFs. Although the work herein reported is focused upon a particular kind of coordination polymer ([M(μ-ox(4-apy2]n, M: Co(II, Ni(II, the results are of interest in the field of porous materials and of MOFs, as the employed synthetic approach implies that any coordination polymer could be processable as a mesoporous material. The polymerization conditions were fixed to obtain stiff gels at the synthesis stage. Gels were dried at ambient pressure and at supercritical conditions to render well shaped monolithic xerogels and aerogels, respectively. The monolithic shape of the synthesis product is another remarkable result, as it does not require a post-processing or the use of additives or binders. The aerogels of the 1D coordination polymers are featured by exhibiting high pore volumes and diameters ranging in the mesoporous/macroporous regions which endow to these materials the ability to deal with large-sized molecules. The aerogel monoliths present markedly low densities (0.082–0.311 g·cm−3, an aspect of interest for applications that persecute light materials.

  17. Mn(II,III) oxidation and MnO2 mineralization by an expressed bacterial multicopper oxidase

    Science.gov (United States)

    Butterfield, Cristina N.; Soldatova, Alexandra V.; Lee, Sung-Woo; Spiro, Thomas G.; Tebo, Bradley M.

    2013-01-01

    Reactive Mn(IV) oxide minerals are ubiquitous in the environment and control the bioavailability and distribution of many toxic and essential elements and organic compounds. Their formation is thought to be dependent on microbial enzymes, because spontaneous Mn(II) to Mn(IV) oxidation is slow. Several species of marine Bacillus spores oxidize Mn(II) on their exosporium, the outermost layer of the spore, encrusting them with Mn(IV) oxides. Molecular studies have identified the mnx (Mn oxidation) genes, including mnxG, encoding a putative multicopper oxidase (MCO), as responsible for this two-electron oxidation, a surprising finding because MCOs only catalyze single-electron transfer reactions. Characterization of the enzymatic mechanism has been hindered by the lack of purified protein. By purifying active protein from the mnxDEFG expression construct, we found that the resulting enzyme is a blue (absorption maximum 590 nm) complex containing MnxE, MnxF, and MnxG proteins. Further, by analyzing the Mn(II)- and (III)-oxidizing activity in the presence of a Mn(III) chelator, pyrophosphate, we found that the complex facilitates both electron transfers from Mn(II) to Mn(III) and from Mn(III) to Mn(IV). X-ray absorption spectroscopy of the Mn mineral product confirmed its similarity to Mn(IV) oxides generated by whole spores. Our results demonstrate that Mn oxidation from soluble Mn(II) to Mn(IV) oxides is a two-step reaction catalyzed by an MCO-containing complex. With the purification of active Mn oxidase, we will be able to uncover its mechanism, broadening our understanding of Mn mineral formation and the bioinorganic capabilities of MCOs. PMID:23818588

  18. Degradation of zinc oxide thin films in aqueous environment. Pt. II. Coated films

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, L. de; Mitton, D.B.; Monetta, T.; Bellucci, F. [Naples Univ. (Italy). Dept. of Materials and Production Engineering; Springer, J. [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Stuttgart (Germany)

    2001-12-01

    cn Part I of this research, the degradation mechanism of two different bare ZnO thin films was assessed. Degradation of the electrical properties of ZnO as well as changes in morphology were observed for both films. In the current paper, the degradation of zinc oxide thin films coated with protective acrylic paint is addressed during exposure to (i) an aqueous 3.5% NaCl solution at 85 C and (ii) a standard damp heat test at 85% R.H. and 85 C. Electrical and electrochemical techniques were employed to monitor zinc oxide degradation during exposure to the test environments. Electrochemical Impedance Spectroscopy was employed to investigate the delamination phenomena at the ZnO/coating interface and a simple equivalent circuit was developed to quantitatively measure the delamination ratio. The effect of different silane based adhesion promoters (glycidil-oxypropyl-trimethoxy-silane and aminopropyl-trimethoxy-silane) was also investigated. (orig.)

  19. Hybrid aerogels and bioactive aerogels under uniaxial compression: an in situ SAXS study

    Directory of Open Access Journals (Sweden)

    Esquivias, L.

    2010-12-01

    Full Text Available The complex structure of hybrid organic/inorganic aerogels is composed by an inorganic phase covalently bonded to an organic chain forming a copolymer. Conventional hybrid aerogels were studied as well as bioactive hybrid aerogels, that is, aerogels with a calcium active phase added. In this work, the relationship between mechanical response and nanostructure was studied, using a specifically designed sample-holder for in situ uniaxial compression obtaining at the same time the small-angle X-ray pattern from synchrotron radiation (SAXS. Structural elements can be described as a particulated silica core surrounded by the organic chains. These chains are compressed on the direction parallel to the load, and a relationship between macroscopic uniaxial compression and particle and pore deformations can be established.

    La compleja estructura de los aerogeles híbridos orgánico/inorgánicos está compuesta por una fase inorgánica de sílice, unida mediante enlaces covalentes a una red de cadenas orgánicas. Se han estudiado composites híbridos convencionales y bioactivos, esto es, con una fase activa de calcio añadida. En este trabajo se ha investigado la relación entre la respuesta mecánica y la nanoestructura, con ayuda de un portamuestras específicamente diseñado para el estudio in situ de muestras bajo compresión uniaxial, a la vez que se obtiene el espectro de rayos-X a bajo-ángulo de radiación sincrotrón (SAXS. Los elementos estructurales se pueden describir como núcleos particulados de sílice rodeados de las cadenas orgánicas. Estas, se comprimen en la dirección paralela a la carga pudiéndose establecer una relación entre la compresión uniaxial macroscópica y la deformación de las partículas y poros que forman la estructura.

  20. Structural information on the coordination compounds formed by manganese(II), cobalt(II), nickel(II), zinc(II), cadmium(II) and mercury(II) thiocyanates with 4-cyanopyridine N-oxide from their magnetic moments, electronic and infrared spectra

    Science.gov (United States)

    Ahuja, I. S.; Yadava, C. L.; Singh, Raghuvir

    1982-05-01

    Coordination compounds formed by the interaction of 4-cyanopyridine. N-oxide (4-CPO), a potentially bidentate ligand, with manganese(II), cobalt(II), nickel(II), zinc(II), cadmium(II) and rnercury(II) thiocyanates have been prepared and characterized from their elemental analyses, magnetic susceptibilities, electronic and infrared spectral studies down to 200 cm -1 in the solid state. The compounds isolated are: Mn(4-CPO) 2(NCS) 2, Co(4-CPO) 2(NCS) 2,Ni(4-CPO) 2(NCS) 2,Zn(4-CPO) 2(NCS) 2, Cd(4-CPO)(NCS) 2 and Hg(4-CPO) 2(SCN) 2. It is shown that 4-CPO acts as a terminal N-oxide oxygen bonded monodentate ligand in all the metal(II) thiocyanate complexes studied. Tentative stereochemistries of the complexes in the solid state are discussed. The ligand field parameters 10 Dq, B, β and λ calculated for the manganese(II), cobalt(II) and nickel(II) complexes are consistent with their proposed stereochemistries.

  1. Exchange interactions in a dinuclear manganese (II) complex with cyanopyridine-N-oxide bridging ligands

    Energy Technology Data Exchange (ETDEWEB)

    Markosyan, A.S. [Faculty of Physics, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Department of Applied Physics, Stanford University (United States); Gaidukova, I.Yu.; Ruchkin, A.V. [Faculty of Physics, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Anokhin, A.O. [Institute of Metal Physics, Ural Division of the Russian, Ekaterinburg (Russian Federation); Irkhin, V.Yu., E-mail: valentin.irkhin@imp.uran.ru [Institute of Metal Physics, Ural Division of the Russian, Ekaterinburg (Russian Federation); Ryazanov, M.V.; Kuz’mina, N.P. [Faculty of Chemistry, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Nikiforov, V.N. [Faculty of Physics, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation)

    2014-01-01

    The magnetic properties of dinuclear manganese(II) complex [Mn(hfa){sub 2}cpo]{sub 2} (where hfa is hexafluoroacetylacetonate anion and cpo is 4-cyanopyridine-N-oxide) are presented. The non-monotonous dependence of magnetic susceptibility is explained in terms of the hierarchy of exchange parameters by using exact diagonalization. The thermodynamic behavior of pure cpo and [Mn(hfa){sub 2}(cpo)]{sub 2} is simulated numerically by an extrapolation to spin S=5/2. The Mn–Mn exchange integral is evaluated.

  2. Monolithic three-dimensional electrochemical energy storage system on aerogel or nanotube scaffold

    Science.gov (United States)

    Farmer, Joseph C; Stadermann, Michael

    2013-11-12

    A monolithic three-dimensional electrochemical energy storage system is provided on an aerogel or nanotube scaffold. An anode, separator, cathode, and cathodic current collector are deposited on the aerogel or nanotube scaffold.

  3. Evaluation of supercritical CO2 dried cellulose aerogels as nano-biomaterials

    Science.gov (United States)

    Lee, Sinah; Kang, Kyu-Young; Jeong, Myung-Joon; Potthast, Antje; Liebner, Falk

    2017-10-01

    Cellulose is the renewable, biodegradable and abundant resource and is suggested as an alternative material to silica due to the high price and environmental load of silica. The first step for cellulose aerogel production is to dissolve cellulose, and hydrated calcium thiocyanate molten salt is one of the most effective solvents for preparing porous material. Cellulose aerogels were prepared from dissolved cellulose samples of different degree of polymerization (DP) and drying methods, and tested with shrinkage, density and mechanical strength. Supercritical CO2 dried cellulose aerogels shrank less compared to freeze-dried cellulose aerogels, whereas the densities were increased according to the DP increases in both cellulose aerogels. Furthermore, scanning electron microscope (SEM) images showed that the higher DP cellulose aerogels were more uniform with micro-porous structure. Regarding the mechanical strength of cellulose aerogels, supercritical CO2 dried cellulose aerogels with higher molecular weight were much more solid.

  4. Aerogel Cherenkov Counters of the KEDR Detector

    CERN Document Server

    Ovtin, I V; Barnyakov, M Y; Bobrovnikov, V S; Buzykaev, A R; Danilyuk, A F; Katcin, A A; Kononov, S A; Kravchenko, E A; Kuyanov, I A; Onuchin, A P; Rodiakin, V A

    2017-01-01

    The particle identification system of the KEDR detector is based on aerogel threshold Cherenkov counters called ASHIPH counters. The system consists of 160 counters arranged in two layers. An event reconstruction program for the ASHIPH system was developed. The position of each counter relative to the tracking system was determined using cosmic muons and Bhabha events. The geometric efficiency of the ASHIPH system was verified with Bhabha events. The efficiency of relativistic particle detection was measured with cosmic muons. A π/K separation of 4δ in the momentum range 0.95 −1.45 GeV/c was confirmed. A simulation program for the ASHIPH counters has been developed.

  5. Reinforced plastics and aerogels by nanocrystalline cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Leung, Alfred C. W.; Lam, Edmond; Chong, Jonathan; Hrapovic, Sabahudin; Luong, John H. T., E-mail: john.luong@cnrc-nrc.gc.ca [National Research Council Canada (Canada)

    2013-05-15

    Nanocrystalline cellulose (NCC), a rigid rod-like nanoscale material, can be produced from cellulosic biomass in powder, liquid, or gel forms by acid and chemical hydrolysis. Owing to its unique and exceptional physicochemical properties, the incorporation of a small amount of NCC into plastic enhances the mechanical strength of the latter by several orders of magnitudes. Carbohydrate-based NCC poses no serious environmental concerns, providing further impetus for the development and applications of this green and renewable biomaterial to fabricate lightweight and biodegradable composites and aerogels. Surface functionalization of NCC remains the main focus of NCC research to tailor its properties for dispersion in hydrophilic or hydrophobic media. It is of uttermost importance to develop tools and protocols for imaging of NCC in a complex matrix and quantify its reinforcement effect.

  6. Acclimation of a marine microbial consortium for efficient Mn(II) oxidation and manganese containing particle production

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Hao, E-mail: zhouhao@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Food and Environment, Dalian University of Technology, Panjin 124221 (China); Pan, Haixia [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Food and Environment, Dalian University of Technology, Panjin 124221 (China); Xu, Jianqiang [School of Life Science and Medicine, Dalian University of Technology, Panjin 124221 (China); Xu, Weiping; Liu, Lifen [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Food and Environment, Dalian University of Technology, Panjin 124221 (China)

    2016-03-05

    Highlights: • An efficient Mn(II) oxidation marine sediments microbial community was obtained. • High-throughput sequencing indicated new Mn(II) oxidation associated genus. • Na{sub 3}MnPO{sub 4}CO{sub 3} and MnCO{sub 3} were synthesized by the consortium. • Consortium exhibited Mn(II) oxidation performance over a range of harsh conditions. - Abstract: Sediment contamination with metals is a widespread concern in the marine environment. Manganese oxidizing bacteria (MOB) are extensively distributed in various environments, but a marine microbial community containing MOB is rarely reported. In this study, a consortium of marine metal-contaminated sediments was acclimated using Mn(II). The shift in community structure was determined through high-throughput sequencing. In addition, the consortium resisted several harsh conditions, such as toxic metals (1 mM Cu(II) and Fe(III)), and exhibited high Mn(II) oxidation capacities even the Mn(II) concentration was up to 5 mM. Meanwhile, biogenic Mn containing particles were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and N{sub 2} adsorption/desorption. Dye removal performance of the Mn containing particles was assayed using methylene blue, and 20.8 mg g{sup −1} adsorption capacity was obtained. Overall, this study revealed several new genera associated with Mn(II) oxidation and rare biogenic Na{sub 3}MnPO{sub 4}CO{sub 3.} Results suggested the complexity of natural microbe-mediated Mn transformation.

  7. Identification of Mn(II)-oxidizing bacteria from a low-pH contaminated former uranium mine.

    Science.gov (United States)

    Akob, Denise M; Bohu, Tsing; Beyer, Andrea; Schäffner, Franziska; Händel, Matthias; Johnson, Carol A; Merten, Dirk; Büchel, Georg; Totsche, Kai Uwe; Küsel, Kirsten

    2014-08-01

    Biological Mn oxidation is responsible for producing highly reactive and abundant Mn oxide phases in the environment that can mitigate metal contamination. However, little is known about Mn oxidation in low-pH environments, where metal contamination often is a problem as the result of mining activities. We isolated two Mn(II)-oxidizing bacteria (MOB) at pH 5.5 (Duganella isolate AB_14 and Albidiferax isolate TB-2) and nine strains at pH 7 from a former uranium mining site. Isolate TB-2 may contribute to Mn oxidation in the acidic Mn-rich subsoil, as a closely related clone represented 16% of the total community. All isolates oxidized Mn over a small pH range, and isolates from low-pH samples only oxidized Mn below pH 6. Two strains with different pH optima differed in their Fe requirements for Mn oxidation, suggesting that Mn oxidation by the strain found at neutral pH was linked to Fe oxidation. Isolates tolerated Ni, Cu, and Cd and produced Mn oxides with similarities to todorokite and birnessite, with the latter being present in subsurface layers where metal enrichment was associated with Mn oxides. This demonstrates that MOB can be involved in the formation of biogenic Mn oxides in both moderately acidic and neutral pH environments. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  8. Identification of Mn(II)-oxidizing bacteria from a low-pH contaminated former uranium mine

    Science.gov (United States)

    Akob, Denise M.; Bohu, Tsing; Beyer, Andrea; Schäffner, Franziska; Händel, Matthias; Johnson, Carol A.; Merten, Dirk; Büchel, Georg; Totsche, Kai Uwe; Küsel, Kirsten

    2014-01-01

    Biological Mn oxidation is responsible for producing highly reactive and abundant Mn oxide phases in the environment that can mitigate metal contamination. However, little is known about Mn oxidation in low-pH environments, where metal contamination often is a problem as the result of mining activities. We isolated two Mn(II)-oxidizing bacteria (MOB) at pH 5.5 (Duganella isolate AB_14 and Albidiferax isolate TB-2) and nine strains at pH 7 from a former uranium mining site. Isolate TB-2 may contribute to Mn oxidation in the acidic Mn-rich subsoil, as a closely related clone represented 16% of the total community. All isolates oxidized Mn over a small pH range, and isolates from low-pH samples only oxidized Mn below pH 6. Two strains with different pH optima differed in their Fe requirements for Mn oxidation, suggesting that Mn oxidation by the strain found at neutral pH was linked to Fe oxidation. Isolates tolerated Ni, Cu, and Cd and produced Mn oxides with similarities to todorokite and birnessite, with the latter being present in subsurface layers where metal enrichment was associated with Mn oxides. This demonstrates that MOB can be involved in the formation of biogenic Mn oxides in both moderately acidic and neutral pH environments.

  9. Sphaerotilus natans encrusted with nanoball-shaped Fe(III) oxide minerals formed by nitrate-reducing mixotrophic Fe(II) oxidation.

    Science.gov (United States)

    Park, Sunhwa; Kim, Dong-Hun; Lee, Ji-Hoon; Hur, Hor-Gil

    2014-10-01

    Ferrous iron has been known to function as an electron source for iron-oxidizing microorganisms in both anoxic and oxic environments. A diversity of bacteria has been known to oxidize both soluble and solid-phase Fe(II) forms coupled to the reduction of nitrate. Here, we show for the first time Fe(II) oxidation by Sphaerotilus natans strain DSM 6575(T) under mixotrophic condition. Sphaerotilus natans has been known to form a sheath structure enclosing long chains of rod-shaped cells, resulting in a thick biofilm formation under oxic conditions. Here, we also demonstrate that strain DSM 6575(T) grows mixotrophically with pyruvate, Fe(II) as electron donors and nitrate as an electron acceptor and single cells of strain DSM 6575(T) are dominant under anoxic conditions. Furthermore, strain DSM 6575(T) forms nanoball-shaped amorphous Fe(III) oxide minerals encrusting on the cell surfaces through the mixotrophic iron oxidation reaction under anoxic conditions. We propose that cell encrustation results from the indirect Fe(II) oxidation by biogenic nitrite during nitrate reduction and that causes the bacterial morphological change to individual rod-shaped single cells from filamentous sheath structures. This study extends the group of existing microorganisms capable of mixotrophic Fe(II) oxidation by a new strain, S. natans strain DSM 6575(T) , and could contribute to biogeochemical cycles of Fe and N in the environment. © 2014 The Authors. FEMS Microbiology Ecology published by John Wiley & Sons Ltd on behalf of Federation of European Microbiological Societies.

  10. Aerogel as a Sample Collector and Sample Mount for Transmission XRD Analysis

    Science.gov (United States)

    Bish, D. L.; Vaniman, D. T.; Chipera, S. J.; Yen, A. S.; Jones, S. M.

    2001-01-01

    Silica aerogel can be used for dust collection and in situ X-ray analysis. Aerogels can be less absorbing than Be, and it is feasible to obtain X-ray transmission factors >50% using typical aerogels together with a 100-micrometer Be backing foil. Additional information is contained in the original extended abstract.

  11. Study on the adsorption of Cu(II) by folic acid functionalized magnetic graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Cuicui [Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022 (China); School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Ge, Heyi, E-mail: geheyi@sina.com [Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022 (China); School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Zhao, Yueying [Shandong Xiaguang Industrial Co., Ltd., Jining 272000 (China); Liu, Shanshan; Zou, Yu; Zhang, Wenbo [Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022 (China); School of Material Science and Engineering, University of Jinan, Jinan 250022 (China)

    2017-02-01

    The folic acid functionalized magnetic graphene oxide (FA-mGO) as a new adsorbent has been synthesized in this work for the elimination of Cu(II) from waste water. The as-prepared FA-mGO was tested by SEM, TEM, particle size analyzer, FTIR, XRD, Roman spectrum, TGA and magnetic properties analyzer. Some factors, such as adsorbent dose, pH, contact time, initial concentration of adsorbate and temperature were explored. The results showed that the FA-mGO had the better adsorption performance than mGO. After 40 min, the adsorption equilibrium could be reached. Furthermore, the adsorption property obeyed the pseudo-second order kinetic model and the Temkin isotherms well. The maximum adsorption capacity was 283.29 mg/g for Cu(II) from Pseudo-second-order model at pH=5 and 318 K. The chelation action between FA and Cu(II) along with electrostatic incorporation between GO and Cu(II) determined the favourable adsorption property. Besides, thermodynamic studies results ∆G{sup 0}<0, ∆H{sup 0}>0, ∆S{sup 0}>0 suggested that the adsorption mechanism was an endothermic and spontaneous process essentially. Finally, desorption and reusability studies imply FA-mGO has an excellent reproducibility and is benefit to environmental protection and resource conservation. - Graphical abstract: Schematic illustration of preparing FA-mGO. - Highlights: • The FA-mGO was synthesized for the removal of Cu(II). • The chelation action and electrostatic incorporation determined the favourable adsorption property. • The adsorption property obeyed the pseudo-second-order and Temkin models well. • The adsorption mechanism was an endothermic and spontaneous process. • The FA-mGO has an excellent reproducibility.

  12. High turnover catalysis of water oxidation by Mn(II) complexes of monoanionic pentadentate ligands

    DEFF Research Database (Denmark)

    Seidler-Egdal, Rune Kirk; Nielsen, Anne; Bond, Andrew

    2011-01-01

    -pyridylmethyl)ethane-1,2-diamine (bcbpen(-)), show the presence of a mixture of closely related Mn(II) species, assigned to the mono, di-, tri- and poly-cationic complexes [Mn(II)(L)(H(2)O)](n)(n+), L = mcbpen(-) or bcbpen(-) with n = 1, 2, 3, etc. In solution, these complexes are reversibly oxidized by tert......:1 reaction of TBHP with [Mn] is rate determining and the resultant species is proposed to be the mononuclear, catalytically competent, [Mn(IV)(O)(mcbpen)](+). At very close m/z values [Mn(III)(OH)(mcbpen)](+), [Mn(2)(III/IV)(O)(2)(mcbpen)(2)](+) and [Mn(IV)(2)(O)(2)(mcbpen)(2)](2+) are detected by ESI MS......-butyl hydrogen peroxide (TBHP), (NH(4))(2)[Ce(NO(3))(6)], Ce(ClO(4))(4), oxone and [Ru(bipy)(3)](3+) to form metastable (t(½) = min to h) higher valent (hydr)oxide species, showing a collective maximum absorbance at 430 nm. The same species can be produced by [Ru(bipy)(3)](2+)-mediated photooxidization...

  13. High Turnover Catalysis of Water Oxidation by Mn(II) complexes of Monoanionic Pentadentate Ligands

    DEFF Research Database (Denmark)

    Seidler-Egdal, Rune Kirk; Nielsen, Anne; Bond, Andrew

    2011-01-01

    -pyridylmethyl)ethane-1,2-diamine (bcbpen−), show the presence of a mixture of closely related Mn(II) species, assigned to the mono, di-, tri- and poly-cationic complexes [MnII(L)(H2O)]nn+, L = mcbpen− or bcbpen− with n = 1, 2, 3, etc. In solution, these complexes are reversibly oxidized by tert-butyl hydrogen...... determining and the resultant species is proposed to be the mononuclear, catalytically competent, [MnIV(O)(mcbpen)]+. At very close m/z values [MnIII(OH)(mcbpen)]+, [Mn2III/IV(O)2(mcbpen)2]+ and [MnIV2(O)2(mcbpen)2]2+are detected by ESI MS and CE when the concentration of TBHP is comparable to or lower than...... peroxide (TBHP), (NH4)2[Ce(NO3)6], Ce(ClO4)4, oxone and [Ru(bipy)3]3+ to form metastable (t½ = min to h) higher valent (hydr)oxide species, showing a collective maximum absorbance at 430 nm. The same species can be produced by [Ru(bipy)3]2+-mediated photooxidization in the presence of an electron acceptor...

  14. Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

    Energy Technology Data Exchange (ETDEWEB)

    Song, Na [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Brookhaven National Lab. (BNL), Upton, NY (United States); Concepcion, Javier J. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Binstead, Robert A. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Rudd, Jennifer A. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Vannucci, Aaron K. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemistry and Biochemistry; Dares, Christopher J. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Coggins, Michael K. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Meyer, Thomas J. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry

    2015-04-06

    In aqueous solution above pH 2.4 with 4% (vol/vol) CH3CN, the complex [RuII(bda)(isoq)2] (bda is 2,2'-bipyridine-6,6'-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [RuII(CO2-bpy-CO2$-$)(isoq)2(NCCH3)], as shown by 1H and 13C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO43–, the calculated half-time for water oxidation is ~7 μs. In conclusion, the key to the rate accelerations with added bases is direct involvement of the buffer base in either atom–proton transfer (APT) or concerted electron–proton transfer (EPT) pathways.

  15. Optically Transparent Thermally Insulating Silica Aerogels for Solar Thermal Insulation.

    Science.gov (United States)

    Günay, A Alperen; Kim, Hannah; Nagarajan, Naveen; Lopez, Mateusz; Kantharaj, Rajath; Alsaati, Albraa; Marconnet, Amy; Lenert, Andrej; Miljkovic, Nenad

    2018-04-18

    Rooftop solar thermal collectors have the potential to meet residential heating demands if deployed efficiently at low solar irradiance (i.e., 1 sun). The efficiency of solar thermal collectors depends on their ability to absorb incoming solar energy and minimize thermal losses. Most techniques utilize a vacuum gap between the solar absorber and the surroundings to eliminate conduction and convection losses, in combination with surface coatings to minimize reradiation losses. Here, we present an alternative approach that operates at atmospheric pressure with simple, black, absorbing surfaces. Silica based aerogels coated on black surfaces have the potential to act as simple and inexpensive solar thermal collectors because of their high transmission to solar radiation and low transmission to thermal radiation. To demonstrate their heat-trapping properties, we fabricated tetramethyl orthosilicate-based silica aerogels. A hydrophilic aerogel with a thickness of 1 cm exhibited a solar-averaged transmission of 76% and thermally averaged transmission of ≈1% (at 100 °C). To minimize unwanted solar absorption by O-H groups, we functionalized the aerogel to be hydrophobic, resulting in a solar-averaged transmission of 88%. To provide a deeper understanding of the link between aerogel properties and overall efficiency, we developed a coupled radiative-conductive heat transfer model and used it to predict solar thermal performance. Instantaneous solar thermal efficiencies approaching 55% at 1 sun and 80 °C were predicted. This study sheds light on the applicability of silica aerogels on black coatings for solar thermal collectors and offers design priorities for next-generation solar thermal aerogels.

  16. Catalytic behaviors of Co{sup II} and Mn{sup II} compounds bearing α-Diimine ligands for oxidative polymerization or drying oils

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Gilvan E.S.; Nunes, Everton V.; Dantas, Roberta C.; Meneghetti, Mario R.; Meneghetti, Simoni M.P., E-mail: simoni.plentz@gmail.com [Universidade Federal de Alagoas (UFAL), Maceió, AL (Brazil). Grupo de Catálise e Reatividade Química; Simone, Carlos A. de [Universidade de Sao Paulo (USP), São Carlos, USP, SP (Brazil). Instituto de Física

    2018-05-01

    The oxidative polymerization of linseed oil was investigated comparing the classical catalysts cobalt(II) 2-ethylhexanoate and manganese(II) 2-ethylhexanoate and their derivatives modified by the presence of chelating nitrogen ligands, i.e., 2,2’-bipyridyl, 2-(acetyl-2,6-diisopropylphenylimine)- pyridine and [N-(2,6-diisopropylphenyl)imine]acenaphthoquinone. The suitable stoichiometries between the two precursor complexes with the three ligands were determined by UV-visible spectroscopy. All complexes were characterized by infrared spectroscopy, and one complex was characterized also by X-ray diffraction. The apparent kinetic constants of oxidative polymerization of linseed oil was determined, for each catalytic system, via the periodic measurements of the oil viscosity during the oxidation reaction. The results indicated that the modifications of the classical two complexes with the chelating nitrogen ligands improved the catalytic efficiency at least to the manganese complex. (author)

  17. Efficient removal of cobalt(II) and strontium(II) metals from water using ethylene diamine tetra-acetic acid functionalized graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Amer, Hany; Moustafa, Wafaa M. [Nuclar Fuel Cycle Department, Nuclear and Radiological Regulatory Authority (NRRA), Naser City, Cairo (Egypt); Farghali, Ahmed A.; El Rouby, Waleed M.A. [Materials Science and Nanotechnology Department, Faculty of Postgraduate Studies for Advanced Sciences (PASA), Beni-Suef University (Egypt); Khalil, Waleed F. [Nuclar Fuel Cycle Department, Nuclear and Radiological Regulatory Authority (NRRA), Naser City, Cairo (Egypt); Materials Science and Nanotechnology Department, Faculty of Postgraduate Studies for Advanced Sciences (PASA), Beni-Suef University (Egypt)

    2017-12-04

    Graphene oxide (GO) with high specific surface area was prepared and functionalized with ethylene diamine tetra-acetic acid (EDTA). The as-prepared GO and the functionalized one (GO-EDTA) were characterized using high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Raman spectroscopy. The as-prepared and EDTA functionalized GO were applied as adsorbent to remove strontium(II) and cobalt(II) from water. The results indicated that the prepared materials are efficient adsorbents for strontium(II) and cobalt(II) removal. The adsorption of Co{sup II} and Sr{sup II} under effects of contact time, temperature, and pH was investigated It is concluded that the maximum adsorption capacities of GO for Co{sup II} and Sr{sup II} were about 168 and 140 mg.g{sup -1}, whereas of GO-EDTA the values were about 197 and 158 mg.g{sup -1}, respectively. It is indicated that pH 6 and temperature 40 C are the best condition for Co{sup II} and Sr{sup II} removal from water. The application of Langmuir and Freundlich isotherms indicated that Langmuir isotherm is best fit for Co{sup II} and Sr{sup II} equilibrium adsorption. Adsorption kinetics were studied by applying pseudo first-order, pseudo second-order, and intraparticle diffusion models on the experimental data. The results proved that pseudo second-order model is the best represented adsorption kinetics. Appling the intraparticle diffusion regressions on the experimental data indicated that intraparticle diffusion involved in adsorption process, which was not the only rate-controlling step. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Nano-structured Ni(II)-curcumin modified glassy carbon electrode for electrocatalytic oxidation of fructose

    International Nuclear Information System (INIS)

    Elahi, M. Yousef; Mousavi, M.F.; Ghasemi, S.

    2008-01-01

    A nano-structured Ni(II)-curcumin (curcumin: 1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) film is electrodeposited on a glassy carbon electrode in alkaline solution. The morphology of polyNi(II)-curcumin (NC) was investigated by scanning electron microscopy (SEM). The SEM results show NC has a nano-globular structure in the range 20-50 nm. Using cyclic voltammetry, linear sweep voltammetry, chronoamperometry, steady-state polarization measurements and electrochemical impedance spectroscopy (EIS) showed that the nano-structure NC film acts as an efficient material for the electrocatalytic oxidation of fructose. According to the voltammetric studies, the increase in the anodic peak current and subsequent decrease in the corresponding cathodic current, fructose was oxidized on the electrode surface via an electrocatalytic mechanism. The EIS results show that the charge-transfer resistance has as a function of fructose concentration, time interval and applied potential. The increase in the fructose concentration and time interval in fructose solution results in enhanced charge transfer resistance in Nyquist plots. The EIS results indicate that fructose electrooxidation at various potentials shows different impedance behaviors. At lower potentials, a semicircle is observed in the first quadrant of impedance plot. With further increase of the potential, a transition of the semicircle from the first to the second quadrant occurs. Also, the results obtained show that the rate of fructose electrooxidation depends on concentration of OH - . Electron transfer coefficient, diffusion coefficient and rate constant of the electrocatalytic oxidation reaction are obtained. The modified electrode was used as a sensor for determination of fructose with a good dynamic range and a low detection limit

  19. Oxidation behavior analysis of cladding during severe accidents with combined codes for Qinshan Phase II Nuclear Power Plant

    International Nuclear Information System (INIS)

    Shi, Xingwei; Cao, Xinrong; Liu, Zhengzhi

    2013-01-01

    Highlights: • A new verified oxidation model of cladding has been added in Severe Accident Program (SAP). • A coupled analysis method utilizing RELAP5 and SAP codes has been developed and applied to analyze a SA caused by LBLOCA. • Analysis of cladding oxidation under a SA for Qinshan Phase II Nuclear Power Plant (QSP-II NPP) has been performed by SAP. • Estimation of the production of hydrogen has been achieved by coupled codes. - Abstract: Core behavior at a high temperature is extremely complicated during transition from Design Basic Accident (DBA) to the severe accident (SA) in Light Water Reactors (LWRs). The progression of core damage is strongly affected by the behavior of fuel cladding (oxidation, embrittlement and burst). A Severe Accident Program (SAP) is developed to simulate the process of fuel cladding oxidation, rupture and relocation of core debris based on the oxidation models of cladding, candling of melted material and mechanical slumping of core components. Relying on the thermal–hydraulic boundary parameters calculated by RELAP5 code, analysis of a SA caused by the large break loss-of-coolant accident (LBLOCA) without mitigating measures for Qinshan Phase II Nuclear Power Plant (QSP-II NPP) was performed by SAP for finding the key sequences of accidents, estimating the amount of hydrogen generation and oxidation behavior of the cladding

  20. Copper(II) oxide solubility behavior in aqueous sodium phosphate solutions at elevated temperatures

    International Nuclear Information System (INIS)

    Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

    1990-02-01

    A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of copper(II) oxide (CuO) in aqueous sodium phosphate solutions at temperatures between 292 and 535 K. Copper solubilities are observed to increase continuously with temperature and phosphate concentration. The measured solubility is examined via a Cu(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reactions are obtained from a least- squares analysis of the data. Altogether, thermochemical properties are established for five anionic complexes: Cu(OH) 3 - , Cu(OH) 4 = , Cu(OH) 2 (HPO 4 ) = , Cu(OH) 3 (H 2 PO 4 ) = , and Cu(OH) 2 (PO 4 ) ≡ . Precise thermochemical parameters are also derived for the Cu(OH) + hydroxocomplex based on CuO solubility behavior previously observed in pure water (*) at elevated temperatures. The relative ease of Cu(II) ion hydrolysis is such that Cu(OH) 3 - species become the preferred hydroxocomplex for pH ≥ 9.4. 20 refs., 8 figs., 6 tabs

  1. Infertility and recurrent miscarriage with complex II deficiency-dependent mitochondrial oxidative stress in animal models.

