708 research outputs found
Immobilized polyoxometalates onto mesoporous organically-modified silica aerogels as selective heterogeneous catalysts of anthracene oxidation
No full textImmobilized molybdovanadophosphoric acids onto organically surface-modified silica aerogels were successfully prepared and investigated in heterogeneous catalysis of anthracene oxidation. The catalysts were obtained by supporting mono- and di-vanadium substituted molybdophosphoric acids on hybrid silica materials synthesized via the sol-gel process followed by surface amino-functionalization. The FTIR, DR UV-vis, and AA spectroscopy confirmed the loading and distribution of the polyoxometalate molecules on the surface of the aerogels. The nitrogen adsorption-desorption technique revealed a systematic decrease in the specific surface area and pore volume after the immobilization of the polyoxometalates. The application of the supported molecules as catalysts for anthracene oxidation showed 100percent selectivity for 9,10- anthraquinone as opposed to the reactions conducted under homogeneous conditions. Moreover, at certain conditions, the catalytic activity of the supported polyoxometalates was greater than their corresponding free polyoxometalates with a clear effect of the surface chemical groups of the supporting silica aerogels. Additionally, the oxidant and solvent nature showed a crucial effect on the catalytic activity and selectivity of the immobilized polyoxometales. The heterogeneous catalysts were regenerated and reused over consecutive catalytic cycles reflecting a potential economic interest in these materials besides their high efficiency in heterogeneous catalysis. © Springer Science+Business Media, LLC 2011.Al-Kadamany G, 2010, CHEM-EUR J, V16, P11797, DOI 10.1002-chem.201000786; Al-Oweini R, 2009, J MOL STRUCT, V919, P140, DOI 10.1016-j.molstruc.2008.08.025; Al-Oweini R, 2010, APPL SURF SCI, V257, P276, DOI 10.1016-j.apsusc.2010.06.086; Antonova NS, 2010, J AM CHEM SOC, V132, P7488, DOI 10.1021-ja1023157; BARRETT EP, 1951, J AM CHEM SOC, V73, P373, DOI 10.1021-ja01145a126; Bassil BS, 2011, ANGEW CHEM INT EDIT, V50, P5961, DOI 10.1002-anie.201007617; Berzelius J.J., 1826, POGGENDORFS ANN PHYS, V6, P369; Bi LH, 2009, INORG CHEM, V48, P10068, DOI 10.1021-ic9009306; Bordoloi A, 2007, J CATAL, V247, P166, DOI 10.1016-j.jcat.2007.01.020; Bordoloi A, 2008, J CATAL, V259, P232, DOI 10.1016-j.jcat.2008.08.010; Brinker C. J., 1990, SOL GEL SCI PHYS CHE; Brunauer S, 1938, J AM CHEM SOC, V60, P309, DOI 10.1021-ja01269a023; Cairns D, 2002, BIOORGAN MED CHEM, V10, P803, DOI 10.1016-S0968-0896(01)00337-6; Chen QL, 2008, CHEM ENG PROCESS, V47, P787, DOI 10.1016-j.cep.2006.12.012; Donoeva BG, 2010, EUR J INORG CHEM, V33, P5312; Durand N, 2011, LANGMUIR, V27, P4057, DOI 10.1021-la1048826; Ge P, 1997, TETRAHEDRON, V53, P17469, DOI 10.1016-S0040-4020(97)10195-8; Giinzler H., 2002, IR SPECTROSCOPY INTR; Guo YH, 2000, CHEM MATER, V12, P3501, DOI 10.1021-cm000074+; Hu CW, 1996, CHEM COMMUN, P121, DOI 10.1039-cc9960000121; Huang HS, 2003, J MED CHEM, V46, P3300, DOI 10.1021-jm0204921; Huesing N, 1995, J NONCRYST SOLIDS, V186, P37; ISHII Y, 1988, J ORG CHEM, V53, P3587, DOI 10.1021-jo00250a032; Izumi Y, 1995, MICROPOROUS MATER, V5, P255, DOI 10.1016-0927-6513(95)00059-3; Jahier C, 2009, EUR J INORG CHEM, P5148, DOI 10.1002-ejic.200900682; Joseph T, 2005, J MOL CATAL A-CHEM, V229, P241, DOI 10.1016-j.molcata.2004.12.008; Katsoulis DE, 1998, CHEM REV, V98, P359, DOI 10.1021-cr960398a; Keggin JF, 1933, NATURE, V131, P908, DOI 10.1038-131908b0; Kumar D, 2007, MICROPOR MESOPOR MAT, V98, P309, DOI 10.1016-j.micromeso.2006.09.023; Long