    Science.gov (United States)

    Ishii, Takamasa; Yasuda, Kayo; Miyazawa, Masaki; Mitsushita, Junji; Johnson, Thomas E; Hartman, Phil S; Ishii, Naoaki

    2016-04-01

    Oxidative stress is associated with some forms of both male and female infertility. However, there is insufficient knowledge of the influence of oxidative stress on the maintenance of a viable pregnancy, including pregnancy complications and fetal development. There are a number of animal models for understanding age-dependent decrease of reproductive ability and diabetic embryopathy, especially abnormal spermatogenesis, oogenesis and embryogenesis with mitochondrial dysfunctions. Several important processes occur in mitochondria, including ATP synthesis, calcium ion storage, induction of apoptosis and production of reactive oxygen species (ROS). These events have different effects on the several aspects of reproductive function. Tet-mev-1 conditional transgenic mice, developed after studies with the mev-1 mutant of the nematode C. elegans, offer the ability to carefully regulate expression of doxycycline-induced mutated SDHC(V69E) levels and hence modulate endogenous oxidative stress. The mev-1 models have served to illuminate the effects of complex II deficiency-dependent mitochondrial ROS production, although interestingly they maintain normal mitochondrial and intracellular ATP levels. In this review, the reproductive dysfunctions are presented focusing on fertility potentials in each gamete, early embryogenesis, maternal conditions with placental function and neonatal development. Copyright © 2016. Published by Elsevier Ireland Ltd.

  2. Production of Nitrous Oxide from Nitrite in Stable Type II Methanotrophic Enrichments.

    Science.gov (United States)

    Myung, Jaewook; Wang, Zhiyue; Yuan, Tong; Zhang, Ping; Van Nostrand, Joy D; Zhou, Jizhong; Criddle, Craig S

    2015-09-15

    The coupled aerobic-anoxic nitrous decomposition operation is a new process for wastewater treatment that removes nitrogen from wastewater and recovers energy from the nitrogen in three steps: (1) NH4(+) oxidation to NO2(-), (2) NO2(-) reduction to N2O, and (3) N2O conversion to N2 with energy production. Here, we demonstrate that type II methanotrophic enrichments can mediate step two by coupling oxidation of poly(3-hydroxybutyrate) (P3HB) to NO2(-) reduction. Enrichments grown with NH4(+) and NO2(-) were subject to alternating 48-h aerobic and anoxic periods, in which CH4 and NO2(-) were added together in a "coupled" mode of operation or separately in a "decoupled mode". Community structure was stable in both modes and dominated by Methylocystis. In the coupled mode, production of P3HB and N2O was low. In the decoupled mode, significant P3HB was produced, and oxidation of P3HB drove reduction of NO2(-) to N2O with ∼ 70% conversion for >30 cycles (120 d). In batch tests of wasted cells from the decoupled mode, N2O production rates increased at low O2 or high NO2(-) levels. The results are significant for the development of engineered processes that remove nitrogen from wastewater and for understanding of conditions that favor environmental production of N2O.

  3. Tailored lithium storage performance of graphene aerogel anodes with controlled surface defects for lithium-ion batteries

    International Nuclear Information System (INIS)

    Shan, Hui; Xiong, Dongbin; Li, Xifei; Sun, Yipeng; Yan, Bo; Li, Dejun; Lawes, Stephen; Cui, Yanhua; Sun, Xueliang

    2016-01-01

    Graphical abstract: - Highlights: • The graphene aerogel (GA) with controllable surface defects was synthesized. • The graphene aerogel anodes showed high specific capacity and excellent cyclability. • Surface defects on the GA significantly function for lithium storage. • This study can extend the application of the graphene anodes for LIBs. - Abstract: Three dimensional self-assembled graphene aerogel (GA) anode materials with some surface defects have been successfully generated through a facile hydrothermal procedure using graphene oxide as precursor. The morphologies and textural properties of as-obtained GA were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman and other spectroscopy techniques. The surface defects and electrical conductivities of GA can be controlled by adjusting the hydrothermal reaction time. The results indicate that GA with a reaction time of 6 h exhibits extremely high reversible capacity (1430 mAh g"−"1 at the current density of 100 mA g"−"1) and superior rate capability (587 mAh g"−"1 at 800 mA g"−"1) with excellent cycling stability (maintaining a reversible capacity of 960 mAh g"−"1 at 100 mA g"−"1 after 100 cycles). It is demonstrated that the 3D porous network with increased defect density, as well as the considerable electrical conductivity, results in the excellent electrochemical performance of the as-made GA anodes in lithium-ion batteries.

  4. Diffusion of gases in metal containing carbon aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Marques, L.M.; Conceicao, F.L.; Carrott, M.M.L. Ribeiro; Carrott, P.J.M. [Evora Univ. (Portugal). Centro de Quimica de Evora

    2011-02-15

    Carbon aerogels containing Fe, Ni, Cu or no metal were prepared by carbonisation of polymer aerogels synthesised from 2,4-dihydroxybenzoic acid and formaldehyde and modified by CVD of benzene. Uptakes and diffusion coefficients of CO{sub 2}, CH{sub 4}, N{sub 2} and O{sub 2} were measured and the results compared with those obtained using a commercial carbon molecular sieve. The results indicated that the diffusion of light gas molecules in carbon aerogels cannot be interpreted solely on the basis of micropore diffusion, but that the very high mesopore volumes of the aerogel monoliths exert a strong influence on the kinetics of diffusion in these materials. The mesoporosity is decreased when the % solids used during synthesis of the polymer precursor increases and this resulted in kinetic behaviour which was more similar to that predicted by Fickian or LDF models. Increasing % solids was also accompanied by generally slower diffusion rates and generally lower uptakes. The single gas uptakes and diffusion coefficients could be altered by varying the % solids used during synthesis of the polymer precursor, by introducing different metals into the polymer hydrogel by ion exchange, or by CVD of benzene on the carbon aerogel. (author)

  5. Efficiently dense hierarchical graphene based aerogel electrode for supercapacitors

    Science.gov (United States)

    Wang, Xin; Lu, Chengxing; Peng, Huifen; Zhang, Xin; Wang, Zhenkun; Wang, Gongkai

    2016-08-01

    Boosting gravimetric and volumetric capacitances simultaneously at a high rate is still a discrepancy in development of graphene based supercapacitors. We report the preparation of dense hierarchical graphene/activated carbon composite aerogels via a reduction induced self-assembly process coupled with a drying post treatment. The compact and porous structures of composite aerogels could be maintained. The drying post treatment has significant effects on increasing the packing density of aerogels. The introduced activated carbons play the key roles of spacers and bridges, mitigating the restacking of adjacent graphene nanosheets and connecting lateral and vertical graphene nanosheets, respectively. The optimized aerogel with a packing density of 0.67 g cm-3 could deliver maximum gravimetric and volumetric capacitances of 128.2 F g-1 and 85.9 F cm-3, respectively, at a current density of 1 A g-1 in aqueous electrolyte, showing no apparent degradation to the specific capacitance at a current density of 10 A g-1 after 20000 cycles. The corresponding gravimetric and volumetric capacitances of 116.6 F g-1 and 78.1 cm-3 with an acceptable cyclic stability are also achieved in ionic liquid electrolyte. The results show a feasible strategy of designing dense hierarchical graphene based aerogels for supercapacitors.

  6. Diffusion of gases in metal containing carbon aerogels

    International Nuclear Information System (INIS)

    Marques, L.M.; Conceicao, F.L.; Carrott, M.M.L. Ribeiro; Carrott, P.J.M.

    2011-01-01

    Carbon aerogels containing Fe, Ni, Cu or no metal were prepared by carbonisation of polymer aerogels synthesised from 2,4-dihydroxybenzoic acid and formaldehyde and modified by CVD of benzene. Uptakes and diffusion coefficients of CO 2 , CH 4 , N 2 and O 2 were measured and the results compared with those obtained using a commercial carbon molecular sieve. The results indicated that the diffusion of light gas molecules in carbon aerogels cannot be interpreted solely on the basis of micropore diffusion, but that the very high mesopore volumes of the aerogel monoliths exert a strong influence on the kinetics of diffusion in these materials. The mesoporosity is decreased when the % solids used during synthesis of the polymer precursor increases and this resulted in kinetic behaviour which was more similar to that predicted by Fickian or LDF models. Increasing % solids was also accompanied by generally slower diffusion rates and generally lower uptakes. The single gas uptakes and diffusion coefficients could be altered by varying the % solids used during synthesis of the polymer precursor, by introducing different metals into the polymer hydrogel by ion exchange, or by CVD of benzene on the carbon aerogel. (author)

  7. Modeling silica aerogel optical performance by determining its radiative properties

    Directory of Open Access Journals (Sweden)

    Lin Zhao

    2016-02-01

    Full Text Available Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM. Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation. To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE. The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel’s microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain.

  8. Van der Waal Interactions in Ultrafine Nanocellulose Aerogels

    Science.gov (United States)

    Fritch, Byron; Bradley, Derek; Kidd, Tim

    Nanocellulose aerogels have shown an ability to be used in many different applications ranging from oil sponges to conductive materials to possibly a low calorie food substitute. Not much is known about the structural and physical property changes that occur when the composition of the aerogel changes. We studied what properties change when the aerogel amounts change, as well as how sticky the aerogels are and how strong they are. The higher concentrations appeared to have more plate-like structures while the lower concentrations had a more fibrous material. These fibers in the low concentrations had a smaller diameter than a human hair. Only the low concentration aerogels were able to stick to a glass surface in the adhesion test, but were able to support a mass much larger than their own. These low concentrations also would stick to your finger when lightly touched. Preliminary tests show that a concentration that is not too low, but not too high, is best for tensile strength. All concentrations were able to hold many times their own mass. Cellulose should be studied more because it is a renewable material and is easily accessed. Nanocellulose is also not environmentally dangerous allowing it to be used in applications involving humans and the environment like noted above. National Science Foundation Grant DMR-1410496.

  9. Structure/Function Analysis of Cotton-Based Peptide-Cellulose Conjugates: Spatiotemporal/Kinetic Assessment of Protease Aerogels Compared to Nanocrystalline and Paper Cellulose

    Directory of Open Access Journals (Sweden)

    J. Vincent Edwards

    2018-03-01

    Full Text Available Nanocellulose has high specific surface area, hydration properties, and ease of derivatization to prepare protease sensors. A Human Neutrophil Elastase sensor designed with a nanocellulose aerogel transducer surface derived from cotton is compared with cotton filter paper, and nanocrystalline cellulose versions of the sensor. X-ray crystallography was employed along with Michaelis–Menten enzyme kinetics, and circular dichroism to contrast the structure/function relations of the peptide-cellulose conjugate conformation to enzyme/substrate binding and turnover rates. The nanocellulosic aerogel was found to have a cellulose II structure. The spatiotemporal relation of crystallite surface to peptide-cellulose conformation is discussed in light of observed enzyme kinetics. A higher substrate binding affinity (Km of elastase was observed with the nanocellulose aerogel and nanocrystalline peptide-cellulose conjugates than with the solution-based elastase substrate. An increased Km observed for the nanocellulosic aerogel sensor yields a higher enzyme efficiency (kcat/Km, attributable to binding of the serine protease to the negatively charged cellulose surface. The effect of crystallite size and β-turn peptide conformation are related to the peptide-cellulose kinetics. Models demonstrating the orientation of cellulose to peptide O6-hydroxymethyl rotamers of the conjugates at the surface of the cellulose crystal suggest the relative accessibility of the peptide-cellulose conjugates for enzyme active site binding.

  10. Structure/Function Analysis of Cotton-Based Peptide-Cellulose Conjugates: Spatiotemporal/Kinetic Assessment of Protease Aerogels Compared to Nanocrystalline and Paper Cellulose

    Science.gov (United States)

    Edwards, J. Vincent; Fontenot, Krystal; Liebner, Falk; Pircher, Nicole Doyle nee; French, Alfred D.; Condon, Brian D.

    2018-01-01

    Nanocellulose has high specific surface area, hydration properties, and ease of derivatization to prepare protease sensors. A Human Neutrophil Elastase sensor designed with a nanocellulose aerogel transducer surface derived from cotton is compared with cotton filter paper, and nanocrystalline cellulose versions of the sensor. X-ray crystallography was employed along with Michaelis–Menten enzyme kinetics, and circular dichroism to contrast the structure/function relations of the peptide-cellulose conjugate conformation to enzyme/substrate binding and turnover rates. The nanocellulosic aerogel was found to have a cellulose II structure. The spatiotemporal relation of crystallite surface to peptide-cellulose conformation is discussed in light of observed enzyme kinetics. A higher substrate binding affinity (Km) of elastase was observed with the nanocellulose aerogel and nanocrystalline peptide-cellulose conjugates than with the solution-based elastase substrate. An increased Km observed for the nanocellulosic aerogel sensor yields a higher enzyme efficiency (kcat/Km), attributable to binding of the serine protease to the negatively charged cellulose surface. The effect of crystallite size and β-turn peptide conformation are related to the peptide-cellulose kinetics. Models demonstrating the orientation of cellulose to peptide O6-hydroxymethyl rotamers of the conjugates at the surface of the cellulose crystal suggest the relative accessibility of the peptide-cellulose conjugates for enzyme active site binding. PMID:29534033

  11. Coherent-Interface-Assembled Ag2O-Anchored Nanofibrillated Cellulose Porous Aerogels for Radioactive Iodine Capture.

    Science.gov (United States)

    Lu, Yun; Liu, Hongwei; Gao, Runan; Xiao, Shaoliang; Zhang, Ming; Yin, Yafang; Wang, Siqun; Li, Jian; Yang, Dongjiang

    2016-10-26

    Nanofibrillated cellulose (NFC) has received increasing attention in science and technology because of not only the availability of large amounts of cellulose in nature but also its unique structural and physical features. These high-aspect-ratio nanofibers have potential applications in water remediation and as a reinforcing scaffold in composites, coatings, and porous materials because of their fascinating properties. In this work, highly porous NFC aerogels were prepared based on tert-butanol freeze-drying of ultrasonically isolated bamboo NFC with 20-80 nm diameters. Then nonagglomerated 2-20-nm-diameter silver oxide (Ag 2 O) nanoparticles (NPs) were grown firmly onto the NFC scaffold with a high loading content of ∼500 wt % to fabricate Ag 2 O@NFC organic-inorganic composite aerogels (Ag 2 O@NFC). For the first time, the coherent interface and interaction mechanism between the cellulose I β nanofiber and Ag 2 O NPs are explored by high-resolution transmission electron microscopy and 3D electron tomography. Specifically, a strong hydrogen between Ag 2 O and NFC makes them grow together firmly along a coherent interface, where good lattice matching between specific crystal planes of Ag 2 O and NFC results in very small interfacial straining. The resulting Ag 2 O@NFC aerogels take full advantage of the properties of the 3D organic aerogel framework and inorganic NPs, such as large surface area, interconnected porous structures, and supreme mechanical properties. They open up a wide horizon for functional practical usage, for example, as a flexible superefficient adsorbent to capture I - ions from contaminated water and trap I 2 vapor for safe disposal, as presented in this work. The viable binding mode between many types of inorganic NPs and organic NFC established here highlights new ways to investigate cellulose-based functional nanocomposites.

  12. Comparative Analysis of Secretome Profiles of Manganese(II-Oxidizing Ascomycete Fungi.

    Directory of Open Access Journals (Sweden)

    Carolyn A Zeiner

    Full Text Available Fungal secretomes contain a wide range of hydrolytic and oxidative enzymes, including cellulases, hemicellulases, pectinases, and lignin-degrading accessory enzymes, that synergistically drive litter decomposition in the environment. While secretome studies of model organisms such as Phanerochaete chrysosporium and Aspergillus species have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or conducted side-by-side comparisons of diverse species. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of LC-MS/MS, genomic, and bioinformatic analyses to characterize and compare the protein composition of the secretomes of four recently isolated, cosmopolitan, Mn(II-oxidizing Ascomycetes (Alternaria alternata SRC1lrK2f, Stagonospora sp. SRC1lsM3a, Pyrenochaeta sp. DS3sAY3a, and Paraconiothyrium sporulosum AP3s5-JAC2a. We demonstrate that the organisms produce a rich yet functionally similar suite of extracellular enzymes, with species-specific differences in secretome composition arising from unique amino acid sequences rather than overall protein function. Furthermore, we identify not only a wide range of carbohydrate-active enzymes that can directly oxidize recalcitrant carbon, but also an impressive suite of redox-active accessory enzymes that suggests a role for Fenton-based hydroxyl radical formation in indirect, non-specific lignocellulose attack. Our findings highlight the diverse oxidative capacity of these environmental isolates and enhance our understanding of the role of filamentous Ascomycetes in carbon turnover in the environment.

  13. Comparative Analysis of Secretome Profiles of Manganese(II)-Oxidizing Ascomycete Fungi

    Energy Technology Data Exchange (ETDEWEB)

    Zeiner, Carolyn A.; Purvine, Samuel O.; Zink, Erika M.; Paša-Tolić, Ljiljana; Chaput, Dominique L.; Haridas, Sajeet; Wu, Si; LaButti, Kurt; Grigoriev, Igor V.; Henrissat, Bernard; Santelli, Cara M.; Hansel, Colleen M.; Pöggeler, Stefanie

    2016-07-19

    Fungal secretomes contain a wide range of hydrolytic and oxidative enzymes, including cellulases, hemicellulases, pectinases, and lignin-degrading accessory enzymes, that synergistically drive litter decomposition in the environment. While secretome studies of model organisms such as Phanerochaete chrysosporium and Aspergillus species have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or conducted side-by-side comparisons of diverse species. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of LC-MS/MS, genomic, and bioinformatic analyses to characterize and compare the protein composition of the secretomes of four recently isolated, cosmopolitan, Mn(II)-oxidizing Ascomycetes (Alternaria alternata SRC1lrK2f, Stagonospora sp. SRC1lsM3a, Pyrenochaeta sp. DS3sAY3a, and Paraconiothyrium sporulosum AP3s5-JAC2a). We demonstrate that the organisms produce a rich yet functionally similar suite of extracellular enzymes, with species-specific differences in secretome composition arising from unique amino acid sequences rather than overall protein function. Furthermore, we identify not only a wide range of carbohydrate-active enzymes that can directly oxidize recalcitrant carbon, but also an impressive suite of redox-active accessory enzymes that suggests a role for Fenton-based hydroxyl radical formation in indirect, non-specific lignocellulose attack. Our findings highlight the diverse oxidative capacity of these environmental isolates and enhance our understanding of the role of filamentous Ascomycetes in carbon turnover in the environment.

  14. Measurements of scattering, transmittance/reflectance, IR-transmittance and thermal conductivity of small aerogel samples

    DEFF Research Database (Denmark)

    Duer, Karsten; Svendsen, Sv Aa Højgaard

    1997-01-01

    By providing at the same time thermal insulation and transparency the silica aerogel is a very attractive material for the purpose of improving the thermal performance of windows. Nevertheless a lot of problems have to be solved on the way from concept to the developed product. The B1 Aerogels...... project deals with some of these problems.This report summarizes the work that has been carried out on the subject of characterizing the optical and thermal performance of different types of aerogels and aerogel-like materials for the purpose of using aerogel in clear glazings.All measurements presented...

  15. Simultaneous removal of Cd(II) and Sb(V) by Fe–Mn binary oxide: Positive effects of Cd(II) on Sb(V) adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ruiping [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Liu, Feng [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Hu, Chengzhi, E-mail: czhu@rcees.ac.cn [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); He, Zan [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Huijuan; Qu, Jiuhui [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China)

    2015-12-30

    Highlights: • Fe–Mn binary oxide achieves the simultaneous removal of Cd(II) and Sb(V). • Cd(II) at above 0.25 mmol/L improves Sb(V) adsorption onto FMBO. • Cd(II) improves more significant Sb(V) adsorption than Ca{sup 2+} and Mn{sup 2+}. • Sb(V) adsorption decreases whereas Cd(II) adsorption increases with elevated pH. • The increased ζ-potential and Cd(II)–Sb(V) precipitation favors Sb(V) adsorption. - Abstract: The coexistence of cadmium ion (Cd(II)) and antimonate (Sb(V)) creates the need for their simultaneous removal. This study aims to investigate the effects of positively-charged Cd(II) on the removal of negative Sb(V) ions by Fe–Mn binary oxide (FMBO) and associated mechanisms. The maximum Sb(V) adsorption density (Q{sub max,Sb(V)}) increased from 1.02 to 1.32 and 2.01 mmol/g in the presence of Cd(II) at 0.25 and 0.50 mmol/L. Cd{sup 2+} exhibited a more significant positive effect than both calcium ion (Ca{sup 2+}) and manganese ion (Mn{sup 2+}). Cd{sup 2+} showed higher affinity towards FMBO and increased its ζ-potential more significantly compared to Ca{sup 2+} and Mn{sup 2+}. The simultaneous adsorption of Sb(V) and Cd(II) onto FMBO can be achieved over a wide initial pH (pH{sub i}) range from 2 to 9, and Q{sub Sb(V)} decreases whereas Q{sub Cd(II)} increases with elevated pH{sub i}. Their combined values, as expressed by Q{sub Sb(V)+Cd(II)}, amount to about 2 mmol/g and vary slightly in the pH{sub i} range 4–9. FTIR and XPS spectra indicate the significant synergistic effect of Cd(II) on Sb(V) adsorption onto FMBO, and that little chemical valence transformation occurs. These results may be valuable for the treatment of wastewater with coexisting heavy metals such as Cd(II) and Sb(V).

  16. Advanced oxidation removal of hypophosphite by O3/H2O2 combined with sequential Fe(II) catalytic process.

    Science.gov (United States)

    Zhao, Zilong; Dong, Wenyi; Wang, Hongjie; Chen, Guanhan; Wang, Wei; Liu, Zekun; Gao, Yaguang; Zhou, Beili

    2017-08-01

    Elimination of hypophosphite (HP) was studied as an example of nickel plating effluents treatment by O 3 /H 2 O 2 and sequential Fe(II) catalytic oxidation process. Performance assessment performed with artificial HP solution by varying initial pH and employing various oxidation processes clearly showed that the O 3 /H 2 O 2 ─Fe(II) two-step oxidation process possessed the highest removal efficiency when operating under the same conditions. The effects of O 3 dosing, H 2 O 2 concentration, Fe(II) addition and Fe(II) feeding time on the removal efficiency of HP were further evaluated in terms of apparent kinetic rate constant. Under improved conditions (initial HP concentration of 50 mg L -1 , 75 mg L -1 O 3 , 1 mL L -1 H 2 O 2 , 150 mg L -1 Fe(II) and pH 7.0), standard discharge (<0.5 mg L -1 in China) could be achieved, and the Fe(II) feeding time was found to be the limiting factor for the evolution of apparent kinetic rate constant in the second stage. Characterization studies showed that neutralization process after oxidation treatment favored the improvement of phosphorus removal due to the formation of more metal hydroxides. Moreover, as a comparison with lab-scale Fenton approach, the O 3 /H 2 O 2 ─Fe(II) oxidation process had more competitive advantages with respect to applicable pH range, removal efficiency, sludge production as well as economic costs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Preparation of sponge-reinforced silica aerogels from tetraethoxysilane and methyltrimethoxysilane for oil/water separation

    Science.gov (United States)

    Li, Ming; Jiang, Hongyi; Xu, Dong

    2018-04-01

    Polyurethane sponge-reinforced silica aerogels based on tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS) were fabricated by a facile method through sol-gel reaction followed by ambient pressure drying. In sponge-reinforced silica aerogels, nanoporous aerogel aggregates fill in the pores of polyurethane sponge. The sponge-reinforced aerogels are hydrophobic and oleophilic and show extremely high absorption for machine oil (10.6 g g‑1 for TEOS-based aerogel and 9.2 g g‑1 for MTMS-based aerogel). In addition, the sponge-reinforced aerogel composites exhibit notable improvements with regards to mechanical properties. The compressive strength was enhanced obviously up to about 349 KPa for TEOS-based aerogel and 60 KPa for MTMS-based aerogel. Specially, sponge-reinforced silica aerogels based on MTMS drastically shrank upon loading and then recovered to the original size when unloaded. The property differences of the sponge-reinforced silica aerogels caused by the two precursors were discussed in terms of morphologies, pore size distributions and chemical structure.

  18. Preparation, Characterization, and Cationic Functionalization of Cellulose-Based Aerogels for Wastewater Clarification

    Directory of Open Access Journals (Sweden)

    Yang Hu

    2016-01-01

    Full Text Available Aerogels are a series of materials with porous structure and light weight which can be applied to many industrial divisions as insulators, sensors, absorbents, and cushions. In this study, cellulose-based aerogels (aerocelluloses were prepared from cellulosic material (microcrystalline cellulose in sodium hydroxide/water solvent system followed by supercritical drying operation. The average specific surface area of aerocelluloses was 124 m2/g. The nitrogen gas (N2 adsorption/desorption isotherms revealed type H1 hysteresis loops for aerocelluloses, suggesting that aerocelluloses may possess a porous structure with cylindrically shaped pores open on both ends. FTIR and XRD analyses showed that the crystallinity of aerocelluloses was significantly decreased as compared to microcrystalline cellulose and that aerocelluloses exhibited a crystalline structure of cellulose II as compared to microcrystalline cellulose (cellulose I. To perform cationic functionalization, a cationic agent, (3-chloro-2-hydroxypropyl trimethylammonium chloride, was used to introduce positively charged sites on aerocelluloses. The cationized aerocelluloses exhibited a strong ability to remove anionic dyes from wastewater. Highly porous and low cost aerocelluloses prepared in this study would be also promising as a fast absorbent for environmental pollutants.

  19. Self-assembled hierarchical graphene/polyaniline hybrid aerogels for electrochemical capacitive energy storage

    International Nuclear Information System (INIS)

    Yang, Fan; Xu, Maowen; Bao, Shu-Juan; Wei, Hua; Chai, Hui

    2014-01-01

    In this work, polyaniline nanowires (PANI-NWs) act as spacers, incorporated with graphene oxide and self-assembled into graphene/PANI hybrid aerogels through a facile hydrothermal route. The as-synthesized samples have been characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), contact angle measurement, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) for their microstructure, morphology and relative affinities toward water. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements have been used to study the effects of composition, microstructure and morphology of the samples on their capacitive performance. The experimental results indicate that the PANI can effectively tailor the microstructures and electrochemical performances of the products. The as-prepared materials with an appropriate proportion of PANI nanowires can efficiently prevent the adjacent graphene sheets from aggregation and provide fast ionic channels for electrochemical energy storage. A specific capacitance of 520.3 F g −1 has been achieved from graphene/PANI hybrid aerogel, which also exhibits excellent cycling stability

  20. Synthesis of nano-Au doped SiO2 aerogels by seeding method

    International Nuclear Information System (INIS)

    Ren Hongbo; Wan Xiaobo; Zhang Lin; Du Aiming; Xiu Peng

    2006-01-01

    A new approach to synthesize gold nano cluster doped aerogel on the basis of surface-catalyzed reduction of metal ions was described. Au nano particles were formed in a silica aerogel matrix by hydroxylamine seeding method of reducing gold ions on the silica colloidal surface. Subsequently, the pH value of system was adjusted to about 7-8, the gel formed within 2 h. After aging for 2 d, the gels were washed in aceton, and then dried supercritically (from CO 2 ) to yield aerogels. The reduction process was attributed to hydroxylamine-induced surface catalysis. Au clusters in the aerogel monoliths were characterized with optical adsorption, transmission electron microscopy. These techniques have shown the cluster size and weight content in the aerogels. Brunauer-emmett-teller surface area measurements show that the specific surface area of silica aerogels and doped aerogels are higher than 800 m 2 /g. (authors)

  1. A Special Material or a New State of Matter: A Review and Reconsideration of the Aerogel

    Directory of Open Access Journals (Sweden)

    Jun Shen

    2013-03-01

    Full Text Available The ultrahighly nanoporous aerogel is recognized as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas, and diverse chemical compositions. In this review, the characteristics, classification, history and preparation of the aerogel were introduced. More attention was paid to the sol-gel method for preparing different kinds of aerogels, given its important role on bridging the synthetic parameters with the properties. At last, preparation of a novel single-component aerogel, design of a composite aerogel and industrial application of the aerogel were regarded as the research tendency of the aerogel state in the near future.

  2. Saline-water bioleaching of chalcopyrite with thermophilic, iron(II)- and sulfur-oxidizing microorganisms.

    Science.gov (United States)

    Watling, Helen R; Collinson, David M; Corbett, Melissa K; Shiers, Denis W; Kaksonen, Anna H; Watkin, Elizabeth L J

    2016-09-01

    The application of thermoacidophiles for chalcopyrite (CuFeS2) bioleaching in hot, acidic, saline solution was investigated as a possible process route for rapid Cu extraction. The study comprised a discussion of protective mechanisms employed for the survival and/or adaptation of thermoacidophiles to osmotic stress, a compilation of chloride tolerances for three genera of thermoacidophiles applied in bioleaching and an experimental study of the activities of three species in a saline bioleaching system. The data showed that the oxidation rates of iron(II) and reduced inorganic sulfur compounds (tetrathionate) were reduced in the presence of chloride levels well below chloride concentrations in seawater, limiting the applicability of these microorganisms in the bioleaching of CuFeS2 in saline water. Copyright © 2016. Published by Elsevier Masson SAS.

  3. A novel sensitive Cu(II) and Cd(II) nanosensor platform: Graphene oxide terminated p-aminophenyl modified glassy carbon surface

    International Nuclear Information System (INIS)

    Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Atar, Necip; Ustundag, Zafer; Solak, Ali Osman

    2013-01-01

    Graphical abstract: - Highlights: • We electrochemically prepared sensor based on graphene oxide. • The prepared electrode was characterized by using various techniques. • The proposed nanosensor showed good stability, selectivity and high sensitivity. • The proposed nanosensor electrode was used for the analysis of Cd(II) and Cu(II). - Abstract: Graphene oxide (GO) based glassy carbon (GC) electrode has been prepared. Firstly, p-nitrophenyl (NP) modified GC (NP/GC) electrode was prepared via the electrochemical reduction of its tetraflouroborate diazonium salt. After the formation of NP/GC electrode, the negative potential was applied to NP/GC electrode to reduce the nitro groups to amine. p-Aminophenyl (AP) modified GC (AP/GC) electrode was immersed into a graphene oxide solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide. Hence, we constructed GO terminated AP modified GC (GO/AP/GC) electrode. NP/GC, AP/GC and GO/AP/GC electrodes were characterized sequentially using cyclic voltammetry (CV) in the presence of 1.0 mM of potassium ferricyanide in 0.1 M KCl. In addition, GO and GO/AP/GC surfaces were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The GO/AP/GC electrode was used for the analysis of Cd(II) and Cu(II) ions by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) and Cu(II) ions were 1.0 × 10 −11 –5.0 × 10 −10 M and 3.3 × 10 −12 M (S/N = 3), respectively

  4. Effect of catalyst on melamine-formaldehyde organic aerogel

    International Nuclear Information System (INIS)

    Sun Zhipeng; Yang Xi; Fu Zhibing; Zhong Minglong; Wang Chaoyang; Ma Kangfu; Huang Xiaoli; Chang Lijuan

    2013-01-01

    A series of melamine-formaldehyde(MF) organic aerogel templates were prepared with different categories and concentration of catalyst. Their molecular structure, thermal stability and pore structure were tested by Fourier transform infrared spectroscopy, thermogravimetric analysis and nitrogen adsorption. It is indicated that the type and concentration of catalyst do not affect molecular structure and thermal stability of the MF organic aerogel template. The specific surface area and pore volume of the MF organic aerogel template using Na 2 CO 3 as catalyst are higher than those using NaOH, NaHCO 3 as catalyst. When the ratio of the concentration of melamine to that of catalyst is 500, the specific surface area is maximized. (authors)

  5. Development of windows based on highly insulating aerogel glazings

    DEFF Research Database (Denmark)

    Jensen, Karsten Ingerslev; Schultz, Jørgen Munthe; Kristiansen, Finn Harken

    2004-01-01

    of buildings, the window area is the weakest part with respect to the heat loss, but at the same time, it also provides e.g. solar energy gain. Glazing prototypes have been made of aerogel tiles of about 55 cm sq. (elaborated within the projects). Those tiles are quickly evacuated and easily sealed between two...... glass panes and a specific rim seal. A heat treatment phase (after the supercritical CO2 drying) of the aerogel is currently being developed in order to improve its optical quality. This step increases the solar transmittance about 6 percent points. For glazing prototypes with an aerogel thickness...... of approx. 15 mm, a centre heat loss coefficient of below 0.7 W/m² K and a solar transmittance of 76% have been obtained. The research is funded in part by the European Commission within the frameworks of the Non-Nuclear Energy Programme – JOULE III and the Energy, Environment and Sustainable Development...

  6. Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames

    International Nuclear Information System (INIS)

    Chakrabarty, Rajan K.; Novosselov, Igor V.; Beres, Nicholas D.; Moosmüller, Hans; Sorensen, Christopher M.; Stipe, Christopher B.

    2014-01-01

    We report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (−g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in −g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in −g flames, which reduces the time to gel for nanoparticles by ≈10 6  s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale.

  7. Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarty, Rajan K., E-mail: rajan.chakrabarty@gmail.com [Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130 (United States); Laboratory for Aerosol Science, Spectroscopy, and Optics, Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512 (United States); Novosselov, Igor V. [Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195 (United States); Enertechnix Inc., Maple Valley, Washington 98068 (United States); Beres, Nicholas D.; Moosmüller, Hans [Laboratory for Aerosol Science, Spectroscopy, and Optics, Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512 (United States); Sorensen, Christopher M. [Condensed Matter Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Stipe, Christopher B. [TSI Incorporated, 500 Cardigan Rd, Shoreview, Minnesota 55126 (United States)

    2014-06-16

    We report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (−g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in −g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in −g flames, which reduces the time to gel for nanoparticles by ≈10{sup 6} s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale.

  8. Aerogel Hybrid Composite Materials: Designs and Testing for Multifunctional Applications

    Science.gov (United States)

    Williams, Martha K.; Fesmire, James E.

    2016-01-01

    This webinar will introduce the broad spectrum of aerogel composites and their diverse performance properties such as reduced heat transfer to energy storage, and expands specifically on the aerogel/fiber laminate systems and testing methodologies. The multi-functional laminate composite system, AeroFiber, and its construction is designed by varying the type of fiber (e.g. polyester, carbon, Kevlar®, Spectra® or Innegral(TradeMark) and combinations thereof), the aerogel panel type and thickness, and overall layup configuration. The combination and design of materials may be customized and tailored to achieve a range of desired properties in the resulting laminate system. Multi-functional properties include structural strength, impact resistance, reduction in heat transfer, increased fire resistance, mechanical energy absorption, and acoustic energy dampening. Applications include aerospace, aircraft, automotive, boating, building and construction, lightweight portable structures, liquefied natural gas, cryogenics, transportation and energy, sporting equipment, and military protective gear industries.

  9. Aerogel-Based Insulation for Industrial Steam Distribution Systems

    Energy Technology Data Exchange (ETDEWEB)

    John Williams

    2011-03-30

    Thermal losses in industrial steam distribution systems account for 977 trillion Btu/year in the US, more than 1% of total domestic energy consumption. Aspen Aerogels worked with Department of Energy’s Industrial Technologies Program to specify, develop, scale-up, demonstrate, and deliver Pyrogel XT®, an aerogel-based pipe insulation, to market to reduce energy losses in industrial steam systems. The product developed has become Aspen’s best selling flexible aerogel blanket insulation and has led to over 60 new jobs. Additionally, this product has delivered more than ~0.7 TBTU of domestic energy savings to date, and could produce annual energy savings of 149 TBTU by 2030. Pyrogel XT’s commercial success has been driven by it’s 2-4X better thermal performance, improved durability, greater resistance to corrosion under insulation (CUI), and faster installation times than incumbent insulation materials.

  10. O2 Activation and Double C-H Oxidation by a Mononuclear Manganese(II) Complex.

    Science.gov (United States)

    Deville, Claire; Padamati, Sandeep K; Sundberg, Jonas; McKee, Vickie; Browne, Wesley R; McKenzie, Christine J

    2016-01-11

    A Mn(II) complex, [Mn(dpeo)2](2+) (dpeo=1,2-di(pyridin-2-yl)ethanone oxime), activates O2, with ensuing stepwise oxidation of the methylene group in the ligands providing an alkoxide and ultimately a ketone group. X-ray crystal-structure analysis of an intermediate homoleptic alkoxide Mn(III) complex shows tridentate binding of the ligand via the two pyridyl groups and the newly installed alkoxide moiety, with the oxime group no longer coordinated. The structure of a Mn(II) complex of the final ketone ligand, cis-[MnBr2(hidpe)2] (hidpe=2-(hydroxyimino)-1,2-di(pyridine-2-yl)ethanone) shows that bidentate oxime/pyridine coordination has been resumed. H2(18)O and (18)O2 labeling experiments suggest that the inserted O atoms originate from two different O2 molecules. The progress of the oxygenation was monitored through changes in the resonance-enhanced Raman bands of the oxime unit. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The hybrid nanostructure of MnCo2O4.5 nanoneedle/carbon aerogel for symmetric supercapacitors with high energy density

    Science.gov (United States)

    Hao, Pin; Zhao, Zhenhuan; Li, Liyi; Tuan, Chia-Chi; Li, Haidong; Sang, Yuanhua; Jiang, Huaidong; Wong, C. P.; Liu, Hong

    2015-08-01

    Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by calcination. The carbon aerogel exhibits a high electrical conductivity, high specific surface area and porous structure, ensuring high electrochemical performance of the hybrid nanostructure when coupled with the porous MnCo2O4.5 nanoneedles. The symmetric supercapacitor using the MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure as the active electrode material exhibits a high energy density of about 84.3 Wh kg-1 at a power density of 600 W kg-1. The voltage window is as high as 1.5 V in neutral aqueous electrolytes. Due to the unique nanostructure of the electrodes, the capacitance retention reaches 86% over 5000 cycles.Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by

  12. Ultrasound propagation in dense aerogels filled with liquid 4He

    International Nuclear Information System (INIS)

    Matsumoto, K; Ohmori, K; Abe, S; Kanamori, K; Nakanishi, K

    2012-01-01

    Longitudinal ultrasound propagation was studied in dense aerogels filled with liquid 4 He. Sound velocity and attenuation were measured at the frequency of 6 MHz in both normal and superfluid phases. Pressure dependence of velocity and attenuation were also studied. Studied aerogels had porosities about 85%. They had two different types of structure, tangled strand structure and aggregated particles structure. The pore size distributions were narrow. Reduction of superfluid transition temperature mainly depended on not porosity but mean pore size. The structure of gel played an important role in sound velocity and attenuation.

  13. Formation and pore structure of boron nitride aerogels

    International Nuclear Information System (INIS)

    Lindquist, D.H.; Borek, T.T.; Kramer, S.J.; Kramer, S.J.; Naruta, C.K.; Johnson, G.; Schaeffer, R.; Smith, D.M.; Paine, R.T.

    1990-01-01

    This paper reports gels containing a poly(borazinyl amine) and tetrahydrofuran processed by CO 2 supercritical drying techniques followed by pyrolysis. The resulting BN ceramic aerogels are highly porous, and the microstructure, porosity, and surface area characteristics have been examined. The aerogels show excellent thermal stability exhibiting surface areas in excess of 350 m 2 /g and porosities greater than 0.8 even when heated in argon at 1500 degrees C for 8 h. By removing solvent via evaporation before supercritical drying, the mean pore radius can be varied between 3.6 and 10 nm

  14. Using of Aerogel to Improve Thermal Insulating Properties of Windows

    Science.gov (United States)

    Valachova, Denisa; Zdrazilova, Nada; Panovec, Vladan; Skotnicova, Iveta

    2018-06-01

    For the best possible thermal-technical properties of building structures it is necessary to use materials with very low thermal conductivity. Due to the increasing thermal-technical requirements for building structures, the insulating materials are developed. One of the modern thermal insulating materials is so-called aerogel. Unfortunately, this material is not used in the field of external thermal insulation composite systems because of its price and its properties. The aim of this paper is to present possibilities of using this insulating material in the civil engineering - specifically a usage of aerogel in the production of windows.

  15. Coordination functionalization of graphene oxide with tetraazamacrocyclic complexes of nickel(II): Generation of paramagnetic centers

    Energy Technology Data Exchange (ETDEWEB)

    Basiuk, Vladimir A., E-mail: basiuk@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico); Department of Chemistry,Tufts University, 62 Talbot Avenue, Medford, MA 02155 (United States); Alzate-Carvajal, Natalia [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico); Henao-Holguín, Laura V. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico); Rybak-Akimova, Elena V. [Department of Chemistry,Tufts University, 62 Talbot Avenue, Medford, MA 02155 (United States); Basiuk, Elena V., E-mail: elbg1111@gmail.com [Department of Chemistry,Tufts University, 62 Talbot Avenue, Medford, MA 02155 (United States); Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico)

    2016-05-15

    Highlights: • [Ni(cyclam)]{sup 2+} and [Ni(tet b)]{sup 2+} cations coordinate to carboxylic groups of GO. • The coordination takes place under basic conditions in aqueous-based medium. • The coordination results in the conversion from low-spin to high-spin Ni(II). • Functionalized GO samples were characterized by various instrumental techniques. - Abstract: We describe a novel approach to functionalization of graphene oxide (GO) which allows for a facile generation of paramagnetic centers from two diamagnetic components. Coordination attachment of [Ni(cyclam)]{sup 2+} or [Ni(tet b)]{sup 2+} tetraazamacrocyclic cations to carboxylic groups of GO takes place under basic conditions in aqueous-based reaction medium. The procedure is very straightforward and does not require high temperatures or other harsh conditions. Changing the coordination geometry of Ni(II) from square-planar tetracoordinated to pseudooctahedral hexacoordinated brings about the conversion from low-spin to high-spin state of the metal centers. Even though the content of tetraazamacrocyclic complexes in functionalized GO samples was found to be relatively low (nickel content of ca. 1 wt%, as determined by thermogravimetric analysis, elemental analysis and energy dispersive X-ray spectroscopy), room temperature magnetic susceptibility measurements easily detected the appearance of paramagnetic properties in GO + [Ni(cyclam)] and GO + [Ni(tet b)] nanohybrids, with effective magnetic moments of 1.95 BM and 2.2 BM for, respectively. According to density functional theory calculations, the main spin density is localized at the macrocyclic complexes, without considerable extension to graphene sheet, which suggests insignificant ferromagnetic coupling in the nanohybrids, in agreement with the results of magnetic susceptibility measurements. The coordination attachment of Ni(II) tetraazamacrocycles to GO results in considerable changes in Fourier-transform infrared and X-ray photoelectron spectra

  16. Simultaneous removal of Cd(II) and Sb(V) by Fe–Mn binary oxide: Positive effects of Cd(II) on Sb(V) adsorption

    International Nuclear Information System (INIS)

    Liu, Ruiping; Liu, Feng; Hu, Chengzhi; He, Zan; Liu, Huijuan; Qu, Jiuhui

    2015-01-01

    Highlights: • Fe–Mn binary oxide achieves the simultaneous removal of Cd(II) and Sb(V). • Cd(II) at above 0.25 mmol/L improves Sb(V) adsorption onto FMBO. • Cd(II) improves more significant Sb(V) adsorption than Ca"2"+ and Mn"2"+. • Sb(V) adsorption decreases whereas Cd(II) adsorption increases with elevated pH. • The increased ζ-potential and Cd(II)–Sb(V) precipitation favors Sb(V) adsorption. - Abstract: The coexistence of cadmium ion (Cd(II)) and antimonate (Sb(V)) creates the need for their simultaneous removal. This study aims to investigate the effects of positively-charged Cd(II) on the removal of negative Sb(V) ions by Fe–Mn binary oxide (FMBO) and associated mechanisms. The maximum Sb(V) adsorption density (Q_m_a_x_,_S_b_(_V_)) increased from 1.02 to 1.32 and 2.01 mmol/g in the presence of Cd(II) at 0.25 and 0.50 mmol/L. Cd"2"+ exhibited a more significant positive effect than both calcium ion (Ca"2"+) and manganese ion (Mn"2"+). Cd"2"+ showed higher affinity towards FMBO and increased its ζ-potential more significantly compared to Ca"2"+ and Mn"2"+. The simultaneous adsorption of Sb(V) and Cd(II) onto FMBO can be achieved over a wide initial pH (pH_i) range from 2 to 9, and Q_S_b_(_V_) decreases whereas Q_C_d_(_I_I_) increases with elevated pH_i. Their combined values, as expressed by Q_S_b_(_V_)_+_C_d_(_I_I_), amount to about 2 mmol/g and vary slightly in the pH_i range 4–9. FTIR and XPS spectra indicate the significant synergistic effect of Cd(II) on Sb(V) adsorption onto FMBO, and that little chemical valence transformation occurs. These results may be valuable for the treatment of wastewater with coexisting heavy metals such as Cd(II) and Sb(V).

  17. Adsorption and co-adsorption of graphene oxide and Ni(II) on iron oxides: A spectroscopic and microscopic investigation.

    Science.gov (United States)

    Sheng, Guodong; Huang, Chengcai; Chen, Guohe; Sheng, Jiang; Ren, Xuemei; Hu, Baowei; Ma, Jingyuan; Wang, Xiangke; Huang, Yuying; Alsaedi, Ahmed; Hayat, Tasawar

    2018-02-01

    Graphene oxide (GO) may strongly interact with toxic metal ions and mineral particles upon release into the soil environment. We evaluated the mutual effects between GO and Ni (Ni(II)) with regard to their adsorption and co-adsorption on two minerals (goethite and hematite) in aqueous phase. Results indicated that GO and Ni could mutually facilitate the adsorption of each other on both goethite and hematite over a wide pH range. Addition of Ni promoted GO co-adsorption mainly due to the increased positive charge of minerals and cation-π interactions, while the presence of GO enhanced Ni co-adsorption predominantly due to neutralization of positive charge and strong interaction with oxygen-containing functional groups on adsorbed GO. Increasing adsorption of GO and Ni on minerals as they coexist may thus reduce their mobility in soil. Extended X-ray absorption fine structure (EXAFS) spectroscopy data revealed that GO altered the microstructure of Ni on minerals, i.e., Ni formed edge-sharing surface species (at R Ni-Fe ∼3.2 Å) without GO, while a GO-bridging ternary surface complexes (at R Ni-C ∼2.49 Å and R Ni-Fe ∼4.23 Å) was formed with GO. These findings improved the understanding of potential fate and toxicity of GO as well as the partitioning processes of Ni ions in aquatic and soil environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Physiology, Fe(II oxidation, and Fe mineral formation by a marine planktonic cyanobacterium grown under ferruginous conditions

    Directory of Open Access Journals (Sweden)

    Elizabeth D. Swanner

    2015-10-01

    Full Text Available Evidence for Fe(II oxidation and deposition of Fe(III-bearing minerals from anoxic or redox-stratified Precambrian oceans has received support from decades of sedimentological and geochemical investigation of Banded Iron Formations (BIF. While the exact mechanisms of Fe(II oxidation remains equivocal, reaction with O2 in the marine water column, produced by cyanobacteria or early oxygenic phototrophs, was likely. In order to understand the role of cyanobacteria in the deposition of Fe(III minerals to BIF, we must first know how planktonic marine cyanobacteria respond to ferruginous (anoxic and Fe(II-rich waters in terms of growth, Fe uptake and homeostasis, and Fe mineral formation. We therefore grew the common marine cyanobacterium Synechococcus PCC 7002 in closed bottles that began anoxic, and contained Fe(II concentrations that span the range of possible concentrations in Precambrian seawater. These results, along with cell suspension experiments, indicate that Fe(II is likely oxidized by this strain via chemical oxidation with oxygen produced during photosynthesis, and not via any direct enzymatic or photosynthetic pathway. Imaging of the cell-mineral aggregates with scanning electron microscopy (SEM and confocal laser scanning microscopy (CLSM are consistent with extracellular precipitation of Fe(III (oxyhydroxide minerals, but that >10% of Fe(III sorbs to cell surfaces rather than precipitating. Proteomic experiments support the role of reactive oxygen species (ROS in Fe(II toxicity to Synechococcus PCC 7002. The proteome expressed under low Fe conditions included multiple siderophore biosynthesis and siderophore and Fe transporter proteins, but most siderophores are not expressed during growth with Fe(II. These results provide a mechanistic and quantitative framework for evaluating the geochemical consequences of perhaps life’s greatest metabolic innovation, i.e. the evolution and activity of oxygenic photosynthesis, in ferruginous

  19. Angiotensin II type 1a receptor-deficient mice develop angiotensin II-induced oxidative stress and DNA damage without blood pressure increase.

    Science.gov (United States)

    Zimnol, Anna; Amann, Kerstin; Mandel, Philipp; Hartmann, Christina; Schupp, Nicole

    2017-12-01

    Hypertensive patients have an increased risk of developing kidney cancer. We have shown in vivo that besides elevating blood pressure, angiotensin II causes DNA damage dose dependently. Here, the role of blood pressure in the formation of DNA damage is studied. Mice lacking one of the two murine angiotensin II type 1 receptor (AT1R) subtypes, AT1aR, were equipped with osmotic minipumps, delivering angiotensin II during 28 days. Parameters of oxidative stress and DNA damage of kidneys and hearts of AT1aR-knockout mice were compared with wild-type (C57BL/6) mice receiving angiotensin II, and additionally, with wild-type mice treated with candesartan, an antagonist of both AT1R subtypes. In wild-type mice, angiotensin II induced hypertension, reduced kidney function, and led to a significant formation of reactive oxygen species (ROS). Furthermore, genomic damage was markedly increased in this group. All these responses to angiotensin II could be attenuated by concurrent administration of candesartan. In AT1aR-deficient mice treated with angiotensin II, systolic pressure was not increased, and renal function was not affected. However, angiotensin II still led to an increase of ROS in kidneys and hearts of these animals. Additionally, genomic damage in the form of double-strand breaks was significantly induced in kidneys of AT1aR-deficient mice. Our results show that angiotensin II induced ROS production and DNA damage even without the presence of AT1aR and independently of blood pressure changes. Copyright © 2017 the American Physiological Society.

  20. Uptake and Release of Cerium During Fe-Oxide Formation and Transformation in Fe(II) Solutions

    DEFF Research Database (Denmark)

    Nedel, Sorin; Dideriksen, Knud; Christiansen, Bo C.

    2010-01-01

    Fe-oxides are ubiquitous in soils and sediments and form during Fe(0) corrosion. Depending on redox conditions and solution composition, Fe-oxides such as ferrihydrite, goethite, magnetite, and green rust (GR) may form. These phases typically have high surface area and large affinity for adsorption......(III) release. X-ray photoelectron spectroscopy revealed Ce(III) adsorbed on magnetite. When Fe-oxides were synthesized by air oxidation of Fe(II) solutions at pH 7, GR(Na,SO4) played a catalytic role in the oxidation of Ce(III) to Ce(IV) by O-2, removing more than 90% of the dissolved Ce. Transmission electron...

  1. Flexible, highly graphitized carbon aerogels based on bacterial cellulose/lignin: Catalyst-free synthesis and its application in energy storage devices

    KAUST Repository

    Xu, Xuezhu; Zhou, Jian; Nagaraju, Doddahalli H.; Jiang, Long; Marinov, Val R.; Lubineau, Gilles; Alshareef, Husam N.; Oh, Myungkeun

    2015-01-01

    Currently, most carbon aerogels are based on carbon nanotubes (CNTs) or graphene, which are produced through a catalyst-assisted chemical vapor deposition method. Biomass based organic aerogels and carbon aerogels, featuring low cost, high

  2. Non-noble metal graphene oxide-copper (II) ions hybrid electrodes for electrocatalytic hydrogen evolution reaction

    KAUST Repository

    Muralikrishna, S.; Ravishankar, T.N.; Ramakrishnappa, T.; Nagaraju, Doddahalli H.; Krishna Pai, Ranjith

    2015-01-01

    Non-noble metal and inexpensive graphene oxide-copper (II) ions (GO-Cu2+) hybrid catalysts have been explored for the hydrogen evolution reaction (HER). We were able to tune the binding abilities of GO toward the Cu2+ ions and hence their catalytic

  3. Cu(II)-catalyzed esterification reaction via aerobic oxidative cleavage of C(CO)-C(alkyl) bonds.

    Science.gov (United States)

    Ma, Ran; He, Liang-Nian; Liu, An-Hua; Song, Qing-Wen

    2016-02-04

    A novel Cu(II)-catalyzed aerobic oxidative esterification of simple ketones for the synthesis of esters has been developed with wide functional group tolerance. This process is assumed to go through a tandem sequence consisting of α-oxygenation/esterification/nucleophilic addition/C-C bond cleavage and carbon dioxide is released as the only byproduct.

  4. A ruthenium(II) complex as turn-on Cu(II) luminescent sensor based on oxidative cyclization mechanism and its application in vivo

    Science.gov (United States)

    Zhang, Yunfei; Liu, Zonglun; Yang, Kui; Zhang, Yi; Xu, Yongqian; Li, Hongjuan; Wang, Chaoxia; Lu, Aiping; Sun, Shiguo

    2015-02-01

    Copper ions play a vital role in a variety of fundamental physiological processes not only in human beings and plants, but also for extensive insects and microorganisms. In this paper, a novel water-soluble ruthenium(II) complex as a turn-on copper(II) ions luminescent sensor based on o-(phenylazo)aniline was designed and synthesized. The azo group would undergo a specific oxidative cyclization reaction with copper(II) ions and turn into high luminescent benzotriazole, triggering significant luminescent increasements which were linear to the concentrations of copper(II) ions. The sensor distinguished by its high sensitivity (over 80-fold luminescent switch-on response), good selectivity (the changes of the emission intensity in the presence of other metal ions or amino acids were negligible) and low detection limit (4.42 nM) in water. Moreover, the copper(II) luminescent sensor exhibited good photostability under light irradiation. Furthermore, the applicability of the proposed sensor in biological samples assay was also studied and imaged copper(II) ions in living pea aphids successfully.

  5. Influence of organics and silica on Fe(II) oxidation rates and cell-mineral aggregate formation by the green-sulfur Fe(II)-oxidizing bacterium Chlorobium ferrooxidans KoFox - Implications for Fe(II) oxidation in ancient oceans

    Science.gov (United States)

    Gauger, Tina; Byrne, James M.; Konhauser, Kurt O.; Obst, Martin; Crowe, Sean; Kappler, Andreas

    2016-06-01

    Most studies on microbial phototrophic Fe(II) oxidation (photoferrotrophy) have focused on purple bacteria, but recent evidence points to the importance of green-sulfur bacteria (GSB). Their recovery from modern ferruginous environments suggests that these photoferrotrophs can offer insights into how their ancient counterparts grew in Archean oceans at the time of banded iron formation (BIF) deposition. It is unknown, however, how Fe(II) oxidation rates, cell-mineral aggregate formation, and Fe-mineralogy vary under environmental conditions reminiscent of the geological past. To address this, we studied the Fe(II)-oxidizer Chlorobium ferrooxidans KoFox, a GSB living in co-culture with the heterotrophic Geospirillum strain KoFum. We investigated the mineralogy of Fe(III) metabolic products at low/high light intensity, and in the presence of dissolved silica and/or fumarate. Silica and fumarate influenced the crystallinity and particle size of the produced Fe(III) minerals. The presence of silica also enhanced Fe(II) oxidation rates, especially at high light intensities, potentially by lowering Fe(II)-toxicity to the cells. Electron microscopic imaging showed no encrustation of either KoFox or KoFum cells with Fe(III)-minerals, though weak associations were observed suggesting co-sedimentation of Fe(III) with at least some biomass via these aggregates, which could support diagenetic Fe(III)-reduction. Given that GSB are presumably one of the most ancient photosynthetic organisms, and pre-date cyanobacteria, our findings, on the one hand, strengthen arguments for photoferrotrophic activity as a likely mechanism for BIF deposition on a predominantly anoxic early Earth, but, on the other hand, also suggest that preservation of remnants of Fe(II)-oxidizing GSB as microfossils in the rock record is unlikely.

  6. Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

    KAUST Repository

    Turias, Francesc; Solà , Miquel; Falivene, Laura; Cavallo, Luigi; Poater, Albert

    2015-01-01

    The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

  7. Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

    KAUST Repository

    Turias, Francesc

    2015-09-09

    The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

  8. The removal of hydrogen sulfide from gas streams using an aqueous metal sulfate absorbent : Part II. the regeneration of copper sulfide to copper oxide - An experimental study

    NARCIS (Netherlands)

    Ter Maat, H.; Hogendoorn, J. A.; Versteeg, G. F.

    2005-01-01

    Aim of this study was to investigate the possibilities for a selective and efficient method to convert copper(II) sulfide (CuS) into copper(II) oxide (CuO). The oxidation of copper sulfide has been studied experimentally using a thermogravimetric analyzer (TGA) at temperatures ranging from 450 to

  9. Evaluation of Fe(II) oxidation at an acid mine drainage site using laboratory-scale reactors

    Science.gov (United States)

    Brown, Juliana; Burgos, William

    2010-05-01

    Acid mine drainage (AMD) is a severe environmental threat to the Appalachian region of the Eastern United States. The Susquehanna and Potomac River basins of Pennsylvania drain to the Chesapeake Bay, which is heavily polluted by acidity and metals from AMD. This study attempted to unravel the complex relationships between AMD geochemistry, microbial communities, hydrodynamic conditions, and the mineral precipitates for low-pH Fe mounds formed downstream of deep mine discharges, such as Lower Red Eyes in Somerset County, PA, USA. This site is contaminated with high concentrations of Fe (550 mg/L), Mn (115 mg/L), and other trace metals. At the site 95% of dissolved Fe(II) and 56% of total dissolved Fe is removed without treatment, across the mound, but there is no change in the concentration of trace metals. Fe(III) oxides were collected across the Red Eyes Fe mound and precipitates were analyzed by X-ray diffraction, electron microscopy and elemental analysis. Schwertmannite was the dominant mineral phase with traces of goethite. The precipitates also contained minor amounts of Al2O3, MgO,and P2O5. Laboratory flow-through reactors were constructed to quantify Fe(II) oxidation and Fe removal over time at terrace and pool depositional facies. Conditions such as residence time, number of reactors in sequence and water column height were varied to determine optimal conditions for Fe removal. Reactors with sediments collected from an upstream terrace oxidized more than 50% of dissolved Fe(II) at a ten hour residence time, while upstream pool sediments only oxidized 40% of dissolved Fe(II). Downstream terrace and pool sediments were only capable of oxidizing 25% and 20% of Fe(II), respectively. Fe(II) oxidation rates measured in the reactors were determined to be between 3.99 x 10-8and 1.94 x 10-7mol L-1s-1. The sediments were not as efficient for total dissolved Fe removal and only 25% was removed under optimal conditions. The removal efficiency for all sediments

  10. Temporal changes in cardiac oxidative stress, inflammation and remodeling induced by exercise in hypertension: Role for local angiotensin II reduction.

    Directory of Open Access Journals (Sweden)

    Sebastião D Silva

    Full Text Available Exercise training reduces renin-angiotensin system (RAS activation, decreases plasma and tissue oxidative stress and inflammation in hypertension. However, the temporal nature of these phenomena in response to exercise is unknown. We sought to determine in spontaneously hypertensive rats (SHR and age-matched WKY controls the weekly effects of training on blood pressure (BP, plasma and left ventricle (LV Ang II and Ang-(1-7 content (HPLC, LV oxidative stress (DHE staining, gene and protein expression (qPCR and WB of pro-inflammatory cytokines, antioxidant enzymes and their consequence on hypertension-induced cardiac remodeling. SHR and WKY were submitted to aerobic training (T or maintained sedentary (S for 8 weeks; measurements were made at weeks 0, 1, 2, 4 and 8. Hypertension-induced cardiac hypertrophy was accompanied by acute plasma Ang II increase with amplified responses during the late phase of LV hypertrophy. Similar pattern was observed for oxidative stress markers, TNF alpha and interleukin-1β, associated with cardiomyocytes' diameter enlargement and collagen deposition. SHR-T exhibited prompt and marked decrease in LV Ang II content (T1 vs T4 in WKY-T, normalized oxidative stress (T2, augmented antioxidant defense (T4 and reduced both collagen deposition and inflammatory profile (T8, without changing cardiomyocytes' diameter and LV hypertrophy. These changes were accompanied by decreased plasma Ang II content (T2-T4 and reduced BP (T8. SHR-T and WKY-T showed parallel increases in LV and plasma Ang-(1-7 content. Our data indicate that early training-induced downregulation of LV ACE-AngII-AT1 receptor axis is a crucial mechanism to reduce oxidative/pro-inflammatory profile and improve antioxidant defense in SHR-T, showing in addition this effect precedes plasma RAS deactivation.

  11. Fabrication and characterization of Aerogel-Polydimethyl siloxane (PDMS) Insulation Film

    Science.gov (United States)

    Noh, Yeoung ah; Song, Sinae; Taik Kim, Hee

    2018-03-01

    The building has a large impact on the space heating demand and the indoor environment is affected by climate or daylight. Hence, silica aerogel has generally used as a film to reduce the coefficient of the window in the building. Silica aerogel is a suitable material to apply for insulation material with lower thermal conductivity than that of air to save interior energy. However expensive precursor and drying process were the main issue of the silica aerogel synthesis and practical usage. We attempt to fabricate aerogel insulation film for energy saving through the economic process under ambient pressure. Silica aerogel was synthesized from rice husk ash, which was an agricultural waste to be able to recycle. Taguchi design was used to optimize the parameters (amount of rice husk ash, pH, aging time) controlling the surface area of silica aerogel. The silica aerogel is prepared by sol-gel processing through acidic treatment and aging. The silica aerogel was obtained by modification of silica hydrogel surface and dry at ambient pressure. Finally, aerogel film was respectively fabricated by the different content of aerogel in polydimethylsiloxane (PDMS). Silica aerogel obtained 21 – 24nm average particle size was analyzed by SEM and silica aerogel with high surface area (832.26 m2/g), pore size ( 3.30nm ) was characterized by BET. Then silica Aerogel – PDMS insulation film with thermal conductivity (0.002 W/mK) was analyzed by thermal wave system. The study demonstrates an eco-friendly and low-cost route toward silica – PDMS insulation film with low thermal conductivity (0.002 W/mK).

  12. Amorphous manganese-calcium oxides as a possible evolutionary origin for the CaMn₄ cluster in photosystem II.

    Science.gov (United States)

    Najafpour, Mohammad Mahdi

    2011-06-01

    In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn(3+) in a distorted octahedral environment and eight-coordinate Ca(2+) centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn₂O₄), pyrolusite (MnO₂) and compared with hollandite (Ba(0.2)Ca(0.15)K(0.3)Mn(6.9)Al(0.2)Si(0.3)O(16)), hausmannite (Mn₃O₄), Mn₂O₃.H₂O, Ca Mn₃O₆.H₂O, CaMn₄O₈.H₂O, CaMn₂O₄.H₂O and synthetic marokite (CaMn₂O₄). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II.

  13. Aerogel-Based Insulation for High-Temperature Industrial Processes

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Owen Evans

    2011-10-13

    Under this program, Aspen Aerogels has developed an industrial insulation called Pyrogel HT, which is 4-5 times more thermally efficient than current non-aerogel technology. Derived from nanoporous silica aerogels, Pyrogel HT was specifically developed to address a high temperature capability gap not currently met with Aspen Aerogels{trademark} flagship product, Pyrogel XT. Pyrogel XT, which was originally developed on a separate DOE contract (DE-FG36-06GO16056), was primarily optimized for use in industrial steam processing systems, where application temperatures typically do not exceed 400 C. At the time, further improvements in thermal performance above 400 C could not be reasonably achieved for Pyrogel XT without significantly affecting other key material properties using the current technology. Cumulative sales of Pyrogel HT into domestic power plants should reach $125MM through 2030, eventually reaching about 10% of the total insulation market share in that space. Global energy savings would be expected to scale similarly. Over the same period, these sales would reduce domestic energy consumption by more than 65 TBtu. Upon branching out into all industrial processes in the 400 C-650 C regime, Pyrogel HT would reach annual sales levels of $150MM, with two-thirds of that being exported.

  14. Aerogel-Based Antennas for Aerospace and Terrestrial Applications

    Science.gov (United States)

    Meador, Mary Ann (Inventor); Miranda, Felix (Inventor); Van Keuls, Frederick (Inventor)

    2016-01-01

    Systems and methods for lightweight, customizable antenna with improved performance and mechanical properties are disclosed. In some aspects, aerogels can be used, for example, as a substrate for antenna fabrication. The reduced weight and expense, as well as the increased ability to adapt antenna designs, permits a systems to mitigate a variety of burdens associated with antennas while providing added benefits.