DL, 2007, CHEM SOC REV, V36, P105, DOI 10.1039-b502666k; Maksimchuk NV, 2007, J CATAL, V246, P241, DOI 10.1016-j.jcat.2006.11.026; Manisankar P, 2005, J MOL CATAL A-CHEM, V232, P45, DOI 10.1016-j.molcata.2005.01.001; Mizuno N, 1998, CHEM REV, V98, P199, DOI 10.1021-cr960401q; Pierre AC, 2002, CHEM REV, V102, P4243, DOI 10.1021-cr0101306; Pozniczek J, 2006, APPL CATAL A-GEN, V298, P217, DOI 10.1016-j.apcata.2005.10.013; Santacesaria E, 1999, CHEM ENG SCI, V54, P2799, DOI 10.1016-S0009-2509(98)00377-7; Selvaraj M, 2007, MICROPOR MESOPOR MAT, V101, P240, DOI 10.1016-j.micromeso.2006.12.020; Song H, 2006, J AM CHEM SOC, V128, P3027, DOI 10.1021-ja057383r; Strukul G, 1992, CATALYTIC OXIDATIONS, P1; TSIGDINO.GA, 1968, INORG CHEM, V7, P437, DOI 10.1021-ic50061a00933
Scrutinizing the importance of surface chemistry versus surface roughness for aluminium / sol-gel film adhesion
No full textThe sol-gel synthesis process is a versatile method used to produce a wide diversity of materials and is being increasingly used as a surface modification method to alter porosity, wettability, catalytic activity, biocompatibility and corrosion performance of underlying substrates. Silane sol–gel films deposited on aluminium and aluminium alloys have been widely studied as chemical conversion coatings and as coupling agent between the substrate and organic layers. This study set out to investigate the effect of the surface chemical treatment prior to sol-gel application on the interfacial adhesion properties of a hybrid sol-gel film. Different surface pre-treatments, including two abrasive treatments and three chemical surface pre-treatments were used and their effect on surface chemistry and surface roughness was assessed. Surfaces were characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, roughness measurements and static contact angles. Cerium nitrate loaded hybrid sol-gel films were deposited and adhesion on commercially pure aluminium was evaluated using pull-off testing. Statistical analysis revealed that, although highest adhesion values were obtained on rougher surfaces, the strongest correlation exists between the surface hydroxyl fraction and adhesion strength.Team Arjan MolTeam Yaiza Gonzalez Garci
Cobalt ferrite aerogels by epoxide sol-gel addition: Efficient catalysts for the hydrolysis of 4-nitrophenyl phosphate
No full textPorous cobalt ferrite aerogel catalysts were obtained by 1,2-epoxide sol-gel process and investigated in the hydrolysis of 4-nitrophenyl phosphate. These materials were synthesized by reacting cobalt and iron salts with propylene oxide in methanol, dried by supercritical carbon dioxide, and calcined between 200 and 800 °C. The catalysts were characterized using Fourier Transform Infrared (FTIR) spectroscopy, nitrogen adsorption-desorption technique, and powder X-ray diffraction (XRD). The as-prepared aerogel surface exhibits M-OH groups that disappear after annealing, which enhances the spinel structure. This was coupled with a better crystallinity revealed by XRD peaks sharpness. The crystallite sizes were found to be between 6.3 and 28.1 nm. In addition, the catalysts revealed high porosities that decrease as the annealing temperature increases. The catalysis showed that the catalytic activity significantly rely on the synthesis procedure and mainly the calcination temperature. Samples calcined at 600 °C and above did not show any catalytic activity, however, the highest catalytic efficiency was for those calcined at 200 °C with 100percent selectivity for the 4-nitrophenol. The correlation of the characterization techniques and the catalysis tests revealed that