  15. Synthesis and Properties of Cross-Linked Polyamide Aerogels

    Science.gov (United States)

    Williams, Jarrod C.; Meador, Mary Ann; McCorkle, Linda

    2015-01-01

    We report the first synthesis of cross-linked polyamide aerogels through step growth polymerization using a combination of diamines, diacid chloride and triacid chloride. Polyamide oligomers endcapped with amines are prepared as stable solutions in N-methylpyrrolidinone from several different diamine precursors and 1,3-benzenedicarbonyl dichloride. Addition of 1,3,5-benzenetricarbonyl trichloride yields gels which form in under five minutes according to the scheme shown. Solvent exchange of the gels into ethanol, followed by drying using supercritical CO2 extraction gives colorless aerogels with densities around 0.1 to 0.2 gcm3. Thicker monolithes of the polyamide aerogels are stiff and strong, while thin films of certain formulations are highly flexible, durable, and even translucent. These materials may have use as insulation for deployable space structures, rovers, habitats or extravehicular activity suits as well as in many terrestrial applications. Strucure property relationships of the aerogels, including surface area, mechanical properties, and thermal conductivity will be discussed.

  16. Adsorption of Cu(II) on Oxidized Multi-Walled Carbon Nanotubes in the Presence of Hydroxylated and Carboxylated Fullerenes

    Science.gov (United States)

    Wang, Jing; Li, Zhan; Li, Shicheng; Qi, Wei; Liu, Peng; Liu, Fuqiang; Ye, Yuanlv; Wu, Liansheng; Wang, Lei; Wu, Wangsuo

    2013-01-01

    The adsorption of Cu(II) on oxidized multi-walled carbon nanotubes (oMWCNTs) as a function of contact time, pH, ionic strength, temperature, and hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) were studied under ambient conditions using batch techniques. The results showed that the adsorption of Cu(II) had rapidly reached equilibrium and the kinetic process was well described by a pseudo-second-order rate model. Cu(II) adsorption on oMWCNTs was dependent on pH but independent of ionic strength. Compared with the Freundlich model, the Langmuir model was more suitable for analyzing the adsorption isotherms. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Cu(II) adsorption on oMWCNTs was spontaneous and endothermic. The effect of C60(OH)n on Cu(II) adsorption of oMWCNTs was not significant at low C60(OH)n concentration, whereas a negative effect was observed at higher concentration. The adsorption of Cu(II) on oMWCNTs was enhanced with increasing pH values at pH adsorption of Cu(II) onto oMWCNTs at pH 4–6. The double sorption site model was applied to simulate the adsorption isotherms of Cu(II) in the presence of C60(OH)n and fitted the experimental data well. PMID:24009683

  17. Quantitative analysis of O-2 and Fe2+ profiles in gradient tubes for cultivation of microaerophilic Iron(II)-oxidizing bacteria

    DEFF Research Database (Denmark)

    Lueder, U.; Druschel, G.; Emerson, D.

    2018-01-01

    The classical approach for the cultivation of neutrophilic microaerophilic Fe(II)-oxidizing bacteria is agar-based gradient tubes where these bacteria find optimal growth conditions in opposing gradients of oxygen (O-2) and dissolved Fe(II) (Fe2+). The goals of this study were to quantify...... imply that transfer of cultures to fresh tubes within 48-72 h is crucial to provide optimal growth conditions for microaerophilic Fe(II)-oxidizers, particularly for the isolation of new strains....

  18. On the improvement of mechanical properties of monolithic silica aerogels (for transparent insulating material); Silica aerogel (tomei dannetsu zairyo) kyodo no kaizen ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Tajiri, K; Igarashi, K; Tanemura, S [National Industrial Research Institute of Nagoya, Nagoya (Japan)

    1997-11-25

    Study was made on improvement of the strength of silica aerogel as transparent insulating material. Silica aerogel is a low-density porous material with high heat insulation and transparency. To develop a insulating material with high transparency, monolithic silica aerogel was studied. For direct use of it for windows, its strength improvement was attempted. The aerogel was prepared by supercritical drying (alcohol or CO2) of silica wet gel obtained by hydrolysis and condensation of silicon alkoxide solution. To prepare the aerogel bonded on plate glass for strength improvement, the aerogel was bonded to alkoxide by exposing active silanol radical through F-etching of plate glass surface. However, to obtain the practical large-area bonded aerogel, shrinkage control of the aerogel in supercritical drying was necessary. Addition of Laponite into a silica network for strength improvement by polymer increased the bending strength by 50%. Although some reduction of its transparency was observed because of clouding, its heat insulation was stable. Further strength improvement is necessary for its practical use. 5 figs., 1 tab.

  19. IGF-II promotes neuroprotection and neuroplasticity recovery in a long-lasting model of oxidative damage induced by glucocorticoids.

    Science.gov (United States)

    Martín-Montañez, E; Millon, C; Boraldi, F; Garcia-Guirado, F; Pedraza, C; Lara, E; Santin, L J; Pavia, J; Garcia-Fernandez, M

    2017-10-01

    Insulin-like growth factor-II (IGF-II) is a naturally occurring hormone that exerts neurotrophic and neuroprotective properties in a wide range of neurodegenerative diseases and ageing. Accumulating evidence suggests that the effects of IGF-II in the brain may be explained by its binding to the specific transmembrane receptor, IGFII/M6P receptor (IGF-IIR). However, relatively little is known regarding the role of IGF-II through IGF-IIR in neuroprotection. Here, using adult cortical neuronal cultures, we investigated whether IGF-II exhibits long-term antioxidant effects and neuroprotection at the synaptic level after oxidative damage induced by high and transient levels of corticosterone (CORT). Furthermore, the involvement of the IGF-IIR was also studied to elucidate its role in the neuroprotective actions of IGF-II. We found that neurons treated with IGF-II after CORT incubation showed reduced oxidative stress damage and recovered antioxidant status (normalized total antioxidant status, lipid hydroperoxides and NAD(P) H:quinone oxidoreductase activity). Similar results were obtained when mitochondria function was analysed (cytochrome c oxidase activity, mitochondrial membrane potential and subcellular mitochondrial distribution). Furthermore, neuronal impairment and degeneration were also assessed (synaptophysin and PSD-95 expression, presynaptic function and FluoroJade B® stain). IGF-II was also able to recover the long-lasting neuronal cell damage. Finally, the effects of IGF-II were not blocked by an IGF-IR antagonist, suggesting the involvement of IGF-IIR. Altogether these results suggest that, in or model, IGF-II through IGF-IIR is able to revert the oxidative damage induced by CORT. In accordance with the neuroprotective role of the IGF-II/IGF-IIR reported in our study, pharmacotherapy approaches targeting this pathway may be useful for the treatment of diseases associated with cognitive deficits (i.e., neurodegenerative disorders, depression, etc

  20. The mechanism of the catalytic oxidation of hydrogen sulfide: II. Kinetics and mechanism of hydrogen sulfide oxidation catalyzed by sulfur

    NARCIS (Netherlands)

    Steijns, M.; Derks, F.; Verloop, A.; Mars, P.

    1976-01-01

    The kinetics of the catalytic oxidation of hydrogen sulfide by molecular oxygen have been studied in the temperature range 20–250 °C. The primary reaction product is sulfur which may undergo further oxidation to SO2 at temperatures above 200 °C. From the kinetics of this autocatalytic reaction we

  1. Oxidatively Stable Flexible Aerogel Composites for Reusable TPS, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA?s Next Generation Launch Vehicle Technology Program has an interest in robust TPS materials with the highest level of thermal performance at the lowest possible...

  2. Electrochemical Properties of High Surface Area Vanadium Oxide Aerogels

    National Research Council Canada - National Science Library

    Dong, Winny

    2001-01-01

    .... Traditional composite electrode structures have prevented truly quantitative analysis of surface area effects in nanoscale battery materials, as well as a study of their innate electrochemical behavior...

  3. Robust superhydrophobic bridged silsesquioxane aerogels with tunable performances and their applications.

    Science.gov (United States)

    Wang, Zhen; Wang, Dong; Qian, Zhenchao; Guo, Jing; Dong, Haixia; Zhao, Ning; Xu, Jian

    2015-01-28

    Aerogels are a family of highly porous materials whose applications are commonly restricted by poor mechanical properties. Herein, thiol-ene chemistry is employed to synthesize a series of novel bridged silsesquioxane (BSQ) precursors with various alkoxy groups. On the basis of the different hydrolyzing rates of the methoxy and ethoxy groups, robust superhydrophobic BSQ aerogels with tailorable morphology and mechanical performances have been prepared. The flexible thioether bridge contributes to the robustness of the as-formed aerogels, and the property can be tuned on the basis of the distinct combinations of alkoxy groups with the density of the aerogels almost unchanged. To the best of our knowledge, the lowest density among the ambient pressure dried aerogels is obtained. Further, potential application of the aerogels for oil/water separation and acoustic materials has also been presented.

  4. Methods for controlling pore morphology in aerogels using electric fields and products thereof

    Science.gov (United States)

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Olson, Tammy Y.; Kuntz, Joshua D.; Rose, Klint A.

    2017-12-16

    In one embodiment, an aerogel or xerogel includes column structures of a material having minor pores therein and major pores devoid of the material positioned between the column structures, where longitudinal axes of the major pores are substantially parallel to one another. In another embodiment, a method includes heating a sol including aerogel or xerogel precursor materials to cause gelation thereof to form an aerogel or xerogel and exposing the heated sol to an electric field, wherein the electric field causes orientation of a microstructure of the sol during gelation, which is retained by the aerogel or xerogel. In one approach, an aerogel has elongated pores extending between a material arranged in column structures having structural characteristics of being formed from a sol exposed to an electric field that causes orientation of a microstructure of the sol during gelation which is retained by the elongated pores of the aerogel.

  5. Spray freeze-dried nanofibrillated cellulose aerogels with thermal superinsulating properties.

    Science.gov (United States)

    Jiménez-Saelices, Clara; Seantier, Bastien; Cathala, Bernard; Grohens, Yves

    2017-02-10

    Nanofibrillated cellulose (NFC) aerogels were prepared by spray freeze-drying (SFD). Their structural, mechanical and thermal insulation properties were compared to those of NFC aerogels prepared by conventional freeze-drying (CFD). The purpose of this investigation is to develop superinsulating bioaerogels by reducing their pore size. Severe reduction of the aerogel pore size and skeleton architecture were observed by SEM, aerogels prepared by SFD method show a fibril skeleton morphology, which defines a mesoporous structure. BET analyses confirm the appearance of a new organization structure with pores of nanometric sizes. As a consequence, the thermal insulation properties were significantly improved for SFD materials compared to CFD aerogel, reaching values of thermal conductivity as low as 0.018W/(mK). Moreover, NFC aerogels have a thermal conductivity below that of air in ambient conditions, making them one of the best cellulose based thermal superinsulating material. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Applicability of anaerobic nitrate-dependent Fe(II) oxidation to microbial enhanced oil recovery (MEOR).

    Science.gov (United States)

    Zhu, Hongbo; Carlson, Han K; Coates, John D

    2013-08-06

    Microbial processes that produce solid-phase minerals could be judiciously applied to modify rock porosity with subsequent alteration and improvement of floodwater sweep in petroleum reservoirs. However, there has been little investigation of the application of this to enhanced oil recovery (EOR). Here, we investigate a unique approach of altering reservoir petrology through the biogenesis of authigenic rock minerals. This process is mediated by anaerobic chemolithotrophic nitrate-dependent Fe(II)-oxidizing microorganisms that precipitate iron minerals from the metabolism of soluble ferrous iron (Fe(2+)) coupled to the reduction of nitrate. This mineral biogenesis can result in pore restriction and reduced pore throat diameter. Advantageously and unlike biomass plugs, these biominerals are not susceptible to pressure or thermal degradation. Furthermore, they do not require continual substrate addition for maintenance. Our studies demonstrate that the biogenesis of insoluble iron minerals in packed-bed columns results in effective hydrology alteration and homogenization of heterogeneous flowpaths upon stimulated microbial Fe(2+) biooxidation. We also demonstrate almost 100% improvement in oil recovery from hydrocarbon-saturated packed-bed columns as a result of this metabolism. These studies represent a novel departure from traditional microbial EOR approaches and indicate the potential for nitrate-dependent Fe(2+) biooxidation to improve volumetric sweep efficiency and enhance both the quality and quantity of oil recovered.

  7. Anoxic and Oxic Oxidation of Rocks Containing Fe(II)Mg-Silicates and Fe(II)-Monosulfides as Source of Fe(III)-Minerals and Hydrogen. Geobiotropy.

    Science.gov (United States)

    Bassez, Marie-Paule

    2017-12-01

    In this article, anoxic and oxic hydrolyses of rocks containing Fe (II) Mg-silicates and Fe (II)-monosulfides are analyzed at 25 °C and 250-350 °C. A table of the products is drawn. It is shown that magnetite and hydrogen can be produced during low-temperature (25 °C) anoxic hydrolysis/oxidation of ferrous silicates and during high-temperature (250 °C) anoxic hydrolysis/oxidation of ferrous monosulfides. The high-T (350 °C) anoxic hydrolysis of ferrous silicates leads mainly to ferric oxides/hydroxides such as the hydroxide ferric trihydroxide, the oxide hydroxide goethite/lepidocrocite and the oxide hematite, and to Fe(III)-phyllosilicates. Magnetite is not a primary product. While the low-T (25 °C) anoxic hydrolysis of ferrous monosulfides leads to pyrite. Thermodynamic functions are calculated for elementary reactions of hydrolysis and carbonation of olivine and pyroxene and E-pH diagrams are analyzed. It is shown that the hydrolysis of the iron endmember is endothermic and can proceed within the exothermic hydrolysis of the magnesium endmember and also within the exothermic reactions of carbonations. The distinction between three products of the iron hydrolysis, magnetite, goethite and hematite is determined with E-pH diagrams. The hydrolysis/oxidation of the sulfides mackinawite/troilite/pyrrhotite is highly endothermic but can proceed within the heat produced by the exothermic hydrolyses and carbonations of ferromagnesian silicates and also by other sources such as magma, hydrothermal sources, impacts. These theoretical results are confirmed by the products observed in several related laboratory experiments. The case of radiolyzed water is studied. It is shown that magnetite and ferric oxides/hydroxides such as ferric trihydroxide, goethite/lepidocrocite and hematite are formed in oxic hydrolysis of ferromagnesian silicates at 25 °C and 350 °C. Oxic oxidation of ferrous monosulfides at 25 °C leads mainly to pyrite and ferric oxides/hydroxides such as

  8. Hydrolysis of bis(dimethylamido)tin to tin (II) oxyhydroxide and its selective transformation into tin (II) or tin (IV) oxide

    KAUST Repository

    Khanderi, Jayaprakash

    2015-03-01

    Sn6O4(OH)4, a hydrolysis product of Sn(NMe2)2, is transformed to tin (II) or tin (IV) oxide by solid and solution phase processing. Tin (II) oxide is formed by heating Sn6O4(OH)4 at ≤200 °C in air or under inert atmosphere. Tin (IV) oxide nanoparticles are formed in the presence of a carboxylic acid and base in air at room temperature. IR spectroscopy, Raman spectroscopy, thermogravimetry (coupled with infrared spectroscopy), powder X-ray diffraction, high temperature X-ray diffraction, scanning electron and transmission electron microscopy are used for the characterization of Sn6O4(OH)4 and the investigation of its selective decomposition into SnO or SnO2. Spectroscopic and X-ray diffraction results indicate that SnO is formed by the removal of water from crystalline Sn6O4(OH)4. SEM shows octahedral morphology of the Sn6O4(OH)4, SnO and SnO2 with particle size from 400 nm-2 μm during solid state conversion. Solution phase transformation of Sn6O4(OH)4 to SnO2 occurs in the presence of potassium glutarate and oxygen. SnO2 particles are 15-20 nm in size.

  9. Oxidation of cyclic amines by molybdenum(II and tungsten(II halocarbonyls, [M(CO4X2]2 (M = Mo, W; X = Cl, Br

    Directory of Open Access Journals (Sweden)

    H.M. Mbuvi

    2013-05-01

    Full Text Available The molybdenum(II and tungsten(II halocarbonyls, [M(CO4X2]2 (M = Mo, W; X = Cl, Br react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2-ethylpiperidine to give aminecarbonyl complexes of the type M(CO3L3 (L= alkylamine. Excess piperidine reacts with the tungsten halocarbonyls, [W(CO4X2]2 (X = Cl, Br, to give the trans isomer of the complex, W(CO3(C5H11N3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO3(C4H10N22X2 (M = Mo, W; X = Cl, Br. Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry.

  10. CATALYTIC WET PEROXIDE OXIDATION OF HYDROQUINONE WITH Co(II)/ACTIVE CARBON CATALYST LOADED IN STATIC BED

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Catalysts based on Co(II) supported on active carbon were prepared and loaded in static bed. The hydroquinone would be degraded completely after treated by Catalytic wet peroxide oxidation method with Co(II)/active carbon catalyst. After activate treatment, the active carbon was immerged in cobaltous nitrate solution, then put into a drying oven, Co(II) could be loaded on the micro-surface of carbon. Taking the static bed as the equipment, the absorption of active carbon and catalysis of Co(II) was used to reduce activation energy of hydroquinone. Thus hydroquinone could be drastically degraded and the effluent can be drained under the standard. Referring to Fenton reaction mechanism, experiment had been done to study the heterogeneous catalyzed oxidation mechanism of Co(II). The degradation rate of hydroquinone effluent could be achieved to 92% when treated in four columns at H2O2 concentration 10%, reaction temperature 40℃ , pH 5 and reaction time 2.5h.

  11. Nitric oxide and bcl-2 mediated the apoptosis induced by nickel(II) in human T hybridoma cells

    International Nuclear Information System (INIS)

    Guan Fuqin; Zhang Dongmei; Wang Xinchang; Chen Junhui

    2007-01-01

    Although effects of nickel(II) on the immune system have long been recognized, little is known about the effects of nickel(II) on the induction of apoptosis and related signaling events in T cells. In the present study, we investigated the roles and signaling pathways of nickel(II) in the induction of apoptosis in a human T cell line jurkat. The results showed that the cytotoxic effects of Ni involved significant morphological changes and chromosomal condensation (Hoechst 33258 staining). Analyses of hypodiploid cells and FITC-Annexin V and PI double staining showed significant increase of apoptosis in jurkat cells 6, 12 and 24 h after nickel(II) treatment. Flow cytometry analysis also revealed that the loss of mitochondrial membrane potential (MMP) occurred concomitantly with the onset of NiCl 2 -induced apoptosis. Induction of apoptotic cell death by nickel was mediated by reduction of bcl-2 expression. Furthermore, nickel stimulated the generation of nitric oxide (NO). These results suggest that nickel(II) chloride induces jurkat cells apoptosis via nitric oxide generation, mitochondrial depolarization and bcl-2 suppression

  12. Thermal Failure Analysis of Fiber-Reinforced Silica Aerogels under Liquid Nitrogen Thermal Shock

    Directory of Open Access Journals (Sweden)

    Ai Du

    2018-06-01

    Full Text Available Aerogel materials are recognized as promising candidates for the thermal insulator and have achieved great successes for the aerospace applications. However, the harsh environment on the exoplanet, especially for the tremendous temperature difference, tends to affect the tenuous skeleton and performances of the aerogels. In this paper, an evaluation method was proposed to simulate the environment of exoplanet and study the influence on the fiber-reinforced silica aerogels with different supercritical point drying (SPD technology. Thermal conductivity, mechanical property and the microstructure were characterized for understanding the thermal failure mechanism. It was found that structure and thermal property were significantly influenced by the adsorbed water in the aerogels under the thermal shocks. The thermal conductivity of CO2-SPD aerogel increased 35.5% after the first shock and kept in a high value, while that of the ethanol-SPD aerogel increased only 19.5% and kept in a relatively low value. Pore size distribution results showed that after the first shock the peak pore size of the CO2-SPD aerogel increased from 18 nm to 25 nm due to the shrinkage of the skeleton, while the peak pore size of the ethanol-SPD aerogel kept at ~9 nm probably induced by the spring-back effect. An 80 °C treatment under vacuum was demonstrated to be an effective way for retaining the good performance of ethanol-SPD aerogels under the thermal shock. The thermal conductivity increases of the ethanol-SPD aerogels after 5 shocks decreased from ~30 to ~0% via vacuum drying, while the increase of the CO2-SPD aerogels via the same treatments remains ~28%. The high-strain hardening and low-strain soften behaviors further demonstrated the skeleton shrinkage of the CO2-SPD aerogel.

  13. Comparative study of the influence of antimony oxide additives (III) and nickel hydroxide (II) on electrochemical behavior of cadmium electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kadnikova, N.V.; Lvova, L.A.; Ryabskaya, I.A.

    1983-01-01

    Comparative study of the influence of additives indicated that with partial or complete replacement in the active mass of the cadmium electrode of nickel hydroxide (II) by antimony oxide (III), the electrochemical characteristics do not significantly change. During prolonged storage of charged cadmium electrodes the presence of nickel hydroxide (II) and intermetal compound (IMC) of cadmium with nickel is formed and the specific surface increases. In the case of adding antimony (III) formation of noticeable quantities of IMC of cadmium with antimony is not observed. The specific surface is reduced during storage.

  14. SINTESIS SILIKA AEROGEL DENGAN BAHAN DASAR ABU BAGASSE

    Directory of Open Access Journals (Sweden)

    Nazriati Nazriati

    2012-05-01

    Full Text Available SYNTHESIS OF SILICA AEROGEL FROM BAGASSE ASH. Synthesis of silica aerogel from bagasse ash was done by alkaline extraction followed by sol-gel. Bagasse ash was extracted with NaOH at its boiling temperature for one hour with continue stirring, to produce sodium silicate. Subsequently, sodium silicate was pass through ionic exchanger resin, to produces silicic acid (SA. Silicic acid solution was then added with TMCS and HMDS as surface modifier agent. In order to form gel pH must be adjusted to final pH of 8-9 by addition of NH4OH solution. The resulting gel then was aged and dried at ambient pressure and at a certain time and temperature. Characterization of products was done by measuring its pore volume, surface area, and hydrophobisity (contact angle. TMCS serves as water expeller from the pores and subsequently surface was modified by HMDS and TMCS. HMDS content will linearly increase surface area, pore volume, and the contact angle of the resulting silica aerogel. Characteristics of silica aerogel was generated by varying the composition of the SA:TMCS:HMDS resulting has a surface area of 50-488 m2/g, pore volume from 0.2 to 0.9 m3 /g, the contact angle of 48-119 and pore diameter ranging from 5.7-22.56 nm. Based on the resulting pore diameter, the synthesized of silica aerogel categorized as mesoporous.      Abstrak   Sintesis silika aerogel dari bahan dasar abu bagasse dilakukan dengan ekstraksi basa dan diikuti dengan sol-gel. Abu bagasse diekstrak dengan NaOH pada suhu didihnya sambil diaduk selama satu jam, menghasilkan sodium silikat. Selanjutnya, sodium silikat dilewatkan resin penukar ion, menghasilkan asam silicic (SA. Larutan asam silicic kemudian ditambahkan trimethy­l­chlorosilane (TMCS dan hexamethyldisilazane (HMDS sebagai agen pemodifikasi permukaan. Untuk terjadinya gel pH diatur hingga mencapai 8-9 dengan penambahan larutan NH4OH. Gel yang dihasilkan kemudian di-aging dan dikeringkan pada tekanan ambien pada suhu dan

  15. Structural properties and adsorption capacity of holocellulose aerogels synthesized from an alkali hydroxide-urea solution

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Gu-Joong; Kim, Dae-Young; Hwang, Jae-Hyun; Kang, Joo-Hyon [Dongguk University, Seoul (Korea, Republic of)

    2014-05-15

    A tulip tree was used to synthesize a holocellulose aerogel from an aqueous alkali hydroxide-urea solution with the substitution of an organic solvent followed by freeze-drying. For comparison, the synthesized holocellulose aerogels were divided into two groups according to the source of the hydrogel, an upper suspended layer and a bottom concentrated layer of the centrifuged solution of cellulose and NaOH/urea solvents. We investigated the effects of the temperature of the pre-cooled NaOH/urea solution (i.e., dissolution temperature) on the pore structure and the adsorption capacity of the holocellulose aerogel. A nano-fibrillar network structure of the holocellulose aerogel was observed, with little morphological difference in pore structure for different dissolution temperatures. Both micropores and mesopores were observed in the holocellulose aerogel. The specific surface area of the holocellulose aerogel was generally greater at lower dissolution temperatures. In a series of adsorption tests using methylene blue, the holocellulose aerogel showed the greatest adsorption capacity at the lowest dissolution temperature tested ( -2 .deg. C). However, the dissolution temperature generally had little effect on the adsorption capacity. The holocellulose aerogel produced from the upper suspended layer of the centrifuged hydrogel solution showed a greater porosity and adsorption capacity than the one produced from the bottom concentrated layer. Overall, the aerogel made by utilizing a delignified tulip tree display a high surface area and a high adsorption property, indicating its possible application in eco-friendly adsorption materials.

  16. Structural properties and adsorption capacity of holocellulose aerogels synthesized from an alkali hydroxide-urea solution

    International Nuclear Information System (INIS)

    Kwon, Gu-Joong; Kim, Dae-Young; Hwang, Jae-Hyun; Kang, Joo-Hyon

    2014-01-01

    A tulip tree was used to synthesize a holocellulose aerogel from an aqueous alkali hydroxide-urea solution with the substitution of an organic solvent followed by freeze-drying. For comparison, the synthesized holocellulose aerogels were divided into two groups according to the source of the hydrogel, an upper suspended layer and a bottom concentrated layer of the centrifuged solution of cellulose and NaOH/urea solvents. We investigated the effects of the temperature of the pre-cooled NaOH/urea solution (i.e., dissolution temperature) on the pore structure and the adsorption capacity of the holocellulose aerogel. A nano-fibrillar network structure of the holocellulose aerogel was observed, with little morphological difference in pore structure for different dissolution temperatures. Both micropores and mesopores were observed in the holocellulose aerogel. The specific surface area of the holocellulose aerogel was generally greater at lower dissolution temperatures. In a series of adsorption tests using methylene blue, the holocellulose aerogel showed the greatest adsorption capacity at the lowest dissolution temperature tested ( -2 .deg. C). However, the dissolution temperature generally had little effect on the adsorption capacity. The holocellulose aerogel produced from the upper suspended layer of the centrifuged hydrogel solution showed a greater porosity and adsorption capacity than the one produced from the bottom concentrated layer. Overall, the aerogel made by utilizing a delignified tulip tree display a high surface area and a high adsorption property, indicating its possible application in eco-friendly adsorption materials.

  17. The effect of Ca2+ ions and ionic strength on Mn(II) oxidation by spores of the marine Bacillus sp. SG-1

    Science.gov (United States)

    Toyoda, Kazuhiro; Tebo, Bradley M.

    2013-01-01

    Manganese(IV) oxides, believed to form primarily through microbial activities, are extremely important mineral phases in marine environments where they scavenge a variety of trace elements and thereby control their distributions. The presence of various ions common in seawater are known to influence Mn oxide mineralogy yet little is known about the effect of these ions on the kinetics of bacterial Mn(II) oxidation and Mn oxide formation. We examined factors affecting bacterial Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1 in natural and artificial seawater of varying ionic conditions. Ca2+ concentration dramatically affected Mn(II) oxidation, while Mg2+, Sr2+, K+, Na+ and NO3- ions had no effect. The rate of Mn(II) oxidation at 10 mM Ca2+ (seawater composition) was four or five times that without Ca2+. The relationship between Ca2+ content and oxidation rate demonstrates that the equilibrium constant is small (on the order of 0.1) and the binding coefficient is 0.5. The pH optimum for Mn(II) oxidation changed depending on the amount of Ca2+ present, suggesting that Ca2+ exerts a direct effect on the enzyme perhaps as a stabilizing bridge between polypeptide components. We also examined the effect of varying concentrations of NaCl or KNO3 (0-2000 mM) on the kinetics of Mn(II) oxidation in solutions containing 10 mM Ca2+. Mn(II) oxidation was unaffected by changes in ionic strength (I) below 0.2, but it was inhibited by increasing salt concentrations above this value. Our results suggest that the critical coagulation concentration is around 200 mM of salt (I = ca. 0.2), and that the ionic strength of seawater (I > 0.2) accelerates the precipitation of Mn oxides around the spores. Under these conditions, the aggregation of Mn oxides reduces the supply of dissolved O2 and/or Mn2+ and inhibits the Mn(II) → Mn(III) step controlling the enzymatic oxidation of Mn(II). Our results suggest that the hardness and ionic strength of the aquatic environment

  18. Genetic Targeting of Arginase-II in Mouse Prevents Renal Oxidative Stress and Inflammation in Diet-Induced Obesity.

    Science.gov (United States)

    Huang, Ji; Rajapakse, Angana; Xiong, Yuyan; Montani, Jean-Pierre; Verrey, François; Ming, Xiu-Fen; Yang, Zhihong

    2016-01-01

    Obesity is associated with development and progression of chronic kidney disease (CKD). Recent evidence demonstrates that enhanced levels of the L-arginine:ureahydrolase, including the two isoenzymes arginase-I (Arg-I) and arginase-II (Arg-II) in vascular endothelial cells promote uncoupling of endothelial nitric oxide synthase (eNOS), leading to increased superoxide radical anion and decreased NO production thereby endothelial dysfunction. Arg-II but not Arg-I is abundantly expressed in kidney and the role of Arg-II in CKD is uncertain and controversial. We aimed to investigate the role of Arg-II in renal damage associated with diet-induced obesity mouse model. Wild type (WT) C57BL/6 mice and mice deficient in Arg-II gene (Arg-II -/- ) were fed with either a normal chow (NC) or a high-fat-diet (HFD) for 14 weeks (starting at the age of 7 weeks) to induce obesity. In WT mice, HFD feeding caused frequent renal lipid accumulation, enhancement of renal reactive oxygen species (ROS) levels which could be attenuated by a NOS inhibitor, suggesting uncoupling of NOS in kidney. HFD feeding also significantly augmented renal Arg-II expression and activity. All the alterations in the kidney under HFD feeding were reduced in Arg-II -/- mice. Moreover, mesangial expansion as analyzed by Periodic Acid Schiff (PAS) staining and renal expression of vascular adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) in HFD-fed WT mouse assessed by immunoblotting were reduced in the HFD-fed Arg-II -/- mice, although there was no significant difference in body weight and renal weight/body weight ratio between the WT and Arg-II -/- mice. Thus, Arg-II expression/activity is enhanced in kidney of diet-induced obesity mice. Genetic targeting of Arg-II prevents renal damage associated with obesity, suggesting an important role of Arg-II in obesity-associated renal disease development.

  19. Genetic Targeting of Arginase-II in Mouse Prevents Renal Oxidative Stress and Inflammation in Diet-Induced Obesity

    Directory of Open Access Journals (Sweden)

    Ji Huang

    2016-11-01

    Full Text Available Obesity is associated with development and progression of chronic kidney disease (CKD. Recent evidence demonstrates that enhanced levels of the L-arginine:ureahydrolase, including the two isoenzymes arginase-I (Arg-I and arginase-II (Arg-II in vascular endothelial cells promote uncoupling of endothelial nitric oxide synthase (eNOS, leading to increased superoxide radical anion and decreased NO production thereby endothelial dysfunction. Arg-II but not Arg-I is abundantly expressed in kidney and the role of Arg-II in CKD is uncertain and controversial. We aimed to investigate the role of Arg-II in renal damage associated with diet-induced obesity mouse model. Wild type (WT C57BL/6 mice and mice deficient in Arg-II gene (Arg-II-/- were fed with either a normal chow (NC or a high-fat-diet (HFD for 14 weeks (starting at the age of 7 weeks to induce obesity. In WT mice, HFD feeding caused frequent renal lipid accumulation, enhancement of renal ROS levels which could be attenuated by a NOS inhibitor, suggesting uncoupling of NOS in kidney. HFD feeding also significantly augmented renal Arg-II expression and activity. All the alterations in the kidney under HFD feeding were reduced in Arg-II-/- mice. Moreover, mesangial expansion as analysed by Periodic Acid Schiff (PAS staining and renal expression of vascular adhesion molecule-1 (VCAM-1 and intercellular adhesion molecule-1 (ICAM-1 in HFD-fed WT mouse assessed by immunoblotting were reduced in the HFD-fed Arg-II-/- mice, although there was no significant difference in body weight and renal weight/body weight ratio between the WT and Arg-II-/- mice. Thus, Arg-II expression/activity is enhanced in kidney of diet-induced obesity mice. Genetic targeting of Arg-II prevents renal damage associated with obesity, suggesting an important role of Arg-II in obesity-associated renal disease development.

  20. Amidines for versatile ruthenium(II)-catalyzed oxidative C-H activations with internal alkynes and acrylates.

    Science.gov (United States)

    Li, Jie; John, Michael; Ackermann, Lutz

    2014-04-25

    Cationic ruthenium complexes derived from KPF6 or AgOAc enabled efficient oxidative CH functionalizations on aryl and heteroaryl amidines. Thus, oxidative annulations of diversely decorated internal alkynes provided expedient access to 1-aminoisoquinolines, while catalyzed C-H activations with substituted acrylates gave rise to structurally novel 1-iminoisoindolines. The powerful ruthenium(II) catalysts displayed a remarkably high site-, regio- and, chemoselectivity. Therefore, the catalytic system proved tolerant of a variety of important electrophilic functional groups. Detailed mechanistic studies provided strong support for the cationic ruthenium(II) catalysts to operate by a facile, reversible C-H activation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Particulate air pollution induces arrhythmia via oxidative stress and calcium calmodulin kinase II activation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin-Bae [The Division of Cardiology, Kyung Hee University College of Medicine, 1 Hoegi-dong, Dongdaemun-Gu, Seoul (Korea, Republic of); Kim, Changsoo [The Department of Preventive Medicine, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); Choi, Eunmi [Cardiovascular Research Institute and Severance Biomedical Science Institute, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); Park, Sanghoon; Park, Hyelim; Pak, Hui-Nam; Lee, Moon-Hyoung [The Division of Cardiology, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); Shin, Dong Chun [The Department of Preventive Medicine, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); Hwang, Ki-Chul [Cardiovascular Research Institute and Severance Biomedical Science Institute, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); The Division of Cardiology, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of); Joung, Boyoung, E-mail: cby6908@yuhs.ac [The Division of Cardiology, Yonsei University College of Medicine, 250 Seungsanno, Seodaemun-gu, Seoul (Korea, Republic of)

    2012-02-15

    Ambient particulate matter (PM) can increase the incidence of arrhythmia. However, the arrhythmogenic mechanism of PM is poorly understood. This study investigated the arrhythmogenic mechanism of PM. In Sprague–Dawley rats, QT interval was increased from 115.0 ± 14.0 to 142.1 ± 18.4 ms (p = 0.02) after endotracheal exposure of DEP (200 μg/ml for 30 min, n = 5). Ventricular premature contractions were more frequently observed after DEP exposure (100%) than baseline (20%, p = 0.04). These effects were prevented by pretreatment of N-acetylcysteine (NAC, 5 mmol/L, n = 3). In 12 Langendorff-perfused rat hearts, DEP infusion of 12.5 μg/ml for 20 min prolonged action potential duration (APD) at only left ventricular base increasing apicobasal repolarization gradients. Spontaneous early afterdepolarization (EAD) and ventricular tachycardia (VT) were observed in 8 (67%) and 6 (50%) hearts, respectively, versus no spontaneous triggered activity or VT in any hearts before DEP infusion. DEP-induced APD prolongation, EAD and VT were successfully prevented with NAC (5 mmol/L, n = 5), nifedipine (10 μmol/L, n = 5), and active Ca{sup 2+}/calmodulin-dependent protein kinase II (CaMKII) blockade, KN 93 (1 μmol/L, n = 5), but not by thapsigargin (200 nmol/L) plus ryanodine (10 μmol/L, n = 5) and inactive CaMKII blockade, KN 92 (1 μmol/L, n = 5). In neonatal rat cardiomyocytes, DEP provoked ROS generation in dose dependant manner. DEP (12.5 μg/ml) induced apoptosis, and this effect was prevented by NAC and KN 93. Thus, this study shows that in vivo and vitro exposure of PM induced APD prolongation, EAD and ventricular arrhythmia. These effects might be caused by oxidative stress and CaMKII activation. -- Highlights: ► The ambient PM consistently prolonged repolarization. ► The ambient PM induced triggered activity and ventricular arrhythmia. ► These effects were prevented by antioxidants, I{sub CaL} blockade and CaMKII blockade. ► The ambient PM can induce

  2. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Wenchuan [Univ. of California, Berkeley, CA (United States)

    1994-11-01

    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S2 state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S2 state with the g~4 electron paramagnetic resonance (EPR) signal (S2-g4 state) was compared with that in the S2 state with multiline signal (S2-MLS state) and the S1 state. The S2-g4 state has a higher XAS inflection point energy than that of the S1 state, indicating the oxidation of Mn in the advance from the S1 to the S2-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S2-g4 state is different from that in the S2-MLS or the S1 state. In the S2-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 Å and 2.85 Å. Very little distance disorder exists in the second shell of the S1 or S2-MLS states. The third shell of the S2-g4 state at about 3.3 Å also contains increased heterogeneity relative to that of the S2-MLS or the S1 state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct "pure" S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S1 → S2 transition.

  3. Continuous adsorption of Pb(II) and methylene blue by engineered graphite oxide coated sand in fixed-bed column

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Ji-Lai, E-mail: jilaigong@gmail.com [College of Environmental Science and Engineering, Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082 (China); Zhang, Yong-Liang; Jiang, Yan [College of Environmental Science and Engineering, Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082 (China); Zeng, Guang-Ming, E-mail: zgming@hnu.edu.cn [College of Environmental Science and Engineering, Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082 (China); Cui, Zhi-Hui; Liu, Ke; Deng, Can-Hui; Niu, Qiu-Ya; Deng, Jiu-Hua [College of Environmental Science and Engineering, Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082 (China); Huan, Shuang-Yan [State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)

    2015-03-01

    Highlights: • GO-sand was prepared by coating GO on the surface of sand. • Pb(II) and MB were efficiently removed by GO-sand filter in column. • The removal of MB was enhanced with the presence of Pb(II). • GO-sand is low-cost and convenient for its application as packed bed filter. - Abstract: The mixture of several effluents, caused by the improper handling and management of effluents, generated multi-component wastewater containing both metals and dyes, leading to the complicated treatment process. In this study, a continuous adsorption of Pb(II) and methylene blue (MB) has been studied in single and binary solutions by using graphite oxide coated sand (GO-sand) as an adsorbent in a fixed-bed column. GO-sand was analyzed by X-ray photoelectron spectroscopy before and after analyte adsorption. Compared with sand filter, adsorption quantity and capacity for Pb(II) and MB by GO-sand filter were greatly increased. In Pb(II) and MB single solutions, the experimental parameters were investigated in detail including initial concentration, flow rate, bed depth and pH. Exhaustion time decreased with increasing initial concentration and flow rate, and increased with increasing bed depth and pH. In the Pb(II)-MB binary solution, exhaustion time significantly decreased for Pb(II) adsorption, but increased for MB adsorption. The reason was explained that the more favorable adsorption for MB onto the surface of GO-sand than that for Pb(II), which was derived from π–π interaction between MB and GO on sand surface in packed filter. The Yoon–Nelson model was applied at different concentration of Pb(II) and MB to predict the breakthrough curves. The experimental data were well fit with the model indicating that it was suitable for this column design.

  4. Protection of Nitrate-Reducing Fe(II)-Oxidizing Bacteria from UV Radiation by Biogenic Fe(III) Minerals

    Science.gov (United States)

    Gauger, Tina; Konhauser, Kurt; Kappler, Andreas

    2016-04-01

    Due to the lack of an ozone layer in the Archean, ultraviolet radiation (UVR) reached early Earth's surface almost unattenuated; as a consequence, a terrestrial biosphere in the form of biological soil crusts would have been highly susceptible to lethal doses of irradiation. However, a self-produced external screen in the form of nanoparticular Fe(III) minerals could have effectively protected those early microorganisms. In this study, we use viability studies by quantifying colony-forming units (CFUs), as well as Fe(II) oxidation and nitrate reduction rates, to show that encrustation in biogenic and abiogenic Fe(III) minerals can protect a common soil bacteria such as the nitrate-reducing Fe(II)-oxidizing microorganisms Acidovorax sp. strain BoFeN1 and strain 2AN from harmful UVC radiation. Analysis of DNA damage by quantifying cyclobutane pyrimidine dimers (CPD) confirmed the protecting effect by Fe(III) minerals. This study suggests that Fe(II)-oxidizing microorganisms, as would have grown in association with mafic and ultramafic soils/outcrops, would have been able to produce their own UV screen, enabling them to live in terrestrial habitats on early Earth.

  5. Mobilization of manganese by basalt associated Mn(II)-oxidizing bacteria from the Indian Ridge System

    Digital Repository Service at National Institute of Oceanography (India)

    Sujith, P.P.; Mourya, B.S.; Krishnamurthi, S.; Meena, R.M.; LokaBharathi, P.A.

    The Indian Ridge System basalt bearing Mn-oxide coatings had todorokite as the major and birnesite as the minor mineral. We posit that microorganisms associated with these basalts participate in the oxidation of Mn and contribute to mineral...

  6. Fabrication of the tea saponin functionalized reduced graphene oxide for fast adsorptive removal of Cd(II) from water

    Science.gov (United States)

    Li, Zhigang; Liu, Zhifeng; Wu, Zhibin; Zeng, Guangming; Shao, Binbin; Liu, Yujie; Jiang, Yilin; Zhong, Hua; Liu, Yang

    2018-05-01

    A novel graphene-based material of tea saponin functionalized reduced graphene oxide (TS-RGO) was synthesized via a facil thermal method, and it was characterized as the absorbent for Cd(II) removal from aqueous solutions. The factors on adsorption process including solution pH, contact time, initial concentration of Cd(II) and background electrolyte cations were studied to optimize the conditions for maximum adsorption at room temperature. The results indicated that Cd(II) adsorption was strongly dependent on pH and could be strongly affected by background electrolytes and ionic strength. The optimal pH and required equilibrium time was 6.0 and 10 min, respectively. The Cd(II) removal decreased with the presence of background electrolyte cations (Na+ < Ca2+ < Al3+). The adsorption kinetics of Cd(II) followed well with the pseudo-second-order model. The adsorption isotherm fitted well to the Langmuir model, indicating that the adsorption was a monolayer adsorption process occurred on the homogeneous surfaces of TS-RGO. The maximum monolayer adsorption capacity was 127 mg/g at 313 K and pH 6.0. Therefore, the TS-RGO was considered to be a cost-effective and promising material for the removal of Cd(II) from wastewater.

  7. Fe biomineralization mirrors individual metabolic activity in a nitrate-dependent Fe(II-oxidizer

    Directory of Open Access Journals (Sweden)

    Jennyfer eMIOT

    2015-09-01

    Full Text Available Microbial biomineralization sometimes leads to periplasmic encrustation, which is predicted to enhance microorganism preservation in the fossil record. Mineral precipitation within the periplasm is however thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall. This hypothesis had however never been investigated down to the single cell level. Here, we cultured the nitrate reducing Fe(II oxidizing bacteria Acidovorax sp. strain BoFeN1 that have been previously shown to promote the precipitation of a diversity of Fe minerals (lepidocrocite, goethite, Fe phosphate encrusting the periplasm. We investigated the connection of Fe biomineralization with carbon assimilation at the single cell level, using a combination of electron microscopy and Nano-Secondary Ion Mass Spectrometry (NanoSIMS. Our analyses revealed strong individual heterogeneities of Fe biomineralization. Noteworthy, a small proportion of cells remaining free of any precipitate persisted even at advanced stages of biomineralization. Using pulse chase experiments with 13C-acetate, we provide evidences of individual phenotypic heterogeneities of carbon assimilation, correlated with the level of Fe biomineralization. Whereas non- and moderately encrusted cells were able to assimilate acetate, higher levels of periplasm encrustation prevented any carbon incorporation. Carbon assimilation only depended on the level of Fe encrustation and not on the nature of Fe minerals precipitated in the cell wall. Carbon assimilation decreased exponentially with increasing cell-associated Fe content. Persistence of a small proportion of non-mineralized and metabolically active cells might constitute a strategy of survival in highly ferruginous environments. Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern

  8. Structural, magnetic and electronic properties of rare earth ternary oxides Li Ln(II) 2 Ln(III)O4

    International Nuclear Information System (INIS)

    Malki, M.

    1987-06-01

    Properties of a new class of rare earth ternary oxides Li Ln(II) 2 Ln(III)O 4 where Ln(II) is a divalent metal (Sr, Eu) and Ln(III) a trivalent rare earth (Eu, Gd, Dy, Er and Y). These orthorhombic compounds (type Li Eu 3 O 4 ) allow the study of many magnetic phenomena and their evolution in function of the nature of Ln(II) and Ln(III): diamagnetic ions Sr 2+ , Y 3+ ; isotrope magnetic ions: Eu 2+ , Gd 3+ and anisotrope magnetic ions Dy 3+ , Er 3+ . Magnetic and electric properties are obtained by classical techniques and from hyperfine interaction by Moessbauer spectroscopy. The possibility to use several Moessbauer resonance (nuclei Eu 151, Gd 155, Dy 161 and Er 166) completes informations obtained by the macroscopic study [fr

  9. Iron(III) species formed during iron(II) oxidation and iron-core formation in bacterioferritin of Escherichia coli

    International Nuclear Information System (INIS)

    Hawkins, C.; Treffry, A.; Mackey, J.; Williams, J.M.; Andrews, S.C.; Guest, J.R.; Harrison, P.M.

    1996-01-01

    This paper describes a preliminary investigation of the mechanisms of Fe(II) oxidation and storage of Fe(III) in the bacterioferritin of Escherichia coli (EcBFR). Using Moessbauer spectroscopy to examine the initial oxidation of iron by EcBFR it is confirmed that this ferritin exhibits 'ferroxidase' activity and is shown that dimeric and monomeric iron species are produced as intermediates. The characteristics of ferroxidase activity in EcBFR is compare d with those of human H-chain ferritin (HuHF) and discuss the different Moessbauer parameters of their dimeric iron with reference to the structures of their di-metal sites. In addition, it is presented preliminary findings suggesting that after an initial 'burst', the rate of oxidation is greatly reduced, possibly due to blockage of the ferroxidase centre by bound iron. A new component, not found in HuHF and probably representing a small cluster of Fe(III) atoms, is reported

  10. Control of the microstructure and surface chemistry of graphene aerogels via pH and time manipulation by a hydrothermal method.

    Science.gov (United States)

    García-Bordejé, E; Víctor-Román, S; Sanahuja-Parejo, O; Benito, A M; Maser, W K

    2018-02-15

    Three-dimensional graphene aerogels of controlled pore size have emerged as an important platform for several applications such as energy storage or oil-water separation. The aerogels of reduced graphene oxide are mouldable and light weight, with a porosity up to 99.9%, consisting mainly of macropores. Graphene aerogel preparation by self-assembly in the liquid phase is a promising strategy due to its tunability and sustainability. For graphene aerogels prepared by a hydrothermal method, it is known that the pH value has an impact on their properties but it is unclear how pH affects the auto-assembly process leading to the final properties. We have monitored the time evolution of the chemical and morphological properties of aerogels as a function of the initial pH value. In the hydrothermal treatment process, the hydrogel is precipitated earlier and with lower oxygen content for basic pH values (∼13 wt% O) than for acidic pH values (∼20 wt% O). Moreover, ∼7 wt% of nitrogen is incorporated on the graphene nanosheets at basic pH generated by NH 3 addition. To our knowledge, there is no precedent showing that the pH value affects the microstructure of graphene nanosheets, which become more twisted and bent for the more intensive deoxygenation occurring at basic pH. The bent nanosheets attained at pH = 11 reduce the stacking by the basal planes and they connect via the borders, hence leading eventually to higher pore volumes. In contrast, the flatter graphene nanosheets attained under acidic pH entail more stacking and higher oxygen content after a long hydrothermal treatment. The gravimetric absorption capacity of non-polar solvents scales directly with the pore volume. The aerogels have proved to be highly selective, recyclable and robust for the absorption of nonpolar solvents in water. The control of the porous structure and surface chemistry by manipulation of pH and time will also pave the way for other applications such as supercapacitors or batteries.

  11. Low dielectric constant and moisture-resistant polyimide aerogels containing trifluoromethyl pendent groups

    Science.gov (United States)

    Wu, Tingting; Dong, Jie; Gan, Feng; Fang, Yuting; Zhao, Xin; Zhang, Qinghua

    2018-05-01

    Conventional polyimide aerogels made from biphenyl-3,3‧,4,4‧-tetracarboxylic dianydride (BPDA) and 4,4‧-oxidianiline (ODA) exhibit poor resistance to moisture and mechanical properties. In this work, a versatile diamine, 2,2‧-bis-(trifluoromethyl)-4,4‧-diaminobiphenyl (TFMB), is introduced to BPDA/ODA backbone to modify the comprehensive performance of this aerogel. Among all formulations, the resulted polyimide aerogels exhibit the lowest shrinkage and density as well as highest porosity, at the ODA/TFMB molar ratio of 5/5. Dielectric constants and loss tangents of the aerogels fall in the range of 1.29-1.33 and 0.001-0.004, respectively, and more TFMB fractions results in a slightly decrease of dielectric constant and loss tangent. In addition, moisture-resistance of the aerogels are dramatically enhanced as the water absorption decreasing from 415% for BPDA/ODA to 13% for the polyimide aerogel at the ODA/TFMB molar ratio of 7/3, and even to 4% for the homo-BPDA/TFMB polyimide aerogel, showing a superhydrophobic characteristic, which is a great advantage for polyimide aerogels used as low dielectric materials. Meanwhile, all of formulations of aerogels exhibit high absorption capacities for oils and common organic solvents, indicating that these fluorinated polyimide aerogels are good candidates for the separation of oils/organic solvents and water. Mechanical properties and thermal stability of the polyimide aerogels are also raised to varying degrees due to the rigid-rod biphenyl structure introduced by TFMB.

  12. Strong-coupling effects in superfluid 3He in aerogel

    International Nuclear Information System (INIS)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2007-01-01

    Effects of impurity scatterings on the strong-coupling (SC) contribution, stabilizing the ABM (axial) pairing state, to the quartic term of the Ginzburg-Landau free energy of superfluid 3 He are theoretically studied to examine recent observations suggestive of an anomalously small SC effect in superfluid 3 He in aerogels. To study the SC corrections, two approaches are used. One is based on a perturbation in the short-range repulsive interaction, and the other is a phenomenological approach used previously for the bulk liquid by Sauls and Serene [Phys. Rev. B 24, 183 (1981)]. It is found that the impurity scattering favors the BW pairing state and shrinks the region of the ABM pairing state in the T-P phase diagram. In the phenomenological approach, the resulting shrinkage of the ABM region is especially substantial and, if assuming an anisotropy over a large scale in aerogel, leads to justifying the phase diagrams determined experimentally

  13. Toll-like receptor 4 (TLR4) impairs nitric oxide contributing to Angiotensin II-induced cavernosal dysfunction.

    Science.gov (United States)

    Nunes, Kenia P; Bomfim, Gisele F; Toque, Haroldo A; Szasz, Theodora; Clinton Webb, R

    2017-12-15

    Angiotensin II (AngII), a corpus cavernosum (CC) constrictor peptide, modulates Toll like receptor (TLR) expression, a key element of the innate immune system, contributing to impaired vascular function in pathological conditions. However, it is unknown whether TLR4 is involved in AngII-induced erectile dysfunction. In this study, we investigated whether TLR4 plays a role in cavernosal dysfunction caused by AngII upregulation. Cavernosal smooth muscle cells (CSMC) from C57/BL6 mice were treated with AngII (0.1μM) or bacterial LPS (50ng/ml) for 12-24h and TLR4 expression was assessed. Mice were infused with AngII (90ng/min, 28days) and treated with anti-TLR4 antibody (0.1mg/daily, i.p.) for the last 14days of the treatment. CC tissue was used for functional studies and for Western blotting. Nitric Oxide Synthase (NOS) activity was measured by conversion of [ 3 H]-l-arginine to [ 3 H]-l-citrulline, systemic TNF-α levels by ELISA, and reactive oxygen species (ROS) by immunofluorescence. We report upregulation of TLR4 in CSMC following AngII or LPS stimulation. In AngII-infused mice, chronic treatment with anti-TLR4 antibody (28±2.1%) attenuates adrenergic CC contraction, which also ameliorates nitrergic (68.90±0.21 vs. 51.07±0.63, 8Hz, AngII-infused mice treated vs. non-treated). Decreased endothelial NOS expression, reduced NOS activity, and augmented levels of TNF-α, and ROS were found following AngII-infusion. These alterations were prevented, or at least decreased by anti-TLR4 antibody treatment. Inhibition of TLR4 ameliorates AngII-impaired cavernosal relaxation, decreases TNF-α levels, and restores NO bioavailability, demonstrating that TLR4 partly mediates AngII-induced cavernosal dysfunction. Copyright © 2017. Published by Elsevier Inc.

  14. The protonation state around TyrD/TyrD• in photosystem II is reflected in its biphasic oxidation kinetics.

    Science.gov (United States)

    Sjöholm, Johannes; Ho, Felix; Ahmadova, Nigar; Brinkert, Katharina; Hammarström, Leif; Mamedov, Fikret; Styring, Stenbjörn

    2017-02-01

    The tyrosine residue D2-Tyr160 (Tyr D ) in photosystem II (PSII) can be oxidized through charge equilibrium with the oxygen evolving complex in PSII. The kinetics of the electron transfer from Tyr D has been followed using time-resolved EPR spectroscopy after triggering the oxidation of pre-reduced Tyr D by a short laser flash. After its oxidation Tyr D is observed as a neutral radical (Tyr D • ) indicating that the oxidation is coupled to a deprotonation event. The redox state of Tyr D was reported to be determined by the two water positions identified in the crystal structure of PSII [Saito et al. (2013) Proc. Natl. Acad. Sci. USA 110, 7690]. To assess the mechanism of the proton coupled electron transfer of Tyr D the oxidation kinetics has been followed in the presence of deuterated buffers, thereby resolving the kinetic isotope effect (KIE) of Tyr D oxidation at different H/D concentrations. Two kinetic phases of Tyr D oxidation - the fast phase (msec-sec time range) and the slow phase (tens of seconds time range) were resolved as was previously reported [Vass and Styring (1991) Biochemistry 30, 830]. In the presence of deuterated buffers the kinetics was significantly slower compared to normal buffers. Furthermore, although the kinetics were faster at both high pH and pD values the observed KIE was found to be similar (~2.4) over the whole pL range investigated. We assign the fast and slow oxidation phases to two populations of PSII centers with different water positions, proximal and distal respectively, and discuss possible deprotonation events in the vicinity of Tyr D . Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Characterization of pH dependent Mn(II) oxidation strategies and formation of a bixbyite-like phase by Mesorhizobium australicum T-G1

    Science.gov (United States)

    Bohu, Tsing; Santelli, Cara M; Akob, Denise M.; Neu, Thomas R; Ciobota, Valerian; Rösch, Petra; Popp, Jürgen; Nietzsche, Sándor; Küsel, Kirsten

    2015-01-01

    Despite the ubiquity of Mn oxides in natural environments, there are only a few observations of biological Mn(II) oxidation at pH < 6. The lack of low pH Mn-oxidizing bacteria (MOB) isolates limits our understanding of how pH influences biological Mn(II) oxidation in extreme environments. Here, we report that a novel MOB isolate, Mesorhizobium australicum strain T-G1, isolated from an acidic and metalliferous uranium mining area, can oxidize Mn(II) at both acidic and neutral pH using different enzymatic pathways. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy revealed that T-G1 initiated bixbyite-like Mn oxide formation at pH 5.5 which coincided with multi-copper oxidase expression from early exponential phase to late stationary phase. In contrast, reactive oxygen species (ROS), particularly superoxide, appeared to be more important for T-G1 mediated Mn(II) oxidation at neutral pH. ROS was produced in parallel with the occurrence of Mn(II) oxidation at pH 7.2 from early stationary phase. Solid phase Mn oxides did not precipitate, which is consistent with the presence of a high amount of H2O2 and lower activity of catalase in the liquid culture at pH 7.2. Our results show that M. australicum T-G1, an acid tolerant MOB, can initiate Mn(II) oxidation by varying its oxidation mechanisms depending on the pH and may play an important role in low pH manganese biogeochemical cycling.

  16. Characterization of pH dependent Mn(II oxidation strategies and formation of a bixbyite-like phase by Mesorhizobium australicum T-G1

    Directory of Open Access Journals (Sweden)

    Tsing eBohu

    2015-07-01

    Full Text Available Despite the ubiquity of Mn oxides in natural environments, there are only a few observations of biological Mn(II oxidation at pH < 6. The lack of low pH Mn-oxidizing bacteria (MOB isolates limits our understanding of how pH influences biological Mn(II oxidation in extreme environments. Here, we report that a novel MOB isolate, Mesorhizobium australicum strain T-G1, isolated from an acidic and metalliferous uranium mining area, can oxidize Mn(II at both acidic and neutral pH using different enzymatic pathways. X-ray diffraction (XRD, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS revealed that T-G1 initiated bixbyite-like Mn oxide formation at pH 5.5 which coincided with multi-copper oxidase (MCO expression from early exponential phase to late stationary phase. In contrast, reactive oxygen species (ROS, particularly superoxide, appeared to be more important for T-G1 mediated Mn(II oxidation at neutral pH. ROS was produced in parallel with the occurrence of Mn(II oxidation at pH 7.2 from early stationary phase. Solid phase Mn oxides did not precipitate, which is consistent with the presence of a high amount of H2O2 and lower activity of catalase in the liquid culture at pH 7.2. Our results show that M. australicum T-G1, an acid tolerant MOB, can initiate Mn(II oxidation by varying its oxidation mechanisms depending on the pH and may play an important role in low pH manganese biogeochemical cycling.

  17. Theoretical and experimental investigation of REB interaction with aerogel targets

    Energy Technology Data Exchange (ETDEWEB)

    Efremov, V P; Fortov, V E [Russian Academy of scinces, Moscow (Russian Federation). High Energy Density Research Center; Demidov, B A; Ivonin, I A [Kurchatov Institute, Moscow (Russian Federation); Vorobev, O Yu [Institute of Chemical Physics, Chernogolovka (Russian Federation); Keeler, N

    1997-12-31

    Recent results of luminosity measurements of aerogel targets (with a density about 0.36 g/cc) irradiated with `KALMAR` beam are reported. The beam current was varied within the range of 10-20 kA, the pulse duration was 80-120 ns and the electron energy was from 200 keV to 290 keV. Absorbed energy distribution in the deposition zone was compared with the results of calculations. (author). 4 figs., 4 refs.

  18. Novel retrofit technologies incorporating silica aerogel for lower energy buildings

    OpenAIRE

    Dowson, Mark

    2012-01-01

    This thesis was submitted for the degree of Doctor of Engineering and was awarded by Brunel University. The aim of this Engineering Doctorate is to design, build and test novel environmental retrofit technologies to reduce energy consumption in existing buildings. Three contributions to knowledge are documented. The first contribution is the technical verification of a novel proof-of-principle prototype incorporating translucent silica aerogel granules to improve the thermal performance of...

  19. Emissions of Fe(II) and its kinetic of oxidation at Tagoro submarine volcano, El Hierro (Canary Islands)

    Science.gov (United States)

    González-Dávila, M.; Santana-González, C.; Santana-Casiano, J. M.

    2017-12-01

    The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Island of El Hierro (Canary Island) and the subsequent degasification stage, five months later, have increased the concentration of TdFe(II) (Total dissolved iron(II)) in the waters nearest to the volcanic edifice. In order to detect any variation in concentrations of TdFe(II) due to hydrothermal emissions, three cruises were carried out two years after the eruptive process in October 2013, March 2014, May 2015, March 2016 and November 2016. The results from these cruises confirmed important positive anomalies in TdFe(II), which coincided with negatives anomalies in pHF,is (pH in free scale, at in situ conditions) located in the proximity of the main cone. Maximum values in TdFe(II) both at the surface, associated to chlorophyll a maximum, and at the sea bottom, were also observed, showing the important influence of organic complexation and particle re-suspension processes. Temporal variability studies were carried out over periods ranging from hours to days in the stations located over the main and two secondary cones in the volcanic edifice with positive anomalies in TdFe(II) concentrations and negative anomalies in pHF,is values. Observations showed an important variability in both pHF,is and TdFe(II) concentrations, which indicated the volcanic area was affected by a degasification process that remained in the volcano after the eruptive phase had ceased. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t1/2 (half-life time) of ferrous iron. The increased TdFe(II) concentrations and the low associated pHF,is values acted as an important fertilization event in the seawater around the Tagoro volcano at the Island of El Hierro providing optimal conditions for the regeneration of the area.

  20. Seasonal variability of oxidative stress markers in city bus drivers – Part II: Oxidative damage to lipids and proteins

    Czech Academy of Sciences Publication Activity Database

    Rössner ml., Pavel; Švecová, Vlasta; Milcová, Alena; Lněničková, Zdena; Solanský, I.; Šrám, Radim

    2008-01-01

    Roč. 642, 1-2 (2008), s. 21-27 ISSN 0027-5107 R&D Projects: GA MŽP SL/5/160/05 Institutional research plan: CEZ:AV0Z50390512 Keywords : Air pollution * Oxidative stress * Bus drivers Subject RIV: DN - Health Impact of the Environment Quality Impact factor: 3.198, year: 2008

  1. Acute Urinary Bladder Distension Triggers ICAM-1-mediated Renal Oxidative Injury via the Norepinephrine–renin–angiotensin II System in Rats

    Directory of Open Access Journals (Sweden)

    Show-Shing Chen

    2009-08-01

    Conclusion: Acute urinary retention enhances renal sympathetic activity, which causes renal vasoconstriction and increases oxidative stress, adhesion-molecule expression and leukocyte infiltration in the rat kidney via the angiotensin II type 1 receptor pathway.

  2. THE EFFECT OF WATER CAPACITY ON THE ACTIVITY OF PD(II-CU(II CATALYST ANCHORED TO ACID-MODIFIED CLINOPTILOLITE IN THE REACTION OF LOW-TEMPERATURE CARBON MONOXIDE OXIDATION

    Directory of Open Access Journals (Sweden)

    T. L. Rakitskaya

    2015-02-01

    Full Text Available The maximum activity of Pd(II-Cu(II catalyst anchored to acid modified clinoptilolite in the reaction of low-temperature carbon monoxide oxidation with air oxygen has been found at the water content in the range from 3.3 to 4.2 mmol/g.

  3. Effect of process parameters on removal and recovery of Cd(II) and Cu(II) from electroplating wastewater by fixed-bed column of nano-dimensional titanium (IV) oxide agglomerates

    CSIR Research Space (South Africa)

    Debnath, S

    2014-01-01

    Full Text Available Removal performances of Cd(II) and Cu(II) from water was investigated using agglomerated nanoparticle of hydrous titanium(IV) oxide (NTO) packed fixed bed. The parameters varied were the bed depth, flow rate and feed solution concentrations...

  4. Particle detection and identification through Cerenkov effect in silica aerogels

    International Nuclear Information System (INIS)

    Engelmann, J.J.; Cantin, M.

    1978-01-01

    Cerenkov counters are largely used in high energy physics and in nuclear astrophysics to identify the charge of high energy particles and to measure their velocity. Good velocity resolution is obtained only near the Cerenkov threshold, which is directly dependent on the refractive index of the radiator. It is therefore very important to dispose of materials of various refractive indices. The silica aerogel allows to cover a range of indices between 1.015 and 1.2 which is intermediate between the indices given by gas and liquids. The samples most often built until now are hexagonal blocks of 1.06 refractive index and 0.24 g/cm 3 density. Blocks of one liter in volume have been assembled to form a mosaic of large dimension. For lower refractive indices, 1.015 for instance, the material becomes too brittle. So we have been led to use an aerogel sand made of aerogel grains of controlled granulometry. Radiators of both types blocks and sand are used in the franco-danish experiment to be launched aboard the NASA satellite HEAO-C in July 1979 [fr

  5. Oxidation of Cu(II) aminopolycarboxylates by carbonate radical. A flash photolysis study

    International Nuclear Information System (INIS)

    Mandal, P.C.; Bardhan, D.K.

    1999-01-01

    Reactions of carbonate radical (CO 3 -. ) generated by photolysis or by radiolysis of a carbonate solution, with Cu(II) complexes of aminopolycarboxylic acids viz., Cu(II)ethylenediamine tetraacetate [Cu II EDTA] 2- and Cu(II)-iminodiacetate [Cu II IDA] were studied at pH 10.5 and ionic strength 0.2 mol x dm -3 . Time-resolved spectroscopy and kinetics for the transients were studied using flash photolysis and stable products arising from the ligand degradation of the complex were ascertained by steady-state radiolysis experiments. From the kinetic data it is observed that CO 3 -. radical reacts initially with Cu II -complex to form a transient intermediate having maximum absorption at 335 nm and 430 nm. From the subsequent reactions of this intermediate it was assigned to be Cu III .species. This Cu(III) species undergoes intermolecular electron transfer with the Cu II -complex to give a radical intermediate which again slowly reacts with Cu II -complex to give a long lived species containing Cu-C bond. This long lived species, however, slowly decomposed to give glyoxalic reaction between Cu III -complex and a suitable donor, the one electron reduction potential for [Cu III EDTA] 1- /[Cu II EDTA] 2- and [Cu III IDA] +1 /Cu II IDA was determined. (author)

  6. Ultrasonic synthesis of two new zinc(II) bipyridine coordination polymers: New precursors for preparation of zinc(II) oxide nano-particles.