the catalytic properties of these sol-gel materials are due to the existence of residual surface OH groups. © 2009 Elsevier B.V. All rights reserved.Banerjee M, 2007, J MATER SCI, V 42, P1833, DOI 10.1007-s10853-006-0821-1; BARRETT EP, 1951, J AM CHEM SOC, V73, P373, DOI 10.1021-ja01145a126; Brinker CJ, 1990, PHYS CHEM SOL GEL PR; Brunauer S, 1938, J AM CHEM SOC, V60, P309, DOI 10.1021-ja01269a023; Calero-DdelC VL, 2007, J MAGN MAGN MATER, V314, P60, DOI 10.1016-j.jmmm.2006.12.030; Cote LJ, 2003, FLUID PHASE EQUILIBR, V210, P307, DOI 10.1016-S0378-3812(03)00168-7; El-Shobaky HG, 2007, MAT SCI ENG B-SOLID, V143, P21, DOI 10.1016-j.mseb.2007.07.072; Gao YP, 2007, CHEM MATER, V19, P6007, DOI 10.1021-cm0718419; Gash AE, 2001, J NON-CRYST SOLIDS, V285, P22, DOI 10.1016-S0022-3093(01)00427-6; Giinzler H., 2002, IR SPECTROSCOPY INTR; Gu ZJ, 2008, J PHYS CHEM C, V112, P18459, DOI 10.1021-jp806682q; Gul IH, 2008, J ALLOY COMPD, V465, P227, DOI 10.1016-j.jallcom.2007.11.006; HAMDEH HH, 1994, J APPL PHYS, V76, P1135, DOI 10.1063-1.357835; Hua ZH, 2007, J ALLOY COMPD, V427, P199, DOI 10.1016-j.jallcom.2006.02.048; Huesing N, 1995, J NONCRYST SOLIDS, V186, P37; Lavela P, 2007, J POWER SOURCES, V172, P379, DOI 10.1016-j.jpowsour.2007.07.055; Lee H, 2008, CATAL LETT, V124, P364, DOI 10.1007-s10562-008-9476-7; Liu T, 2008, MATER LETT, V62, P4056, DOI 10.1016-j.matlet.2008.04.081; LIVAGE J, 1988, PROG SOLID STATE CH, V18, P259, DOI 10.1016-0079-6786(88)90005-2; Lowell S., 2004, CHARACTERIZATION POR; Maaz K, 2007, J MAGN MAGN MATER, V308, P289, DOI 10.1016-j.jmmm.2006.06.003; Manova E, 2004, CHEM MATER, V16, P5689, DOI 10.1021-cm049189u; Mathew T, 2004, APPL CATAL A-GEN, V273, P35, DOI 10.1016-j.apcata.2004.06.011; Meron T, 2005, J MAGN MAGN MATER, V292, P11, DOI 10.1016-j.jmmm.2004.10.084; Patterson AL, 1939, PHYS REV, V56, P978, DOI 10.1103-PhysRev.56.978; Pierre AC, 2002, CHEM REV, V102, P4243, DOI 10.1021-cr0101306; Ramankutty CG, 2002, J MOL CATAL A-CHEM, V187, P105, DOI 10.1016-S1381-1169(02)00121-8; Sisk CN, 2008, J MATER CHEM, V18, P2607, DOI 10.1039-b802174k; Sun SH, 2004, J AM CHEM SOC, V126, P273, DOI 10.1021-ja0380852; Thang PD, 2007, J MAGN MAGN MATER, V310, P2621, DOI 10.1016-j.jmmm.2006.11.048; Toksha BG, 2008, SOLID STATE COMMUN, V147, P479, DOI 10.1016-j.ssc.2008.06.040; Toledo-Antonio JA, 2002, APPL CATAL A-GEN, V234, P137, DOI 10.1016-S0926-860X(02)00212-0; Vijayaraj M, 2006, J CATAL, V241, P83, DOI 10.1016-j.jcat.2006.04.010; WALDRON RD, 1955, PHYS REV, V99, P1727, DOI 10.1103-PhysRev.99.1727; Wang CC, 2006, J MAGN MAGN MATER, V304, pE451, DOI 10.1016-j.jmmm.2006.02.064; Wang X, 2005, NATURE, V437, P121, DOI 10.1038-nature03968; Xu R, 2003, CHEM MATER, V15, P2040, DOI 10.1021-cm021732o; Yan CH, 1999, SOLID STATE COMMUN, V111, P287, DOI 10.1016-S0038-1098(99)00119-2; Zhao LJ, 2008, J SOLID STATE CHEM, V181, P245, DOI 10.1016-j.jssc.2007.10.0348101
Design of a GaInP/GaAs tandem solar cell for maximum daily, monthly, and yearly energy output
No full textSolar concentrator cells are typically designed for maximum efficiency under the AM1.5d standard spectrum. While this methodology does allow for a direct comparison of cells produced by various laboratories, it does not guarantee maximum daily, monthly, or yearly energy production, as the relative distribution of spectral energy changes throughout the day and year. It has been suggested that achieving this goal requires designing under a nonstandard spectrum. In this work, a GaInP/GaAs tandem solar cell is designed for maximum energy production by optimizing for a set of geographically-dependent solar spectra using detailed numerical models. The optimization procedure focuses on finding the best combination of GaInP bandgap and GaInP and GaAs sub-cell absorber layer thicknesses. It is shown that optimizing for the AM1.5d standard spectrum produces nearly maximum yearly energy. This result simplifies the design of a dual-junction device considerably, is independent of the optical concentration up to at least 500 suns, and holds for a wide range of geographic locations. The simulation results are compared to those obtained using a more traditional, ideal-diode model. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI:10.1117/1.3633244
NOBODY LIED / (When they said that I cried over you.) / Words by / KARYL NORMAN / & HYATT BERRY. / Music by / EDWIN J. WEBER:
No full textBox no. 1This item has been bound together with items gma-doc-00524 and gma-doc-00034.Edwin J. Weber: Nobody Lied; music printItem type: book | Content type: music and text | Writing material: pencil | Counting of pages: page numbersvocal-instrumental score | staff notation; tonic sol-fa | voice; piano"I have wander'd my whole life through [...]
Surface engineering of aerospace aluminium alloys: Understanding alloying effects on chemical pre-treatment and sol-gel coating adhesion
No full textThe sol–gel process is a chemical surface preparation method based on hydrolysis and polycondensation reactions for enhanced adhesion for metallic substrates in adhesive bonding and coating applications. This paper describes an investigation into the effect of the microstructural complexity of two commonly used aerospace aluminium alloys (AAs) 2024-T3 and 7075-T6, on the response to different surface pre-treatments before deposition of the sol-gel coating and subsequent adhesive bonding. Different surface pre-treatments, including two abrasive treatments and three chemical surface pre-treatments were used, and their effect on surface chemistry, wettability and roughness was assessed. Surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry and static contact angles. A hybrid silane sol-gel film was deposited on the differently pre-treated aluminium alloys, an epoxy adhesive was applied and the adhesion properties were evaluated using pull-off testing. The role of the altered physicochemical properties of the pre-treated surfaces was related to the adhesion strength of the sol–gel reinforced epoxy/aluminium interfaces. The microstructural complexity of the aerospace alloys caused non-uniform responses to the pre-treatments, proving the importance of compatibility between material and treatment conditions. Statistical analysis revealed that, despite that overall higher adhesion values were obtained on rougher surfaces, only a strong correlation exists between the surface hydroxyl fraction and adhesion strength. The relation of roughness and water contact angle to interfacial adhesion was found to be non-significant. The findings of this study underscore the critical role of surface pre-treatments and their impact on adhesion strength in aerospace aluminium alloys, providing valuable insights for the effective utilization of sol-gel coatings in adhesive bonding and coating processes.Team Yaiza Gonzalez GarciaTeam Peyman TaheriTeam Shoshan AbrahamiTeam Arjan Mo
The Dwarfs / Action Song for School Concerts / WORDS BY / A. J. FOXWELL / MUSIC BY / C. HUTCHINS LEWIS.
No full textBox no. 4Charles Hutchins Lewis: The Dwarfs, Action Song for School Concerts; music printItem type: book | Content type: music | Counting of pages: page numbersvocal-instrument score | staff notation; tonic sol-fa notation | voice, piano"O dear! how is it people think So very much of tall men? [...]