    Science.gov (United States)

    Fard, Mohammad Jaafar Soltanian; Hayati, Payam; Firoozadeh, Azita; Janczak, Jan

    2017-03-01

    Nanoparticles of two zinc(II) coordination polymers (CPs), [Zn(μ-4,4'-bipy)Cl 2 ] n (1) and [Zn(μ-4,4'-bipy)Br 2 ] n (2) L=bpy=4,4'-bipyridine ligand, have been synthesized by use of a sonochemical process and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) spectroscopy and elemental analyses. The single crystal X-ray data of compounds 1 and 2 imply that the Zn +2 ions are four coordinated. Topological analysis shows that 1D coordination networks of 1 and 2 can be classified as underlying nets of topological types 2C1. Nanoparticles of zinc(II) oxide have been prepared by calcination of two different zinc (II) CPs at 450°C that were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and IR spectroscopy. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Amino siloxane oligomer-linked graphene oxide as an efficient adsorbent for removal of Pb(II) from wastewater

    International Nuclear Information System (INIS)

    Luo, Shenglian; Xu, Xiangli; Zhou, Guiyin; Liu, Chengbin; Tang, Yanhong; Liu, Yutang

    2014-01-01

    Graphical abstract: A high performance sorbent, oligomer-linked graphene oxide, was prepared by using oligomeric poly3-aminopropyltriethoxysilane as crosslinking agents. The sorbent could selectively remove Pb(II) with high adsorption capacity. - Highlights: • Oligomer-linked graphene oxide sharply fattened function groups. • The sorbent exhibited high adsorption capacity toward Pb(II). • Pb, Cu and Fe were selectively removed from smelter industrial effluent. • The sorption could be conducted at a wide pH range of about 4.0–7.0. - Abstract: A high performance sorbent, oligomer-linked graphene oxide (GO) composite, was prepared through simple cross-linking reactions between GO sheets and poly3-aminopropyltriethoxysilane (PAS) oligomers as crosslinking agents. The three-dimensional PAS oligomers prevented GO sheets from aggregation, provided foreign molecules with easier access, and introduced a large amount of amino functional groups. The morphology, structure and property of the PAS-GO composite were determined by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourie transform infrared (FTIR), X-ray diffractometer (XRD), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The adsorption performance of PAS-GO was investigated in removing Pb(II) ions from water. Compared to 3-aminopropyltriethoxysilane functionalized GO (AS-GO) which was prepared by the direct reaction between 3-aminopropyltriethoxysilane and GO, PAS-GO exhibited much higher adsorptivity toward Pb(II) with the maximum adsorption capacity of 312.5 mg/g at 303 K and furthermore the maximum adsorption capacity increased with increasing temperature. The adsorption could be conducted in a wide pH range of 4.0–7.0. Importantly, PAS-GO had a priority tendency to adsorb Pb, Cu and Fe from a mixed solution of metal ions, especially from a practical industrial effluent

  8. Leptin Inhibits the Proliferation of Vascular Smooth Muscle Cells Induced by Angiotensin II through Nitric Oxide-Dependent Mechanisms

    Directory of Open Access Journals (Sweden)

    Amaia Rodríguez

    2010-01-01

    Full Text Available Objective. This study was designed to investigate whether leptin modifies angiotensin (Ang II-induced proliferation of aortic vascular smooth muscle cells (VSMCs from 10-week-old male Wistar and spontaneously hypertensive rats (SHR, and the possible role of nitric oxide (NO. Methods. NO and NO synthase (NOS activity were assessed by the Griess and 3H-arginine/citrulline conversion assays, respectively. Inducible NOS (iNOS and NADPH oxidase subutnit Nox2 expression was determined by Western-blot. The proliferative responses to Ang II were evaluated through enzymatic methods. Results. Leptin inhibited the Ang II-induced proliferative response of VSMCs from control rats. This inhibitory effect of leptin was abolished by NOS inhibitor, NMMA, and iNOS selective inhibitor, L-NIL, and was not observed in leptin receptor-deficient fa/fa rats. SHR showed increased serum leptin concentrations and lipid peroxidation. Despite a similar leptin-induced iNOS up-regulation, VSMCs from SHR showed an impaired NOS activity and NO production induced by leptin, and an increased basal Nox2 expression. The inhibitory effect of leptin on Ang II-induced VSMC proliferation was attenuated. Conclusion. Leptin blocks the proliferative response to Ang II through NO-dependent mechanisms. The attenuation of this inhibitory effect of leptin in spontaneous hypertension appears to be due to a reduced NO bioavailability in VSMCs.

  9. 3d-4f {Co(II)3Ln(OR)4} Cubanes as Bio-Inspired Water Oxidation Catalysts.

    Science.gov (United States)

    Evangelisti, Fabio; Moré, René; Hodel, Florian; Luber, Sandra; Patzke, Greta Ricarda

    2015-09-02

    Although the {CaMn4O5} oxygen evolving complex (OEC) of photosystem II is a major paradigm for water oxidation catalyst (WOC) development, the comprehensive translation of its key features into active molecular WOCs remains challenging. The [Co(II)3Ln(hmp)4(OAc)5H2O] ({Co(II)3Ln(OR)4}; Ln = Ho-Yb, hmp = 2-(hydroxymethyl)pyridine) cubane WOC series is introduced as a new springboard to address crucial design parameters, ranging from nuclearity and redox-inactive promoters to operational stability and ligand exchange properties. The {Co(II)3Ln(OR)4} cubanes promote bioinspired WOC design by newly combining Ln(3+) centers as redox-inactive Ca(2+) analogues with flexible aqua-/acetate ligands into active and stable WOCs (max. TON/TOF values of 211/9 s(-1)). Furthermore, they open up the important family of 3d-4f complexes for photocatalytic applications. The stability of the {Co(II)3Ln(OR)4} WOCs under photocatalytic conditions is demonstrated with a comprehensive analytical strategy including trace metal analyses and solution-based X-ray absorption spectroscopy (XAS) investigations. The productive influence of the Ln(3+) centers is linked to favorable ligand mobility, and the experimental trends are substantiated with Born-Oppenheimer molecular dynamics studies.

  10. Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

    Directory of Open Access Journals (Sweden)

    Hao Ma

    2018-01-01

    Full Text Available Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

  11. Alumina/silica aerogel with zinc chloride as an alkylation catalyst

    Directory of Open Access Journals (Sweden)

    DEJAN U. SKALA

    2001-10-01

    Full Text Available The alumina/silica with zinc chloride aerogel alkylation catalyst was obtained using a one step sol-gel synthesis, and subsequent drying with supercritical carbon dioxide. The aerogel catalyst activity was found to be higher compared to the corresponding xerogel catalyst, as a result of the higher aerogel surface area, total pore volume and favourable pore size distribution. Mixed Al–O–Si bonds were present in both gel catalyst types. Activation by thermal treatment in air was needed prior to catalytic alkylation, due to the presence of residual organic groups on the aerogel surface. The optimal activation temperature was found to be in the range 185–225°C, while higher temperatures resulted in the removal of zinc chloride from the surface of the aerogel catalyst with a consequential decrease in the catalytic activity. On varying the zinc chloride content, the catalytic activity of the aerogel catalyst exhibited a maximum. High zinc chloride contents decreased the catalytic activity of the aerogel catalyst as the result of the pores of the catalyst being plugged with this compound, and the separation of the alumina/silica support into Al-rich and Si-rich phases. The surface area, total pore volume, pore size distribution and zinc chloride content had a similar influence on the activity of the aerogel catalyst as was the case of xerogel catalyst and supported zinc chloride catalysts.

  12. Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction.

    Science.gov (United States)

    Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yi, Yong; Yang, Fan

    2018-01-30

    Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

  13. Optimization of an aerogel cerenkov detector having a mirror light collection system

    International Nuclear Information System (INIS)

    Johansson, K.E.; Aakesson, T.; Norrby, J.

    1979-01-01

    Cerenkov detectors with silica aerogel of refractive indec 1.03 as the radiator have been tested in a particle beam at the CERN Proton Synchrotron. With a detector surface of 22 x 50 cm 2 and 9 cm thickness of aerogel, the number of photoelectrons was found to be 6.5 for β = 1 particles. (author)

  14. Preparation and characterization of silica aerogels from diatomite via ambient pressure drying

    Science.gov (United States)

    Wang, Baomin; Ma, Hainan; Song, Kai

    2014-07-01

    The silica aerogels were successfully fabricated under ambient pressure from diatomite. The influence of different dilution ratios of diatomite filtrate on physical properties of aerogels were studied. The microstructure, surface functional groups, thermal stability, morphology and mechanical properties of silica aerogels based on diatomite were investigated by BET adsorption, FT-IR, DTA-TG, FESEM, TEM, and nanoindentation methods. The results indicate that the filtrate diluted with distilled water in a proportion of 1: 2 could give silica aerogels in the largest size with highest transparency. The obtained aerogels with density of 0.122-0.203 g/m3 and specific surface area of 655.5-790.7 m2/g are crack free amorphous solids and exhibited a sponge-like structure. Moreover, the peak pore size resided at 9 nm. The initial aerogels were hydrophobic, when being heat-treated around 400°C, the aerogels were transformed into hydrophilic ones. The obtained aerogel has good mechanical properties.

  15. Low-temperature specific-heat and thermal-conductivity of silica aerogels

    DEFF Research Database (Denmark)

    Bernasconi, A.; Sleator, T.; Posselt, D.

    1992-01-01

    Specific heat, C(p), and thermal conductivity, lambda, have been measured on a series of base-catalyzed silica aerogels at temperatures between 0.05 and 20 K. Results for both C(p)(T) and lambda(T) confirm that the different length-scale regions observed in the aerogel structure are reflected...

  16. Synthesis of Fe3O4 cluster microspheres/graphene aerogels composite as anode for high-performance lithium ion battery

    Science.gov (United States)

    Zhou, Shuai; Zhou, Yu; Jiang, Wei; Guo, Huajun; Wang, Zhixing; Li, Xinhai

    2018-05-01

    Iron oxides are considered as attractive electrode materials because of their capability of lithium storage, but their poor conductivity and large volume expansion lead to unsatisfactory cycling stability. We designed and synthesized a novel Fe3O4 cluster microspheres/Graphene aerogels composite (Fe3O4/GAs), where Fe3O4 nanoparticles were assembled into cluster microspheres and then embedded in 3D graphene aerogels framework. In the spheres, the sufficient free space between Fe3O4 nanoparticles could accommodate the volume change during cycling process. Graphene aerogel works as flexible and conductive matrix, which can not only significantly increase the mechanical stress, but also further improve the storage properties. The Fe3O4/GAs composite as an anode material exhibits high reversible capability and excellent cyclic capacity for lithium ion batteries (LIBs). A reversible capability of 650 mAh g-1 after 500 cycles at a current density of 1 A g-1 can be maintained. The superior storage capabilities of the composites make them potential anode materials for LIBs.

  17. Enhanced electrochemical capacitance and oil-absorbability of N-doped graphene aerogel by using amino-functionalized silica as template and doping agent

    Science.gov (United States)

    Du, Yongxu; Liu, Libin; Xiang, Yu; Zhang, Qiang

    2018-03-01

    The development of novel energy storage devices with high power density and energy density is highly desired. However, as a promising material, the strong π-π interaction of graphene inhibits its applications. Herein, we provide a new approach that amino-functionalized silica are used as both templates to prevent the restacking of the graphene sheets and doping agents simultaneously. The microstructures, porous properties and chemical composition of the resulted N-doped reduced graphene oxide (RGO) aerogels, characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, indicate that the amount of SiO2-NH2 has profound effects on the surface area and carbon activity of the graphene sheets. Benefiting from the large specific surface area of 481.8 m2 g-1, low series resistances and high nitrogen doping content (4.4 atom%), the as-fabricated 3D hierarchical porous N-doped RGO aerogel electrode exhibits outstanding electrochemical performance in aqueous and organic electrolyte, such as ultrahigh specific capacitances of 350 F g-1 at a current density of 1 A g-1 and excellent reversibility with a cycling efficiency of 88% after 10000 cycles. In addition, the N-doped RGO aerogels possess high oil-absorbability with long recyclability.

  18. Characterization of pH dependent Mn(II) oxidation strategies and formation of a bixbyite-like phase by Mesorhizobium australicum T-G1

    Science.gov (United States)

    Bohu, Tsing; Santelli, Cara M; Akob, Denise M.; Neu, Thomas R; Ciobota, Valerian; Rösch, Petra; Popp, Jürgen; Nietzsche, Sándor; Küsel, Kirsten

    2015-01-01

    Despite the ubiquity of Mn oxides in natural environments, there are only a few observations of biological Mn(II) oxidation at pH MOB) isolates limits our understanding of how pH influences biological Mn(II) oxidation in extreme environments. Here, we report that a novel MOB isolate, Mesorhizobium australicum strain T-G1, isolated from an acidic and metalliferous uranium mining area, can oxidize Mn(II) at both acidic and neutral pH using different enzymatic pathways. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy revealed that T-G1 initiated bixbyite-like Mn oxide formation at pH 5.5 which coincided with multi-copper oxidase expression from early exponential phase to late stationary phase. In contrast, reactive oxygen species (ROS), particularly superoxide, appeared to be more important for T-G1 mediated Mn(II) oxidation at neutral pH. ROS was produced in parallel with the occurrence of Mn(II) oxidation at pH 7.2 from early stationary phase. Solid phase Mn oxides did not precipitate, which is consistent with the presence of a high amount of H2O2 and lower activity of catalase in the liquid culture at pH 7.2. Our results show that M. australicum T-G1, an acid tolerant MOB, can initiate Mn(II) oxidation by varying its oxidation mechanisms depending on the pH and may play an important role in low pH manganese biogeochemical cycling.

  19. Role of shear stress in nitric oxide-dependent modulation of renal angiotensin II vasoconstriction.

    Science.gov (United States)

    Endlich, K; Muller, C; Barthelmebs, M; Helwig, J J

    1999-08-01

    1. Renal vasoconstriction in response to angiotensin II (ANGII) is known to be modulated by nitric oxide (NO). Since shear stress stimulates the release of a variety of vasoactive compounds from endothelial cells, we studied the impact of shear stress on the haemodynamic effect of ANGII in isolated perfused kidneys of rats under control conditions and during NO synthase inhibition with L-NAME (100 microM). 2. Kidneys were perfused in the presence of cyclo-oxygenase inhibitor (10 microM indomethacin) with Tyrode's solution of relative viscosity zeta=1 (low viscosity perfusate, LVP) or, in order to augment shear stress, with Tyrode's solution containing 7% Ficoll 70 of relative viscosity zeta=2 (high viscosity perfusate, HVP). 3. Vascular conductance was 3.5+/-0.4 fold larger in HVP as compared with LVP kidneys, associated with an augmentation of overall wall shear stress by 37+/-5%. During NO inhibition, vascular conductance was only 2.5+/-0.2 fold elevated in HVP vs LVP kidneys, demonstrating shear stress-induced vasodilatation by NO and non-NO/non-prostanoid compound(s). 4. ANGII (10 - 100 pM) constricted the vasculature in LVP kidneys, but was without effect in HVP kidneys. During NO inhibition, in contrast, ANGII vasoconstriction was potentiated in HVP as compared with LVP kidneys. 5. The potentiation of ANGII vasoconstriction during NO inhibition has been shown to be mediated by endothelium-derived P450 metabolites and to be sensitive to AT2 receptor blockade in our earlier studies. Accordingly, in HVP kidneys, increasing concentrations of the AT2 receptor antagonist PD123319 (5 and 500 nM) gradually abolished the potentiation of ANGII vasoconstriction during NO inhibition, but did not affect vasoconstriction in response to ANGII in LVP kidneys. 6. Our results demonstrate, that augmentation of shear stress by increasing perfusate viscosity induces vasodilatation in the rat kidney, which is partially mediated by NO. Elevated levels of shear stress attenuate

  20. Insights into Nitrate-Reducing Fe(II) Oxidation Mechanisms through Analysis of Cell-Mineral Associations, Cell Encrustation, and Mineralogy in the Chemolithoautotrophic Enrichment Culture KS.

    Science.gov (United States)

    Nordhoff, M; Tominski, C; Halama, M; Byrne, J M; Obst, M; Kleindienst, S; Behrens, S; Kappler, A

    2017-07-01

    Most described nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB) are mixotrophic and depend on organic cosubstrates for growth. Encrustation of cells in Fe(III) minerals has been observed for mixotrophic NRFeOB but not for autotrophic phototrophic and microaerophilic Fe(II) oxidizers. So far, little is known about cell-mineral associations in the few existing autotrophic NRFeOB. Here, we investigate whether the designated autotrophic Fe(II)-oxidizing strain (closely related to Gallionella and Sideroxydans ) or the heterotrophic nitrate reducers that are present in the autotrophic nitrate-reducing Fe(II)-oxidizing enrichment culture KS form mineral crusts during Fe(II) oxidation under autotrophic and mixotrophic conditions. In the mixed culture, we found no significant encrustation of any of the cells both during autotrophic oxidation of 8 to 10 mM Fe(II) coupled to nitrate reduction and during cultivation under mixotrophic conditions with 8 to 10 mM Fe(II), 5 mM acetate, and 4 mM nitrate, where higher numbers of heterotrophic nitrate reducers were present. Two pure cultures of heterotrophic nitrate reducers ( Nocardioides and Rhodanobacter ) isolated from culture KS were analyzed under mixotrophic growth conditions. We found green rust formation, no cell encrustation, and only a few mineral particles on some cell surfaces with 5 mM Fe(II) and some encrustation with 10 mM Fe(II). Our findings suggest that enzymatic, autotrophic Fe(II) oxidation coupled to nitrate reduction forms poorly crystalline Fe(III) oxyhydroxides and proceeds without cellular encrustation while indirect Fe(II) oxidation via heterotrophic nitrate-reduction-derived nitrite can lead to green rust as an intermediate mineral and significant cell encrustation. The extent of encrustation caused by indirect Fe(II) oxidation by reactive nitrogen species depends on Fe(II) concentrations and is probably negligible under environmental conditions in most habitats. IMPORTANCE Most described nitrate

  1. Insights into Nitrate-Reducing Fe(II) Oxidation Mechanisms through Analysis of Cell-Mineral Associations, Cell Encrustation, and Mineralogy in the Chemolithoautotrophic Enrichment Culture KS

    Science.gov (United States)

    Nordhoff, M.; Tominski, C.; Halama, M.; Byrne, J. M.; Obst, M.; Behrens, S.

    2017-01-01

    ABSTRACT Most described nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB) are mixotrophic and depend on organic cosubstrates for growth. Encrustation of cells in Fe(III) minerals has been observed for mixotrophic NRFeOB but not for autotrophic phototrophic and microaerophilic Fe(II) oxidizers. So far, little is known about cell-mineral associations in the few existing autotrophic NRFeOB. Here, we investigate whether the designated autotrophic Fe(II)-oxidizing strain (closely related to Gallionella and Sideroxydans) or the heterotrophic nitrate reducers that are present in the autotrophic nitrate-reducing Fe(II)-oxidizing enrichment culture KS form mineral crusts during Fe(II) oxidation under autotrophic and mixotrophic conditions. In the mixed culture, we found no significant encrustation of any of the cells both during autotrophic oxidation of 8 to 10 mM Fe(II) coupled to nitrate reduction and during cultivation under mixotrophic conditions with 8 to 10 mM Fe(II), 5 mM acetate, and 4 mM nitrate, where higher numbers of heterotrophic nitrate reducers were present. Two pure cultures of heterotrophic nitrate reducers (Nocardioides and Rhodanobacter) isolated from culture KS were analyzed under mixotrophic growth conditions. We found green rust formation, no cell encrustation, and only a few mineral particles on some cell surfaces with 5 mM Fe(II) and some encrustation with 10 mM Fe(II). Our findings suggest that enzymatic, autotrophic Fe(II) oxidation coupled to nitrate reduction forms poorly crystalline Fe(III) oxyhydroxides and proceeds without cellular encrustation while indirect Fe(II) oxidation via heterotrophic nitrate-reduction-derived nitrite can lead to green rust as an intermediate mineral and significant cell encrustation. The extent of encrustation caused by indirect Fe(II) oxidation by reactive nitrogen species depends on Fe(II) concentrations and is probably negligible under environmental conditions in most habitats. IMPORTANCE Most described nitrate

  2. Highly Porous, Rigid-Rod Polyamide Aerogels with Superior Mechanical Properties and Unusually High Thermal Conductivity.

    Science.gov (United States)

    Williams, Jarrod C; Nguyen, Baochau N; McCorkle, Linda; Scheiman, Daniel; Griffin, Justin S; Steiner, Stephen A; Meador, Mary Ann B

    2017-01-18

    We report here the fabrication of polyamide aerogels composed of poly-p-phenylene-terephthalamide, the same backbone chemistry as DuPont's Kevlar. The all-para-substituted polymers gel without the use of cross-linker and maintain their shape during processing-an improvement over the meta-substituted cross-linked polyamide aerogels reported previously. Solutions containing calcium chloride (CaCl 2 ) and para-phenylenediamine (pPDA) in N-methylpyrrolidinone (NMP) at low temperature are reacted with terephthaloyl chloride (TPC). Polymerization proceeds over the course of 5 min resulting in gelation. Removal of the reaction solvent via solvent exchange followed by extraction with supercritical carbon dioxide provides aerogels with densities ranging from 0.1 to 0.3 g/cm 3 , depending on the concentration of calcium chloride, the formulated number of repeat units, n, and the concentration of polymer in the reaction mixture. These variables were assessed in a statistical experimental study to understand their effects on the properties of the aerogels. Aerogels made using at least 30 wt % CaCl 2 had the best strength when compared to aerogels of similar density. Furthermore, aerogels made using 30 wt % CaCl 2 exhibited the lowest shrinkage when aged at elevated temperatures. Notably, whereas most aerogel materials are highly insulating (thermal conductivities of 10-30 mW/m K), the polyamide aerogels produced here exhibit remarkably high thermal conductivities (50-80 mW/(m K)) at the same densities as other inorganic and polymer aerogels. These high thermal conductivities are attributed to efficient phonon transport by the rigid-rod polymer backbone. In conjunction with their low cost, ease of fabrication with respect to other polymer aerogels, low densities, and high mass-normalized strength and stiffness properties, these aerogels are uniquely valuable for applications such as lightweighting in consumer electronics, automobiles, and aerospace where weight reduction is

  3. Remediation of Soil and Ground Water Contaminated with PAH using Heat and Fe(II)-EDTA Catalyzed Persulfate Oxidation

    International Nuclear Information System (INIS)

    Nadim, Farhad; Huang, Kun-Chang; Dahmani, Amine M.

    2006-01-01

    The feasibility of degrading 16 USEPA priority polycyclic aromatic (PAH) hydrocarbons (PAHs) with heat and Fe(II)-EDTA catalyzed persulfate oxidation was investigated in the laboratory. The experiments were conducted to determine the effects of temperature (i.e. 20 deg. C, 30 deg. C and 40 deg. C) and iron-chelate levels (i.e., 250 mg/L-, 375 mg/L- and 500 mg/L-Fe(II)) on the degradation of dissolved PAHs in aqueous systems, using a series of amber glass jars as the reactors that were placed on a shaker inside an incubator for temperature control. Each experiment was run in duplicate and had two controls (i.e., no persulfate in systems). Samples were collected after a reaction period of 144 hrs and measured for PAHs, pH and sodium persulfate levels. The extent of degradation of PAHs was determined by comparing the data for samples with the controls.The experimental results showed that persulfate oxidation under each of the tested conditions effectively degraded the 16 target PAHs. All of the targeted PAHs were degraded to below the instrument detection limits (∼4 μ/L) from a range of initial concentration (i.e., 5 μ/L for benzo(a)pyrene to 57 μ/L for Phenanthrene) within 144 hrs with 5 g/L of sodium persulfate at 20 deg. C, 30 deg. C and 40 deg. C. The data indicated that the persulfate oxidation was effective in degrading the PAHs and that external heat and iron catalysts might not be needed for the degradation of PAHs.The Fe(II)-EDTA catalyzed persulfate also effectively degraded PAHs in the study. In addition, the data on the variation of persulfate concentrations during the experiments indicated that Fe(II)-EDTA accelerated the consumption of persulfate ions.The obtained degradation data cannot be used to evaluate the influence of temperature and Fe(II) levels on the PAH degradation because the PAHs under each of the tested conditions were degraded to below the instrument detection limit within the first sampling point. However, these experiments have

  4. Seasonal variability of oxidative stress markers in city bus drivers. Part II. Oxidative damage to lipids and proteins.

    Science.gov (United States)

    Rossner, Pavel; Svecova, Vlasta; Milcova, Alena; Lnenickova, Zdena; Solansky, Ivo; Sram, Radim J

    2008-07-03

    The aim of the present study was to investigate the seasonal variability of markers of oxidative damage to lipids (15-F2t-isoprostane, 15-F2t-IsoP) and proteins (protein carbonyl levels) in 50 bus drivers and 50 controls from Prague, Czech Republic, and to identify factors affecting oxidative stress markers. The samples were collected in three seasons with different levels of air pollution. The exposure to environmental pollutants (carcinogenic polycyclic aromatic hydrocarbons, c-PAHs, particulate matter, PM2.5 and PM10, and volatile organic compounds, VOC) was monitored by personal and/or stationary monitors. For the analysis of both markers, ELISA techniques were used. The median levels of individual markers in bus drivers versus controls were as follows: 15-F2t-IsoP (nmol/mmol creatinine): winter 2005, 0.81 versus 0.68 (pbus drivers in winter seasons, but not in summer. Lipid peroxidation was positively correlated with c-PAHs and PM exposure; protein oxidation correlated negatively and was highest in summer suggesting another factor(s) affecting protein carbonyl levels.

  5. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    Science.gov (United States)

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. X-ray radiographic technique for measuring density uniformity of silica aerogel

    International Nuclear Information System (INIS)

    Tabata, Makoto; Hatakeyama, Yoshikiyo; Adachi, Ichiro; Morita, Takeshi; Nishikawa, Keiko

    2013-01-01

    This paper proposes a new X-ray radiographic technique for measuring density uniformity of silica aerogels used as radiator in proximity-focusing ring-imaging Cherenkov detectors. To obtain high performance in a large-area detector, a key characteristic of radiator is the density (i.e. refractive index) uniformity of an individual aerogel monolith. At a refractive index of n=1.05, our requirement for the refractive index uniformity in the transverse plane direction of an aerogel tile is |δ(n−1)/(n−1)|<4% in a focusing dual layer radiator (with different refractive indices) scheme. We applied the radiographic technique to evaluate the density uniformity of our original aerogels from a trial production and that of Panasonic products (SP-50) as a reference, and to confirm they have sufficient density uniformity within ±1% along the transverse plane direction. The measurement results show that the proposed technique can quantitatively estimate the density uniformity of aerogels.

  7. Supercritical methanol drying as a convenient route to phenolic-furfural aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Albert, Donald F.; Bruno, Joseph W. [Department of Chemistry, Wesleyan University, 06459 Middletown, CT (United States); Andrews, Greg R.; Mendenhall, Robert S. [American Aerogel Corporation, 1000 Corporate Row, 06416 Cromwell, CT (United States)

    2001-12-01

    Organic aerogels are prepared by the acid catalyzed cross-linking of phenolic-furfural (PF) precursors in methanol solution, and the solvent is subsequently removed at high temperature as the supercritical fluid. The resulting aerogel is a brown opaque solid and has been prepared as 30 ml cylindrical monoliths exhibiting little or no shrinkage during formation. These solids, which are routinely available with a density as low as ca. 125mg/cm{sup 3}, have been characterized by chemical methods (infrared spectroscopy and CP-MAS 13C NMR spectrometry) and physical techniques (Brunauer-Emmet-Teller surface area, transmission and scanning electron microscopy). In addition, thermal conductivities have been determined, and show that the PF aerogels are excellent thermal insulators. These studies establish that the materials described herein exhibit chemical and physical properties very similar to those seen for organic aerogels prepared with low temperature processing techniques. The current method constitutes a convenient and rapid route to organic aerogels.

  8. Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

    Directory of Open Access Journals (Sweden)

    Carlos Macias

    2016-01-01

    Full Text Available We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores. The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

  9. Silica aerogel Cherenkov counter for the KEK B-factory experiment

    CERN Document Server

    Sumiyoshi, T; Enomoto, R; Iijima, T; Suda, R; Leonidopoulos, C; Marlow, D R; Prebys, E; Kawabata, R; Kawai, H; Ooba, T; Nanao, M; Suzuki, K; Ogawa, S; Murakami, A; Khan, M H R

    1999-01-01

    Low-refractive-index silica aerogel is a convenient radiator for threshold-type Cherenkov counters, which are used for particle identification in high-energy physics experiments. For the BELLE detector at the KEK B-Factory we have produced about 2 m sup 3 of hydrophobic silica aerogels of n=1.01-1.03 using a new production method. The particle identification capability of the aerogel Cherenkov counters was tested and 3 sigma pion/proton separation has been achieved at 3.5 GeV/c. Radiation hardness of the aerogels was confirmed up to 9.8 Mrad. The Aerogel Cherenkov counter system (ACC) was successfully installed in the BELLE just before this conference.

  10. The Relation between the Rheological Properties of Gels and the Mechanical Properties of Their Corresponding Aerogels

    Directory of Open Access Journals (Sweden)

    Mingze Sun

    2018-04-01

    Full Text Available A series of low density, highly porous clay/poly(vinyl alcohol composite aerogels, incorporating ammonium alginate, were fabricated via a convenient and eco-friendly freeze drying method. It is significant to understand rheological properties of precursor gels because they directly affect the form of aerogels and their processing behaviors. The introduction of ammonium alginate impacted the rheological properties of colloidal gels and improved the mechanical performance of the subject aerogels. The specific compositions and processing conditions applied to those colloidal gel systems brought about different aerogel morphologies, which in turn translated into the observed mechanical properties. The bridge between gel rheologies and aerogel structures are established in the present work.

  11. Amalgamation based optical and colorimetric sensing of mercury(II) ions with silver graphene oxide nanocomposite materials

    International Nuclear Information System (INIS)

    Kamali, Khosro Zangeneh; Pandikumar, Alagarsamy; Jayabal, Subramaniam; Huang, Nay Ming; Ramaraj, Ramasamy; Lim, Hong Ngee; Ong, Boon Hoong; Bien, Chia Sheng Daniel; Kee, Yeh Yee

    2016-01-01

    The article describes a facile method for the preparation of a conjugate composed of silver nanoparticles and graphene oxide (Ag GO) via chemical reduction of silver precursors in the presence of graphene oxide (GO) while sonicating the solution. The Ag GO was characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, and energy-dispersive X-ray spectroscopy. The nanocomposite undergoes a color change from yellow to colorless in presence of Hg(II), and this effect is based on the disappearance of the localized surface plasmon resonance absorption of the AgNPs due to the formation of silver-mercury amalgam. The presence of GO, on the other hand, prevents the agglomeration of the AgNPs and enhances the stability of the nanocomposite material in solution. Hence, the probe represents a viable optical probe for the determination of mercury(II) ions in that it can be used to visually detect Hg(II) concentrations as low as 100 μM. The instrumental LOD is 338 nM. (author)

  12. Bismuth oxide based ceramics with improved electrical and mechanical properties: Part II. Structural and mechanical properties

    NARCIS (Netherlands)

    Kruidhof, H.; Seshan, Kulathuiyer; van de Velde, G.M.H.; de Vries, K.J.; Burggraaf, A.J.

    1988-01-01

    Coprecipitation as a method of preparation for bismuth oxides based ceramics yields relatively strong and machineable materials in comparison with the solid state reaction. Compositions within the system (1−x)Bi2O3|xEr2O3 containing up to twenty five mole percent of erbium oxide show a slow

  13. Formation and Transformation of Iron Oxide-Kaolinite Associations in the Presence of Iron(II)

    NARCIS (Netherlands)

    Wei, S.Y.; Liu, F.; Feng, X.H.; Tan, W.F.; Koopal, L.K.

    2011-01-01

    Iron oxide-kaolinite associations are important components of tropical and subtropical soils and have significant influence on the physical and chemical properties of soils. In this study, the formation and transformation of Fe oxide-kaolinite associations as a function of pH, temperature, and time

  14. Self-assembled three-dimensional hierarchical graphene/polypyrrole nanotube hybrid aerogel and its application for supercapacitors.

    Science.gov (United States)

    Ye, Shibing; Feng, Jiachun

    2014-06-25

    A three-dimensional hierarchical graphene/polypyrrole aerogel (GPA) has been fabricated using graphene oxide (GO) and already synthesized one-dimensional hollow polypyrrole nanotubes (PNTs) as the feedstock. The amphiphilic GO is helpful in effectively promoting the dispersion of well-defined PNTs to result in a stable, homogeneous GO/PNT complex solution, while the PNTs not only provide a large accessible surface area for fast transport of hydrate ions but also act as spacers to prevent the restacking of graphene sheets. By a simple one-step reduction self-assembly process, hierarchically structured, low-density, highly compressible GPAs are easily obtained, which favorably combine the advantages of graphene and PNTs. The supercapacitor electrodes based on such materials exhibit excellent electrochemical performance, including a high specific capacitance up to 253 F g(-1), good rate performance, and outstanding cycle stability. Moreover, this method may be feasible to prepare other graphene-based hybrid aerogels with structure-controllable nanostructures in large scale, thereby holding enormous potential in many application fields.

  15. Synthesis, Processing, and Characterization of Inorganic-Organic Hybrid Cross-Linked Silica, Organic Polyimide, and Inorganic Aluminosilicate Aerogels

    Science.gov (United States)

    Nguyen, Baochau N.; Guo, Haiquan N.; McCorkle, Linda S.

    2014-01-01

    As aerospace applications become ever more demanding, novel insulation materials with lower thermal conductivity, lighter weight and higher use temperature are required to fit the aerospace application needs. Having nanopores and high porosity, aerogels are superior thermal insulators, among other things. The use of silica aerogels in general is quite restricted due to their inherent fragility, hygroscopic nature, and poor mechanical properties, especially in extereme aerospace environments. Our research goal is to develop aerogels with better mechanical and environmental stability for a variety of aeronautic and space applications including space suit insulation for planetary surface missions, insulation for inflatable structures for habitats, inflatable aerodynamic decelerators for entry, descent and landing (EDL) operations, and cryotank insulation for advance space propulsion systems. Different type of aerogels including organic-inorganic polymer reinforced (hybrid) silica-based aerogels, polyimide aerogels and inorganic aluminosilicate aerogels have been developed and examined.

  16. Expanding rare-earth oxidation state chemistry to molecular complexes of holmium(II) and erbium(II).

    Science.gov (United States)

    MacDonald, Matthew R; Bates, Jefferson E; Fieser, Megan E; Ziller, Joseph W; Furche, Filipp; Evans, William J

    2012-05-23

    The first molecular complexes of holmium and erbium in the +2 oxidation state have been generated by reducing Cp'(3)Ln [Cp' = C(5)H(4)SiMe(3); Ln = Ho (1), Er (2)] with KC(8) in the presence of 18-crown-6 in Et(2)O at -35 °C under argon. Purification and crystallization below -35 °C gave isomorphous [(18-crown-6)K][Cp'(3)Ln] [Ln = Ho (3), Er (4)]. The three Cp' ring centroids define a trigonal-planar geometry around each metal ion that is not perturbed by the location of the potassium crown cation near one ring with K-C(Cp') distances of 3.053(8)-3.078(2) Å. The metrical parameters of the three rings are indistinguishable within the error limits. In contrast to Ln(2+) complexes of Eu, Yb, Sm, Tm, Dy, and Nd, 3 and 4 have average Ln-(Cp' ring centroid) distances only 0.029 and 0.021 Å longer than those of the Ln(3+) analogues 1 and 2, a result similar to that previously reported for the 4d(1) Y(2+) complex [(18-crown-6)K][Cp'(3)Y] (5) and the 5d(1) La(2+) complex [K(18-crown-6)(Et(2)O)][Cp″(3)La] [Cp″ = 1,3-(Me(3)Si)(2)C(5)H(3)]. Surprisingly, the UV-vis spectra of 3 and 4 are also very similar to that of 5 with two broad absorptions in the visible region, suggesting that 3-5 have similar electron configurations. Density functional theory calculations on the Ho(2+) and Er(2+) species yielded HOMOs that are largely 5d(z(2)) in character and supportive of 4f(10)5d(1) and 4f(11)5d(1) ground-state configurations, respectively.

  17. Effect of ozone on ruthenium species in alkaline medium. Pt. II. Oxidation of pentahydroxo nitrosyl ruthenate(II) ion RuNO(OH)52-

    International Nuclear Information System (INIS)

    Floquet, S.; Eysseric, C.

    2006-01-01

    Oxidation of the nitrosyl ruthenium complex RuNO(OH) 5 2- has been carried out in sodium hydroxide solutions in contact with a gas flow containing ozone. The RuNO(OH) 5 2- complex is converted successively into ruthenate and perruthenate ions. An empirical kinetic rate law for the first step has been determined and was shown to depend on concentrations of (i) the ruthenium complex, (ii) the hydroxide ions and (iii) ozone concentration in the gas flow. The second step of the reaction, corresponding to the perruthenate ion formation, shows a complex mechanism and four competing reactions have been proposed to represent it. The influences on the second step kinetics of several parameters such as ozone or hydroxide concentrations or the conditions of the gas-liquid exchange area are also qualitatively discussed. (orig.)

  18. Effect of ozone on ruthenium species in alkaline medium. Pt. II. Oxidation of pentahydroxo nitrosyl ruthenate(II) ion RuNO(OH){sub 5}{sup 2-}

    Energy Technology Data Exchange (ETDEWEB)

    Floquet, S. [Commissariat a l' Energie Atomique (CEA/Valrho), Bagnols-sur-Ceze (France); Inst. Lavoisier, IREM UMR 8637, Univ. de Versailles Saint-Quentin, Versailles (France); Eysseric, C. [Commissariat a l' Energie Atomique (CEA/Valrho), Bagnols-sur-Ceze (France)

    2006-07-01

    Oxidation of the nitrosyl ruthenium complex RuNO(OH){sub 5}{sup 2-} has been carried out in sodium hydroxide solutions in contact with a gas flow containing ozone. The RuNO(OH){sub 5}{sup 2-} complex is converted successively into ruthenate and perruthenate ions. An empirical kinetic rate law for the first step has been determined and was shown to depend on concentrations of (i) the ruthenium complex, (ii) the hydroxide ions and (iii) ozone concentration in the gas flow. The second step of the reaction, corresponding to the perruthenate ion formation, shows a complex mechanism and four competing reactions have been proposed to represent it. The influences on the second step kinetics of several parameters such as ozone or hydroxide concentrations or the conditions of the gas-liquid exchange area are also qualitatively discussed. (orig.)

  19. In vitro antibacterial activity of oxide and non-oxide bioceramics for arthroplastic devices: II. Fourier transform infrared spectroscopy.

    Science.gov (United States)

    Boschetto, Francesco; Toyama, Nami; Horiguchi, Satoshi; Bock, Ryan M; McEntire, Bryan J; Adachi, Tetsuya; Marin, Elia; Zhu, Wenliang; Mazda, Osam; Bal, B Sonny; Pezzotti, Giuseppe

    2018-04-30

    The metabolic response of Gram-positive Staphylococcus epidermidis (S. epidermidis) bacteria to bioceramic substrates was probed by means of Fourier transform infrared spectroscopy (FTIR). Oxide zirconia-toughened alumina (ZTA) and non-oxide silicon nitride (Si3N4) substrates were tested. Bacteria exposed to silica glass substrates were used as a control. S. epidermidis, a major cause of periprosthetic infections, was screened to obtain a precise time-lapse knowledge of its molecular composition and to mechanistically understand its interaction with different substrates. At the molecular level, the structure of proteins, lipids, nucleic acid, and aromatic amino acids evolved with time in response to different substrates. In combination with statistical validation and local pH measurements, a chemical lysis mechanism was spectroscopically observed in situ on the Si3N4 substrates. Utilization of FTIR in this study avoided fluorescence noise which occurred while probing the ZTA samples with Raman spectroscopy in a companion paper. The substrate-driven dynamics of polysaccharide and peptide variations in the bacterial cell wall, peculiar to Si3N4 bioceramics, are elucidated.

  20. Iron oxide impregnated Morus alba L. fruit peel for biosorption of Co(II): biosorption properties and mechanism.

    Science.gov (United States)

    Koduru, Janardhan Reddy; Chang, Yoon-Young; Yang, Jae-Kyu; Kim, Im-Soon

    2013-01-01

    Biosorption is an ecofriendly wastewater treatment technique with high efficiency and low operating cost involving simple process for the removal of heavy metal ions from aqueous solution. In the present investigation, Morus alba L. fruit peel powder (MAFP) and iron oxide impregnated Morus alba L. fruit peel powder (IO-MAFP) were prepared and used for treating Co(II) contaminated aqueous solutions. Further the materials were characterized by using FTIR and SEM-EDX analysis. From FT-IR analysis it was found that hydroxyl, methoxy, and carbonyl groups are responsible for Co(II) biosorption. The kinetic data obtained for both biosorbents was well fitted with pseudo-second-order kinetic model. The equilibrium data was in tune with the Langmuir and Freundlich isotherm models. The thermodynamic studies were also carried and it was observed that sorption process was endothermic at 298-328 K. These studies demonstrated that both biosorbents were promising, efficient, economic, and biodegradable sorbents.

  1. Making oxidation potentials predictable: Coordination of additives applied to the electronic fine tuning of an iron(II) complex

    KAUST Repository

    Haslinger, Stefan

    2014-11-03

    This work examines the impact of axially coordinating additives on the electronic structure of a bioinspired octahedral low-spin iron(II) N-heterocyclic carbene (Fe-NHC) complex. Bearing two labile trans-acetonitrile ligands, the Fe-NHC complex, which is also an excellent oxidation catalyst, is prone to axial ligand exchange. Phosphine- and pyridine-based additives are used for substitution of the acetonitrile ligands. On the basis of the resulting defined complexes, predictability of the oxidation potentials is demonstrated, based on a correlation between cyclic voltammetry experiments and density functional theory calculated molecular orbital energies. Fundamental insights into changes of the electronic properties upon axial ligand exchange and the impact on related attributes will finally lead to target-oriented manipulation of the electronic properties and consequently to the effective tuning of the reactivity of bioinspired systems.

  2. Making oxidation potentials predictable: Coordination of additives applied to the electronic fine tuning of an iron(II) complex

    KAUST Repository

    Haslinger, Stefan; Kü ck, Jens W.; Hahn, Eva M.; Cokoja, Mirza; Pö thig, Alexander; Basset, Jean-Marie; Kü hn, Fritz

    2014-01-01

    This work examines the impact of axially coordinating additives on the electronic structure of a bioinspired octahedral low-spin iron(II) N-heterocyclic carbene (Fe-NHC) complex. Bearing two labile trans-acetonitrile ligands, the Fe-NHC complex, which is also an excellent oxidation catalyst, is prone to axial ligand exchange. Phosphine- and pyridine-based additives are used for substitution of the acetonitrile ligands. On the basis of the resulting defined complexes, predictability of the oxidation potentials is demonstrated, based on a correlation between cyclic voltammetry experiments and density functional theory calculated molecular orbital energies. Fundamental insights into changes of the electronic properties upon axial ligand exchange and the impact on related attributes will finally lead to target-oriented manipulation of the electronic properties and consequently to the effective tuning of the reactivity of bioinspired systems.

  3. Kinetics of the oxidative hydroxylation of tetraphosphorus in the presence of copper(II chloride modified by humic (fulvo- acid

    Directory of Open Access Journals (Sweden)

    Zhaksyntay Kairbekov

    2012-12-01

    Full Text Available It was established that in mild conditions (50-70 oC, РО2= 1 atm white phosphorus effectively is oxidized by oxygen in water-toluene solutions of copper(II chloride modified by humic (fulvo- acid to give mainly phosphoric acid. Humic (fulvo- acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, intermediate and final products, optimum conditions of new catalytic reaction of P4 oxidation by oxygen in water medium were defined by kinetics, volumometry, redox-potentiometry, 31Р{1Н} NMR spectroscopy and  titration. 

  4. Kinetics of the oxidative hydroxylation of sodium hypophosphite in the presence of copper (II chloride modified by humic (fulvo- acid

    Directory of Open Access Journals (Sweden)

    Zhaksyntay Kairbekov

    2012-12-01

    Full Text Available It was established that in soft conditions (50-70oC, PO2 = 1 atm sodium hypophosphite effectively is oxidized by oxygen in water solutions of copper(II chloride  to give mainly a phosphorous acid. Humic (fulvo- acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, the intermediate and final products, optimal conditions of new catalytic reaction of NaH2PO2 oxidation by oxygen in water solution were defined by kinetics, volumometry, redox-potentiometry and a titration.

  5. Cladding oxidation during air ingress. Part II: Synthesis of modelling results

    International Nuclear Information System (INIS)

    Beuzet, E.; Haurais, F.; Bals, C.; Coindreau, O.; Fernandez-Moguel, L.; Vasiliev, A.; Park, S.

    2016-01-01

    Highlights: • A state-of-the-art for air oxidation modelling in the frame of severe accident is done. • Air oxidation models from main severe accident codes are detailed. • Simulations from main severe accident codes are compared against experimental results. • Perspectives in terms of need for further model development and experiments are given. - Abstract: Air ingress is a potential risk in some low probable situations of severe accidents in a nuclear power plant. Air is a highly oxidizing atmosphere that can lead to an enhanced Zr-based cladding oxidation and core degradation affecting the release of fission products. This is particularly true speaking about ruthenium release, due to its high radiotoxicity and its ability to form highly volatile oxides in a significant manner in presence of air. The oxygen affinity is decreasing from the Zircaloy cladding, fuel and ruthenium inclusions. It is consequently of great need to understand the phenomena governing cladding oxidation by air as a prerequisite for the source term issues in such scenarios. In the past years, many works have been done on cladding oxidation by air under severe accident conditions. This paper with in addition the paper “Cladding oxidation during air ingress – Part I: Synthesis of experimental results” of this journal issue aim at assessing the state of the art on this phenomenon. In this paper, the modelling of air ingress phenomena in the main severe accident codes (ASTEC, ATHLET-CD, MAAP, MELCOR, RELAP/SCDAPSIM, SOCRAT) is described in details, as well as the validation against the integral experiments QUENCH-10, QUENCH-16 and PARAMETER-SF4. A full review of cladding oxidation by air is thus established.

  6. Nitric oxide, prostaglandins and angiotensin II in the regulation of renal medullary blood flow during volume expansion.

    Science.gov (United States)

    Moreno, Carol; Llinás, María T; Rodriguez, Francisca; Moreno, Juan M; Salazar, F Javier

    2016-03-01

    Regulation of medullary blood flow (MBF) is essential in maintaining renal function and blood pressure. However, it is unknown whether outer MBF (OMBF) and papillary blood flow (PBF) are regulated independently when extracellular volume (ECV) is enhanced. The aim of this study was to determine whether OMBF and PBF are differently regulated and whether there is an interaction between nitric oxide (NO), prostaglandins (PGs) and angiotensin II (Ang II) in regulating OMBF and PBF when ECV is enhanced. To achieve these goals, OMBF and PBF were measured by laser-Doppler in volume-expanded rats treated with a cyclooxygenase inhibitor (meclofenamate, 3 mg/kg) and/or a NO synthesis inhibitor (L-nitro-arginine methyl ester (L-NAME), 3 μg/kg/min) and/or Ang II (10 ng/kg/min). OMBF was unchanged by NO or PGs synthesis inhibition but decreased by 36 % (P blood flows to the outer medulla and renal papilla are differently regulated and showing that there is a complex interaction between NO, PGs and Ang II in regulating OMBF and PBF when ECV is enhanced.

  7. Spectrophotometric investigation on the kinetics of oxidation of adrenaline by dioxygen of μ-dioxytetrakis(histidinato)-dicobalt(II) complex

    Science.gov (United States)

    Rafiquee, M. Z. A.; Siddiqui, Masoom R.; Ali, Mohd. Sajid; Al-Lohedan, Hamad A.

    The cobalt(II)histidine complex binds molecular oxygen reversibly to form an oxygen adduct complex, μ-dioxytetrakis-(histidinato)dicobalt(II). The molecular oxygen can be released from the oxygenated complex by heating it or by passing N2, He or Ar gas through its solution. μ-Dioxytetrakis-(histidinato)dicobalt(II) complex oxidizes adrenaline into leucoadrenochrome at 25 °C while at higher temperature (>40 °C) adrenochrome with λmax at 490 nm is formed. The rate of formation of leucoadrenochrome was found to be independent of [bis(histidinato)cobalt(II)]. The rate of reaction for the formation of leucoadrenochrome and adrenochrome increased with the increase in [adrenaline] at its lower concentration but become independent at higher concentration. Similarly, the rate of formation of both leucoadrenochrome and adrenochrome was linearly dependent upon [NaOH]. The values of activation parameters i.e. ΔEa, ΔH‡ and ΔS‡ for the formation of leucoadrenochrome are reported.

  8. Kinetics of the oxidative hydroxylation of tetraphosphorus in the presence of copper(II) chloride modified by humic (fulvo-) acid

    OpenAIRE

    Zhaksyntay Kairbekov; Dina Akbayeva; Zh. Eshova

    2012-01-01

    It was established that in mild conditions (50-70 oC, РО2= 1 atm) white phosphorus effectively is oxidized by oxygen in water-toluene solutions of copper(II) chloride modified by humic (fulvo-) acid to give mainly phosphoric acid. Humic (fulvo-) acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, intermediate and final ...

  9. Investigation of self-powered gamma flux detectors with Lead(II) oxide serving as both emitter and insulator

    International Nuclear Information System (INIS)

    Shi, H.; Yue, S.; Jonkmans, G.; Sur, B.; Hilborn, J.

    2010-01-01

    The use of Lead(II) oxide as the electron-emitting component and the insulating component of self-powered flux detectors is a concept that had not been previously explored. Detectors constructed from various combinations of electrodes (stainless steel, Al, Pb, and W) and insulating materials (Al 2 O 3 and PbO) were irradiated in a 427 Gy/h gamma field. Although high gamma sensitivities were achieved, PbO did not prove to be a strong emitter of gamma-induced electrons. Nevertheless, PbO did serve as a better insulator than one that is currently in use, namely alumina. (author)

  10. Comparative Genomic Analysis of Neutrophilic Iron(II Oxidizer Genomes for Candidate Genes in Extracellular Electron Transfer

    Directory of Open Access Journals (Sweden)

    Shaomei He

    2017-08-01

    Full Text Available Extracellular electron transfer (EET is recognized as a key biochemical process in circumneutral pH Fe(II-oxidizing bacteria (FeOB. In this study, we searched for candidate EET genes in 73 neutrophilic FeOB genomes, among which 43 genomes are complete or close-to-complete and the rest have estimated genome completeness ranging from 5 to 91%. These neutrophilic FeOB span members of the microaerophilic, anaerobic phototrophic, and anaerobic nitrate-reducing FeOB groups. We found that many microaerophilic and several anaerobic FeOB possess homologs of Cyc2, an outer membrane cytochrome c originally identified in Acidithiobacillus ferrooxidans. The “porin-cytochrome c complex” (PCC gene clusters homologous to MtoAB/PioAB are present in eight FeOB, accounting for 19% of complete and close-to-complete genomes examined, whereas PCC genes homologous to OmbB-OmaB-OmcB in Geobacter sulfurreducens are absent. Further, we discovered gene clusters that may potentially encode two novel PCC types. First, a cluster (tentatively named “PCC3” encodes a porin, an extracellular and a periplasmic cytochrome c with remarkably large numbers of heme-binding motifs. Second, a cluster (tentatively named “PCC4” encodes a porin and three periplasmic multiheme cytochromes c. A conserved inner membrane protein (IMP encoded in PCC3 and PCC4 gene clusters might be responsible for translocating electrons across the inner membrane. Other bacteria possessing PCC3 and PCC4 are mostly Proteobacteria isolated from environments with a potential niche for Fe(II oxidation. In addition to cytochrome c, multicopper oxidase (MCO genes potentially involved in Fe(II oxidation were also identified. Notably, candidate EET genes were not found in some FeOB, especially the anaerobic ones, probably suggesting EET genes or Fe(II oxidation mechanisms are different from the searched models. Overall, based on current EET models, the search extends our understanding of bacterial EET and

  11. Cyclopentadienyl molybdenum(II/VI) N-heterocyclic carbene complexes: Synthesis, structure, and reactivity under oxidative conditions

    KAUST Repository

    Li, Shenyu

    2010-04-26

    A series of N-heterocyclic carbene (NHC) complexes CpMo(CO) 2(NHC)X (NHC = IMe = 1,3-dimethylimidazol-2-ylidene, X = Br, 1; NHC = 1,3-dipropylimidazol-2-ylidene, X = Br, 2; NHC = IMes = 1,3-bis(2,4,6- trimethylphenyl)imidazol-2-ylidene, X = Br, 3; NHC = IBz = 1,3-dibenzylimidazol- 2-ylidene, X = Br, 4a, and X = Cl, 4b; NHC = 1-methyl-3-propylimidazol-2- ylidene, X = Br, 5) and [CpMo(CO)2(IMes)(CH3CN)][BF 4] (6) have been synthesized and fully characterized. The stability of metal-NHC ligand bonds in these compounds under oxidative conditions has been investigated. The thermally stable Mo(VI) dioxo NHC complex [CpMoO 2(IMes)][BF4] (9) has been isolated by the oxidation of the ionic complex 6 by TBHP (tert-butyl hydrogen peroxide). Complex 6 can be applied as a very active (TOFs up to 3400 h-1) and selective olefin epoxidation catalyst. While under oxidative conditions (in the presence of TBHP), compounds 1-5 decompose into imidazolium bromide and imidazolium polyoxomolybdate. The formation of polyoxomolybdate as oxidation products had not been observed in a similar epoxidation catalyzed by Mo(II) and Mo(VI) complexes. DFT studies suggest that the presence of Br- destabilizes the CpMo(VI) oxo NHC carbene species, consistent with the experimental observations. © 2010 American Chemical Society.

  12. Transformation of Unsaturated Fatty Acids/Esters to Corresponding Keto Fatty Acids/Esters by Aerobic Oxidation with Pd(II)/Lewis Acid Catalyst.

    Science.gov (United States)

    Senan, Ahmed M; Zhang, Sicheng; Zeng, Miao; Chen, Zhuqi; Yin, Guochuan

    2017-08-16

    Utilization of renewable biomass to partly replace the fossil resources in industrial applications has attracted attention due to the limited fossil feedstock with the increased environmental concerns. This work introduced a modified Wacker-type oxidation for transformation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, in which Cu 2+ cation was replaced with common nonredox metal ions, that is, a novel Pd(II)/Lewis acid (LA) catalyst. It was found that adding nonredox metal ions can effectively promote Pd(II)-catalyzed oxidation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, even much better than Cu 2+ , and the promotional effect is highly dependent on the Lewis acidity of added nonredox metal ions. The improved catalytic efficiency is attributed to the formation of heterobimetallic Pd(II)/LA species, and the oxidation mechanism of this Pd(II)/LA catalyst is also briefly discussed.

  13. Determination of HCl and VOC Emission from Thermal Degradation of PVC in the Absence and Presence of Copper, Copper(II Oxide and Copper(II Chloride

    Directory of Open Access Journals (Sweden)

    Ahamad J. Jafari

    2009-01-01

    Full Text Available Polyvinyl chloride (PVC has played a key role in the development of the plastic industry over the past 40 years. Thermal degradation of PVC leads to formation of many toxic pollutants such as HCl, aromatic and volatile organic carbon vapors. Thermal degradation of PVC and PVC in the present of copper, cupric oxide and copper(II chloride were investigated in this study using a laboratory scale electrical furnace. HCl and Cl- ion were analyzed by a Dionex ion chromatograph and VOCs compounds were analyzed using GC or GC-MS. The results showed that HCl plus Cl- ion and benzene formed about 99% and 80% respectively in the first step of thermal degradation under air atmosphere. The presence of cupric oxide increases the percentage of short chain hydrocarbons more than 184% and decreases the amount of the major aromatic hydrocarbon and HCl plus Cl- ion to 90% and 65% respectively. The total aromatic hydrocarbon emitted less than when atmosphere was air and difference was statistically significant (Pvalue<0.000

  14. The group theory of oxidation II: cosets of non-split groups

    International Nuclear Information System (INIS)

    Keurentjes, Arjan

    2003-01-01

    The oxidation program given in the first article of this series (see preceding article in this issue) is extended to cover oxidation of 3d sigma model theories on a coset G/H, with G non-compact (but not necessarily split), and H the maximal compact subgroup. We recover the matter content, the equations of motion and Bianchi identities from group lattice and Cartan involution. Satake diagrams provide an elegant tool for the computations, the maximal oxidation dimension, and group disintegration chains can be directly read off. We give a complete list of theories that can be recovered from oxidation of a 3-dimensional coset sigma model on G/H, where G is a simple non-compact group

  15. One electron oxidation of Ni(II)-iminodiacetate by carbonate radical

    International Nuclear Information System (INIS)

    Mandal, P.C.; Bardhan, D.K.; Bhattacharyya, S.N.

    1995-01-01

    Reactions of carbonate radical (CO 3 - ), generated by photolysis or by radiolysis of a carbonate solution with nickel(II)-iminodiacetate (Ni(II)IDA) were studied at pH 10.5 and ionic strength (I)=0.2 mol x dm -3 . The stable product arising from the ligand degradation in the complex is mainly glyoxalic acid. Time-resolved spectroscopy and transient kinetics were studied using flash photolysis. From the kinetic data it was suggested that the carbonate radical initially reacts with Ni(III)IDA with a rate constant (2.4.±0.4) x 10 6 dm 3 x mol -1 x s -1 to form a Ni(II)IDA species which, however, undergoes a first-order transformation (k=2.7 x 10 2 x s -1 ) to give a radical intermediate of the type Ni(II)RNHCHCO - 2 ) which rapidly forms an adduct containing a Ni-C bond. This adduct decays very slowly to give rise to glyoxalic acid. From a consideration of equilibrium between Ni(II)IDA and Ni(III)IDA, the one electron reduction potential for the Ni(III)IDA/Ni(II)IDA couple was determined to be 1.467 V. (author) 30 refs.; 5 figs

  16. Part II: Effects of gamma irradiation on lipid and cholesterol oxidation in mechanically deboned turkey meat

    International Nuclear Information System (INIS)

    Farkas, J.; Andrassy, E.; Meszaros, L.; Beczner, J.; Polyak-Feher, K.; Gaal, O.; Lebovics, V.K.; Lugasi, A.

    2009-01-01

    The pasteurizing effect of a 2 kGy radiation dose on non-frozen mechanically deboned turkey meat was achieved without increase in cholesterol oxidation products or increases in thiobarbituric acid reactive substance values during 15 d of chilled storage following the treatments, while untreated samples were spoiled. The addition of antioxidants, such as thyme oil or α-tocopherol plus ascorbic acid, significantly inhibited the oxidative changes of cholesterol and lipids during 3 kGy treatment. (author)

  17. Three-Dimensionally Hierarchical Graphene Based Aerogel Encapsulated Sulfur as Cathode for Lithium/Sulfur Batteries

    Directory of Open Access Journals (Sweden)

    Haipeng Li

    2018-01-01

    Full Text Available A simple and effective method was developed to obtain the electrode for lithium/sulfur (Li/S batteries with high specific capacity and cycling durability via adopting an interconnected sulfur/activated carbon/graphene (reduced graphene oxide aerogel (S/AC/GA cathode architecture. The AC/GA composite with a well-defined interconnected conductive network was prepared by a reduction-induced self-assembly process, which allows for obtaining compact and porous structures. During this process, reduced graphene oxide (RGO was formed, and due to the presence of oxygen-containing functional groups on its surface, it not only improves the electronic conductivity of the cathode but also effectively inhibits the polysulfides dissolution and shuttle. The introduced activated carbon allowed for lateral and vertical connection between individual graphene sheets, completing the formation of a stable three-dimensionally (3D interconnected graphene framework. Moreover, a high specific surface area and 3D interconnected porous structure efficiently hosts a higher amount of active sulfur material, about 65 wt %. The designed S/AC/GA composite electrodes deliver an initial capacity of 1159 mAh g−1 at 0.1 C and can retain a capacity of 765 mAh g−1 after 100 cycles in potential range from 1 V to 3 V.

  18. Three-Dimensionally Hierarchical Graphene Based Aerogel Encapsulated Sulfur as Cathode for Lithium/Sulfur Batteries

    Science.gov (United States)

    Li, Haipeng; Sun, Liancheng; Wang, Zhuo; Zhang, Yongguang; Tan, Taizhe; Wang, Gongkai

    2018-01-01

    A simple and effective method was developed to obtain the electrode for lithium/sulfur (Li/S) batteries with high specific capacity and cycling durability via adopting an interconnected sulfur/activated carbon/graphene (reduced graphene oxide) aerogel (S/AC/GA) cathode architecture. The AC/GA composite with a well-defined interconnected conductive network was prepared by a reduction-induced self-assembly process, which allows for obtaining compact and porous structures. During this process, reduced graphene oxide (RGO) was formed, and due to the presence of oxygen-containing functional groups on its surface, it not only improves the electronic conductivity of the cathode but also effectively inhibits the polysulfides dissolution and shuttle. The introduced activated carbon allowed for lateral and vertical connection between individual graphene sheets, completing the formation of a stable three-dimensionally (3D) interconnected graphene framework. Moreover, a high specific surface area and 3D interconnected porous structure efficiently hosts a higher amount of active sulfur material, about 65 wt %. The designed S/AC/GA composite electrodes deliver an initial capacity of 1159 mAh g−1 at 0.1 C and can retain a capacity of 765 mAh g−1 after 100 cycles in potential range from 1 V to 3 V. PMID:29373525

  19. Nitrous Oxide and Serious Long-term Morbidity and Mortality in the Evaluation of Nitrous Oxide in the Gas Mixture for Anaesthesia (ENIGMA)-II Trial.

    Science.gov (United States)

    Leslie, Kate; Myles, Paul S; Kasza, Jessica; Forbes, Andrew; Peyton, Philip J; Chan, Matthew T V; Paech, Michael J; Sessler, Daniel I; Beattie, W Scott; Devereaux, P J; Wallace, Sophie

    2015-12-01

    The Evaluation of Nitrous Oxide in the Gas Mixture for Anaesthesia (ENIGMA)-II trial randomly assigned 7,112 noncardiac surgery patients at risk of perioperative cardiovascular events to 70% N2O or 70% N2 groups. The aim of this follow-up study was to determine the effect of nitrous oxide on a composite primary outcome of death and major cardiovascular events at 1 yr after surgery. One-year follow-up was conducted via a medical record review and telephone interview. Disability was defined as a Katz index of independence in activities of daily living score less than 8. Adjusted odds ratios and hazard ratios were calculated as appropriate for primary and secondary outcomes. Among 5,844 patients evaluated at 1 yr, 435 (7.4%) had died, 206 (3.5%) had disability, 514 (8.8%) had a fatal or nonfatal myocardial infarction, and 111 (1.9%) had a fatal or nonfatal stroke during the 1-yr follow-up period. Exposure to nitrous oxide did not increase the risk of the primary outcome (odds ratio, 1.08; 95% CI, 0.94 to 1.25; P = 0.27), disability or death (odds ratio, 1.07; 95% CI, 0.90 to 1.27; P = 0.44), death (hazard ratio, 1.17; 95% CI, 0.97 to 1.43; P = 0.10), myocardial infarction (odds ratio, 0.97; 95% CI, 0.81 to 1.17; P = 0.78), or stroke (odds ratio, 1.08; 95% CI, 0.74 to 1.58; P = 0.70). These results support the long-term safety of nitrous oxide administration in noncardiac surgical patients with known or suspected cardiovascular disease.

  20. Ambient pressure dried tetrapropoxysilane-based silica aerogels with high specific surface area

    Science.gov (United States)

    Parale, Vinayak G.; Han, Wooje; Jung, Hae-Noo-Ree; Lee, Kyu-Yeon; Park, Hyung-Ho

    2018-01-01

    In the present paper, we report the synthesis of tetrapropoxysilane (TPOS)-based silica aerogels with high surface area and large pore volume. The silica aerogels were prepared by a two-step sol-gel process followed by surface modification via a simple ambient pressure drying approach. In order to minimize drying shrinkage and obtain hydrophobic aerogels, the surface of the alcogels was modified using trichloromethylsilane as a silylating agent. The effect of the sol-gel compositional parameters on the polymerization of aerogels prepared by TPOS, one of the precursors belonging to the Si(OR)4 family, was reported for the first time. The oxalic acid and NH4OH concentrations were adjusted to achieve good-quality aerogels with high surface area, low density, and high transparency. Controlling the hydrolysis and condensation reactions of the TPOS precursor turned out to be the most important factor to determine the pore characteristics of the aerogel. Highly transparent aerogels with high specific surface area (938 m2/g) and low density (0.047 g/cm3) could be obtained using an optimized TPOS/MeOH molar ratio with appropriate concentrations of oxalic acid and NH4OH.

  1. Marinobacter subterrani, a genetically tractable neutrophilic Fe(II-oxidizing strain isolated from the Soudan Iron Mine

    Directory of Open Access Journals (Sweden)

    Benjamin Michael Bonis

    2015-07-01

    Full Text Available We report the isolation, characterization, and development of a robust genetic system for a halophilic, Fe(II-oxidizing bacterium isolated from a vertical borehole originating 714 m below the surface located in the Soudan Iron Mine in northern Minnesota, USA. Sequence analysis of the 16S rRNA gene places the isolate in the genus Marinobacter of the Gammaproteobacteria. The genome of the isolate was sequenced using a combination of short- and long-read technologies resulting in 2 contigs representing a 4.4 Mbp genome. Using genomic information, we used a suicide vector for targeted deletion of specific flagellin genes, resulting in a motility-deficient mutant. The motility mutant was successfully complemented by expression of the deleted genes in trans. Random mutagenesis using a transposon was also achieved. Capable of heterotrophic growth, this isolate represents a microaerophilic Fe(II-oxidizing species for which a system for both directed and random mutagenesis has been established. Analysis of 16S rDNA suggests Marinobacter represents a major taxon in the mine, and genetic interrogation of this genus may offer insight into the structure of deep subsurface communities as well as an additional tool for analyzing nutrient and element cycling in the subsurface ecosystem.

  2. Mtr Extracellular Electron Transfer Pathways in Fe(III)-reducing or Fe(II)-oxidizing Bacteria: A Genomic Perspective

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Liang; Rosso, Kevin M.; Zachara, John M.; Fredrickson, Jim K.