Piezoelectricity Of Zno Films Prepared By Sol-Gel Method
No full textZnO piezoelectric thin films were prepared on crystal substrate Si(111) by sol-gel technology, then characterized by scanning electron microscopy, X-ray diffraction and atomic force microscopy (AFM). The ZnO films characterized by X-ray diffraction are highly oriented in (002) direction with the growing of the film thickness. The morphologies, roughness and grain size of ZnO film investigated by AFM show that roughness and grain size of ZnO piezoelectric films decrease with the increase of the film thickness. The roughness dimension is 2.188-0.914 nm. The piezoelectric coefficient d(33) was investigated with a piezo-response force microscope (PFM). The results show that the piezoelectric coefficient increases with the increase of thickness and (002) orientation. When the force reference is close to surface roughness of the films, the piezoelectric coefficient measured is inaccurate and fluctuates in a large range, but when the force reference is big, the piezoelectric coefficient d(33) changes little and ultimately keeps constant at a low frequency
Towards H2 selective porous inorganic membranes: Pore size control through combined Sol-Gel and Atomic Layer Deposition Processes
No full textCarbon capture and storage (CCS) can significantly contribute to the reduction of the emission of the greenhouse gas CO2. Capture by means of CO2 sorption or membrane-based separation processes is a promising way for achieving decarbonization of fuel or flue gas cleaning. In the field of separation and also purification of hydrogen, membrane separation technology has been and still is a focal point for Research and Development (R&D) due to its promising energy-efficiency, inherent selectivity and continuous operation. Research is being devoted to the development of membranes for H2 separation from CO and CO2 containing gas mixtures with high permeance and selectivity for conversion to electricity via fuel cells or directly in gas turbines. Currently, most membranes are being developed to separate H2 from the underlying reaction mixtures obtained via coal gasification, steam-methane reforming, and water gas-shift processes. The key advantage of membrane separation, but also sorbent-based separation, is the possibility to go beyond the thermodynamic conversion limits set by the equilibrium constant of these H2 production reactions. The in-situ separation of H2 from the gas mixture through membranes shifts the equilibrium toward higher production of H2 by preventing the back reaction. At the same time a stream of CO2 is produced, pure enough for storage in geological reservoirs (empty oil and gas fields or deep saline aquifers) or for use in enhanced oil or gas recovery processes. Inorganic microporous membranes are considered promising for H2 separation in high-temperature H2 production processes because of their high thermal and chemical stability. The major objective of the thesis is dedicated to fabricate and study a microporous non-silica based membrane system, consisting of an ?-alumina macroporous support, a mesoporous intermediate layer, and a microporous ?-Al2O3, or TiO2 top layer, for H2 separation from a gas mixture with CO and CO2. We have studied the possibility to incorporate Al2O3, TiO2, and ZrO2 into the envisioned structure using the synthesis concept of a combination of sol-gel and Atomic Layer Deposition (ALD) processes. The foremost goal of the ALD related membrane research was to provide enhanced H2 selectivity of the synthesized membranes. Tests on the H2/CO2 separation were carried out on these synthesized membranes. The H2 permeance and H2/CO2 selectivity of these membranes are ~1-2x10?7 mol.m?2.s?1.Pa?1 and ~ 5.8-10.9 at 175 °C and 105 Pa pressure difference, respectively. It was shown that ALD can elegantly be coupled with the sol-gel synthesis to fabricate microporous membranes on a large scale.Chemical EngineeringApplied Science
A sol-gel method for growing superconducting MgB2 films
No full textIn this paper we report a new sol-gel method for the fabrication of MgB2 films. Polycrystalline MgB2 films were prepared by spin-coating a precursor solution of Mg(BH4)(2) diethyl ether on (001)Al2O3 substrates followed with annealing in Mg vapor. In comparison with the MgB2 films grown by other techniques, our films show medium qualities including a superconducting transition temperature of T-C similar to 37 K, a critical current density of J(C)(5 K, 0 T) similar to 5 x 10(6) A cm(-2), and a critical field of H-C2(0) similar to 19 T. Such a sol-gel technique shows potential in the commercial fabrication of practically used MgB2 films as well as MgB2 wires and tapes.Physics, AppliedPhysics, Condensed MatterSCI(E)EI3ARTICLE1null2
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