    2012-12-01

    Originally discovered in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), the Mtr (i.e., metal-reducing) pathway exists in all characterized strains of metal-reducing Shewanella. The protein components identified to date for the Mtr pathway of MR-1 include four multi-heme c-type cytochromes (c-Cyts), CymA, MtrA, MtrC and OmcA, and a porin-like, outer membrane protein MtrB. They are strategically positioned along the width of the MR-1 cell envelope to mediate electron transfer from the quinone/quinol pool in the inner-membrane to the Fe(III)-containing minerals external to the bacterial cells. A survey of microbial genomes revealed homologues of the Mtr pathway in other dissimilatory Fe(III)-reducing bacteria, including Aeromonas hydrophila, Ferrimonas balearica and Rhodoferax ferrireducens, and in the Fe(II)-oxidizing bacteria Dechloromonas aromatica RCB, Gallionella capsiferriformans ES-2 and Sideroxydans lithotrophicus ES-1. The widespread distribution of Mtr pathways in Fe(III)-reducing or Fe(II)-oxidizing bacteria emphasizes the importance of this type of extracellular electron transfer pathway in microbial redox transformation of Fe. Their distribution in these two different functional groups of bacteria also emphasizes the bi-directional nature of electron transfer reactions carried out by the Mtr pathways. The characteristics of the Mtr pathways may be shared by other pathways used by microorganisms for exchanging electrons with their extracellular environments.

  3. Destruction of hazardous and mixed wastes using mediated electrochemical oxidation in a Ag(II)HNO3 bench scale system

    International Nuclear Information System (INIS)

    Balazs, B.; Chiba, Z.; Hsu, P.; Lewis, P.; Murguia, L.; Adamson, M.

    1997-01-01

    Mediated Electrochemical Oxidation (MEO) is a promising technology for the destruction of organic containing wastes and the remediation of mixed wastes containing transuranic components. The combination of a powerful oxidant and an acid solution allows the conversion of nearly all organics, whether present in hazardous or in mixed waste, to carbon dioxide. Insoluble transuranics are dissolved in this process and may be recovered by separation and precipitation.The MEO technique offers several advantages which are inherent in the system. First, the oxidation/dissolution processes are accomplished at near ambient pressures and temperatures (30-70 degrees C). Second, all waste stream components and oxidation products (with the exception of evolved gases) are contained in an aqueous environment. This electrolyte acts as an accumulator for inorganics which were present in the original waste stream, and the large volume of electrolyte provides a thermal buffer for the energy released during oxidation of the organics. Third, the generation of secondary waste is minimal, as the process needs no additional reagents. Finally, the entire process can be shut down by simply turning off the power, affording a level of control unavailable in some other techniques.Numerous groups, both in the United States and Europe, have made substantial progress in the last decade towards understanding the mechanistic pathways, kinetics, and engineering aspects of the process. At Lawrence Livermore National Laboratory, substantial contributions have been made to this knowledge base in these areas and others. Conceptual design and engineering development have been completed for a pilot plant-scale MEO system, and numerous data have been gathered on the efficacy of the process for a wide variety of anticipated waste components. This presentation will review the data collected at LLNL for a bench scale system based primarily on the use of a Ag(II) mediator in a nitric acid electrolyte; results

  4. Impact Verification of Aerogel Insulation Paint on Historic Brick Facades

    Science.gov (United States)

    Ganobjak, Michal; Kralova, Eva

    2017-10-01

    Increasing the sustainability of existing buildings is being motivated by reduction of their energy demands. It is the above all the building envelope and its refurbishment by substitution or addition of new materials that makes the opportunity for reduction of energy consumption. A special type of refurbishment is conservation of historical buildings. Preservation of historic buildings permits also application of innovative methods and materials in addition to the original materials if their effects are known and the gained experience ensures their beneficial effect. On the market, there are new materials with addition of silica aerogel in various forms of products. They are also potentially useful in conservation of monuments. However, the effects of aerogel application in these cases are not known. For refurbishment is commercially available additional transparent insulation paint - Nansulate Clear Coat which is containing aerogel and can be used for structured surfaces such as bricks. A series of experiments examined the thermo-physical manifestation of an ultra-thin insulation coating of Nansulate Clear Coat containing silica aerogel on a brick facade. The experiments of active and passive thermography have observed effects of application on the small-scale samples of the brick façade of a protected historical building. Through a series of experiments were measured thermal insulation effect and influence on the aesthetic characteristics such as change in colour and gloss. The treated samples were compared to a reference. Results have shown no thermal-insulating manifestation of the recommended three layers of insulation paint. The three layers recommended by the manufacturer did not significantly affect the appearance of the brick facade. Color and gloss were not significantly changed. Experiments showed the absence of thermal insulation effect of Nansulate transparent triple coating. The thermal insulation effect could likely be reached by more layers of

  5. Synthesising highly reactive tin oxide using Tin(II2- ethylhexanoate polynucleation as precursor

    Directory of Open Access Journals (Sweden)

    Alejandra Montenegro Hernández

    2009-01-01

    Full Text Available Tin oxide is a widely used compound in technological applications, particularity as a catalyst, gas sensor and in making varistors, transparent conductors, electrocatalytic electrodes and photovoltaic cells. An ethylhexanoate tin salt, a carboxylic acid and poly-esterification were used for synthesising highly reactive tin oxide in the present study. Synthesis was controlled by Fourier transform infrared (FTIR spectroscopy and recording changes in viscosity. The tin oxide characteristics so obtained were determined using FTIR spectroscopy, X-ray diffraction (XRD and scanning electron microscopy (SEM. The SnO2 dust synthesised and heat-treated at 550°C yielded high density aggregates, having greater than 50 μm particle size. This result demonstrates the high reactivity of the ceramic powders synthesised here.

  6. The Role of Vasodilator Receptors of Renin-angiotensin System on Nitric Oxide Formation and Kidney Circulation after Angiotensin II Infusion in Renal Ischemia/Reperfusion Rats.

    Science.gov (United States)

    Maleki, Maryam; Hasanshahi, Jalal; Moslemi, Fatemeh

    2018-01-01

    Nitric oxide (NO) as a vasodilator factor has renoprotective effect against renal ischemia. The balance between angiotensin II (Ang II) and NO can affect kidney homeostasis. The aim of this study was to determine NO alteration in response to renin-Ang system vasodilator receptors antagonists (PD123319; Ang II type 2 receptor antagonist and A779; Mas receptor antagonist) in renal ischemia/reperfusion injury (IRI) in rats. Sixty-three Wistar male and female rats were used. Animals from each gender were divided into four groups received saline, Ang II, PD123319 + Ang II, and A779 + Ang II after renal IRI. Renal IRI induced with an adjustable hook. Blood pressure and renal blood flow (RBF) measured continuously. The nitrite levels were measured in serum, kidney, and urine samples. In female rats, the serum and kidney nitrite levels increased significantly by Ang II ( P < 0.05) and decreased significantly ( P < 0.05) when PD123319 was accompanied with Ang II. Such observation was not seen in male. Ang II decreased RBF significantly in all groups ( P < 0.05), while PD + Ang II group showed significant decrease in RBF in comparison with the other groups in female rats ( P < 0.05). Males show more sensibility to Ang II infusion; in fact, it is suggested that there is gender dimorphism in the Ang II and NO production associated with vasodilator receptors.

  7. Three-dimensional multichannel aerogel of carbon quantum dots for high-performance supercapacitors

    Science.gov (United States)

    Lv, Lingxiao; Fan, Yueqiong; Chen, Qing; Zhao, Yang; Hu, Yue; Zhang, Zhipan; Chen, Nan; Qu, Liangti

    2014-06-01

    A three-dimensional (3D) carbon quantum dot (CQD) aerogel has been prepared by in situ assembling CQDs in the sol-gel polymerization of resorcinol (R) and formaldehyde (F) and subsequently pyrolyzing the formed CQD gel. Compared to the supercapacitor based on the CQD-free aerogel, the supercapacitor fabricated with the CQD aerogel showed 20-fold higher specific capacitance (294.7 F g-1 at the current density of 0.5 A g-1) and an excellent stability over 1000 consecutive charge-discharge cycles.

  8. Dynamic properties of silica aerogels as deduced from specific-heat and thermal-conductivity measurements

    DEFF Research Database (Denmark)

    Bernasconi, A.; Sleator, T.; Posselt, D.

    1992-01-01

    The specific heat C(p) and the thermal conductivity lambda of a series of base-catalyzed silica aerogels have been measured at temperatures between 0.05 and 20 K. The results confirm that the different length-scale regions observed in the aerogel structure are reflected in the dynamic behavior of...... SiO2 are most likely not due to fractal behavior....... the possibility of two spectral dimensions characterizing the fracton modes. Our data imply important differences between the physical mechanisms dominating the low-temperature behavior of aerogels and dense glasses, respectively. From our analysis we also conclude that the low-temperature properties of amorphous...

  9. Robust Vacuum-/Air-Dried Graphene Aerogels and Fast Recoverable Shape-Memory Hybrid Foams.

    Science.gov (United States)

    Li, Chenwei; Qiu, Ling; Zhang, Baoqing; Li, Dan; Liu, Chen-Yang

    2016-02-17

    New graphene aerogels can be fabricated by vacuum/air drying, and because of the mechanical robustness of the graphene aerogels, shape-memory polymer/graphene hybrid foams can be fabricated by a simple infiltration-air-drying-crosslinking method. Due to the superelasticity, high strength, and good electrical conductivity of the as-prepared graphene aerogels, the shape-memory hybrid foams exhibit excellent thermotropical and electrical shape-memory properties, outperforming previously reported shape-memory polymer foams. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. A study of the oxidation of nickel-titanium intermetallics. II. Phase composition of the scale

    Energy Technology Data Exchange (ETDEWEB)

    Chuprina, V G [Institut Problem Materialovedeniia, Kiev (Ukrainian SSR)

    1989-06-01

    The phase composition of the scale formed on NiTi during oxidation in air in the temperature range 600-1000 C was investigated by X-ray diffraction and layer-by-layer metallographic analyses. The scale was found to contain NiO, NiO.TiO2, TiO2, Ti2O3, Ti3O5, Ni, and Ni(Ti) solid solution; an Ni3Ti sublayer was present at the scale-alloy boundary. Oxygen diffusion in the scale toward the sublayer and counterdiffusion of Ni(+2) were found to be the principal processes responsible for NiTi oxidation. 8 refs.

  11. Surfactant controlled low-temperature thermal decomposition route to zinc oxide nanorods from zinc(II) acetylacetonate monohydrate

    Energy Technology Data Exchange (ETDEWEB)

    Purkayastha, Debraj Dhar; Sarma, Bedabrat; Bhattacharjee, Chira R., E-mail: crbhattacharjee@rediffmail.com

    2014-10-15

    Zinc oxide (ZnO) nanorods were synthesized via a low-temperature thermal decomposition of zinc(II) acetylacetonate monohydrate, [Zn(C{sub 5}H{sub 7}O{sub 2}){sub 2}].H{sub 2}O. A relatively inexpensive surfactant, octadecylamine (C{sub 18}H{sub 37}NH{sub 2}) served both as a reaction solvent and a capping agent during the synthesis of ZnO nanorods. The synthesized nanorods were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, UV–visible, and photoluminescence (PL) studies. The XRD spectrum furnished evidence for the hexagonal wurtzite structure of ZnO. TEM images revealed the material to be rod shaped having diameter 30 nm and length 200 nm. The HRTEM image showed that the lattice fringes between the two adjacent planes are 0.244 nm apart, which corresponds to the interplanar separation of the (1 0 1) plane of hexagonal ZnO. The electron diffraction (ED) pattern confirmed the single crystalline nature of the nanorods. The PL spectrum showed two UV emissions at 356 nm (∼3.48 eV) and 382 nm (∼3.25 eV). ZnO nanorods also showed very weak blue bands at 445, 453 and 470 nm. - Highlights: Low temperature thermal decomposition of zinc(II) acetylacetonate monohydrate gave zinc oxide nanorods. Powder XRD showed hexagonal wurtzite structure of ZnO having average diameter about 24 nm. TEM images revealed the material to be of rod shape having diameter 30 nm and length 200 nm. ZnO showed band gap luminescence at 356 nm, excitonic emission at 382 nm and defect related blue bands. The synthesis is simple and can act as a paradigm for obtaining various metal oxide nanomaterials.

  12. Nickel Oxide (NiO nanoparticles prepared by solid-state thermal decomposition of Nickel (II schiff base precursor

    Directory of Open Access Journals (Sweden)

    Aliakbar Dehno Khalaji

    2015-06-01

    Full Text Available In this paper, plate-like NiO nanoparticles were prepared by one-pot solid-state thermal decomposition of nickel (II Schiff base complex as new precursor. First, the nickel (II Schiff base precursor was prepared by solid-state grinding using nickel (II nitrate hexahydrate, Ni(NO32∙6H2O, and the Schiff base ligand N,N′-bis-(salicylidene benzene-1,4-diamine for 30 min without using any solvent, catalyst, template or surfactant. It was characterized by Fourier Transform Infrared spectroscopy (FT-IR and elemental analysis (CHN. The resultant solid was subsequently annealed in the electrical furnace at 450 °C for 3 h in air atmosphere. Nanoparticles of NiO were produced and characterized by X-ray powder diffraction (XRD at 2θ degree 0-140°, FT-IR spectroscopy, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The XRD and FT-IR results showed that the product is pure and has good crystallinity with cubic structure because no characteristic peaks of impurity were observed, while the SEM and TEM results showed that the obtained product is tiny, aggregated with plate-like shape, narrow size distribution with an average size between 10-40 nm. Results show that the solid state thermal decomposition method is simple, environmentally friendly, safe and suitable for preparation of NiO nanoparticles. This method can also be used to synthesize nanoparticles of other metal oxides.

  13. Reduced Graphene Oxide-Immobilized Tris(bipyridine)ruthenium(II) Complex for Efficient Visible-Light-Driven Reductive Dehalogenation Reaction.

    Science.gov (United States)

    Li, Xiaoyan; Hao, Zhongkai; Zhang, Fang; Li, Hexing

    2016-05-18

    A sodium benzenesulfonate (PhSO3Na)-functionalized reduced graphene oxide was synthesized via a two-step aryl diazonium coupling and subsequent NaCl ion-exchange procedure, which was used as a support to immobilize tris(bipyridine)ruthenium(II) complex (Ru(bpy)3Cl2) by coordination reaction. This elaborated Ru(bpy)3-rGO catalyst exhibited excellent catalytic efficiency in visible-light-driven reductive dehalogenation reactions under mild conditions, even for ary chloride. Meanwhile, it showed the comparable reactivity with the corresponding homogeneous Ru(bpy)3Cl2 catalyst. This high catalytic performance could be attributed to the unique two-dimensional sheet-like structure of Ru(bpy)3-rGO, which efficiently diminished diffusion resistance of the reactants. Meanwhile, the nonconjugated PhSO3Na-linkage between Ru(II) complex and the support and the very low electrical conductivity of the catalyst inhibited energy/electron transfer from Ru(II) complex to rGO support, resulting in the decreased support-induced quenching effect. Furthermore, it could be easily recycled at least five times without significant loss of catalytic reactivity.

  14. Characterization and evaluation of graphene oxide scaffold for periodontal wound healing of class II furcation defects in dog.

    Science.gov (United States)

    Kawamoto, Kohei; Miyaji, Hirofumi; Nishida, Erika; Miyata, Saori; Kato, Akihito; Tateyama, Akito; Furihata, Tomokazu; Shitomi, Kanako; Iwanaga, Toshihiko; Sugaya, Tsutomu

    2018-01-01

    The 3-dimensional scaffold plays a key role in volume and quality of repair tissue in periodontal tissue engineering therapy. We fabricated a novel 3D collagen scaffold containing carbon-based 2-dimensional layered material, named graphene oxide (GO). The aim of this study was to characterize and assess GO scaffold for periodontal tissue healing of class II furcation defects in dog. GO scaffolds were prepared by coating the surface of a 3D collagen sponge scaffold with GO dispersion. Scaffolds were characterized using cytotoxicity and tissue reactivity tests. In addition, GO scaffold was implanted into dog class II furcation defects and periodontal healing was investigated at 4 weeks postsurgery. GO scaffold exhibited low cytotoxicity and enhanced cellular ingrowth behavior and rat bone forming ability. In addition, GO scaffold stimulated healing of dog class II furcation defects. Periodontal attachment formation, including alveolar bone, periodontal ligament-like tissue, and cementum-like tissue, was significantly increased by GO scaffold implantation, compared with untreated scaffold. The results suggest that GO scaffold is biocompatible and possesses excellent bone and periodontal tissue formation ability. Therefore, GO scaffold would be beneficial for periodontal tissue engineering therapy.

  15. Photoenhanced Oxidative DNA Cleavage with Non-Heme Iron(II) Complexes

    NARCIS (Netherlands)

    Li, Qian; Browne, Wesley R.; Roelfes, Gerard

    2010-01-01

    The DNA cleavage activity of iron(II) complexes of a series of monotopic pentadentate N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine (N4Py)-derived ligands (1-5) was investigated under laser irradiation at 473, 400.8, and 355 nm in the absence of a reducing agent and compared to that under

  16. Alternative products to carbazoles in the oxidation of diphenylamines with palladium (II) acetate

    OpenAIRE

    Raposo, M. Manuela M.; Campos, Ana M. F. Oliveira; Shannon, Patrick V. R.

    1997-01-01

    Although simple diphenylamines are conveniently oxidised with Palladium (II) acetate to give carbazoles, for more complex examples, carbazoles are minor products amongst many. CRUP (Portugal). British Council - Treaty of Windsor Programme. Junta Nacional de Investigação Científica e Tecnológica.

  17. ARSENATE AND ARSENITE SORPTION AND ARSENITE OXIDATION BY IRON (II, III) HYDROXYCARBONATE GREEN RUST

    Science.gov (United States)

    Iron (II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron that is being used in permeable reactive barriers to remediate groundwater arsenic contamination. To optimize the design of iron barriers, it is important to evaluate the influence of geoch...

  18. Copper(II)-catalyzed electrophilic amination of quinoline N-oxides with O-benzoyl hydroxylamines.

    Science.gov (United States)

    Li, Gang; Jia, Chunqi; Sun, Kai; Lv, Yunhe; Zhao, Feng; Zhou, Kexiao; Wu, Hankui

    2015-03-21

    Copper acetate-catalyzed C-H bond functionalization amination of quinoline N-oxides was achieved using O-benzoyl hydroxylamine as an electrophilic amination reagent, thereby affording the desired products in moderate to excellent yields. Electrophilic amination can also be performed in good yield on a gram scale.

  19. Physiochemical Characterization of Iodine (V Oxide Part II: Morphology and Crystal Structure of Particulate Films

    Directory of Open Access Journals (Sweden)

    Brian K. Little

    2015-11-01

    Full Text Available In this study, the production of particulate films of iodine (V oxides is investigated. The influence that sonication and solvation of suspended particles in various alcohol/ketone/ester solvents have on the physical structure of spin or drop cast films is examined in detail with electron microscopy, powder x-ray diffraction, and UV-visible absorption spectroscopy. Results indicate that sonicating iodine oxides in alcohol mixtures containing trace amounts of water decreases deposited particle sizes and produces a more uniform film morphology. UV-visible spectra of the pre-cast suspensions reveal that for some solvents, the iodine oxide oxidizes the solvent, producing I2 and lowering the pH of the suspension. Characterizing the crystals within the cast films reveal their composition to be primarily HI3O8, their orientations to exhibit a preferential orientation, and their growth to be primarily along the ac-plane of the crystal, enhanced at higher spin rates. Spin-coating at lower spin rates produces laminate-like particulate films versus higher density, one-piece films of stacked particles produced by drop casting. The particle morphology in these films consists of a combination of rods, plates, cubes, and rhombohedra structure.

  20. Sorption of Sr(II) onto nanocomposites of graphene oxide-polymeric matrix

    Czech Academy of Sciences Publication Activity Database

    Bubeníková, M.; Ecorchard, Petra; Szatmáry, L.; Mrózek, Ondřej; Salačová, P.; Tolasz, Jakub

    2018-01-01

    Roč. 315, č. 2 (2018), s. 263-272 ISSN 0236-5731 R&D Projects: GA TA ČR(CZ) TA04020222 Institutional support: RVO:61388980 Keywords : Graphene oxide * Nanocomposite * PA66 * Polystyrene * Radiostrontium removal Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 1.282, year: 2016

  1. EPA:DHA 6:1 prevents angiotensin II-induced hypertension and endothelial dysfunction in rats: role of NADPH oxidase- and COX-derived oxidative stress.

    Science.gov (United States)

    Niazi, Zahid Rasul; Silva, Grazielle C; Ribeiro, Thais Porto; León-González, Antonio J; Kassem, Mohamad; Mirajkar, Abdur; Alvi, Azhar; Abbas, Malak; Zgheel, Faraj; Schini-Kerth, Valérie B; Auger, Cyril

    2017-12-01

    Eicosapentaenoic acid:docosahexaenoic acid (EPA:DHA) 6:1, an omega-3 polyunsaturated fatty acid formulation, has been shown to induce a sustained formation of endothelial nitric oxide (NO) synthase-derived NO, a major vasoprotective factor. This study examined whether chronic intake of EPA:DHA 6:1 prevents hypertension and endothelial dysfunction induced by angiotensin II (Ang II) in rats. Male Wister rats received orally corn oil or EPA:DHA 6:1 (500 mg kg -1 per day) before chronic infusion of Ang II (0.4 mg kg -1 per day). Systolic blood pressure was determined by tail cuff sphingomanometry, vascular reactivity using a myograph, oxidative stress using dihydroethidium and protein expression by immunofluorescence and western blot analysis. Ang II-induced hypertension was associated with reduced acetylcholine-induced relaxations of secondary branch mesenteric artery rings affecting the endothelium-dependent hyperpolarization (EDH)- and the NO-mediated relaxations, both of which were improved by the NADPH oxidase inhibitor VAS-2870. The Ang II treatment induced also endothelium-dependent contractile responses (EDCFs), which were abolished by the cyclooxygenase (COX) inhibitor indomethacin. An increased level of vascular oxidative stress and expression of NADPH oxidase subunits (p47 phox and p22 phox ), COX-1 and COX-2, endothelial NO synthase and Ang II type 1 receptors were observed in the Ang II group, whereas SK Ca and connexin 37 were downregulated. Intake of EPA:DHA 6:1 prevented the Ang II-induced hypertension and endothelial dysfunction by improving both the NO- and EDH-mediated relaxations, and by reducing EDCFs and the expression of target proteins. The present findings indicate that chronic intake of EPA:DHA 6:1 prevented the Ang II-induced hypertension and endothelial dysfunction in rats, most likely by preventing NADPH oxidase- and COX-derived oxidative stress.

  2. Natriuretic peptide receptor-C activation attenuates angiotensin II-induced enhanced oxidative stress and hyperproliferation of aortic vascular smooth muscle cells.

    Science.gov (United States)

    Madiraju, Padma; Hossain, Ekhtear; Anand-Srivastava, Madhu B

    2018-02-07

    We showed previously that natriuretic peptide receptor-C (NPR-C) agonist, C-ANP 4-23 , attenuated the enhanced expression of Giα proteins in vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) through the inhibition of enhanced oxidative stress. Since the enhanced levels of endogenous angiotensin II (Ang II) contribute to the overexpression of Giα proteins and augmented oxidative stress in VSMC from SHR, the present study was undertaken to investigate if C-ANP 4-23 could also attenuate angiotensin II (Ang II)-induced oxidative stress and associated signaling. Ang II treatment of aortic VSMC augmented the levels of superoxide anion (O 2 - ), NADPH oxidase activity, and the expression of NADPH oxidase subunits and C-ANP 4-23 treatment attenuated all these to control levels. In addition, Ang II-induced enhanced levels of thiobarbituric acid-reactive substances (TBARS) and protein carbonyl content were also attenuated toward control levels by C-ANP 4-23 treatment. On the other hand, Ang II inhibited the levels of nitric oxide (NO) and augmented the levels of peroxynitrite (OONO - ) in VSMC which were restored to control levels by C-ANP 4-23 treatment. Furthermore, C-ANP 4-23 treatment attenuated Ang II-induced enhanced expression of Giα proteins, phosphorylation of p38, JNK, and ERK 1,2 as well as hyperproliferation of VSMC as determined by DNA synthesis, and metabolic activity. These results indicate that C-ANP 4-23 , via the activation of NPR-C, attenuates Ang II-induced enhanced nitroxidative stress, overexpression of Giα proteins, increased activation of the p38/JNK/ERK 1,2 signaling pathways, and hyperproliferation of VSMC. It may be suggested that C-ANP 4-23 could be used as a therapeutic agent in the treatment of vascular remodeling associated with hypertension and atherosclerosis.

  3. Inelastic scattering from liquid 4He in aerogel glass

    International Nuclear Information System (INIS)

    Snow, W.M.; Sokol, P.E.

    1988-01-01

    The physics of liquid and solid 4 He in restricted geometries has motivated a number of interesting experiments. Recent experiments include detailed measurements of the phase diagram for bulk liquid in vycor, showing a suppression of the superfluid transition and elevation of the melting pressure, and measurements of the superfluid fraction in vycor, aerogel, and zerogel glasses near the lambda point, in which critical exponents differ from the pure 4 He values have been observed. Many striking features in several of the experiments on helium in restricted geometries are poorly understood. We have performed inelastic neutron scattering measurements of liquid helium in aerogel glass above and below the superfluid transition for two samples of different porosities. The kinetic energy (KE) of the confined liquid is the same as that of the bulk liquid in the normal phase, but is clearly higher than the bulk values in the superfluid phase. The observed scattering in the superfluid phase is more peaked than in the normal phase: consistent with the presence of a Bose condensate. An estimate of the condensate fraction using a modification of a method due to Sears yields values consistent with those estimated for the bulk liquid. 7 refs., 2 figs., 1 tab

  4. The LHCb RICH silica aerogel performance with LHC data

    CERN Multimedia

    Perego, D L

    2010-01-01

    In the LHCb detector at the Large Hadron Collider, powerful charged particle identification is performed by Ring Imaging Cherenkov (RICH) technology. In order to cover the full geometric acceptance and the wide momentum range (1-100 GeV/c), two detectors with three Cherenkov radiators have been designed and installed. In the medium (10-40 GeV/c) and high (30-100 GeV/c) momentum range, gas radiators are used (C4F10 and CF4 respectively). In the low momentum range (1 to a few GeV/c) pion/kaon/proton separation will be done with photons produced in solid silica aerogel. A set of 16 tiles, with the large transverse dimensions ever (20x20 cm$^2$) and nominal refractive index 1.03 have been produced. The tiles have excellent optical properties and homogeneity of refractive index within the tile of ~1%. The first data collected at LHC are used to understand the behaviour of the RICH: preliminary results will be presented and discussed on the performance of silica aerogel and of the gas radiators C4F10 and CF4.

  5. Mechanical Properties and Brittle Behavior of Silica Aerogels

    Directory of Open Access Journals (Sweden)

    Thierry Woignier

    2015-12-01

    Full Text Available Sets of silica gels: aerogels, xerogels and sintered aerogels, have been studied in the objective to understand the mechanical behavior of these highly porous solids. The mechanical behaviour of gels is described in terms of elastic and brittle materials, like glasses or ceramics. The magnitude of the elastic and rupture modulus is several orders of magnitude lower compared to dense glass. The mechanical behaviours (elastic and brittle are related to the same kinds of gel characteristics: pore volume, silanol content and pore size. Elastic modulus depends strongly on the volume fraction of pores and on the condensation reaction between silanols. Concerning the brittleness features: rupture modulus and toughness, it is shown that pores size plays an important role. Pores can be considered as flaws in the terms of fracture mechanics and the flaw size is related to the pore size. Weibull’s theory is used to show the statistical nature of flaw. Moreover, stress corrosion behaviour is studied as a function of environmental conditions (water and alcoholic atmosphere and temperature.

  6. Iron and Arsenic Speciation During As(III) Oxidation by Manganese Oxides in the Presence of Fe(II): Molecular-Level Characterization Using XAFS, Mössbauer, and TEM Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yun [Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, Delaware 19716, United States; Kukkadapu, Ravi K. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Livi, Kenneth J. T. [The High-Resolution Analytical Electron Microbeam Facility, Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218, United States; Xu, Wenqian [Department of Chemistry, Brookhaven National Lab, Upton, New York 11796, United States; Li, Wei [Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, Delaware 19716, United States; Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, People’s Republic of China; Sparks, Donald L. [Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, Delaware 19716, United States

    2018-01-17

    The redox state and speciation of metalloid arsenic (As) determine its toxicity and mobility. Knowledge of biogeochemical processes influencing the As redox state is therefore important to understand and predict its environmental behavior. Many previous studies examined As(III) oxidation by various Mn-oxides, but little is known the environmental influences (e.g. co-existing ions) on such process. In this study, we investigated the mechanisms of As(III) oxidation by a poorly crystalline hexagonal birnessite (δ-MnO2) in the presence of Fe(II) using X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS). As K-edge X-ray absorption near edge spectroscopy (XANES) analysis revealed that, at low Fe(II) concentration (100 μM), As(V) was the predominant As species on the solid phase, while at higher Fe(II) concentration (200-1000 μM), both As(III) and As(V) were sorbed on the solid phase. As K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) analysis showed an increasing As-Mn/Fe distance over time, indicating As prefers to bind with the newly formed Fe(III)-(hydr)oxides. As adsorbed on Fe(III)-(hydr)oxides as a bidentate binuclear corner-sharing complex. Both Mössbauer and TEM-EDS investigations demonstrated that the oxidized Fe(III) products formed during Fe(II) oxidation by δ-MnO2 were predominantly ferrihydrite, goethite, and ferric arsenate like compounds. However, Fe EXAFS analysis also suggested the formation of a small amount of lepidocrocite. The Mn K-edge XANES data indicated that As(III) and Fe(II) oxidation occurs as a two electron transfer with δ-MnO2 and the observed Mn(III) is due to conproportionation of surface sorbed Mn(II) with Mn(IV) in δ-MnO2 structure. This study reveals that the mechanisms of As(III) oxidation by δ-MnO2 in the presence of Fe(II) are very complex, involving many simultaneous reactions, and the formation of

  7. Catalytic water oxidation by ruthenium(II) quaterpyridine (qpy) complexes: evidence for ruthenium(III) qpy-N,N'''-dioxide as the real catalysts.

    Science.gov (United States)

    Liu, Yingying; Ng, Siu-Mui; Yiu, Shek-Man; Lam, William W Y; Wei, Xi-Guang; Lau, Kai-Chung; Lau, Tai-Chu

    2014-12-22

    Polypyridyl and related ligands have been widely used for the development of water oxidation catalysts. Supposedly these ligands are oxidation-resistant and can stabilize high-oxidation-state intermediates. In this work a series of ruthenium(II) complexes [Ru(qpy)(L)2 ](2+) (qpy=2,2':6',2'':6'',2'''-quaterpyridine; L=substituted pyridine) have been synthesized and found to catalyze Ce(IV) -driven water oxidation, with turnover numbers of up to 2100. However, these ruthenium complexes are found to function only as precatalysts; first, they have to be oxidized to the qpy-N,N'''-dioxide (ONNO) complexes [Ru(ONNO)(L)2 ](3+) which are the real catalysts for water oxidation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Discussion of "Investigation of Oxide Bifilms in Investment Cast Superalloy IN100 Parts I and II"*

    Science.gov (United States)

    Campbell, John

    2017-10-01

    Fuchs and Kaplan carried out experiments in an attempt to ascertain whether oxide bifilms were present in a vacuum-cast Ni-base superalloy but concluded negatively. Although this author challenged their interpretation of their findings, both parties had overlooked the presence in the alloy of boron which is now known to inhibit bifilm formation. However, even though boron can help significantly, improved filling system designs remain important if other damaging entrainment defects are to be avoided.

  9. Reduction-oxidation Enabled Glass-ceramics to Stainless Steel Bonding Part II interfacial bonding analysis

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Steve Xunhu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Among glass-ceramic compositions modified with a variety of oxidants (AgO, FeO, NiO, PbO, SnO, CuO, CoO, MoO3 and WO3) only CuO and CoO doped glass-ceramics showed existence of bonding oxides through reduction-oxidation (redox) at the GC-SS interface. The CuO-modified glass-ceramics demonstrate the formation of a continuous layer of strong bonding Cr2O3 at the interface in low partial oxygen (PO2) atmosphere. However, in a local reducing atmosphere, the CuO is preferentially reduced at the surface of glass-ceramic rather than the GC-SS interface for redox. The CoO-modified glass-ceramics demonstrate improved GC-SS bonding. But the low mobility of Co++ ions in the GC limited the amount of CoO that can diffuse to and participate in redox at the interface.

  10. Flexible transparent aerogels as window retrofitting films and optical elements with tunable birefringence

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qingkun; Frazier, Allister W.; Zhao, Xinpeng; De La Cruz, Joshua A.; Hess, Andrew J.; Yang, Ronggui; Smalyukh, Ivan I.

    2018-06-01

    Experimental realization of optically transparent, mechanically robust and flexible aerogels has been a longstanding challenge, which limits their practical applications in energy-saving devices, such as thermally insulating films for enhancing energy efficiency of windows. The poor transparency precluded even hypothetical consideration of the possibility of birefringent aerogels. We develop birefringent and optically isotropic aerogels that combine properties of thermal super-insulation, mechanical robustness and flexibility, and transparency to visible-spectrum light. This unusual combination of physical properties is achieved by combining liquid crystalline self-organization of cellulose nanofibers with polysiloxane cross-linking and control of the nanoscale porosity to form hybrid organic-inorganic mesostructured aerogels. Potential applications of these inexpensive materials range from single pane window retrofitting to smart fabrics.

  11. Preparation and Characterization of Highly Spherical Silica-titania